WO2013059695A1

WO2013059695A1 - Turbine drive absorption system

Info

Publication number: WO2013059695A1
Application number: PCT/US2012/061159
Authority: WO
Inventors: Timothy J. Held
Original assignee: Echogen Power Systems, Llc
Priority date: 2011-10-21
Filing date: 2012-10-19
Publication date: 2013-04-25

Abstract

Embodiments of the disclosure provide a heat pump system having a pump configured to transfer a solution from a first reservoir and into a second reservoir. The solution contains a refrigerant (e.g., CO₂) and an absorbent, whereas the absorbent at least partially absorbs the refrigerant in the first reservoir and at least partially desorbs the refrigerant in the second reservoir to generate a gaseous refrigerant component. The system further contains a supercritical precooler fluidly coupled to the second reservoir and configured to extract thermal energy from the refrigerant component in a supercritical state, an expansion valve in fluid communication with the supercritical precooler and configured to reduce pressure and temperature of the refrigerant component. The system also contains a fluid turbine fluidly coupled to the second reservoir and configured to receive the solution and extract at least a portion of residual thermal energy therefrom.

Description

Turbine Drive Absorption System

Gross-Reference to Related Applications

[0001] This application claims the benefit of U.S. Appl. No. 81/550,017, filed October 21 , 2011 , which is hereby incorporated by reference.

Background

[0002] A heat pump is a device for transferring thermal energy from a heat source to a heat sink in a direction which is opposite to the direction of spontaneous heat flow using mechanical work or a high-temperature heat source. In contrast to a refrigerator, which only removes heat from a system, heat pumps are used to deliver either heating or cooling to a system. Thus, in at least one application, a refrigerator may be considered a type of heat pump.

[0003] The inherent feature of a heat pump is to transport/move thermal energy from a heat source to a heat sink. Consequently, the use of the term "heat pump" is broadly applied to systems that transport thermal energy from one entha!py/entropy state to another. The utilization of heat pumps is not restricted to the generation of heating or cooling, but also for the intrinsic movement of thermal energy in virtually any thermodynamic cycle including means to convert such thermal energy into power generation (e.g., electrical or mechanical energy).

[0004] In absorption heat pumps, a liquid absorbent absorbs a vapor refrigerant to generate a liquid solution. When the combined solution is pressurized and heated further, the refrigerant is expelled from the solution. When the refrigerant is pre-cooled and expanded to a low pressure, the refrigerant provides cooling or heat to an external system. The low-pressure refrigerant is then recombined with the low-pressure, depleted solution to complete the cycle.

[0005] Many current absorption heat pumps and refrigerators use water as the absorbent and ammonia as the refrigerant. In other applications, water is combined with lithium bromide (LiBr) to create the solution. These two absorption solutions, however, suffer from certain drawbacks. For example, the water-ammonia solution raises security concerns in view of the toxicity and f!ammability of the ammonia counterpart. And because of the corrosive nature of LiBr in combination with a low pressure operation, small leaks in the system can develop, thereby creating potentially dangerous contamination situations. Moreover, the tendency of the LiBr solution to crystallize can present clogging problems. Additionally, circulating the solutions at very low pressures is often impossible due to the freezing point of water.

[0006] Other absorption processes have been proposed, but each involve working fluids that are toxic, flammable, ozone-depleting, or have high atmospheric green house effects. Therefore, what is needed is an environmentally-friendly cycle that uses a nontoxic, non-corrosive working fluid with a positive working pressure, where the cycle takes advantage of unused energy in the system to increase overall system efficiency.

