Atmospheric water harvester with climate-adjustable adsorbant properties

Abstract

This paper presents an atmospheric water sampling system with optimal adsorption limits, customized based on energy cost and water availability considerations. The system comprises multiple adsorbent modules, each containing a metal-organic framework with various adsorption limits. This design allows for real-time adjustments to achieve optimal sampling conditions under varying atmospheric conditions, including daily and seasonal humidity changes.

Description

Technical Field

[0001] This disclosure is generally about water collection, and more specifically about systems and methods for collecting water from the surrounding air under varying atmospheric conditions. Prior Technology

[0002] Drinking water is scarce, especially in the desert regions of North Africa and the Middle East. However, it is abundant in the atmosphere, even in arid regions. In recent years, porous materials have been designed to harvest atmospheric water. See Atmospheric Water Harvesting: A Review of Material and Structural Designs, X. Zhou, H. Lu, F. Zhao and G. Yu, ACS Materials Lett. 2020, 2, 7, 671–684. In particular, a class of metallic frameworks (MOFs) with high water affinity has been developed, exhibiting excellent atmospheric water yield. See H. Furukawa, F. Gándara, YB Zhang, J. Jiang, WL Queen, MR Hudson and OM Yaghi, Water Adsorption in Porous Metal–Organic Frameworks and Related Materials, J. Am. Chem. Soc. 2014,136,11,4369–4381; MJ Kalmutzki CS Diercks and OM Yaghi, Metal–Organic Frameworks for Water Harvesting from Air, Advanced Materials Volume 30, Issue 37, 2018, 1704304; and N. Hanikel et al., Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water Harvester; ACS Cent. Sci. 2019, 5, 10, 1699-1706, August 27, 2019. This discovery has spurred the development of devices that can be deployed in homes or in desert areas without drinking water. See WO 2020 / 154427.

[0003] Depicted in the figure [1] shows a schematic diagram of the water adsorption properties of various porous materials. The amount of water adsorbed (in mass%) is usually expressed as a function of the relative humidity (in percentage) of the surrounding air, known as the adsorption isotherm. First and for all practical purposes, these curves are independent of temperature. MOF materials exhibit a stepped characteristic, which allows them to capture and release water within a very narrow humidity range (Figure 1). [2]). This contrasts with more conventional materials such as silicone, which exhibits more gradual isotherms, or zeolite, which desorbs water only at extremely low humidity levels (Figure 1). [1]). Another advantage of MOF materials is that the relative humidity RH0 at which adsorption occurs (adsorption threshold) can be adjusted by changing the molecular properties of the material itself. In fact, the continuous range of RH0 can be achieved by mixing various organic or inorganic components into multivariate MOFs with different water affinities. See WO2020112899; Janiak, C. et al., Solid-Solution Mixed-Linker Synthesis of Isoreticular Al-Based MOFs for an Easy Hydrophilicity Tuning in Water-Sorption Heat TransformationsChem. Mater.2019,31,11,4051–4062; and Fang, Y. et al., One-Pot Synthesis of Two-Linker Mixed Al-Based Metal–Organic Frameworks for Modulated Water Vapor AdsorptionCryst. Growth Des.2020,20,10,6565–6572. Finally, a large adsorption capacity (in mass%) is also a requirement for practical water collectors.

[0004] This technology requires an atmospheric water collector designed to achieve optimal collection conditions under varying atmospheric conditions. Summary of the Invention

[0005] In some embodiments, the atmospheric water harvesting system includes: a plurality of modules configured as at least one adsorption stack; a desorption chamber configured to receive modules saturated or nearly saturated with water from the adsorption stack, causing water to desorb from modules positioned therein in the form of water vapor; a condensation chamber positioned adjacent to or near the desorption chamber, configured to condense at least a portion of the water vapor from the desorption chamber into liquid water; and a robotic arm configured to (i) select and grasp modules saturated or nearly saturated with water in the adsorption stack, and (ii) transfer modules into the desorption chamber. In some embodiments, each module independently includes at least one metal-organic framework positioned on or incorporated into a support. In some variations, when a module is positioned in the adsorption stack, at least one metal-organic framework adsorbs water from the surrounding air.

[0006] In some cases, a method for collecting water from the atmosphere using any of the atmospheric water collection systems described herein is also provided. Simple Explanation of the Diagram

[0007] This application can be best understood by referring to the following description in conjunction with the accompanying drawings included in this specification.

[0008] picture [1] A graph showing the adsorption isotherms of MOFs compared with those of conventional adsorbents such as silica and zeolite.

[0009] picture [2] A diagram showing adsorption and desorption under atmospheric water sampling using MOFs.

