Direct thermal charging cell for converting low-grade heat to electricity

Xun Wang; Yu-Ting Huang; Chang Liu; Kaiyu Mu; Ka Ho Li; Sijia Wang; Yuan Yang; Lei Wang; Chia-Hung Su; Shien-Ping Feng

doi:10.1038/s41467-019-12144-2

Direct thermal charging cell for converting low-grade heat to electricity

Nat Commun. 2019 Sep 12;10(1):4151. doi: 10.1038/s41467-019-12144-2.

Authors

Xun Wang¹, Yu-Ting Huang¹, Chang Liu¹, Kaiyu Mu¹, Ka Ho Li¹, Sijia Wang¹, Yuan Yang², Lei Wang¹, Chia-Hung Su³, Shien-Ping Feng^{4

5}

Affiliations

¹ Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
² Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA.
³ Department of Chemical Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan.
⁴ Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China. hpfeng@hku.hk.
⁵ The University of Hong Kong-Zhejiang Institute of Research and Innovation (HKU-ZIRI), Hangzhou, 311300, Zhejiang, China. hpfeng@hku.hk.

Abstract

Efficient low-grade heat recovery can help to reduce greenhouse gas emission as over 70% of primary energy input is wasted as heat, but current technologies to fulfill the heat-to-electricity conversion are still far from optimum. Here we report a direct thermal charging cell, using asymmetric electrodes of a graphene oxide/platinum nanoparticles cathode and a polyaniline anode in Fe²⁺/Fe³⁺ redox electrolyte via isothermal heating operation. When heated, the cell generates voltage via a temperature-induced pseudocapacitive effect of graphene oxide and a thermogalvanic effect of Fe²⁺/Fe³⁺, and then discharges continuously by oxidizing polyaniline and reducing Fe³⁺ under isothermal heating till Fe³⁺ depletion. The cell can be self-regenerated when cooled down. Direct thermal charging cells attain a temperature coefficient of 5.0 mV K^-1 and heat-to-electricity conversion efficiency of 2.8% at 70 °C (21.4% of Carnot efficiency) and 3.52% at 90 °C (19.7% of Carnot efficiency), outperforming other thermoelectrochemical and thermoelectric systems.