[0001 ] The present application relates to one or more waste heat recovery units that are independently operated or connected together. The application also relates to methods of making, assembling, installing, repairing, upgrading, modifying and using the one or more waste heat recovery units.

[0002] The present application claims earlier priority dates of following patent applications:

Singapore patent application (SG) 1020 1503 915P filed on 19 May 2015;

Taiwan invention patent application TW 104,128,594 filed on 31 August 2015; and

International patent application PCT/SG2015/050186 filed on 29 June 2015; [0003] Contents or subject matters of these priority applications are hereby incorporated entirely.

[0004] A waste heat recovery unit (WHRU) is an energy recovery heat exchanger that recovers heat from hot streams or ambient with potential high energy content, such as hot flue gases from a diesel generator, steam from cooling towers or waste water from different cooling processes such as in steel cooling. Known types of waste heat recovery unit include recuperators, regenerators, heat pipe exchanger, thermal wheel or rotary heat exchanger, economizer, heat pumps and run around coil. Traditionally, waste heat of low temperature range (0~120°C, or typically under 100°C) has not been used for electricity generation despite efforts by ORC (Organic Rankine Cycle) companies because the Carnot efficiency is rather low, which is about maximum 18% for 90°C heating and 20°C cooling, minus losses, typically ending up with 5-7% net electricity. In general, waste heat below 100°C could be used for the production of bio-fuel by growing of algae farms or could be used in greenhouses or even used in Eco-industrial parks. Waste Heat of medium (120-650 °C) and high (>650°C) temperature could be used for the generation of electricity or mechanical work via different capturing processes. For example, waste heat recovery system can also be used to fulfill refrigeration requirements of a trailer. The configuration is easy as only a waste heat recovery boiler and absorption cooler is required.

[0005] Known types of waste heat recovery units usually requires high capital investment as compared to useful energy recovered by the waste heat recovery units. Besides, since waste heat is of low quality (temperature), it is difficult to efficiently utilize the quantity of low quality heat contained in a waste heat medium. Heat exchangers of the waste heat recovery units tend to be larger to recover significant quantities which increases capital cost. Additional equipment of the waste heat recovery units requires extra maintenance cost, as compared to those required for recovering heat of high temperature. More units or larger sizes of waste heat recovery units are often necessary to install and operate the waste heat recovery units in practice. [0006] The present invention aims to provide a new and useful waste heat recovery unit. The invention also aims to present a new and useful method of making, assembling, installing, repairing, upgrading, modifying and using the waste heat recovery unit. Essential features are provided by one or more independent claims, whilst advantageous features are presented by their dependent claims.

