Dehumidification and absorption chilling using electrochemical separation

Abstract

The present disclosure includes methods and systems of absorption chilling and / or dehumidification. Specifically, the systems and methods disclosed herein utilize electrochemical separation (e.g., faradaic separation) to avoid harmful refrigerants and increase cooling and dehumidification efficiencies.

Description

DEHUMIDIFICATION AND ABSORPTION CHILLING USINGELECTROCHEMICAL SEPARATIONCROSS-REFENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 669,557, filed July 10, 2024, the entirety of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates generally to methods and systems of dehumidification and absorption chilling, and more specifically to methods and systems of dehumidification and absorption chilling using electrochemical separation.BACKGROUND

[0003] Vapor-compression (“VC”) technology has dominated refrigeration, air conditioning, and heat pumping for the past century by using hydrofluorocarbons (“HFC”). It is predicted that by 2050, HFC emissions will account for up to 20% of equivalent global CO2 emissions due to rapid growing demand for refrigeration and electrification of heating in the world. Other alternatives to HFC are being implemented, but these low Global Warming Potential (“GWP”) refrigerants are still slightly flammable, have smaller power densities and efficiencies compared to HFC, and pose other environmental concerns.

[0004] Legislation has been signed into law to curb HFC use and transition the world to a next generation refrigerant. That next generation refrigerant is uncertain and appears to be a choice between hydrofluor-ol efins (“HFO”), which acidify our water (irreparably), or natural refrigerants such as propane, which are explosive. The heating and cooling industries are trying to wean off HFC, but they do not have an acceptable alternative that has low-GWP, zerotoxicity, and zero-flammability.

[0005] In addition to using harmful refrigerants, vapor-compression utilizes a very energy intensive process for dehumidification. To remove water vapor from air, vapor-compression relies on dew-point dehumidification in which the water vapor from air is condensed onto a cold surface created by a vapor-compression driven heat pump. Historically, the dew-point dehumidification approach has dominated air conditioning for more than 100 years. However, converting water vapor to a liquid through condensation on a cold plate can require more than ten times the theoretical minimum amount of energy to remove the water vapor from the air stream.

[0006] Typical dew point settings can be about ~7-9 degrees Celsius (corresponding to 40- 50% relative humidity at 20°C intake air). As such, typical evaporator coils can be at temperatures of around 5°C to provide a sufficient driving force to reach dehumidification targets. However, for occupant comfort, the supply air comes into a room around 15-20°C (depending on outdoor temperature). Thus, the air gets cooled to around 5°C for dehumidification, and then must get reheated to about 15-20°C before it enters the room that is being conditioned. In essence, the evaporator coils overcool the air to meet dehumidification targets, and then are reheated to meet temperature comfort settings, which is an inefficient process.BRIEF SUMMARY

[0007] Provided herein are methods and systems for increasing cooling efficiency and / or dehumidification efficiency without using harmful refrigerants. The methods and systems disclosed herein can replace harmful refrigerants or thermal regeneration using electrochemical separation (e.g., faradaic separation), thereby increasing cooling and / or dehumidification efficiency.

[0008] In some embodiments, an absorption chilling system includes an absorber comprising a solution, wherein the solution comprises a solvent, a cation, and an anion, wherein the absorber is configured to condense water vapor, thereby decreasing a concentration of the cation and anion in the solution to form a diluted solution; a faradaic separator, wherein the faradaic separator is configured to reduce the cation of the diluted solution at a negative electrode and oxidize the anion of the diluted solution at a positive electrode when a voltage is applied between the positive and negative electrodes such that at least a portion of the anion and the cation are removed from the diluted solution to form a further diluted solution; and an evaporator configured to receive the further diluted solution and evaporate water of the further diluted solution to form the water vapor received by the absorber. In some embodiments, the reduced cation is stored at the negative electrode and the oxidized anion is stored at the positive electrode. In some embodiments, the faradaic separator is further configured to reverse the reduction of the cation and the oxidation of the anion during discharging of the faradaic separator to form a concentrated solution. In some embodiments, the absorber is configured to receive the concentrated solution from the faradaic separator to be used as the solution in the absorber. In some embodiments, the evaporator comprises a heat exchanger comprising a heat transfer fluid, wherein the heat transfer fluid provides heat to the further diluted solution forevaporation, thereby cooling the heat transfer fluid. In some embodiments, the cooled heat transfer fluid is used to absorb heat from a building. In some embodiments, the absorber comprises a second heat exchanger comprising a second heat transfer fluid, wherein the second heat transfer fluid receives heat from the first water vapor during condensation of the first water vapor. In some embodiments, the heated second heat transfer fluid is sent to a cooling tower.

[0009] In some embodiments, an absorption chilling method includes condensing water vapor, thereby decreasing a concentration of a cation and an anion in a solution to form a diluted solution; applying a voltage between a positive and negative electrode to reduce the cation of the diluted solution at the negative electrode and oxidize the anion of the diluted solution at the positive electrode to form a further diluted solution; and evaporating water from the further diluted solution to form the water vapor. In some embodiments, the method includes discharging the positive and negative electrodes to reverse the reduction of the cation and the oxidation of the anion to form a concentrated solution. In some embodiments, the method includes using the concentrated solution as the solution diluted by the condensed water vapor. In some embodiments, the method includes heating the further diluted solution with a heat transfer fluid for evaporation, thereby cooling the heat transfer fluid. In some embodiments, the method includes using the cooled heat transfer fluid to cool a building. In some embodiments, the method includes transferring heat from the water vapor to a second heat transfer fluid during condensation of the first water vapor.

