CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Patent Application No. 62/326,553, filed on April 22, 2016, the entirety of which is incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

[0002] The present invention relates generally to the field of liquid desiccant air conditioning systems, particularly one incorporating a desiccant heating system.

BACKGROUND

[0003] Air conditioning refers to the heating, cooling, cleaning, humidification, and

dehumidification of air. Conventional air conditioning systems utilize an engine that is capable of providing the energy required for the cooling and dehumidification demands of an indoor space, including the energy needed for operation during peak demand. The vast majority of operating conditions, however, demand much less energy than that consumed by conventional air conditioning systems. There remains a need for an air conditioning system that can provide cooling and humidification in an energy-efficient and cost-efficient manner.

SUMMARY

[0004] In some embodiments, an air conditioning system having a desiccant regeneration system is provided. The air conditioning system can include a liquid desiccant loop having a low concentration desiccant portion and a high concentration desiccant portion, a dehumidification unit having a dehumidification unit inlet and a dehumidification unit outlet, a regeneration unit having a regeneration unit inlet and a regeneration unit outlet, and a desiccant heating system adapted to heat low concentration desiccant in a low concentration desiccant section to accelerate regeneration of low concentration desiccant in the regeneration unit. The desiccant heating system can include a burner arranged to heat low concentration desiccant passing through the desiccant heating system. In the regeneration unit, the high concentration desiccant portion can extend from the regeneration unit outlet to the dehumidification unit inlet, and the low concentration desiccant portion can extend from the dehumidification unit outlet to the regeneration unit inlet.

[0005] A method of operating an air conditioning system having a desiccant heating system is also described.

[0006] These and other features, objects and advantages of the present invention will become more apparent to one skilled in the art from the following description and claims when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a diagram of a liquid desiccant regeneration system as described herein.

[0008] Fig. 2 is a diagram of another liquid desiccant regeneration system as described herein.

[0009] Fig. 3 is a diagram showing an alternate embodiment of Fig. 1, in which the engine coolant and the heating stream are the same.

[0010] Fig. 4 is a diagram showing still another liquid desiccant regeneration system as described herein.

[0011] Fig. 5 is a diagram showing yet another liquid desiccant regeneration system as described herein.

[0012] Fig. 6 is a diagram of a liquid desiccant regeneration system as described herein, where the engine and the heater are in series and the regeneration unit is a combined mass and heat exchanger.

[0013] Fig. 7 is a variation of Fig. 6 where the fuel cell and the heater are in parallel.

[0014] Fig. 8 is a generalized schematic of the liquid desiccant regeneration system as described herein.

[0015] Fig. 9 is a diagram showing another liquid desiccant regeneration system as described herein.

[0016] Fig. 1 OA is a diagram showing one arrangement of the heating stream and the stream being heated with respect to the thermally conductive wall; Fig. 10B is a diagram showing one arrangement of the low concentration desiccant and the process air with respect to a water vapor permeable wall; Fig. IOC is a diagram showing one arrangement of the heating stream, the low concentration desiccant, and the process air in a combined mass and heat exchanger as described herein; Fig. 10D is a diagram showing an arrangement of a stream being heated and the burner flames with respect to a burner thermally conductive wall; and Fig. 10E is a diagram showing another arrangement of the heating stream, the low concentration desiccant, and the process air in a combined mass and heat exchanger as described herein.

[0017] Fig. 11 A is a diagram of a low concentration desiccant reservoir; and Fig. 1 IB is a diagram of a high concentration desiccant reservoir.

DETAILED DESCRIPTION

[0018] As shown in Figs. 1-1 IB, a system 100 for maintaining a space 90 being air conditioned within a target range of temperature and humidity during continuous operation is disclosed. In one embodiment, the system 100 comprises a liquid desiccant loop 102, a dehumidification unit 1112, a regeneration unit 1159, and a desiccant heating system 104. The liquid desiccant loop 102 can include a low concentration desiccant portion 124/14 and a high concentration desiccant portion 126/16. The dehumidification unit 1112 can have a

dehumidification unit inlet 1142 and a dehumidification unit outlet 1136, and the regeneration unit 1159 can have a regeneration unit inlet 1138 and a regeneration unit outlet 140. The high concentration desiccant portion 126 can extend from the regeneration unit outlet 140 to the dehumidification unit inlet 1142, and the low concentration desiccant portion 124 can extend from the dehumidification unit outlet 1136 to the regeneration unit inlet 1138. The desiccant heating system 104 is adapted to heat low concentration desiccant in the low concentration desiccant section 124 to accelerate regeneration of low concentration desiccant in the regeneration unit 1159. The heating system 104 includes a burner 110 arranged to heat low concentration desiccant passing through the desiccant heating system 104.

[0019] As used herein, "adapted so that" or "adapted to" can indicate that the system includes a control system or energy management subsystem 70 containing non-transitory instructions to cause the system 100 to operate according to the "adapted so that/adapted to" provision. In addition, "adapted so that" and "adapted to" also indicates a method where the system 100 is operated to produce the desired outcome. Although the control system or energy management subsystem 70 may be shown as a discrete element or connected to specific elements, it will be understood that the control system or energy management subsystem 70 can be connected to any and all motors, control features, and processors that are part of the system 100 either by wired or wireless communication devices.

[0020] The system 100 can also include a plurality of pumps controlled by the control system or energy management subsystem 70. For example, a coolant pump 19 can be used to control the flow of engine coolant 102 through the coolant loop. Similarly, a heating stream pump 111 can be used to control the flow of the heating stream 114 through the burner 110.

[0021] The heating system 104 is designed to provide enhanced regeneration of liquid desiccant in order to provide increased peak cooling levels to an air conditioning system 32 that is part of the liquid desiccant system described herein. The system 100 can be adapted to include a high concentration desiccant reservoir 62, which allows storage of high concentration desiccant when the cooling/dehumidification load is low. However, this only allows for a limited amount of stored cooling capacity and the periods of high demand may not be spaced apart far enough for the regenerator 1159 to replenish the high concentration desiccant reservoir 62. Alternately, the peak cooling demand may require a much larger engine 18 than would otherwise be required for the system 100. It has been discovered that a much smaller engine 18 can be used to provide the necessary cooling when a supplemental heating system 104, including a burner 110, is incorporated into the system 100 in order to facilitate rapid regeneration of the low concentration desiccant.

[0022] In some embodiments, the burner is fed a gas selected from the group consisting of methane, ethane, propane, butane, pentane, natural gas, and combinations thereof. Within the burner 110, the fluid being heated and the burner flames are on opposite sides of at least one burner thermally conductive wall 138. An example of this arrangement is shown in Fig. 10D.

[0023] In some embodiments, the burner 110 is adapted for intermittent operation. This may be helpful when the engine 18 used as a source of heat for desiccant regeneration is smaller than what is typically necessary for yearly peak demand. Examples of such engines include, but are not limited to, electrical or internal combustion engines, a fuel cell or another type of engine that generates energy through electrochemical oxidation of a fuel, or any other engine that can operate continuously (except for maintenance, planned stoppages, etc.). In such instances, an engine 18 of a particular output that can provide adequate desiccant regeneration to meet the cooling/dehumidification demands for the vast majority (>90% or >95%) of the operating conditions may not be useful in a liquid desiccant system 100 unless it includes a supplemental heating system 104 as described herein. Thus, as an example, while a 10 kW engine would generally be required to provide 10 tons of cooling, a 5 kW engine with a supplemental heating system 104, as described herein, can provide the same cooling capacity.

[0024] In some embodiments, the system 100 includes an engine 18 that generates energy. In some embodiments, the engine 18 is an internal combustion engine and energy is generated through combustion of a fuel (e.g., gasoline, natural gas, etc.) prior to producing a heated exit stream. In some embodiments, energy is generated through electrochemical oxidation of a fuel, and produces a heated exit stream. In some such embodiments, the desiccant heating system 104 includes a primary regeneration heat exchanger 106, comprising at least one primary thermally conductive wall 130. In some embodiments, as shown in Fig. 10A, the low concentration desiccant portion 124 and the heated exit stream 102/20 are in contact with opposite sides of the at least one primary thermally conductive wall 130. In some embodiments, the heated exit stream is a heated heat exchange fluid, an exhaust stream, or both. Various configurations for the heat exchangers 106, 108, mass exchangers 1159, and heat and mass exchangers 1159 described herein are illustrated in Figs. 10A-10E. As will be understood, these arrangements can be carried out using a variety of exchange techniques known to those of skill in the art, including plate technology, tubular technology, ducts of any cross-sectional shape, and others.