[0007] According to a first aspect, the present application provides a waste heat recovery unit for recovering waste heat by a refrigerant via a heat exchanger. The heat exchanger is configured to receive the refrigerant in liquid phase at an inlet, absorb the waste heat by the refrigerant and discharge the refrigerant in liquid phase at an outlet. The refrigerant is circulated from the outlet back to the inlet in the waste heat recovery unit in forming a closed loop of circulation. In one embodiment, the heat exchanger includes a hydraulic motor having a heat exchanger chamber. The heat exchange chamber cooperates with other parts of the waste heat recovery unit in providing the heat exchanger. Embodiments of the invention provides that carbon dioxide is adopted as the refrigerant. More specifically, carbon dioxide of liquid phase is presented at the inlet, albeit gaseous and/or solid carbon dioxide may still present at times. Hence, the waste heat recovery unit is configured to utilize the refrigerant in liquid phase for circulation in a closed loop. Phase change from liquid to gas is largely avoided. [0008] Embodiments of the present application provide a waste heat recovery unit for recovering waste heat at 50°C or lower temperature by a refrigerant. The waste heat recovery unit is configured to be exposed to the waste heat (e.g. ambient heat) in order to heat up the refrigerant and expand volume of the refrigerant in forming a closed loop of circulation of the refrigerant. For example, the refrigerant is carbon dioxide that operates in a liquid phase, a super-critical phase or in both phases. Embodiments of the invention provide that carbon dioxide is circulated within the waste heat recovery unit at about at -56.6°C to 31 .1 °C, or pressure from 518 kPa to 7.38 MPa. The embodiments further provide that carbon dioxide in the waste heat recovery unit is able to operate in the liquid phase having temperature of slightly higher than -78.5°C. When being heated up, one or more movable parts of the waste heat recovery unit are only allowed to move in a predetermined direction (e.g. direction of refrigerant circulation) such that expansion of the refrigerant force the movable parts to move (e.g. displacement or rotation) according to the predetermined direction, thereby producing useful kinetic energy or work. In other words, the waste heat recovery unit is configured to covert waste heat to useful output of energy or motion by using the refrigerant in the closed loop of circulation. In practice, if carbon dioxide is adopted as the preferred refrigerant, the carbon dioxide can operate at the outlet with temperature of 20 to 50 degree Celsius and pressure of 50 to 80 bars and at the inlet with temperature of -50 to 0 degree Celsius and pressure 10 to 30 bars where the coldest temperature is preferred. The temperature and pressure of the between the inlet and outlet depend on the temperature of the embedded heat exchanger or the waste heat to be recovered. The higher the waste heat temperature, the higher the refrigerant temperature and pressure but it is best the refrigerant before exits at the outlet the temperature be at not more than 50 degrees Celsius and pressure contains to within the material strength which can be around 300 bars. The temperature and pressure ranges can be wider but are limited to the construction materials strength and limit.

[0009] The waste heat recovery unit may comprise a hydraulic motor that has an inlet, an outlet and a heat exchange chamber between the inlet and the outlet. The hydraulic motor further comprises a plurality of vanes adapted to divide the heat exchange chamber into mutually hermetically separated compartments, the plurality of vanes being configured to move only according to a predetermined direction when in operation. The waste heat recovery unit is able to absorb heat of low grade or low temperature, having temperature range from about 0°C (i.e. degree Celsius) to 200°C or higher depending on temperature limit of relevant material deployed. Hence, the waste heat recovery unit may be alternatively called as ambient heat engine or ambient heat generator. The hydraulic motor is configured or designed to receive one or more refrigerants or heat transfer fluids in order to operate. For example, the hydraulic motor receives carbon dioxide (CO2) in liquid form, which is circulated around the waste heat recovery unit repeatedly or continuously. The hydraulic motor is also known as rotary vane motor because these vanes are implemented.

[0010] The hydraulic motor can comprise a rotary drum that has the plurality of vanes extending from a cylindrical surface of the rotary drum. Both the plurality of vanes and the drum are enclosed by a barrel of the hydraulic motor. Each of the vanes is radially extendable from a rotation axis of the drum. Bottoms of the vanes are resiliently supported (e.g. by springs) such that tips of the vanes touch an inner surface of the barrel continually, even when the drum rotates. For example, the drum and the barrel are off-centered (i.e. not coaxial), although the barrel encloses the drum and the vanes. In one embodiment, at one side, the drum touches the inner surface of the barrel, whilst a gap exists at an opposite of the drum between the drum and the barrel. Whether in movement or at rest, the vanes extend from the drum and divide the gap between the drum and the barrel into mutually separated compartments for receiving the one or more refrigerants or heat transfer fluids. [001 1 ] The two or more of the mutually isolated compartments may have substantially the similar volume, which exist between the drum and the barrel. For example, the drum is circular, whilst the inner surface of barrel is not circular. The compartments with uniform volumes are formed between a portion of the inner surface and the drum. Alternatively, the rotary vane motor comprises compartments that have volumes gradually increasing clockwise or progressively reducing clockwise. The change of volume is a reverse direction may also be true when necessary. In practice, it is more beneficial to have the compartments with the same and then increasing volume in a direction of the refrigerant(s) or heat transfer fluid(s) flow. [0012] The hydraulic motor can further comprise a stopper, whether connected to a shaft or the drum of the hydraulic motor, for preventing reversal movement of the vanes with respect to the predetermined direction. The stopper is a mechanical device, an electrical device or a combination of both. For example, the stopper comprises a ratchet and pawl device. The stopper can further include a worm drive which includes a worm meshes with a worm gear. Many mechanical or electrical alternatives are feasible acting as the stopper in order to prevent reversal rotation of the drum.

