Water vapor capturing heat exchanger using alginate-bentonite bio-composite hydrogel and method for manufacturing the same

Abstract

A high performance adsorption heat exchanger ADS-HX (1) is described, comprising a hygroscopic composite biopolymer (2), a heat exchange medium (4) in contact with the hygroscopic composite biopolymer (2) and a hollow duct in contact with the heat exchange medium (4), through which a cooling fluid (6) or a heating fluid (8) is alternately passed, so that the adsorption heat exchanger (1) can be used in conditions of high ambient temperature and low relative humidity typical of arid climates. A method for manufacturing the high performance adsorption heat exchanger ADS-HX (1) described above is also described. A preferred and advantageous use of the high performance adsorption heat exchanger ADS-HX (1) described above is in combination with an atmospheric water harvesting device.

Description

Technical Field

[0001] This invention relates to the field of energy, and in particular to the adsorption and storage of water vapor directly from ambient air under any type of climatic conditions.

[0002] In particular, the present invention relates to adsorption heat exchangers.

[0003] The present invention also relates to a method for manufacturing the above-described adsorption heat exchanger.

[0004] The adsorption heat exchanger of the present invention is preferably and advantageously used in conjunction with an atmospheric water collection device described by the same applicant in international application publication number WO 2019 / 082000A1.

[0005] Preferred applications of the present invention are atmospheric water harvesting (freshwater production using the atmosphere as a source for civil, agricultural and industrial end-use) and air dehumidification for drying industry and air conditioning (removing water vapor from airflows used as process fluids in industrial applications (e.g., food and / or cargo drying, gas fields, etc.) and / or human thermal comfort applications). Background Technology

[0006] Atmospheric water harvesting, the ability to capture large amounts of water vapor from ambient air and convert it into potable freshwater, can address the growing demand for freshwater in countries affected by natural and / or economic water scarcity.

[0007] Existing solutions for removing water vapor from the air and converting it into fresh water mainly employ two methods: desiccant systems and vapor compression systems.

[0008] Desiccant systems utilize the hygroscopic properties of adsorbent materials that can directly remove water vapor when exposed to air; once saturated with moisture, the desiccant material needs to be regenerated to restore its initial adsorption capacity; the water absorption rate and capacity of the adsorbent material determine its performance (the latter depends on ambient air conditions, especially low water vapor content in the ambient air leading to low water absorption rate and high regeneration temperature).

[0009] Examples of desiccant systems can be found in US 8118912 B2, entitled "LOW POWER ATMOSPHERIC WATER GENERATOR"; US 8876956 B2, entitled "SYSTEM FOR WATER RECOVERY INLUDING MULTIPLE POWER SOURCES"; US 10640954 B2, entitled "SORPTION-BASED ATMOSPERIC WATER HARVESTING DEVICE"; WO 2018002918A1, entitled "LIQUID DESICANT VAPOR SEPARATION SYSTEM"; US 6511525 B2, entitled "METHOD AD APPARATUS FOR EXTRACTING WATER FROM AIR USING ADESICCANT"; and US 6511525 B2, entitled "METHOD AND APPARATUS FOR PRODUCING POTABLEWATER FROM AIR INLUDIG SEVEREY ARID AD HOT". US patent 20070028769 A1, entitled "Climates"; US patent 6336957 B1, entitled "Methods and Apparatus for Etracting Water from Atmospheric Air"; WO 2016081863, entitled "Systems and Methods for Generting Liquid Water from Air"; and WO 2019071202, entitled "Systems for Generating Water with Waste Heat and Relatedemeths Therefor". However, the technical solution disclosed in US 8118912 B2 is a system for providing drinking water based on the capture of moisture from ambient air by drying wheels. These wheels are then regenerated to condense the generated steam. The disadvantage of this solution is the use of drying wheels as drying components. This type of component cannot co-located for heat and mass transfer. Therefore, hotter and drier climates require higher regeneration temperatures, which negatively impacts efficiency and water production. Furthermore, the condensation stage is driven by a vapor compression refrigeration cycle, increasing the power intensity of this solution.

[0010] However, the technical solution disclosed in US 8876956 B2 is a system that uses a liquid desiccant to remove moisture from the air, followed by an extraction cycle driven by an external heat source to recover the water collected in the condenser. A disadvantage of this solution is the direct contact of calcium chloride with other machine parts and materials. Calcium chloride, as a desiccant, is highly corrosive and will cause numerous maintenance problems. Furthermore, component manufacturing does not anticipate the possibility of co-location heat and mass transfer, or the recovery of latent heat from steam condensation.

[0011] However, the technical solution disclosed in US 10640954 B2 is a passive water collection device based on a metal-organic framework hygroscopic material. Regeneration involves exposing the material to radiation intensity close to 1 kW / m². 2 This is achieved by dissipating the condensation heat to the external environment under sunlight through a passive metal radiator. A drawback of this solution is the use of a passive condenser, which limits the heat consumption required for water condensation. Furthermore, component manufacturing is limited to a regeneration process that exposes the adsorbent to direct sunlight. This restricts the development and utilization of alternative heat sources, such as waste heat. Additionally, the scalability of this solution is limited by the available free surface exposed to sunlight, with expansion proportional to water demand.

[0012] However, the technical solution disclosed in WO 2018002918 A1 is an atmospheric moisture harvesting system in which water vapor is separated from the air using a liquid desiccant subsystem. A refrigeration unit condenses the water vapor released from the solar-regenerated liquid desiccant. A disadvantage of this solution is that it utilizes an auxiliary refrigeration cycle to drive water condensation at temperatures of 4-15°C, thus reducing the energy advantage gained from using the desiccant. Finally, this solution requires consistent desiccant regeneration heat and consistent condensation power.

[0013] However, the technical solution disclosed in US 6511525 B2 is a method and apparatus for extracting liquid water by adsorbing water from the air into a desiccant and compressing the water vapor released during adsorbent regeneration, then condensing the same vapor into liquid water. The disadvantage of this solution is that driving the adsorption / regeneration / condensation cycle to produce water requires mechanical energy, followed by electricity; in practice, regeneration is achieved by creating a vacuum in the adsorbent chamber, rather than using solar energy or other economical heat sources. Furthermore, condensation requires an active component with consistent power requirements.