[0025] In some embodiments, as shown in Fig. 4, the dehumidification unit 1112 further comprises a process air stream 38, a dehumidification unit desiccant stream 17, and at least one dehumidifier vapor permeable wall 36, wherein portions of the process air stream 38 and the dehumidification liquid desiccant stream 17 are in contact with opposite sides of each of the at least one dehumidifier vapor permeable walls 36.

[0026] As shown in Figs. 1-4 and 8, in some embodiments, the burner 110 can be used to warm a heating stream that heats the low concentration liquid desiccant via a regeneration heat exchanger. In some embodiments, the desiccant heating system 104 further comprises a regeneration heat exchanger 106/108, comprising at least one thermally conductive

wall 130/132, wherein the low concentration desiccant portion 124 and a heating stream 114 are in contact with opposite sides of at least one thermally conductive wall 130/132, and the burner 110 heats the heating stream 114 prior to the at least one thermally conductive wall 130/132, e.g., before the heating stream 114 is fed to the regeneration heat

exchanger 106/108. [0027] In some embodiments, such as those shown in Figs. 1, 3, and 4, the desiccant heating system 104 comprises a primary regeneration heat exchanger 106, comprising at least one primary thermally conductive wall 130, and the regeneration heat exchanger is a supplemental regeneration heat exchanger 108. In some such embodiments, the at least one thermally conductive wall is at least one supplemental thermally conductive wall 132. In some such embodiments, the system 100 further comprises an engine 18 that generates energy through electrochemical oxidation of a fuel, and the engine 18 produces a heated exit stream 102, where the low concentration desiccant portion 124 and the heated exit stream are in contact with opposite sides of the at least one primary thermally conductive wall 130. In some such embodiments, the system 100 further comprises an engine 18 that generates energy through combustion of a fuel (e.g., gasoline, natural gas, etc.) and the engine 18 produces a heated exit stream 102, where the low concentration desiccant portion 124 and the heated exit stream are in contact with opposite sides of the at least one primary thermally conductive wall 130. In some embodiments, the heated exit stream is selected from a heated exhaust stream (e.g., cathode exhaust, gaseous exhaust) and heated heat exchange fluid.

[0028] In some embodiments, as shown in Figs. 1, 3, and 4, the low concentration

desiccant 124 flows through the primary regeneration heat exchanger 106 before passing through the supplemental regeneration heat exchanger 108. In some embodiments, the heated exit stream 102 comprises an engine coolant and the heating stream 114 comprises a thermal transfer fluid. In such embodiments, the heating stream 114 and the low concentration desiccant 124 are on opposite sides of each supplemental thermally conductive wall 132.

[0029] In some embodiments, the system 100 comprises an engine coolant reservoir 112/215, a thermal transfer fluid reservoir 55, or both. In some embodiments, the engine coolant and the thermal transfer fluid are the same. In some such embodiments, the engine coolant

reservoir 112/215 and the thermal transfer fluid reservoir 55 are the same. In Figs. 1, 3, 4, and 5, the engine coolant reservoir 112/215 and the thermal transfer fluid reservoir 55 are separated by a dotted line to indicate that the reservoirs 112/55 may be separated or may be combined. In some embodiments, the engine coolant and thermal transfer fluid can be independently selected from the group consisting of ethylene glycol, propylene glycol, water, and combinations thereof.

[0030] In some embodiments, as shown in Fig. 2, the heated exit stream 102 comprises engine coolant, which is fed into the burner 110, to further heat the engine coolant and produce the heating stream 114. In some such embodiments, the heating stream 114 is fed into the primary regeneration heat exchanger 106 and the recirculates into the engine 18. In some embodiments, an engine coolant reservoir 112/215 is located in the engine coolant loop between the primary regeneration heat exchanger 106 and the engine 18.

[0031] In some embodiments, as shown in Figs. 1-4, the regeneration unit 1159 is a mass exchange unit comprising at least one water vapor permeable regenerator wall 134. As show in Fig. 10B, in such embodiments, the low concentration desiccant stream 124 and a process air stream 26 are in contact with opposite sides of each water vapor permeable regenerator wall 134.

[0032] In some embodiments, such as those shown in Figs. 5-8, the burner is adapted to heat a heating stream, and the burner outlet 116 is operatively connected to a heating stream inlet 118 of the regeneration unit 1159 so that the heating stream 114 is fed to the regeneration unit 1159.

[0033] In some embodiments, as shown in Figs. 6 and 8, the system 100 includes an engine 18 that generates energy through electrochemical oxidation of a fuel, where the engine 18 produces a heated exit stream. In some such embodiments, the system 100 further comprises an engine 18 that generates energy through combustion of a fuel (e.g., gasoline, natural gas, etc.) and the engine 18 produces a heated exit stream 102. In some such embodiments, the engine exit stream outlet 120 is operatively connected to a burner inlet 121, so that the heated exit stream is fed to the burner 110. In such embodiments, the heated exit 102 stream can be engine coolant.

[0034] In the embodiments of Figs. 6 and 8, the regeneration unit 1159 can be a combined mass and heat exchanger that includes at least one thermally conductive regenerator wall 136, and is designed so that the low concentration desiccant stream 124 and the process air stream contact one another. In such embodiments, the low concentration desiccant stream 124 and the heating stream 114 are in contact with opposite sides of each thermally conductive regenerator wall 136. In some embodiments, as shown in Fig. IOC, the regeneration unit 1159 also includes at least one water vapor permeable regenerator wall 134, and the low concentration desiccant stream 124 and a process air stream 26 are in contact with opposite sides of each water vapor permeable regenerator wall 134 within the regeneration unit 1159. In some embodiments, as shown in Fig. 10E, the regeneration unit 1159 includes at least one regeneration wi eking material 142 and the low concentration desiccant stream 124 wicks through the wi eking material 142 while contacting the process air stream 26. In some embodiments, each strip of regeneration wi eking material 142 can be in contact with a thermally conductive generator wall 136 on a side of the thermally conductive generator wall 136 opposite the heating stream 114.

[0035] In these combined mass and heat exchange arrangements, the low concentration desiccant stream 124 is heated by the heating stream 114, which facilitates transfer of water vapor from the low concentration desiccant stream 124 to the process air stream 26. In some embodiments, the process air stream can be outside air and the process exhaust stream 28 can be vented to the atmosphere.

[0036] In some embodiments, the thermally conductive walls 130, 132, 136, 138 described herein can be independently selected from the group consisting of aluminum, brass, carbon steel, chrome-moly steel (1-12 Cr, 0.5-1 Mo), titanium, copper, cupro-nickel (70-90 Cu, 10-30 Ni), inconel, monel (67 Ni, 30 Cu, 1.4 Fe), nickel, stainless steel, and combinations thereof.

[0037] In some embodiments, the wicking material 142 described herein can be a porous material adapted for wicking the liquid desiccant and providing large amounts of surface area to facilitate mass transfer of water vapor to the process air stream 26. For example, the wicking material can be designed to allow liquid desiccant to wick downward in a controlled manner. Wicking materials that are useful in designs set forth herein include foams, spunbond, meltblown, textiles, and other materials. In some embodiments, the wicking material can be formed from a material selected from the group consisting of cotton, rayon, nylon,

polypropylene, polyethylene, polyester, combinations thereof, and other materials.