[0010] In some embodiments, a dehumidification system includes a dehumidifier comprising a solution, wherein the solution comprises water, a cation, and an anion, and the solution absorbs water vapor from a humid air stream received by the dehumidifier, thereby decreasing a concentration of the anion and cation in the solution to form a diluted solution; a faradaic separator, wherein the faradaic separator is configured to reduce the cation of the diluted solution at a negative electrode and oxidize the anion of the diluted solution at a positive electrode when a voltage is applied between the positive and negative electrodes such that at least a portion of the anion and the cation are removed from the diluted solution to form a further diluted solution; and a humidifier configured to receive the further diluted solution and an air stream and evaporate water of the further diluted solution such that a concentration of water vapor in the air stream increases. In some embodiments, the system includes the faradaic separator is further configured to reverse the reduction of the cation and the oxidation of the anion during discharging of the faradaic separator to form a concentrated solution. In someembodiments, the dehumidifier is configured to receive the concentrated solution from the faradaic separator to be used as the solution in the dehumidifier.

[0011] In some embodiments, a dehumidification method includes removing water vapor from a humid air stream with a solution, wherein the solution comprises water, a cation, and an anion, thereby decreasing a concentration of the cation and the anion in the solution to form a diluted solution; applying a voltage between a positive electrode and a negative electrode to reduce the cation of the diluted solution at the negative electrode and oxidize the anion of the diluted solution at the positive electrode to form a further diluted solution; and increasing a concentration of water vapor in an air stream by evaporating water of the further diluted solution in the presence of the air stream. In some embodiments, the method includes discharging the positive and negative electrodes to reverse the reduction of the cation and the oxidation of the anion to form a concentrated solution. In some embodiments, the method includes using the concentrated solution as the solution diluted by the removal of water vapor from the humid air stream.

[0012] The embodiments disclosed above are only examples, and the scope of this disclosure is not limited to them. Particular embodiments may include all, some, or none of the components, elements, features, functions, operations, or steps of the embodiments disclosed above. Embodiments according to the disclosure herein are in particular disclosed in the attached claims directed to methods and systems, wherein any feature mentioned in one claim category, e.g., method, can be claimed in another claim category, e.g., system, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However, any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof are disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and / or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims.

[0013] Additional advantages will be readily apparent to those skilled in the art from the following detailed description. The examples and descriptions herein are to be regarded as illustrative in nature and not restrictive.

[0014] All publications, including patent documents, scientific articles and databases, referred to in this application are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication were individually incorporated by reference. If a definition set forth herein is contrary to or otherwise inconsistent with a definition set forth in the patents, applications, published applications and other publications that are herein incorporated by reference, the definition set forth herein prevails over the definition that is incorporated herein by reference.BRIEF DESCRIPTION OF THE FIGURES

[0015] The present application can be understood by reference to the following description taken in conjunction with the accompanying figures.

[0016] FIG. 1 illustrates an exemplary system for a standard absorption chiller process.

[0017] FIG. 2 illustrates a first exemplary faradaic deionization process in accordance with some embodiments disclosed herein.

[0018] FIG. 3 illustrates a second exemplary faradaic deionization process in accordance with some embodiments disclosed herein.

[0019] FIG. 4 illustrates a exemplary system for an absorption chiller process that utilizes faradaic separation in accordance with some embodiments disclosed herein.

[0020] FIG. 5 illustrates a second exemplary system for an absorption chiller process that utilizes faradaic separation in accordance with some embodiments disclosed herein.

[0021] FIG. 6 illustrates an exemplary system for a liquid desiccant dehumidifier process that utilizes faradaic separation in accordance with some embodiments disclosed herein.

[0022] In the Figures, like reference numerals refer to like components unless otherwise stated herein.DETAILED DESCRIPTION

[0023] Applicant has discovered an approach to increasing cooling efficiency and / or dehumidification efficiency, without using harmful refrigerants, involving electrochemical (e.g., faradaic separation) used to drive an absorption-based cooling cycle and / or a dehumidification cycle. An absorption chiller can create cold by evaporating water at low temperature (absorbing energy) and condensing that water into a highly concentrated salt solution (releasing energy).

[0024] FIG. 1 illustrates a standard or typical absorption cooling or chiller system. In some embodiments, a typical absorption chiller system can include an evaporator 7, such as a falling film over horizontal tubes or flooded evaporator, and an absorber 1 (e.g., an absorber heat and mass exchanger). In some embodiments, the evaporator can be configured to receive a solution that includes water 17 and evaporate water to form water vapor (i.e., gaseous water) 8. In some embodiments, the pressure in the evaporator can be very low (e.g. 1-2000 Pa). In this lower pressure environment, the boiling point of the water containing solution can decrease. As the water evaporates, it can cool itself down. In some embodiments, the evaporator can include a heat exchanger 24. In some embodiments, the heat exchanger in the evaporator can be a coilbased heat exchanger carrying a heat transfer fluid. In some embodiments, the heat exchanger in the evaporator can be plate and frame, shell and tube, concentric tubes, or a combination thereof. In some embodiments, the heat transfer fluid entering 18 the evaporator can provide the heat for the water to evaporate. In other words, heat can be transferred from the inlet heat transfer fluid 18 to the water containing solution (i.e., absorbed by the water containing solution), thereby evaporating the water and cooling the heat transfer fluid such that the outlet heat transfer fluid 19 is at a lower temperature (e.g., about 2-10°C) than the inlet heat transfer fluid (e.g., about 12-15°C). In some embodiments, the heat transfer fluid can include water (water mixture with glycol for example) or air. For example, in a chiller, water can be the heat transfer fluid and air can be the heat transfer fluid for an air conditioner. In some embodiments, the evaporator temperature can be about 5-6°C. In some embodiments, the inlet heat transfer fluid can be the return from an inside of a home or building and the outlet heat transfer fluid can be the outlet to the building in order to cool the building. In some embodiments, the outlet heat transfer fluid can be chilled and can be pumped through the home or building to absorb heat, and then returned to the inlet of the device to transfer the absorbed heat from the building to the evaporating water.

