CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Canadian patent application number CA 3,056,117, filed on September 20, 2019, the contents of which are incorporated herein by reference in their entirety.

FIELD OF INVENTION

The present invention relates generally to systems and methods for providing refrigeration, or heating and refrigeration. More specifically, the present invention relates to hybrid systems and methods which may provide both refrigeration and electricity generation simultaneously and/or compressed air and refrigeration simultaneously, for example.

BACKGROUND

Refrigeration of a volume or structure can be resource intensive and costly. In the field of mining, for example, refrigeration of underground mines presents a necessary but complex and expensive challenge. Underground mines are typically difficult to access, and may or may not have a robust supply of electricity.

Cooling of underground mines has typically involved chiller-type apparatus designed to reject or remove heat from air circulated through the mine. Particularly where such chiller-type apparatus is installed underground, the removed heat is directed back to the surface, presenting safety and/or infrastructure challenges. Alternatively, conventional cooling strategies have used fluid circulation system ice, ethylene glycol, or water, or fluid circulation systems flowing cooled water/fluid to the mine and returning heated water/fluid to the surface. Such approaches typically involve complicated circulation networks and heat exchangers or spray networks in order to convey heat away from the mine.

Heating of underground mines, or ventilation air intended for underground mines, has conventionally been done by burning fossil fuels such as propane or natural gas, which adds cost to operations and creates greenhouse gases. Nonetheless, some mining operations are located in climates where the ambient air temperature at the surface gets so cold that such heating measures are employed despite the added cost and emissions, so as to make the ventilation air sufficiently warm for use.

Alternative, additional, and/or improved systems and methods for cooling, or cooling and heating, a volume or structure, and particularly underground mines, are desirable.

SUMMARY OF INVENTION

Systems and methods for cooling a volume or structure, which may provide for cogeneration of refrigeration and electricity (or cogeneration of refrigeration and compressed gas, or both), using a cryogenic liquid have now been developed and described in detail herein. In certain embodiments, methods and systems as described herein may convert cryogenic liquid to compressed gas, and/or expanded gas, in a manner which may provide for both cooling of a volume or structure (such as an underground mine) while also generating electricity in a cogeneration process and/or generating a compressed gas (which may be used, for example, to power tools, engines, or equipment operable on compressed gas). It is contemplated that such systems and methods may provide for efficient cooling and/or may avoid certain challenges associated with other cooling strategies which may rely on a robust on-site electrical grid and/or fossil fuels that may produce greenhouse gases and/or may be difficult to provide, particularly at remote mining sites. Systems and methods for both heating and cooling of ventilation air, using exhaust air and cryogenic liquid, are also described in detail herein.

In an embodiment, there is provided herein a method for cooling a volume or structure, said method comprising: converting a cryogenic liquid into a compressed gas, a high velocity gas flow, or both, wherein the cryogenic liquid absorbs ambient heat to provide the compressed gas, the high velocity gas flow, or both; and optionally, expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure, providing an expanded gas; wherein heat exchange is performed between any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and ambient air or ventilation air of the volume or structure, so as to provide cooling to the ambient air or ventilation air of the volume or structure; thereby cooling the volume or structure.

In another embodiment of the above method, the method may further comprise: passing at least a portion of the compressed gas and/or the high velocity gas flow and/or the expanded gas through a turbine, providing rotational energy to the turbine, and generating electricity at a generator coupled with the turbine, thereby providing cogeneration of refrigeration and electricity.

In still another embodiment of any of the above method or methods, the compressed gas and/or the high velocity gas flow and/or the expanded gas may be passed through the turbine during or after expanding the compressed gas, high velocity gas flow, or both, from the high pressure to the lower pressure.

In still another embodiment of any of the above method or methods, the method may further comprise using at least a portion of the generated electricity to generate more cryogenic liquid and/or compressed gas.

In yet another embodiment of any of the above method or methods, at least a portion of the cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, may be mixed with the ambient air or ventilation air of the volume or structure, cooling the ambient air or ventilation air of the volume or structure and/or providing supplemental ambient air or ventilation air for the volume or structure.

In another embodiment of any of the above method or methods, the volume or structure may comprise an underground volume or structure.

In another embodiment of any of the above method or methods, the volume or structure may comprise an underground mine, or portion thereof.

In still another embodiment of any of the above method or methods, the cryogenic liquid may comprise synthetic or designed liquid air.

In yet another embodiment of any of the above method or methods, the cryogenic liquid may be allowed to absorb ambient heat until it is a compressed gas, high velocity gas flow, or both, optionally wherein a temperature at or near ambient temperature is reached, optionally during the step of expanding.

In still another embodiment of any of the above method or methods, the expanded gas may be produced, and the expanded gas may be allowed to absorb ambient heat until the expanded gas reaches a temperature at or near ambient temperature during and/or after the step of expanding.

In still another embodiment of any of the above method or methods, the step of expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure may comprise expanding the high pressure compressed gas, high velocity gas flow, or both, through a nozzle or throttling the high pressure compressed gas, high velocity gas flow, or both, through an orifice, providing cooling to the expanded gas and/or the ambient air or ventilation air of the volume or structure.

In still another embodiment of any of the above method or methods, the method may be used to provide on-demand cooling to the volume or structure; or to provide a pulsed cooling to the volume or structure in which a temperature of the volume or structure is maintained within a range defined by an upper and lower temperature limit through periodic or intermittent cooling at regular or irregular intervals; or any combination thereof.

In another embodiment of any of the above method or methods, the any one or more of cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and the ambient air or ventilation air of the volume or structure may be thermally contacted in a heat exchanger for performing the heat exchange so as to provide cooling to the ambient air or ventilation air of the volume or structure.

In still another embodiment of any of the above method or methods, the any one or more of cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and the ambient air or ventilation air of the volume or structure may be thermally contacted in the heat exchanger via a countercurrent flow.

In yet another embodiment of any of the above method or methods, the ambient air or ventilation air may be supplied to the heat exchanger via a fan.

In still another embodiment of any of the above method or methods, the fan may be at least partially powered by rotation of the turbine and/or electricity from the generator.

In yet another embodiment of any of the above method or methods, the lower pressure may be at or near ambient pressure.

In still another embodiment, there is provided herein a system for cooling a volume or structure, said system comprising: a cryogenic liquid source; and a conversion apparatus integrated with, coupled with, or in thermal communication with, a heat exchanger; wherein the conversion apparatus comprises: an inlet in communication with the cryogenic liquid source and configured for receiving cryogenic liquid from the cryogenic liquid source; a thermal exchange portion configured for thermally contacting received cryogenic liquid with ambient heat to convert the cryogenic liquid into a compressed gas, a high velocity gas flow, or both; optionally, an expansion portion configured for expanding the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, by transitioning the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, from a high pressure to a lower pressure so as to provide an expanded gas; and an outlet for the expanded gas; and wherein the heat exchanger comprises: an inlet for receiving ambient air or ventilation air of the volume or structure; a heat exchange portion configured for thermally contacting received ambient air or ventilation air of the volume or structure with any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure; and an outlet for cooled ambient air or ventilation air of the volume or structure.

In another embodiment of the above system, the ambient heat at the thermal exchange portion may be ambient heat from ambient air or ventilation air of the heat exchanger.

In still another embodiment of the above system or systems, the system may further comprise: a turbine, the turbine configured for receiving at least a portion of the compressed gas and/or the high velocity gas flow and/or the expanded gas of the conversion apparatus therethrough, imparting rotational energy to the turbine; and a generator coupled with the turbine, the generator configured for converting rotational energy from the turbine to electricity, thereby providing cogeneration of refrigeration and electricity.

In still another embodiment of the above system or systems, the turbine may be configured for receiving compressed gas and/or high velocity gas flow and/or expanded gas from the conversion apparatus during or after expansion of the compressed gas, high velocity gas flow, or both.

In yet another embodiment of the above system or systems, the turbine may be configured for receiving high velocity gas flow and/or expanded gas from the conversion apparatus via the outlet for expanded gas.

In still another embodiment of the above system or systems, the system may further comprise: a cryogenic liquid generator configured for using at least a portion of the generated electricity to generate more cryogenic liquid and/or compressed gas.

In still another embodiment of the above system or systems, the system may further comprise: a mixing portion configured for mixing at least a portion of the cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, from the cryogenic liquid source and/or conversion apparatus and/or turbine with ambient air or ventilation air from the heat exchanger, cooling the ambient air or ventilation air and/or providing supplemental ambient air or ventilation air for the volume or structure.

In still another embodiment of the above system or systems, the mixing portion may comprise an inlet for receiving compressed gas, high velocity gas flow, and/or expanded gas from the outlet for expanded gas and/or from the turbine, an inlet for receiving ambient air or ventilation air from the heat exchanger, and an outlet for outputting cooled and/or supplemented ambient air or ventilation air for the volume or structure. In yet another embodiment of the above system or systems, the volume or structure may comprise an underground volume or structure.

In still another embodiment of the above system or systems, the volume or structure may comprise an underground mine, or portion thereof.

In yet another embodiment of the above system or systems, the cryogenic liquid may comprise synthetic or designed liquid air.

In still another embodiment of the above system or systems, the conversion apparatus may be configured for thermally contacting received cryogenic liquid with ambient heat such that the compressed gas and/or high velocity gas flow reaches a temperature at or near ambient temperature, optionally while expanding the cryogenic liquid, compressed gas, or high velocity gas flow at the expansion portion.

In still another embodiment of the above system or systems, the heat exchanger may be configured for thermally contacting the expanded gas with the ambient air or ventilation air such that the expanded gas absorbs heat from the ambient air or ventilation air and the expanded gas reaches a temperature at or near ambient temperature during and/or after expanding the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof.

In yet another embodiment of the above system or systems, the expansion portion of the conversion apparatus may comprise a nozzle or orifice, and the expansion portion of the conversion apparatus may be configured for expanding the cryogenic liquid, compressed gas, or high velocity gas flow by transitioning the cryogenic liquid, compressed gas, or high velocity gas flow from a high pressure to a lower pressure by expanding the high pressure cryogenic liquid, compressed gas, or high velocity gas flow, or any combinations thereof, through the nozzle or throttling the high pressure cryogenic liquid, compressed gas, or high velocity gas flow, or any combinations thereof, through the orifice, providing cooling to the expanded gas and/or the ambient air or ventilation air of the volume or structure.

In still another embodiment of the above system or systems, the system may be configured for providing on-demand cooling to the volume or structure; or to provide a pulsed cooling to the volume or structure in which a temperature of the volume or structure is maintained within a range defined by an upper and lower temperature limit through periodic or intermittent cooling at regular or irregular intervals; or any combination thereof.

In yet another embodiment of the above system or systems, the heat exchanger may be a countercurrent flow-type or other heat exchanger configurations in which any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and the ambient air or ventilation air of the volume or structure are thermally contacted via a countercurrent or concurrent flow.

In still another embodiment of the above system or systems, the system may be configured with a fan for supplying the ambient air or ventilation air to the heat exchanger inlet.

In another embodiment of the above system or systems, the fan may be at least partially powered by rotation of the turbine and/or electricity from the generator.

In still another embodiment of the above system or systems, the conversion apparatus may be configured such that the lower pressure is at or near ambient pressure.

In another embodiment, there is provided herein a system for cooling a volume or structure, said system comprising: a cryogenic liquid source; and a conversion apparatus integrated with a heat exchanger; wherein the conversion apparatus comprises: an inlet in communication with the cryogenic liquid source and configured for receiving cryogenic liquid from the cryogenic liquid source; a thermal exchange portion configured for thermally contacting received cryogenic liquid with ambient heat to convert the cryogenic liquid into a compressed gas, a high velocity gas flow, or both; an expansion portion configured for expanding the compressed gas, or high velocity gas flow, or both, by transitioning the compressed gas or high velocity gas flow, or both from a high pressure to a lower pressure so as to provide an expanded gas; and an outlet for the expanded gas; and wherein the heat exchanger comprises: an inlet for receiving ambient air or ventilation air of the volume or structure; a heat exchange portion configured for thermally contacting received ambient air or ventilation air of the volume or structure with the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, passing through the thermal exchange portion and the expansion portion of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure; and an outlet for cooled ambient air or ventilation air of the volume or structure.

In another embodiment of the above system, the system may further comprise: a turbine, the turbine configured for receiving at least a portion of the compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, from the outlet of the conversion apparatus therethrough, imparting rotational energy to the turbine; and a generator coupled with the turbine, the generator configured for converting rotational energy from the turbine to electricity, thereby providing cogeneration of refrigeration and electricity.

In another embodiment of the above system or systems, the system may be configured with a fan for supplying the ambient air or ventilation air to the heat exchanger inlet, the fan being independently powered or powered by rotational energy of the turbine and/or electricity from the generator.

In yet another embodiment of the above system or systems, the expanded gas exiting the outlet of the conversion apparatus and/or exiting the turbine may be mixed with the cooled ambient air or ventilation air exiting the outlet of the heat exchanger, further cooling the ambient air or ventilation air and/or providing supplemental ambient air or ventilation air for the volume or structure..

In another embodiment of any of the above method or methods, the method may further comprise collecting at least a portion of compressed gas derived from the cryogenic liquid, providing a collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In another embodiment of any of the above system or systems, the system may further comprise a compressed gas storage tank configured to collect at least a portion of compressed gas derived from the cryogenic liquid, providing a collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In yet another embodiment there is provided herein a method for controlling or adjusting temperature of a volume or structure, said method comprising: heating a ventilation air being supplied to the volume or structure when the ventilation air temperature is below a desired temperature or temperature range by performing a heat exchange between the ventilation air and exhaust air returning from the volume or structure, the returning exhaust air being hotter than the ventilation air such that the ventilation air is heated by the heat exchange; cooling the ventilation air being supplied to the volume or structure when the ventilation air temperature is above the desired temperature or temperature range by performing a heat exchange between the ventilation air and a cooling stream generated using a cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof, the cooling stream being cooler than the ventilation air such that the ventilation air is cooled by the heat exchange; and supplying the heated or cooled ventilation air to the volume or structure.

In another embodiment of the above method, the step of heating may comprise performing heat exchange between the ventilation air and exhaust air without mixing the ventilation air with the exhaust air.

In still another embodiment of any of the above method or methods, the step of cooling may comprise generating the cooling stream by:

(a) thermally contacting, or mixing, the cryogenic liquid or cold compressed gas, high velocity gas flow, or expanded gas derived from the cryogenic liquid, or any combination thereof, with an ambient air, the exhaust air, or a combination thereof, thereby providing the cooling stream;

(b) converting the cryogenic liquid into a cold compressed gas, high velocity gas flow, or both, wherein the cryogenic liquid absorbs heat to provide the compressed gas, the high velocity gas flow, or both; and, optionally, expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure, providing an expanded gas and absorbing additional heat; and thermally contacting, or mixing, the cryogenic liquid, compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, with an ambient air, the exhaust air, or a combination thereof, such that cooling occurs, thereby providing the cooling stream; or

(c) converting the cryogenic liquid into a cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, and using the cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, as the cooling stream, wherein the cooling stream may optionally further comprise ambient air, the exhaust air, or a combination thereof; or any combinations thereof.

In still another embodiment of any of the above method or methods, the expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure may comprise expanding the high pressure compressed gas, high velocity gas flow, or both, through a nozzle or throttling the high pressure compressed gas, high velocity gas flow, or both, through an orifice, providing cooling.

In yet another embodiment of any of the above method or methods, the step of cooling may comprise mixing the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with ambient air, with the returning exhaust air, or a combination thereof, to provide the cooling stream; or wherein the step of cooling comprises thermally contacting the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, via non-mixing heat exchange with ambient air, with the returning exhaust air, or a combination thereof, cooling the ambient air, returning exhaust air, or the combination thereof to provide the cooling stream.

In another embodiment of any of the above method or methods, the step of cooling may comprise performing heat exchange between the ventilation air and the cooling stream without mixing the ventilation air with the cooling stream.

In still another embodiment of any of the above method or methods, the heating and cooling steps may be performed using the same heat exchanger.

In yet another embodiment of any of the above method or methods, the method may further comprise generating a compressed gas and/or the high velocity gas flow and/or expanded gas from the cryogenic liquid and passing the compressed gas and/or the high velocity gas flow and/or expanded gas through a turbine, providing rotational energy to the turbine, and generating electricity at a generator coupled with the turbine, thereby providing electricity.

In another embodiment of any of the above method or methods, the method may further comprise collecting at least a portion of compressed gas derived from the cryogenic liquid, providing a collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In still another embodiment of any of the above method or methods, the volume or structure may comprise an underground volume or structure.