Summary

[0007] Embodiments of the disclosure may provide a heat pump system. The system may include a first reservoir in fluid communication with a second reservoir. A pump may be fluidly coupled to the first and second reservoirs and configured to draw a solution from the first reservoir and to pump, flow, or otherwise transfer the solution into the second reservoir. The solution may include a combination or mixture of a refrigerant and an absorbent, and the absorbent may at least partially absorb the refrigerant in the first reservoir and at least partially desorb the refrigerant in the second reservoir to generate a refrigerant component (e.g. , gaseous CO₂). A supercritical precooler may be fluidly coupled to the second reservoir and configured to receive and to extract thermal energy as heat from the refrigerant component while the refrigerant component is in a supercritical state (e.g. , SC-CO₂). An expansion valve may be in fluid communication with the supercritical precooler and configured to reduce the pressure and temperature of the refrigerant component discharged from the supercritical precooler. A conduit may be fluidly communicating the expansion valve with the first reservoir and configured to direct the refrigerant component discharged from the expansion valve into the first reservoir. A fluid turbine may be fluidly coupled to the second reservoir and configured to receive the solution and extract at least a portion of residual thermal energy therefrom.

[0008] Embodiments of the disclosure may also provide a method for delivering thermal energy as heat. The method may include increasing a pressure of a solution with a pump. The solution may be drawn from a first reservoir and include a combination or mixture of carbon dioxide and an absorbent. A temperature of the solution may be increased in a first heat exchanger fluid!y coupled to the pump and a second reservoir. At least a portion of the carbon dioxide may be boiled off from the solution in the second reservoir to generate a refrigerant component containing carbon dioxide in a gaseous state. The refrigerant component may be cooled to have a supercritical state with a supercritical precooler while extracting heat from the refrigerant component. The supercritical precooler is generally in fluid communication with the second reservoir. The refrigerant component may be expanded in an expansion valve f!uidly coupled to the supercritical precooler. The refrigerant component discharged from the expansion valve may be directed into the first reservoir. A portion of the solution from the second reservoir may be received in a fluid turbine fluid!y coupled to the second reservoir. Energy from the portion of the solution may be extracted with the fluid turbine.

[0009] Embodiments of the disclosure may further provide a heat pump system. The system may include a pump f!uidly coupled to a first reservoir and configured to draw a solution from the first reservoir and increase a pressure of the solution. The solution may include a combination or mixture of a refrigerant and an absorbent. A first heat exchanger may be fluidly coupled to the pump and configured to heat the solution. A second reservoir may be fluidly coupled to the first heat exchanger and configured to boil the solution to at least partially desorb the refrigerant from the absorbent, thereby generating a refrigerant component. A supercritical precooler may be fluidly coupled to the second reservoir and configured to receive and to extract thermal energy as heat from the refrigerant component while the refrigerant component is in a supercritical state. A second heat exchanger may be fluidly coupled to the supercritical precooler and configured to decrease a temperature of the refrigerant component discharged from the supercritical precooler. An expansion valve may be fluidly coupled to the second heat exchanger and configured to reduce the pressure and temperature of the refrigerant component discharged from the second heat exchanger. One or more conduits may be fluidly communicating the expansion valve with the first reservoir to direct the refrigerant component discharged from the expansion valve into the first reservoir. A fluid turbine may be fluidly coupled to the second reservoir and configured to receive a portion of the solution in the second reservoir and extract energy therefrom. Brief Description of the Drawings

[0010] The present disclosure is best understood from the foilowing detailed description when read with the accompanying Figures, It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0011] Figure 1 illustrates an exemplary heat pump system, according to one or more embodiments disclosed herein.

[0012] Figure 2 illustrates a flowchart of a method for delivering thermal energy as heat and extracting power therefrom, according to one or more embodiments disclosed herein.

Detailed Description

[0013] It is to be understood that the present disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure. However, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure. [0014] Additionally, certain terms are used throughout the present disclosure and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the present disclosure and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to". All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B", unless otherwise expressly specified herein.

[0015] Figure 1 illustrates a heat pump system 100, according to one or more embodiments described. Although the term "heat pump" is used to characterize the heat pump system 100, it will be appreciated that the designation of refrigerator, air conditioner, water heater, trigeneration, and cogeneration could be substituted without changing the operation of the heat pump system 100. The heat pump system 100 may include a first reservoir 102 in fluid communication with a second reservoir 104 and a solution that is circulated throughout the heat pump system 100. The first reservoir 102 may be an absorber configured to maintain or otherwise house the solution in a first state 106 and the second reservoir 104 may be a desorber or "evaporator" configured to maintain or otherwise house the solution in a second state 108.