[0025] In some embodiments, the absorber 1 can be configured to receive the gaseous water 8 from the evaporator 7. In some embodiments, the absorber can include a concentrated solution 14. In some embodiments, the solution can be an aqueous solution that has very low water vapor pressure (e.g., about 0.2 kPa to 5 kPa). In some embodiments, the solution can include an anion, a cation, and solvent. In some embodiments, the solution can be a liquid desiccant solution. In some embodiments, liquid desiccants can be one or more salts in a solvent. In some embodiments, any suitable salts may be used provided the salt(s) is provided at a high enough concentration in water to pull additional water in. In some embodiments, the salts may include calcium chloride (CaCh), magnesium chloride (MgCh), lithium chloride (LiCl), lithium bromide (LiBr), or any combinations thereof. The salts can include be in their cation and anion forms when in the solution. For example, calcium chloride in solution can have calcium in its cation form and chloride can be in its anion form. In some embodiments, the solvent comprises or is water, acetone, ethanol, ionic liquids, ammonia, or combinations thereof. In some embodiments, the absorber can be configured to receive a concentrated solution 14. In some embodiments, the concentration of salt (i.e., concentration of anions and cations) in the concentrated liquid desiccant can be about 5-65 wt.%. In some embodiments, at these high concentrations of salt, the vapor pressure of the solvent (e.g., water) can be lowered significantly.

[0026] In some embodiments, there is a strong chemical potential that can generate a pressure difference between the gaseous water 8 entering the absorber and the concentrated solution 14 that can drive the gaseous water towards the concentrated solution. Once in contact with the concentrated solution, the gaseous water can chemically absorb into the solution, where it can condense, thereby releasing heat. In other words, the absorber can be configured to condense the gaseous water such that it further dilutes the concentrated solution. In some embodiments, the concentration of salt (concentration of anion and cation) in the diluted solution 9 is less than the concentration of salt (concentration of anion and cation) in the concentrated solution 14. In some embodiments, the concentration of salt (concentration of anion and cation) in the diluted solution can be about 0-60 wt.% or about 1-60 wt.%.

[0027] In some embodiments, the absorber can include a heat exchanger 28. In some embodiments, the heat exchanger in the absorber can be a coil-based heat exchanger carrying a heat transfer fluid, a plate and frame heat exchanger, a shell and tube heat exchanger, a spiral plate heat exchanger, a concentric tube heat exchanger, or combinations thereof. In someembodiments, the heat transfer fluid entering 20 the absorber can provide cooling for the water vapor to condense. In other words, heat can be transferred from the inlet water vapor 8 to the inlet heat transfer fluid 20, thereby condensing the gaseous water and heating the heat transfer fluid such that the outlet heat transfer fluid 21 is at a higher temperature than the inlet heat transfer fluid (e.g., water, water with other components such as glycol, or air). In some embodiments, the absorber temperature can range from slightly above ambient to about 20°C above ambient (e.g., about 20-55°C). In some embodiments, the heat can be rejected to ambient or to a cooling tower. In some embodiments, fluid 20 can be heat transfer fluid that has been cooled (e.g., from a cooling tower), it can then absorb energy from the absorber, and the heat transfer fluid 21 can leave to go back where it came from (e.g., the cooling tower). In some embodiments, fluid 20 can be air from outside that is at ambient temperature, the air can absorb energy from the absorber, and then the hot air can be rejected to ambient.

[0028] In some embodiments, the diluted solution can be “regenerated” or re-concentrated to form the concentrated solution to redo this process. As such, in some embodiments, the diluted solution 9 from the absorber can be sent (via pump 2) to a thermal generator 4 as shown in FIG. 1. In some embodiments, the thermal generator can be a natural gas fired / powered boiler, a concentrated solar collector (that can boil water in tubes that run at the focal point), and / or a condensing steam boiler. In some embodiments, the thermal generator can heat the diluted solution such that excess water is boiled off to form gaseous water stream 15. In some embodiments, the thermal generator can include a heat exchanger 22 to heat the diluted solution such that excess water is boiled off the diluted solution. The remaining solution 12 is now more concentrated since water was removed from the diluted solution. This can allow for the remaining solution 12 to be reused as the concentrated solution in the absorber (as it can once again be good at lowering the vapor pressure of water in the absorber).

[0029] The water vapor stream 15 can then be sent to a condenser 5 to condense the water vapor back into liquid water 16 by rejecting the heat of condensation 23 to air or a cooling tower. In some embodiments, the condenser can be any heat exchanger such as those disclosed herein. In some embodiments, the condenser can be a heat exchanger coil with a fan that blows ambient air over the outside of the coil while the water vapor condenses on the inside of the coil, transferring its heat to the air. The resulting liquid water from the condenser can then be sent back to the evaporator 7 to repeat the process. In some embodiments, an expansion valve can be used to reduce the pressure of the liquid water stream 16 before entering the evaporator7. In some embodiments, the pressure on the low pressure side of the expansion valve can be about 0.1 kPa to 1.5 kPa and the pressure on the high pressure side of the expansion valve can be about 50-100 kPa.

[0030] In some embodiments, the solution 12 after the thermal generator can be sent back to the absorber to restart the cooling cycle. In some embodiments, the absorption chilling system can include a solution heat exchanger 3. In some embodiments, the heat exchanger can be a plate and frame heat exchanger, a plate heat exchanger (e.g., brazed plate), a shell and tube heat exchanger, others, or combinations thereof. In some embodiments, the solution 12 from the thermal generator can heat the diluted solution 10 from pump 2 and the absorber 1. By transferring heat from the solution 12 to the diluted solution 10, the heating requirements of the thermal generator 4 can be reduced. In some embodiments, expansion valve 25 can reduce the pressure of the solution 13 leaving heat exchanger 3 before it enters the absorber. In some embodiments, solution 13 can be at a high pressure and solution 14 can be at a low pressure. Thus, the expansion valve can act to maintain that pressure difference. In some embodiments, expansion valve can maintain the pressure in the absorber and separate out the high pressure part of the system from the low pressure part of the system. Thus, concentrated solution 13 leaving heat exchanger 3 is at a lower temperature than when it entered and diluted solution 11 is at a higher temperature than when it entered heat exchanger 3.

