System for Upgrading Waste Heat

Technical Field

A system and method for the upgrading of waste heat is disclosed. More specifically, the system and method can be driven by the waste heat to upgrade the waste heat. At the same time, the system and method can reduce entropy or chaos in a waste heat stream. The system and method can be applied in a broad range of industries and contexts to extract heat from relatively low temperature zones and transfer it to (for use in) relatively high temperature zones.

Background Art

Many industries discharge warm and hot process and waste gases to atmosphere such that the heat energy is lost. This can also result in a contribution to atmospheric warming. Warm liquids such as waste waters can also be released to the environment. It would be desirable if some of this wasted heat energy could be captured and utilised in that industry or elsewhere, especially the so-called "low grade" heat (e.g. streams having temperatures of less than around 100 ⁰ C).

WO 2005/073644 (to the present applicant) discloses a method, apparatus and system for transferring heat which can be embodied as an adsorption chiller that employs a simple modular design principle.

In addition, it is known to pump heat from a lower to a higher temperature using a compression cycle system. For example, known compression cycle systems that extract heat from lower temperatures and pump into the higher temperature zones are referred to as reverse cycle systems. Ammonia and methanol systems have also been used for extracting ocean heat, but all such systems are based on compression cycle principles and require a compressor. The systems also have moving parts and need to be operated either with electricity or petroleum fuels, and cannot be operated simply with heat. Further, the compression cycle systems use hydrofluoro-carbons (HFCs) as a working fluid. HFC is a green house gas (with global warming consequences) and its commercial use is to be phased out internationally by 2020. Ammonia systems are manufactured of carbon steel which suffers severe corrosion from the sunOunding air on the outer surface of the equipment and pipes, particularly on evaporator outer surfaces, where moisture from ambient air may condense.

To date, there is no knowledge or teaching in the art of a waste heat driven desorption heat "pump" for waste heat recovery, especially from a low grade heat source.

Summary of the Disclosure

In a first aspect there is provided a system for recovering heat of a relatively lower grade from a fluid and transferring that into a fluid having a relatively higher grade heat so as to raise the temperature thereof, the system comprising first and second heat transfer units, with each unit comprising one or more modules, and with each module comprising a chamber having a first part which contains a first gas adsorbent material and a second part which contains a second gas adsorbent material for a ■ working gas, the parts being connected so as to allow gaseous communication therebetween whilst being relatively thermally isolated from each other; whereby, in a first stage:

(i) the higher grade fluid is passed through the first heat transfer unit so as to flow around the (or each) module first part and cause desorption of the working gas from the first gas adsorbent material;

(ii) the lower grade fluid is passed through the first heat transfer unit so as to flow around the (or each) module second part and cause adsorption onto the second gas adsorbent material of the desorbed working gas;

(iii) the lower grade fluid from the first heat transfer unit is heated (as defined below) and then passed through the second heat transfer unit so as to flow around the (or each) module second part and cause desorption of the adsorbed working gas from the second gas adsorbent material, whereby the lower grade fluid that leaves the second heat transfer unit is cooled (as defined below);

(iv) the higher grade fluid from the first heat transfer unit is passed through the second heat transfer unit so as to flow around the (or each) module first part such that, during adsorption of the desorbed working gas onto the first gas adsorbent material, the higher grade fluid that leaves the second heat transfer unit is heated.

Such a system can provide waste heat driven heat pumping from a lower temperature stream to a higher temperature stream. In this regard, a relatively lower temperature stream with high entropy can be transformed into a relatively higher temperature stream with lower entropy. Thus, beneficially, the system can be used to reduce entropy or chaos through the use of more chaotic or high entropy heat.

In step (iii) of the first stage, when it is stated that "the lower grade fluid from the first heat transfer unit is heated" this refers to a relatively marginal heating of the fluid so as to enable the heat of adsorption released in the second part of the first heat transfer unit to be removed. hi step (iii) of the first stage, when it is stated that "the lower grade fluid that leaves the second heat transfer unit is cooled" this refers to a relatively marginal cooling

of the fluid so as to enable a completion of desorption of adsorbed working gas from the second gas adsorbent material.

It is to be appreciated that the use herein of a "steps" nomenclature such as "(i) to (iv)" or "a., b." etc. is not intended to imply that the steps are sequential. This is because, during operation of the system, the steps may occur simultaneously.