[0018] The solution may include a combination or mixture of a refrigerant and an absorbent, although the first and second states 106, 108 may have varying quantities and/or concentrations of the refrigerant and/or absorbent, as will be described below. An exemplary refrigerant may include fluid that expands into a gas within the second reservoir 104. In one embodiment, a suitable refrigerant may be ammonia. In other embodiments, the refrigerant may be carbon dioxide (CO2), which has reduced toxicity and perceived safety. In operation of the heat pump system 100, the refrigerant will be capable of operating within the supercritical temperature/pressure and/or the subcritical temperature/pressure {e.g., transcritical ranges), as determined by the specific refrigerant.

[0017] The absorbent may be configured to absorb the refrigerant to either increase the temperature lift of a particular thermal source (e.g., transform a relatively low temperature fluid to a higher temperature), or to provide cooling. Desorption in the second reservoir 104 is effectively the process at which the refrigerant separates from the absorbent. An exemplary absorbent may be selected from alcohols (e.g., methyl or ethyl alcohol), acetates, ketones, ionic liquids, ionic solids, electride solutions, alkalide solutions, derivatives thereof, or combinations thereof. Ionic liquids may be utilized as environmentally-friendly solvents. Electride solutions and alkalide solutions may be utilized as chemical reducing agents and chemical oxidizing agents, respectively. Ionic liquids have very low, if not negligible, vapor pressure, and are therefore compatible with supercritical carbon dioxide {SC-CO2). The use of SC-CO2 in ionic liquids yields excellent carbon dioxide solubility and simple phase separation due to the resulting solution's classification as a partially miscible fluid combination. At least two acetates that may be suitable absorbents include isobutyl acetate and amyl acetate, which absorb carbon dioxide well as compared to alcohols and exhibit a relatively high normal boiling point and low toxicity.

[0018] In one embodiment, the solution circulated throughout the heat pump system 100 may be a combination or mixture of an alcohol absorbent and a carbon dioxide refrigerant. In the first state 106, the solution in the first reservoir 102 may be maintained at a temperature of about 100°F (about 37.8°C) and a pressure of about 560 pounds per square inch (psi) (about 38.1 atm). The solution in the first state 106 may be characterized as a "strong" solution in that there may be a relatively higher concentration of carbon dioxide dissolved in the alcohol absorbent. On the other hand, the solution in the second state 108 may be characterized as a "weak" solution having a relatively lower concentration of carbon dioxide, as will be discussed below. It should be noted that any numerical values provided herein are intended for illustrative purposes only and the various embodiments discussed are not to be considered limiting to any particular temperature or pressure range specifically defined.

[0019] The solution in the first state 106 may be directed through a conduit 1 10 to a pump 1 12 fluidly coupled to the first reservoir 102. The pump 1 12 may be configured to elevate the pressure of the solution to about 1 ,400 psi (about 95.3 atm). A conduit 114 may fluidly couple the pump 112 to a first heat exchanger 1 16. The first heat exchanger 1 16 may be any device adapted to transfer thermal energy between one or more fluids such as, but not limited to, a direct contact heat exchanger or one or more printed circuit heat exchange panels. Such heat exchangers and/or panels are known in the art, and are described, for example, in U.S. Pat. Nos. 6,921 ,518; 7,022,294; and 7,033,553, the contents of which are incorporated herein by reference to the extent consistent with the present disclosure.

[0020] In operation, the first heat exchanger 116 may increase the temperature of the solution discharged from the pump 1 12. in one embodiment, the temperature of the solution is increased to about 275°F (about 135°C). The increased-temperature solution may then be injected or otherwise directed into the second reservoir 104 via a conduit 1 18, thereby being combined with or otherwise forming an integral part of the solution in a second state 108.