[0014] However, the technical solution disclosed in US 20070028769 A1 is a system using an adsorption-desorption-condensation cycle with an adsorption wheel to extract moisture from ambient air and concentrate water vapor discharged from the adsorbent material in a circulating gas, from which liquid water is condensed. As previously mentioned, the use of a rotating drying component (such as a drying wheel) operating simultaneously during adsorption and regeneration suppresses the possibility of co-existing heat and mass transfer. Compared to systems using co-existing heat and mass transfer, such as those employing isothermal methods, as described in WO 2019082000A1 (“METHOD FOR PRODUCTION OF WATER FROM AIR BASED ON LOW-TEMPERATURE HEAT, AND MACHINE AD SYSTEMTHEREOF”, published by the same author of this invention, this method would require higher regeneration temperatures (>80°C) in hot, arid climates. Furthermore, in some configurations, condensation is driven by a refrigeration cycle.

[0015] However, the technical solution disclosed in US 6336957 B1 involves using adsorbent materials and varying temperatures to alter the pressure within a tightly sealed chamber, thereby alternately driving adsorption and desorption processes to extract water from the atmosphere. The disadvantages of this solution are the need for consistent pressure changes, followed by the requirement for a pressure-resistant seal. Furthermore, a partial vacuum is required to condense water vapor. This solution is highly complex, operates at high temperatures, and may hinder its application at very low cost.

[0016] However, the technical solution disclosed in WO 2016081863 is a system that uses solar energy and a drying wheel to extract water vapor from the atmosphere. As mentioned above, with these types of components, regeneration is adiabatic and requires high temperatures to achieve regeneration in very dry environments.

[0017] However, the technical solution disclosed in WO 2019071202A1 is a system that couples a drying device with an independent heater powered by an external waste heat source, which then powers the water collection cycle. Since the adsorption / regeneration process occurs simultaneously on some rotating drying components, regeneration temperature issues are expected, particularly in hot and arid climates. Finally, in this case, the limiting factor for the development of adsorbent materials is the improvement of co-located heat and mass transfer.

[0018] In contrast to techniques in the references and other known literature not listed, the technique proposed in this invention is based on an architecture capable of simultaneous mass and heat transfer, employing a cosonic transfer between multiple elements: the adsorbent material, water vapor, and a heat carrier providing heat or cold. Furthermore, the adsorbent composition allows for high performance using alginate-derived hygroscopic biopolymers under low regeneration temperatures and extensive drought conditions.

[0019] Vapor compression systems utilize the typical compression process of evaporating / condensing fluids to lower the air temperature to the dew point, thus developing a refrigeration cycle; water vapor is extracted by condensation at temperatures below the relative dew point; power consumption depends on ambient air conditions (the higher the temperature, the more energy is required to condense water vapor; the drier the air, i.e., the lower the dew point, the more energy is required to condense water vapor).

[0020] Examples of vapor compression systems include, for instance, US 20100083673 A1, entitled "WATER PRODUCTION SYSTEM AND METHODWITH AIR BYPASS"; KR 20160087805 A, entitled "ATMOSPHERIC WATER GENERATION SYSTEM AND METHOD"; US 6684648 B2, entitled "APPARATUS FOR THE PRODUCTION OFFRESHWATER FROM EXRTEMELY HOT AND HUMID AIR"; TW 593849 B, entitled "APPARATUS AND METHOD FOR EXTRACTING POTABLE WATER FROM ATMOSPHERE"; US7861544 B2, entitled "APPARATUS AND METHODS FOR CREATING SPARKLING WATER FROM THE ATMOSPHERE"; and US 7861544 B2, entitled "REFRIGERATION APPARATUS CONFIGURED TO CAPTURE". US 20200141095 A1, titled "ATMOSPHERIC WATER"; WO 2018167774 A1, titled "SYSTEM AND METHOD FOR HIGH-EFFICIENCYATMOSPHERIC WATER GENERATOR AND DEHUMIDIFIER"; CN 2675002 Y, titled "DOMESTIC AIR WATER DRINKING MACHINE"; and US 8627673 B2, titled "ATMOSPHERIC WATER HARVESTERS".

[0021] However, all the technical solutions disclosed in the references concerning vapor compression chillers share a common drawback: they are highly energy-intensive, limiting their use in remote and arid regions where electricity and water are scarce. Furthermore, power consumption depends on the dew point of the air being processed, increasing continuously when the dew point is very low. Additionally, the auxiliary equipment necessary to power these technologies with renewable energy sources such as photovoltaics or wind power increases basic investment and system complexity.

[0022] In addition, the problem of separating / capturing water vapor from ambient air for use in air conditioning still needs to be solved.

[0023] For air conditioning, removing water vapor from the regulated indoor environment improves human thermal comfort.

[0024] The standard technologies that drive this process are very energy-intensive. In particular, they typically use high-temperature thermal inputs, do not integrate solar energy, and / or they waste the heat from air conditioning systems. Therefore, in general, standard technologies do not meet the framework of Sustainable Development Goal 7 (SDG 7), which requires the development of more renewable energy sources to meet the growing global cooling demand.

[0025] Known solutions for air conditioning can be found in US 20160195312, entitled "AIR CONDITIOINING AND WATERHARVESTING"; CA 2736085, entitled "COMBINED AIR CONDITIONING AND WATERGENERATING SYSTEM"; US 8607583 B2, entitled "COMBINATION DEHYDRATOR, DRY RETURN AIR AND CONDENSED WATER GENERATOR / DISPENSER"; US 8506675 B2, entitled "COMPOSITE DESICCANT AND AIR TO WATER SYSTEM AND METHOD"; and CN 105229386 B, entitled "ON-CEILING LIQUID DESICCANT AIR CONDITIOINING SYSTEM".

[0026] However, the technical solution disclosed in US 20160195312 is a system that provides air conditioning and atmospheric water collection based on a vapor compression refrigeration unit.

[0027] Similarly, the technical solution disclosed in CA 2736085 is a system in which cooling elements condense water from the atmosphere and are operable to switch between an air conditioning mode for building cooling and a pure water generation mode. The cooling elements are cooled by vapor compression technology.

[0028] The technical solution disclosed in US 8607583 B2 is a portable device for alternately supplying water from a condensate reservoir or an alternative bottled water source. The system can then supply purified water and dried supplemental cool air to a home, office, or dehydration cabinet. All three solutions suffer from the drawbacks of typical coolers described in the previous section regarding vapor compression technology. The main issues involve energy costs and the significant use of electricity.

[0029] However, the technical solution disclosed in US 8506675 B2 employs a composite desiccant material composed of PVA foam or nonwoven fiber sheets immersed in a CaCl2 solution. The multi-chamber stacking of the membrane in this sheet constitutes an atmospheric water collection system. The disadvantage of this solution is that the use of membranes avoids direct contact between the desiccant itself and the air, thus preventing air pollution. This technical solution increases vapor mass transfer resistance, reducing the kinetics of the water production process. Furthermore, since the desiccant is a liquid fluid, it needs to be pumped to ensure system operation, increasing energy costs.