The terminology "relatively lower grade heat" and "relatively higher grade heat" employed herein is understood by persons of ordinary skill in the art of heat transfer and heat pumping. For example, a low grade waste heat stream is known to have a temperature of around or less than 100 ⁰ C. The term "fluid" employed herein is understood by persons of ordinary skill in the art of heat transfer and heat pumping to include liquids, gases and mixtures thereof.

In one form the heated higher grade fluid leaving the second heat transfer unit is recovered e.g. for recycling back into an industrial process. In this regard, the system of the first aspect can be added onto an existing industrial process to upgrade the heat of one or more fluid streams thereof.

The system can further comprise:

- a first four-way valve wherein the heated higher grade fluid passes from the second heat transfer unit and through the first four-way valve to be recovered, and wherein the higher grade fluid to be heated also passes through the first four-way valve and then to the first heat transfer unit; and

- a second four- way valve wherein the lower grade fluid from which heat is recovered passes through the second four-way valve and into the first heat transfer unit, and wherein the cooled lower grade fluid passes from the second heat transfer unit and through the second four-way valve and then out of the system. Such valves allow for easy and rapid switchover to a second stage of operation to thereby maintain continuity of operation of the system and method.

In one form of step (iii), heating of the lower grade fluid prior to passing it through the second heat transfer unit can be achieved by bleeding a portion of the higher grade fluid entering the second heat transfer unit into the lower grade fluid. In this case, a line can extend between the higher grade fluid and the lower grade fluid, and a valve can be positioned in that line that can be progressively opened to effect the bleeding.

Alternatively, it can be achieved by exchanging heat from a separate source into the lower grade fluid (e.g. such as solar, or from waste heat recovered from engines, boiler, furnace or turbines, exhaust from the condensers of air conditioners, heat from the return stream to cooling towers, etc.).

Once the working gas has completed desorbing from the first gas adsorbent material in the first heat transfer unit, and once the working gas has completed adsorbing onto the first gas adsorbent material in the second heat transfer unit, a second stage can be commenced to maintain continuous system operation. In this regard, the flows of the higher and lower grade fluids can be reversed, whereby:

(i) the higher grade fluid is passed through the second heat transfer unit so as to flow around the (or each) module first part and cause desorption of the working gas from the first gas adsorbent material;

(ii) the lower grade fluid is passed through the second heat transfer unit so as to flow around the (or each) module second part and cause adsorption onto the second gas adsorbent material of the desorbed working gas;

(iii) the lower grade fluid from the second heat transfer unit is heated (as defined below) and then passed through the first heat transfer unit so as to flow around the (or each) module second part and cause desorption of the adsorbed working gas from the second gas adsorbent material, whereby the lower grade fluid that leaves the first heat transfer unit is cooled (as defined below);

(iv) the higher grade fluid from the second heat transfer unit is passed through the first heat transfer unit so as to flow around the (or each) module first part such that, during adsorption of the desorbed working gas onto the first gas adsorbent material, the higher grade fluid that leaves the first heat transfer unit is heated.

In this second stage the heated higher grade fluid leaving the first heat transfer unit can again be recovered (e.g. for recycling to an industrial process).

In step (iii) of the second stage, when it is stated that "the lower grade fluid from the second heat transfer unit is heated" this refers to a relatively marginal heating of the fluid so as to enable the heat of adsorption released in the second part of the first heat transfer unit to be removed.

In step (iii) of the second stage, when it is stated that "the lower grade fluid that leaves the first heat transfer unit is cooled" this refers to a relatively marginal cooling of the fluid so as to enable a completion of desorption of adsorbed working gas from the second gas adsorbent material.

Again, the second stage can employ the first and second four-way valves so as to reverse fluid flows.

In step (iii) of the second stage, heating of the lower grade fluid prior to passing it through the first heat transfer unit can again be achieved by bleeding a portion of the higher grade fluid entering the first heat transfer unit into the lower grade fluid. Again, a line can extend between the higher grade fluid and the lower grade fluid, with a valve being positioned in that line that can be progressively opened to effect the

bleeding. Alternatively, it can be achieved by exchanging heat from a separate source (as outlined above) into the lower grade fluid.

In the system each of the first and second heat transfer units can comprise a plurality of modules. In each module the first gas adsorbent material can be a different material and have a different adsorptivity to the second gas adsorbent material. For example the first gas adsorbent material can be a zeolite, and the second gas adsorbent material can be activated carbon. The working gas can be carbon dioxide that is pressurised relative to ambient pressure (e.g. to 0.5 MPa).