In yet another embodiment of any of the above method or methods, the volume or structure may comprise an underground mine, or a portion thereof.

In another embodiment of any of the above method or methods, the steps of heating and cooling may be performed at the surface.

In still another embodiment of any of the above method or methods, the exhaust air may comprise upcast air from a mine, the ventilation air comprises downcast air for the mine, or both.

In still another embodiment of any of the above method or methods, the ventilation air may be cooled via heat exchange when the exhaust air is cooler than the ventilation air, and the step of cooling is used to provide on-demand cooling when the temperature of the untreated exhaust air is not sufficiently cool to maintain the ventilation air at or within the desired temperature or temperature range.

In still another embodiment of any of the above method or methods, the ventilation air is not mixed with the cooling stream, and the cryogenic liquid is or comprises liquid nitrogen.

In yet another embodiment of any of the above method or methods, heat exchange in the cooling and/or heating steps may be performed using a non-mixing air-to-air parallel plate-type heat exchanger.

In another embodiment, there is provided herein a system for controlling or adjusting temperature of a volume or structure, said system comprising: a heat exchange unit comprising a ventilation air input, a ventilation air output, an exhaust air input, an exhaust air output, and a heat exchanger configured to exchange heat to and from the ventilation air; and a cooling unit configured to generate a cooling stream; the system configured for heating a ventilation air being supplied to the volume or structure when the ventilation air temperature is below a desired temperature or temperature range by passing the ventilation air from the ventilation air input, through the heat exchanger, and out the ventilation air output, while passing exhaust air returning from the volume or structure, the returning exhaust air being hotter than the ventilation air, from the exhaust air input, through the heat exchanger, and out the exhaust air output, such that the ventilation air is heated by the heat exchange with the exhaust air in the heat exchange unit; and the system configured for cooling the ventilation air being supplied to the volume or structure when the ventilation air temperature is above the desired temperature or temperature range by passing the ventilation air from the ventilation air input, through the heat exchanger, and out the ventilation air output, while passing a cooling stream, the cooling stream being cooler than the ventilation air, through the heat exchanger (optionally input via the exhaust air input and output via the exhaust air output), such that the ventilation air is cooled by the heat exchange with the cooling stream; the ventilation air output configured for supplying the ventilation air to the volume or structure.

In another embodiment of the above system, the cooling unit may comprise a cryogenic liquid- based cooling unit configured to generate the cooling stream using a cryogenic liquid.

In still another embodiment of any of the above system or systems, the cryogenic liquid-based cooling unit may comprise a cryogenic liquid storage tank, and a mixing/expansion chamber for generating the cooling stream using a cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof, the cooling stream being cooler than the ventilation air.

In still another embodiment of any of the above system or systems, the system may further comprise a cryogenic liquid generation unit in communication with the cryogenic storage unit.

In yet another embodiment of any of the above system or systems, the heat exchange unit may be or comprise a non-mixing heat exchanger which exchanges heat between the ventilation air and exhaust air without mixing the ventilation air with the exhaust air. In another embodiment of any of the above system or systems, the cooling unit may be configured for generating the cooling stream, and the cooling unit may comprise:

(a) a mixing/expansion chamber comprising an input for cryogenic liquid or cold compressed gas, high velocity gas flow, or expanded gas derived from the cryogenic liquid, or any combination thereof, and an input for an ambient air, the exhaust air, or a combination thereof, the mixing/expansion chamber structured to thermally contact, or mix, the ambient air, the exhaust air, or a combination thereof and the cryogenic liquid or cold compressed gas, high velocity gas flow, or expanded gas derived from the cryogenic liquid, thereby providing the cooling stream;

(b) a mixing/expansion chamber comprising an input for cryogenic liquid; a conversion section for converting at least a portion of the input cryogenic liquid into a cold compressed gas, high velocity gas flow, or both, wherein the cryogenic liquid absorbs heat to provide the compressed gas, the high velocity gas flow, or both, and optionally, for expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure, providing an expanded gas and absorbing additional heat; and an input for an ambient air, the exhaust air, or a combination thereof; the mixing/expansion chamber structured to thermally contact, or mix, the cryogenic liquid, compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, with the ambient air, the exhaust air, or the combination thereof, such that cooling occurs, thereby providing the cooling stream; or

(c) a mixing/expansion chamber comprising an input for cryogenic liquid; a conversion section for converting the cryogenic liquid into a cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof; and an output for the cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, to be used as the cooling stream; wherein the conversion section and/or the output for cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof optionally further comprises an input for ambient air, the exhaust air, or a combination thereof, such that the output cooling stream additionally comprises ambient air and/or exhaust air; or any combinations thereof. In still another embodiment of any of the above system or systems, the conversion section may comprise a nozzle or orifice, and expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure comprises expanding the high pressure compressed gas, high velocity gas flow, or both, through the nozzle or throttling the high pressure compressed gas, high velocity gas flow, or both, through the orifice, providing cooling.

In still another embodiment of any of the above system or systems, the cooling unit may be configured to mix the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with ambient air, with the returning exhaust air, or a combination thereof, to provide the cooling stream; or wherein the cooling unit is configured to thermally contact the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, via non-mixing heat exchange, with ambient air, with the returning exhaust air, or a combination thereof, cooling the ambient air, returning exhaust air, or the combination thereof to provide the cooling stream.

In yet another embodiment of any of the above system or systems, the heat exchange unit may be or comprise a non-mixing heat exchange unit which performs heat exchange between the ventilation air and the cooling stream without mixing the ventilation air with the cooling stream.

In another embodiment of any of the above system or systems, the system may further comprise a turbine configured to receive at least a portion of compressed gas and/or high velocity gas flow and/or expanded gas from the cryogenic liquid, which is passed through the turbine, providing rotational energy to the turbine, and generating electricity at a generator coupled with the turbine, thereby providing electricity.

In yet another embodiment of any of the above system or systems, the system may further comprise a collection unit for collecting and storing at least a portion of compressed gas derived from the cryogenic liquid, the collection unit having an outlet for providing collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In still another embodiment of any of the above system or systems, the volume or structure may comprise an underground volume or structure. In another embodiment of any of the above system or systems, the volume or structure may comprise an underground mine, or a portion thereof.

In yet another embodiment of any of the above system or systems, the cooling unit and the heat exchange unit may be installed at the surface.

In still another embodiment of any of the above system or systems, the exhaust air may comprise upcast air from a mine, the ventilation air comprises downcast air for the mine, or both.

In yet another embodiment of any of the above system or systems, the ventilation air may be cooled via heat exchange when the exhaust air is cooler than the ventilation air, and the cooling unit may be used to provide on-demand cooling when the temperature of the untreated exhaust air is not sufficiently cool to maintain the ventilation air at or within the desired temperature or temperature range.

In yet another embodiment of any of the above system or systems, the ventilation air is not mixed with the cooling stream, and the cryogenic liquid is or comprises liquid nitrogen.

In another embodiment of any of the above system or systems, the heat exchanger in the heat exchange unit may comprise a non-mixing air-to-air parallel plate-type heat exchanger.

In still another embodiment of any of the above system or systems, the cooling unit may comprise a cryogenic liquid-based cooling unit configured to generate the cooling stream using a cryogenic liquid; wherein the cryogenic liquid-based cooling unit may comprise a cryogenic liquid storage tank, and a mixing/expansion chamber for generating the cooling stream using the cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof, the cooling stream being cooler than the ventilation air; and wherein the mixing/expansion chamber may comprise an inlet for ambient air, exhaust air, or a mixture thereof; a cryogenic fluid inlet (which may, in certain embodiments, be in the form of a substantially annular tube or ring comprising a plurality of exit ports, such as a perforated annulus) for input into the mixing/expansion chamber so as to provide mixing and cooling; and an output for the cooling stream, the outlet being in communication with the heat exchange unit for supplying the cooling stream thereto. In certain embodiments, one or more of various arrangements may be provided which may separate the phase change from liquid to gas (often referred to as a “flash” phase change, typically quick - typically almost half of the heat may be absorbed in this stage, or about 205 kJ/kg) from the expansion of the gas (in this stage typically slightly more heat may be absorbed, depending on the temperature difference about 225 kJ/kg for ambient temperature of 300K, for example), with systems to capture the cold from each stage. This may, in certain embodiments, involve a series of containment systems, heat exchangers, and conduit connections to contain the overall heat exchange, for example..

BRIEF DESCRIPTION OF DRAWINGS

These and other features will become further understood having regard to the following drawings in which:

FIGURE 1 shows results from a computational fluid dynamics model providing results as further described in Example 1;

FIGURE 2 shows calculated on-demand chilling response time, showing results over a 500 meter shaft for cooling created by introducing the cryogenic liquid air and the rapid response time, which may be correlated to the air flow velocity, as described in Example 1;

FIGURE 3 shows an embodiment of a compressed air system having liquid air storage and compressed air storage units as described herein;

FIGURE 4 shows a schematic of an embodiment of a system as described herein, wherein the system may comprise an underground electrical power and chilling system, as described in further detail in Example 1;

FIGURE 5 shows a schematic of another embodiment of a system as described herein, wherein the system comprises an electrical power and chilling system;

FIGURE 6 shows a schematic of an embodiment of a method for cooling a volume or structure as described herein; FIGURE 7 shows a schematic of a system for cooling a volume or structure as described herein;

FIGURE 8 depicts a heat exchange system as described in Example 3, comprising a heat exchanger, and inlets and outlets for both upcast and downcast air. Flow direction of the upcast and downcast air is shown in arrows. In the depiction, the upcast air is hot, and heat is transferred to the downcast air. The upcast air and the downcast air are not mixed;

FIGURE 9 shows the heat exchange system of Figure 8, installed and integrated with pre existing ventilation exhaust (including exhaust fans) at the surface of a mine;

FIGURE 10 shows the heat exchange system of Figure 9, further including an extension ventilation duct connection to the downcast air on the surface for supplying the downcast air to the mine. The inset (not to scale) depicts a cryogenic liquid-based chilling system (which may include a cryogenic liquid storage tank and may optionally include a cryogenic liquid generator), which may be used to cool the downcast air, and/or may be used to cool the upcast air such that the upcast air cools the downcast air, or both;

FIGURE 11 shows calculated chilling for an example mine using weather data from a random day (May 24, 2015) for an underground target WBGT of 35°C;

FIGURE 12 shows a cryogenic liquid chilling system as described in Example 3, in which the cryogenic liquid may flow from the low pressure storage tank (207) to a mixing container (208) where air from the upcast shaft (or ambient air, or a mixture of both) may be used to provide a flow velocity and appropriate volume, such that, heat from the incoming downcast air at the heat exchanger is transferred to the cold air flow (generated within the mixing chamber (208) and supplied to the heat exchanger) in an efficient manner. 12(A) provides an isometric view, 12(B) provides a back view, 12(C) provides a front view, 12(D) provides a right view, and 12(E) provides a top view of the cryogenic liquid-based chilling system;

FIGURE 13(A) shows an image of the prototype described in Example 3, in which liquid enters the system from the right and continues through the pipe to the turbine. The depicted prototype has the heat exchanger insulated, and is generating both chilling and power. 13(B) shows results from the prototype for the heat flux removed from the ambient fan driven air flowing through the insulated container containing the heat exchanger;

FIGURE 14 shows temperatures of the ambient room, see triangles at bottom to indicate the room air change times, and note the instantaneous temperature change from the time the cryogenic liquid is started flowing through the prototype system, as discussed for the prototype testing described in Example 3;

FIGURE 15 shows additional detail of an example of a cryogenic liquid chilling system as depicted in Figure 12 and described in Example 3. The cryogenic liquid chilling system comprises an annular ring for introducing cryogenic liquid (or cold gas therefrom) into a mixing chamber for mixing with upcast air to provide a cooled air;

FIGURE 16 shows CFD modelling internal to the mixing chamber as described in Example 3. Computational fluid dynamics modelling for about the first ten seconds from the start of the cryogenic flow is shown, this is a cross section through the centre of the mixing chamber shown in Figure 15;

FIGURE 17 shows additional CFD modelling as described in Example 3, and shows details of the interaction at the mixing zone where the cryogenic liquid expands and mixes with the incoming ambient air flow. Top left panel shows a close up cut through the cryogenic inlet ring at 0.43 s from the start of cryogenic flow. Top right panel shows a close up cut through the cryogenic inlet ring at 13.3s from the start of cryogenic flow. Bottom panel shows flow trajectories of a simulation for incoming air temperature of 20 C at 90m ³ /s and 10 m ³ /s of air created from the expansion of the cryogenic liquid to illustrate the mixing; and

FIGURE 18 shows additional CFD modelling as described in Example 3, and shows flow trajectories of a simulation for incoming air temperature of 35 C at 90 m ³ /s and 10 m ³ /s of air created from the expansion of the cryogenic liquid to illustrate the mixing. Cross section cut plots are included to represent the temperature profiles. DETAILED DESCRIPTION

Described herein are systems and methods for providing refrigeration, or cogeneration of refrigeration and electricity. Dual heating and cooling systems and methods are also described. It will be appreciated that embodiments and examples are provided for illustrative purposes intended for those skilled in the art, and are not meant to be limiting in any way.

Systems and methods for cooling a volume or structure, which may provide for cogeneration of refrigeration and electricity, using a cryogenic liquid have now been developed and described in detail herein. In certain embodiments, methods and systems as described herein may convert cryogenic liquid to compressed gas, and/or expanded gas, in a manner which may provide for both cooling of a volume or structure (such as an underground mine) while also generating electricity in a cogeneration process. It is contemplated that such systems and methods may provide for efficient cooling and/or may avoid certain challenges associated with other cooling strategies which may rely on a robust on-site electrical grid and/or fossil fuels that may be difficult or expensive to provide, particularly at remote mining sites. Systems and methods for both heating and cooling of ventilation air, using exhaust air and cryogenic liquid, are also described in detail herein.

In certain embodiments, a cryogenic liquid may be used in systems and methods as described herein to provide chilling of a volume or structure while also providing electrical power (e.g. heat from a volume or structure, such as a mine, may be converted to electricity using cryogenic liquid and a turbine as described herein); or to provide chilling of a volume or structure by absorbing heat, while also providing compressed gas at suitable pressure(s) for use by a variety of different operations on or off-site, such as but not limited to operation of vehicles, equipment, engines (such as those produced by Dearman Engine Company) or tools powered by compressed gas.

In an embodiment, there is provided herein a method for cooling a volume or structure, said method comprising: converting or expanding a cryogenic liquid into a compressed gas, a high velocity gas flow, or both, wherein the cryogenic liquid may absorb ambient heat to provide the compressed gas, the high velocity gas flow, or both; and/or optionally, expanding the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, from a high pressure to a lower pressure, providing an expanded gas; wherein heat exchange is performed between any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and ambient air or ventilation air of the volume or structure, so as to provide cooling to the ambient air or ventilation air of the volume or structure; thereby cooling the volume or structure.

As will be understood, in certain embodiments, the converting and expanding steps may be separate steps, or may be combined such that the cryogenic liquid may be converted to the expanded gas without actually isolating or accumulating the compressed gas. In certain embodiments, the compressed gas may comprise a gas at a pressure higher than ambient pressure, or may comprise a gas moving at high velocity (e.g. a high velocity gas flow), or both. In certain embodiments, the steps of converting and expanding may be combined, such that the step of converting may comprise converting a cryogenic liquid into an expanded gas by allowing the cryogenic liquid to absorb ambient heat and/or expanding the cryogenic liquid or gas therefrom (such as a compressed gas or high velocity gas, for example) from a high pressure to a lower pressure so as to produce the expanded gas.

In certain embodiments, the cryogenic liquid may be converted to the expanded gas without actually producing, isolating, or accumulating the compressed gas, via expanding the cryogenic liquid to a high velocity gas (which may still involve creating some pressure), which may be used to exchange heat and/or power a turbine as described in further detail below.

As will be understood, the volume or structure may be any volume or structure of interest, for which cooling may be desired on an ongoing or temporary basis. In certain embodiments, the volume may be an interior volume of a structure or other enclosed volume which is at least partially insulated from the environment. In certain embodiments, the volume or structure may comprise an underground volume or structure. In certain embodiments, the underground volume or structure may comprise a mine, mine shaft, or other underground tunnel, cavity, or structure, or any portion thereof. In certain embodiments, the volume or structure may comprise an underground mine, or a portion thereof.