[0038] As shown in Fig. 5, in some embodiments employing a combined mass and heat exchanger, the system 100 includes a primary regeneration heat exchanger 106, comprising at least one primary thermally conductive wall 130. In such embodiments, as illustrated in

Fig. 10A, the low concentration desiccant portion 124 and the heated exit stream 102 are in contact with opposite sides of the at least one primary thermally conductive wall 130. The low concentration desiccant passes through the primary regeneration heat exchanger 106 before being fed to the regeneration unit 1159.

[0039] As shown in Fig. 7, in some embodiments, the heating stream 114 and the heated exit stream 102 are mixed to form a combined heating stream 103 prior to being fed into the heating stream inlet 118 of the regeneration unit 1159. In such an embodiment, as shown in Fig. 7, the regeneration unit 1159 can be a combined mass and heat exchanger, having at least one thermally conductive regenerator wall 136. In some embodiments, the regeneration unit 1159 also includes at least one water vapor permeable regenerator wall 134 or at least one wicking material 142. In some embodiments, as illustrated in Fig. IOC, the low concentration desiccant stream 124 and a process air stream 26 are in contact with opposite sides of each water vapor permeable regenerator wall 134, and the low concentration desiccant stream 124 and the combined heating stream 103 are in contact with opposite sides of each thermally conductive regenerator wall 136. In some embodiments, as illustrated in Fig. 10E, the low concentration desiccant stream 124 wicks through a wicking material 142 and a process air stream 26 contacts the low concentration desiccant stream 124, while the low concentration desiccant stream 124 and the combined heating stream 103 are in contact with opposite sides of each thermally conductive regenerator wall 136.

[0040] As shown in Fig. 9, in some embodiments, the burner 110 is adapted to directly heat low concentration desiccant in the low concentration desiccant portion 124, wherein the heated low concentration desiccant is the fed into the regeneration unit 1159. In some such

embodiments, the system 100 can include a primary regeneration heat exchanger 106, having at least one primary thermally conductive wall 130, where the low concentration desiccant portion 124 and the heated exit stream 102 of the engine 18 are in contact with opposite sides of at least one thermally conductive wall.

[0041] In some such embodiments, such as the one shown in Fig. 9, the regeneration unit 1159 is a mass exchange unit comprising at least one water vapor permeable regenerator wall 134, where the low concentration desiccant stream 124 and a process air stream 26 are in contact with opposite sides of each water vapor permeable regenerator wall 134. As shown in Fig. 9, in some embodiments, the process air stream 26 can be heated in a heat exchanger 30, where the heated exit stream 20 contacts and heats the carrier stream 26 in the heat exchanger 30. As described herein, liquid desiccants tend to be corrosive, so the materials that come into contact with them must be resistant to the corrosive agents (e.g., salt ions) in the liquid desiccant. In addition, materials used to facilitate heat transfer (e.g., metals) are generally susceptible to corrosion by liquid desiccants. Thus, where the burner 110 is used to heat the low concentration desiccant, the ducts carrying the low concentration desiccant can be formed of titanium or other corrosion resistant metals.

[0042] As shown in Figs 1-10E, a liquid desiccant regeneration system is disclosed. The system utilizes a heated exit stream (e.g., exhaust, heated heat exchange fluid, etc.) from an engine to regenerate low concentration liquid desiccant. In one example, the low concentration liquid desiccant can be the exit stream of a liquid desiccant air conditioning system that uses high concentration liquid desiccant to dehumidify air. Water from the liquid desiccant regeneration system can also be recovered and used, for example, to provide evaporative cooling to the air conditioning system. Power generated by the engine is used to power the air conditioner, the building being cooled and, where excess power is produced, the power can be sold back to the power grid or stored for future use (e.g., in batteries, capacitors, etc.).

[0043] As shown in Fig. 4, a liquid desiccant regeneration system 100 is described. The desiccant regeneration system 100 can include a liquid desiccant regenerator 12, a low concentration liquid desiccant stream 14 feeding into the liquid desiccant regenerator 12, and a high concentration liquid desiccant stream 16 exiting the liquid desiccant regenerator 12. The liquid desiccant regenerator 12 can include an engine 18 producing a heated exit stream 20, and at least one dehydrating conduit 22 comprising a regenerator water vapor permeable wall 24. As shown in Fig. 6, a carrier stream 26 and the low concentration liquid desiccant 14 are in contact with opposite sides of the regenerator water vapor permeable wall 24 and the low concentration liquid desiccant stream 14 is heated by heat from the heated exit stream 20 to drive water from the low concentration liquid desiccant stream 14 through the regenerator water vapor permeable wall 24 to the carrier stream 26 to form a humidified carrier stream 28. The desiccant concentration in the high concentration liquid desiccant stream 16 is higher than a desiccant concentration in the low concentration liquid desiccant stream 14.

[0044] Fig. 4 shows a generalized embodiment of the liquid desiccant regeneration

system 100, while Fig. 9 shows another embodiment having the same or similar features. For example, Fig. 9 schematically shows liquid desiccant regeneration systems 100 that use separate heat exchangers and mass exchangers. Of course, in other embodiments, similar systems 100 employing combined heat and mass exchangers are also envisioned. As will be understood, depending of the application and objectives, a desiccant regeneration system 100 can employ individual heat exchangers and mass exchangers, combined heat and mass exchangers, or a combination of both. Additional details on liquid desiccant air conditioning and regeneration systems useful in the systems described herein, can be found in U.S. Patent No. 9,423, 140, entitled "Liquid Desiccant Regeneration System, Systems Including the Same, and Methods of Operating the Same," by Daniel A. Betts, et al., filed February 17, 2015 ("the Ί40 Patent"), the entirety of which is incorporated herein by reference. Additional details on heat and mass exchangers useful in the desiccant regeneration systems 100 described herein can be found in U.S. Patent Application Publication No. 2015/0233588, entitled "Heat and Mass Transfer Device and Systems Including the Same," by Daniel A. Betts and Matthew Daniel Graham, filed February 17, 2015 ("the '588 Publication"), the entirety of which is incorporated herein by reference.

[0045] In some embodiments, the heated exit stream 20 is selected from the group consisting of heated heat exchange fluid, an exhaust stream, or both. For example, the heated heat exchange fluid can be coolant used to keep the engine 18 from overheating. In some such embodiments, the heated heat exchange fluid 21a can pass through the liquid desiccant regenerator 12 as part of a closed loop circuit with the engine 18.

[0046] In some embodiments, the heated exit stream 20 can be an exhaust stream, such as the gaseous exhaust stream 21b from an internal combustion engine or the gaseous exhaust stream 21b from the anode or cathode chamber of a fuel cell.

[0047] In some embodiments, the heated exit stream 20 is an exhaust stream 21b and the carrier stream 26 comprises the exhaust stream 21b. In some embodiments, such as the one shown in Fig. 4, the liquid desiccant regenerator 12 further comprises a heat exchanger 30, wherein the heated exit stream 20 contacts and heats the carrier stream 26 in the heat

exchanger 30. In some such embodiments, the carrier stream 26 includes ambient air, recirculated air from a space being air conditioned, or a combination of both. Such a

configuration can be beneficial in that these sources of the carrier stream 26 generally have a lower humidity than the heated exhaust stream 20, 21b, so that the driving force to regenerate the low concentration liquid desiccant 14 is increased.

[0048] In some embodiments, the heated exit stream 20 is heated heat exchange liquid 21a exiting the engine 18, and the heated heat exchange liquid 21a contacts and heats the low concentration liquid desiccant stream 14, the carrier stream 26, or both.

[0049] In some embodiments, such as Fig. 4, the heated exit stream 20 includes both a heated heat exchange liquid 21a exiting the engine and a heated exhaust stream 21b. In such embodiments, the heated heat exchange liquid 21a contacts and heats the low concentration liquid desiccant 14, and (a) the heated exhaust stream 21b contacts and heats the carrier stream 26, or (b) the carrier stream 26 comprises the heated exhaust stream 21b. [0050] In some embodiments, the high concentration liquid desiccant stream 16 is directed through an air conditioning system 32. In some embodiments, the air conditioning system 32 includes at least one dehumidification conduit 34 that has a dehumidifier water vapor permeable wall 36. In some embodiments, a process air stream 38 and the high concentration liquid desiccant stream 16 are in contact with opposite sides of the dehumidifier water vapor permeable wall 36, and moisture from the process air stream 38 passes through the dehumidifier water vapor permeable wall 36 to the high concentration liquid desiccant stream 16, thereby dehumidifying the process air stream 38 and diluting the high concentration liquid desiccant stream 16.