Further, each unit can comprise an internal dividing wall in which the modules are supported and through which the modules extend, whereby the first gas adsorbent material for each of the modules is located on one side of the wall, and the second gas adsorbent material for each of the modules is located on the other side of the wall.

In the system the higher grade fluid is usually a process gas or liquid and the lower grade fluid is usually a waste process gas or liquid. In one example, both the higher and lower grade fluids can be air.

In a second aspect there is provided a method for recovering heat of a relatively lower grade from a fluid and transferring that into a fluid having a relatively higher grade heat so as to raise the temperature thereof, the method making use of the system of the first aspect and comprising the steps of: (i) passing the higher grade fluid through the first heat transfer unit to cause working gas desorption from the first gas adsorbent material;

(ii) passing the lower grade fluid through the first heat transfer unit to cause working gas adsorption onto the second gas adsorbent material;

(iii) heating the lower grade fluid from the first heat transfer unit and passing it through the second heat transfer unit to cause working gas desorption from the second gas adsorbent material, whereby the lower grade fluid that leaves the second heat transfer unit is cooled;

(iv) passing the higher grade fluid from the first heat transfer unit through the second heat transfer unit so that, during working gas adsorption onto the first gas adsorbent material, the higher grade fluid that leaves the second heat transfer unit is heated.

The method can further comprise the step of feeding back the heated higher grade fluid from the second heat transfer unit into an industrial process.

Brief Description of the Drawings

Notwithstanding any other forms which may fall within the scope of the system and method as set forth in the Summary, specific embodiments of the system

and method will now be described, by way of example only, and with reference to the accompanying drawings in which:

Figure 1 shows a schematic view of a simple desorption module for use in the system and method; Figure 2 shows a schematic flow diagram of a specific desorption system according to the system and method, the system employing a plurality of the desorption modules of Figure 1 in each of two units;

Figure 3 shows a schematic view of one of the desorption system units showing the position of specific thermocouples used in the experimental procedure, with the resulting temperatures then being plotted as in Figures 4 and 5 ;

Figure 4 is a graph plotting Temperature against Time for the system of Figure 2 during operation over 300 hours when the regenerator was isolated by shutting down the inlet and exit, there being no flow of hot air or cold air through the regenerator; and

Figure 5 is a graph plotting both Regenerator and Desorption Temperatures against Time for the system of Figure 2 during operation over a 12 hour period when the hot air at 115 ⁰ C was continuously passed at a constant flow rate.

Detailed Description of Specific Embodiments

The system and method as illustrated in Figure 2 advantageously enabled the heat driven recovery of low grade waste heat below 100 ⁰ C, especially at temperatures as, low as around the 13-17 ⁰ C range. When applied to e.g. low grade waste heat from a given industry process (a "main process") the low grade heat was able to be amplified or upgraded to a temperature where it could be recycled or reused in the main process.

For example, potential applications included the heat rejected from the exhaust of compression cycle heat refrigerators, from the return stream of cooling towers and even to heat arising from the warmth of sunshine or of from ambient temperature air (e.g. ranging from, -55 to +55 ⁰ C), all of which could be upgraded, hi other words the system and method was observed to be generally applicable in extracting heat from a relatively lower temperature zone and transferring it to a relatively higher temperature zone(s) of a main process .

System Components

Prior to describing the present system and method in further detail, the components of the system as illustrated in Figures 1 and 2 will first be explained. Referring firstly to Figure 1 , the desorption module comprises a sealed vessel

10 having two cylindrical chambers (e.g. tubes, such as stainless steel tubes), being a regenerator chamber 12 and a desorption chamber 14. The chambers are connected by a

joining section in the form of a narrower (e.g. smaller diameter) conduit or neck 16 (such as a smaller diameter tube). To provide for greater thermal isolation of the chambers 12, 14 the conduit 16 can be formed from a material having lesser thermal conductivity than the chamber walls (e.g. a less thermally conductive stainless steel) and is typically welded to the chamber walls to seal the vessel 10.

Regenerator chamber 12 is packed with a first adsorbent material, typically in the form of a molecular sieve (e.g. a zeolite such as a 13X zeolite) and the desorption chamber 14 is packed with either a different second adsorbent material (e.g. a surface activated powder such as activated carbon) or the same material but having a different adsorptivity (e.g. another type of zeolite but having, for example, a lesser adsorptivity e.g. 1OA, 8A, 5A zeolites or another type of 13X zeolite). One or more heat transfer elements in the form of a plurality of discrete metal wire mesh panels can be arranged in each of the chambers 12&14, together with the first and second adsorbent materials (ie. the panels can be dispersed through the adsorbent material). The panels are typically formed from a material not reactive to the gas and materials in vessel 10, such as stainless steel, brass, aluminium or copper, and of a material having sufficient thermal conductivity. The panels function to enhance thermal conductivity between the adsorbent material and the wall and thus exterior of each chamber, hi addition, it has been observed that the panels enhance the mass transfer rate of carbon dioxide through each of the first and second adsorbent materials.