As will also be understood, cooling of the volume or structure may comprise decreasing a temperature of the volume or structure, which may be an air temperature or ambient temperature of the volume or structure, for example. In certain embodiments, cooling of the volume or structure may comprise refrigerating, air conditioning, or otherwise reducing heat of the volume or structure. In certain embodiments, cooling may be provided on an ongoing or temporary basis. In certain embodiments, the cooling may be provided on-demand to the volume or structure as desired; or may be provided via a pulsed cooling to the volume or structure in which a temperature of the volume or structure may be maintained within a range defined by an upper and lower temperature limit through periodic or intermittent cooling at regular or irregular intervals; or any combination thereof.

In certain embodiments, the cryogenic liquid may comprise any suitable cryogenic liquid known to the skilled person having regard to the teachings herein, which may be selected to suit the particular implementation and/or application. In certain embodiments, such as where gas from the cryogenic liquid will eventually be introduced to air of the volume or structure and the air of the volume or structure will be breathed be a human or animal, the cryogenic liquid may be selected such that it is non-toxic and provides breathable gas for the volume or structure. In certain embodiments, the cryogenic liquid may comprise liquid air, for example. In certain embodiments, the cryogenic liquid may comprise a nitrogen oxygen mix of about 79% to 21% respectively. For situations where the gas produced by the cryogen is in open air or not breathed by human or animal, the cryogen may be pure nitrogen. In certain embodiments, a liquefaction system separating the nitrogen, oxygen and argon may be used, and the nitrogen and oxygen may be used to create suitable mixtures while the argon may be sold on the open market, for example.

As will be understood, the choice of cryogenic or liquid air will be tailored to suit the particular application, taking into account safety and other such considerations. In certain embodiments, the cryogenic liquid may comprise a synthetic or designed liquid air tailored for the particular application. Making liquid air from ambient air, the concentration starts at about 78% N2 and 21% 02, as the liquid is created the oxygen may become enriched up to about 35% which is a concentration of oxygen that is a combustion hazard and should be prevented. Accordingly, the synthetic or designed liquid air may be controlled such that the ratios of gas(es) provided are confirmed to be safe and appropriate for the particular application. In certain embodiments, the cryogenic liquid may be a designer cryogenic liquid of liquid air comprising a mix of liquid nitrogen (LN2) and liquid oxygen (L02) tailored to be suitable for the particular application. By way of example, in cases where there are personnel working outside, in an enclosed volume, or underground, the mix of the cryogenic liquid would change and be tailored accordingly. For outside open air ventilated applications the mix may be predominantly LN2, and for underground the mix may be adjusted depending on the flow and conditions required for safety and other factors.

In certain embodiments, converting the cryogenic liquid into a compressed gas or high velocity gas or both may comprise allowing the cryogenic liquid to absorb ambient heat and/or expanding the cryogenic liquid, thereby providing the compressed gas or high velocity gas or both. In certain embodiments, the cryogenic liquid may be thermally contacted such that it may absorb ambient heat (such as ambient heat from the volume or structure, or a ventilation air being supplied to the volume or structure, for example), providing heat of vaporization to the cryogenic liquid so as to produce a higher density air or the compressed gas or expanding gas or high velocity gas, which typically may still be quite cold. In certain embodiments, the cold compressed or high velocity or expanded gas may be allowed to absorb additional ambient heat, which may warm the compressed gas or high velocity or expanded gas (and may also increase pressure of the compressed gas, for example). In certain embodiments, the compressed gas or high velocity gas may be allowed to absorb ambient heat until the compressed gas or high velocity gas reaches a temperature at or near ambient temperature prior to the step of expanding, or during the step of expanding.

In certain embodiments, the compressed gas, high velocity gas flow, or both, may be expanded from a high pressure to a lower pressure, thereby providing an expanded gas (which may provide cooling via the Joule Thompson effect). In certain embodiments, the lower pressure may be at or near ambient pressure. In certain embodiments, the expanded gas may comprise a lower pressure gas, or a gas at or near ambient pressure, derived from the compressed gas, high velocity gas flow, or both. In certain embodiments, expansion of the compressed gas, high velocity gas flow, or both, may comprise flowing of the compressed gas, high velocity gas flow, or both, from a confined volume or high pressure region to a comparatively expanded volume or lower pressure region. In certain embodiments, expansion of the compressed gas, high velocity gas flow, or both, may result in cooling of the gas. In certain embodiments, expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure may comprise expanding the high pressure compressed gas, high velocity gas flow, or both, through a nozzle or throttling the high pressure compressed gas, high velocity gas flow, or both, through an orifice to a lower pressure, which may provide cooling to the expanded gas and/or the ambient air or ventilation air of the volume or structure. In certain embodiments, the expanded gas may be allowed to absorb ambient heat until the expanded gas reaches a temperature at or near ambient temperature during and/or after the step of expanding. In certain embodiments, a compressed gas or high velocity gas flow (such as a gas at a pressure of about 50 to 60 Bar, for example) may be used to provide a Joule Thompson effect chilling by supplying the compressed gas or high velocity gas or high pressure gas to a Joule Thompson device.

In certain embodiments, heat exchange may be performed between any one or more of the cryogenic liquid, the compressed gas, high velocity gas flow, the expanded gas, or any combinations thereof, and ambient air or ventilation air of the volume or structure, so as to provide cooling to the ambient air or ventilation air of the volume or structure. In certain embodiments, the heat exchange may comprise placing any one or more of the cryogenic liquid, the compressed gas, high velocity gas flow, the expanded gas, or any combinations thereof, in thermal contact with the ambient air or ventilation air of the volume or structure, the ambient air or ventilation air being comparatively warmer than the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, such that heat may transfer from the ambient air or ventilation air to the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or combinations thereof, resulting in cooling of the ambient air or ventilation air of the volume or structure. In certain embodiments, the heat exchange may be performed without mixing of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with the ambient air or ventilation air (for example, the thermal contact may involve heat transfer across a barrier such as via countercurrent flow or concurrent flow in a heat exchanger, for example). In certain embodiments, the heat exchange may be performed with mixing of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with the ambient air or ventilation air (for example, a stream of relatively cold cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof may be introduced into the ambient air or ventilation air to provide cooling thereto). In certain embodiments, a portion of the heat exchange may be performed without mixing, and a portion of the heat exchange may be performed with mixing.

In certain embodiments, any one or more of cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and the ambient air or ventilation air of the volume or structure may be thermally contacted in a heat exchanger for performing the heat exchange so as to provide cooling to the ambient air or ventilation air of the volume or structure. In certain embodiments, the any one or more of cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and the ambient air or ventilation air of the volume or structure may be thermally contacted in the heat exchanger via a countercurrent flow.

In certain embodiments, the ambient air or ventilation air of the volume or structure may comprise ambient air or ventilation air already found in or around the volume or structure, or may comprise ambient air or ventilation air which will be (or is being) directed to the volume or structure, or any combination thereof.

In certain embodiments, the present methods may offer several opportunities for providing cooling to the ambient air or ventilation air. By way of example, when converting the cryogenic liquid to a compressed gas and/or high velocity gas flow, a heat of vaporization may be absorbed by the cryogenic liquid, which may be obtained from the ambient air or ventilation air in certain embodiments. As another example, the resultant compressed gas and/or high velocity gas flow may typically still be quite cold upon production, and the compressed gas and/or high velocity gas flow may be allowed to absorb heat from the ambient air or ventilation air to become warmer (and typically increase in pressure), which may provide further cooling to the ambient air or ventilation air. As yet another example, the compressed gas and/or high velocity gas flow may be expanded to produce an expanded gas, which may in certain embodiments result in cooling of the gas such that the expanded gas may be relatively cool gas. This cool gas may then be thermally contacted (with or without mixing) with the ambient air or ventilation air, providing cooling to the ambient air or ventilation air. As will be understood, any of the cryogenic liquid, compressed gas, high velocity gas flow, and expanded gas may be provided at a temperature which is cooler than the ambient air or ventilation air, and therefore may be used for cooling the ambient air or ventilation air either via heat exchange across a barrier, or via mixing with the ambient air or ventilation air, or both, for example.

In certain embodiments, the methods as described herein may further provide for electricity generation. In certain embodiments, the methods as described herein may provide for cogeneration of cooling/refrigeration and electricity.

Accordingly, in certain embodiments, methods as described herein may further comprise: passing at least a portion of the compressed gas and/or high velocity gas flow and/or expanded gas through a turbine, providing rotational energy to the turbine, and generating electricity at a generator coupled with the turbine, thereby providing cogeneration of refrigeration and electricity.

In certain embodiments, the turbine may be a mixed flow turbine. In certain embodiments, the turbine may be used in an expansion portion or stem to capture energy. In certain embodiments, the turbine may be used in combination with, or may be replaced by, a piston or rotary engine where the liquid may be injected into the piston to expand (similar principle to a gasoline engine) in order to capture energy.

In certain embodiments, the compressed gas, high velocity gas flow, and/or expanded gas may be passed through the turbine during or after the step of expanding the compressed gas and/or high velocity gas flow from the high pressure to the lower pressure. In certain embodiments, energy from the compressed gas and/or high velocity gas flow being released by expansion of the compressed gas and/or high velocity gas flow may be captured by the turbine, which may be used to power a generator to provide electricity. In certain embodiments, at least a portion of the generated electricity may be used to generate more cryogenic liquid and/or compressed gas to be used in the methods described herein.

In certain embodiments, the ambient air or ventilation air may be supplied to the heat exchanger via a fan or pump, and in certain further embodiments the fan or pump may be at least partially powered by rotation of the turbine and/or electricity from the generator.

In certain embodiments, methods as described herein may be used to provide supplemental air to the volume or structure. As will be understood, certain volumes or structures, such as an underground mine, may be supplied with air from the surface on a regular basis, the conditioning and pumping of which may be energy intensive and/or costly. Accordingly, in certain embodiments, methods as described herein may be used to provide supplemental air to the volume or structure, which may reduce demand for air from the surface, for example.

In certain embodiments, at least a portion of the cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, may be mixed with the ambient air or ventilation air of the volume or structure, which may cool the ambient air or ventilation air of the volume or structure and/or may provide supplemental ambient air or ventilation air for the volume or structure.

In certain embodiments, opening a valve to the cryogenic liquid or otherwise exposing the cryogenic liquid may result in the cryogenic liquid rapidly expanding, absorbing the latent heat of vapourasition and the heat to raise it to ambient temperature, which would consequently be lower than the initial ambient temperature prior to the liquid cryogen being introduced, thereby providing cooling. In another embodiment, creating electricity through a turbine coupled to a generator may be used (as will be understood, the skilled person will be aware of a wide variety of different turbines which may be used, and in certain embodiments some liquid may enter the turbine, although this may be optional or may typically be avoided) and the turbine(s) may for example be arranged in stages to accommodate the expanding gas all the while the heat for the latent heat of vapourisation and further expansion may be taken from the environment. In another embodiment, when creating compressed air for use to run equipment, for example, the latent heat of vapourisation may be absorbed in what is often called a flash because it may be so fast then a very cold higher density gas may absorb heat from the environment to be raised to the ambient temperature that would be lower than the initial ambient temperature due to the heat taken out by the cryogenic liquids, for example.

An example of a method for cooling a volume or structure as described herein is depicted in Figure 6. The example depicted in Figure 6 represents a preferred embodiment, producing both chilling and electricity. In the depicted embodiment, a cryogenic liquid (101) (which is very cold in temperature) is converted (102) from a liquid into a compressed gas or high velocity gas (103) or expanded gas by absorbing the latent heat of vapourisation, wherein the cryogenic liquid (101) absorbs (107) ambient heat (104) (in this example, from the ambient air or ventilation air (108)) to provide the compressed gas or high velocity gas (103) or expanded gas. The compressed gas or high velocity gas (103) or expanded gas is cold, and is allowed to absorb further ambient heat (103) to warm further and increase in pressure in the depicted embodiment. The compressed gas or high velocity gas (103) or expanded gas is then expanded (105) further from a high pressure and/or high velocity to a lower pressure, providing an expanded gas (which may be at high velocity) (106). Expansion provides a cooling effect in this example, such that the resultant expanded gas (106) increases in entrophy; thus, absorbs heat from the surroundings. The expanded gas (106) is then allowed to mix (107) with the ambient air and may absorb additional ambient heat from the ambient air or ventilation air (108), providing further cooling to the ambient air or ventilation air (108). In the depicted method embodiment, heat exchange is performed between the cryogenic liquid (101) and the ambient air or ventilation air (108) when producing the compressed gas or high velocity gas (103) or expanded gas, and heat exchange is performed between the expanded gas (106) (or a mixture of the compressed gas and/or high velocity gas and/or the expanded gas, as the expanded gas is forming) and the ambient air or ventilation air (108). Accordingly, cooling is provided to the ambient air or ventilation air of the volume or structure, providing (109) a cooled ambient air or ventilation air (110). The expanded gas (106) (which may be at high velocity) is then passed (111) through a turbine (112) coupled with a generator (113), so as to provide electricity (114). Expanded gas (106), or expanded gas exiting the turbine, or both, may then be introduced into (115) (i.e. mixed with) ambient air or ventilation air (108), cooled ambient air or ventilation air (110), or both, so as to provide cooled and/or supplemented ambient air or ventilation air (116), which may be in, or introduced to, the volume or structure, providing cooling thereto. In the depicted embodiment, the volume or structure is an underground mine (100).

In another embodiment, there is provided herein a method for cooling a volume or structure, said method comprising: expanding a cryogenic liquid to a compressed gas, high velocity gas flow, or both; and performing heat exchange between any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, or any combinations thereof, and ambient air or ventilation air of the volume or structure, so as to provide cooling to the ambient air or ventilation air of the volume or structure; thereby cooling the volume or structure. In another embodiment, the compressed gas and/or high velocity gas flow may be passed through a turbine coupled with a generator, creating electricity.

In another embodiment, there is provided herein a system for cooling a volume or structure, said system comprising: a cryogenic liquid source; and a conversion apparatus integrated with, coupled with, or in thermal communication with, a heat exchanger; wherein the conversion apparatus comprises: an inlet in communication with the cryogenic liquid source and configured for receiving cryogenic liquid from the cryogenic liquid source; a thermal exchange portion configured for thermally contacting received cryogenic liquid with ambient heat to convert the cryogenic liquid into a compressed gas or a high velocity gas flow or both; optionally, an expansion portion configured for expanding the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, by transitioning the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, from a high pressure to a lower pressure so as to provide an expanded gas; and an outlet for the gas; and wherein the heat exchanger comprises: an inlet for receiving ambient air or ventilation air of the volume or structure; a heat exchange portion configured for thermally contacting received ambient air or ventilation air of the volume or structure with any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure; and an outlet for cooled ambient air or ventilation air of the volume or structure.

In certain embodiments, a system as described herein may be for use in performing a method as described herein.

As will be understood, in certain embodiments, the thermal exchange portion and the expansion portion may be separate, or may be combined such that the cryogenic liquid may be converted to the expanded gas by the thermal exchange portion and expansion portion without actually isolating or accumulating the compressed gas. In certain embodiments, the compressed gas may comprise a gas at a pressure higher than ambient pressure, or may comprise a gas moving at high velocity (e.g. a high velocity gas flow), or both. In certain embodiments, the thermal exchange portion and the expansion portion may be combined such that the combined portion may convert a cryogenic liquid into an expanded gas by allowing the cryogenic liquid to absorb ambient heat and/or expanding the cryogenic liquid or gas therefrom (such as a compressed gas or high velocity gas, for example) from a high pressure to a lower pressure so as to produce the expanded gas.

In certain embodiments, compressed gas may be created by, for example, injecting the liquid into a confined pressure container, and the compressed gas may then, optionally, be expanded to create more chilling via the Joule Thompson Effect, or the gas may be allowed to freely expand in a tube or other channel, picking up velocity and may then be used to turn a turbine and generator, or any combinations thereof.

In certain embodiments, the cryogenic liquid source may comprise a tank or reservoir for containing the cryogenic liquid, or may comprise a cryogenic liquid generator, or both.

In certain embodiments, the conversion apparatus and the heat exchanger may be a combined or hybrid design in which the conversion apparatus and heat exchanger may be at least partially integrated, or the conversion apparatus and the heat exchanger may be separate units which may be coupled with and/or in thermal communication with one another.

In certain embodiments, the conversion apparatus may comprise an inlet in communication with the cryogenic liquid source and configured for receiving cryogenic liquid from the cryogenic liquid source; a thermal exchange portion configured for thermally contacting received cryogenic liquid with ambient heat to convert the cryogenic liquid into a compressed gas, a high velocity gas flow, or any combinations thereof; an expansion portion configured for expanding the compressed gas, high velocity gas flow, or any combinations thereof by transitioning the compressed gas, high velocity gas flow, or any combinations thereof, from a high pressure to a lower pressure so as to provide an expanded gas; and an outlet for the expanded gas. In certain embodiments, the outlet may lead to ambient air, for example.