[0013] The hydraulic motor may be made of material capable of withstanding pressure of at least 30 bars and/or temperature of 150-degree Kelvin (K). When using liquid carbon dioxide at low temperature (e.g. -57°C at above 5.1 atmospheric pressure), the hydraulic motor is able to keep its structural integrity and strength without comprising its performance. For example, the hydraulic motor has one or more components that are made of composite material, alloy, polymer or combination of any of these materials. In one case, both the barrel and the drum are made of Polytetrafluoroethylene (PTFE), Polyoxymethylene (POM) or Polycaprolactam (Cast Nylon 6). Hence, barrel and the drum offer low friction loss, but have high strength at low temperature.

[0014] The waste heat recovery unit can further comprise an exit check valve that is connected to the outlet for preventing backflow of a heat transfer fluid of the waste heat recovery unit. The check valve is alternatively known as clack valve, non-return valve or one-way valve that normally allows fluid (liquid or gas) to flow through the check valve in only one predetermined direction. The check valve is able to be implemented at low cost with good reliability.

[0015] The waste heat recovery unit may further comprise an entry check valve that is connected to the inlet for preventing the backflow of the heat transfer fluid of the waste heat recovery unit. The entry valve provides another control valve that guides movement of the refrigerant(s) or heat transfer fluid(s) according to the predetermined direction. [0016] The waste heat recovery unit can further comprise a high pressure reservoir that is connected to the outlet. The high pressure reservoir is able to hold the refrigerant(s) or heat transfer fluid(s) and stabilize its/their pressure so that the refrigerant(s) or heat transfer fluid(s) possess uniform temperature at a substantially the same phase (e.g. liquid phase or super-critical phase).

[0017] The waste heat recovery unit may preferably comprise an expander or condenser that is connected between the outlet and the inlet. The expander or condenser is able to increase volume of the one or more refrigerants adiabatically, by heating or other means, and eventually make it a very cold liquid. For example, in the process of making dry ice (solid CO2) high pressure CO2 expands to low pressure and becomes solid. In contrast, embodiments of the application enable liquid carbon dioxide to be formed by expansion. Preferably, the expander comprises a Joule- Thomson device that utilizes an adiabatic process to expand the one or more refrigerants. The Joule-Thomson device does not generate waste heat to the ambient environment.

[0018] The waste heat recovery unit can optionally comprise a compressor that is connected to the hydraulic motor at the inlet, the outlet or both, which is a component of waste heat recovery unit in forming a complete loop of circulation. If the refrigerants exit below the high pressure cylinder pressure. The compressor is able to raise pressure. The compressor is further able to reduce volume of the one or more refrigerants. The compressor includes a dynamic type or a positive displacement type. For example, the positive displacement type of compressor is a rotary compressor or a reciprocating compressor. The dynamic type of compressor is a centrifugal compressor or an axial compressor.

[0019] The waste heat recovery unit may further comprise one or more conduits that are exposed to an ambient environment of the waste heat recovery unit. Hence, the one or more conduits become one or more heat exchangers, or parts of a heat exchanger. The one or more conduits provide effective heat supply to the waste recovery unit so that the waste heat recovery unit is able to operate with high efficiency. For example, the one or more conduits include shell and tube heat exchanger, plate heat exchanger, plate and shell heat exchanger, adiabatic wheel heat exchanger, plate fin heat exchanger, pillow plate heat exchanger, fluid heat exchangers, dynamic scraped surface heat exchanger, phase-change heat exchangers, direct contact heat exchangers, and microchannel heat exchangers. [0020] According a second aspect, the present application provides a method for using a waste heat recovery unit. The method comprises a first of receiving a heat transfer fluid at an inlet of a hydraulic motor of the waste heat recovery unit; a second step of introducing the heat transfer fluid into at least one compartment of the hydraulic motor; a third step of heating the heat transfer fluid at the at least one compartment (for increasing pressure or volume of the heat transfer fluid in the at least one compartment); a fourth step of allowing expansion of the heat transfer fluid at the one or more compartments for propelling the hydraulic motor in a predetermined direction; a fifth step of discharging the heat transfer fluid at an outlet of the hydraulic motor; and a sixth step of routing the heat transfer fluid from the outlet back to the inlet. Some of these steps may be changed in sequence. Once filled with one or more refrigerants or heat transfer fluids, the waste heat recovery unit is able to receive waste heat for heating the one or more refrigerants so that the one or more refrigerants are able to be circulated within the waste heat recovery unit, resulting continuous operation. In one embodiment, the refrigerant or heat transfer fluid is carbon dioxide (CO2), which may be operated in liquid phase within the waste heat recovery unit.