The sealed vessel 10 further comprises a suitable pressurised gas, typically carbon dioxide because of its abundance and ease of use; but other gases can be used such as refrigerants, ammonia, alcohol, water (steam), nitrogen etc. in combination with adsorbents suitable to the gas. The sealed vessel 10 is configured such that the gas can pass continuously and unhinderedly between each of the chambers 12, 14 via the conduit 16. Advantageously no valving or additional flow control is provided or required and, as a further advantage, the sealed vessel has no moving parts. Further, the ^■ sealed vessel 10 is typically configured so that the desorption chamber 14 (housing the second adsorbent material) is, at least to an operable extent, thermally isolated from the regenerator chamber 12 (housing the first adsorbent material). This is optimally achieved by employing the narrower conduit 16 to connect but space apart the chambers. However, thermal isolation can be further enhanced by employing appropriately positioned insulation, including insulation barriers and baffles in, around and/or between the chambers. In a first mode of use, the first adsorbent material is selected to have a higher adsorptivity for the vessel gas then the second adsorbent material. For example, when

starting at ambient temperature, it is observed that a greater proportion or a bulk of the vessel gas is adsorbed on the first material.

Referring now to Figure 2, a desorption system 20 is depicted for extracting heat from relatively low temperature zone (e.g. low grade waste heat) and transferring it to one or more relatively high temperature zones is shown. The system 20 employs a plurality of the sealed desorption vessels 10 of Figure 1, with the vessels arranged in parallel, in each of parallel module units 22A and 22B.

To enhance the thermal isolation of chambers 12 and 14, each module unit 22 comprises a thermal barrier wall 24 positioned to divide each regenerator chamber 12 from its respective desorption chamber 14 (except for conduit 16, which extends through wall 24). The barrier wall 24 thus defines in module unit 22A a Regenerator zone Rl and a Desorption zone Dl, and in module unit 22B a Regenerator zone R2 and a Desorption zone D2. Barrier wall 24 can also be formed from and/or lined with an insulating material. The system 20 further comprises two four-way valves 30 and 32 which are respectively arranged for directing fluids (e.g. gases) with respect to the Regenerator zone Rl and Regenerator zone R2, and the Desorption zone Dl and Desorption zone D2.

In this regard, the four-way valve 30 can selectively direct a main process hot gas 34 (e.g. a hot air stream) into the regenerator zone Rl as stream 36, whilst simultaneously receiving a heated gas stream 38 (e.g. a heated air stream) from the other regenerator zone R2, and then passing this out as an increased heated gas stream 40.

On the other hand, the four-way valve 32 can selectively direct a process waste stream 42 of low grade heat (e.g. a waste gas such as air) into the Desorption zone Dl as stream 44, whilst simultaneously receiving a relatively heated stream 46 from the other the Desorption zone D2, and then passing this out as gas stream 48.

Experimental Overview A laboratory scale desorption cooler having the system configuration of Figure

2 was operated to recover the heat from a lower temperature zone and pump it into a relatively higher temperature zone. Trials on the laboratory system indicated that the heat from a zone at 13 ⁰ C could be transferred to a zone of about 115 ⁰ C. In addition, it was noted that the heat from any relatively lower temperature zone could be transferred to relatively higher temperature zone with a suitable system reconfiguration.

In the desorption cooling module described in WO 2005/073644 (to the present applicant), during regeneration of the regenerator the heat was absorbed to compensate

- S - the latent heat of desorption of working fluid from the absorbent and to sensibly heat all components of the regenerator. The desorbed fluid from the regenerator was moved into the desorption cooler chamber and then adsorbed, releasing heat of adsorption. During regeneration the desorption cooler was maintained at ambient temperature (or at a temperature relatively lower than the regenerator) to allow adsorption of working fluid (adsorbate) on the adsorbent in the desorption cooler chamber.

However, in the present system and method, it was surprisingly discovered that, in the second step, if the regenerator was maintained at the regeneration temperature and the desorption cooler was reheated by low grade waste heat to a relatively higher temperature than that maintained during regeneration, the temperature of the regenerator rose from the original regeneration temperature.

