# US 12,759,901 B2 · Passive freezing desalination driven by radiative cooling > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,759,901 B2 - Document ID: US12759901B2 - Status: Granted - Kind: B2 - Application number: 18/847,640 - Filed: 2023-04-27 - Published: 2025-02-06 - Granted: 2026-10-13 - Earliest claimed: 2022-04-27 - Assignees: The Regents of the University of California - Applicants: The Regents of the University of California - Inventors: Xin Huang; Aaswath Pattabhi Raman; Jyotirmoy Mandal - Web page: https://patentgrep.com/patent/US12759901B2 ## CPC - C02F 1/22: by freezing - C02F 1/14: using solar energy - C02F 2103/08: Seawater, e.g. for desalination - C02F 2201/009: Apparatus with independent power supply, e.g. solar cells, windpower or fuel cells - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) ## Abstract Radiative cooling enabled passive freezing desalination processes are described. High salinity water can be desalinated via radiative cooling-driven freezing desalination. The passive freezing desalination processes can be a complementary method to solar desalination to enable 24-hour, year round passive thermal desalination. ## Claims ### Claim 1 A method for desalination comprising: contacting a water source with a radiative cooling surface, wherein the radiative cooling surface faces outwardly to an atmosphere; wherein the radiative cooling surface comprises a thermal emitter with an emissivity from 0.5 to 1 at an electromagnetic wavelength range from 8 μm to 13 μm; freezing the water source via radiative cooling to form ice and brine; wherein the radiative cooling transfers heat from the water source to the atmosphere via the radiative cooling surface; and obtaining desalinated water by thawing the ice, wherein the desalinated water has a salinity lower than the water source. ### Claim 2 (depends on 1) The method of claim 1, further comprising washing the ice with a low salinity water. ### Claim 3 (depends on 2) The method of claim 2, further comprising sweating the ice under a temperature gradient. ### Claim 4 (depends on 1) The method of claim 1, further comprising adding at least one ice seed to the water source before freezing. ### Claim 5 (depends on 1) The method of claim 1, further comprising separating the ice from the brine. ### Claim 6 (depends on 1) The method of claim 1, wherein the desalination is combined with a solar desalination process. ### Claim 7 A desalination system comprising: a water source; a radiative cooling surface in contact with the water source; wherein the radiative cooling surface faces outwardly to an atmosphere, and is configured to transfer heat from the water source to the atmosphere and to freeze the water source; wherein the radiative cooling surface comprises a thermal emitter with an emissivity from 0.5 to 1 at an electromagnetic wavelength range from 8 μm to 13 μm; and a collecting system configured to collect ice from the frozen water source, wherein the ice comprises desalinated water. ### Claim 8 (depends on 7) The system of claim 7, wherein the water source is selected from the group consisting of: brackish water, saline water, seawater, salt water, and any combinations thereof. ### Claim 9 (depends on 7) The system of claim 7, wherein the water source has a salinity greater than or equal to 35‰. ### Claim 10 (depends on 7) The system of claim 7, wherein the water source comprises at least one ice seed. ### Claim 11 (depends on 7) The system of claim 7, further comprising a separation system to separate ice and brine from the frozen water source. ### Claim 12 (depends on 11) The system of claim 11, wherein the separation system comprises a filter. ### Claim 13 (depends on 7) The system of claim 7, wherein the collecting system comprises a hydrophilic surface to improve ice collection efficiency. ### Claim 14 (depends on 7) The system of claim 7, wherein the thermal emitter comprises a material selected from the group consisting of: an acrylic polymer, indium tin oxide, aluminum oxide, hafnium oxide, and any combinations thereof. ### Claim 15 (depends on 7) The system of claim 7, wherein the radiative cooling surface is insulated with at least one material to minimize a thermal emittance. ### Claim 16 (depends on 15) The system of claim 15, wherein the at least one material is selected from the group consisting of: polyurethane, polyurethane foam, polystyrene, cellulose, mylar, low density polyethylene, high density polyethylene, polyester, polyisocyanurate, fiberglass, wool, reflective foil, natural fiber, and any combinations thereof. ### Claim 17 (depends on 16) The system of claim 16, wherein the at least one material comprises a double-layer low density polyethylene. ### Claim 18 (depends on 7) The system of claim 7, wherein the desalinated water has a salinity of less than 35‰. ### Claim 19 (depends on 7) The system of claim 7, wherein the desalinated water is used as the water source for the desalination system. ### Claim 20 A hybrid desalination system comprising: a desalination system comprising: a water source; a radiative cooling surface in contact with the water source; wherein the radiative cooling surface faces outwardly to an atmosphere, and is configured to transfer heat from the water source to the atmosphere and to freeze the water source; wherein the radiative cooling surface comprises a selective thermal emitter with an emissivity from 0.5 to 1 at an electromagnetic wavelength range from 8 μm to 13 μm, and an emissivity from 0.5 to 1 at an electromagnetic wavelength range from 0.3 μm to 2.5 μm; and a collecting system configured to collect ice from the frozen water source, wherein the ice comprises desalinated water; and a solar thermal desalination system; wherein the solar thermal desalination system desalinates during daytime and the desalination system desalinates during nighttime.