Rethinking cooling technology with thermogalvanic cells
Research supported by the National Natural Science Foundation of China and the China National Postdoctoral Program for Innovative Talents details a more efficient and environmentally friendly method of cooling based on thermogalvanic cells that is scalable from wearable devices to industrial grade refrigeration.
The new cooling technology described in a paper uses reversible electrochemical reactions involving iron ions to produce the cooling effect. Cooling using thermogalvanic cells is cheaper and more environmentally friendly than other methods as it uses a much lower energy input.
“Thermogalvanic technology is on its way to our lives, either in the form of clean electricity or low-power cooling, and both research and commercial communities should be paying attention,” says senior author Jiangjiang Duan of Huazhong University of Science and Technology in Wuhan, China.
Thermogalvanic cells use heat produced by reversible electrochemical reactions to create electrical power. Reversing this process by applying an external electrical current to drive electrochemical reactions generates cooling. Previous studies have shown that thermogalvanic cells have a limited potential to produce cooling. However, Duan’s team was able to significantly boost this potential by optimising the chemicals used in the technology.
“While previous studies mostly focus on original system design and numerical simulation, we report a rational and universal design strategy of thermogalvanic electrolytes, enabling a record-high cooling performance that is potentially available for practical application,” says Duan.
The researchers used thermodynamic cells based on electrochemical redox reactions involving dissolved iron ions. In one phase of the reaction, iron ions lose an electron and absorb heat (Fe3+ → Fe2+), and in the other phase, they gain an electron and release heat (Fe2+ → Fe3+). The power produced by the first reaction cools the surrounding electrolyte solution, while the heat produced by the first reaction is removed by a heat sink.
By tweaking the solutes and solvents used in the electrolyte solution, the researchers were able to improve the hydrogalvanic cell’s ability to cool. They used a hydrated iron salt containing perchlorate, which helped the iron ions dissolve and dissociate more freely compared to other previously tested iron-containing salts such as ferricyanide. By dissolving the iron salts in a solvent containing nitriles rather than pure water, the researchers were able to improve the hydrogalvanic cell’s cooling power by 70%.
The optimized system was able to cool the surrounding electrolyte by 1.42 K, which is a big improvement compared to the 0.1 K cooling capacity reported by previously published thermogalvanic systems.
“Though our advanced electrolyte is commercially viable, further efforts in the system-level design, scalability, and stability are required to promote the practical application of this technology,” says Duan. “In the future, we aim to continuously improve the thermogalvanic cooling performance by exploring novel mechanisms and advanced materials. We are also attempting to develop diverse refrigerator prototypes towards potential application scenarios and are seeking to collaborate with innovation companies to promote commercialization of thermogalvanic technologies.”
Image: Prototype thermogalvanic refrigerator. Credit Yilin Zeng.
The research was supported by the National Natural Science Foundation of China and the China National Postdoctoral Program for Innovative Talents.
Paper: Joule, Zeng et al., “Solvation entropy engineering of thermogalvanic electrolytes for efficient electrochemical refrigeration” DOI https://doi.org/10.1016/j.joule.2025.101822
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