Specific Example

In a first experiment the regenerator zone Rl and desorption zone Dl were maintained at around 115 ⁰ C and 7 ⁰ C, respectively, during regeneration. The regenerator zone Rl was isolated from the hot air supply when it acquired a steady temperature of around 115 ⁰ C. The desorption zone Dl was reheated to 21 ⁰ C. The temperature of the regenerator chambers 12 in zone Rl rose up to 135 ⁰ C, as illustrated in Figure 4. The specific sequential operation of the system of Figure 2 was as follows:

1. Regenerator Rl zone was regenerated by passing therethrough hot air 36 at 115 ⁰ C. During this period the corresponding desorber zone Dl was cooled by passing therethrough air 44 at 7 ⁰ C. During this period the adsorbate molecules were desorbed from the regenerator material in chambers 12 and moved towards the desorber chambers 14 and adsorbed on the adsorbent located therein.

There was some heat of desorption absorbed by the regenerators 12 in Rl from the heating air stream, and some heat of adsorption was released by the desorbers 14 in D2 into the cooling air stream 46. Because the adsorption-desorption was run as a batch process/system, and because of the high air flow rates employed, this did not change the air stream temperature significantly. This is why, in Figure 2, stream 36 is depicted at 115°C and stream 50 is also depicted at 115°C, and why stream 44 is depicted at 7°C and stream 60 is also depicted at 7°C. It was noted that a more significant change in temperature would be observed when a greater number of modules was employed in the heat transfer unit.

In accordance with the present system and method the exit stream 50 from the regenerator Rl and the exit stream 60 from the desorber Dl were respectively recycled

into regenerator R2 (as stream 52) and into desorber D2 (as stream 62), as shown in Figure 2.

2. During this period, and noting that the regenerator Rl was now regenerated, the valve Vl was maintained shut but valve V2 was partially opened, to an extent so as to convert the cold exit air stream 60 at 7 ⁰ C from desorber Dl into a warmer air stream 62 at 13 ⁰ C, before stream 62 entered the desorber D2.

The valves Vl & V2 were, at the appropriate stage, each used to produce a warm air stream 62 at 13 ⁰ C. However, in many industrial processes use can be made of another gas/liquid stream at 13 ⁰ C, or to achieve the 13 ⁰ C feed stream 62 into desorber

D2. hi such a case, the valves Vl & V2 would not be required or made use of.

The employment of the valves Vl & V2 also enabled the demonstration of a stream at 115 ⁰ C being upgraded to a 135 ⁰ C stream, with optimum system/method design and flow rates. In this regard, without air flow through the regenerator, the regenerator was able to be reheated to 135 ⁰ C from 115 ⁰ C (as shown in Figure 4).

3. hi any case, with the production of the warm air stream 62 at 13 ⁰ C, the stream 62 passing through the desorber D2 re-heated the desorbers 14 in desorber D2 and desorbed the adsorbate molecules. These then moved towards regenerator R2 and adsorbed on the adsorbent in the regenerators 12 in R2. As a result of this some heat of desorption was absorbed at the desorbers in D2 from the warm air stream at 13 ⁰ C such that the temperature of stream 46 exiting D2 was around 7 ⁰ C.

In Figure 2 stream 46 is at 7°C. However, stream 48 "Hot air" is depicted at 13°C. This is because, once the desorption in D2 was over, stream 46 (and thus 48) again acquired a temperature ofl 3 ⁰ C. hi addition, some heat of adsorption was released from the regenerators in R2 into the air stream 52 at 115 ⁰ C which then exited the regenerator R2 as stream 38 at 117 ⁰ C. The heat absorbed in the desorber D2 and the heat released in regenerator R2 respectively caused cooling and heating of the exit air streams 46 and 38 from the desorber D2 and regenerator R2, as shown in Figure 2.

4. At an appropriate time, when the regenerators in Rl were fully regenerated, and the working gas in the regenerators in R2 were now fully adsorbed on the adsorbent, a system changeover was initiated. In this regard, the flow of hot air 34 was now directed by four-way valve 30 into the regenerators in R2, whereby R2 regeneration began, with the exit stream from R2 being recycled to the regenerators in Rl to produce a higher grade heat stream exiting from Rl.

