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EP-4739500-A1 - ATMOSPHERIC-MOISTURE-INDUCED POLYACRYLATE HYDROGEL SYSTEM AND METHOD FOR PASSIVE COOLING

EP4739500A1EP 4739500 A1EP4739500 A1EP 4739500A1EP-4739500-A1

Abstract

A photonic hydrogel film (300) includes a substrate (602) and a hybrid cooling layer (304) attached to the substrate (602) and including a sodium polyacrylate (PAAS) material (308) forming a continuous film structure. The PAAS material (308) is hydrated by atmospheric water molecules so that chains of the PAAS material (308) are uncoiled for maintaining the continuous film structure. The PAAS material simultaneously reflects sunlight due to a porous structure and emits infrared radiation due to molecular vibrations of the chains of the PAAS material.

Inventors

  • GAN, QIAOQIANG

Assignees

  • King Abdullah University of Science and Technology

Dates

Publication Date
20260513
Application Date
20240703

Claims (20)

  1. 1 . A photonic hydrogel film (300) comprising: a substrate (602); and a hybrid cooling layer (304) attached to the substrate (602) and including a sodium polyacrylate (PAAS) material (308) forming a continuous film structure, wherein the PAAS material (308) is hydrated by atmospheric water molecules so that chains of the PAAS material (308) are uncoiled for maintaining the continuous film structure, and wherein the PAAS material simultaneously reflects sunlight due to a porous structure and emits infrared radiation due to molecular vibrations of the chains of the PAAS material.
  2. 2. The film of Claim 1 , wherein a mass of the atmospheric water molecules relative to a mass of the PAAS material is between 0.5 to 0.8 g/g for a thickness of 2 to 3 mm.
  3. 3. The film of Claim 1 , wherein the hybrid cooling layer further includes AN.
  4. 4. The film of Claim 3, wherein a mass ratio between the PAAS and AN is about 1 :1 .
  5. 5. The film of Claim 1 , further comprising: a functional layer covering the hybrid cooling layer, wherein the functional layer protects the hybrid cooling layer from excessive water.
  6. 6. The film of Claim 5, wherein the functional layer includes a melamine layer coated with polydimethylsiloxane (PDMS).
  7. 7. The film of Claim 1 , wherein the substrate includes one of wood, metal or plastic.
  8. 8. The film of Claim 1 , further comprising: an adhesive layer located between the substrate and the hybrid cooling layer.
  9. 9. The film of Claim 1 , wherein the hybrid cooling layer is configured to lower a temperature behind the film, relative to an ambient temperature, with no electricity consumption.
  10. 10. A method for cooling a structure, the method comprising: placing (1500) a photonic hydrogel film (300) on a structure (603), wherein the photonic hydrogel film (300) includes a sodium polyacrylate (PAAS) material (308) forming a continuous film structure; hydrating (1502) the photonic hydrogel film (300) with atmospheric water molecules during night; and exposing (1504) to sunlight the photonic hydrogel film (300) during day so that the PAAS material (308) is hydrated by atmospheric water molecules so that chains of the PAAS material (308) are uncoiled for maintaining the continuous film structure, and the PAAS material simultaneously reflects the sunlight due to a porous structure and emits infrared radiation due to molecular vibrations of the chains of the PAAS material.
  11. 11. The method of Claim 10, wherein the photonic hydrogel film includes a substrate (602) and a hybrid cooling layer (304) attached to the substrate (602), the hybrid cooling layer including the PAAS material.
  12. 12. The method of Claim 10, wherein a mass of the atmospheric water molecules relative to a mass of the PAAS material is between 0.5 to 0.8 g/g for a thickness of 2 to 3 mm.
  13. 13. The method of Claim 11 , wherein the hybrid cooling layer further includes AN.
  14. 14. The method of Claim 13, wherein a mass ratio between the PAAS and AN is about 1 :1 .
  15. 15. The method of Claim 11 , wherein the substrate includes one of wood, metal or plastic.
  16. 16. A construction material (600) to be attached to a structure (603) for passively lowering a temperature of the structure (603), the construction material (600) comprising: a substrate (602); and a hybrid cooling layer (304) attached to the substrate (602) and including a sodium polyacrylate (PAAS) material (308) forming a continuous film structure, wherein the PAAS material (308) is hydrated by atmospheric water molecules so that chains of the PAAS material (308) are uncoiled for maintaining the continuous film structure, and wherein the PAAS material simultaneously reflects sunlight due to a porous structure and emits infrared radiation due to molecular vibrations of the chains of the PAAS material.
  17. 17. The construction material of Claim 16, wherein a mass of the atmospheric water molecules relative to a mass of the PAAS material is between 0.5 to 0.8 g/g for a thickness of 2 to 3 mm.
  18. 18. The construction material of Claim 16, wherein the hybrid cooling layer further includes AN.
  19. 19. The construction material of Claim 18, wherein a mass ratio between the PAAS and AN is about 1 :1.
  20. 20. The construction material of Claim 16, further comprising: a functional layer covering the hybrid cooling layer, wherein the functional layer protects the hybrid cooling layer from excessive water, wherein the functional layer includes a melamine layer coated with polydimethylsiloxane (PDMS), and wherein the substrate includes one of wood, metal or plastic.