[0010] picture [3] A diagram showing the optimization of water extraction (in terms of productivity, compared to energy costs).

[0011] picture [4] Depict a decision tree for selecting the optimal type of MOF module to move to the desorption or condensation chamber.

[0012] picture [5A] Describes an exemplary atmospheric water harvesting system having replaceable MOF modules in a circular configuration.

[0013] picture [5B] Describes an exemplary atmospheric water harvesting system having replaceable MOF modules configured in a stacked manner. Implementation

[0014] Cross-reference to related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 139,211, filed January 19, 2021, which is incorporated herein by reference in its entirety.

[0015] The following embodiments describe exemplary systems, methods, parameters, and the like. However, it should be understood that this description is not intended to be a limitation on the scope of this disclosure but is provided to illustrate exemplary embodiments.

[0016] In some embodiments, atmospheric water collectors are provided, based on considerations of energy cost and water availability, including MOF adsorbent systems with optimal adsorption limits. Methods for collecting water from ambient air using the atmospheric water collectors described herein are also provided. In some embodiments, the atmospheric water collector is designed to include several adsorbent assemblies, each made of MOFs with various adsorption limits. Such collectors allow for on-the-fly adjustment of the MOF material to achieve optimal collection conditions under varying atmospheric conditions, whether daily or seasonal humidity changes. In some embodiments, the atmospheric water collector is structurally designed to completely separate the adsorption process from the desorption and condensation processes. This allows for multiple design configurations.

[0017] In one embodiment, an atmospheric water sampling system is provided, comprising a plurality of MOF modules; a desorption chamber; a condensation chamber; and a robotic arm. Each MOF module contains at least one MOF. In some embodiments, the MOF modules are configured as an adsorption stack. The adsorption stack may comprise MOF modules of the same MOF material (MOF "A") or MOF modules of MOF materials with different adsorption limits RH0 (MOF "A", "B", "C", etc.).

[0018] In some variants, the MOF contains organic ligands having acid and / or amine functional groups. In some variants, these organic ligands have carboxylic acid groups. In other variants, these organic ligands have acid and / or amine functional groups. In some variants, these organic ligands have carboxylic acid groups. Any suitable MOF capable of adsorbing and desorbing water can be used in the systems provided herein. Suitable MOFs may include those described, for example, in Kalmutzki et al., Adv. Mat., 30(37), 1704304 (2018); Furukawa et al., J. Am. Chem. Soc. 2014, 136, 4369-4381; Y. Tu et al., Joule, Vol. 2, No. 8(15), 1452-1475 (2018). In some variants, 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:Zr6O4(OH)4(fumarate)6; MOF-841:Zr6O4(OH)4(MTB)6(HCOO)4(H2O)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 variants, these MOFs have a pore size between about 0.5 nm and about 1 nm, or between about 0.7 nm and about 0.9 nm. In some variations, these MOFs have a hydrophilic porous structure. In some variations, these MOFs have a hydrophilic porous structure comprising acid and / or amine functional groups. In some variations, these MOFs have 1D channels that allow reversible water adsorption. Any combination of the MOFs described herein may also be used. In some embodiments, the MOF is mixed with a binder to improve its properties for adhesion to a substrate or support.

[0019] Air is blown across MOF modules, which are structurally designed to maximize their surface-to-volume ratio for rapid humidity exchange with the air. For example, in some variations, these MOF modules comprise a uniform MOF layer coated on a parallel plate. Water is adsorbed when the ambient relative humidity RHamb exceeds the adsorption threshold RH0 (see figure). [2]), the adsorption rate Rads can be expressed as: Where S(T) is the saturated vapor pressure of water at temperature T, and Tamb is the ambient air temperature. The adsorption rate directly affects water productivity (e.g., in liters per day, see figure). [3]).

[0020] A robotic arm (automated system) is structurally designed to select and pick up the optimal MOF module based on weather conditions. The robotic arm selects and grasps MOF modules from an adsorption stack that is saturated (or nearly saturated) with water, and transfers these MOF modules to a desorption chamber. After desorption, the robotic arm replaces the MOF modules, grasps the desorbed MOF modules from the desorption chamber, and places them back into the adsorption stack to achieve saturation.

[0021] In some variations, the robotic arm includes robotic effectors, vacuum effectors, mechanical effectors, or electromechanical effectors. In some variations, the robotic end effector may include a flexible structure maneuverable between different orientations. For example, in one variation, such a structure may include a silicon body or other flexible material. In some variations, the vacuum end effector may use suction to grasp objects. In other variations, the mechanical or electromechanical end effector may include clamps, grippers, graspers, or other rigid components actuated relative to each other for grasping objects.