[0031] Thermal regeneration of the liquid desiccant is very inefficient. There can be a significant thermodynamic penalty incurred using heat to drive the work of separation between the water and the liquid desiccant. If regeneration is instead done electrically, there may be no or a smaller thermodynamic penalty, and the process can approach the thermodynamic minimum amount of energy required for separation of water from the anion / cation solution.

[0032] Applicant discovered that the thermal generator 4 and condenser 5 architecture shown in FIG. 1 can be replaced with an electrochemical (e.g., faradaic) architecture. Specifically, Applicant’s approach to increasing cooling efficiency and dehumidification efficiency without using harmful refrigerants involves the faradaic separation of anions and cations in solution that can be used to drive an absorption-based cooling cycle and / or a dehumidification cycle.

[0033] FIG. 2 illustrates a faradaic deionization scheme to separate ions (anions and cations) from a solution. As shown in FIG. 1, the thermal generator 4 can boil water off from the diluted solution, thereby re-concentrating the solution for re-use in the absorber 1. The boiled watercan then be condensed in the condenser for re-use in the evaporator 7 again. By using electrochemical separation (e.g., faradaic deionization), the same or relatively similar streams can be obtained without using thermal energy as an input. Faradaic deionization can take a dilute input (e.g., diluted solution), performs electrochemically driven separation, and results in a concentrated solution (e.g., concentrated solution) and a further diluted solution. The faradaic separation can enable the electrification of the solution regeneration process, creating an electrically driven absorption chiller and / or heat pump.

[0034] In some embodiments, faradaic deionization can work by electrochemically inserting and removing ionic species from electrode materials (e.g., positive and negative electrodes) in a dual-ion battery configuration. In some embodiments, in a dual-ion battery configuration, during charge, the negative electrode can reduce the cations in solution. In some embodiments, this may convert the cationic species into an electrically neutralized solid, liquid, and / or gaseous substance. Likewise, in some embodiments, the positive electrode can oxidize the anionic species (during charge), thereby converting it into an electrically neutral form (e.g., solid, liquid, and / or gas). Thus, during charging of the faradaic separator (i.e., applying voltage between the positive and negative electrodes), the electrolyte or the solution that includes cations and anions in a solvent can be removed from the solution / solvent by electrochemical oxidation / reduction. In some embodiments, to dilute a solution, a dual-ion battery can be charged and the ions (anions / cations) can precipitate out of solution, adhere to or enter an electrode, and / or change phase. In some embodiments, to concentrate a solution, the dual-ion battery can be discharged such that the original ions in solution return to the original form and enter back into a solution.

[0035] FIG. 2 provides an example of an application of faradaic separation to transfer ions from a low concentration solution to a high concentration solution using an intermediate purge solution to prevent solvent and / or ion crossover between the solutions. FIG. 2 illustrates electrode active material 201, current collectors 202, dilute solution 203, immiscible fluid / solution 204, and concentrated solution 205. In some embodiments, the dilute solution and concentrate solution can include a solvent (e.g., water) and ions, which can further be categorized as positively charged cations 207 and negatively charged anions 206. In some embodiments, the electrochemical cell (i.e., dual-ion battery cell) can be purged (panel (1) of FIG. 2) using neutral fluid 204 that is immiscible with the dilute 203 and concentrated solutions 205. During this process, the immiscible fluid can be pumped through the electrochemical cell,pushing any fluid / solution remaining in the cell back into its respective container, stream, and / or waste. This purge can prevent crossover of the solvent and ions between the dilute and concentrated solutions. Any immiscible fluid that cross-contaminates the diluent and concentrated solutions can easily be separated with a pump or other common mechanical means.

[0036] In some embodiments, a positive 211 and negative 210 potential can be generated across the electrochemical cell (e.g., a voltage is applied between the positive and negative electrodes) leads 208, 209 and the dilute solution can be pumped through the electrochemical cell (panel (3) of FIG. 2). In some embodiments, when the dilute solution comes into contact with the electrodes (i.e., electrode active materials 201), the potential difference can cause a reaction between the electrodes and the cations 206 and anions 207. In some embodiments, this reaction can convert the cations and anions into another chemical form. For example, the cations and / or anions may precipitate out of solution, adhere to or enter an electrode, and / or change phase. In some embodiments, the reacted cations and anions can result in stable (e.g., non-ionic forms). In some embodiments, the reacted cations and anions may be stored in the electrodes 212, 213 (e.g., positive and negative electrodes) or electrode active material of the electrodes. In some embodiments, when a voltage is applied across the electrodes, the cation can be reduced at the negative electrode and the anion can be oxidized at the positive electrode.

[0037] For example, if the solutions of the system include hydrochloric acid and water, a dualion battery could reduce the H+ at the negative electrode, forming electrically neutral hydrogen gas, and oxidize the Cl- at the positive electrode, forming neutral chlorine gas. As a result, hydrochloric acid (H+ and C1-) can be removed from the solution. In some embodiments, the resulting hydrogen and chlorine gases may be absorbed by the electrodes or adhered to the electrode surfaces, where they may remain until the reaction is reversed.

[0038] As another example, if the solution of the system includes sodium chloride in water, a sodium-intercalation electrode can be used to remove sodium ions and store it in the interstitials of electrode host material (e.g., a Prussian Blue Analogue). The chloride ions can be neutralized through a redox-compensation reaction in a conductive polymer electrode (e.g., polyaniline), for example, and stored in the positive electrode. As a result, sodium chloride can be removed from the solution.