[0021] The second reservoir 104, or desorber, may be configured to extract or otherwise desorb the refrigerant (e.g., CO;?) from the solution. To accomplish this, heat Q-_m may be added as needed to the second reservoir 104 to boil off or evaporate the refrigerant component, thereby generating a refrigerant component 120 (e.g., CO2 gas) and leaving a weak solution in the second state 108. The refrigerant component 120 may be boiled off from the absorbent at about 275°F (about 135°C) and about 1 ,400 psi (about 95.3 atm), but may be boiled off at higher or lower temperatures and pressures without departing from the scope of the disclosure.

[0022] The extracted refrigerant component 120 may then be directed through a conduit 122 which fluidly communicates the top of the second reservoir 104 with the first heat exchanger 1 16. The thermal energy in the refrigerant component 120 may be used to increase the temperature of the solution discharged from the pump 1 12 while passing through the first heat exchanger 1 16. In one embodiment, the refrigerant component 120 loses thermal energy such that the refrigerant component 120 is discharged from the first heat exchanger 116 at a temperature of about 175°F (about 79.4°C), and yet the pressure may remain approximately the same at about 1 ,400 psi (about 95.3 atm).

[0023] The refrigerant component 120 may then be conveyed by conduit 124 to a supercritical precooler 126 configured to extract thermal energy as heat from the refrigerant component 120. The extracted heat Q_out may be vented or provided to an external system or mechanical device configured to utilize the heat Q_ou} for, among other applications, general heating purposes or power generation. In one embodiment, the supercritical precooler 126 may cool the refrigerant component 120 from about 175°F to about 100°F (from about 79.4°C to about 37.8°C). The temperature reduction of the refrigerant component 120 occurs while the refrigerant component 120 is in a supercritical state, thereby enabling the heat Q_out to be removed across a significant temperature range instead of at a single condenser temperature.

[0024] At least one advantage of using carbon dioxide as the refrigerant and subsequent refrigerant component 120 is the capacity to pre-coo! carbon dioxide over a much larger supercritical temperature range compared to common refrigerants, such as hydrofluorocarbons (HFCs) (e.g., 1.1 ,1 ,2-tetrafiuoroethane (R134a) or 1 ,1 ,1 ,3,3- pentafluoropropane (R245fa)), which must be condensed at one specific temperature for a given pressure. Carbon dioxide, however, is capable of being cooled in the supercritical regime, such as within a temperature range from about 100°F to about 200°F (from about 37.8°C to about 93.3°C), depending upon the state of the refrigerant component 120 exiting the first heat exchanger 116. Consequently, thermal energy may be removed from the carbon dioxide continuously within this range rather than limiting the heat extraction to only a small range of temperatures. Therefore, a significantly reduced structural mass of the first heat exchanger 1 16 may be utilized instead of a larger structural mass that otherwise would have been required for similar results with a typical heat exchanger. The reduced structural mass of the first heat exchanger 116 also provides a considerable reduction in cost over the typically larger heat exchanger.

[0025] The supercritical precooler 126 then discharges the refrigerant component 120 into a second heat exchanger 128, which may be substantially similar to the first heat exchanger 1 16, and therefore will not be described again in detail. The second heat exchanger 128 may be configured to further reduce the temperature of the refrigerant component 120. At this point in the heat pump system 100, the high-pressure, low- temperature refrigerant component 120 may be partially liquefied and directed through conduit 130 to an expansion valve 132 where the pressure and temperature of the refrigerant component 120 is further reduced. In one embodiment, the expansion valve

132 reduces the pressure of the refrigerant component 120 to about 560 psi (about 38.1 atm), while the temperature is reduced still further to about 40°F (about 4.4°C).