[0030] However, the technical solution disclosed in CN 105229386 B is an air conditioning system based on liquid desiccant. The desiccant is contained in a vapor permeation membrane to avoid contaminating the treated air or leaking harmful and highly corrosive liquid desiccant. A disadvantage of this solution is the use of a selective membrane that only allows water vapor to pass through, and which inherently provides resistance to vapor mass transfer. As before, the main problems with this type of technology are reduced kinetics in the water production process and increased energy costs associated with desiccant pumping.

[0031] None of the above-mentioned technical solutions or any combination thereof can provide an exchanger that can directly adsorb and store water vapor from ambient air, thus making it feasible for any type of humid or arid climate.

[0032] Furthermore, none of the above-mentioned technical solutions or any combination thereof can provide an exchanger that can perform rapid water capture / regeneration cycles without being affected by mass transfer kinetic resistance.

[0033] Furthermore, none of the above-mentioned technical solutions or any combination thereof can provide an exchanger that increases the total water production by employing a technical solution capable of achieving co-located heat and mass transfer.

[0034] Furthermore, none of the above-mentioned technical solutions or any combination thereof can provide a manufacturing technology for exchanging equipment that captures water vapor even under the high ambient temperature and low relative humidity conditions of a typical arid climate.

[0035] Therefore, even though many technological solutions are available, there is still a need for systems that separate / capture water vapor from ambient air for atmospheric water harvesting and air conditioning.

[0036] Specifically, there is still a need for a high-performance, competitive, efficient, and flexible heat and mass exchanger for water vapor capture.

[0037] Furthermore, there remains a need for a method to produce high-performance, competitive, efficient, and flexible heat and mass exchangers for separating / capturing water vapor from ambient air for atmospheric water harvesting and air conditioning.

[0038] Therefore, simply put, to date, to the applicant's knowledge, there is no known solution that can provide an exchanger for water vapor capture and a method for producing said exchanger that achieves the following characteristics:

[0039] - It exhibits a high water absorption capacity under dry climatic conditions, particularly at 20-35℃ (preferably 20-30℃), 1 kPa water vapor pressure, and a regeneration temperature of 60℃, achieving a dry-wet water absorption capacity difference of 0.7 kg. H2O / kg 干吸附剂 ;

[0040] - Achieves biocompatibility because the production process of the adsorbent material in the final configuration does not involve the use of toxic compounds; the production process requires only food-grade chemicals, eliminating any risk of contamination from the liquid water and / or conditioned air produced;

[0041] - Performance is a significant improvement over current commercial methods used for water vapor capture;

[0042] - To meet the growing demand for reliable, sustainable and affordable solutions that can provide freshwater even in remote areas;

[0043] - Enables rapid cycles of water capture / regeneration;

[0044] -Use inexpensive and industrially available raw materials;

[0045] - Manufactured by injection molding: The adsorbent and its components are in the form of a viscous fluid before solidification through a gelation process; this facilitates the initial injection of the fluid into a mold, followed by driving gelation at ambient temperature and pressure to produce the desired final hydrogel shape;

[0046] - Apply the same deep coating process to the heat exchange surfaces of various substrates (such as aluminum, copper, polymer materials and other thermally conductive and impermeable media);

[0047] - Materials can be manufactured in a way that is easily scalable; the production processes for materials and components do not require the construction of specific production environments, thus reducing the production costs of materials and components;

[0048] - It provides a scalable, low-cost, and rapidly functionalized switch manufacturing process that overcomes the shortcomings of previously proposed processes;

[0049] -Suitable for use in any climate conditions.

[0050] Therefore, the applicant has corrected these disadvantages by utilizing the water vapor capture exchanger and related methods for producing the exchanger as described in this invention. Summary of the Invention

[0051] One object of the present invention is to overcome the disadvantages of known prior art related to systems for separating / capturing water vapor from ambient air for atmospheric water harvesting and air conditioning.

[0052] A specific object of the present invention is to overcome the shortcomings of known prior art related to high-performance, competitive, efficient and flexible heat and mass exchangers for water vapor capture.

[0053] A more specific objective of this invention is to overcome the shortcomings of known prior art related to exchangers that capture water vapor under conditions of high ambient temperature and low relative humidity, even in typical arid climates.

[0054] Therefore, the present invention aims to solve the problem of separating / capturing water vapor from ambient air for use in atmospheric water harvesting and air conditioning.

[0055] In particular, the present invention aims to provide a high-performance, competitive, efficient and flexible heat and mass exchanger for water vapor capture.

[0056] The present invention also provides a method for producing high-performance, competitive, efficient and flexible heat and mass exchangers for separating / capturing water vapor from ambient air for atmospheric water harvesting and air conditioning.

[0057] The present invention discovers a preferred and advantageous application in conjunction with an atmospheric water collection device described by the same applicant in international application publication number WO 2019 / 082000 A1.

[0058] As can be seen from the following description, the above and other objects and advantages of the present invention are achieved by an adsorption heat exchanger.

[0059] Furthermore, the above and other objects and advantages of the present invention are achieved by an atmospheric water collection device.

[0060] Furthermore, the above and other objects and advantages of the present invention are achieved by a method of manufacturing an adsorption heat exchanger.

[0061] It should be understood that all appended claims form part of this specification, and each technical feature claimed therein may be independently and autonomously available in relation to other aspects of the invention.

[0062] Obviously, several modifications can be made to the description without departing from the scope of the invention as claimed in the appended claims (e.g., in relation to shape, size, arrangement and components with equivalent functions).

[0063] Advantageously, the technical solution of the present invention allows for:

[0064] - It exhibits a high water absorption capacity under dry climatic conditions: at 20-35℃, preferably 20-30℃, and a water vapor pressure of 1 kPa, it can absorb 0.7 kg of water. H2O / kg 干吸附剂 Water absorption (on a dry basis);

[0065] - Achieving biocompatibility: The production process of the adsorbent material in the final configuration does not involve the use of toxic compounds; the production process only requires food-grade chemicals, eliminating any risk of contamination to the conditioned air and / or liquid water produced;

[0066] - Manufactured via injection molding: The adsorbent and its components are in the form of a viscous fluid before solidification through a gelation process; this facilitates the initial injection of the fluid into a mold, followed by driven gelation at ambient temperature and pressure to obtain the desired final hydrogel shape. Notably, the same process can be applied to deep coatings on heat exchange surfaces of various substrates, such as aluminum, copper, polymeric materials, etc.

[0067] - Materials are manufactured in a way that is easily scalable; the production processes for materials and components do not require the construction of specific production environments; this reduces the production costs of materials and components.