In certain embodiments, the thermal exchange portion may comprise a structure allowing for heat exchange, such that ambient heat may be absorbed by cryogenic liquid in the thermal exchange portion, providing the latent heat of vaporization to the cryogenic liquid such that the cryogenic liquid is converted to a compressed gas, high velocity gas flow, or both. In certain embodiments, the cryogenic liquid may be thermally contacted such that it may absorb ambient heat (such as ambient heat from the volume or structure, or a ventilation air being supplied to the volume or structure, for example), providing the latent heat of vaporization to the cryogenic liquid so as to produce the compressed gas, or high velocity gas flow, or expanded gas (which may be at high velocity), or any combinations thereof. In certain embodiments, the ambient heat at the thermal exchange portion may be ambient heat from ambient air or ventilation air of the heat exchanger. In certain embodiments, the thermal exchange portion may comprise at least one surface across which heat may be transferred from the ambient surroundings and/or from the volume or structure, or a ventilation air being supplied to the volume or structure, and into the cryogenic liquid and/or the forming compressed gas and/or high velocity gas flow. In certain embodiments, the thermal exchange portion may further comprise a tank or reservoir for collecting the produced compressed gas and/or high velocity gas flow.

In certain embodiments, the expansion portion may comprise a structure for expanding the compressed gas and/or high velocity gas flow from the thermal exchange portion, wherein the compressed gas and/or high velocity gas flow may be expanded by transitioning the compressed gas and/or high velocity gas flow from a high pressure to a lower pressure. In certain embodiments, the expansion portion of the conversion apparatus may comprise a nozzle or orifice, and the expansion portion of the conversion apparatus may be configured for expanding the compressed gas and/or high velocity gas flow by transitioning the compressed gas and/or high velocity gas flow from a high pressure to a lower pressure by expanding the high pressure compressed gas and/or high velocity gas flow through the nozzle or throttling the high pressure compressed gas and/or high velocity gas flow through the orifice, which may provide cooling to the expanded gas and/or the ambient air or ventilation air of the volume or structure. In certain embodiments, the lower pressure may be at or near ambient pressure at the completion of the process.

In certain embodiments of the systems as described herein, the conversion apparatus may be configured for thermally contacting received cryogenic liquid with ambient heat such that the compressed gas and/or high velocity gas flow reaches a temperature at or near ambient temperature prior to expanding the compressed gas and/or high velocity gas flow at the expansion portion, or while expanding the compressed gas and/or high velocity gas flow at the expansion portion.

In certain embodiments, the heat exchanger may comprise an inlet for receiving ambient air or ventilation air of the volume or structure; a heat exchange portion configured for thermally contacting received ambient air or ventilation air of the volume or structure with any one or more of the cryogenic liquid, the compressed gas, the expanded gas, or any combinations thereof, of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure; and an outlet for cooled ambient air or ventilation air of the volume or structure.

In certain embodiments, the heat exchange portion may comprise a structure configured for thermally contacting received ambient air or ventilation air of the volume or structure with any one or more of the cryogenic liquid, the compressed gas, and/or high velocity gas flow, the expanded gas, or any combinations thereof, of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure. In certain embodiments, the heat exchange portion may be configured to place any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, in thermal contact with the ambient air or ventilation air of the volume or structure, the ambient air or ventilation air being comparatively warmer than the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, such that heat may transfer from the ambient air or ventilation air to the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or combinations thereof, resulting in cooling of the ambient air or ventilation air of the volume or structure. In certain embodiments, the heat exchange portion may be structured to provide for heat exchange without mixing of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with the ambient air or ventilation air (for example, the thermal contact may involve heat transfer across a barrier of the heat exchange portion such as via countercurrent flow in a heat exchanger, for example). In certain embodiments, the heat exchange portion may be structured to perform heat exchange by mixing the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with the ambient air or ventilation air (for example, a stream of relatively cold cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof may be introduced into the ambient air or ventilation air to provide cooling thereto). In certain embodiments, a portion of the heat exchange by the heat exchange portion may be performed without mixing, and a portion of the heat exchange by the heat exchange portion may be performed with mixing.

In certain embodiments, the heat exchanger may be configured for thermally contacting the expanded gas with the ambient air or ventilation air such that the expanded gas absorbs heat from the ambient air or ventilation air and the expanded gas reaches a temperature at or near ambient temperature during and/or after expanding the compressed gas and/or high velocity gas flow at the expansion portion.

In another embodiment of the systems as described herein, the heat exchanger may be a countercurrent flow-type heat exchanger in which any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, and the ambient air or ventilation air of the volume or structure are thermally contacted via a countercurrent flow.

In certain embodiments, the conversion apparatus and the heat exchanger may be a combined or hybrid design in which the conversion apparatus and heat exchanger may be at least partially integrated, or the conversion apparatus and the heat exchanger may be separate units which may be coupled with and/or in thermal communication with one another.

In certain embodiments, the systems as described herein may further provide for electricity generation. In certain embodiments, the systems as described herein may provide for cogeneration of cooling/refrigeration and electricity.

Accordingly, in certain embodiments, systems as described herein may comprise: a turbine, the turbine configured for receiving at least a portion of the compressed gas and/or the high velocity gas flow and/or expanded gas of the conversion apparatus there through, imparting rotational energy to the turbine; and a generator coupled with the turbine, the generator configured for converting rotational energy from the turbine to electricity, thereby providing cogeneration of refrigeration and electricity.

In certain embodiments, a turbine may be used, or an expansion valve may be used, and the turbine may, in certain embodiments, be a mixed flow turbine which may, in certain embodiments, accept some liquid particles.

In certain embodiments, the turbine may be configured for receiving compressed gas and/or high velocity gas flow and/or expanded gas from the conversion apparatus during or after expansion of the compressed gas and/or high velocity gas flow by the expansion portion. In certain embodiments, the turbine may be configured for receiving expanded gas (which may be at a high velocity) from the conversion apparatus via the outlet for expanded gas.

In certain embodiments, systems as described herein may further comprise: a cryogenic liquid generator configured for using at least a portion of the generated electricity to generate more cryogenic liquid and/or compressed gas.

In another embodiment, systems as described herein may further comprise: a mixing portion configured for mixing at least a portion of the cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, from the cryogenic liquid source and/or conversion apparatus and/or turbine with ambient air or ventilation air from the heat exchanger, cooling the ambient air or ventilation air and/or providing supplemental ambient air or ventilation air for the volume or structure.

In certain embodiments where cryogenic liquid may be mixed with the ambient air or ventilation air to provide cooled and/or supplemented air, the cryogenic liquid may comprise nitrogen and oxygen, which may be mixed to provide a suitable breathable air (which may typically be a minimum 19.5% oxygen in Canadian workplaces, for example).

In certain embodiments, the mixing portion may comprise generally any suitable structure (e.g. a chamber, duct, channel, or other structure) which may receive the cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, and the ambient air or ventilation air (which may be via the same or separate inlet(s)), and allow for mixing of the cryogenic liquid, compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, and the ambient air or ventilation air therein. In certain embodiments, the mixing portion may comprise a ventilation duct suppling ambient air or ventilation air to the volume or structure (such as an underground mine, for example). In certain embodiments, the mixing portion may comprise an inlet for receiving compressed gas, high velocity gas flow, and/or expanded gas from the outlet for expanded gas and/or from the turbine, an inlet for receiving ambient air or ventilation air from the heat exchanger, and an outlet for outputting cooled and/or supplemented ambient air or ventilation air for the volume or structure.

In certain embodiments of the systems as described herein, the volume or structure may comprise an underground volume or structure. In certain embodiments, the volume or structure may comprise an underground mine, or portion thereof.

In certain embodiments of the systems as described herein, the cryogenic liquid may comprise liquid air.

In certain embodiments of the systems as described herein, the system may be configured for providing on-demand cooling to the volume or structure; or to provide a pulsed cooling to the volume or structure in which a temperature of the volume or structure may be maintained within a range defined by an upper and lower temperature limit through periodic or intermittent cooling at regular or irregular intervals; or any combination thereof.

In certain embodiments of the systems as described herein, the system may be configured with a fan for supplying the ambient air or ventilation air to the heat exchanger inlet. In certain embodiments, the fan may be independently powered, or at least partially powered by rotation of the turbine and/or electricity from the generator.

In another embodiment of the systems described herein, there is provided a system for cooling a volume or structure, said system comprising: a cryogenic liquid source; and a conversion apparatus integrated with a heat exchanger; wherein the conversion apparatus comprises: an inlet in communication with the cryogenic liquid source and configured for receiving cryogenic liquid from the cryogenic liquid source; a thermal exchange portion configured for thermally contacting received cryogenic liquid with ambient heat to convert the cryogenic liquid into a compressed gas, a high velocity gas, or both; an expansion portion configured for expanding the compressed gas, or high velocity gas flow, or both, by transitioning the compressed gas or high velocity gas flow, or both from a high pressure to a lower pressure so as to provide an expanded gas; and an outlet for the expanded gas; and wherein the heat exchanger comprises: an inlet for receiving ambient air or ventilation air of the volume or structure; a heat exchange portion configured for thermally contacting received ambient air or ventilation air of the volume or structure with the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, passing through the thermal exchange portion and the expansion portion of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure; and an outlet for cooled ambient air or ventilation air of the volume or structure.

In another embodiment of the above system, the system may comprise: a turbine, the turbine configured for receiving at least a portion of the compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, from the outlet of the conversion apparatus therethrough, imparting rotational energy to the turbine; and a generator coupled with the turbine, the generator configured for converting rotational energy from the turbine to electricity, thereby providing cogeneration of refrigeration and electricity.

In certain embodiments, expansion of the cryogenic liquid may be used to produce power. By way of example, in certain embodiments, about 1 litre of liquid may expand to about 700 liters or more depending on ambient temperatures. By way of example, typical lowgrade heat at only about boiling water temperatures may be used to raise the expansion power by further expansion, as such low grade heat is often available but may be difficult to use in other applications, and such low grade heat may become high grade heat due to the temperature difference, which may be about 80 k to 300 k, for example, for ambient temperatures and about 80 k to 400 k for lowgrade heat. Such temperature differences may, in certain embodiments, be significant for waste heat situations, which may otherwise often be wasted.

In still another embodiment of the above systems, the system may be configured with a fan for supplying the ambient air or ventilation air to the heat exchanger inlet, the fan being powered by rotational energy of the turbine and/or electricity from the generator.

In still another embodiment of the systems described herein, cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas exiting the outlet of the conversion apparatus and/or exiting the cryogenic liquid source and/or exiting the turbine may be mixed with the cooled ambient air or ventilation air exiting the outlet of the heat exchanger, or other ambient air or ventilation air, further cooling the ambient air or ventilation air and/or providing supplemental ambient air or ventilation air for the volume or structure.

An example of a system for cooling a volume or structure as described herein is depicted in

Figure 7. In the depicted embodiment, the system comprises a cryogenic liquid source (1)

(shown containing a cryogenic liquid (2)); and a conversion apparatus (3) integrated with a heat exchanger (4). The conversion apparatus (3) comprises: an inlet (5) in communication with the cryogenic liquid source and configured for receiving cryogenic liquid (2) from the cryogenic liquid source (1); a thermal exchange portion (6) configured for thermally contacting received cryogenic liquid (2) with ambient heat to convert the cryogenic liquid (2) into a compressed gas, high velocity gas flow, or both; an expansion portion (7) configured for expanding the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, by transitioning the cryogenic liquid, compressed gas, high velocity gas flow, or any combinations thereof, from a high pressure to a lower pressure so as to provide an expanded gas; and an outlet (8) for the expanded gas. In the depicted embodiment, the heat exchanger (4) comprises: an inlet (9) for receiving ambient air or ventilation air (10) of the volume or structure; a heat exchange portion (11) configured for thermally contacting received ambient air or ventilation air (10) of the volume or structure with any one or more of the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, of the conversion apparatus (3) so as to provide cooling to the ambient air or ventilation air (10) of the volume or structure; and an outlet (12) for cooled ambient air or ventilation air (13) of the volume or structure.

The system depicted in Figure 7 further provides for electricity generation via cogeneration of cooling/refrigeration and electricity. Accordingly the system further includes a turbine (14), the turbine configured for receiving at least a portion of the compressed gas and/or high velocity gas flow and/or expanded gas of the conversion apparatus (3) therethrough, imparting rotational energy to the turbine (14); and a generator (15) coupled with the turbine (14), the generator configured for converting rotational energy from the turbine (14) to electricity (16), thereby providing cogeneration of refrigeration and electricity. In the depicted system, the electricity (16) is, or may be, used to power a cryogenic liquid generator (17), to generate and supply additional cryogenic liquid (2) to the system.

In the system embodiment depicted in Figure 7, the system further provides supplementary air for the ambient air or ventilation air. The depicted system includes a mixing portion (18) configured for mixing at least a portion of the compressed gas, high velocity gas flow, expanded gas, or any combinations thereof, from the conversion apparatus (3) (in this example, the expanded gas exiting the turbine (14)) with cooled ambient air or ventilation air (13) from the heat exchanger (4), thereby further cooling the ambient air or ventilation air and/or providing supplemental ambient air or ventilation air for the volume or structure. The mixing portion (18) outputs a cooled and supplemented ambient air or ventilation air (19). The depicted mixing portion (18) includes an inlet (20) for cooled ambient air or ventilation air (13) from the heat exchanger (4), and an inlet (21) for expanded gas exiting the turbine (14), and an outlet (22) for outputting the cooled and supplemented ambient air or ventilation air (19). The cooled and supplemented ambient air or ventilation air (19) is then circulated through the volume or structure (in this example, an underground mine (25)), thereby providing cooling of the underground mine (25). In the depicted example, the system is installed within the underground mine, and the heat exchanger (4) receives ambient air or ventilation air (10) from a ventilation system of the underground mine (in this example, a fan or pump (24) is provided for supplying the ambient air or ventilation air (10) to the heat exchanger (4), the fan or pump (24) being powered at least in part by produced electricity (16)), and the mixing portion (18) is integrated with or otherwise outputs the cooled and supplemented ambient air or ventilation air (19) back to the ventilation system of the underground mine for circulation throughout all or a portion of the mine to provide cooling thereto.

In certain embodiments, where a compressed gas is produced, the compressed gas, or a portion thereof, may be used to power machinery, tools, etc..., and/or to perform other actions, as desired.

In certain embodiments, provided herein are dual-purpose heating/cooling heat exchanger systems using cryogenic liquid as well as upcast/exhaust air to provide heating and/or cooling to downcast air as desired, as well as methods relating thereto. In certain embodiments, a heat exchanger may be used to exchange heat between the downcast air and the upcast/exhaust air prior to the downcast air being supplied to the volume or structure. When the upcast/exhaust air is hotter than the downcast air (as is often the case during the winter months), the downcast air will be heated by the heat exchange. When the upcast/exhaust air is cooler than the downcast air (as may occur in the summer months), the downcast air may be cooled by the heat exchange. It is contemplated that in many instances, the upcast/exhaust air may not be sufficiently cooler than the downcast air to provide desired cooling levels to the volume or structure. In such instances, a cryogenic liquid may be used to provide cooling to the downcast air, either directly or indirectly. In certain embodiments, cryogenic liquid may be converted to a compressed gas, a high velocity gas flow, and/or an expanded gas, which may absorb heat as described hereinabove, and this may be used to directly or indirectly cool the downcast air. Optionally, cooling may be provided by: mixing the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas with the downcast air directly (so long as the cryogenic liquid used is chosen to provide a cooled downcast air that is appropriate for the volume or structure - for example, if workers will be exposed to the downcast air then the cryogenic liquid should be selected to provide a safe and breathable downcast air); or by exchanging heat between the downcast air and the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas (any of which may optionally be mixed with additional air, such as ambient air, if further volume and/or flow is desired), without mixing the downcast air with the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas, optionally using a heat exchanger; or by using the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas to cool upcast/exhaust air (either directly such as by mixing or indirectly such as by heat exchange without mixing) and using the cooled upcast/exhaust air to cool the downcast air via heat exchange between the cooled upcast/exhaust air and the downcast air; or any combinations thereof.