[0026] The low-temperature, low-pressure refrigerant component 120 ejected from the expansion valve 132 may then be directed through an evaporator 131 that transfers thermal energy between the refrigerant component 120 and a target fluid 133 originating from an external location 135 such that the target fluid 133 is cooled. The target fluid

133 may be a liquid or a gas, or any other known thermal fluid or heat transfer fluid. In one embodiment, the target fluid 133 is or contains water, or a mixture of glycol and water. Specifically, the evaporator 131 acts as a refrigeration circuit and transfers thermal energy from the target fluid 133 to the refrigerant component 120, thereby reducing the temperature of the target fluid 133 and simultaneously increasing the temperature of the refrigerant component 120 which evaporates the remnant liquid carbon dioxide in the refrigerant component 120 back into a vapor state. The cooled target fluid 133 is discharged from the evaporator 131 and used in a separate downstream system or duty 137 requiring a cooled fluid.

[0027] Upon being discharged from the evaporator 131 , the refrigerant component 120 is returned through the second heat exchanger 128 in order to elevate the temperature to close to the initial temperature of the refrigerant component 120 discharged from the supercritical precooler 126. Although some losses are expected, in at least one embodiment, the refrigerant component 120 may be reheated to about 100°F (about 37.8°C) in the second heat exchanger 128. The refrigerant component 120 is then be directed back to the first reservoir 102 via a conduit 134 to help regenerate the solution to a first state 106 and begin the cycle over again.

[0028] Returning now to the second reservoir 104, the weak solution in the second state 108 that remains after the refrigerant component 120 is bled off into conduit 122 is directed out of the bottom of the second reservoir 104. The weak solution may be directed through a fluid turbine 138 that is in fluid communication with both the second reservoir 104 and the first reservoir 102 through the heat exchanger 1 16. The fluid turbine 136 may be configured to extract at least a portion of remaining energy present in the weak solution. In one embodiment, the fluid turbine 136 may be an impulse turbine, such as a Pelton wheel, configured to extract energy from the impulse (momentum) of the moving weak solution discharged from the second reservoir 104. In other embodiments, the fluid turbine 136 may be a reaction turbine or any other type fluid turbine.

[0029] In at least one embodiment, the fluid turbine 136 may be operativeiy coupled to the pump 112 in order to offset at least a portion of the work consumed by pump 1 12. In other embodiments, however, the fluid turbine 138 may be operativeiy coupled to an external device 138 configured to convert the mechanical energy into useful work or other form of energy. For example, the fluid turbine 136 may be configured to drive the external device 138 (e.g., convert thermal energy into mechanical energy). The external device 138 may be a power generator, alternator, or other electricity generating device capable of transforming the mechanical energy into electrical energy, such as generating electricity with an alternating current or a direct current. In other embodiments, the external device 138 may be a pump (e.g., turbopump), compressor, mill, motor, or other load-receiving device.

[0030] The fluid turbine 136 reduces the pressure of the weak solution to near the pressure of the first reservoir 102 (e.g., about 560 psi; about 38.1 atm) before being directed to the first heat exchanger 1 16. The first heat exchanger 1 16 may be adapted to recoup at least a portion of the heat Qj_n used to heat the solution in the second reservoir 106 and transfer that thermal energy to the solution discharged from the pump 1 12 and subsequently passed through the first heat exchanger 116.

[0031] After leaving the first heat exchanger 1 16, the weak solution may then return to the first reservoir 102 where the weak solution is mixed with the refrigerant component 120 returning from the cycle to regenerate the solution at a first state 108.

[0032] As will be appreciated by those skilled in the art, the disclosure has several practical applications, especially in the automobile air conditioning field. Other applications include industrial heating and air conditioning systems. The embodiments described herein have a number of distinct advantages over existing systems of water/ammonia and lithium bromide (LiBr) in that the refrigerant is high pressure, thus requiring smaller heat exchangers, and utilizes a non-toxic working fluid. Furthermore, there is no potential for crystallization as is the case with LiBr. Also, the application is also well suited for indoor applications because of the absence of toxic working fluids which may leak into human occupied spaces. Further still, the implementation of the fluid turbine 138 takes advantage of residual thermal energy present in the solution, thereby increasing the efficiency of the heat pump system 100.