[0068] Other advantageous features will become more apparent from the following description of preferred but not exclusive embodiments, which are merely illustrative and not limiting. Attached Figure Description

[0069] The invention will now be described with reference to the accompanying drawings, which are illustrative and not restrictive. These drawings illustrate different aspects and examples of the invention, and similar structures, parts, materials, and / or elements in the different drawings are indicated by similar reference numerals, where appropriate.

[0070] Figure 1A A schematic diagram of the intermittent adsorption phase of ADS-HX containing a hygroscopic polymer as described in this invention is shown.

[0071] Figure 1B A schematic diagram of the regeneration stage of the intermittent action of ADS-HX containing a hygroscopic polymer as described in this invention is shown.

[0072] Figure 2 This is a schematic flowchart illustrating the steps required to form a honeycomb geometry by gelling sodium alginate ions in an ionic solution of water and divalent cations using molding technology according to the present invention.

[0073] Figure 3 This is a schematic flowchart illustrating the steps required to directly form the same honeycomb geometry on a heat exchanger according to the present invention;

[0074] Figure 4 The isothermal adsorption (IA) curves of the hygroscopic polymer described in this invention are shown; in particular, Figure 4 This illustrates the relationship between the pressure and temperature of water trapped in the material pores and water vapor in equilibrium contact;

[0075] Figure 5 A scanning electron microscope (SEM) image of the internal structure of the honeycomb described in this invention is shown;

[0076] Figure 6A This is a schematic diagram illustrating the reduction in polymer volume caused by the inherent shrinkage of the biopolymer during the curing stage and after ion gelation, as described in this invention.

[0077] Figure 6B The diagram illustrates the relationship between the volume reduction of the polymer and the concentration of calcium chloride (CaCl2) during the ion gelation process described in this invention. Calcium chloride is a non-exhaustive example of an aqueous solution of a divalent cation.

[0078] Figure 7 This is a schematic diagram of an atmospheric water collection device including the adsorption heat exchanger described in this invention;

[0079] Figure 8A The transient state required for the component to reach regeneration operating conditions (60°C) is shown, where the air flow rate is 1 m / s and the water flow rate is 60 liters / minute. This is a non-exhaustive example of the component's operating conditions. The figure shows the use of... Figure 8B The images show the different points captured by the infrared camera pointing vertically to the ADS-HX entry segment;

[0080] Figure 8B The temperature distribution was measured by observing the transient infrared camera during regeneration startup. As shown in the left figure, this is the portion of the infrared camera facing the ADS-HX.

[0081] Figure 9A The time required to reach equilibrium conditions, which correspond to a 25% increase in water absorption, and the relative humidity corresponding to the equilibrium value are described.

[0082] Figure 9B The functional diagram of ADS-HX is shown, demonstrating the equilibrium water absorption (at 0.25-0.5-0.75-1 g) achieved under the following conditions: airflow of 1 m / s, air temperature of 30°C, and relative humidity of 15-28-45-57-70-75%. H2O / g 干吸附剂 (Increase gradually) the required time; Detailed Implementation

[0083] While various modifications and alternative constructions may be made to the invention, some preferred embodiments are shown in the accompanying drawings and will be described in detail below.

[0084] However, it should be understood that the present invention is not limited to the specific embodiments shown, but rather covers all modifications, alternative constructions and equivalents that fall within the scope of the invention as defined in the claims.

[0085] Therefore, in the following description, unless otherwise stated, “for example,” “etc.” and “or” mean unrestricted, non-exclusive alternatives; unless otherwise stated, “also” means “in which, but not limited to”; and unless otherwise stated, “including / contains” means “including / contains but not limited to”.

[0086] In this specification, the following terms have the following meanings:

[0087] A heat mass exchanger is a component that provides support for the exchange of heat and mass (in the form of steam) between air, adsorbent, and heat carrier.

[0088] "Composite materials" refer to media in which a material composition is a significant combination of components with different properties. Combinations of different components result in composite materials with improved properties compared to individual components.

[0089] "Biocomposite materials" refer to composite media whose main components are derived from natural substances, or are composed of natural substances, or are obtained through biological activities.

[0090] "Biopolymer" refers to a monomer polymer structure derived from natural substances or obtained through biological activities;

[0091] "Hydrogel" refers to a colloidal gel composed of hydrophilic polymer chains typically dispersed in water. A specific aspect of this invention is a solid obtained by ion-gelling of polysaccharide chains from sodium alginate;

[0092] "Hygroscopicity" refers to the ability of a substance to first attract and then retain water molecules in the form of water or liquid through absorption and / or adsorption.

[0093] "Hygroscopic composite biopolymer" refers to a composite material in which the main component simultaneously or individually possesses the properties defined by "hygroscopicity" and "biopolymer"; in this specification, the terms "hygroscopic composite biopolymer", "adsorbent" and "adsorbent polymer" are used as synonyms without distinction.

[0094] "Heat exchange medium" refers to a component that provides support for heat exchange between two or more materials;

[0095] "Cooling fluid" refers to a heat carrier composed of fluid (liquid or gas) whose function is to remove heat from a specific material (solid, gas or liquid) or multiple materials;

[0096] "Heating fluid" refers to a heat carrier composed of fluid (liquid or gas) whose function is to provide heat to a specific material (solid, gas or liquid) or multiple materials;

[0097] "Adsorption phase" refers to the time period during which the mass transfer of water moves from the air mass to the porous structure of the adsorbent; in this specification, the terms "adsorption" and "capture" are used as synonyms without distinction.

[0098] The “regeneration phase” refers to the time period during which the mass transfer of water occurs from the porous structure of the adsorbent to the air mass; in this specification, the terms “regeneration” and “release” are used as synonyms without distinction.

[0099] "High performance" refers to improvements in the inherent properties that affect the function and performance of components / materials. The term "high performance" and similar terms used to mean: reduced time for complete adsorption and regeneration; increased water absorption at lower relative humidity and higher outdoor temperatures; reduced regeneration temperature; increased difference in water absorption between the end of the adsorption state and the end of the regeneration state; and reduced resistance to mass transfer through conduction and diffusion.

[0100] "Homogeneous fluid" refers to a fluid composed of materials with different properties and phases, which are fully mixed so that the overall concentration of different single elements or phases is constant.

[0101] "Mass transfer" refers to the mass transfer between the air mixture and the adsorbent material during adsorption or regeneration, and in the context of this invention, it refers to the mass of water vapor.

[0102] This invention is based on an innovative concept of providing a new exchanger made of innovative materials and with an innovative geometry, which is able to capture water vapor from ambient air even under the high ambient temperature and low relative humidity conditions typical of arid climates, for use in atmospheric water harvesting and air conditioning.

[0103] In particular, the present invention provides a high-performance, competitive, efficient and flexible heat and mass exchanger for water vapor capture.