[0051] In some embodiments, the air conditioning system 32 also includes at least one air conditioning heat exchange conduit 40, where (a) the high concentration liquid desiccant stream 16 and a heat exchange fluid 42 are in contact with opposite sides of the air conditioning heat exchange conduits 40, for cooling the high concentration liquid desiccant stream 16, as shown in Figs. 4 and 9; (b) the process air stream 38 and a heat exchange fluid 42 are in contact with opposite sides of the air conditioning heat exchange conduits 40, for cooling the process air stream 38 (not shown); or (c) the high concentration liquid desiccant stream 16 and a first heat exchange fluid 42a are in contact with opposite sides of a first group of the air conditioning heat exchange conduits 40a, for cooling the high concentration liquid desiccant stream 16, and the process air stream 38 and a second heat exchange fluid 42b are in contact with opposite sides of a second group of the air conditioning heat exchange conduits 40b, for cooling said process air (not shown).

[0052] The heat exchange fluids 42a, 42b used herein include, but are not limited to, chilled water or other coolants, including a combination of air and water, which may be used in a heat exchanger or which may be sprayed in a space or coated on a surface to provide psychrometric cooling. For example, Fig. 4 shows an embodiment where a water recovery system 44 supplies a water stream 46 that is sprayed in order to cool the high concentration liquid desiccant stream 16 before it flows into dehumidification conduit(s) 34.

[0053] In some embodiments, the liquid desiccant regeneration system 100 also includes a water recovery system 44. The water recovery system 44 can include a water recovery heat exchange conduit 48, where the humidified carrier air 28 and a water recovery heat transfer fluid 50 are in contact with opposite sides of the water recovery heat exchange conduits 48. An outlet of the water recovery heat exchanger 52 can be in fluid communication with a water reservoir 54/1256 for storing water precipitating from the humidified carrier air 28. In some embodiments, the water recovery system 44 includes a flow control system 56 for controlling transport of water from the water reservoir 54/1256 to one side of the air conditioning heat exchange conduits 40. The flow control system 56 can include a controller 58 and a flow control device 60. Examples of flow control devices 60 include, but are not limited to, pumps and valves.

[0054] In some embodiments, the desiccant regeneration system 100 includes a high concentration liquid desiccant reservoir 62, having an inlet in fluid communication with an outlet of the liquid desiccant regenerator 12 and an outlet in fluid communication with an inlet of the air conditioning system 32. In some embodiments, the desiccant regeneration system 100 includes a low concentration liquid desiccant reservoir 64, having an inlet in fluid

communication with an outlet of the air conditioning system 32 and an outlet in fluid

communication with an inlet of the liquid desiccant regenerator 12.

[0055] In some embodiments, as shown in Fig. 11 A, the low concentration desiccant reservoir 64 is configured with a low concentration desiccant inlet 65 and a low concentration desiccant outlet 67. In some embodiments, there is a difference in concentration between the desiccant entering through inlet 65 and in proximity thereto and the desiccant exiting through outlet 67 and in proximity thereto. In particular, the low concentration inlet is below the low concentration outlet. Without adopting or being limited to any particular scientific theory, the difference in concentration may result from, for example, settling of desiccant salts on or near the bottom of the reservoir, a concentration gradient, a change in pressure, a change in temperature, and/or due to the flow rate of desiccant through the reservoir, which is relatively slow compared to the volume of the tank, which limits mixing.

[0056] In some embodiments, as shown in Fig. 1 IB, the high concentration desiccant reservoir 62 is configured with a high concentration desiccant inlet 61 and a high concentration desiccant outlet 63. In some embodiments, there is a difference in concentration between the desiccant entering through inlet 61 and in proximity thereto and the desiccant exiting through outlet 63 and in proximity thereto. In particular, the high concentration inlet is above the high concentration outlet. Without adopting or being limited to any particular scientific theory, the difference in concentration may result from, for example, settling of desiccant salts on or near the bottom of the reservoir, a concentration gradient, a change in pressure, a change in temperature, and/or due to the flow rate of desiccant through the reservoir, which is relatively slow compared to the volume of the tank, which limits mixing.

[0057] In some embodiments, the capacity of the high concentration liquid desiccant reservoir 62 is sufficient to operate the air conditioning system 32 solely from the high concentration liquid desiccant reservoir 62 continuously for at least one hour, or at least two hours, or at least four hours, or at least eight hours. In some embodiments, the capacity of the low concentration liquid desiccant reservoir 64 is sufficient to operate the liquid desiccant regenerator continuously from the low concentration liquid desiccant reservoir 64 for at least one hour, or at least two hours, or at least four hours, or at least eight hours.

[0058] The liquid desiccant regeneration systems 100 described herein include engines 18 that are adapted for generating energy from a fuel source 66. Thus, in some embodiments, it will be desirable to operate the liquid desiccant regenerator 12, which also produces an electricity stream 68, even when the air conditioning system 32 is not operating.

[0059] In some embodiments, the fuel source 66 is a fuel tank or a fuel line providing fuel from a municipal source or other source. Examples of fuel sources 66 include, but are not limited to, natural gas, propane, butane, liquefied petroleum gas (LPG), hydrogen, city gas (i.e., gas piped to the building from a municipality or other source), and combinations thereof. In some embodiments, the fuel source 66 will be pre-processed before being introduced into the engine 18. For example, a fuel processor can convert natural gas into a hydrogen rich gas before it is fed into an engine 18.

[0060] In some embodiments, the air conditioning system 32 consumes high concentration liquid desiccant at the same rate that the liquid desiccant regenerator 12 regenerates the low concentration liquid desiccant 14 into a high concentration liquid desiccant 16. Because of the desire to operate these two systems 12, 32 independently from one another, in some

embodiments, the air conditioning system 32 can consume high concentration liquid desiccant 16 at a faster or slower rate than the liquid desiccant regenerator 12 regenerates the low

concentration liquid desiccant 14 into high concentration liquid desiccant 16. In some embodiments, the consumption of high concentration liquid desiccant 16 by the air conditioning system 32 is at least 10% faster or at least 10% slower than regeneration of the low

concentration liquid desiccant 14 by the liquid desiccant regenerator 12. In some embodiments, the consumption of high concentration liquid desiccant 16 by the air conditioning system 32 is at least 20% faster or at least 20% slower than regeneration of the low concentration liquid desiccant 14 into high concentration liquid desiccant 16 by the liquid desiccant regenerator 12. In some embodiments, the consumption of high concentration liquid desiccant 16 by the air conditioning system 32 is variable. In some embodiments, the regeneration of the low

concentration liquid desiccant 14 into high concentration liquid desiccant 16 by the liquid desiccant regenerator 12 is variable.

[0061] In some embodiments, the engine 18 generates electricity 68 through electrochemical oxidation of a fuel 66. Examples of engines 18 capable of generating electricity 68 through electrochemical oxidation of a fuel include, but are not limited to, low and high temperature proton exchange membrane fuel cells, solid oxide fuel cells, and flow batteries. In some embodiments, the engine 18 generates electricity 68 through combustion of a fuel (e.g., gasoline, natural gas, etc.) and the engine 18 produces a heated exit stream 102. Examples of engines 18 capable of generating electricity 68 through combustion of a fuel include an internal combustion engine.

[0062] The electricity 68 produced by the engine 18 can be provided to an external power grid, such as the building being air conditioned, the local power grid (e.g., municipal power grid), or both. In some embodiments, electricity 68 produced by the engine 18 is supplied to the air conditioning system 32 or any other electrical components (e.g., pumps, processors, valves, etc.) of the desiccant regeneration system 100.