[0021 ] Since carbon dioxide can maintain its liquid phase at temperature about - 70~30°C at pressure of about 6-1 ,500 bar, the waste heat recovery unit is able to absorb heat at -30~50°C. For example, the waste heat recovery unit can absorb ambient heat in summer, provide useful kinetic energy (e.g. motor rotation), and discharge the absorbed heat to underground water. In one case, the heating of the heat transfer fluid comprises a step of freezing waste water such that contaminants are removed from freshly frozen water. The waste heat recovery unit thus can operate as a clean water generator.

[0022] The method can further comprise a step of enclosing the heat transfer fluid by a drum having radially movable vanes for separating the heat transfer fluid into multiple pieces of the one or more compartments with similar volumes. The heat transfer fluid (also known as refrigerant) is hermetically concealed and circulated within the waste heat recovery unit, without being dissipated. For example, a single injection of carbon dioxide may last years of operation of the waste heat recovery unit.

[0023] The method may additionally comprise a step of hermetically sealing the multiple pieces of the one or more compartments. The separation of multiple compartments prevents escape of heat transfer fluid from one compartment to another, making pressure increase with the relevant compartment possible. Accordingly, a refrigerant is able to increase its pressure with a hermetically sealed compartment, and pushes vanes of the compartments to the predetermined direction of movement.

[0024] The step of receiving of the heat transfer fluid can comprise a step of injecting carbon dioxide. Carbon dioxide can be injected into the waste heat recovery unit through one of the check valves such that the carbon dioxide does not escape after filing. Foreign gases, such as air, is repelled and forced out of the waste heat recovery unit when filing carbon dioxide because the carbon dioxide has a higher mass density than that of the air.

[0025] Alternatively speaking as according to another aspect of the invention, the present application provides a cold CO2 Hydraulic Engine powered by pressurized flow of cold liquid carbon dioxide (CO2), which comprises a rotating device with a chamber. The chamber has cross sectional areas of substantially the same size, which are substantially perpendicular to a direction of travelling of the carbon dioxide. When progressing from an inlet to an outlet of the cold CO2 Hydraulic Engine, the carbon dioxide increases its pressure progressively from the inlet to the outlet because the chamber is subjected to heating by external medium. Hence, at the outlet, the liquid carbon dioxide expands its volume, being continuously in the liquid phase.

[0026] Pressure of the carbon dioxide at the outlet is higher than that at the inlet. The carbon dioxide fluid is looped back to the inlet of the rotating device through a series of heat exchangers and expander(s)/condenser to ensure that the cold liquid carbon dioxide at the inlet of the rotating device is much lower than zero degree Celsius. The chamber of the rotating device has a constant cross section area from the inlet to the outlet. The rotating device is made of Polytetrafluoroethylene (PTFE), Polyoxymethylene (POM) or Polycaprolactam (Cast Nylon 6), which are polymer. In use, the carbon dioxide in the chamber remains in liquid phase and increases in pressure when progressing from the inlet to the outlet. After exiting the rotating device at the outlet, the carbon dioxide is able to be channeled back to the inlet to become very cold liquid at about -50 to -10 degrees Celsius, which forms a closed loop with the rotating device.