[0104] The present invention discovers a preferred and advantageous application in conjunction with an atmospheric water collection device described by the same applicant in international application publication number WO 2019 / 082000 A1.

[0105] The following will refer to Figure 1 to... Figure 7 The invention relates in detail to various individual aspects, including:

[0106] - Adsorption heat exchanger 1;

[0107] - An atmospheric water collection device 10 including at least one adsorption heat exchanger 1; and

[0108] - Method for manufacturing adsorption heat exchanger 1.

[0109] This invention discloses an innovative high-performance adsorption heat exchanger ADS-HX 1 using a hygroscopic composite biopolymer, i.e., adsorbent 2; this invention also discloses an innovative method for realizing the high-performance adsorption heat exchanger 1.

[0110] The following explanations are in order: i) the function and motivation of ADS-HX, and ii) the procedure for manufacturing ADS-HX using composite biopolymers.

[0111] i) Function and Motivation

[0112] The ADS-HX 1 is an intermittently operating component that performs co-location heat and mass transfer.

[0113] Its working principle is based on the alternation of water vapor capture / release phases (a process known as "mass transfer") and heat exchange between adsorbent material 2 and cold / heat sources 6 and 8 (a process known as "heat transfer").

[0114] The co-location of heat and mass transfer results in a higher water vapor exchange rate between the air mixture and the adsorbent material 2.

[0115] By using a honeycomb geometry, the contact area between the adsorbent 2 and the heat exchange medium 4 is increased, reducing the pressure drop generated during airflow through the adsorbent channel.

[0116] Referring to Figure 1, during the capture phase (also known as the "adsorption phase"), a humid gas flow passes through a channel created by the adsorbent polymer 2.

[0117] In the air / adsorbent contact area, water vapor separates from the air and is stored in the pores of the hygroscopic polymer 2.

[0118] Because this process is exothermic, it releases a large amount of heat (called "heat of adsorption," approximately 2500 kJ / kg, totaling less than 50 kJ / mol), raising the equilibrium temperature between adsorbent 2 and the air, thereby reducing the separation and capture rate of water vapor in humid air. In fact, as... Figure 4 As shown, increasing the adsorption operating temperature reduces the amount of water absorbed by the adsorbent when it is in equilibrium with the air mixture.

[0119] The presence of heat exchange medium 4 allows the generated adsorbed heat to be transferred to the cooling fluid and discharged to the external radiator (20°C). <T 散热器 At temperatures below 40℃, this heat of adsorption can be removed from the adsorbent material 2, thereby achieving an isothermal or supercooled process.

[0120] An impermeable and conductive frame separates the cooling fluid 6 from the adsorbent material 2, preventing water bypass and allowing energy transfer only through thermal conduction between the adsorbent / air and the cooling carrier.

[0121] The outlet airflow from the adsorbent channel is drier and cooler than the inlet airflow, making it suitable for any air conditioning application or industrial drying process.

[0122] Ultimately, when the outlet air is treated via evaporative cooling, this configuration falls under the category of evaporative cooling technology for desiccants used in building air conditioning systems. The adsorption phase continues until the adsorbent is saturated (at a temperature of 30°C, the water absorption can exceed 0.7 kg). H2O / kg 干吸附剂 ).

[0123] When saturation is reached, the ADS-HX 1 switches to the regeneration phase, thereby reversing the direction of heat and mass transfer.

[0124] At this point, the cooling fluid 6 is replaced by the heating fluid 8, transferring heat from the heat source (T). 热源 <100°C, preferably about 60°C, to utilize solar energy or industrial or process waste heat to transfer to the adsorbent material 2.

[0125] This provides energy (2500-3000 kJ / kg - approximately 2500 kJ / kg) to the water molecules previously trapped in the pores of the hygroscopic polymer 2, thereby initiating the diffusion flux of water from the wet adsorbent to the air flowing in the same channel.

[0126] Uniform heat transfer, achieved through prolonged continuous contact between adsorbent 2 and the heat exchange conductive frame, is increased and accelerated, thus accelerating water transfer.

[0127] Currently, the outlet airflow is hot and very humid, with a very high dew point, thus driving spontaneous condensation at ambient temperature and collecting liquid water. If, at this stage, the ADS-HX is combined with the method described in WO 2019 / 082000 A1 from the same applicant, it is noteworthy that an improved water collection device can be achieved using 60°C thermal energy without the need for refrigeration or cooling cycles to condense water from the air.

[0128] The regeneration process continues until the adsorbent polymer 2 reaches its dry state.

[0129] ii) Production process

[0130] ADS-HX 1 is achieved by combining an air / liquid or air / gas heat exchange medium 4 with a hygroscopic polymer 2, resulting in a high contact area between air / adsorbent / heat exchange medium, which can improve the transfer rate of water vapor and energy, while the pressure drop on the air side is low.

[0131] The heat exchange medium 4 is made of a material selected from metals, plastics and any conductive composite materials.

[0132] Hygroscopic polymer 2 was obtained by ion-gelation of sodium alginate, a polysaccharide widely distributed in the cell walls of brown algae.

[0133] The first step in the ADS-HX 1 production process is to create a viscous gel containing hygroscopic polymeric main components (i.e., sodium alginate and calcium-based bentonite).

[0134] A viscous gel was prepared by mixing powders of sodium alginate (2 wt%) and calcium-based bentonite (4-10 wt%) with deionized water until a homogeneous fluid was obtained.

[0135] Dissolve calcium-based bentonite powder in 1 liter of deionized water (DIW) (1-20% by weight) and stir at high speed (>700 rpm) for 1 hour.

[0136] The solution was filtered multiple times (final sieve mesh <5μm) to remove impurities and undissolved particles from the water / bentonite liquid solution, with alternating short stirring phases (10 minutes, speed >700 rpm).

[0137] Add a gelling agent, such as sodium alginate, to the bentonite / DIW solution at a concentration of 0.5-4%, and mix rapidly until the solution is completely homogeneous.

[0138] The obtained viscous gel was degassed under a vacuum of 200-500 mbar relative pressure for at least 20 minutes.

[0139] Simultaneously prepare a DIW / CaCl2 solution (5-40% by weight of CaCl2), continuously stirring the water and salt until the solution is ready for use and the temperature drops to ambient temperature.

[0140] The degassed viscous gel, namely a degassed viscous solution of sodium alginate / bentonite / DIW, is injected into a prefabricated mold with an optimized geometry, namely a honeycomb geometry, for a specific process.

[0141] Then, immerse the entire mold deeply in the DIW / CaCl2 solution for at least 12 hours until it is completely gelled.