In certain embodiments, there are provided herein methods and systems for adjusting, controlling, or regulating temperature (i.e. providing heating and cooling) of a volume or structure, such as an underground mine, which may utilize cryogenic liquid as well as exhaust ventilation air (e.g. upcast air) from the volume or structure (such as a mine) to adjust the temperature of incoming air (e.g. downcast air) being provided to the volume or structure (such as downcast air or a mine, for example) so as to provide heating and/or cooling to the volume or structure as desired. In certain embodiments, heat exchange may be performed between the exhaust ventilation air and the incoming air being provided to the volume or structure using a heat exchanger to heat or cool the incoming air (depending on whether the exhaust ventilation air is hotter or cooler than the incoming air). In embodiments or examples where the exhaust ventilation air is not used for cooling, or where the exhaust ventilation air is not sufficiently cool to provide a desired level of cooling to the incoming air, then cryogenic liquid may be used to cool the incoming air being provided to the volume or structure (optionally via cooling the exhaust ventilation air), as desired.

Thus, dual purpose heating/cooling methods and systems are provided herein which may be used for both summer and winter months, for example. By using exhaust ventilation air and cryogenic liquid to provide heating/cooling to downcast air as desired, it is contemplated that temperature control may be achieved with desirable efficiency and/or with reduced green house gas emission as compared to certain conventional approaches such as those that bum fossil fuels, and that systems and methods as described herein may be for use year-round including both winter and summer months.

In certain embodiments, systems and methods as described herein may be configured to transfer heat from exhaust ventilation air to incoming fresh air through a heat exchanger. In certain embodiments, the two air streams (i.e. the exhaust ventilation air/upcast air, and the incoming fresh air/downcast air) do not mix, rather heat may be exchanged without actually mixing the air streams together. The skilled person having regard to the teachings herein will be aware of a wide variety of different heat exchanger configurations that may be used to transfer heat without mixing of the two air streams. Using such approaches, when the exhaust ventilation air is hotter than the incoming/downcast air (as is often the case particularly in winter months), the incoming/downcast air may be heated in the heat exchanger, which may replace or reduce the conventional use of propane or natural gas burning to heat the downcast air in winter, which may save on or reduce greenhouse gases (GHG). In summer, it is contemplated in certain embodiments that the same heat exchanger may be used to cool the downcast air by using cryogenic liquids to cool the exhaust ventilation airflow (if the exhaust ventilation airflow is not already suitably cool), which may as a result cool the incoming/downcast air in the heat exchanger. In certain embodiments, it is contemplated that the system may be operated at a reduced rate in the case of cooling the air from the upcast shaft - in certain embodiments, for example, the rate may be about 500 m ³ /s in winter and for the cooling the rate may be about 100 to 150 m ³ /s, accordingly it is contemplated that for cooling (such as may be desired in summer), some of the upcast air may be mixed with the cryogenically sourced air to provide a sufficient air flow for the heat exchanger efficiency, this provides the pressure and volume flow via the expanding cryogenic gas and power from the upcast air fan, for example. In certain embodiments where cooling of the downcast air is desired, the temperature of the upcast air may be compared with the temperature of another air source such as ambient air, and the cooler of the two may be selected for use. By way of example, if ambient air is cooler than the upcast air, then systems and methods described herein may be configured to use the cryogenic liquid to cool the ambient air, and to use the cooled ambient air to cool the downcast air, for example.

As will be understood, it is contemplated that in certain embodiments the systems and methods may be operated on the surface, using upcast and downcast air exiting and entering the mine, respectively. In certain embodiments, the cryogenic liquid may be stored and used at the surface for cooling, prior to the downcast air being provided to the volume or structure (such as an underground mine). In certain embodiments, a cryogenic liquid production plant may be provided at the surface, or near the site, or cryogenic liquid may be otherwise transported to the site. As will be understood, in certain embodiments of the systems and methods as described herein, the cryogenic liquid may be used for cooling in a manner which prevents mixing of the cryogenic liquid (and gases produced therefrom) from mixing with the downcast air. Accordingly, it is contemplated that in such embodiments the selection of cryogenic liquid(s) used may be relatively broad, since workers in the mine are prevented from exposure to the cryogenic liquid (and gases produced therefrom) and instead only experience the downcast air which is maintained free of cryogenic liquid (and gases produced therefrom). Accordingly, in such embodiments it is contemplated that a cryogenic liquid such as nitrogen cryogenic liquid may be used, and the resultant nitrogen gas produced from the cryogenic liquid may be vented or otherwise dealt with at the surface (without ever entering the mine) in a manner which does not create a low-oxygen or otherwise dangerous environment. Thus, by avoiding mixing with the downcast air, a relatively cost-effective and readily obtainable cryogenic liquid such as nitrogen cryogenic liquid may be used in such embodiments, for example. The person of skill in the art having regard to the teachings herein will be aware of a variety of precautions, monitoring, and safety measures for ensuring air quality and safety is maintained.

In certain embodiments, it is contemplated that in addition to cooling, the cryogenic liquid or compressed gas, high velocity gas flow, and/or expanded gas derived therefrom may additionally be used for one or more additional purposes on site, such as driving a turbine to create electricity and or powering tools and/or equipment designed to be powered by compressed air, for example. Accordingly, in certain embodiments, cryogenic liquid may be used as an energy source for providing two or more uses such as, but not limited to, providing cooling; providing a compressed gas for powering tools and other equipment operable on compressed air; providing electricity via a turbine; or various combinations thereof. In situations having challenging economics, or in situations where further improvement of economics and/or reduced operating costs are desired, it is contemplated that the cryogenic liquid may be used to provide chilling whilst also being used for one or more of cogenerating electricity (via a turbine, for example); cogenerating compressed air (whilst also generating chilling) that can be used to power tool or vehicle engines (such as Dearman engines, or other) that absorb heat and exhaust clean cool air in an underground setting, for example; or any combinations thereof; thereby increasing benefit from the cryogenic liquid.

As will be understood, in certain embodiments of systems and methods described herein, the same heat exchange unit may be used to provide both cooling in summer and heating in winter, thus reducing the carbon load by reducing propane consumption (often used in conventional heating) by about 90% in certain examples, which may create substantial cost savings and/or reduced emission of greenhouse gases.

In certain embodiments, it is contemplated that integrating cryogenic liquid for more than one purpose (such as chilling, combined with one or more of electricity generation and/or generation of compressed gas usable to power tools/equipment), and/or by combining use of cryogenic liquid and use of upcast air for cooling/heating of downcast air, an economy of scale may be provided allowing for the production costs of the cryogenic liquid(s) to be at least partly offset. In certain embodiments, production costs of the cryogenic liquid(s) may be at least partly offset by the scaling factor of the plant cost (e.g. double the size plant volume output for a 1.4 to 1.5 increase in capex, for example). Then having the large plant, it is contemplated that the amount of product used for operations at the mine may be based on the daily temperatures for the large consumption component - chilling - and may be somewhat the same for the other uses. Therefore, in certain embodiments, it is contemplated that the surplus cryogenic liquid(s) may be available for sale on the open market. Generally, the demand for cryogenic liquids (e.g. argon, oxygen, and nitrogen) may be directly proportional to mass of industrial product - so may be expected to be a straightforward relationship to the GDP. In embodiments employing large scale production, it is contemplated that this may apply to surface operations where mining often already requires oxygen for smelters, but having the larger plant may allow use of the cheaper or by product liquid nitrogen for surface vehicles, for example, since on the surface there is less concern with outside use of nitrogen-based vehicles or tools (unless operating in a confined space or where other potential safety concerns may exist).

In certain embodiments, a heat exchanger (configured for non-mixing airflows) may be used to provide heating in the winter by capturing the heat from the mine air raise (exhaust air), and in the summer chilling may be provided for the hot months by directing liquid nitrogen (or other cryogenic liquid) or a compressed gas, high velocity gas flow, and/or expanded gas obtained therefrom, to mix with some ambient air (or exhaust air, or other air supply) to provide a cold side flow for downcast air or other air intended for cooling a volume or structure.

In another embodiment of any of the above method or methods, the method may further comprise collecting at least a portion of compressed gas derived from the cryogenic liquid, providing a collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In another embodiment of any of the above system or systems, the system may further comprise a compressed gas storage tank configured to collect at least a portion of compressed gas derived from the cryogenic liquid, providing a collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In yet another embodiment there is provided herein a method for controlling or adjusting temperature of a volume or structure, said method comprising: heating a ventilation air being supplied to the volume or structure when the ventilation air temperature is below a desired temperature or temperature range by performing a heat exchange between the ventilation air and exhaust air returning from the volume or structure, the returning exhaust air being hotter than the ventilation air such that the ventilation air is heated by the heat exchange; cooling the ventilation air being supplied to the volume or structure when the ventilation air temperature is above a desired temperature or temperature range by performing a heat exchange between the ventilation air and a cooling stream generated using a cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof, the cooling stream being cooler than the ventilation air such that the ventilation air is cooled by the heat exchange; and supplying the heated or cooled ventilation air to the volume or structure.

In another embodiment of the above method, the step of heating may comprise performing heat exchange between the ventilation air and exhaust air without mixing the ventilation air with the exhaust air.

In still another embodiment of any of the above method or methods, the step of cooling may comprise generating the cooling stream by:

(a) thermally contacting, or mixing, the cryogenic liquid or cold compressed gas, high velocity gas flow, or expanded gas derived from the cryogenic liquid, or any combination thereof, with an ambient air, the exhaust air, or a combination thereof, thereby providing the cooling stream;

(b) converting the cryogenic liquid into a cold compressed gas, high velocity gas flow, or both, wherein the cryogenic liquid absorbs heat to provide the compressed gas, the high velocity gas flow, or both; and, optionally, expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure, providing an expanded gas and absorbing additional heat; and thermally contacting, or mixing, the cryogenic liquid, compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, with an ambient air, the exhaust air, or a combination thereof, such that cooling occurs, thereby providing the cooling stream; or

(c) converting the cryogenic liquid into a cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, and using the cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, as the cooling stream, wherein the cooling stream may optionally further comprise ambient air, the exhaust air, or a combination thereof; or any combinations thereof.

In still another embodiment of any of the above method or methods, the expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure may comprise expanding the high pressure compressed gas, high velocity gas flow, or both, through a nozzle or throttling the high pressure compressed gas, high velocity gas flow, or both, through an orifice, providing cooling. Such approaches for conversion/expansion are already described in detail hereinabove.

In yet another embodiment of any of the above method or methods, the step of cooling may comprise mixing the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with ambient air, with the returning exhaust air, or a combination thereof, to provide the cooling stream; or wherein the step of cooling comprises thermally contacting the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, via non-mixing heat exchange with ambient air, with the returning exhaust air, or a combination thereof, cooling the ambient air, returning exhaust air, or the combination thereof to provide the cooling stream.

In another embodiment of any of the above method or methods, the step of cooling may comprise performing heat exchange between the ventilation air and the cooling stream without mixing the ventilation air with the cooling stream.

In still another embodiment of any of the above method or methods, the heating and cooling steps may be performed using the same heat exchanger.

In yet another embodiment of any of the above method or methods, the method may further comprise generating a compressed gas and/or the high velocity gas flow and/or expanded gas from the cryogenic liquid and passing the compressed gas and/or the high velocity gas flow and/or expanded gas through a turbine, providing rotational energy to the turbine, and generating electricity at a generator coupled with the turbine, thereby providing electricity.

In another embodiment of any of the above method or methods, the method may further comprise collecting at least a portion of compressed gas derived from the cryogenic liquid, providing a collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In still another embodiment of any of the above method or methods, the volume or structure may comprise an underground volume or structure. In yet another embodiment of any of the above method or methods, the volume or structure may comprise an underground mine, or a portion thereof. In another embodiment of any of the above method or methods, the steps of heating and cooling may be performed at the surface. In still another embodiment of any of the above method or methods, the exhaust air may comprise upcast air from a mine, the ventilation air comprises downcast air for the mine, or both.

In still another embodiment of any of the above method or methods, the ventilation air may be cooled via heat exchange when the exhaust air is cooler than the ventilation air, and the step of cooling is used to provide on-demand cooling when the temperature of the untreated exhaust air is not sufficiently cool to maintain the ventilation air at or within the desired temperature or temperature range.

In still another embodiment of any of the above method or methods, the ventilation air is not mixed with the cooling stream, and the cryogenic liquid is or comprises liquid nitrogen.

In yet another embodiment of any of the above method or methods, heat exchange in the cooling and/or heating steps may be performed using a non-mixing air-to-air parallel plate-type heat exchanger, or concentric cylinder heat exchanger as is used for circular shafts.

In another embodiment, there is provided herein a system for controlling or adjusting temperature of a volume or structure, said system comprising: a heat exchange unit comprising a ventilation air input, a ventilation air output, an exhaust air input, an exhaust air output, and a heat exchanger configured to exchange heat to and from the ventilation air; and a cooling unit configured to generate a cooling stream; the system configured for heating a ventilation air being supplied to the volume or structure when the ventilation air temperature is below a desired temperature or temperature range by passing the ventilation air from the ventilation air input, through the heat exchanger, and out the ventilation air output, while passing exhaust air returning from the volume or structure, the returning exhaust air being hotter than the ventilation air, from the exhaust air input, through the heat exchanger, and out the exhaust air output, such that the ventilation air is heated by the heat exchange with the exhaust air in the heat exchange unit; and the system configured for cooling the ventilation air being supplied to the volume or structure when the ventilation air temperature is above a desired temperature or temperature range by passing the ventilation air from the ventilation air input, through the heat exchanger, and out the ventilation air output, while passing a cooling stream, the cooling stream being cooler than the ventilation air, through the heat exchanger (optionally, the cooling stream may be input via the exhaust air input and output via the exhaust air output, or other input(s)/output(s) may be provided), such that the ventilation air is cooled by the heat exchange with the cooling stream; the ventilation air output configured for supplying the ventilation air to the volume or structure.

As will be understood, the heat exchanger may comprise generally any suitable heat exchanger design known to the person of skill in the art having regard to the teachings herein. An example of a heat exchange unit is depicted in Figure 8, comprising a ventilation air input (not visible), a ventilation air output (202), an exhaust air input (200), an exhaust air output (201), and a heat exchanger unit (main section) configured to exchange heat to and from the ventilation air.

In another embodiment of the above system, the cooling unit may comprise a cryogenic liquid- based cooling unit configured to generate the cooling stream using a cryogenic liquid. In still another embodiment of any of the above system or systems, the cryogenic liquid-based cooling unit may comprise a cryogenic liquid storage tank, and a mixing/expansion chamber for generating the cooling stream using a cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof, the cooling stream being cooler than the ventilation air.

In still another embodiment of any of the above system or systems, the system may further comprise a cryogenic liquid generation unit in communication with the cryogenic storage unit. The person of skill in the art having regard to the teachings herein will be aware of a variety of different cryogenic liquid generation units and plants that may be used to provide the cryogenic liquid, Alternatively, cryogenic liquid may be generated elsewhere, and supplied to the storage tank (via pipeline, trucking, or other transport), for example.

In yet another embodiment of any of the above system or systems, the heat exchange unit may be or comprise a non-mixing heat exchanger which exchanges heat between the ventilation air and exhaust air without mixing the ventilation air with the exhaust air.

In another embodiment of any of the above system or systems, the cooling unit may be configured for generating the cooling stream, and the cooling unit may comprise:

(a) a mixing/expansion chamber comprising an input for cryogenic liquid or cold compressed gas, high velocity gas flow, or expanded gas derived from the cryogenic liquid, or any combination thereof, and an input for an ambient air, the exhaust air, or a combination thereof, the mixing/expansion chamber structured to thermally contact, or mix, the ambient air, the exhaust air, or a combination thereof and the cryogenic liquid or cold compressed gas, high velocity gas flow, or expanded gas derived from the cryogenic liquid, thereby providing the cooling stream;

(b) a mixing/expansion chamber comprising an input for cryogenic liquid; a conversion section for converting at least a portion of the input cryogenic liquid into a cold compressed gas, high velocity gas flow, or both, wherein the cryogenic liquid absorbs heat to provide the compressed gas, the high velocity gas flow, or both, and optionally, for expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure, providing an expanded gas and absorbing additional heat; and an input for an ambient air, the exhaust air, or a combination thereof; the mixing/expansion chamber structured to thermally contact, or mix, the cryogenic liquid, compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, with the ambient air, the exhaust air, or the combination thereof, such that cooling occurs, thereby providing the cooling stream; or

(c) a mixing/expansion chamber comprising an input for cryogenic liquid; a conversion section for converting the cryogenic liquid into a cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof; and an output for the cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof, to be used as the cooling stream; wherein the conversion section and/or the output for cold compressed gas, high velocity gas flow, or expanded gas, or any combination thereof optionally further comprises an input for ambient air, the exhaust air, or a combination thereof, such that the output cooling stream additionally comprises ambient air and/or exhaust air; or any combinations thereof.