[0033] Figure 2 depicts a flowchart illustrating a method 200 for delivering thermal energy as heat. The method 200 may include increasing a pressure of a solution with a pump, as at 202. The solution may be drawn from a first reservoir and, as explained above, the solution may include a combination or mixture of carbon dioxide and an absorbent, such as an alcohol. The temperature of the solution may be increased in a first heat exchanger, as at 204. The first heat exchanger may be fluidly coupled to the pump and also a second reservoir, such that the first heat exchanger interposes the two. The method 200 may further include boiling off at least a portion of the carbon dioxide from the solution in the second reservoir, as at 206. The boiled off carbon dioxide may generate a refrigerant component containing carbon dioxide in a gaseous state.

[0034] The refrigerant component may then be cooled to have a supercritical state across a supercritical precooler, as at 208. As the refrigerant component cools, heat is simultaneously extracted therefrom. The supercritical precooler may be in fluid communication with the second reservoir. The refrigerant component may be expanded in an expansion valve, as at 210, thereby resulting in a cooled liquid/vapor carbon dioxide composition. The expansion valve may be fluidly coupled to the supercritical precooler and also fluidly coupled to an evaporator. The evaporator receives the cooled liquid/vapor carbon dioxide composition discharged from the expansion valve and cools a target fluid channeled through the evaporator. The result is a cooled target fluid for use in another application, and a substantially vapor-state refrigerant component discharged from the evaporator. Accordingly, the expansion valve and evaporator form integral parts of a refrigeration circuit. [0035] The method 200 may also include directing the refrigerant component discharged from the expansion valve and evaporator into the first reservoir, as at 212. A portion of the solution from the second reservoir may be received in a fluid turbine, as at 214. The fluid turbine may be fluidly coupled to the second reservoir. The fluid turbine may be configured to extract residual thermal energy from the portion of the solution, as at 218.

[0036] It should be noted that the use of the term carbon dioxide is not intended to be limited to carbon dioxide of any particular type, purity, or grade. For example, industrial grade carbon dioxide may be used without departing from the scope of the disclosure. Carbon dioxide is a neutral working fluid that offers benefits such as non-toxicity, non- f!ammability, high availability, and is generally inexpensive.

[0037] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

Claims:

1 . A heat pump system, comprising:

a first reservoir in fluid communication with a second reservoir;

a pump fluidly coupled to the first and second reservoirs and configured to draw a solution from the first reservoir and to transfer the solution into the second reservoir, the solution comprising a refrigerant and an absorbent, wherein the absorbent at least partially absorbs the refrigerant in the first reservoir and at least partially desorbs the refrigerant in the second reservoir to generate a refrigerant component in a gaseous state;

a supercritical precooler fluidly coupled to the second reservoir and configured to receive and to extract thermal energy from the refrigerant component while the refrigerant component is in a supercritical state;

an expansion valve in fluid communication with the supercritical precooler and configured to reduce a pressure and a temperature of the refrigerant component discharged from the supercritical precooler;

a conduit fluidly coupled to and between the expansion valve and the first reservoir and configured to direct the refrigerant component discharged from the expansion valve into the first reservoir; and

a fluid turbine fluidly coupled to the second reservoir and configured to receive the solution and extract at least a portion of residual thermal energy therefrom.

2. The heat pump system of claim 1 , wherein the refrigerant comprises carbon dioxide.

3. The heat pump system of claim 1 , wherein the fluid turbine is an impulse turbine.

4. The heat pump system of claim 1 , wherein the fluid turbine is operatively coupled to the pump and the residual thermal energy extracted from the solution with the fluid turbine is used to drive the pump.

5. The heat pump system of claim 1 , further comprising an external device operativeiy coupled to the fluid turbine, wherein the fluid turbine is configured to convert thermal energy into mechanical energy and the external device is configured to receive and convert the mechanical energy.

6. The heat pump system of claim 5, wherein the external device is a power generator configured to convert the mechanical energy to electrical energy,

7. The heat pump system of claim 1 , further comprising an evaporator in fluid communication with the expansion valve and having a target fluid circulating therein, the evaporator being configured to transfer thermal energy from the target fluid to the refrigerant component such that the target fluid is cooled.

