Materials and System Design for Thermally Regenerative Electrochemical Cycle for Low-grade Heat Harvesting

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Professor Gang Chen
Department of Mechanical Engineering, MIT
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Professor Yi Cui
Stanford University
Seok Woo Lee
Stanford University
Yuan Yang
Department of Mechanical Engineering, MIT
Hadi Ghasemi
Department of Mechanical Engineering, MIT
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Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Electromechanical Systems and Methods for Harvesting Heat Energy

US Patent 9,559,388
An electrochemical system for efficiently harvesting low-grade heat energy
Nature Communications , May 21, 2014
A new way to harness waste heat
MIT News, May 21, 2014


  • Harvesting waste heat
  • Renewable thermal energy
  • Off-grid energy generation in remote areas

Problem Addressed

Vast amounts of low-grade heat  are wasted in the industrial processes of solar-thermal and geothermal energy production. It is generally difficult to convert such low temperature thermal energy into electricity due to the distributed nature of the heat source and low temperature differential.


This invention encompasses a charging-free electrochemical cell for harvesting low-grade heat. The cell consists of a Fe(CN)63-/4- positive electrode and a solid Prussian blue nanoparticle negative electrode. The cell is first discharged at room temperature. When the entire cell is heated, the voltage decreases to less than zero due to the negative thermogalvanic coefficient of the full cell. In the subsequent reverse process at high temperature, which is spontaneous, the cell is discharged again as the absolute value of voltage decreases. Thus, the two discharge processes at different temperatures, fueled by low grade heat, can be cycled without charging and can provide an alternating current to a load. 


  • Reasonable cycling performance
  • Efficiency is about an order of magnitude higher than previous studies on galvanic cells
  • Simplifies thermally regenerative electrochemical system design
  • Reduced cost