[0142] Sodium alginate is a polymer composed of repeating blocks of guluronic acid and mannuronic acid monomers, and it is the initiator of the cross-linking process: it contains water and divalent cations (Ca). +2 Mg +2 In the presence of an ionic solution of (etc.), the crosslinking process leads to the gelation of viscous fluids to form solid hydrogels.

[0143] In this process, bentonite fills the spaces between polymer chains and, as a highly porous, hygroscopic clay, increases the water-trapping capacity of the composite polymer material.

[0144] The crosslinking process that transforms viscous gels into solid hydrogels is achieved through ionogelation technology, in which Na, contained as a functional group in alginate, is utilized. + With Ca dissolved in aqueous solution +2 Cation (or one of the other cations mentioned above) exchange.

[0145] Because calcium has a higher valence, this activates the cross-linking between different polymer chains of alginate, achieving the so-called "egg-box geometry".

[0146] The process takes place inside a mold to shape the hydrogel into the desired geometry.

[0147] Figure 2 The steps of the above process are schematically illustrated, showing the fabrication of the honeycomb geometry of the composite polymer.

[0148] The same method can be used to create honeycomb geometries directly on heat exchangers, such as... Figure 3 As shown.

[0149] The proposed technical solution expands the potential of the atmospheric water harvesting device described by the same applicant in the international application with publication number WO 2019 / 082000 A1.

[0150] The innovative features of this invention come from the combination of novel hygroscopic polymers within heat transfer and / or heat conduction devices.

[0151] The final product is a component characterized by its high water absorption capacity, low regeneration temperature, and high regeneration rate in a wide range of operating environments due to the increased contact between the material and the heat exchanger medium.

[0152] Due to the adsorption properties of the composite hydrogel, multiple moisture capture / regeneration cycles can be performed daily at a temperature of around 60°C.

[0153] refer to Figure 4 The figure illustrates the main advantage of this invention, namely, high water absorption.

[0154] Figure 4 The water absorption capacity of the polymer at different temperatures and pressures under equilibrium water vapor conditions is shown.

[0155] During the adsorption phase (operating under typical dry conditions at temperatures of 20-35°C and water vapor pressures of 0.6-1 kPa), the water absorption capacity can reach up to 0.8 kg.H2O / kg 干吸附剂 (Under the same operating conditions, the most common moisture-absorbing material, silica gel, has a water absorption rate of 10-15%, preferably less than 0.1 kg.) H2O / kg 干吸附剂 As shown in US10640954B2, under the same operating conditions, the maximum water absorption of MOF and other innovative materials is 0.2-0.3 kg. H2O / kg 干吸附剂 ).

[0156] Regeneration can be carried out at temperatures as low as 60°C, and at ambient temperatures as high as 35°C, regeneration can reduce the water content to 0.1 kg. H2O / kg 干吸附剂 Furthermore, at ambient temperature, the minimum pressure achievable for a single water collection cycle on this material to condense the released water vapor is 5.6 kPa (corresponding to the saturation pressure of water vapor at 35°C). Under these conditions, no reference material can release vapor at pressures exceeding this value, requiring an auxiliary cooling source to drive the complete water collection cycle under these conditions, and also requiring auxiliary electricity and energy. Under the above conditions, the total water volume obtained from the entire adsorption / regeneration cycle is equivalent to 0.7 kg. H2O / kg 干吸附剂 Quality changes, such as Figure 4 As shown.

[0157] The scheme also utilizes the high density of the polymer (650kg). 干吸附剂 / m 3 This increases the overall specific density of machines based on this component. In fact, each cubic meter of composite material can extract up to 480 liters of water, enough to supply water daily for a small community of no more than 32 people (in Sustainable Development Goal 6, WASH-UNICEF stipulates a minimum requirement of 15 liters of fresh water per person per day for drinking, cooking and sanitation).

[0158] like Figure 5 As shown in the SEM images, these improved properties are achieved due to the high internal porosity and high internal surface extension of the composite polymer.

[0159] refer to Figure 6A and 6B The figure illustrates and comments on the stability of the coating. The coating on the surface of the heat exchanger HX is achieved more through mechanical effects than through chemical bonding between the HX material and the polymer. This mechanical effect is due to the pressure effect generated by the thermal shrinkage of the polymer during the drying stage after molding.

[0160] The coating completes the heat exchanger manufacturing process. This is due to the tension effect generated by the thermal shrinkage of the polymer during the curing stage, thus completing the heat exchanger manufacturing process. After ionogelation, the polymer is in a superhydrated state, which ends once the material is cured at 70-90°C for 12 hours. During the curing process, the polymer exhibits consistent volume shrinkage, such as... Figure 6B As shown, this depends on the concentration of CaCl2, which is close to 90% of the initial volume when the CaCl2 concentration is below 10%. This volume reduction creates permanent stress in the material, leading to cohesion on the HX surface. This type of adhesion is considered an improved solution compared to typical adsorbent material coatings on thermally conductive materials (e.g., metals) operated by chemical binders, as it does not experience the typical degradation problems of chemical binder coating methods. In fact, they typically undergo hydration; internal structural stresses lead to crack formation when subjected to rapid heating / cooling cycles; and the final composition of binder plus adsorbent results in a reduction in water absorption proportional to the binder / adsorbent ratio due to its inertness relative to water; this is discussed in l) Kalmutzki, MJ; Diercks, CS; Yaghi, OM Metal-Organic Frameworks for Water Harvesting from Air. Advanced Materials. Wiley-VCH Verlag September 13, 2018.

[0161] https: / / doi.org / 10.1002 / adma.201704304 .

[0162] 2) A.Freni, L.Bonaccorsi, L.Calabrese, A.Capri, A.Frazzica,A.Sapienza.SAPO-34 coatedadsorbent heat exchanger for adsorption chillers,Applied Thermal Engineering,Vol.82,2015,pg.l-7, https: / / doi.org / 10.1016 / j.applthermaleng.2015.02.052 .

[0163] This invention proposes a method for inducing mechanical adhesion between the adsorbent and the heat exchange medium based on the thermal shrinkage of the adsorbent itself. This is achieved by curing the material after a gelation process. The water discharged during curing shortens the distance between different parallel chains of the biopolymer, reduces the overall volume of the composite, and increases the concentration of divalent ions diluted by water in the hydrogel. This further increases the crosslinking between polymer chains, which remains stable after curing, forming an adhesion layer around the solid structure of the heat exchanger, such as... Figure 6A As shown.

[0164] This type of adhesion is not affected by the degradation problems typical of chemical binder coating methods, but is achieved through the material itself as the adsorbent.