In still another embodiment of any of the above system or systems, the conversion section may comprise a nozzle or orifice, and expanding the compressed gas, high velocity gas flow, or both, from a high pressure to a lower pressure comprises expanding the high pressure compressed gas, high velocity gas flow, or both, through the nozzle or throttling the high pressure compressed gas, high velocity gas flow, or both, through the orifice, providing cooling.

Examples of conversion sections and mixing/expansion chambers have already been described in detail hereinabove. Figures 5, 12, and 15 provide additional illustrative examples, and are described in detail below.

In still another embodiment of any of the above system or systems, the cooling unit may be configured to mix the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, with ambient air, with the returning exhaust air, or a combination thereof, to provide the cooling stream; or wherein the cooling unit is configured to thermally contact the cryogenic liquid, the compressed gas, the high velocity gas flow, the expanded gas, or any combinations thereof, via non-mixing heat exchange, with ambient air, with the returning exhaust air, or a combination thereof, cooling the ambient air, returning exhaust air, or the combination thereof to provide the cooling stream.

In yet another embodiment of any of the above system or systems, the heat exchange unit may be or comprise a non-mixing heat exchange unit which performs heat exchange between the ventilation air and the cooling stream without mixing the ventilation air with the cooling stream.

In another embodiment of any of the above system or systems, the system may further comprise a turbine configured to receive at least a portion of compressed gas and/or high velocity gas flow and/or expanded gas from the cryogenic liquid, which is passed through the turbine, providing rotational energy to the turbine, and generating electricity at a generator coupled with the turbine, thereby providing electricity.

In yet another embodiment of any of the above system or systems, the system may further comprise a collection unit for collecting and storing at least a portion of compressed gas derived from the cryogenic liquid, the collection unit having an outlet for providing collected compressed gas for use in powering tools, engines, or equipment operable on compressed gas.

In still another embodiment of any of the above system or systems, the volume or structure may comprise an underground volume or structure.

In another embodiment of any of the above system or systems, the volume or structure may comprise an underground mine, or a portion thereof.

In yet another embodiment of any of the above system or systems, the cooling unit and the heat exchange unit may be installed at the surface.

In still another embodiment of any of the above system or systems, the exhaust air may comprise upcast air from a mine, the ventilation air comprises downcast air for the mine, or both.

In yet another embodiment of any of the above system or systems, the ventilation air may be cooled via heat exchange when the exhaust air is cooler than the ventilation air, and the cooling unit may be used to provide on-demand cooling when the temperature of the untreated exhaust air is not sufficiently cool to maintain the ventilation air at or within the desired temperature or temperature range.

In yet another embodiment of any of the above system or systems, the ventilation air is not mixed with the cooling stream, and the cryogenic liquid is or comprises liquid nitrogen.

In another embodiment of any of the above system or systems, the heat exchanger in the heat exchange unit may comprise a non-mixing air-to-air parallel plate-type, concentric cylinder-type, or other suitable geometry, heat exchanger.

In still another embodiment of any of the above system or systems, the cooling unit may comprise a cryogenic liquid-based cooling unit configured to generate the cooling stream using a cryogenic liquid; wherein the cryogenic liquid-based cooling unit may comprise a cryogenic liquid storage tank, and a mixing/expansion chamber for generating the cooling stream using the cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof, the cooling stream being cooler than the ventilation air; and wherein the mixing/expansion chamber may comprise an inlet for ambient air, exhaust air, or a mixture thereof; a cryogenic fluid inlet in the form of a substantially annular tube or ring comprising a plurality of exit ports, or another suitable geometry appropriate for a given situation, for input into the mixing/expansion chamber so as to provide mixing and cooling; and an output for the cooling stream, the outlet being in communication with the heat exchange unit for supplying the cooling stream thereto.

An illustrative example of a cryogenic liquid-based cooling unit is shown in Figures 12 and 15. The depicted example comprises a cryogenic liquid storage tank (207), and a mixing/expansion chamber (208) for generating the cooling stream using the cryogenic liquid or a compressed gas, a high velocity gas flow, or an expanded gas derived from the cryogenic liquid, or any combination thereof. The depicted mixing/expansion chamber (208) comprises an inlet (209) for ambient air, exhaust air, or a mixture thereof; a cryogenic fluid inlet (210) in the form of a substantially annular tube or ring comprising a plurality of exit ports for input into the mixing/expansion chamber so as to provide mixing and cooling; and an output (211) for the cooling stream, the outlet being in communication with the heat exchange unit for supplying the cooling stream thereto. EXAMPLE 1- Hybrid Cryogenic Process and System.

This example describes embodiments of hybrid methods and systems as described herein, wherein the methods and systems provide for both refrigeration and electricity generation. From a cryogenic liquid, a compressed air and refrigeration may be cogenerated, and/or electricity and refrigeration may be cogenerated. In certain embodiments, electricity and/or motive power in the form of engines to operate underground equipment may be provided, while simultaneously producing refrigeration, in a cogeneration system. As part of the methods and systems in this example, a source of cryogenic liquid may be used to freely expand in an ambient ventilation duct, for example, which may absorb heat and may supply a fraction of the ventilation air to a volume or structure such as an underground mine. In certain embodiments, these systems may collectively operate from a single source of cryogenic liquid to provide a mine service and refrigeration (such as mine chilling) simultaneously.

In certain embodiments of the methods and systems of this example, the cryogenic liquid may absorb the latent heat of vaporisation from the ambient air to become a very cold gas which may be a compressed gas. In certain embodiments, the very cold gas may be mixed with the ambient air, absorbing an amount of heat so as to raise its temperature to a final temperature of the resulting mixture, the final temperature of the resulting mixture being lower than the initial temperature of the ambient air. In certain embodiments, a fraction of the air demand from an underground mine may be supplied by gas from the cryogenic liquid (for example, liquid air), which may reduce the demand for air from the surface, which may lead to savings in energy, for example. In certain embodiments, the composition of the mine air may not change substantially, except for the addition of the fraction of ultrapure air upon the expansion of the liquid air to the gaseous state, and consequently contaminant concentrations may accordingly be further diluted.

By way of example and for illustrative purposes, in certain embodiments, it is contemplated that the expansion factor of about 1 litre of the liquid may become about 750 litres of gaseous air, depending on temperatures and pressures (i.e. atmospheric conditions) of the ambient air into which the liquid expands. In certain embodiments, the use of liquid air may be environmentally clean (zero or near zero carbon emissions). In certain embodiments, where the system is grid connected, electrical energy may be used to produce the cryogenic liquid, and emissions may depend on the composition of the grid generation such that the actual environmental footprint may be a jurisdictional determination. In remote or off-grid implementations, it is contemplated that all or at least a portion of the power may be sourced from renewable energy systems if desired.

As part of systems and methods described in this example, cryogenic liquid may become a store of energy, which can be used to increase the reliability, availability and/or penetration factor of the renewable energy systems.

In certain embodiments, it is contemplated that hybrid systems and methods as described herein may eliminate or reduce diesel usage for remote community power and/or the impact of transporting large amounts of fossil fuels of long distances or obviate the need for transmission lines.

A series of sample calculations used in developing systems and methods as described in this example are discussed below. Sample calculations:

• Let the air demand for underground usage be 100 m ³ ;

• Let the surface temperature be 30°C;

• Let the target temperature of the underground workings be 25°C;

• The depth at which the release of the liquid air is 2500 m in this sample calculation; and

• Relative humidity of surface air is 75% in this sample calculation;

QL = m ₁ L The latent heat of vapourisation of liquid air phase transition to a gas 205 kJ/kg

Q ₁ = m ₁ C ₁ T, The heat in the liquid cryogenic air

Q ₂ - m ₂ C ₁ T _a The heat contained in ambient air a. The air sourced from the surface and delivered to the mine depth warms while descending according to the adiabatic lapse rate of 9.8 °C per 1000 meters and for wet adiabatic lapse rate at 4.6 °C per 1000 M. For a depth of 2500 meters, the dry air temperature increase is 24.5 °C; however depending on the shaft conditions (which may lie somewhere between perfectly dry and perfectly wet) the temperature increase could be typically 6 °C per 1000 meters so the temperature increase may be 15 to 24.5 °C. Let the temperature increase be 24.5 °C for the purpose of this sample calculation. b. Based on the above, the air arrives at depth at a temperature of 59.5 °C in this example and it is desired that the air be cooled to 25 °C. c. Assume a density for air at the surface of 1.2 kg/m ³ and 1.47 kg/m ³ at 2500 m depth. d. The temperature difference between the target temperature underground and the arrival temperature underground is 29.5 K in this sample calculation. e. Using 1.005 kJ/kg K as the specific heat capacity, f. The amount of heat to be removed is

(92.19 m ³ )(1.47 kg/m ³ )(1.005 kJ/kg K)( 29.5 K) = 4.04 MW g. The volume at depth is reduced to 92.19 m ³ because the amount of air created by releasing the 9.36 kg liquid air into the mine results in 7.803 m ³ . h. As a result of the reduced airflow demanded, the fan power at surface main fans may be reduced to 78.37% of the initial demand in this sample calculation due to the cubic relationship between the flow and the power.

Figure 1 shows (a) a computational fluid dynamics analysis of a shaft in total length of 500 m, but in this figure the initial section where the cryogenic liquids are used to cool the airflow. A concentric plate heat exchanger is placed in the flow where the cryogenic liquids exchange the latent heat of vapourisation and undergo an initial expansion. The flow and apparatus are surrounded by granite maintained at a constant temperature of 325 K to simulate an actual mine ventilation situation where heat would be transferred to the air from the host rock. The initial cooling in this case is determined by the properties of temperature, pressure and flow rate at the exit of this stage. The higher density low temperature air is emitted into the ventilation flow and mixes due to turbulence to cause the ambient airflow to cool further. In this case the inlet airflow is 235 kg/s at 319 K. The cryogenic liquid flow is 24 kg/s at an initial temperature of 78 K. Consequently the heat absorbed to cause the change of state from liquid to gas and for the further expansion from a very cold higher density gas to ambient temperature reduces the temperature of the entire flow to a value less than the initial ambient temperature. In Figure 1(b) the results of the simulation are shown, based on the model described in Figure 1, and are depicted in Figure 2, where the red is the high temperature and blue is the lower temperature as caused by the introduction of the cryogenic liquids into the ambient ventilation flow.

Figure 2 shows the average temperature of the entire volume of air contained in the 500 m length of the simulated ventilation flow. This example demonstrates that the cooling in this example is delivered at the velocity of the airflow or virtually instantaneously. In figure 2, results are shown (over a 500 meter shaft) of the cooling created by introducing cryogenic liquid air and the rapid response time, which may be correlated to the air flow velocity. This provides a demonstration of a cooling on demand concept.

Compressed air may be produced from cryogenic liquid in this example. Due to the previously discussed expansion factor (see above) the cryogenic liquids when placed in a confined pressure rated container and allowed to absorb heat may be capable of producing compressed air at a wide range of pressures. Compressed air may be readily produced by simply confining the liquid and allowing it to reach ambient temperature, this is a consequence of the expansion factor and may be readily calculated by use of the ideal gas laws (PV = nRT). The production of compressed air will absorb ambient heat from the surroundings of the underground environment in this example, creating a cogeneration system of compressed air and refrigeration. The absorption of heat in the production of compressed air may be desirable in the present systems and methods; and may be distinguished from traditional underground compressors, in which traditional underground compressors typically reject heat from the compressed air. Depending on the rating of the pressure vessel and the amount of liquid inserted, the pressures obtained with the present systems may be very high, if desired. High pressures may be used to provide further mine cooling via the Joule Thompson effect. Expansion of the high pressure gas through a nozzle, for example, may create cooling. By using this method, it is contemplated that in certain embodiments the overall consumption of the liquid air for chilling may be reduced.

In certain embodiments of systems and methods described herein, a first stage of chilling may be achieved by absorption of the latent heat of vapourisation and the heat absorbed during the expansion of the gas from cryogenic temperatures to ambient temperatures, and a second stage of chilling may be created by the release of the gas in a free expansion from a high pressure to the ambient pressure in the underground environment, for example.

A series of sample calculations used in developing systems and methods as described in this example are discussed below. Sample calculations:

A typical 5000 ft3/min compressed air service for a mine would demand 250 tonnes/day of liquid air in a steady state configuration; this may provide 1.2 MWr of refrigeration simultaneously.

In figure 3 a liquid air storage tank is shown with a connection to the pressure vessel via control valves. The operation is controlled by set points of pressure in the pressure tank whereby at the low pressure a signal is interpreted by a proportional integral derivative or simple predetermined low and high pressures or other control system to maintain the pressure and demand for pressure flow by continuously or intermittently injecting liquid air into the pressure tank. In Figure 3, a compressed air system depicted in which a cryogenic liquid (e.g. liquid air) storage units is depicted, operating at relatively low pressure, which is in communication (controlled by one or more flow control valves) with a compressed air storage unit, and the cryogenic liquid is flowed to the compressed air storage unit, transforming to compressed gas that is stored in the compressed air storage unit until the compressed gas is sent to services for further use.

It is additionally contemplated in these system and method examples that in certain embodiments, electricity storage may be provided as a means of providing refrigeration to an underground environment. A low pressure storage tank, expansion turbines, and generators underground may be placed underground. Electricity may be produced by capturing the power created during the expansion of the cryogenic liquid to provide rotational energy to a turbine, which may then rotate an electrical generator. The expansion of the cryogenic liquid to a gas through a turbine may absorb the latent heat of vapourisation and the heat absorbed during the expansion of the gas from cryogenic temperatures to the ambient underground temperatures, which may provide for a significant amount of heat being removed from the underground environment. In certain embodiments, it is contemplated that geothermal energy from deeper in the mine may be used to create an electricity production system with a higher round trip efficiency.

In certain embodiments, methods and systems of this example may produce refrigeration and electricity simultaneously - in a cogeneration system. This may be distinguishing over traditional approaches, such as other chilling systems that may reject all of the heat removed from the airflow entering the workings thereby demanding an escape route for the high temperature air that carries the heat from the chiller of the traditional system (such as a bulk air chiller located underground) that may easily be in excess of 55 °C which may present a danger to a worker that may inadvertently encounter the hot air, and other chilling systems that may use a cold water or ice flow to the underground workings where heat exchangers or spray networks may be used to warm up the water flow in order that the heat be carried back to the surface.

In the present systems and methods of this example, in certain embodiments, the liquid air may expand to a gas and may exit through the regular ventilation system, and therefore there may be no return circuit as may be found in other liquid chilling systems.

In Figure 4, a description/depiction of an embodiment of a cryogenic liquefaction plant is shown. During the liquefaction of the air the heat expelled may be stored for other uses such as heating the inlet ventilation air in winter. During expansion of the liquid air to produce power as the expanding gas is routed through a turbine there cold may be stored for further efficiency of producing liquid air; however, in this embodiment the electrical generation system is placed underground such that heat is absorbed from the ambient ventilation air. Storage of the liquid air may be an energy storage vector such that the expansion may provide power. In certain embodiments, a surface storage facility may be connected to the underground via standard cryogenic piping, for example, and subsurface storage facilities are also contemplated. In Figure

4, an example of an underground electrical power and chilling system is depicted. The system includes a liquid air storage unit (which may be underground, or may be at the surface and connected to a transfer line for sending the liquid air underground).

As part of this example, a prototype system was built to demonstrate electrical power generation and chilling simultaneously. This testing supports feasibility of the system and also supports that due to the extremely cold temperatures of the cryogenic liquids, a pulsed chilling configuration may be used, and/or a chilling on demand configuration may be used which may be capable of meeting environmental and/or operational temperature changes (see also figure 2). In certain embodiments, the system may be used in a pulsed mode where the cold temperatures of the system may be able to continue chilling after the system cryogenic flow is stopped. This may provide a benefit over traditional mine chilling systems to not only respond virtually instantaneously to temperature changes, but also to pulse a wave of cool - let the temperature increase slightly - and then provide a further pulse. It is contemplated that in certain embodiments, such configuration may reduce the costs of chilling and/or may provide a more consistent control over underground temperatures.