[0039] Applying a voltage between the electrodes (i.e., charging) can remove ions from solution 217. As shown in FIG. 2, that solution can then be displaced (panel (4)) by the immiscible purge solution, where the immiscible solution can push the dilute solution out of the electrochemical cell. As a result, the electrochemical cell may remain unchanged from panel (1) of FIG. 2 except that the electrodes now contain a stabilized oxidized and reduced species in and / or on the surface of the respective electrodes.

[0040] In some embodiments, the stabilized species of the electrodes can then be transferred to the concentrated solution 205 by pumping the concentrate 218 into the electrochemical cell and discharging 214 the dual-ion battery, thereby releasing the ions into the electrolyte solution and thus further increasing the concentration of the solution (panels (5) and (6) of FIG. 2). For example, hydrogen and chlorine gases can then reverse back to their ionic forms by discharging the electrochemical cell introducing HC1 (H+ and C1-) into an electrolyte or solution in the electrochemical cell. Or the sodium and chloride ions can reverse back into their original forms by discharging the electrochemical cell, introducing sodium chloride into the electrolyte or solution in the electrochemical cell.

[0041] An additional example that employs faradaic processes and minimizes crossover between dilute and concentrated solutions is shown in FIG. 3. FIG. 3 illustrates an example of an application of faradaic processing to transfer ions from a low concentration solution to a high concentration solution by transferring electrodes from one solution to another solution to prevent solvent and / or ion crossover between the solutions. In some embodiments, this configuration can involve two electrodes 320, 321 (e.g., positive and negative electrodes), but can differ from FIG. 2 in that the current collectors 322, 323 can be embedded in the dilute 324 and concentrated 325 solution tanks themselves. In some embodiments, the electrodes can be physically transported to the dilute solution tank 324, upon which they can be contacted with the current collectors 322, 323 embedded in the tank (panel (1) of FIG. 3). The current collectors can be subsequently energized by applying a potential difference across the leads, resulting in the oxidation and reduction of the anion and cation species. The oxidized and reduced forms of the ionic species can be stabilized within or on the electrodes 326 as shown in panel (2) of FIG. 3. In some embodiments, the electrode can then be physically transported from the dilute solution 324 to the concentrated solution 325 (panel (3) of FIG. 3). During this process, care can be taken to ensure that any liquid can be removed from the electrodes such that dilute solution is not carried over to the concentrated solution. The electrode materialcontaining the stabilized species can then come into contact with the current collectors of the concentrated solution tank, upon which the two leads can be connected (e.g., with a variable resistor to control current rate), and the species can be oxidized and reduced such that they return to their ionic forms in the concentrated solution to increase the concentration of the ions in the concentrated solution further (panel (4) of FIG. 3).

[0042] Using faradaic separation shown in FIGS. 2 and 3 for example, the thermal generator 4 and condenser 5 of the standard absorption chilling system of FIG. 1 can be replaced to create an absorption chilling system as shown in FIG. 4. As shown in FIG. 4, in some embodiments, absorption chiller system can include an evaporator 7 and an absorber 1 (e.g., an absorber heat and mass exchanger). In some embodiments, the evaporator can be an adiabatic evaporator, a two phase evaporator, a flooded evaporator, a falling film evaporator, or combinations thereof. In some embodiments, the evaporator can be configured to receive a water containing solution 17 and evaporate the water to form water vapor (i.e., gaseous water) 8. In some embodiments, the pressure in the evaporator can be very low (e.g., about 0.1 kPa to 2 kPa). In this lower pressure environment, the boiling point of the liquid water can decrease. As the water evaporates, it can cool itself down. In some embodiments, the evaporator can include a heat exchanger 24. In some embodiments, the heat exchanger in the evaporator can be a coil-based heat exchanger (e.g., plate and frame, brazed plate, concentric tube, shell and tube, falling film, or combinations thereof) carrying a heat transfer fluid. In some embodiments, the heat transfer fluid entering 18 the evaporator can provide the heat for the liquid water to evaporate. In other words, heat can be transferred from the inlet heat transfer fluid 18 to the water containing solution (i.e., absorbed by the water containing solution), thereby evaporating the water and cooling the heat transfer fluid such that the outlet heat transfer fluid 19 is at a lower temperature (e.g., about 2-10°C) than the inlet heat transfer fluid (e.g., water, air, water with other component such as glycol) (e.g., about 12-15°C). In some embodiments, the evaporator temperature can be about 5-6°C. In some embodiments, the inlet heat transfer fluid can be the return from an inside of a home or building and the outlet heat transfer fluid can be the outlet to the building in order to cool the building. In some embodiments, the outlet heat transfer fluid can be chilled and can be pumped through the home or building to absorb heat, and then returned to the inlet of the device to transfer the absorbed heat from the building to the evaporating water.

[0043] In some embodiments, the absorber 1 can be configured to receive the gaseous water 8 from the evaporator 7. In some embodiments, the absorber can include a concentrated solution 14. As stated above, a solution can be an aqueous solution that has very low water vapor pressure(e.g., about 0.2 kPa to 5 kPa). In some embodiments, the solution can be a liquid dessicant solution. In some embodiments, the solution can include a solvent, an anion, and a cation. In some embodiments, liquid desiccants can be one or more salts (i.e., anion and cation) in a solvent. In some embodiments, the salts can be in their anion and cation form. In some embodiments, the salts can be calcium chloride (CaCh), magnesium chloride (MgCh), lithium chloride (LiCl), lithium bromide (LiBr), or combinations thereof. In some embodiments, the solvent can be water. In some embodiments, the absorber can be configured to receive a concentrated solution 14. In some embodiments, the concentration of salt (e.g., anion and cation) in the concentrated solution can be 10-80 weight percent. In some embodiments, at these high concentrations of salt (e.g., anion and cation), the vapor pressure of the solvent (e.g., water) can be lowered significantly.