[0063] In some embodiments, the liquid desiccant concentration in the high concentration liquid desiccant stream 16 can be at least 0.5 wt-% higher than the liquid desiccant concentration in the low concentration liquid desiccant stream 14. In some embodiments, the difference in concentration can be at least at least 1 wt-% higher, at least 1.5 wt-% higher, at least 2 wt-% higher, at least 2.5 wt-% higher, at least 3 wt-% higher, at least 3.5 wt-% higher, or at least 4 wt-%) higher in the high concentration liquid desiccant stream 16 than in the low concentration liquid desiccant stream 14.

[0064] The liquid desiccant can be composed of any hygroscopic liquid such as aqueous salt solutions (e.g., LiCl, NaCl, CaCh), alcohol solutions (e.g. glycerol, methanol, ethanol), or aqueous chemical agents (e.g. CaS0 ₄ ). All materials wetted with the liquid desiccant are constructed of materials that are chemically compatible with the liquid desiccant. [0065] In some embodiments, the liquid desiccant concentration in the low concentration liquid desiccant stream (14) is at least 10 wt-%, at least 20 wt-%>, at least 25 wt-%>, at least 30 wt-%), at least 33 wt-%>, at least 34 wt-%>, at least 35 wt-%>, at least 36 wt-%>, at least 37 wt-%>, at least 38 wt-%>, or at least 39 wt-%>. In some embodiments, the liquid desiccant concentration in the low concentration liquid desiccant stream (14) is 50 wt-%> or less, 45 wt-%> or less, 40 wt-%> or less, 39 wt-%> or less, 38 wt-%> or less, 37 wt-%> or less, 36 wt-%> or less, or 37 wt-%> or less.

[0066] In some embodiments, the liquid desiccant concentration in the high concentration liquid desiccant stream (16) is at least 20 wt-%>, at least 25 wt-%>, at least 30 wt-%>, at least 34 wt-%), at least 35 wt-%>, at least 36 wt-%>, at least 37 wt-%>, at least 38 wt-%>, at least 39 wt-%>, or at least 40 wt-%>. In some embodiments, the liquid desiccant concentration in the high concentration liquid desiccant stream (16) is 50 wt-%> or less, 45 wt-%> or less, 44 wt-%> or less, 43 wt-% or less, 42 wt-% or less, 41 wt-% or less, 40 wt-% or less, 39 wt-% or less, 38 wt-% or less, or 37 wt-%> or less.

[0067] Because liquid desiccants can be corrosive, the duct-work or piping coming into contact with the liquid desiccant streams 14, 16 can be corrosion resistant. For example, the duct-work or piping can be formed from corrosion resistant materials or the inside or outside of the ductwork or piping can be coated with corrosion resistant materials. Examples of materials that are corrosion resistant to liquid desiccants include, but are not limited to titanium, ethylene propylene diene rubber (EPDM), fluorine rubber (FKM), nitrile rubber ( BR), perfluorinated elastomers (FFKM), polytetrafluoroethylene (PTFE), rigid polyvinyl chloride (PVC), polyolefin materials, such as polypropylene (PP), polyethylene (PE), high density polyethelene (HDPE), and others, polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and chloroprene rubber (CR), sulfonated ietrafluoroethylene based fluoropolynier- copolymer (such as Nafion, which is sold by DuPont), water conducting fluoropolymers, and non-fluorinated proton conducting polymers.

[0068] As used herein, the phrases water vapor permeable and micro-porous are used interchangeably. Where a conduit wall, membrane, or material is water vapor permeable or micro-porous, the structure can be made of a material that is hydrophobic, and impermeable to liquids but permeable to water vapor. Such water vapor permeable materials are also referred to as mass transfer conduits, tubes or materials. Examples of solid or monolithic, water vapor permeable materials include sulfonated tetrafluoroethylene based fluoropolymer-copolymer (e.g., Nafion™, sold by DuPont), water conducting fluoropolymers, and non-fluorinated proton conducting polymers (e.g., NanoClear™, sold by Dais Analytic), and high density polyethelene (HDPE).

[0069] In some embodiments, the water vapor permeable materials are formed from fibers of hydrophobic materials. Examples include spunbond or meltblown polymer materials. Such water vapor permeable materials are generally formed from hydrophobic materials. As used herein "hydrophobic" refers to materials with a contact angle of greater than 90° (e.g., at least 100°, at least 115°, at least 120°, or at least 135°).

[0070] A method of operating liquid desiccant regenerating systems 100 such as those described herein is also provided. In some embodiments, the method can include providing a low concentration liquid desiccant stream 14; providing a liquid desiccant regenerator 12, and operating the liquid desiccant regenerating system 100 to produce the high concentration liquid desiccant stream 16, which has a higher desiccant concentration than the low concentration liquid desiccant stream 14. The liquid desiccant regenerator 12 can include an engine 18, wherein heat from the engine 18 is used to convert the low concentration liquid desiccant stream 14 to the high concentration liquid desiccant stream 16.

[0071] In some embodiments, the liquid desiccant regeneration system 100 also includes an air conditioning system 32 that converts the high concentration liquid desiccant stream 16 to a low concentration liquid desiccant stream 14 while dehumidifying process air 38 supplied to an air conditioned space. In some embodiments, the operating step includes transporting the high concentration liquid desiccant stream 16 to the air conditioning system 32, then transporting the low concentration liquid desiccant stream 14 from the air conditioning system 32 to the liquid desiccant regenerating system 12. In some embodiments, the liquid desiccant flows in a closed loop.

[0072] In some embodiments, the operating step comprises operating the liquid desiccant regenerator 12 continuously, and operating the air conditioning system 32 intermittently. In some embodiments, the air conditioning system 32 operates when a temperature, a humidity, or both of the space being air conditioned passes a target temperature or humidity, and the air conditioning system 32 does not operate when a temperature, a humidity, or both of the space being air conditioned are on the other side of the target temperature or humidity. [0073] In some embodiments, the operating step includes operating the liquid desiccant regenerator 12 when the air conditioning system 32 is not operating. For example, the liquid desiccant regenerator 12 can operate during particular times of the day, such as when there is a peak demand for electricity, regardless of whether the air conditioning system 32 is operating.

[0074] The system 100 can also include a control system or energy management subsystem 70 composed of an engine (e.g., fuel cell, internal combustion engine) load controller, a DC to DC converter, and a DC to AC converter. The engine load controller is able to determine the electrical power generated by the engine (e.g., fuel cell stack). This can be done by controlling current draw from the engine and supplied to the DC to DC converter and to the DC to AC converter. For most applications, the energy management subsystem will be connected to the electrical grid and will be able to manage and adjust the ratio of grid power and engine 18 (e.g., fuel cell, internal combustion engine) power used to cover the electrical load of the air conditioning system, the building, and/or external source.

[0075] The energy management subsystem 70 has a role to play in taking advantage of the mismatch between air conditioning load and electricity load throughout the day. As current draw from the engine 18 (e.g., fuel cell, internal combustion engine) is decreased, the efficiency of the engine increases, resulting in decrease in fuel consumed. However, as efficiency increases, heat and water production also decreases. Decreased heat results in decreased rate of liquid desiccant regeneration by the liquid desiccant regenerator 12. The opposite is also true, as current increases the engine 18 (e.g., fuel cell, internal combustion engine) heat production and water production increases. Because the energy management subsystem 70 controls the current from the engine 18 (e.g., fuel cell, internal combustion engine) it also regulates the rate of desiccant regeneration, the concentration of the regenerated desiccant (i.e., high concentration liquid desiccant), and the capacity to take advantage of evaporative cooling in the air conditioning system 32 using water from the water recovery system 44. Therefore, the energy management subsystem 70 controls the operations of the system through its control software.

[0076] In some embodiments, electricity 68 produced by the engine 18 is supplied to the air conditioning system 32.