Description

ATMOSPHERIC-MOISTURE-INDUCED POLYACRYLATE HYDROGEL SYSTEM AND METHOD FOR PASSIVE COOLING CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 63/524,948, filed on July 5, 2023, entitled “ATMOSPHERIC-MOISTURE- INDUCED POLYACRYLATE HYDROGELS FOR HYBRID PASSIVE COOLING,” the disclosure of which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION TECHNICAL FIELD [0002] Embodiments of the subject matter disclosed herein generally relate to a system and method for passive cooling, and more particularly, to a polyacrylate- based material that exhibits high solar reflectance, thus reducing solar heating, and high mid-infrared emittance, thus maximizing thermal emission. DISCUSSION OF THE BACKGROUND [0003] Climate change has brought high temperatures to many regions of the globe for longer periods. As a result, rapidly increasing energy demands, in part from air conditioning systems, are overloading the existing energy grids. Energy consumption and associated environmental issues due to compressor-based cooling techniques amplify the need to explore energy-free passive cooling approaches. The natural process of evaporation, condensation, precipitation, and percolation, known as the “water cycle,” delineates the continuous water movement between the Earth and the atmosphere in three phases. Mainly, a large amount of energy is absorbed during water evaporation (e.g., 2,430 kJ kg'1 at 30°C). Therefore, it is possible to use this process for cooling, i.e., evaporating water to absorb ambient heat passively. However, continuous evaporative cooling requires an external water supply, limiting its widespread use in areas with limited water sources. Global atmospheric vapor is estimated at about 12,900 km3 and is considered a ubiquitous water resource. Moreover, rising ambient temperatures cause an increase in atmospheric moisture, amplifying the warming effect of greenhouse gases such as moisture (moisture is the most significant component of greenhouse gases and even more challenging to control than carbon dioxide). Therefore, utilizing atmospheric moisture effectively could create a solution to address the challenge of global warming. [0004] One approach to passive cooling is the use of desiccant materials. These materials, including silica gel, zeolites, hygroscopic hydrogel [1], metal- organic-frameworks, and lithium chloride [2], have been extensively studied for their ability to absorb vapor from humid atmospheres during the nighttime and evaporate it during the daytime, meeting water harvesting needs [3]. The hygroscopic hydrogel, in particular, has been developed for various applications, including atmospheric water harvesting [4], evaporative cooling [5], and interfacial solar evaporation [6, 7], Its high affinity for water absorption and relatively low temperature-activated desorption process (~ 30°C) make it a promising material. Additionally, the inherent molecular vibrations of chemical bonds over infrared wavelengths (5 - 25 pm) give the hygroscopic hydrogels high thermal emittance, enabling effective heat dissipation through radiative cooling. [0005] Recently, bilayer structures with polymer fibrous networks atop a hygroscopic hydrogel underlayer have been evaluated to integrate radiative and evaporative cooling [8]. Currently, used hygroscopic hydrogels include a hygroscopic matrix and a moisture absorption enhancer. The hygroscopic matrix includes poly(N- isopropyl acrylamide) (pNIPAM), Polyvinyl alcohol (PVA), or polyacrylamide (PAM), while the moisture absorption enhancer includes LiCI and LiBr salts for enhanced cooling performance. However, these hydrogel layers require a complex synthesis process, which increases the fabrication cost and hinders its extensive engineering implementations. Specifically, fabricating poly (vinyl alcohol)-CaCl2 hydrogel involves time-sensitive and labor-intensive processes such as gelation, freeze-drying, and moisture-absorbent loading. These processes contribute to positive carbon emissions and exacerbate global warming. [0006] Thus, there is a need for a new material and a “green” fabrication process of this new material, with no carbon emissions, to further promote and advance the passive cooling technique. SUMMARY OF THE INVENTION [0007] According to an embodiment, there is a photonic hydrogel film that includes a substrate and a hybrid cooling layer attached to the substrate and including a sodium polyacrylate (PAAS) material forming a continuous film structure. The PAAS material is hydrated by atmospheric water molecules so that chains of the PAAS material are uncoiled for maintaining the continuous film structure. The PAAS material simultaneously reflects sunlight due to a porous structure and emits infrared radiation due to molecular vibrations of the chains of the PAAS material. [0008] According to another embodiment, there is a method for cooling a structure and