Efficient Low-Grade Heat Harvesting Enabled by Tuning the Hydration Entropy in an Electrochemical System.
Harvesting of low-grade heat (<100 °C) is promising, but its application is hampered by a lack of efficient and low-cost systems. The thermally regenerative electrochemical cycle (TREC) is a potential alternative system with high energy-conversion efficiency. Here, the temperature coefficient (α), which is a key factor in a TREC, is studied by tuning the hydration entropy of the electrochemical reaction. The change of α in copper hexacyanoferrate (CuHCFe) with intercalation of different monovalent cations (Na+ , K+ , Rb+ , and Cs+ ) and a larger α value of -1.004 mV K-1 being found in the Rb+ system are observed. With a view to practical application, a full cell is constructed for low-grade heat harvesting. The resultant ηe is 4.34% when TREC operates between 10 and 50 °C, which further reaches 6.21% when 50% heat recuperation is considered. This efficiency equals to 50% of the Carnot efficiency, which is thought to be the highest ηe reported for low-grade heat harvesting systems. This study provides a fundamental understanding of the mechanisms governing the TREC, and the demonstrated efficient system paves the way for low-grade heat harvesting.
['Gao|Caitian|C|https://orcid.org/0000-0003-3693-983X', 'Liu|Yezhou|Y|', 'Chen|Bingbing|B|', 'Yun|Jeonghun|J|', 'Feng|Erxi|E|', 'Kim|Yeongae|Y|', 'Kim|Moobum|M|', 'Choi|Ahreum|A|', 'Lee|Hyun-Wook|HW|https://orcid.org/0000-0001-9074-1619', 'Lee|Seok Woo|SW|https://orcid.org/0000-0003-2459-7174']
low-grade heat harvesting hydration entropy thermally regenerative electrochemical cycle monovalent cations energy conversion efficiency