[0027] With the chamber of constant cross-section and a fixed mass of the carbon dioxide, a small amount of thermal energy of low temperature from an external ambient can raise temperature of the carbon dioxide at the chamber such as by five (05) degree Celsius, which can cause pressure of the carbon dioxide to go up to about 100 bars or more, and remains in liquid state at the outlet. In contrast, water with the same mass or volume requires about two (02) times more thermal energy at higher temperature to raise water temperature by five (05) degree Celsius. Heating to the liquid carbon dioxide in the chamber causes the liquid carbon dioxide to increase in pressure, which results in mechanical movement and conversion to kinetic energy. The rotating device provides efficient and advantageous mechanism to convert otherwise waste heat to be useful energy. In the rotating device, the liquid carbon dioxide at the inlet of the rotating device is very cold temperature, for example, at around minus 60 degree Celsius and slightly above the freezing point of carbon dioxide. The cold liquid carbon dioxide at the outlet of the rotating device remains cold, after its temperature being raised by five (05) to fifteen (15) degree Celsius. Hence, the external ambient environment is able to heat up the liquid carbon dioxide even though temperature of the external ambient environment is from minus fifty degrees Celsius (-40°C) to zero degree Celsius (0°C). In other words, the cold CO2 Hydraulic Engine can work by harvesting from low grade heat like ambient heat even at night time, without feedstock cost. Waste heat source with high temperature will enable the Cold CO2 Hydraulic Engine to deliver higher output. As temperature of the liquid carbon dioxide at the outlet of the rotating device may be still below zero degree Celsius, the rotating device or the Cold CO2 Hydraulic Engine can be used for crystallizing or freezing freshwater out of the atmosphere, waste or seawater. Frozen freshwater can be subsequently used for cooling or air-conditioning buildings in summer or tropical regions. When used in hot climate, the external ambient environment will warm up the liquid carbon dioxide to be around twenty (20) degree Celsius such that the liquid carbon dioxide at the inlet of the rotating device has low pressure and becomes cold. Depending on pressure and temperature of the carbon dioxide, the liquid carbon dioxide experiences a controlled process of expansion and contraction such that the carbon dioxide does not form dry ice or gas forms of carbon dioxide. [0028] If receiving heat from a high temperature source, such as from decomposition process of waste disposal by plasma gasification, high temperature thermal energy can be recovered for the Cold CO2 (i.e. carbon dioxide) Hydraulic Engine to deliver useful works, similar to that of electricity generation. The Cold Hydraulic CO2 Engine is a mechanical driver for electricity, hot and cold fresh water generation with wet waste disposal, which can make any place livable in a sustainable way without pollution and depleting natural resources. The Cold CO2 Hydraulic Engine is scalable and portable for powering propulsion of small to big vehicles.

[0029] The Cold CO2 Hydraulic Engine further comprise one or more check (non- return) valves that are connected in the closed loop for preventing backflow of the working fluid. A "unidirectional" gear like ratchet wheel with pawl on a drive shaft of the Cold Carbon Dioxide Hydraulic Engine will ensure one directional mechanical rotation. [0030] According to yet another aspect of the invention, the application provides a method for using a Cold CO2 Hydraulic Engine that comprises a step of reducing temperature of a heat transfer fluid to be lower than an ambient temperature of the Cold CO2 Hydraulic Engine; another step of absorbing the heat by the heat transfer fluid of the Cold CO2 Hydraulic Engine; and a further step of converting one or more portions of the heat to displacement as output. Some of these steps may be changed in sequence, whilst all of these steps can be cyclically or continuously repeated for operating the Cold CO2 Hydraulic Engine. The Cold Hydraulic CO2 Engine is alternatively known as the waste heat recovery unit when using carbon dioxide as the refrigerant. [0031 ] The method can further comprise a step of increasing temperature of the heat transfer fluid after the converting the one or more portions of the heat to displacement as output. In other words, the fluid (i.e. heat transfer medium) can absorb thermal energy from waste heat, sunlight, furnace, plasma gasifying devices, hot spring or any other natural or industrial heat sources for converting the thermal energy to desired energy (e.g. electrical, mechanical). The method can be applied in diverse types of the industries, and further adapted to individual needs or specification. [0032] The step of increasing temperature of the heat transfer fluid additionally may comprise a step of absorbing thermal energy by the heat transfer fluid from the ambient environment. Since ambient environment provides an almost inexhaustible source of energy, the Cold CO2 Hydraulic Engine does not require transportation of "feedstock fuel" to the Cold CO2 Hydraulic Engine, or cause environmental damage. Instead, the Cold CO2 Hydraulic Engine reduces temperature of its ambient environment, and provides an air-conditioner at almost no running cost.