The prototype system used for this example is depicted in Figure 5. The configuration depicted in Figure 5 represents a preferred embodiment, producing both chilling and electricity. In Figure

5, the depicted prototype system for cooling a volume or structure comprises: a cryogenic liquid source (liquid cryogen at -196°C); and a conversion apparatus integrated with a heat exchanger. The conversion apparatus comprises: an inlet in communication with the cryogenic liquid source and configured for receiving cryogenic liquid from the cryogenic liquid source; a combined thermal exchange/expansion portion configured for thermally contacting received cryogenic liquid with ambient heat to convert the cryogenic liquid into a high velocity gas flow so as to provide an expanded gas (at high velocity); and an outlet for the expanded gas. The heat exchanger comprises: an inlet for receiving ambient air or ventilation air of the volume or structure; a heat exchange portion configured for thermally contacting received ambient air or ventilation air of the volume or structure with the cryogenic liquid, the high velocity gas flow, and the expanded gas passing through the combined thermal exchange/expansion portion of the conversion apparatus so as to provide cooling to the ambient air or ventilation air of the volume or structure; and an outlet for cooled ambient air or ventilation air of the volume or structure.

In the prototype system depicted in Figure 5, the thermal exchange portion and expansion portion of the conversion apparatus are integrated/combined, such that as the cryogenic liquid flows from an input end of the conversion apparatus toward an output end of the conversion apparatus, the cryogenic liquid is warmed by absorbing heat (converting the cryogenic liquid to a compressed gas flowing at high velocity toward the output end of the conversion apparatus), while the compressed gas is simultaneously being expanded as the gas travels toward the output end of the conversion apparatus, such that it is expanded gas which exits the output end of the conversion apparatus. In the depicted prototype, the compressed gas is not actually isolated or accumulated by the system. Further, the conversion apparatus of the depicted system is integrated with the heat exchanger, which is a heat exchanger having a countercurrent flow configuration. Ventilation air from a ventilation air duct is introduced into the heat exchanger by a fan or pump, and the ventilation air flows countercurrent with the cryogenic liquid/compressed gas/high velocity gas flow/expanded gas passing through the conversion apparatus such that heat is transferred from the ventilation air to the cryogenic liquid/compressed gas/high velocity gas flow/expanded gas across a surface separating the ventilation air from the cryogenic liquid/compressed gas/high velocity gas flow/expanded gas. Ventilation air exiting the heat exchanger is thus cooled, and expanded gas exiting the conversion apparatus is warmed. In the depicted system, there is a pressure gradient within the conversion apparatus such that pressure is higher toward the input end of the conversion apparatus and pressure is comparatively lower toward the output end of the conversion apparatus. The expanded gas exits the provided outlet, and passes through a turbine causing rotation thereof, which powers a generator to produce electricity. The expanded gas exiting the turbine is then mixed with the cooled ventilation air exiting the heat exchanger, further cooling the ventilation air and/or providing supplemental ventilation air for the underground mine. Generated electricity is used to power, at least in part, the fan or pump to introduce additional ventilation air to the heat exchanger. EXAMPLE 2- Dual Purpose (Cooling and Heating) Heat Exchanger Systems Using Cryogenic Liquid and Upcast/Exhaust Air to Adjust Temperature of Downcast Air.

This example describes embodiments of dual-purpose heating/cooling heat exchanger systems using cryogenic liquid as well as upcast/exhaust air to provide heating and/or cooling to downcast air as desired, as well as methods relating thereto. In certain embodiments, a heat exchanger may be used to exchange heat between the downcast air and the upcast/exhaust air prior to the downcast air being supplied to the volume or structure. When the upcast/exhaust air is hotter than the downcast air (as is often the case during the winter months), the downcast air will be heated by the heat exchange. When the upcast/exhaust air is cooler than the downcast air (as may occur in the summer months), the downcast air may be cooled by the heat exchange. It is contemplated that in many instances, the upcast/exhaust air may not be sufficiently cooler than the downcast air to provide desired cooling levels to the volume or structure. In such instances, a cryogenic liquid may be used to provide cooling to the downcast air, either directly or indirectly. In certain embodiments, cryogenic liquid may be converted to a compressed gas, a high velocity gas flow, and/or an expanded gas, which may absorb heat as described hereinabove, and this may be used to directly or indirectly cool the downcast air. Optionally, cooling may be provided by: mixing the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas with the downcast air directly (so long as the cryogenic liquid used is chosen to provide a cooled downcast air that is appropriate for the volume or structure - for example, if workers will be exposed to the downcast air then the cryogenic liquid should be selected to provide a safe and breathable downcast air); or by exchanging heat between the downcast air and the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas (any of which may optionally be mixed with additional air, such as ambient air, if further volume and/or flow is desired), without mixing the downcast air with the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas, optionally using a heat exchanger; or by using the cryogenic liquid, compressed gas, high velocity gas flow, and/or expanded gas to cool upcast/exhaust air (either directly such as by mixing or indirectly such as by heat exchange without mixing) and using the cooled upcast/exhaust air to cool the downcast air via heat exchange between the cooled upcast/exhaust air and the downcast air; or any combinations thereof. In certain embodiments, there are provided herein methods and systems for adjusting, controlling, or regulating temperature (i.e. providing heating and cooling) of a volume or structure, such as an underground mine, which may utilize cryogenic liquid as well as exhaust ventilation air (e.g. upcast air) from the volume or structure (such as a mine) to adjust the temperature of incoming air (e.g. downcast air) being provided to the volume or structure (such as downcast air or a mine, for example) so as to provide heating and/or cooling to the volume or structure as desired. In certain embodiments, heat exchange may be performed between the exhaust ventilation air and the incoming air being provided to the volume or structure using a heat exchanger to heat or cool the incoming air (depending on whether the exhaust ventilation air is hotter or cooler than the incoming air). In embodiments or examples where the exhaust ventilation air is not used for cooling, or where the exhaust ventilation air is not sufficiently cool to provide a desired level of cooling to the incoming air, then cryogenic liquid may be used to cool the incoming air being provided to the volume or structure (optionally via cooling the exhaust ventilation air), as desired.

Thus, dual purpose heating/cooling methods and systems are provided herein which may be used for both summer and winter months, for example. By using exhaust ventilation air and cryogenic liquid to provide heating/cooling to downcast air as desired, it is contemplated that temperature control may be achieved with desirable efficiency and/or with reduced green house gas emission as compared to certain conventional approaches such as those that bum fossil fuels, and that systems and methods as described herein may be for use year-round including both winter and summer months.

In certain embodiments, systems and methods as described herein may be configured to transfer heat from exhaust ventilation air to incoming fresh air through a heat exchanger. In certain embodiments, the two air streams (i.e. the exhaust ventilation air/upcast air, and the incoming fresh air/downcast air) do not mix, rather heat may be exchanged without actually mixing the air streams together. The skilled person having regard to the teachings herein will be aware of a wide variety of different heat exchanger configurations that may be used to transfer heat without mixing of the two air streams. Using such approaches, when the exhaust ventilation air is hotter than the incoming/downcast air (as is often the case particularly in winter months), the incoming/downcast air may be heated in the heat exchanger, which may replace or reduce the conventional use of propane or natural gas burning to heat the downcast air in winter, which may save on or reduce greenhouse gases (GHG). In summer, it is contemplated in certain embodiments that the same heat exchanger may be used to cool the downcast air by using cryogenic liquids to cool the exhaust ventilation airflow (if the exhaust ventilation airflow is not already suitably cool), which may as a result cool the incoming/downcast air in the heat exchanger. In certain embodiments, it is contemplated that the system may be operated at a reduced rate in the case of cooling the air from the upcast shaft - in certain embodiments, for example, the rate may be about 500 m ³ /s in winter and for the cooling the rate may be about 100 to 150 m ³ /s, accordingly it is contemplated that for cooling (such as may be desired in summer), some of the upcast air may be mixed with the cryogenically sourced air to provide a sufficient air flow for the heat exchanger efficiency, this may provide the pressure and volume flow via the expanding cryogenic gas and power from the upcast air fan.

In certain embodiments where cooling of the downcast air is desired, the temperature of the upcast air may be compared with the temperature of another air source such as ambient air, and the cooler of the two may be selected for use. By way of example, if ambient air is cooler than the upcast air, then systems and methods described herein may be configured to use the cryogenic liquid to cool the ambient air, and to use the cooled ambient air to cool the downcast air, for example.

As will be understood, it is contemplated that in certain embodiments the systems and methods may be operated on the surface, using upcast and downcast air exiting and entering the mine, respectively. In certain embodiments, the cryogenic liquid may be stored and used at the surface for cooling, prior to the downcast air being provided to the volume or structure (such as an underground mine). As will be understood, in certain embodiments of the systems and methods as described herein, the cryogenic liquid may be used for cooling in a manner which prevents mixing of the cryogenic liquid (and gases produced therefrom) from mixing with the downcast air. Accordingly, it is contemplated that in such embodiments the selection of cryogenic liquid(s) used may be relatively broad, since workers in the mine are prevented from exposure to the cryogenic liquid (and gases produced therefrom) and instead only experience the downcast air which is maintained free of cryogenic liquid (and gases produced therefrom). Accordingly, in such embodiments it is contemplated that a cryogenic liquid such as nitrogen cryogenic liquid may be used, and the resultant nitrogen gas produced from the cryogenic liquid may be vented or otherwise dealt with at the surface (without ever entering the mine) in a manner which does not create a low-oxygen or otherwise dangerous environment. Thus, by avoiding mixing with the downcast air, a relatively cost-effective and readily obtainable cryogenic liquid such as nitrogen cryogenic liquid may be used in such embodiments, for example. The person of skill in the art having regard to the teachings herein will be aware of a variety of precautions, monitoring, and safety measures for ensuring air quality and safety is maintained.

In certain embodiments, it is contemplated that in addition to cooling, the cryogenic liquid or compressed gas, high velocity gas flow, and/or expanded gas derived therefrom may additionally be used for one or more additional purposes on site, such as driving a turbine to create electricity and or powering tools and/or equipment designed to be powered by compressed air, for example. Accordingly, in certain embodiments, cryogenic liquid may be used as an energy source for providing two or more uses such as, but not limited to, providing cooling; providing a compressed gas for powering tools and other equipment operable on compressed air; providing electricity via a turbine; or various combinations thereof. In situations having challenging economics, or in situations where further improvement of economics and/or reduced operating costs are desired, it is contemplated that the cryogenic liquid may be used to provide chilling whilst also being used for one or more of cogenerating electricity (via a turbine, for example); cogenerating compressed air (whilst also generating chilling) that can be used to power tool or vehicle engines (such as Dearman engines, or other) that absorb heat and exhaust clean cool air in an underground setting, for example; or any combinations thereof; thereby increasing benefit from the cryogenic liquid.

As will be understood, in certain embodiments of systems and methods described herein, the same heat exchange unit may be used to provide both cooling in summer and heating in winter, thus reducing the carbon load by reducing propane consumption (often used in conventional heating) by about 90% in certain examples, which may create substantial cost savings and/or reduced emission of greenhouse gases. In certain embodiments, it is contemplated that integrating cryogenic liquid for more than one purpose (such as chilling, combined with one or more of electricity generation and/or generation of compressed gas usable to power tools/equipment), and/or by combining use of cryogenic liquid and use of upcast air for cooling/heating of downcast air, an economy of scale may be provided allowing for the production costs of the cryogenic liquid(s) to be at least partly offset. In certain embodiments, production costs of the cryogenic liquid(s) may be at least partly offset by the scaling factor of the plant cost (e.g. double the size plant volume output for a 1.4 to 1.5 increase in capex, for example). Then having the large plant, it is contemplated that the amount of product used for operations at the mine may be based on the daily temperatures for the large consumption component - chilling - and may be somewhat the same for the other uses. Therefore, in certain embodiments, it is contemplated that the surplus cryogenic liquid(s) may be available for sale on the open market. Generally, the demand for cryogenic liquids (e.g. argon, oxygen, and nitrogen) may be directly proportional to mass of industrial product - so may be expected to be a straightforward relationship to the GDP. In embodiments employing large scale production, it is contemplated that this may apply to surface operations where mining often already requires oxygen for smelters, but having the larger plant may allow use of the cheaper or by product liquid nitrogen for surface vehicles, for example, since on the surface there is less concern with outside use of nitrogen-based vehicles or tools (unless operating in a confined space or where other potential safety concerns may exist).

In certain embodiments, a heat exchanger (configured for non-mixing airflows) may be used to provide heating in the winter by capturing the heat from the mine air raise (exhaust air), and in the summer chilling may be provided for the hot months by directing liquid nitrogen (or other cryogenic liquid) or a compressed gas, high velocity gas flow, and/or expanded gas obtained therefrom, to mix with some ambient air (or exhaust air, or other air supply) to provide a cold side flow for downcast air or other air intended for cooling a volume or structure.

Mines operating in temperate climates are faced with cold temperatures in winter that often demand the use of conventional propane, natural gas or electric heaters to provide heat to the downcast air, and hot temperatures in summer that may demand chilling in order to continue operations during the hottest months. The present example describes heat exchange systems and methods developed for addressing these heating/cooling concerns.

In this example, heat exchanger systems and methods are described for transferring the heat from the upcast shaft to the downcast shaft, substantially reducing or eliminating the need for combustion to heat the downcast air, consequently providing ongoing savings subsequent to the payback date. As for cooling, the heat exchanger systems and methods in this example employ a cryogenic liquid-based approach described in detail hereinbelow.

In this Example, the same heat exchanger system is used to provide both the winter heating and summer cooling, which may provide benefit over conventional system(s). There may be minimal moving parts (although some small cryogenic pumps may be used, which may easily be operated by a small solar cell and battery system located at the site if desired); thus potentially avoiding installation of trunk lines to deliver electricity to the site to operate either the heating or chilling systems in certain embodiments.

In the example below, a heat exchange system for upcast shaft heat recovery to provide downcast shaft heating in winter, downcast shaft cooling in summer, and (optionally) electrical power generation from liquid cryogen expansion is described. The heat exchanger system may use warm, moist exhaust air from a mine or other formation or structure to pre-heat the supply or downcast air being provided to the mine or other formation or structure during winter months, reducing or eliminating the burning of fossil fuels for such heating.

Due to the expansion of the cryogenic liquid from one litre of liquid to about 750 litres of gas, an option exists to provide electrical power through the use of a turbine coupled to a generator. In the following example, it is estimated that at the chilling requirements needed for an example mine, such a turbine configuration may provide about 2 MWe power.

In certain embodiments, the heat exchanger of the heat exchange system may comprise a self- contained air-to-air parallel plate-type system. In certain embodiments, the heat exchanger may be comprised of a high-quality fibre reinforced resin-based material, for example. The material characteristics may, in certain embodiments, be such that the heat transfer may be superior to metals, the resistance to industrial contaminants may be superior to metals, and/or the lifetime maintenance may be reduced or negligible. The changes in the psychrometric properties of the air as it passes through the heat exchanger may cause water to be expelled from the air, which may provide for a level of self-cleaning in the system. It is contemplated that as the water droplets form, the whetting of the surface may be such that droplets flow to the bottom where contaminants and water are easily collected, thus the impact on the local environment in terms of atmospheric emissions may be reduced in such embodiments.

In the winter months, heat recovery from upcast air using the heat exchange system described herein may provide for reduced energy costs. Downcast air is typically warmed to a positive temperature in winter months to avoid shaft icing and other operational problems. Although electric heaters may be used in some cases, generally this has conventionally been accomplished by combustion of propane or natural gas to increase the temperature from ambient surface temperature to approximately 2 C to 4 C for the downcast air. In operations where propane is trucked to the site and stored, the costs for such conventional heating may be substantially increased.

It is contemplated that the capture of heat from the upcast air may reduce the cost of heating, and may also reduce the emission of greenhouse gas (GHG). Consequently, a reduction of both the cost of fuel to heat the downcast air and the cost of carbon emissions may be achieved.

In this illustrative example, it is contemplated the heat from the upcast air may be available through three primary sources:

1) The lapse rate or temperature change of air under changing altitude is an increase of 9.8 C/km for descending dry air and 4.6 C for descending wet air, thus a typical lapse rate is about 6.5 C for typical shaft conditions;

2) The skin temperature of the rock increases with increasing depth, thus variations in air flow may result in variations in heat entering the air from the host rock as the air flows through the mine workings. The longer the traversal of the air through the mine workings the more heat is available and the higher the air temperature at the exit from the mine; and

3) Equipment and operations may liberate heat; recovering heat from equipment may serve to reduce the cost of the fuel or electricity purchased to operate the equipment, in a similar way that a cogeneration system operates. Similarly, operations such as blasting liberate heat which may also be captured through the heat exchange system.