Similarly, the flow of low heat grade air 42 was now directed by four- way valve 32 into the desorber in D2, whereby D2 adsorption began, with the exit stream from D2 being recycled to the desorbers in Dl . Valve V2 was now shut down and valve Vl was now partially opened, to cause the reverse flowing stream 60 to rise to 13°C. This recycled slightly warmed stream now caused desorption to take place in Dl, with some heat of desorption being absorbed in D2, producing a cooled stream exiting D2, until desorption was completed in D2.

Thus, the system/method was periodically reversed to maintain, in effect, a continuous operation.

The explanation for the rise in temperature in stream 40 is as follows. The adsorbate molecules were desorbed when the desorption zone D2 was heated from 7 ⁰ C to 13 ⁰ C; (sometimes during laboratory testing the temperature could be allowed to overshoot to 21 ⁰ C). In any case, the adsorbate molecules acquired kinetic energy and moved up to the regenerator zone R2. The rise in temperature in the desorption zone D2 produced an increase in gas pressure within the vessels 10, which compressed the adsorbate fluid and forced it into the pores of the adsorbent in the regenerators 12 in R2. This resulted in a restriction in the movement of the fluid molecules and a loss of their kinetic energy, which was further reduced when the adsorbate molecules adsorbed onto the surface of the adsorbent in the regenerators 12 in R2. The loss of kinetic energy due to compression, restriction in molecular motion due to forced diffusion in the pores, and subsequent adsorption, resulted in a release of heat energy and a subsequent rise in temperature of stream 38, and thus of stream 40.

A steady state time cycle that refers to the steady state operation of the system of Figure 2 is set forth in Table 1.

Table 1 - Steady State Time Cycle

The temperatures shown in Figure 2 were obtained in a laboratory unit where the flow rate of the regenerator air was much higher than required. Upgrading of air from 115 ⁰ C to 130-135 ⁰ C was possible with the existing modules 10 because without air flow in the regenerator chamber the temperature of regenerator ends of the modules was able to be raised from 115 ⁰ C to 136 ⁰ C (Figure 4).

Figure 4 clearly depicts the heating of the regenerator, whereas the surrounding temperature measured by the thermocouples at the inlet and outlet of the regenerator is as depicted in Figure 3.

The temperature profiles of the regenerator side module temperature and cooling side inlet and outlet air temperatures with air flow through the regenerator side is shown in Figure 5. The change in inlet and outlet air temperatures at the heating side was not significant to record as the air flow at heating side was very high (152 litres/second). Experiments were conducted with lower flow rates to record a more significant change in temperature.

It can be seen that several pulses of temperature rise from 7 ⁰ C to 13 ⁰ C results in a corresponding temperature rise in the regenerator side module temperature from 112 ⁰ C to 115 ⁰ C. This clearly demonstrated that low grade heat could be used to further heat a higher grade stream.

As mentioned above with reference to the system and method depicted in Figure 2, the valves Vl & V2 were provided to partially mix the hot air with ambient air and produce a warm air stream to heat the cooling side of the system. However, the warm air can be sourced from another low grade heat source such as solar, or from

waste heat recovered from engines, boilers, furnaces or turbines, exhaust from the condensers of air conditioners, heat from the return stream to cooling towers etc.

The system and method specifically allowed for upgrading process stream temperatures using lower temperature waste heat streams. Further, the system and method was able to convert the entropy associated with a low grade waste heat stream into useful heat and, at the same time, raise the temperature of the lower temperature waste heat stream.

As far as the low grade heat source is concerned, this can comprise solar, natural gas, exhaust from an engine, turbine, boiler or furnace. A combination of these can provide a temperature whereby heat can be further recycled or recovered. The system and method was easily adapted to make use of heat from liquid, gas or mixtures of liquid and gas. The system and method could also be used to further improve the overall efficiencies and to reduce the emissions from systems which generate very low grade heat streams that are usually released into the atmosphere (and thus wasted). The system and method can also be used to increase the efficiencies of existing solar collectors and therefore reduce the installation costs and green house gas emissions associated with the construction and operation of existing solar thermal systems.

Further, the system and method can be used for developing a space heating system which pumps heat from a relatively lower temperature surrounding into relatively warmer zones. This can improve e.g. the efficient heating of residential, commercial and industrial complexes with solar energy, gas or waste heat along with the capturing of heat from much colder surroundings.

Whilst the system and method for upgrading heat have been described with reference to a specific embodiment, it should be appreciated that the system and method can be embodied in many other forms.

For example, whilst a simple example of waste air and process air streams has been provided, it will be appreciated that the waste heat of other waste gas or liquid streams can be captured to enhance main process fluid streams that are again comprised of gas or liquid streams other than air.