[0033] The Cold Hydraulic CO2 Engine is scalable for use as battery charger in an electric vehicle by driving a generator. Alternatively, the Cold Hydraulic CO2 Engine provides kinetic energy that drives powertrain of a vehicle directly. The Cold Hydraulic CO2 Engine of high capacity is able act as energy source of power plants. The heat exchanger which is attached to the motor will absorb the ambient heat or from other heat source. The Cold CO2 Hydraulic Engine does not generate waste heat. The Cold CO2 Hydraulic Engine has the body temperature lower than ambient temperature such that the working medium chills its environment.

[0034] The accompanying figure (Fig. or FIGURE) illustrates one or more embodiments of the relevant invention and serve to explain principles of the disclosed embodiments. It is to be understood, however, that the figure has been presented for purposes of illustration only, and not for defining limits of relevant inventions. Particularly, Fig. 1 illustrates a waste heat recovery unit. Exemplary, non- limiting embodiments of the present application will now be described with references to the figure. [0035] Figs. 1 relates an embodiment of the invention. Particularly, Fig. 1 illustrates a waste heat recovery unit 20. The waste heat recovery unit 20 comprises a cold liquefier cylinder 22, an entry check valve 51 , a rotary vane motor 26, an exit check valve 71 , a high pressure reservoir 23, a run check valve 31 and a Joule-Thomson device 41 , which are sequentially connected together clockwise (CW) by a heat transfer tube or tubing 10. Optionally, a compressor (not shown) can be connected at exit check valve 71 before the high pressure cylinder 23. The heat transfer tube 10 passes through some external heat exchangers (not shown). An internal heat exchanger 27 is embedded in the rotary vane motor 26. The internal heat exchanger 27 has a heat fluid inlet 28 and a heat fluid exit outlet 29 which is further connected back to the heat fluid inlet 28 via a heat fluid tube 21 . The heat fluid tube 21 passes through external heat sources (not shown) to gather heat energy for powering the waste heat recovery unit 20. [0036] In a first step running or using the waste heat recovery unit 20, a high pressure CO2 (i.e. carbon dioxide) around 70 bars at temperature 30 degrees Celsius from an external source is fed into the high pressure reservoir 23 via its inlet 82. The temperature and pressure of the carbon dioxide (i.e. CO2) is affected by ambient temperature of the waste heat recovery unit 20. When an inlet cap 83 is tightened, pushing an inlet cap pin 84 will open the inlet check valve 81 . Once the inlet check valve 81 is opened, the high pressure CO2 fills the chamber of high pressure reservoir 23. Upon completion of filing, the high pressure CO2 is contained within by the exit check valve 71 and run check valve 31 . [0037] An exhaust cap 63 is typically loosened when the waste heat recovery unit 20 is in operation. For an initial start-to-run the waste heat recovery unit 20, the exhaust check valve 61 is opened by tightening the exhaust cap 63, pushing its exhaust cap pin 64, exposing the chamber of the rotary vane motor 26 to the ambient environment via an exhaust outlet 62.