[0077] While the following discussion is equally applicable to all of the embodiments described herein, the system of Fig. 5 is discussed as an example. As shown in Fig. 8, high concentration liquid desiccant accumulation occurs when electrochemical oxidation occurs between the anode (212) and cathode (213) of the fuel cell, thus generating heat. In the embodiment of Fig. 5, the heat produced by the fuel cell (18) is captured by coolant passing through the fuel cell cooling plate (214). Low concentration liquid desiccant (227) is introduced in the desiccant regenerator (216) by operating the liquid desiccant pump (224). The rate of liquid desiccant regeneration can be varied by varying the flow of coolant into the desiccant regenerator (216) and the flow of low concentration liquid desiccant. Water produced in the fuel cell cathode (213) and the water removed by the liquid desiccant is recovered in the water recovery system (217). Water is accumulated in the water container (218) and high concentration liquid desiccant is accumulated in the high concentration liquid desiccant container (221). When accumulating high concentration liquid desiccant, the high concentration liquid desiccant pump (223) does not operate or operates at a rate that it conveys high concentration liquid desiccant at a rate lower than the rate at which it flows into the high concentration liquid desiccant container (221). In this way, the thermal energy produced by the fuel cell (18) is stored, enabling a decoupling of the fuel cell electrical power output from the cooling capacity of the air conditioning subsystem (32).

[0078] Alternatively, the air conditioner (32) can operate at a higher cooling capacity than normal when the heat of the fuel cell (18) is dissipated. This is done by using the high concentration liquid desiccant pump (223) to feed the liquid desiccant in the high concentration liquid desiccant container (221) to the air conditioning dehumidifier (220) at a higher flow rate than the flow rate of high concentration liquid desiccant (226) leaving the water recovery system (217). In this case, low concentration liquid desiccant is accumulated in the low concentration liquid desiccant container (219).

[0079] The stored water and high concentration liquid desiccant can be used to drive desiccant enhanced evaporative cooling air conditioning system (32). The energy management system can therefore optimize engine electricity production, concentration of high concentration liquid desiccant, rate of high concentration liquid desiccant storage, and rate of water recovery, based on optimization of the economic benefit of the system to the user on a daily or hourly basis. Thus, an energy management subsystem (70) can be present in any or all of the systems described herein.

[0080] The decoupling of the desiccant regenerator 12 and the air conditioning system 32 can be particularly beneficial because air humidity generally rises at night as temperature drops. This makes the conditions ideal for recovery of water while using the high concentration liquid desiccant principally to dehumidify air. During the middle of the day, temperature tends to rise but humidity drops. This means that the system could be optimized to provide greater cooling during the day using water stored during the evening when higher relative humidity conditions exist. The optimization by the energy management system (3070/70) can be based on actual or anticipated sensible and latent head load in the building combined with actual and anticipated outside air humidity and temperature.

[0081] The following provides a variety of embodiments of a liquid desiccant regeneration system as described herein. Although discussed in different groups, it should be understood that each is consistent with the spirit of the disclosure and various unit operations from one embodiment can be exchanged with, added to, or taken from another embodiment.

[0082] As used herein, "conduit" and "duct" each have their standard meanings and include hollow solids, including pipes, tubes, conduits, rectangular solids, and other structures that a fluid can flow through, including the space between plates (e.g., plate heat exchanger or a plate mass transfer device, such as those used for dehumidification or liquid desiccant regeneration).

[0083] As used herein, "contact" has its standard meaning and includes where materials within different ducts are in thermal or fluid communication through a common wall or membrane. For example, two ducts would be in contact where they contain fluids on opposite sides of a micro- porous membrane or where they contain fluids on opposite sides of a thermally-conductive, impermeable wall (e.g., a metal wall).

[0084] As used herein, "fluid communication" includes connected as part of the fluid flow of the system. When used generally, fluid communication relates to either a direct fluid connection where two points are directly connected by ducts, pipes, conduits, or tubes, and indirect fluid communication where two points are separated by one or more unit operation, including, but not limited to, a heat exchanger, a fuel cell, a dehumidifier, a radiator, a holding tank, etc. As used herein, "in fluid communication" refers to in fluid communication in the direction of flow of fluid through the system. Thus, unless there is a loop the outlet of a tube cannot be in fluid communication with the inlet of the same tube.

[0085] As shown in Fig. 8, in some embodiments, the fuel cell (207) is composed of its principal elements, an anode section (212), a cathode section (213) and a cooling plate (214). The fuel cell cathode (213) is fed with outside air or another oxygen source. The cathode exhaust (21b) is oxygen depleted air with high humidity. The fuel cell (207) also contains a cooling plate (214) in which coolant from a coolant container (215) is flowed through pump (229). The fuel cell coolant enters the fuel cell cooling plate (214) at a relatively low temperature and exits at a high temperature, almost equivalent to the operating temperature of the fuel cell (207). This temperature can range between 40°C to 120°C. The hot fuel cell coolant is used to heat up low concentration liquid desiccant (227) originating from a low concentration liquid desiccant container (219). This heating process occurs in the desiccant regenerator (216). As the liquid desiccant is heated, its solubility in water is reduced, therefore water is released and the liquid desiccant concentration increases. The water released from the liquid desiccant is captured using high humidity cathode exhaust air in the water recovery system (217). The high humidity cathode exhaust is at a temperature similar to the operating temperature of the fuel cell, therefore it aids in maintaining the liquid desiccant warm at a temperature ranging between 40°C to 160°C and at a low solubility point. Water is diffused from the liquid desiccant to the high humidity cathode exhaust. Since the high humidity cathode exhaust air is at or close to 100% relative humidity, the water released by the liquid desiccant condenses along with the water in the air. Water condensation is captured and transferred to a water container (218). The water recovery system may also include a radiator further cools the air in the water recovery system (217), resulting in further release of water. The liquid desiccant exiting the water recovery system (217) is at high concentration and is stored in the high concentration liquid desiccant container (221). Note that water release from the desiccant and water vapor condensation are both endothermic processes, which result in cooling down of the liquid desiccant in the water recovery system (217). As will be understood, the fuel cell of Fig. 8 can be substituted with an internal combustion engine.

[0086] High concentration liquid desiccant flows from the high concentration liquid desiccant container (221) through a pump (223) to an air conditioning dehumidifier (20) that forms part of the desiccant air conditioning system (32). Outside air, that is warm and humid, enters the air conditioning dehumidifier. The air conditioner dehumidifier enables fluid contact between the water in the air and the high concentration liquid desiccant. The high concentration liquid desiccant absorbs the water in the air, substantially reducing air humidity. Although this process is exothermic, the exothermicity occurs at the surface of the desiccant, where humidity absorption occurs. Since the liquid desiccant has a specific heat, the rise in temperature is low, which reduces the elevation of air temperature. The air exiting the air conditioning dehumidifier (220) has low humidity and a temperature similar to the outside air temperature. This air is then cooled using a sensible heat coil (222) to an appropriate temperature for introduction into the air conditioned space, thus resulting in conditioned low humidity cold air (211). The liquid desiccant leaving the air conditioning dehumidifier is of low concentration (i.e., is diluted), since it has absorbed a substantial amount of water vapor. This low

concentration liquid desiccant flows to a low concentration liquid desiccant container (219). Note that in this embodiment cooling that occurs in the sensible heat coil is aided through the introduction of water transported by pump (225) from the water container (218). This water is used to create evaporative cooling of a portion or all of the low humidity air.

[0087] Note that although Fig. 8 represents each of these components separately, this is done for illustration purposes only, as Fig. 8 is describing functions not independent and distinct components. Case in point, the air conditioning dehumidifier (220) can be coupled with the sensible heat coil (222). In doing this, the liquid desiccant and the air can be cooled as dehumidification occurs, increasing the effectiveness of the process (low temperature liquid desiccant has higher water solubility). Examples of combined functions include heat and mass exchange (HMX) devices, such as those found in the ' 140 Patent, the entirety of which is incorporated herein by reference. Further, the fuel cell (207) may be replaced by an engine (e.g., an internal combustion engine) configured with a temperature regulating system that includes coolant and an exhaust system that handles exhaust generated by combustion of the fuel.