[0044] In some embodiments, there is a strong chemical potential that can generate a pressure difference between the gaseous water 8 entering the absorber and the concentrated solution 14 that can drive the gaseous water towards the concentrated solution. Once in contact with the concentrated solution, the gaseous water can chemically absorb into the solution, where it can condense, thereby releasing heat. In other words, the absorber can be configured to condense the gaseous water such that it further dilutes the concentrated solution. In some embodiments, the concentration of salt (e.g., anion and cation) in the diluted solution 9 is less than the concentration of salt (e.g., anion and cation) in the concentrated solution 14. In some embodiments, the concentration of salt (e.g., anion and cation) in the diluted liquid solution can be about 5-65 wt.%.

[0045] In some embodiments, the absorber can include a heat exchanger 28. In some embodiments, the heat exchanger in the absorber can be a coil-based heat exchanger carrying a heat transfer fluid, a plate and frame heat exchanger, a shell and tube heat exchanger, a spiral plate heat exchanger, a concentric tube heat exchanger, or combinations thereof. In some embodiments, the heat transfer fluid entering 20 the absorber can provide cooling for the water vapor to condense. In other words, heat can be transferred from the inlet water vapor 8 to the inlet heat transfer fluid 20, thereby condensing the gaseous water and heating the heat transfer fluid such that the outlet heat transfer fluid 21 is at a higher temperature than the inlet heattransfer fluid (e.g., water, water with other components such as glycol, or air). In some embodiments, the absorber temperature can range from slightly above ambient to about 20°C above ambient (e.g., about 20-55°C). In some embodiments, the heat can be rejected to ambient or to a cooling tower. In some embodiments, fluid 20 can be heat transfer fluid that has been cooled (e.g., from a cooling tower), it can then absorb energy from the absorber, and the heat transfer fluid 21 can leave to go back where it came from (e.g., the cooling tower). In some embodiments, fluid 20 can be air from outside that is at ambient temperature, the air can absorb energy from the absorber, and then the hot air can be rejected to ambient.

[0046] In some embodiments, the diluted solution can be “regenerated” or re-concentrated to form the concentrated solution to redo this process. As such, in some embodiments, the diluted solution 9 from the absorber can be sent (via pump 2) to faradaic separator system 57 such as that of FIGS. 2-3. In some embodiments, a diluted solution 10 from the absorber can be sent to a faradaic separator system 57. In some embodiments, the faradaic separator system includes a positive electrode and a negative electrode. In some embodiments the faradaic separator system is configured to reduce the cation of the diluted solution at the negative electrode and oxidize the anion of the diluted solution at the positive electrode when a voltage is applied between the positive and negative electrode such that at least a portion of the anion and the cation are removed from the diluted solution to form a further diluted solution. As such, the concentration of the anions and cations in the further diluted solution is less than that of the diluted solution from absorber.

[0047] In some embodiments, the further diluted solution 34 from the faradaic separation system can then be sent back to the evaporator 7 to repeat the process. In some embodiments, an expansion valve can be used to reduce the pressure of the further diluted solution 34 before entering the evaporator 7. In some embodiments, the pressure on the low pressure side of the expansion valve can be about 0.1 kPa to 1.5 kPa and the pressure on the high pressure side of the expansion valve can be about 50-100 kPa.

[0048] In some embodiments, after the diluted solution is further diluted, the faradaic separation system can be discharged in order to concentrate a solution with the previously removed anions / cations. In some embodiments, the faradaic separation system can reverse the reduction of the cation and the oxidation of the anion during discharging of the faradaic separation system to form a concentrated solution as described with respect to FIGS. 2-3, forexample. In some embodiments, the concentrated solution 35 after the faradaic separation system can be sent back to the absorber to restart the cooling cycle.

[0049] In some embodiments, an electrochemically driven absorption chiller system can be configured in a manner similar to that in FIG. 5. In some embodiments, complete purification of water is not required which can make the system more practical. In addition to the previously described absorption chilling system of FIG. 4, FIG. 5 includes a diluted solution reservoir 49 and a concentrated solution reservoir 50 with dilute streams 607, 608 and concentrated streams 605, 606 leaving and entering faradaic separator system 57. In some embodiments, fluid from the diluted solution reservoir 49 can be pumped to the evaporator 7, where water vapor can flash off. In some embodiments, the heat transfer fluid entering 18 the evaporator can provide the heat for the liquid water to evaporate. In other words, heat can be transferred from the inlet heat transfer fluid 18 to the water containing solution (i.e., absorbed by the water containing solution), thereby evaporating the water and cooling the heat transfer fluid such that the outlet heat transfer fluid 19 is at a lower temperature than the inlet heat transfer fluid. The solution / fluid received by the evaporator can now be more concentrated 609 and can be pumped (via pump 604) back to the diluted solution reservoir 49 (as stream 610). This can increase the concentration of the solution in the diluted solution reservoir 49.

[0050] In some embodiments, solution 35 from the concentrated solution reservoir 50 can be sent to the absorber, where a vapor pressure difference between the pure water vapor and the concentrated solution can cause the pure water vapor to condense into the concentrated solution. In other words, heat can be transferred from the inlet water vapor 8 to the inlet heat transfer fluid 20, thereby condensing the gaseous water and heating the heat transfer fluid such that the outlet heat transfer fluid 21 is at a higher temperature than the inlet heat transfer fluid. In some embodiments, a diluted solution 10 from the absorber can be sent to the concentrated solution reservoir 50, which can reduce the concentration of the reservoir. In some embodiments, the dilution of the concentrated reservoir and the concentration of the diluted reservoir may occur simultaneously or in parallel.