8. A method for delivering heat, comprising:

increasing a pressure of a solution with a pump, the solution being drawn from a first reservoir and comprising carbon dioxide and an absorbent;

increasing a temperature of the solution in a first heat exchanger fluidly coupled to the pump and a second reservoir;

boiiing off at ieast a portion of the carbon dioxide from the solution in the second reservoir to generate a refrigerant component comprising carbon dioxide in a gaseous state;

cooling the refrigerant component with a supercritical precooler to be in a supercritical state while extracting heat from the refrigerant component, the supercritical precooler being in fluid communication with the second reservoir;

expanding the refrigerant component in an expansion valve fluidly coupled to the supercritical precooler;

directing the refrigerant component discharged from the expansion valve into the first reservoir;

receiving a portion of the solution from the second reservoir in a fluid turbine fluidly coupled to the second reservoir; and

extracting thermal energy from the portion of the solution with the fluid turbine.

9. The method of claim 8, further comprising driving the pump with the thermal energy extracted from the portion of the solution, the pump being operatively coupled to the fluid turbine.

10. The method of claim 8, further comprising driving an external device with the thermal energy extracted from the portion of the solution, the external device being operatively coupled to the fluid turbine.

1 1 . The method of claim 8, further comprising transferring thermal energy in a second heat exchanger from the refngerant component discharged from the supercritical precooler to the refrigerant component discharged from the expansion valve.

12. The method of claim 8, wherein expanding the refrigerant component in an expansion valve results in a cooled refrigerant component, the method further comprising:

directing the cooled refrigerant component into an evaporator fluidly coupled to the expansion valve; and

cooling a target fluid with the cooled refrigerant component in the evaporator.

13. A heat pump system, comprising:

a pump fluidly coupled to a first reservoir and configured to draw a solution from the first reservoir and increase a pressure of the solution, the solution comprising a refrigerant and an absorbent;

a first heat exchanger fluidly coupled to the pump and configured to heat the solution;

a second reservoir fluidly coupled to the first heat exchanger and configured to boil the solution to at least partially desorb the refrigerant from the absorbent, thereby generating a refrigerant component in a gaseous state;

a supercritical precooler fluidly coupled to the second reservoir and configured to receive and to extract thermal energy from the refrigerant component while the refrigerant component is in a supercritical state; a second heat exchanger f!uidly coupled to the supercritical precoo!er and configured to decrease a temperature of the refrigerant component discharged from the supercritical precooler;

an expansion valve fiuidly coupled to the second heat exchanger and configured to reduce the pressure and temperature of the refrigerant component discharged from the second heat exchanger;

one or more conduits fluid!y communicating the expansion valve with the first reservoir to direct the refrigerant component discharged from the expansion valve into the first reservoir; and

a fluid turbine fiuidly coupled to the second reservoir and configured to receive a portion of the solution in the second reservoir and extract thermal energy therefrom.

14. The heat pump system of claim 13, wherein the fluid turbine is operatively coupled to the pump, and the thermal energy derived from the portion of the solution is used to drive the pump.

15. The heat pump system of claim 13, further comprising an external device operatively coupled to the fluid turbine and configured to be driven by the fluid turbine using the thermal energy derived from the portion of the solution.

16. The heat pump system of claim 15, wherein the external device is a generator adapted to generate electrical power.

17. The heat pump system of claim 13, wherein the refrigerant comprises carbon dioxide.

18. The heat pump system of claim 13, wherein the portion of the solution discharged from the fluid turbine passes through the first heat exchanger before being introduced back into the first reservoir.

19. The heat pump system of claim 18, wherein a temperature of the solution in the first heat exchanger is increased by transferring thermal energy from the portion of the solution discharged from the fluid turbine to the solution discharged from the pump.

20. The heat pump system of claim 13, further comprising an evaporator in fluid communication with the expansion valve and having a target fluid circulating therein, the evaporator being configured to transfer thermal energy from the target fluid to the refrigerant component such that the target fluid is cooled.