Thermosensitive crystallization–boosted liquid thermocells for low-grade heat harvesting

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Science  16 Oct 2020:
Vol. 370, Issue 6514, pp. 342-346
DOI: 10.1126/science.abd6749

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Recovering low-temperature heat

Low-temperature heat sources are both abundant and largely dissipated into the environment. Yu et al. discovered a way to boost the concentration gradient in a liquid thermogalvanic cell that allows low-temperature heat to be recovered. The authors added a component that boosts the concentration gradient by forcing crystallization of the electrolyte at the cold end, and these crystals then melt at the hot end. This process boosts efficiency and is a potential method for recovering low-grade heat.

Science, this issue p. 342


Low-grade heat (below 373 kelvin) is abundant and ubiquitous but is mostly wasted because present recovery technologies are not cost-effective. The liquid-state thermocell (LTC), an inexpensive and scalable thermoelectric device, may be commercially viable for harvesting low-grade heat energy if its Carnot-relative efficiency (ηr) reaches ~5%, which is a challenging metric to achieve experimentally. We used a thermosensitive crystallization and dissolution process to induce a persistent concentration gradient of redox ions, a highly enhanced Seebeck coefficient (~3.73 millivolts per kelvin), and suppressed thermal conductivity in LTCs. As a result, we achieved a high ηr of 11.1% for LTCs near room temperature. Our device demonstration offers promise for cost-effective low-grade heat harvesting.

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