[0038] A run cap 33 is tightened when the waste heat recovery unit 20 is set to run. Subsequently, by pushing the run cap pin 34, the run check valve 31 is opened. The high pressure CO2 then flows out towards the exhaust outlet 62. As the high pressure CO2 flows through the run check valve 31 , its pressure drops as well as its temperature. Since the Joule-Thomson device 41 provides around 0.9K temperature drop per bar at about thirty (30) degrees Celsius and 70 bars, the CO2 reaches the Joule-Thomson device 41 and its pressure is around 60 bars with its temperature dropping to 21 degrees Celsius, having the Joule-Thomson index about 1 K temperature drop per bar (pressure change). As the CO2 flow goes through the Joule-Thomson Device 41 , the CO2 pressure drops further by 40 bars to around 20 bars, the CO2 temperature drops further to minus 19 degree Celsius and its density becomes around 1 ,000kg/m ³ which is a liquid state formed in the cold liquefier cylinder 22.

[0039] Initially air and then some CO2 will escape out to the ambient environment through the exhaust outlet 62 causing the rotary vane motor 26 to rotate. The cold liquid CO2 is then being sucked in by the rotary vanes motor 26, filling the chambers 24 divided by movable vanes 25 of the rotary vanes motor 26. The rotary vanes motor 26 has eighteen (18) vanes, effectively divide a circumference of the rotary vanes motor 26 into eighteen (18) sections. When enclosed by a barrel 66 of the rotary vanes motor 26. The number of vanes 25 can vary if required.

[0040] According to Figure 1 , the eighteen vanes 25 are radially movable around a drum 68 on a driving shaft 70 of the rotary vanes motor 26. The drum 68 is fixed onto the driving shaft 70 such that the drum 68 and the barrel 66 are off-centered. Figure 1 shows that the drum 68 is shifted towards top of the barrel 66, whilst the barrel 66 encloses the drum 68. The radially movable vanes 25 divides space between the barrel 66 and the drum 68 into eighteen (18) mutually separated compartments. When fully extended, the eighteen (18) vanes 25 cause the compartments 24 to be hermetically sealed between each other. A top portion of the space has four (4) of these eighteen (18) chambers, which has substantially zero volume respectively. In contrast, there are eight (8) compartments at a bottom side of the drum 68, which has substantially the same or constant volume. An inner surface of the barrel 66 is non- circular, which encloses the drum 68. The vanes 25 constantly touches the inner surface of the barrel 66 as the drum 66 and the driving shaft 70 rotate. Moreover, the vanes 25 can easily retract and extend within slots of the drum 66, providing no friction or negligible hindrance to rotation of the drum 66 or the driving shaft 70. [0041 ] In use, the lower eight (8) compartments 24 of the rotary vanes motor 26 are filled with cold liquid CO2, which propel the vanes 25 to move toward the exhaust check valve 61 . As the compartments 24 at lower portion of the rotary vanes motor 26 pass over a heated section where the internal heat exchanger 27 is embedded in the rotary vane motor 26, carbon dioxide in these mutually hermetically sealed compartments 24 increases in pressure, which causes both the drum 68 and the driving shaft 70 move clockwise. The internal heat exchange 27 where a heated fluid flows, bringing in via the heat fluid inlet 28 and exits out via the heat fluid exit outlet 29. The colder heat fluid goes through the heat fluid tube 21 where the colder heat fluid is being heated up by external heat sources, which the heat fluid tube 21 receive. One of the basic heat source is ambient heat or low grade waste heat from industrial or other waste sources. The heat fluid returns to the heat fluid inlet 28 by bringing the thermal energy require to raise the Cold liquid CO2 temperature and hence its pressure. The heat fluid optionally is air, liquid water, steam or any fluid that the rotary vane motor 26 housing can handle.

[0042] After a few seconds of CO2 flowing out of the exhaust outlet 62, the exhaust cap 63 is loosened to release the exhaust pin 64 and to shut the opening of the exhaust check valve 61 . The liquid CO2 at the exit of the rotary vane motor 26 now has pressure higher than the pressure in the high pressure reservoir 23 to overcome the exit check valve 71 and flows into the high pressure reservoir 23. If the liquid CO2 is discharged to below 5.1 bars at exit, then optionally a compressor is used to pump carbon dioxide pressure up to flow into the high pressure reservoir 23. The external CO2 source can be removed after loosening the inlet cap 83.