[0022] To remove water from MOF modules that are saturated or nearly saturated with water, a robotic arm transfers the selected MOF module to a desorption chamber. In the desorption chamber, the humidity within the MOF module needs to be kept below RH0 (Figure 1). [2] In some variations, this can be achieved by increasing the air temperature, which increases the water saturated vapor pressure S(T), thus reducing the relative humidity. The temperature at which water begins to desorb, Tdes, can be calculated using the following equation:

[0023] Equation (2) indicates that absolute humidity (or water vapor concentration) is conserved during heating from Tamb to Tdes. In addition to the adsorption energy Eads required for water desorption from the MOF, the energy cost Es is also related to the increase in temperature (reasonable energy). Es is proportional to the desorption temperature, and an example of the change in Es relative to RH0 is schematically shown in the figure. [3] in.

[0024] As the temperature rises, a small airflow allows moisture to be desorbed and transferred to a condensation chamber housing at least one condenser. Once the humid air reaches the condenser, the liquid water condenses and is collected. In some variations, the humid air encounters a series of cold plates configured to maximize surface area, allowing the liquid water to condense.

[0025] picture [4] This describes the process by which the control system selects the optimal MOF module for the robotic arm to pick up. The system tracks the adsorption process to ensure that the modules have reached a sufficient adsorption state before being selected for desorption or condensation. Based on weather conditions, as shown in the figure... [4] In the decision tree (the algorithm defines (RH0)ideal, and the x% value is user-defined), the system will further select the best type of MOF module to move to the desorption or condensation chamber. For example, in a high relative humidity environment and when water demand is not too severe, a MOF with high RH0 can be selected to save energy costs. Conversely, when the ambient relative humidity is low, a low RH0 MOF module can be selected.

[0026] Refer to [5A] [and] [5B] Depicts an exemplary atmospheric water harvesting system. These figures show a system in which the adsorption process is completely separated from the desorption and condensation processes. [5A] Depicting MOF module stacking

[1020] via desorption chamber

[2020] condensation chamber

[2030] and water collection tank

[2040] and central automated materials processor

[3020] (In this example, a robotic arm) A radially arranged circular configuration. Adsorption stacking, as depicted in this exemplary embodiment of the system.

[1020] This includes MOF modules containing MOF materials with different adsorption threshold values ​​RH0. As depicted in the accompanying drawings, the MOF module...

[1022] For adsorption module, and module

[1024] and

[1026] Depicted in idle mode. These MOF modules are located in a pre-configured adsorption stack. In

[1020] , the airflow

[4020] By airflow management system

[4022] (The adsorption fan in this example) is controlled to optimize the adsorption process. Once the system selects the desorption MOF module... [1022b], Robotic Arm

[3020] Pick it up and place it in the desorption chamber. In

[2020] , thermal desorption of water is used in the desorption chamber. Desorption chamber

[2020] Including gates

[2022] It opens to receive via robotic arm

[3020] Desorption MOF module transferred from adsorption stack [1022b] and shut down after the MOF module undergoes desorption. The resulting steam is then directed to the condensation chamber.

[2030] Liquid water is generated in the condensation chamber and collected in the water tank.

[2040] In the middle. Once desorption is complete, the robotic arm will transfer this MOF module from the desorption chamber back to its original position in the adsorption stack. Then, the robotic arm will pick up the next MOF module and place it into the desorption chamber.

[2020] Desorption is performed, and then the process continues. Figure [5A] Displays a circular configuration, but multiple geometries can be used depending on space and coverage conditions. Figure [5B] For example, similar concepts are displayed, but in a stacked configuration.

[0027] Refer to the reference again [3], The RH0 value has a direct impact on both adsorption and desorption efficiencies. During adsorption, the water capture rate is proportional to (RHamb-RH0), as shown by equation (1) above. Therefore, for a given location / climate, a lower adsorption threshold improves adsorption kinetics and water productivity. However, during desorption, these MOF modules (which may include, for example, MOF materials and supports) need to be heated to reduce the relative humidity back to RH0 (Figure 1). [2]), and the low adsorption threshold here will require more thermal energy.

[0028] picture [3] The diagram illustrates the choices made when designing a MOF-based water collector. In arid climates, where the relative humidity (RHamb) of the ambient air is low, MOF materials need to have a low adsorption threshold (RH0) to capture water. However, when the relative humidity is high, users can choose between lower energy costs at the expense of water productivity (high RH0) or higher water productivity at the expense of energy costs (low RH0). For example, when water reserves are abundant, a lower energy cost option will be chosen, but when water demand is high, a MOF with a lower RH0 will be preferred. An example of this type of scenario is the daily humidity variation in arid regions, where lower nighttime temperatures lead to higher relative humidity. In addition, the annual humidity variation between seasons in a given region can also benefit from adjustments to the MOF adsorption threshold.