[0165] An adsorption heat exchanger according to one aspect of the present invention, used independently and autonomously relative to other aspects of the present invention, comprises a hygroscopic composite biopolymer 2, a heat exchange medium 4 in contact with the hygroscopic composite biopolymer 2, and a hollow pipe in contact with the heat exchange medium 4, wherein a cooling fluid 6 or a heating fluid 8 alternately passes through the hollow pipe.

[0166] The hygroscopic composite biopolymer 2 contains a predetermined ratio of sodium alginate and calcium-based bentonite, and the heat exchange medium 4 has a honeycomb geometry, so that the adsorption heat exchanger 1 can operate under the typical high ambient temperature and low relative humidity conditions of arid climates.

[0167] Preferably, the predetermined ratio between sodium alginate and calcium-based bentonite is in the range of 1:1 to 1:10; more preferably, the predetermined ratio between sodium alginate and calcium-based bentonite is 1:1 to 1:2.

[0168] Preferably, the concentration of sodium alginate is 0.5 to 4% of the total mass of the supersaturated hydrogel.

[0169] Preferably, the honeycomb geometry has a honeycomb size range of 3-5 mm, and the vertical distance between honeycombs is no greater than half the honeycomb size. This geometry is inserted between two heat transfer elements to form a structure as follows: Figure 3 The diagram shows a repeating base for an adsorption heat exchanger. The shape and cross-section of the heat exchanger pipes can differ from those shown without altering the inherent characteristics of the configuration. This also applies to using conductive fins to increase the surface area of ​​the heat exchange medium, or using different materials for the heat exchange medium.

[0170] According to another aspect of the invention, which is used independently and autonomously relative to other aspects of the invention, and with reference to Figure 7 This document discloses an atmospheric water collection device 10, which is obtained by connecting the present invention to an atmospheric water collection loop. The atmospheric water collection device 10 enables it to provide freshwater in various parts of the world where natural and / or economic water scarcity forces people to seek alternative solutions for obtaining water.

[0171] Preferably, the atmospheric water collection device 10 is the atmospheric water collection device described by the same applicant in international application with publication number WO 2019 / 082000 A1.

[0172] The atmospheric water collection device 10 includes at least one adsorption heat exchanger 1 as described above, or is composed of multiple modules connected in series or parallel, such as... Figure 7 As shown.

[0173] According to another aspect of the invention, which is used independently and autonomously relative to other aspects of the invention, a method for producing an adsorption heat exchanger 1 is disclosed herein.

[0174] The method for producing adsorption heat exchanger 1 includes the following steps:

[0175] - Prepare hygroscopic composite biopolymer 2 by realizing a viscous gel containing the main components of hygroscopic polymer 2 (i.e., sodium alginate and calcium-based bentonite in a predetermined ratio) (step 100).

[0176] - Prepare a heat exchange medium 4 with a honeycomb geometry and contact it with the hygroscopic composite biopolymer 2 (step 101).

[0177] - Prepare a hollow tube and bring it into contact with the heat exchange medium 4 (step 102), and inject a viscous solution until all the spaces are filled with gel after the degassing step as described above. Then, finally drive the gelation process by deep immersion in a divalent ion / water solution;

[0178] -Alternately introduce cooling fluid 6 or heating fluid 8 into the hollow pipe (step 103).

[0179] The adsorption heat exchanger of the present invention, its preparation method, and its effects will be described in detail below with reference to the following examples, which were developed based on experimental tests and should be understood as illustrative but not limiting descriptions of the present invention.

[0180] Example 1

[0181] In the ADS-HX configuration, the total cell cross-section is close to 70% of that of ADS-HX, and the air-side pressure drop is less than 1 Pa / cm². 2 The average airflow velocity is 1 m / s. The thickness of ADS-HX is 15 mm, containing ~7 kg of dry adsorbent / m³. 2The ADS-HX piping system has a rectangular geometry with a 1x8 mm cross-section and a maximum channel thickness of 1 mm, allowing for good water flow at ambient temperatures during the adsorption phase (~30°C) or at regeneration temperatures during the regeneration phase (~60°C). According to experimental tests, at an airflow velocity of 1 m / s and a hot water flow rate of 60 L / min, the system requires 2.5 minutes to reach the equilibrium temperature (60°C) for regeneration phase activation, as shown in Figure 8. In this configuration, the airflow rate is sufficiently high to reduce mass transfer resistance to the alginate chain diffusion mechanism. Under these test conditions, the heat exchanger performance is as follows: Figure 9A and Figure 9B As shown. Figure 9A As shown, the single-step water absorption on the ADS-HX increased by 0.25 g within approximately 30 minutes. H2O / g 干吸附剂 The time to reach equilibrium is illustrated by referring to the relative humidity of ambient air at 30℃. After 30 minutes, all curves flattened, indicating equilibrium, corresponding to water absorption of 0.25, 0.5, 0.75, and 1g respectively. H2O / g 干吸附剂 ,like Figure 9B As shown. This means that approximately 7 kg of ADS-HX can capture 3.5 liters of water in less than an hour and requires the same amount of time to regenerate, as disclosed by one applicant in WO 2019 / 082000 A1, with a regeneration temperature of 60°C. If the system is powered by solar energy, 2-3 cycles can be easily performed per day, and if the atmospheric water harvesting system is arranged as disclosed in WO 2019 / 082000 A1, with two ADS-HX operating intermittently, a yield of 21 liters can be obtained in six hours of operation per day, with energy consumption not exceeding 1 kWh. th / Lift.

[0182] If the system is powered by a more stable heat source, such as waste heat from process or industry, and is planned to operate 24 hours a day, 12 cycles can be performed per day on a single ADS-HX, and if the atmospheric water collection system is arranged as disclosed in WO 2019 / 082000 A1, with two ADS-HX operating in an intermittent manner, the daily output is 84 liters.

[0183] As described below, the adsorption heat exchanger and its manufacturing method of the present invention are compared with known solutions. [Reference #1] describes adsorption / regeneration experiments conducted on MOF-801 under laboratory conditions (RH-controlled environment chamber with solar simulation) and outdoor conditions; [Reference #2] describes another configuration of the prototype based on MOF-801, equipped with optical lenses for concentrating solar radiation; [Reference #3] describes a MOF-801-based... The prototype of 303 uses solar photovoltaic panels to power the regeneration of resistive adsorbent materials; [Reference #4] is a solar-activated passive water collection device that uses a composite material consisting of a holding matrix in which molecular sieve MCM-41 is impregnated with CaCl2 at a concentration of 30-60%; [Reference #5] is a prototype equipped with a packed bed made of CaCl2-impregnated carbon fibers and regenerated by hot air drying, heated by a solar air collector; in [Reference #6], direct solar radiation is used as the free source for salt regeneration, and the weight changes of three different anhydrous salts (CuCl2, CuSO4, MgSO4) in completely dry and saturated states are observed; [Reference #7] shows the performance of another hydrogel based on polyacrylamide-CaCl2 containing carbon nanotubes to directly capture solar radiation, converting it directly into heat on the adsorbent surface, and then directly regenerating the adsorbent. The prototype shown in [Reference #8] consists of a rotating cylinder with a coating containing hollow carbon nanospheres, impregnated with LiCl, and operating at 0.8-1.2 kW / m². 2 Solar flux regeneration.