[0088] Turning to Fig. 9, a combined air conditioning power generation system is disclosed. The system includes a closed loop liquid desiccant system that utilizes exhaust from the fuel cell to regenerate liquid desiccant used to dehumidify air being supplied to a space to be air conditioned. Water from the fuel cell exhaust and the liquid desiccant regeneration is also used to provide evaporative cooling to the air conditioning system. Power generated by the fuel cell is used to power the air conditioner, the building being cooled and, where excess power is produced, the power can be sold back to the power grid or stored for future use (e.g., in batteries, capacitors, etc.). Although Figs. 8 and 9 depict a fuel cell, it should be understood that the fuel cell can be replaced by another engine (e.g., an internal combustion engine). In such instances, the internal combustion engine coolant stream will exit cooling outlet 1125 and the combustion exhaust will exit outlet 1132. [0089] As shown in Fig. 9, the combined air conditioning power generation system 100 can include a dehumidifier 1112, a fuel cell 1114, and a water recovery (WR) unit 1116. The dehumidifier 1112 can include a dehumidifier desiccant duct 1118 that contacts a dehumidifier air duct 1120. The fuel cell 1114 can include a first electrode chamber 1122, a second electrode chamber 1124, and fuel cell stack cooling plates 1126. The fuel cell stack cooling plates 1126 can be in thermal communication with the first and/or second electrode chambers 1122, 1124. In some embodiments, the first electrode 1122 is a cathode and the second electrode 1124 is an anode, while the first electrode 1122 is an anode and the second electrode 1124 is a cathode in other embodiments.

[0090] The water recovery (WR) unit 1116 can include a WR desiccant duct 1128 that contacts a WR air duct 1130. In some embodiments, the outlet 1132 of the first electrode chamber 1122 (e.g., a cathode chamber or an anode chamber) can be in fluid communication with an inlet 1134 of the WR air duct 1130. In some embodiments, such as a solid oxide fuel cell (SOFC), the first electrode chamber 1122 can be an anode chamber, while the first electrode chamber 1122 can be a cathode chamber in other embodiments. In some embodiments, the outlet 1136 of the dehumidifier desiccant duct 1118 is in fluid communication with the inlet 1138 of the WR desiccant duct 1128. In some embodiments, the outlet 140 of the WR desiccant duct 1128 is in fluid communication with an inlet 1142 of the dehumidifier desiccant duct 1118. Examples of fuel cells useful in the system 100 include, but are not limited to, proton exchange membrane fuel cells, direct methanol/ethanol fuel cells, phosphoric acid fuel cells, solid oxide fuel cells, and molten carbonate fuel cells.

[0091] In some embodiments, a first duct can be in contact with a second duct, where the first duct passes through the second duct or the second duct passes through the first duct. In some embodiments, the first duct can pass through the second duct and the direction of fluid flow in first duct can be approximately perpendicular to the direction of fluid flow in the second duct. Such arrangements may apply to any ducts in contact with one another disclosed herein.

[0092] In some embodiments, the dehumidifier desiccant duct 1118 can pass through the dehumidifier air duct 1120. In some embodiments, the dehumidifier desiccant duct 1118 and the dehumidifier air duct 1120 are on opposite sides of, or share a common wall comprising, a dehumidifier membrane 1146. In some embodiments, the dehumidifier membrane 1146 is permeable to water vapor, but otherwise does not allow the transport of liquids from one side of the dehumidifier membrane 1146 to the other. Such water vapor permeable membranes and their properties are described throughout this disclosure.

[0093] In some embodiments, the dehumidifier membrane 1146 allows water vapor in the air within the dehumidifier air duct 1120 to cross the dehumidifier membrane 1146 and pass into a desiccant stream within the dehumidifier desiccant duct 1118. In some embodiments, as a result of water vapor passing from the air in the dehumidifier air duct 1120 into the dehumidifier desiccant duct 1118, the liquid desiccant stream exiting the dehumidifier desiccant duct 1118 has a lower concentration of desiccant (higher concentration of water) than the liquid desiccant stream entering the dehumidifier desiccant duct 1118, and the air stream exiting the dehumidified air duct 1120 has a lower humidity than the air stream entering the dehumidified air duct 1120. The system 100 can be operated so that the contents of the dehumidifier desiccant duct 1118 do not pass through to the air in the dehumidifier air duct 1120.

[0094] In some embodiments, the water recovery unit 1116 includes a desiccant regeneration unit 1159 that includes the WR desiccant duct 1128 and the WR air duct 1130. In some embodiments, the WR desiccant duct 1128 and the WR air duct 1130 are on opposite sides of, or share a common wall comprising, a WR membrane 1148. In some embodiments, the WR membrane 1148 is permeable to water vapor, but otherwise does not allow the transport of liquids from one side of the WR membrane 1148 to the other. For instance, the WR

membrane 1148 can allow water in a desiccant stream within the WR desiccant duct 1128 to cross the WR membrane 1 148 and pass into the cathode exhaust stream within the WR air duct 1130.

[0095] In some embodiments, the WR membrane 1148 allows water from the WR desiccant duct 1128 to cross the WR membrane 1148 and pass into the exhaust stream within the WR air duct 1130. In some embodiments, as a result of water vapor passing from the liquid desiccant in the WR desiccant duct 1128 into the WR air duct 1130, the liquid desiccant stream exiting the WR desiccant duct 1118 has a higher concentration of desiccant (lower concentration of water) than the liquid desiccant stream entering the WR desiccant duct 1128, and the exhaust stream exiting the WR air duct 1130 has a higher humidity or water content than the exhaust stream entering the WR air duct 1130. The system 100 can be operated so that only water vapor passes from the WR desiccant duct 1128 to the WR air duct 1130. [0096] In some embodiments, the WR desiccant duct 1128 can pass through the WR air duct 1130.

[0097] In some embodiments, as shown in Fig. 9, the system 100 includes a water recovery (WR) radiator 1198. The WR radiator 1198 can include a WR radiator cooling duct 1200 and a WR radiator water feed duct 1202. The WR radiator water feed duct 1202 can be a radiator and the WR radiator cooling duct 1200 can be adapted for blowing ambient air into contact with the WR radiator water feed duct 1202. A WR radiator fan 1203 can be positioned to force air through the WR radiator cooling duct 1200 and onto the WR radiator water feed duct 1202.

[0098] An outlet 1158 of the WR air duct 1130 can be in fluid communication with an inlet 1204 of the WR radiator water feed duct 1202. In some embodiments, the WR radiator water feed duct 1202 has two outlets: a WR radiator water line 1206 and a WR radiator exhaust 1208. The WR radiator water line 1206 can be in fluid communication with an inlet 1178 of the EC water duct 1170. In some embodiments, the WR radiator exhaust 1208 can be in fluid communication with the environment, while the WR radiator exhaust 1208 can be in fluid communication with a space to be conditioned (e.g., heated) in other embodiments.

[0099] In some embodiments, the system 100 includes a heat exchanger (HX) unit 1210 that includes a HX desiccant duct 1212 contacting a HX coolant duct 1214. In some embodiments, the HX desiccant duct 1212 is in thermal communication with the HX coolant duct 1214. In some embodiments, the HX desiccant duct 1212 is not in fluid communication with the HX coolant duct 1214. The heat exchanger unit 1210 can be a counter-flow heat exchanger, such as a counter-flow, plate heat exchanger.

[0100] In some embodiments, an inlet 1216 of the HX desiccant duct 1212 is in fluid communication with the outlet 1136 of the dehumidifier desiccant duct 1118. In some embodiments, an outlet 1218 of the HX desiccant duct 1212 is in fluid communication with an inlet 1138 of the WR desiccant duct 1128. In some embodiments, an inlet 1220 of the HX coolant duct 1214 is in fluid communication with a fuel cell stack cooling plate outlet 1125. In some embodiments, an outlet 1222 of the HX coolant duct 1214 is in fluid communication with a fuel cell stack cooling plate inlet 1127.

[0101] In some embodiments, the system 100 includes a fuel cell coolant (FCC) radiator 1224. In some embodiments, the FCC radiator 1224 includes a FCC coolant duct 1226 and a FCC radiator air duct 1228. The FCC coolant duct 1226 can be a radiator and the FCC radiator air duct 1228 can be adapted for blowing ambient air into contact with the FCC coolant duct 1226. A FCC radiator fan 1229 can be positioned to force air through the FCC radiator air duct 1228 and impinge the air on the FCC coolant duct 1226.