[0029] 1020: MOF Module Stacking 1022: MOF Module 1022b: Desorption MOF Module 1024: Module 1026: Module 2020: Desorption Chamber 2022: Gate 2030: Condensation Chamber 2040: Water Collection Tank 3020: Central Automated Materials Processor 4020: Airflow 4022: Airflow Management System

Claims

1. An atmospheric water harvesting system, comprising: A plurality of modules, each comprising at least one metal-organic framework (MOF) having an adsorption threshold humidity, wherein the at least one MOF adsorbs water from the air when the humidity is above the adsorption threshold humidity and desorbs water from the air when the humidity is below the adsorption threshold humidity, wherein the adsorption threshold humidity of the plurality of modules is different from that of each other; a controller configured to select one or more modules to adsorb water based on a comparison of the relative humidity of the air with the adsorption threshold humidity of the at least one MOF; a desorption chamber fluidly connected to the one or more modules, the desorption chamber being configured to reduce the relative humidity of the air within the one or more modules to below the adsorption threshold humidity to desorb water from the at least one MOF; and a condensation chamber fluidly connected to the desorption chamber, the condensation chamber being configured to condense the water desorbed from the at least one MOF.

2. The system of claim 1, wherein the controller is further structurally designed to select one or more modules based on the adsorption rate of the at least one metal-organic framework.

3. The system of claim 2, wherein the adsorption rate Rads is defined as: Rads = S(Tamb) × (RHamb − RH0) where S(Tamb) is the saturated vapor pressure of water in the air at temperature T; (RHamb) is the relative humidity of the air; and RH0 is the adsorption threshold humidity of the at least one metal-organic framework.

4. The system of claim 1, wherein the controller is further structurally designed to select one or more modules based on the energy cost of desorbing water from the at least one metal-organic framework.

5. The system of claim 4, wherein the controller is further structurally designed to select one or more modules based on the level of water storage.

6. The system of claim 1, wherein the controller is structurally designed to select the one or more modules based on one or more of the following: the relative humidity of the air; the adsorption threshold humidity of the at least one metal-organic framework; the adsorption rate of the at least one metal-organic framework; the energy cost of desorbing water from the at least one metal-organic framework; and the water storage capacity.

7. The system of claim 1, wherein the desorption chamber increases the water vapor saturation pressure of the air to reduce the relative humidity of the air to below the adsorption threshold humidity, so as to desorb water from the at least one metal-organic framework.

8. The system of claim 7, wherein the desorption temperature Tdes is the temperature at which water begins to desorb from the at least one metal-organic framework, and is calculated by the following formula: S(Tdes)×RH0=S(Tamb)×RHamb where, S(Tdes) is the saturated vapor pressure of water at desorption temperature T; Tamb is the temperature of the air; RHamb is the relative humidity of the air; and RH0 is the adsorption threshold humidity.

9. An atmospheric water harvesting system, comprising: A plurality of modules, each comprising at least one metal-organic framework (MOF), having an adsorption threshold humidity. Above this threshold humidity, the MOF adsorbs water from the air; below this threshold humidity, the MOF desorbs water from the air. The adsorption threshold humidityes of the plurality of modules are different from each other. A controller is structurally designed to select one or more modules to adsorb water from the air. The controller is structurally designed to select the following for adsorbing water: the relative humidity of the air; the adsorption threshold humidity of the at least one MOF; the adsorption rate of the at least one MOF; and the energy cost of desorbing water from the at least one MOF. Water storage capacity; And a desorption chamber, which can be operated to reduce the relative humidity of the air to below the adsorption threshold humidity, so as to desorb water from the at least one metal-organic framework.

10. The system of claim 9, further comprising a condensation chamber fluidly connected to the desorption chamber, the desorption chamber being operable to condense the water desorbed from the at least one metal-organic framework.

11. The system of claim 9, wherein the desorption chamber increases the water vapor saturation pressure of the air to reduce the relative humidity of the air to below the adsorption threshold humidity, so as to desorb water from the at least one metal-organic framework.

12. The system of claim 9, further comprising a heat exchanger operable to increase the temperature of the air to reduce the relative humidity of the air to below the adsorption threshold humidity, so as to desorb water from the at least one metal-organic framework.

13. The system of claim 10 further includes a cold exchanger operable to reduce the temperature of the air below the dew point temperature of the air to condense the water from the air.

14. The system of claim 9, further comprising one or more fans to allow air to pass through the one or more modules contained in the metal organic frame.

15. The system of claim 13, wherein the one or more fans circulate the air between the desorption chamber and the condensation chamber.

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