[0184] The table below summarizes the comparison results between the present invention and known solutions.

[0185]

[0186]

[0187]

[0188] The table above lists the most important information comparing the invention disclosed in this document with the references. Comparisons include: examining environmental conditions during adsorption; the amount of water absorbed during the adsorption phase; the regeneration temperature; and the change in water absorbed between the end of adsorption and the end of regeneration. All references in the table show adsorption performance with dew point conditions higher than the minimum requirements shown for the composite biopolymers disclosed herein. In fact, the dew point (T in the table)... 露点 Even at a temperature of 0.6℃ (equivalent to a dry-bulb temperature of 30℃ and a relative humidity of 15%), a considerable amount of water absorption (0.15 g) can be obtained. H2O / g 干吸附剂 This is a property that is difficult for other materials to achieve.

[0189] In almost all the references, the change in water absorption between the end of adsorption and the end of regeneration (the parameter identified in column Δw in the table) is lower than the value obtained by this invention under different RH conditions. Furthermore, the time required for adsorption and regeneration is much longer (3-4 times) than that experienced by the ADS-HX configuration disclosed in this document. Finally, in almost all the references, the regeneration temperature is much higher than the 60°C used in the ADS-HX configuration disclosed in this document.

[0190] Based on the above description, it can be inferred that the innovative technical solution described here has the following advantageous features:

[0191] - It has a large water absorption capacity under dry climate conditions, especially at 20-35℃, preferably 20-30℃ and 1kPa or lower water vapor pressure, where it can achieve a water absorption rate of 70% (dry basis).

[0192] -Biocompatibility, because the production process of the adsorbent material in the final configuration does not involve the use of toxic compounds; the production process only requires food-grade chemicals, eliminating any risk of contamination from the liquid water and / or conditioning air produced;

[0193] - Significantly improved performance compared to current commercial methods used for water vapor capture;

[0194] - To meet the growing demand for reliable, sustainable and affordable solutions that can provide freshwater even in remote areas;

[0195] - Rapid water capture / regeneration cycle;

[0196] -Use inexpensive and industrially available raw materials;

[0197] - Manufactured by injection molding: The adsorbent and its components are in the form of a viscous fluid before solidification through a gelation process; this facilitates the initial injection of the fluid into a mold, followed by driving gelation at ambient temperature and pressure to obtain the desired final shape of the hydrogel;

[0198] - The same process can be applied to deep coatings on the heat exchange surfaces of various substrates (such as aluminum, copper, polymer materials, etc.);

[0199] - Materials are manufactured in a way that is easily scalable; the production processes for materials and components do not require the construction of specific production environments, reducing the production costs of materials and components;

[0200] - The scalable, low-cost, and rapidly functionalizable switch manufacturing process overcomes the shortcomings of previously proposed processes;

[0201] -Suitable for use in any climate conditions.

[0202] Therefore, the present invention described herein represents a significant improvement over current commercial methods for capturing water vapor from ambient air, even under conditions of high ambient temperature and low relative humidity typical of arid climates. Furthermore, it addresses the growing need for efficient solutions for atmospheric water harvesting and air conditioning.

[0203] Therefore, it is clear from the above description that the adsorption heat exchanger and its production method described above can achieve the proposed objectives.

[0204] It will also be apparent to those skilled in the art that modifications and variations can be made to the solutions described with reference to the accompanying drawings without departing from the teachings of the invention and the scope defined in the appended claims.

Claims

1. A sorptive heat exchanger (1) comprising: - a hygroscopic composite biopolymer (2), - a heat exchange medium (4) in contact with said hygroscopic composite biopolymer (2), and - a hollow duct in contact with said heat exchange medium (4), into which a cooling fluid (6) or a heating fluid (8) alternately enters, characterized in that: - said hygroscopic composite biopolymer (2) comprises a predetermined proportion of sodium alginate and calcium bentonite, and in that: - said heat exchange medium (4) has a honeycomb geometry, so that said sorptive heat exchanger (1) can operate under conditions of high ambient temperature and low relative humidity typical of arid climates.

2. The sorptive heat exchanger (1) according to claim 1, wherein said predetermined proportion between sodium alginate and calcium bentonite is in the range of 1:1 to 1:

10.

3. The sorptive heat exchanger (1) according to claim 2, wherein said predetermined proportion between sodium alginate and calcium bentonite is 1:1 to 1:

2.

4. The sorptive heat exchanger (1) according to any one of claims 1 to 3, wherein the concentration of said sodium alginate ranges from 0.5 to 4% of the total mass of the hydrogel in a supersaturated state.

5. The sorptive heat exchanger (1) according to any one of claims 1 to 3, wherein the cell size of said honeycomb geometry ranges from 3 to 5 mm, with a vertical distance between cells not greater than half the cell size; the geometry is inserted between the two elements for heat transfer, constituting the repeating base of said sorptive heat exchanger.

6. An atmospheric water harvesting device (10) comprising at least one sorptive heat exchanger (1) according to any one of claims 1 to 5, so that said atmospheric water harvesting device (10) can provide fresh water in regions of the world where natural and / or economic water scarcity forces people to seek alternative solutions to access water.

7. A method for producing a sorptive heat exchanger (1) comprising the following steps: - step 100, preparation of a hygroscopic composite biopolymer (2) by means of a viscous gel containing a predetermined proportion of sodium alginate and calcium bentonite; - step 101, preparation of a heat exchange medium (4) having a honeycomb geometry and bringing it into contact with said hygroscopic composite biopolymer (2), - step 102, preparation of a hollow duct and bringing it into contact with said heat exchange medium (4), and - step 103, alternately entering a cooling fluid (6) or a heating fluid (8) into said hollow duct.

8. The method according to claim 7, wherein the viscous gel is prepared by mixing 2% by weight of sodium alginate and 4-10% by weight of calcium bentonite powder with deionized water until complete mixing and obtaining a homogeneous fluid.

9. The method according to claim 8, wherein said viscous gel is degassed under vacuum at a relative pressure of 200-500 mbar for at least 20 minutes.

10. The method according to claim 9, wherein said degassed viscous gel is injected into a preformed mold having a honeycomb geometry and said mold is deeply immersed in a deionized water / CaCl2 solution for at least 12 hours until complete gelation.

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