[0043] The cold liquid CO2 of higher temperature in the high pressure reservoir 23 is then directed through the earlier path to reach the inlet of the rotary motor 26. As temperature of the carbon dioxide is colder than its initial temperature when firstly started, the cold liquid CO2 is warmed up by having the tube 10 which carrying the cold liquid CO2, passing through devices (not shown), which can serve other applications. Devices like fans blowing ambient air to the tube 10 are able to transfer heat to the tube 10 and make the ambient air cooler, similar to that of an air- conditioner. Since the cold liquid CO2 operates carbon dioxide below zero degree Celsius, the cold liquid CO2 can be warmed up by crystallizing or freezing freshwater from seawater or wastewater.

[0044] The liquid CO2 formed in the cold liquefier cylinder 22 now becomes very cold at minus 48 degrees Celsius and has pressure around 20 bars. The liquid CO2 density is around 1 150kg/m ³ , enthalpy about 95kj/kg, and entropy about 0.58J/g ^* K. As the cold liquid CO2 fills into the compartments 24 and moves toward an exit of the rotary vane motor 26, the cold carbon dioxide picks up heat (thermal energy) to raise its temperature by five (05) degrees C to minus forty-three (43) degree Celsius which the enthalpy is around 108kj/kg, entropy around 0.62J/g ^* K and its pressure increased to about 105 bars. The change in enthalpy is about 13kj/Kg and the change in entropy is 0.04J/g ^* K. The increased pressure of the carbon dioxide at the compartments 24 of the waste heat recovery unit 20 is prevented from moving backward to the inlet of the rotary vane motor 26 by a ratchet wheel and pawl system (not shown in Figure 1 ) mounted on the shaft 70 of the rotary vane motor 26. The vanes 25 of the rotary vane motor 26 can only move forward clockwise to the exit to release pressurized carbon dioxide to the high pressure reservoir 23. The cold liquid CO2 is warmed up through the tube 10 to reach a suitable value of temperature and pressure before the Joule-Thomson device 41 to allow the carbon dioxide to form liquid CO2 at about minus forty-eight (48) degrees Celsius and around 10 to 20 bars. Liquid carbon dioxide is subsequently drawn into the rotary vane motor 26 by the suction action of the moving vanes. The cycle is then repeated. Alternatively, carbon dioxide departing from the Joule-Thomson device 41 may be directly fed into the rotary vane motor 26.

[0045] The cold CO2 temperature of minus 43 degrees C is relatively cold for performing work. In a second embodiment, instead of going to the high pressure reservoir 23 directly, the carbon dioxide can be routed directly to an inlet of a rotary vane motor 26 of another waste heat recovery unit 20. The cold CO2 pressure can drop down to 75 bars with higher temperature after driving the shaft 70 and exit out of the rotary vane motor 26 to the high pressure reservoir 23 where the carbon dioxide is routed via the tube 10 back to the cold liquefier cylinder 22 of the first Waste heat recovery unit 20. The cold liquid CO2 is formed back to very cold temperature as cycle repeats. A compressor is optionally included, which is connected between the cold liquefier cylinder 22 to the rotary vane motor 26. The compressor propels the carbon dioxide and inject the carbon dioxide into the rotary vane motor 26.

[0046] In the application, unless specified otherwise, the terms "comprising", "comprise", and grammatical variants thereof, intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, non-explicitly recited elements.

[0047] As used herein, the term "about", in the context of concentrations of components of the formulations, typically means +/- 5% of the stated value, more typically +/- 4% of the stated value, more typically +/- 3% of the stated value, more typically, +/- 2% of the stated value, even more typically +/- 1 % of the stated value, and even more typically +/- 0.5% of the stated value. [0048] Throughout this disclosure, certain embodiments may be disclosed in a range format. The description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1 , 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0049] It will be apparent that various other modifications and adaptations of the application will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the application and it is intended that all such modifications and adaptations come within the scope of the appended claims.