[0051] By the nature of this system, the diluted solution reservoir 49 can become slightly concentrated and the concentrated solution reservoir 50 can become slightly diluted. To restore the balance or original parameters, solution 608 from the diluted solution reservoir 49 can be sent to the faradaic separator system 57. The faradaic separator system can then be charged, which can remove ions from the solution inside the system, thereby decreasing theconcentration of the solution inside. After charging, the now diluted solution 607 can be displaced and return to the diluted solution reservoir 49, which may restore the reservoir’s original concentration. In some embodiments, solution 605 from concentrated solution reservoir 50 can be sent to the faradaic separator system 57, upon which the system can be discharged, thereby releasing the ions into the solution inside the system and concentrating the solution. After discharging, the now concentrated solution 606 can be displaced and return to the concentrated solution reservoir 50, which may restore the reservoir’s original concentration. In some embodiments, after a full charge / discharge cycle of the faradaic separator system, the original system concentration levels can be restored and can continue operating to cool down the evaporator and heat up the absorber. However, in some embodiments, both water and ions are transported from the diluted solution reservoir to the concentrated solution reservoir, and although the original concentration of the diluted and concentrated reservoirs are restored after a full charge / discharge cycle of the faradaic separator system, the absolute mass of the diluted reservoir can be diminished and the absolute mass of the concentrated reservoir can be increased. To restore the mass balance of the system, an appropriate amount of concentrated solution (e.g., ions and water) can be transported to the diluted reservoir in exact balance with the net transport of ions through the faradaic separator and water in the evaporator / absorber. That transport can take place in the faradaic separator, or a separate trickle stream that connects the concentrated reservoir to the diluted reservoir.

[0052] With respect to dehumidification, another way of dehumidifying the air besides dew point dehumidification is through liquid desiccant dehumidification. Liquid desiccant dehumidification can approach the theoretical minimum energy of dehumidification. In some embodiments, liquid desiccant dehumidification works by interfacing the liquid desiccant solution with humid air, and the moisture in the air is drawn to the liquid desiccant solution (due to a vapor pressure difference driven by a chemical potential between the air stream and the desiccant) and is absorbed into the solution and condensed, resulting in a less humid air stream and more dilute liquid desiccant solution. As water is absorbed into the liquid desiccant solution, it can become so dilute that the vapor pressure difference between it and the water vapor in the air stream becomes so small that absorption can no longer occur. The liquid desiccant solution then can be “regenerated” or re-concentrated by removing the water that it just absorbed. In some embodiments, traditional regeneration is done thermally.

[0053] Similar to the absorption chilling system, Applicant discovered that the thermal generator can be replaced with an electrochemical separation architecture. FIG. 6 illustrates an exemplary system for a liquid desiccant dehumidifier process that utilizes faradaic separation. The solutions described in FIG. 6 can be any of the solutions previously described herein. As shown in FIG. 6, concentrated solution 61 from concentrated solution reservoir 50 can be inserted (e.g., via spraying) into a dehumidifier 55 that receives a humid air stream 64. In some embodiments, the dehumidifier can be a chamber where concentrated solution and an air stream interact. In some embodiments, the concentrated solution can be sprayed into an incoming humid air stream. In some embodiments, the water vapor in the air stream can be absorbed by the concentrated solution to form a diluted solution 68 in the dehumidifier. In some embodiments, the water in the humid air stream can condense, diluting the concentrated solution and heating it up (due to heat of mixing and condensation). The resulting outlet air stream(s) 66 from the dehumidifier has less water content. In other words, the humidity of the air stream is lowered by the dehumidifier.

[0054] In some embodiments, a further diluted solution that includes water 59 from a further diluted solution reservoir 49 can be inserted (e.g., via spraying) into a humidifier 54 that receives an air stream 63. In some embodiments, the further diluted solution can be sprayed into an incoming air stream. In some embodiments, water can evaporate in the humidifier and is transferred into the air stream raising the humidity of the air and leaving as humid air 65. This evaporation can cool the diluted solution that enters the humidifier.

[0055] In some embodiments, the cooled solution 67 and the diluted solution 68 can be sent to a heat exchanger 56. In some embodiments, the heat exchanger can be a plate heat exchanger, brazed plate heat exchanger, shell and tube heat exchanger, spiral plate heat exchanger, double pipe heat exchanger, or combinations thereof. In the heat exchanger, heat from the diluted solution 68 can be transferred to the cooled solution 67. In some embodiments, the outlet further diluted solution 58 from the heat exchanger 56 can be sent back to further diluted solution reservoir 49. In some embodiments, the outlet diluted liquid desiccant 58a from the heat exchanger 56 can be sent back to the concentrated solution reservoir 50.

[0056] In some embodiments, diluted solution 33a from the further diluted solution reservoir 49 can be sent to a faradaic separation system similar to that shown in FIGS. 2-3. For example, diluted solution 33a can be sent to a faradaic separator that includes a positive and negative electrode. The faradaic separator can reduce the cation of the diluted solution 33a at thenegative electrode and oxidize the anion of the diluted solution 33a at the positive electrode when a voltage is applied between the electrodes such that at least a portion of the anion and the cation are removed from the diluted solution to form a further diluted solution. The further diluted solution 34a can be returned to the further diluted solution reservoir 49. In some embodiments, a concentrated solution 33b can be sent to the faradaic separator. In some embodiments, the faradaic separator can be configured to reverse the reduction of the cation and the oxidation of the anion during discharging of the faradaic separator to further concentrate the concentrated solution to form further concentrated solution 35. This further concentrated solution can then be sent back to concentrated solution reservoir 50 so the process can be repeated. Similar to FIG. 5, in some embodiments, after a full charge / discharge cycle of the faradaic separator system, the original system of FIG. 6 can be restored and can continue operate to humidify / dehumidify. In other words, in some embodiments, the concentrations of both reservoirs can be returned to their original concentrations by virtue of the faradaic separation system.ADDITIONAL DEFINITIONS

[0057] Unless defined otherwise, all terms of art, notations and other technical and scientific terms or terminology used herein are intended to have the same meaning as is commonly understood by one of ordinary skill in the art to which the claimed subject matter pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and / or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art.

[0058] Reference to “about” a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, description referring to “about X” includes description of “X”. In addition, reference to phrases “less than”, “greater than”, “at most”, “at least”, “less than or equal to”, “greater than or equal to”, or other similar phrases followed by a string of values or parameters is meant to apply the phrase to each value or parameter in the string of values or parameters.

[0059] This application discloses several numerical ranges in the text and figures. The numerical ranges disclosed inherently support any range or value within the disclosed numerical ranges, including the endpoints, even though a precise range limitation is not stated verbatim in the specification because this disclosure can be practiced throughout the disclosed numerical ranges.

[0060] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is also to be understood that the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It is further to be understood that the terms “includes, “including,” “comprises,” and / or “comprising,” when used herein, specify the presence of stated features, integers, steps, operations, elements, components, and / or units but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, units, and / or groups thereof.

[0061] The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages.

Claims

CLAIMS1. An absorption chilling system, comprising: an absorber comprising a solution, wherein the solution comprises a solvent, a cation, and an anion, wherein the absorber is configured to condense water vapor, thereby decreasing a concentration of the cation and anion in the solution to form a diluted solution; a faradaic separator, wherein the faradaic separator is configured to reduce the cation of the diluted solution at a negative electrode and oxidize the anion of the diluted solution at a positive electrode when a voltage is applied between the positive and negative electrodes such that at least a portion of the anion and the cation are removed from the diluted solution to form a further diluted solution; and an evaporator configured to receive the further diluted solution and evaporate water of the further diluted solution to form the water vapor received by the absorber.

2. The system of claim 1, wherein the reduced cation is stored at the negative electrode and the oxidized anion is stored at the positive electrode.

3. The system of any one of claims 1-2, wherein the faradaic separator is further configured to reverse the reduction of the cation and the oxidation of the anion during discharging of the faradaic separator to form a concentrated solution.

4. The system of claim 3, wherein the absorber is configured to receive the concentrated solution from the faradaic separator to be used as the solution in the absorber.

5. The system of any one of claims 1-4, wherein the evaporator comprises a heat exchanger comprising a heat transfer fluid, wherein the heat transfer fluid provides heat to the further diluted solution for evaporation, thereby cooling the heat transfer fluid.

6. The system of claim 5, wherein the cooled heat transfer fluid is used to absorb heat from a building.

7. The system of any one of claims 1-6, wherein the absorber comprises a second heat exchanger comprising a second heat transfer fluid, wherein the second heat transfer fluid receives heat from the first water vapor during condensation of the first water vapor.

8. The system of claim 7, wherein the heated second heat transfer fluid is sent to a cooling tower.

9. An absorption chilling method, comprising: condensing water vapor, thereby decreasing a concentration of a cation and an anion in a solution to form a diluted solution; applying a voltage between a positive and negative electrode to reduce the cation of the diluted solution at the negative electrode and oxidize the anion of the diluted solution at the positive electrode to form a further diluted solution; and evaporating water from the further diluted solution to form the water vapor.

10. The method of claim 9, further comprising discharging the positive and negative electrodes to reverse the reduction of the cation and the oxidation of the anion to form a concentrated solution.

11. The method of claim 10, using the concentrated solution as the solution diluted by the condensed water vapor.

12. The method of any one of claims 9-11, further comprising heating the further diluted solution with a heat transfer fluid for evaporation, thereby cooling the heat transfer fluid.

13. The method of claim 12, using the cooled heat transfer fluid to cool a building.

14. The method of any one of claims 9-13, transferring heat from the water vapor to a second heat transfer fluid during condensation of the first water vapor.

15. A dehumidification system, comprising: a dehumidifier comprising a solution, wherein the solution comprises water, a cation, and an anion, and the solution absorbs water vapor from a humid air stream received by the dehumidifier, thereby decreasing a concentration of the anion and cation in the solution to form a diluted solution; a faradaic separator, wherein the faradaic separator is configured to reduce the cation of the diluted solution at a negative electrode and oxidize the anion of the diluted solution at a positive electrode when a voltage is applied between the positiveand negative electrodes such that at least a portion of the anion and the cation are removed from the diluted solution to form a further diluted solution; and a humidifier configured to receive the further diluted solution and an air stream and evaporate water of the further diluted solution such that a concentration of water vapor in the air stream increases.

16. The system of claim 15, wherein the faradaic separator is further configured to reverse the reduction of the cation and the oxidation of the anion during discharging of the faradaic separator to form a concentrated solution.

17. The system of claim 16, wherein the dehumidifier is configured to receive the concentrated solution from the faradaic separator to be used as the solution in the dehumidifier18. A dehumidification method, comprising: removing water vapor from a humid air stream with a solution, wherein the solution comprises water, a cation, and an anion, thereby decreasing a concentration of the cation and the anion in the solution to form a diluted solution; applying a voltage between a positive electrode and a negative electrode to reduce the cation of the diluted solution at the negative electrode and oxidize the anion of the diluted solution at the positive electrode to form a further diluted solution; and increasing a concentration of water vapor in an air stream by evaporating water of the further diluted solution in the presence of the air stream.

19. The method of claim 18, further comprising discharging the positive and negative electrodes to reverse the reduction of the cation and the oxidation of the anion to form a concentrated solution.

20. The method of claim 19, using the concentrated solution as the solution diluted by the removal of water vapor from the humid air stream.

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