[0102] In some embodiments, an inlet 1230 of the FCC coolant duct 1226 is in fluid communication with a HX coolant duct outlet 1222 and an outlet 1232 of the FCC coolant duct 1226 is in fluid communication with a fuel cell stack cooling plate inlet 1127. In some embodiments, the FCC radiator air duct 1228 is open to ambient air (e.g., the outdoors) at both the inlet 1234 and the outlet 1236.

[0103] In some embodiments, the outlet 1236 of the FCC radiator air duct 1228 can be in fluid communication with a space in need of conditioned air, e.g., a building. In such instances, the air exiting the outlet 1236 of the FCC radiator air duct 1228 can be used to heat the space.

[0104] In some embodiments, an inlet 1230 of the FCC coolant duct 1226 is in fluid communication with a HX coolant duct outlet 1222 and an outlet 1232 of the FCC coolant duct 1226 is in fluid communication with a fuel cell stack cooling plate inlet 1127.

[0105] As shown in the Figs. 4 and 9, in some embodiments, the combined air conditioning, power generation system 100 includes an evaporative cooling (EC) unit 1166 that includes an EC air duct 1168 for contacting cooling air with an EC water duct 1170 and an EC desiccant duct 1172. In some embodiments, the EC water duct(s) 1170 and the EC desiccant duct(s) 1172 are arranged so that fluid in the EC air duct 1168 encounters the EC water duct(s) 1170 and the EC desiccant duct(s) 1172 sequentially. In some embodiments, the EC water duct(s) 1170 and the EC desiccant duct(s) 1172 are interspersed.

[0106] The EC water duct 1170 can transfer water droplets or vapor into cooling air passing through the EC air duct 1168 in order to provide psychrometric or evaporative cooling of the cooling air. For example, as shown in Figs. 9, the EC water duct 1170 can include an EC membrane 1174 that is permeable to water vapor for providing evaporative cooling of the cooling air passing through the EC air duct 1168. In other embodiments, such as those shown in Fig. 4, the EC water duct 1170 can spray droplets of water into the cooling air passing through the EC air duct 1168. In some embodiments, the EC water duct 1170 can include a plurality of EC water conduits 1170. In some embodiments the EC water duct 1170 can be adapted to allow water to flow on the exterior portion of the EC water duct 1170 (e.g., orifices positioned along an upper portion of the EC water duct 1170). [0107] In some embodiments, such as Figs. 4 and 9, the only outlet of the EC water duct 1170 is through nozzles or the walls of the EC water duct (e.g., through orifices or the EC

membrane 1174). In some embodiments, the system 100 also includes an EC water

pump 56/1176 in fluid communication with the EC water duct 1170 for maintaining a target pressure within the EC water duct 1170. This allows the system to control the amount of psychrometric cooling utilized in the evaporative cooling unit 1166. The pressure maintained in the EC water duct 1170 should be sufficient to cause a desired amount of water molecules to pass into the EC air duct 1168. In some embodiments, the EC water pump 56/1176 is controlled using level sensor(s) or switch(s) 1177 which maintains a certain water level corresponding to a certain water flow.

[0108] In some embodiments, the system 100 can be adapted to include a desiccant loop 1240, a fuel cell coolant loop 1242, and a water recovery line 1244. Each of these loops 1240, 1242, 1244 can include one or more control pumps 1246, 1248, 1250, respectively, for transporting the relevant fluid through the loop. Each of these loops can have no fluid communication with the other loops, except for the transfer of water vapor that occurs in the desiccant regeneration unit 1159.

[0109] The desiccant loop 1240 can include the dehumidifier desiccant duct 1118 in fluid communication with the HX desiccant duct 1212 in fluid communication with the WR desiccant duct 1128 in fluid communication with the EC desiccant duct 1172 in fluid communication with the dehumidifier desiccant duct 1118. The desiccant loop 1240 can also include a high concentration liquid desiccant tank 1252a, a low concentration liquid desiccant tank 1252b, or both 1252a, 1252b. Although the low concentration liquid desiccant tank 1252b is shown between then dehumidifier desiccant duct 1118 in fluid communication with the HX desiccant duct 1212, it will be understood that the low concentration liquid desiccant tank 1252b can also be positioned between the HX desiccant duct 1212 and the WR desiccant duct 1128.

[0110] The fuel cell coolant loop 1242 can include the fuel cell stack cooling plates 1126 in fluid communication with the HX coolant duct 1214 in fluid communication with the FCC coolant duct 1226 in fluid communication with the fuel cell stack cooling plates 1126.

[0111] The water recovery line 1244 can start with the supersaturated exhaust exiting the WR air duct 1130 in fluid communication with the WR radiator water feed duct 1202 in fluid communication with the WR radiator water line 1206 in fluid communication with the EC water duct 1170.

[0112] Also described is a method of operating a combined air conditioning power generation system 100 as described herein. The method can be a continuous method. The method can include dehumidifying an air stream using a liquid desiccant stream; and regenerating the liquid desiccant stream using an exhaust stream from an electrode chamber of a fuel cell. In some embodiments, the air stream and the liquid desiccant stream are in fluid communication through a dehumidifier membrane 146 that allows moisture in the air to pass into the liquid desiccant stream.

[0113] The exhaust stream can be from an anode chamber or a cathode chamber of a fuel cell. The exhaust stream can have a high humidity (e.g., >70% RH, >80% RH, >90% RH) and a temperature above room temperature (e.g., >40°C, >50°C, >60°C, >70°C, >80°C, >90°C, or > 100°C).

[0114] In some embodiments, the method can also include capturing cooling water from the exhaust stream used in the regenerating step; and cooling the liquid desiccant stream before the dehumidifying step. The cooling step can include evaporative cooling of the liquid desiccant stream using the cooling water.

[0115] In some embodiments, the capturing step includes contacting the exhaust stream with a refrigerant stream. In some embodiments, the refrigerant stream is used for air conditioning or as a domestic or commercial water supply. The method can also include any of the interactions described with respect to the particular unit operations described herein.

[0116] A dehumidifier system that uses a liquid desiccant, such as those disclosed herein, to dehumidify an incoming air stream for air conditioning purposes is described. The design of the dehumidifier is such that heat energy is continually being removed throughout the

dehumidification process by means of, but not necessarily exclusively of, air flow from the atmosphere, water recovered from the liquid desiccant during its regeneration process, and/or through the flow of cooled liquid desiccant. The system is designed in such a way that the water that is absorbed from the ambient air and that enters into the liquid desiccant stream is recovered. This water recovery system uses a liquid cooled fuel cell stack and utilizes the heat produced from its operation to increase the temperature of the liquid desiccant and promote water desorption. The fuel cell's cathode exhaust air and humidity is also used to promote water recovery by using this stream as a water collection, conveyance and precipitation agent.

[0117] The use of liquid desiccant in the systems described herein enables regulation of the rate of air dehumidification by controlling the liquid desiccant flow. Additionally, the liquid desiccant dehumidifies air through a water vapor permeable barrier that can be composed of a microporous polymer or a water permeable polymer. In this way, liquid desiccant entrainment into the air conditioning supply air stream is prevented. The dehumidification process is isothermal, which increases the effectiveness of the air dehumidification process. This in turn results in lower liquid desiccant flow rates and reduces the size, cost and complexity of the liquid desiccant conveyance systems, such as pumps, valves, and line sizes. The continuous operation of the system relies on the capacity to regenerate the liquid desiccant from a low concentration (high water content) state to a high concentration (low water content) state. The way the fuel cell is used and the designs of the system components enables liquid desiccant regeneration to results in recovery of the water obtained from the liquid desiccant and in the generation of electricity. The resulting device, an isothermal air dehumidifier, that generates electricity as a by-product of its operation, has enormous value since it increases the overall efficiency of air-conditioning.

[0118] The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.