Figures 8-10 show that the heat exchange system of this example may be placed inline with a ventilation duct connecting the upcast ventilation to the downcast ventilation shafts. By an air-to- air heat transfer using a plate arrangement-type heat exchanger configured such that the upcast air is vented to the atmosphere, without mixing or contact with the fresh air, while the fresh air is drawn through the heat exchanger, the heat exchange system of this example may allow for high efficiency of heat exchange, typically about 65% of the heat available from the upcast air may be transferred to the downcast air in this example. In the depicted embodiment, the heat exchanger is used in connection with an air duct for the pre-heated air running from the exhaust station to the inlet station for a mine, the air duct having a cross-section of about 6m x 5m.

Operational benefits may be determined, at least in part, by a) the ambient temperatures at the surface, which determines the amount of heat used to provide a downcast temperature of 2°C to 4°C; b) the relative cost of the heating as determined by the consumption of combustible fuel and electricity to operate the systems; and c) the installation cost of the heat exchange system as described herein that may create associated ongoing savings (for example, from reduced or eliminated fuel costs and/or GHG credits, for example).

From these costs the payback period may be calculated, then afterwards the savings may become a real decrease in the operating expenses of the operations.

Performance estimates for the heat exchanger in this example are shown in Table 1.

Table 1: Performance estimates for the heat exchanger of this example.

Using the data from the above performance estimated table an estimate of the carbon tax credit and reduction in combustion of propane or natural gas and the associated ongoing savings that result as assessed (see Table 2). This is only in connection with the winter downcast air warming with no connection to the summer cooling.

Table 2: Estimate of the carbon tax credit and reduction in combustion of propane or natural gas and the associated ongoing savings in connection with the winter downcast air warming in a sample appliation scenario:

It is therefore estimated that in this example, pre-heating of downcast air up to 4°C may be possible at all times down to air temperatures of -37°C. Theoretical frost limit was calculated to air temperature -54°C. Gradual freezing on the plate surfaces may start to occur 6 - 7 degrees warmer than the theoretic frost limit. Figure 8 depicts an illustrative example of a heat exchange system as described in this example, comprising a heat exchanger. Inlets (200) and outlets (201) for upcast air from the mine, as well as inlet (not visible) and outlet (202) for downcast air are shown, Flow direction is indicated by arrows. In the depicted example, the upcast air from the mine is comparatively hot, and the heat is extracted and used to heat the downcast air prior to the air being supplied down to the mine. The upcast air and the downcast air are not mixed.

Figure 9 shows the heat exchange system of Figure 8, installed and integrated with pre-existing ventilation exhaust (including exhaust fans) (203) at the surface of a mine. Figure 10 shows the heat exchange system of Figure 9, further including an extension ventilation duct (204) connection to the downcast air on the surface for supplying the downcast air to the mine. The inset (not to scale) depicts a cryogenic liquid-based chilling system (205) (which may include a cryogenic liquid storage tank and may optionally include a cryogenic liquid generator; see Figures 12 and 15, and discussions thereof, for further detail), which may be configured and used to cool the downcast air, and/or may be configured and used to cool the upcast air such that the upcast air cools the downcast air, or both. The configurations depicted in Figures 10, 12, and 15 represent a preferred embodiment providing both heating and cooling to the ventilation air.

It is contemplated that for the exemplified heat exchanger system, the same heat exchanger may be used not only for heating of downcast air in the winter, but also to provide cooling of downcast air in the summer, which may provide opportunity to reduce overall CAPEX costs by using the same system for both cooling and heating. Depending on the temperature differential of the upcast air to the ambient surface air, there may be some chilling of downcast air that may be achieved if the upcast air temperature is sufficiently lower than the ambient surface air. In addition, the depicted heat exchange system uses cryogenic liquid as a cooling vector, which may allow for the cooling to be delivered on an as-needed basis (and is not dependent on the upcast air being cool). Conventionally, cooling systems were typically bulk chilling in nature and consequently not able to respond to variations in temperatures at the surface. The present heat exchanger system may allow for responding to temperature and/or operational variations, and/or may provide an enhanced efficiency via the liquid cryogen chilling approach described herein. Since the air-to-air heat exchangers isolate the two air streams without any mixing, it is possible to use liquid nitrogen in the depicted heat exchanger system rather than an artificial liquid air (comprised of 20% oxygen and 80 % nitrogen, for example). Liquid nitrogen is often discarded as a by-product of the process to acquire oxygen, and thus may be substantially less expensive for the same chilling power. In the depicted systems (see Figures 10, 12, and 15-18), a cryogenic liquid chilling system (206) is provided, comprising a cryogenic liquid storage tank (207), and the cryogenic liquid may be allowed to expand in a chamber (mixing chamber (208)) producing an expanded gas, where the expanded gas is mixed with an incoming air stream (via ambient air inlet (209)) from the upcast shaft (or from ambient air at the surface, or both) to provide a cool air stream to the heat exchanger (via outlet 210), which is used at the heat exchanger to cool the downcast air stream being supplied into the downcast shaft. In the depicted example, the cooling power of the cryogenic liquid is a two-stage process. First, the latent heat of vapourisation is absorbed in the process of the cryogenic liquid changing to a gas, which absorbs about 205 kJ/kg. Secondly, the cold gas, which is about - 180 C at this point with a density of about 4.2 kg/m ³ , is mixed with warmer air, potentially air that is cooler than ambient surface air (if the upcast air is cooler than ambient surface air), providing an additional cooling benefit. In the depicted example, the air mixed with the cold gas from the cryogenic liquid is sourced from the upcast shaft to raise the flow rate up to about 100 m ³ /s, and this process absorbs about 230 kJ/kg. The cool air interacts through the heat exchanger to extract heat from the downcast air, thus the desired cooling may be achieved and may actually follow the daily temperature variations to both provide the desired environment, and may reduce cooling costs as compared with other convention cooling approaches.

In certain embodiments, it is contemplated that electricity may be generated from the expansion of the cryogenic liquid used for chilling. As will be understood, as the cryogenic liquid absorbs heat and converts to gas used for chilling the air supplied to the heat exchanger, energy is available that may be captured using, for example, a turbine. Capturing the power from the expanding gas by the use of turbines and generators may therefore provide an additional option for cost reduction and/or reduction of greenhouse gases. The power available for electricity production may depend on the amount of liquid nitrogen used for chilling; however, should more cooling be performed than the amount of liquid cryogen flow for operating the turbine/generator then it is contemplated that the cryogenic liquid may be used independent of the turbine/generator flow to supplement the extra cooling desired, for example. Such designs may employ readily available turbines or piston engines and generators in the size range of interest, and/or may be a combination of different size turbines and generators, which may allow for flexibility of the system. As a benchmark size for evaluating the input cryogenic liquids used for a given power output based on the Glencore study for Onaping Depth, a 5 MWe system may require about 1090 tonnes/day of cryogenic liquid, so the consumption for electrical generation may be about 2.5 kg/s per 1 MWe or about 210 tonnes/day per 1 MWe. The recovery of electricity from a cooling system are described in detail hereinabove.

Further consideration of the cooling demonstrates the potential for cooling on demand. An analysis was performed using the weather data for May 24, 2015 as shown in Figure 11. The daily temperatures both wet-bulb (WB) and dry-bulb (DB) are used to calculate the wet bulb globe temperature WBGT as a benchmark temperature for calculation purposes. The area shaded in blue is the temperature zone where chilling is desired as per the target temperature underground set to 35 C (100 % relative humidity is assumed consequently the WB, DB and WBGT temperatures are identical). From these data the chilling demand is calculated for a random day (24/05/2015) and shown in Figure 11.

The amount of chilling needed/desired changes as the surface temperature or subsurface target temperatures change, and this is an important consideration as the chilling demand may be met by adjusting the flow of the cryogenic liquids. As shown in Figures 10 and 12, the cryogenic liquid in this example may flow from the low pressure storage tank (207) to a mixing container (208) where air from the upcast shaft (or ambient air, or a mixture of both) may be used to provide a flow velocity and appropriate volume, such that, heat from the incoming downcast air at the heat exchanger is transferred to the cold air flow from the mixing chamber (208) in an efficient manner. This step may be performed in order for the air travelling through the heat exchanger to be able to contact the plates on the cold side with sufficient turbulence and dynamics to carry away the heat from the incoming air (intended to be downcast air for the mine). These air streams are separate due to the nature of the heat exchanger, and the parallel plates are arranged such that alternate channels (approximately 15 mm in width in this depicted example) contain the air from each source; thus, the air streams are independent and do not mix in this example. This is also the case in the winter warming, where the upcast air containing the heat does not mix with the incoming downcast air in this example, which absorbs the heat consequently reducing or eliminating the need for heating by propane, natural gas or electric heaters.

Sample calculations for the cooling power of liquid nitrogen were also performed. In the case where the cooling is desired underground, an artificial mixture may be created, such that, when released underground the result is breathable air; thus, in certain embodiments measured may be taken such that there is no impact on the oxygen levels underground and the workers are not impacted in any way.

In certain scenarios, the chilling may be created on the surface and the air streams do not mix; therefore, the use of liquid nitrogen may be of interest on the simple basis that it is substantially less expensive, and it may even be available as a by-product of an operating oxygen plant, for example. For these calculations, the chilling is achieved by the use of a cryogenic liquid, which upon expansion from a liquid to a gas volumetrically increases by a factor of about 750 times. Given a cryogenic liquid supplied at about -196 C there are two stages of heat absorption. The latent heat of vapourisation is the heat required to change the state from a liquid to a gas. The latent heat of vapourisation is about 205 kJ/kg; this heat is absorbed in what is termed a “flash”, which means that when the liquid is allowed to expand in the expansion chamber the process is rapid. The second heat absorbed is due to the expansion of the gas from a very cold temperature and relatively high density to the ambient temperature of the final mixture of the cryogenically sourced air (nitrogen) and the air used to take the volume up to an appropriate operational amount for the efficient use of the heat exchange system.

Table 3 below provides values calculated at the point where the peak chilling of 4.9 MWr is desired according to Figure 11. The amount of cryogen flow is determined at a 65 % heat exchanger efficiency for the transfer of heat from the incoming downcast air to the cold input air. The cryogen use is 12.1 kg/s to provide the calculated chilling, thus, at 65 % efficiency the actual flow is 18.7 kg/s. Flow in litres at 18.7 kg/s is 21.5 1/s. The liquid volume flow of 21.5 1/s provides 16.1 m ³ /s volumetric air flow delivered from the expansion of the cryogen, this air is mixed with about 84 m ³ /s of air from the upcast shaft to provide an approximate 100 m ³ /s air flow to be used as the cold side of the heat exchanger in this sample calculation.

Table 3: Sample calculation of cooling by heat absorbed from incoming downcast air by air mixed with liquid nitrogen

In the embodiment depicted in Figure 12, a storage tank (207) holds liquid nitrogen at the site. The liquid is either produced on site or delivered from a remote location. Cryogenic liquids have many industrial uses, and may be easily piped from a larger liquefaction plant, for example. Figure 12 shows a cryogenic liquid chilling system in which the cryogenic liquid may flow from the low pressure storage tank (207) to a mixing container (208) where air from the upcast shaft (or ambient air, or a mixture of both) may be used to provide a flow velocity and appropriate volume, such that, heat from the incoming downcast air at the heat exchanger is transferred to the cold air flow (generated within the mixing chamber (208) and supplied to the heat exchanger) in an efficient manner. Figure 12(A) provides an isometric view, 12(B) provides a back view, 12(C) provides a front view, 12(D) provides a right view, and 12(E) provides a top view of the cryogenic liquid-based chilling system. In Figure 12, dimensions are only for the purposes of computational fluid dynamics modelling of a simplified system for the purpose of demonstrating the principles of operation; the simulation is considered to be representative of expected dimensions that may be used, but are not limiting and my be varied to suit particular implementations.

The depicted cryogenic liquid-based chilling/cooling system comprises a storage tank, a mixing chamber and an outlet to either the heat exchanger, and/or the high velocity gasses may be constrained to exit into a turbine, which may provide a readily available electrical power generation system, or both. In the power generation case, the chilling may be achieved by passing the ventilation air over a separate heat exchange system to cool the downcast air and the high velocity gas may be created by the expansion of the cryogenic liquids and directed through a turbine/generator system. Testing, data, and a diagram of a prototype of such a system is provided hereinbelow. The prototype system is a cross flow heat exchanger, where the ventilation air passes through the insulated system four times in order to maximise the collection of the cooling. The cryogenic liquid is inserted into a pipe with cooling fins attached, which is continuous and does not mix with the ventilation air. At the exhaust of the cryogenic air flow the air is directed through a turbine, which drives a generator to power the fan. This demonstrates the energy storage capacity along with the cooling capacity in a single system. Being able to use the energy storage and electricity production may be of notable benefit to the operations in terms of having on-site power for emergencies and the ability to interact with the global adjustment, which may provide yearly energy cost reductions, for example. The prototype, including air flows, cryogenic liquid injection, and expansion to a gas, which drives a turbine to power the fan, is shown in Figure 5, and has already been described in detail hereinabove.

Figure 13(A) shows an image of the prototype, in which liquid enters the system from the right and continues through the pipe to the turbine. The depicted prototype has the heat exchanger insulated, and is generating both chilling and power. Figure 5 shows a diagrammatic representation of flows for the prototype. Figure 13(B) shows results from the prototype for the heat flux removed from the ambient fan driven air flowing through the insulated container containing the heat exchanger. Figure 14 shows temperatures of the ambient room, see triangles at bottom to indicate the room air change times, and note the instantaneous temperature change from the time the cryogenic liquid is started flowing through the prototype system.

It will be understood from Figures 13(B) and 14 that the chilling may be able to rapidly respond to any variations in ambient surface air conditions and also to the underground operations that may introduce heat. This is a significant difference compared to conventional underground cooling systems. The ability to use the chilling system as an energy storage vector may be beneficial in terms of economics in these respects.

Computational fluid dynamics modelling of a simplified cryogenic liquid chilling system as described herein was also performed. An example of a cryogenic liquid chilling system as described herein is depicted in Figures 12 and 15. The CFD modelling presented in Figures 16-

18 is provided to give an understanding of the basic operating principles of the illustrative system. In Figures 16-18 the flow of the inlet air is directed from the upcast shaft into the inlet

(209), the flow rate is 90 m ³ /s and the temperatures for the simulations were 20 C and 35 C. As shown in Figure 15, the air created from the cryogenic liquid is introduced to an annular tube

(210) with exit ports to create mixing with the incoming air from the ventilation exhaust in mixing chamber (208), and the cooled air mixture exits via ventilation outlet (211) to be supplied to the heat exchanger. In mixing chamber (208), ultra cold cryogenic liquid and/or gas therefrom expands and mixes with ambient/supplied air to provide a cooled air, used to cool downcast air for a mine.

CFD modelling internal to the mixing chamber is shown in Figures 16-18. In Figure 16, computational fluid dynamics modelling is shown for about the first ten seconds from the start of the cryogenic flow, this is a cross section through the centre of the mixing chamber shown in Figure 15. In Figure 17, details of the interaction at the mixing zone where the cryogenic liquid expands and mixes with the incoming ambient air flow are shown. In Figure 18, flow trajectories of a simulation for incoming air temperature of 35 C at 90 m ³ /s and 10 m ³ /s of air created from the expansion of the cryogenic liquid to illustrate the mixing is shown (cross section cut plots are included to represent the temperature profiles).

As shown in these Figures, the incoming air is directed perpendicularly to create a swirling effect, which promotes mixing to create a smooth temperature profile at the exit vent. The outlet is directed either to the heat exchanger where the heat is exchanged to the downcast air without any mixing. Alternatively the outlet vent air may be directed to a turbine to create electrical power. Or, a combination of these may be performed.

At the cryogenic liquid flow rates expected, the output air when directed through a turbine/generator system may be capable of producing about 2 MWe.In a comparison to a bulk air chiller, it is contemplated that in certain embodiments designs described hereinabove may provide about 5 MWe electrical power while simultaneously producing about 8 MWr refrigeration.

In this particular example the cooling is provided by the heat exchange system on the surface, which also provides the GHG reduction by eliminating or substantially reducing the combustion for heating the downcast air in winter. In other designs, it is contemplated that an energy storage system with power generation capacity may be placed underground, which may absorb the heat from the mine to produce electricity. Such systems are described in detail herein above. In some examples, surface systems and underground systems as described herein may both be used for cooling based on cryogenic liquid use.

One or more illustrative embodiments have been described by way of example. It will be understood to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims..