Heat Pump-Based Water Harvesting Systems

Abstract

Water harvesting systems and methods of making and using such water harvesting systems, for capturing water from surrounding air using configurations that reduce overall energy costs and improves water harvesting cycle efficiency in the water harvesting system. In particular embodiments, the water harvesting system can be configured for dehumidification-humidification of air, and a method in the water harvesting system for dehumidification-humidification to control moisture level in the air conditioned by the water harvesting system. The systems and methods use sorbent materials, such as metal-organic frameworks, to adsorb water from the air. The systems and methods desorb this water in the form of water vapor, and the water vapor can be condensed into liquid water and collected to dehumidify air conditioned by the water harvesting system. The collected liquid water can be sprayed to humidify air conditioned by the water harvesting system.

Claims

1. An atmospheric water harvesting system, comprising: a heat pump having a hot side heat exchanger and a cold side heat exchanger; an adsorption unit comprising a sorbent module, said sorbent module contains one or more sorbents, said adsorption unit disposed physically separate from said heat pump; a desorption chamber connected to or positioned in close proximity to said hot side heat exchanger of said heat pump, said desorption chamber configured to operate at an average desorption temperature; and a condensation chamber encompassing or positioned in close proximity to said cold side heat exchanger of said heat pump, wherein said condensation chamber is configured to operate at an average condensation temperature.

2. The system of claim 1, further comprising: a water collection tank connected to said condensation chamber, said water collection tank configured to collect water condensed from said condensation chamber; a water pump connected to said water collection tank, configured to receive said water from said collection tank; a drain connected to said collection tank; a sprayer connected to said water pump and positioned in proximity to an indoor outlet; a bypass unit positioned in proximity to the adsorption unit, configured to transfer air from an outdoor inlet or indoor inlet; an adsorption fan positioned in proximity to said adsorption unit and said bypass unit to transfer air from said outdoor inlet or said indoor inlets into the adsorption unit and the bypass unit; an indoor/outdoor inlet damper configured to control flow of air into the adsorption unit and the bypass unit from said outdoor inlet or said indoor inlet; an adsorption damper configured to direct a portion of airflow into the adsorption unit and a portion of airflow into the bypass unit; and an indoor/outdoor outlet damper configured to control flow of air out of the adsorption unit and the bypass unit into an outdoor outlet or an indoor outlet, said system adapted to switch operation between a first mode to dehumidify said air from said outdoor inlet to said indoor outlet, a second mode to humidify air from outdoor inlet to indoor outlet, a third mode to dehumidify air recirculated from said indoor inlet to said indoor outlet, and fourth mode to humidify air recirculated from said indoor inlet to said indoor outlet.

3. The system of claim 2, wherein in said first mode: said indoor/outdoor inlet damper closes said indoor inlet and opens said outdoor inlet, to transfer air from said outdoor inlet to said adsorption unit and to said bypass unit; said adsorption damper controls said portion of airflow into the adsorption unit and said portion of airflow into said bypass unit; said indoor/outdoor outlet damper closes said outdoor outlet and opens said indoor outlet to transfer dehumidified air from said adsorption unit through said indoor outlet; said transfer mechanism transfers said sorbent module at least partially saturated with water from said adsorption unit into said desorption chamber, wherein water desorbs from said one or more sorbents contained in said sorbent module, wherein said water desorbed from said one or more sorbents condenses in said condensation chamber; said water condensed in said condensation chamber collects in said water collection tank, wherein at least a portion of said water collected in said water collection tank transferred to a drain; and said water pump remains in an off condition.

4. The system of claim 2, wherein in said second mode: said indoor/outdoor inlet damper closes an indoor inlet and opens said outdoor inlet to transfer air from said outdoor inlet to said adsorption unit and to said bypass unit; said adsorption damper closes said bypass unit and opens said adsorption unit; said indoor/outdoor outlet damper partially opens said outdoor outlet and said indoor outlet to transfer dehumidified air from said adsorption through said indoor outlet and through said outdoor outlet; said transfer mechanism transfers said sorbent module at least partially saturated with water from said adsorption unit into said desorption chamber, wherein water desorbs from said one or more sorbents contained in said sorbent module, wherein said water desorbed from said one or more sorbents condenses in said condensation chamber; and said water condensed in said condensation chamber collects in said water collection tank, wherein at least a portion of said water collected in said water collection tank transferred to a drain; at least a portion of said water in water collection tank transferred by said water pump to said sprayer to humidify air transferred through the indoor outlet, said drain remains in an off condition.

5. The system of claim 2, wherein in said third mode: said indoor/outdoor inlet damper closes said outdoor inlet and opens said indoor inlet to transfer air from said indoor inlet to said adsorption unit and to said bypass unit; said adsorption damper controls said portion of airflow into the adsorption unit and said portion of airflow into said bypass unit; said indoor/outdoor outlet damper closes said outdoor outlet and opens said indoor outlet, to transfer dehumidified air from said adsorption unit through said indoor outlet; said transfer mechanism transfers said sorbent module at least partially saturated with water from said adsorption unit into said desorption chamber, wherein water desorbs from said one or more sorbents contained in said sorbent module, wherein said water desorbed from said one or more sorbents condenses in said condensation chamber; said water condensed in said condensation chamber collects in said water collection tank, wherein at least a portion of said water collected in said water collection tank transferred to a drain; and said water pump remains in an off condition.

6. The system of claim 2, wherein in said fourth mode, said system operates in a first configuration and subsequently said system operates in a second configuration, wherein said system in first configuration: said indoor/outdoor inlet damper closes said indoor inlet and opens said outdoor inlet, to transfer air to said adsorption unit and said bypass unit; said adsorption damper closes said bypass unit and opens said adsorption unit; said indoor/outdoor outlet damper closes said indoor outlet and opens said outdoor outlet to transfer air from said adsorption unit through said outdoor outlet; said transfer mechanism transfers said sorbent module at least partially saturated with water from said adsorption unit into said desorption chamber, wherein water desorbs from said one or more sorbents contained in said sorbent module, wherein said water desorbed from said one or more sorbents condenses in said condensation chamber; said water condensed in said condensation chamber collects in said water collection tank, said water pump remains in an off condition, and wherein said system in said second configuration: said indoor/outdoor inlet damper closes said outdoor inlet and opens said indoor inlet, to allow air to transfer to said absorbent unit and said bypass unit; said adsorption damper closes said adsorption unit and opens said bypass unit; said indoor/outdoor outlet damper closes said outdoor outlet and opens said indoor outlet to transfer air from said bypass unit through said indoor outlet; at least a portion of said water in water collection tank transferred by said water pump to said sprayer to humidify air transferred through the indoor outlet, said drain remains in an off condition.

7. The system of claim 1, wherein operation of said system at said average desorption temperature and said average condensation temperature for the system to (i) achieve a lowest energy per liter of water produced with the one or more sorbents, and (ii) maintain a desorption temperature high enough to sustain a target rate of desorption.

8. The system of claim 1, further comprising at least one recirculation fan configured to: (i) transfer heat from said hot side heat exchanger to said sorbent module in said desorption chamber, and (ii) drive desorption of water from said sorbent module to achieve a higher concentration of water in said desorption chamber.

9. The system of claim 1, further comprising at least one desorption-condenser recirculation fan configured to (i) transfer water desorbed from said sorbent module in said desorption chamber to said condensation chamber, and (ii) recirculate remaining desorbed water from said sorbent module in the condensation chamber back into the desorption chamber.

10. The system of claim 1, further comprising a transfer mechanism configured to (i) transfer said sorbent module at least partially saturated with water from said adsorption unit into said desorption chamber, and (ii) transfer said sorbent module at least partially desorbed of said water from said desorption chamber back to said adsorption unit.

11. The system of claim 1, further comprising a secondary hot side heat exchanger.

12. The system of claim 1, further comprising one or more control components to regulate said heat pump.

13. The system of claim 1, wherein the system further comprises a water collection tank.

14. The system of claim 1, wherein one or more sorbents comprises a metal-organic framework.

15. The system of claim 14, wherein said metal-organic framework has an isotherm step of about 20% relative humidity at about 25° C.

16. The system of claim 15, wherein said desorption temperature occurs in a range of about 130° C. to about 140° C., and wherein said condensation temperature occurs in a range of about 85° C. to about 95° C.

17. The system of claim 14, wherein said metal-organic framework has an isotherm step of about 40% relative humidity at about 25° C.

18. The system of claim 17, wherein said desorption temperature occurs in a range of about 115° C. to about 125° C., and wherein said condensation temperature occurs in a range of about 85° C. to about 95° C.

19. The system of claim 14, wherein said metal-organic framework has an isotherm step of about 60% relative humidity at about 25° C.

20. The system of claim 19, wherein said desorption temperature occurs in a range of about 100° C. to about 110° C., and wherein said condensation temperature occurs in a range of about 85° C. to about 95° C.

21-25. (canceled)

Description

IV. DESCRIPTION OF THE FIGURES

[0016] The present application can be best understood by reference to the following description taken in conjunction with the accompanying figures included in the specification.

[0017] FIG. 1 depicts a schematic of a particular embodiment of a heat pump-based water harvesting system.

[0018] FIG. 2A depicts a particular embodiment of a heat pump-based water harvesting system that includes a rotating carousel configured to continuously move fully or partially saturated MOF modules into the desorption chamber of the desorption/condensation unit for desorption.

[0019] FIG. 2B depicts another particular embodiment of a heat pump-based water harvesting system that includes a multi-axis robotic arm configured to switch the MOF modules between the adsorption unit and the desorption chamber.

[0020] FIG. 3 depicts a schematic of a particular embodiment of a thermal coupling between a “condenser” hot side heat exchanger and a MOF module in a desorption chamber.

[0021] FIG. 4 depicts a schematic of a particular embodiment a heat pump-based water harvesting system configured for water vapor condensation and liquid water collection.

[0022] FIG. 5 depicts parts of a particular embodiment of a heat pump-based water harvesting system in which temperature, humidity, or velocity of circulating air, and combinations thereof, are measured.

[0023] FIG. 6 depicts a particular embodiment of a water harvesting system configured to dehumidify-humidify air and which can operate to dehumidify outdoor air to address mode (i).

[0024] FIG. 7 depicts a particular embodiment of a water harvesting system configured to dehumidify-humidify air and which can operate to humidify outdoor air to address mode (ii).

[0025] FIG. 8 depicts particular embodiment of a water harvesting system configured to dehumidify-humidify air and which can be operated to dehumidify recirculated indoor air to address mode (iii).

[0026] FIG. 9A depicts a particular embodiment of a water harvesting system configured to dehumidify-humidify air and which can be operated to humidify recirculated indoor air to address mode (iv), including adsorption of water from the air.

[0027] FIG. 9B depicts a particular embodiment of a water harvesting system configured to dehumidify-humidify air and which can be operated to humidify recirculated indoor to address mode (iv), including introducing water collected by adsorption from the air into recirculated indoor air.

V. DETAILED DESCRIPTION

[0028] The following description sets forth illustrative examples of heat pump-based water harvesting systems (1), methods of making heat pump-based water harvesting systems, and methods of using heat pump-based water harvesting systems. It should be recognized, however, that the examples of heat pump-based water harvesting system (1) provided by the description are not intended to limit the breadth or scope of the description, but instead to provide examples sufficient for a person of ordinary skill in the art to make and use the full breadth and scope of the invention.

[0029] Now, with primary reference to FIGS. 1 through 5, illustrative examples of a sorbent-based water harvesting system (1) methods of making and using the sorbent-based water harvesting systems (1) described herein. In some embodiments, the system (1) includes an adsorption unit (3), such as an adsorption rack, that that holds one or more sorbent modules (4) containing at least one sorbent material (5). Air (6) can flow across one or more sorbent modules (4), leading to adsorption of water (7) from the surrounding air (6) by the sorbent material (5) therein. The system (1) can include a transfer mechanism (8), which in particular embodiments can be a carousel (8a) (as shown in the example of FIG. 2A) or can be a robotic arm (8b) (as shown in the example of FIG. 2B). Once one or more of the sorbent modules (4) reach a target level and/or a target rate of adsorption, the transfer mechanism (8) can move the one or more sorbent modules (4) containing adsorbed water from the adsorption unit (3) to a desorption desorption/condensation unit (2) including a desorption chamber (9) into which the sorbent module (4) can be placed for desorption of water (7). In some embodiments, the desorption chamber (9) includes a recirculation fan (10) that blows air or an air/water mixture (11) across a hot side heat exchanger (12) of a heat pump (2a) through the one or more sorbent modules (4) to effectively recover condensation energy and use it for desorption of water (7) from the sorbent module (4). Once a target water concentration is achieved in the desorption chamber (9), in particular embodiments, the system (1) can turn on a desorption-condenser recirculation fan (13) to transfer hot water vapor (14) from the desorption chamber (9) to a cold side heat exchanger (15) of the heat pump (2) encompassed in, or positioned in closer proximity to, a condensation chamber (16). In some variations, the average desorption temperature and/or average condensation temperature for the system (1) can be configured to achieve the lowest energy per liter of water (7) produced with the sorbent material (5) and can keep the desorption temperature high enough to sustain a target desorption rate. Upon water depletion or reaching a water depletion level of the sorbent module (4), the transfer mechanism (8) can remove the one or more sorbent modules (4) from the desorption chamber (9) and places the one or more sorbent modules (4) back into the adsorption unit (3). Particular embodiments of the sorbent-based water harvesting system (1) can achieve increased water adsorption, as well as continuous desorption and condensation at elevated temperatures.

[0030] In particular embodiments, as depicted in FIG. 2A, the example system (1) utilizes a carousel (8a) which rotates one or more sorbent module(s) (4). While one or more sorbent modules (4) are being desorbed in the desorption chamber (9), the remaining sorbent modules (4) can be exposed to humid environmental air (6). In particular embodiments, as depicted in FIG. 2B, a robotic arm (8b) can be utilized to transfer the one or more sorbent modules (4) from an adsorption rack (17) to the desorption chamber (9). Again, with reference to FIG. 1, in particular embodiments, the heat-pump (2a) includes a heat exchanger (18), which has a hot side heat exchanger (12) and a cold side heat exchanger (15). In some variations, the heat-pump (2a) can include a compressor (19), an expansion valve (20), a main “condenser” or hot-side heat exchanger (21), a secondary hot-side heat exchanger (22), an “evaporator” or cold-side heat exchanger (23), and other control components designed to operate at elevated temperatures. For example, in particular embodiments, the “condenser” or hot side of the heat exchanger (21) can be set to operate at temperatures in the range of about 90° C. to about 160° C., and the “evaporator” or cold-side heat exchanger (23) can be set to operate at temperatures in the range of about 40° C. to about 95° C.

[0031] Again, with reference to FIG. 1, the “condenser” or hot side heat exchanger (21) in the desorption chamber (9) and the “evaporator” or cold-side heat exchanger (23) in the condensation chamber (16) can be respectively coupled to a heat sink(s) (24a, 24b) to provide substantially constant or constant temperature operation when the sorbent modules (4) move in and out of the desorption chamber (9). The heat sink(s) (24a, 24b) can be a metal block or any other material of high thermal mass in both the desorption chamber (9) and condensation chambers (16). It can also be liquid water (7) in the condensation chamber (16).

[0032] The performance of a heat pump system can generally be modelled by the following equations:

[00001]$$\begin{gathered} \begin{array}{cc}W=\frac{Q_c}{\mathrm{COP}} \\ \mathrm{and}& \left(1\right)\end{array} \end{gathered}$$$\begin{array}{cc}\mathrm{COP}=f\frac{T_c}{T_h-T_c}& \left(2\right)\end{array}$

where W is the work input by the compressor (19), Qc is the energy extracted from the cold-side heat exchanger (23), COP is the coefficient of performance, T.sub.h is the temperature of the hot-side heat exchanger (21), T.sub.c is the temperature of the cold-side heat exchanger (23), and f is an empirical coefficient based on practical design of the system (1). In some variations, f is between about 0.4 to about 0.6. Low T.sub.h−T.sub.c and high T.sub.c values typically lead to a more energy-efficient design of the heat pump (2).

[0033] In certain embodiments, the system (1) and methods of using the system (1) can be devised to ensure effective thermal coupling between the hot-side heat exchanger (21) and the desorbing sorbent module(s) (4). Hot water vapor (14) generated during desorption can be directed to the condensation chamber (16) which contains the “evaporator” or cold-side heat exchanger (23) where the water vapor (14) can be condensed into water (6). Liquid water (7) can then be collected in a water tank (25). The residual saturated and relatively cold water vapor (14) can be recirculated back into the desorption chamber (9) to avoid excessive water loss in the environment.

[0034] In some variations, the system (1) can further include a computer (26) coupled to one or more ambient air temperature sensors (27) and/or ambient air humidity sensors (28) located outside of the desorption chamber (9) and condensation chamber (16) adapted to or configured to measure ambient air temperature and/or ambient air humidity of the environment surrounding the system (1). The computer (26) can be respectively coupled to one or more temperature sensors (29a, 29b) and/or one or more humidity sensors (30a, 30b) and/or one or more airflow sensors (31a, 31b) that can be respectively located inside the desorption chamber (9) and/or the condensation chamber (16) to measure respective desorption chamber temperature and/or humidity, and/or condensation chamber temperature and/or humidity. The temperature and/or humidity measurements based on readings from the desorption chamber and condensation chamber sensors (29a, 29b, 30a, 30b) and the environment temperature and/or humidity measurements based on readings from the ambient temperature and humidity sensors (27, 28) can be used under the control of the computer (26) implementing a water harvesting algorithm (32) to adjust operating parameters of the system (1), for example, to modify performance of the system (1) in terms of energy use, water production, and operation of the heat-pump (2a).

[0035] Any suitable sorbent material (5) can be used in embodiments of the system (1) and methods described herein. In particular embodiments, the sorbent material (5) can include one or more metal-organic frameworks (“MOFs”). Generally, MOFs offer unique characteristics that are desirable for harvesting water (7) from air (6). See e.g. H. Furukawa et al., Water Adsorption in Porous Metal-Organic Frameworks and Related Materials, J. Am. Chem. Soc. 2014, 136, 11, 4369-4381. MOFs may be characterized by high water uptake and step-like characteristics for water uptake versus relative humidity (“RH”). In some variations, suitable sorbent materials (5), including MOFs, have such an isotherm step, which can be tailored to various climates. See e.g. WO2020112899. The isotherm step is typically a weak function of temperature due to hydrogen binding between the interior of the MOF pore and the water molecules. The step isotherm enables water capture and release by MOF in a very narrow range of relative humidity (about 3 to about 5% of RH).

[0036] In some variations, the MOF is: MOF-303: Al(OH)(HPDC), where HPDC is 1H-pyrazole-3,5-dicarboxylate; CAU-10: Al(OH)(IPA), where IPA is isophthalate; MOF-801: Zr.sub.6O.sub.4(OH).sub.4(fumarate).sub.6; MOF-841: Zr.sub.6O.sub.4(OH).sub.4(MTB).sub.6(HCOO).sub.4(H.sub.2O).sub.2; Aluminum Fumarate: Al(OH)(fumarate); MIL-160: Al(OH)(FDA), where FDA is 2,5-furandicarboxylate; MIL-53: Al(OH)(TPA), where TPA is terephthalate; or Aluminum Phosphate: AlPO4-LTA. In some variations, the MOFs have pore sizes in the range of about 0.5 nm to about 1 nm, or between about 0.7 nm to about 0.9 nm. In certain variations, the MOFs have a hydrophilic pore structure. In certain variations, the MOFs have a hydrophilic pore structure comprising acid and/or amine functional groups. In certain variations, the MOFs have one-dimensional channels that allow for reversible water adsorption. Any combinations of the MOFs described herein, or other MOFs, or sorbents capable of water adsorption/desorption may also be used. In some embodiments, the MOF can be mixed with a binder to improve its properties for adhesion to a substrate or support.

[0037] In other variations, other sorbents (5) having high water uptake abilities as well as the isotherm step described above may be used in the systems and methods described herein. Other suitable sorbents (5) may include, for example, certain molecular sieves (as one example, SAPO-34 a micropore zeolite, CAS No. 1318-02-1) and certain zeolites having the properties described above.

[0038] Rate of water desorption in the sorbent materials (5) (including the above-described MOFs) and saturated vapor pressure in air values increase exponentially with temperature. The specific desorption energy, on the other hand, decreases with temperature. These three factors all favor a design of the desorption process at elevated temperatures. However, higher desorption temperature incurs a higher sensible heat penalty from the sorbent material (5), water (7) inside the sorbent material (5), support structure, recirculating air (7), and water vapor. The condensation temperature needs to be below the dew point of the desorbed hot water vapor (14). More water (7) can be condensed in a single pass through the cold-side heat exchanger (23) with lower condensation temperature, but the heat-pump COP value becomes lower with increase in T.sub.h−T.sub.c and decrease in T.sub.c. Consequently, desorption and condensation temperatures for the water harvesting system (1) can be adjusted to achieve the lowest energy per liter of water produced with a given sorbent material (5).

[0039] Again, with primary reference to FIG. 2A, another example of the system (1) is depicted in which a rotating carousel (8a) continuously moves fully saturated MOF containing sorbent module(s) (4) into a desorption chamber (9) for desorption. Once a MOF sorbent module (4) moves into the desorption chamber (9), it is heated-up to release water (7) as hot water vapor (14). Simultaneously, the other MOF sorbent modules (4) can be exposed to air (6) blown across them to initiate adsorption. In particular embodiments, upon completed desorption, a motor (32) with positioning control can rotate the carousel (8a) to move the desorbed sorbent module or MOF sorbent module (4) out of the desorption chamber (9) and allowing a saturated MOF sorbent module (4) to enter the desorption chamber (9).

[0040] With reference to FIG. 2B, another example of the system (1) is depicted in which a multi-axis robotic arm (8b) (or other automated mechanism) handles switching of the MOF sorbent modules (4) between an adsorption rack (17) and the desorption chamber (9). As soon as the MOF sorbent module (4) is sufficiently desorbed in the desorption chamber (9), it can be removed by the robot arm (8b) and placed back into the adsorption rack (17). A new fully adsorbed MOF sorbent module (4) can be picked up and placed by the robotic arm (8b) into the desorption chamber (9). A computer and water harvesting algorithm (32) can be used to track desorption and adsorption status of each module.

[0041] Now, with primary reference to FIG. 3, a schematic diagram illustrates a thermal coupling between the “condenser” hot-side heat exchanger (21) and the MOF sorbent module (4) in a desorption chamber (9). The desorption chamber (9) is thermally isolated from the environment with insulated walls (33). A recirculation fan (10) blows air (6) across the hot-side heat exchanger (21) to raise the temperature when a sufficiently adsorbed MOF sorbent module(s) (4) is placed into the desorption chamber (9). This air (6) or air/water mixture (11) heated by being blown across the hot-side heat exchanger (21) can then be blown across the MOF sorbent module(s)(4) to raise the temperature of the MOF sorbent module (4) to release the adsorbed water (7). A portion of the hot water vapor (14) released from the MOF sorbent module (4) can then be circulated by the recirculation fan (10) back to the hot-side main heat exchanger (21) to continue raising the at least one MOF sorbent material (5) temperature to the desired operating desorption temperature. A portion of the hot water vapor (14) from the MOF sorbent module (4) can be directed to the condensation chamber (16) for condensation. Depending on water vapor conditions (RH and temperature values) at the exit of the MOF sorbent module (4), the re-circulating and desorption rates can be adjusted by varied operation of the variable-speed recirculation fan (10) to adjust the flow of the air/water mixture (11) using a pre-determined algorithm (31). The goals are to achieve a constant energy load of the heat exchangers and to maintain a high moisture content of the hot water vapor (14) for more efficient condensation yield. Thermal coupling between the hot-side heat exchanger (21) and the MOF sorbent module (4) can also be improved by physical contact of the heat exchanger and the MOF sorbent module (4).

[0042] It should be understood that while FIGS. 2A, 2B and 3 illustrate particular embodiments of MOF sorbent modules (4) in the system (1), other suitable sorbent modules (4) may be used in other variations of the systems (1) described herein.

[0043] Now, with primary reference to FIG. 4, which depicts an illustrative schematic for the hot water vapor (14) condensation and liquid water (7) collection. In such embodiment, the condensation chamber (16) can be enclosed in a thermally insulated wall (33) (or other manner of condensation chamber insulation). Hot water vapor (14) can flow from the desorption chamber (9) and passed through the “evaporator” cold-side heat exchanger (23) allowing the hot water vapor (14) to cool and water (7) to condense upon reaching the dew point. The exhaust carries cooler air/water mixture (11) back into the desorption chamber (9). A heat sink (24b) can be thermally coupled to the cold-side heat exchanger (23) to maintain the desired operating temperature for water condensation. Liquid water (7) can drip down from the fins of the cold-side heat exchanger (23) and can be collected in the water collection tank (25) below the condensation chamber (16). A desorption-condenser recirculation fan (13) can be used to control and recirculate hot-water vapor (14) and the exhaust cooler an air/water mixture (11) between the desorption chamber (9) and condensation chamber(s) (16).

[0044] Now, with primary reference to FIG. 5 which depicts components of an illustrative example of a particular embodiment of the system (1) where the temperature, humidity, and velocity of the circulating air values can be measured, as above described. Temperature of the hot-side heat exchanger (21) and cold-side heat exchanger (23) can also be measured. Based on these measured values, the computer (26) by execution of the water harvesting algorithm (32) can assess the energy loads for each heat exchanger (21, 22, 23). In some variations, the computer (26) in the system (1) may be programmed to adjust the air flow rates by changing the fan speed of the recirculating fans (10, 13) to maintain nearly constant energy loads for each heat exchanger (21, 22, or 23) included in the system (1) and to achieve the desired temperature for the desorption and condensation processes. Heat pump energy balance can be obtained between the power input of the compressor, {dot over (W)}, the energy load of the cold-side heat exchanger, {dot over (Q)}.sub.c, and the energy loads of the hot-side heat exchangers, which are denoted by {dot over (Q)}.sub.hm and {dot over (Q)}.sub.hs separately for the main and the secondary heat exchangers can be expressed as:

{dot over (W)}=({dot over (Q)}.sub.hm+{dot over (Q)}.sub.hs)−{dot over (Q)}.sub.c  (3)

See R. Sonntag and C. V. Wylen, Introduction to Thermodynamics Classical and Statistical, 2.SUP.nd .ed., John Wylie and Sons, 1982.

[0045] The compressor work input is constant based on the compressor design and the operating conditions. In some variations, to recycle the majority of the recovered condensation heat for desorption, the system is configured to set the following:

{dot over (Q)}.sub.hm={dot over (Q)}.sub.c  (4)

and

{dot over (Q)}.sub.hs={dot over (W)}  (5)

[0046] Thus, the energy load of the hot-side heat exchanger (21) equals to that of the cold-side heat exchanger (23). Some power input can be dissipated by the secondary hot-side heat exchanger (22) to the environment.

[0047] The hot-side heat exchanger (21) configuration may be modeled by taking into account energy “gain” due to incoming and outgoing airflow, which should be equal to the energy dissipated by the hot-side heat exchanger.

{dot over (Q)}.sub.hm={dot over (m)}.sub.bC.sub.pbT.sub.b−{dot over (m)}.sub.aC.sub.paT.sub.a  (6)

where {dot over (m)}.sub.b is the air/water vapor mixture mass flow rate, C.sub.pb the specific heat capacity, and T.sub.b the temperature at location b; {dot over (m)}.sub.a is the air/water vapor mixture mass flow rate, C.sub.pa the specific heat capacity, and T.sub.a the temperature at location a. T.sub.b should be approximately equal to T.sub.h, which is the operating temperature of the hot-side heat exchanger (21) with a targeted heat exchanger design. The mass flow rate can be estimated using the air density, air velocity and cross-sectional area of the heat exchanger. Initially, when the fully adsorbed sorbent module (4) (e.g. MOF sorbent module) is moved into the desorption chamber (9) for desorption, T.sub.a is low but quickly heats up during the desorption process. The system (1) increases the desorption recirculation fan speed (10) according to the equation (6) to maintain constant {dot over (Q)}.sub.hm.

[0048] The energy balance for the secondary hot-side heat exchanger (22) can be expressed as follows:

{dot over (Q)}.sub.hs={dot over (W)}=h.sub.sA.sub.s(T.sub.h−T.sub.f)  (7)

where h.sub.s is the heat transfer coefficient of the secondary hot-side heat exchanger (22) which is a function of heat transfer geometry and air flow, A, area of the fins of the heat exchanger, and T.sub.f the environment temperature. The system (1) adjusts the rate of the airflow across the secondary hot-side heat exchanger (22) to maintain a constant energy dissipation rate as the environment temperature changes.

[0049] Both the sensible heat and the latent heat portions of the energy load at the cold-side heat exchanger need to be considered for the condensation process.

[00002]$\begin{array}{cc}{\stackrel{.}{Q}}_c={\stackrel{.}{m}}_d{C}_{\mathrm{pd}}{T}_d-{\dot{m}}_e{C}_{\mathrm{pe}}{T}_e+H_{\mathrm{fg}}\left(\frac{{\dot{m}}_d}{{\rho }_d}{\varphi }_d-\frac{{\dot{m}}_e}{p_e}{\varphi }_e\right)& \left(8\right)\end{array}$

where {dot over (m)}.sub.d is the air/water vapor mixture mass flow rate, C.sub.pd the specific heat capacity, T.sub.d the temperature, ρ.sub.d the air density, and Φ.sub.d the absolute humidity at location d; {dot over (m)}.sub.e is the air/water vapor mixture mass flow rate, C.sub.pe the specific heat capacity, T.sub.e the temperature, ρ.sub.e the air density, and Φ.sub.e the absolute humidity at location e and H.sub.fg is the latent heat of water at the condensation temperature. T.sub.e should be approximately equal to the cold-side heat exchanger temperature with the targeted heat exchanger design.

[0050] In some variations, the system (1) adjusts the desorption-condenser recirculation fan (13) speed to maintain a constant energy load for the cold-side heat exchanger (23) as temperature and humidity values of the incoming and outcoming air/water vapor mixture changes.

[0051] Again, with general reference to FIGS. 1 through 9A and 9B, particular embodiments of the sorbent-based water harvesting system (1) can be configured for dehumidification-humidification of air (6) that employs a heat pump (2a) to effectively recover condensation energy and use it for desorption of hot water vapor (14) from the sorbent material (5). Particular embodiments afford a method of using any of the sorbent-based water harvesting systems (1) described herein to control humidity level from surrounding air (6).

[0052] Now, with primary reference to FIGS. 1, 2A and 2B, particular embodiments of the system (1) can include an adsorption unit (3) that can hold one or a plurality of sorbent modules (4) containing at least one sorbent material (5). As a first illustrative example, the adsorption unit (3) can comprise a rotating carousel (8a) as shown in FIG. 2A, and as a second illustrative example, the adsorption unit (3) can comprise an adsorption rack (17) in which a plurality of sorbent modules (4) can be stacked as shown in the example of FIG. 2B. In particular embodiments of the system (1), a transfer mechanism (8) can be used to move the one or each of the plurality of absorbent modules (4) from the adsorption unit (3) to the desorption chamber (9). As shown in the example of FIG. 2A, the carousel (8a) can include a plurality of absorption modules (4) disposed radially outward of and spaced circumferentially around a central rotation axis. The carousel (8a) can rotate to move each of the plurality of adsorption modules (4) into the desorption chamber (9). As shown in the example of FIG. 2B, a robotic arm (8b) can operate to move each of the plurality of absorption modules (4) from the adsorption rack (17) into the desorption chamber (9). Air (6) can be pushed across one or more sorbent modules (4), leading to adsorption of water (7) from the surrounding air (6) by the sorbent material (5) contained in the one or the plurality of sorbent modules (4). Once a sorbent module (4) reaches a target level and/or rate of adsorption, the transfer mechanism (8) can move the sorbent module (4) with adsorbed water (7) from the adsorption unit (3) to a desorption chamber (9) of the system (1). In some embodiments, the desorption chamber (9) can include a recirculation fan (10) that blows an air/water mixture (11) across the hot side (12) of the heat pump (2) through the sorbent module (4) to facilitate desorption of water (7). Once a target water concentration is achieved in the desorption chamber (9), the system (1) can operate a desorption-condenser recirculation fan (13) present in the desorption chamber to transfer hot moisture from the desorption chamber (9) to the cold side (15) of the heat pump (2a) encompassed in, or positioned in closer proximity to, a condensation chamber (16).

[0053] Now, with primary reference to FIGS. 1, 6-9A and 9B, particular embodiments the system (1) configured for dehumidification-humidification of air (6) can further comprise one or more of: a water collection tank (25) connected to the condensation chamber (16), configured to collect water (7) condensed in the condensation chamber (16); a water pump (34) connected to the water collection tank (25), configured to receive water (7) from the water collection tank (25); a drain (35) connected to the water collection tank (25); a sprayer (36) connected to the water pump (34) and positioned in proximity to an indoor outlet (37); a bypass unit (38) positioned in proximity to the adsorption unit (3), configured to transfer air (6) from outdoor inlet (39) or an indoor inlet (40) or combination thereof; an adsorption fan (41) positioned in proximity to the adsorption unit (3) and the bypass unit (38) to transfer air (6) from the outdoor inlet (39) or the indoor inlet (40), or combination thereof, into the adsorption unit (3) and the bypass unit (38); an indoor/outdoor inlet damper (42) configured to control the transfer of air (6) into the adsorption unit (3) and the bypass unit (38) from the outdoor inlet (39) or the indoor inlet (40), or combination thereof; an adsorption damper (43) configured to direct a portion of the flow of air (6) into the adsorption unit (3) and a portion of the flow of air (6) into the bypass unit (38); and an indoor/outdoor outlet damper (44) configured to control the flow of air (6) out of the adsorption unit (3) and the bypass unit (38) into an outdoor outlet (45) or the indoor outlet (37) or combination thereof.

[0054] Particular embodiments of the system (1) can be configured to operate in and switch among a plurality of modes (i)-(iv) including a first mode (i) to dehumidify air (6) coming from outdoors (46) to indoors (47), a second mode (ii) to humidify air (6) coming from outdoors (46) to indoors (47), a third mode (iii) to dehumidify recirculated air (6) indoors (47), and a fourth mode (iv) to humidify recirculated air (6) indoors (47).

[0055] In particular embodiments of the system (1), the average desorption temperature or the average condensation temperature, whether independent of each other or in relation to each other, can be configured to achieve the lowest energy per liter of water produced with the sorbent material (5), and in certain embodiments, maintaining the desorption temperature high enough to sustain a target desorption rate. Once the sorbent module (4) is depleted of water (7) or depleted to a target depletion level of water (7), the transfer mechanism (8) can remove the sorbent module (4) from the desorption chamber (9) and return the sorbent module (4) back into the adsorption unit (3).

[0056] Now, with primary reference to FIGS. 6 through 9A and 9B, an illustrative example of the system (1) configured for humidification-dehumidification can include an adsorption unit (3) (as examples an adsorption rack (17) or carousel (8a) including one or more sorbent modules (4)) (as an example, one or more MOF modules), an transfer mechanism (8) (such as, a carousel (8a) or a robotic arm (8b)), a discrete desorption/condensation unit (2) that includes a heat-pump (2a). In some embodiments, the heat-pump (2) includes a heat exchanger (18), which has a hot side (12) (a “condenser”) and a cold side (15) (an “evaporator”). In some variations, the heat-pump (2a) can include a compressor (19), an expansion valve (20), a main “condenser” or the hot-side heat exchanger (21), a secondary hot-side heat exchanger (22), an “evaporator” or the cold-side heat exchanger (23), and other control components which can be designed to operate at elevated temperatures. In particular embodiments, the system (1) can include a spraying unit (48) including a water collection tank (25), a drain (35), a water pump (34), a water sprayer (36) connected to the water pump (34). In addition, an airflow system (49) can comprise one or more of: an indoor/outdoor inlet damper (42), an indoor/outdoor outlet damper (44) and an adsorption damper (43). The system (1) can include an adsorption fan (41) and a bypass unit (38). The adsorption unit (3) and the set of dampers (42)(43)(44) can be positioned in a way to either adsorb water from outdoors (46) to work in modes (i) or (ii) or indoors (47) to work in modes (iii) and (iv). The set of dampers (42)(43)(44) control the direction of the flow of air (6). The transfer mechanism (8) can transfer sorbent modules (4) in and out of the separate desorption/condensation unit (2). Water vapor (14) undergoes desorption and condensation processes in the desorption/condensation unit (2) and then collected in the water collection tank (25). When the system (1) enters humidification mode, the collected water (7) can be delivered by the water spraying unit (48). When the system (1) enters dehumidification mode, the collected water (7) can be transported into the drain (35).

Mode (i): Outdoor Air Dehumidifier

[0057] Now, with primary reference to FIG. 6, depicted is an illustrative example of the system (1) configured for dehumidification of air coming from outdoors (46) to indoors (47). The indoor/outdoor inlet damper (42) opens the outdoor inlet (39) and closes the indoor inlet (40). Air (6) from outdoors (46) can pass through the outdoor inlet (39) and then in part passes through the adsorption unit (3) and in part pass through bypass unit (38). The amount of air (6) from outdoors (46) that passes through the adsorption unit (3) to be dehumidified and the amount of air (6) from outdoors (46) that pass through the bypass unit (38) can be controlled by operation of the adsorption damper (43), which can be positioned in a range between an open or closed condition of the adsorption unit (3) and an open or closed condition of the bypass unit (38). The indoor/outdoor outlet damper (44) closes the outdoor outlet (45) and opens the indoor outlet (37). The dehumidified air (6) can be directed indoors (47) through the indoor outlet (37). The water spraying unit (48) can remain in the off condition in mode (i). The sorption modules (4) saturated with water (7) can be placed into the desorption/condensation unit (2), the desorbed water (7) can be condensed in the desorption chamber (9) and water (7) can be collected in the water collection tank (25). Collected water can be kept in the water collection tank (25) or removed through the drain (35).

Mode (ii): Outdoor Air Humidifier

[0058] Now, with primary reference to FIG. 7, depicted is an illustrative example of the system (1) configured to humidify air (6) coming from outdoors (46) to indoors (47). The indoor/outdoor inlet damper (42) opens the outdoor inlet (39) and closes the indoor inlet (40). The adsorption damper (43) closes the bypass unit (38). Air (6) from outdoors (46) passes through the outdoor inlet (39) and only passes through the adsorption unit (3). The indoor/outdoor outlet damper (44) can be positioned to partially open the outdoor outlet (45) and partially open the indoor outlet (37). The amount of dehumidified air (6) directed outdoors (46) through the outdoor outlet (44) and the amount of dehumidified air (6) directed indoors (47) through indoor outlet (37) can be controlled by the position of indoor/outdoor outlet damper (44). The water spraying unit (48) can be placed in the on condition. The sorption modules (4) saturated with water (7) can be placed into the desorption/condensation unit (2), the desorbed water (7) can be condensed in the desorption chamber (9) and water (7) can be collected in the water collection tank (25). Collected water (7) can be pumped to the water sprayer (36) using the water pump (34).

Mode (iii): Indoor Air Dehumidifier

[0059] Now, with primary reference to FIG. 8, depicted is an illustrative example of the system (1) configured to dehumidify recirculated indoor (47) air (6). The indoor/outdoor inlet damper (42) opens the indoor inlet (40) and closes the outdoor inlet (46). Air (6) from indoors (47) can pass through indoor inlet (40) and then in part pass through the adsorption unit (3) and in part through the bypass unit (38). The amount of air (6) from indoors (47) that passes through the adsorption unit (3) and the amount of air (6) that passes through the bypass unit (38) can be controlled by the position of the adsorption damper (43), which can be positioned from a closed condition of the bypass unit (38) to a closed condition of the adsorption unit (3) or positioned to a partially open condition of both the bypass unit (38) and the adsorption unit (3). The indoor/outdoor outlet damper (44) closes the outdoor outlet (45) and opens the indoor outlet (37). The dehumidified air (6) can then be directed indoors (47) through the indoor outlet (37). The spraying system can remain in the off condition. The sorption modules (4) saturated with water (7) are placed into the desorption/condensation unit (2), the desorbed water (7) can be condensed in the desorption chamber (9) and collected in the water collection tank (25). Collected water (7) can be kept in the water collection tank (25) or removed from the water collection tank (25) through the drain (35).

Mode (iv): Indoor Air Humidifier

[0060] Now, with primary reference to FIGS. 9A and 9B, depicted is an illustrative example of the system (1) configured for humidification of recirculated indoor (47) air (6). Initially, in a first configuration of the system (1) (as depicted in the example of FIG. 9A), the indoor/outdoor inlet damper (42) opens the outdoor inlet (39) and closes the indoor inlet (40). The adsorption damper (43) closes the bypass unit (38). Outdoor (46) air (6) can pass though outdoor inlet (39) and then passes only through the adsorption unit (3). The indoor/outdoor outlet damper (44) closes the indoor outlet (37) and opens the outdoor outlet (44). The dehumidified air (6) passes outdoors (46) through the outdoor outlet (45). The water spraying unit (48) can remain in the off condition. The sorption modules (4) saturated with water (7) can be transferred to the desorption/condensation unit (2), the desorbed water (7) can be condensed in the desorption chamber (9) and collected in the water collection tank (25). Collected water (7) can be kept in the water collection tank (25).

[0061] Subsequently, in a second configuration of the system (1) (as depicted in the example of FIG. 9B), the indoor/outdoor inlet damper (42) closes the outdoor inlet (39) and opens the indoor inlet (40). The adsorption damper (43) closes the adsorption unit (3). Air (6) from indoors (47) can pass through the indoor inlet (40) and then only through the bypass unit (38). The indoor/outdoor outlet damper (44) closes the outdoor outlet (44) and opens the indoor outlet (37). The air (6) from the bypass unit (38) can be directed indoors (47) through indoor outlet (37). The collected water (7) in the water collection tank (25) can by operation of the water pump (34) be conducted to the sprayer (36) sprayed from the sprayer (36) into the air passing through the indoor outlet (37) to humidify the air (6) passing indoors (47).

EXAMPLES

[0062] The presently disclosed subject matter will be better understood by reference to the following Examples, which are provided as exemplary of the invention, and not by way of limitation.

Example 1

Optimizing Desorption and Condensation Temperatures

[0063] The example describes optimization of desorption and condensation temperatures used in a water harvesting system. The model used an iterative procedure. First, the model set the initial desorption and condensation temperatures of the system. Based on the isotherm step of the sorbent, the absolute humidity in the desorption chamber was known at the given desorption temperature. The condensation yield can be calculated for the given condensation temperature, if the relative humidity and temperature of the water vapor in the desorption chamber is known. The heat pump efficiency was computed with equation (2) assuming f=0.6 and in turn the work input is calculated using equation (1). In addition to the desorption and condensation energy, the model further considered the sensible heat value required to heat up the sorbent, water inside sorbent, air, and vapor. The model also took into account the temperature of the recycled vapor and the specified total water harvesting yield of the system. Thus, the system energy consumption per liter of harvested water was approximated as a function of the desorption and condensation temperatures with a given MOF type. The optimum conditions were obtained by varying the two variables (desorption and condensation temperatures). See Table 1 below.

TABLE-US-00001 TABLE 1 Isotherm step Desorption Condensation @25° C. Temperature Temperature MOFType (RH %) (OC) (OC) Arid 20 136 90 Moderate 40 117 91 Humid 60 107 92

[0064] Table 1 shows the optimal desorption and condensation temperatures for three types of MOFs. The water harvester which contains an arid-type MOF with an isotherm step of 20% of relative humidity (RH) at 25° C. optimally operates at the desorption temperature of 136° C. and the condensation temperature of 90° C. “Moderate” MOF with an isotherm step of RH 40% requires desorption and condensation temperatures of 117° C. and 91° C., respectively; while a “humid” MOF with an isotherm step of RH 60% requires desorption and condensation temperatures at 107° C. and 92° C., respectively.

[0065] Table 1 indicates that utilization of a high-temperature heat pump is required to achieve the lowest energy consumption per liter of harvester water given that the high-temperature heat pump operates at 90-160° C. for the hot-side heat exchanger and 40-95° C. for the cold-side heat exchanger.

[0066] As can be easily understood from the foregoing, the basic concepts of the present invention may be embodied in a variety of ways. The invention involves numerous and varied embodiments of a water harvesting system and methods for making and using the varied embodiments of the water harvesting system including the best mode.

[0067] As such, the particular embodiments or elements of the invention disclosed by the description or shown in the figures or tables accompanying this application are not intended to be limiting, but rather illustrative of the numerous and varied embodiments generically encompassed by the invention or equivalents encompassed with respect to any particular element thereof. In addition, the specific description of a single embodiment or element of the invention may not explicitly describe all embodiments or elements possible; many alternatives are implicitly disclosed by the description and figures.

[0068] It should be understood that each element of an apparatus or each step of a method may be described by an apparatus term or method term. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled. As but one example, it should be understood that all steps of a method may be disclosed as an action, a means for taking that action, or as an element which causes that action. Similarly, each element of an apparatus may be disclosed as the physical element or the action which that physical element facilitates. As but one example, the disclosure of a “harvester” should be understood to encompass disclosure of the act of “harvesting”—whether explicitly discussed or not—and, conversely, were there effectively disclosure of the act of “harvesting”, such a disclosure should be understood to encompass disclosure of a “harvester” and even a “means for harvesting.” Such alternative terms for each element or step are to be understood to be explicitly included in the description.

[0069] In addition, as to each term used it should be understood that unless its utilization in this application is inconsistent with such interpretation, common dictionary definitions should be understood to be included in the description for each term as contained in Merriam-Webster's Collegiate Dictionary, each definition hereby incorporated by reference.

[0070] All numeric values herein are assumed to be modified by the term “about”, whether or not explicitly indicated. For the purposes of the present invention, ranges may be expressed as from “about” one particular value to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value to the other particular value. The recitation of numerical ranges by endpoints includes all the numeric values subsumed within that range. A numerical range of one to five includes for example the numeric values 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, and so forth. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. When a value is expressed as an approximation by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” generally refers to a range of numeric values that one of skill in the art would consider equivalent to the recited numeric value or having the same function or result. Similarly, the antecedent “substantially” means largely, but not wholly, the same form, manner or degree and the particular element will have a range of configurations as a person of ordinary skill in the art would consider as having the same function or result. When a particular element is expressed as an approximation by use of the antecedent “substantially,” it will be understood that the particular element forms another embodiment.

[0071] Moreover, for the purposes of the present invention, the term “a” or “an” entity refers to one or more of that entity unless otherwise limited. As such, the terms “a” or “an”, “one or more” and “at least one” can be used interchangeably herein.

[0072] Thus, the applicant(s) should be understood to claim at least: i) each of the water harvesters herein disclosed and described, ii) the related methods disclosed and described, iii) similar, equivalent, and even implicit variations of each of these devices and methods, iv) those alternative embodiments which accomplish each of the functions shown, disclosed, or described, v) those alternative designs and methods which accomplish each of the functions shown as are implicit to accomplish that which is disclosed and described, vi) each feature, component, and step shown as separate and independent inventions, vii) the applications enhanced by the various systems or components disclosed, viii) the resulting products produced by such systems or components, ix) methods and apparatuses substantially as described hereinbefore and with reference to any of the accompanying examples, x) the various combinations and permutations of each of the previous elements disclosed.

[0073] The background section of this patent application provides a statement of the field of endeavor to which the invention pertains. This section may also incorporate or contain paraphrasing of certain United States patents, patent applications, publications, or subject matter of the claimed invention useful in relating information, problems, or concerns about the state of technology to which the invention is drawn toward. It is not intended that any United States patent, patent application, publication, statement or other information cited or incorporated herein be interpreted, construed or deemed to be admitted as prior art with respect to the invention.

[0074] The claims set forth in this specification, if any, are hereby incorporated by reference as part of this description of the invention, and the applicant expressly reserves the right to use all of or a portion of such incorporated content of such claims as additional description to support any of or all of the claims or any element or component thereof, and the applicant further expressly reserves the right to move any portion of or all of the incorporated content of such claims or any element or component thereof from the description into the claims or vice-versa as necessary to define the matter for which protection is sought by this application or by any subsequent application or continuation, division, or continuation-in-part application thereof, or to obtain any benefit of, reduction in fees pursuant to, or to comply with the patent laws, rules, or regulations of any country or treaty, and such content incorporated by reference shall survive during the entire pendency of this application including any subsequent continuation, division, or continuation-in-part application thereof or any reissue or extension thereon.

[0075] Additionally, the claims set forth in this specification, if any, are further intended to describe the metes and bounds of a limited number of the preferred embodiments of the invention and are not to be construed as the broadest embodiment of the invention or a complete listing of embodiments of the invention that may be claimed. The applicant does not waive any right to develop further claims based upon the description set forth above as a part of any continuation, division, or continuation-in-part, or similar application.