You reminded me of Lonnie Johnson's "Johnson Thermo-Electrochemical Convertor", or JTEC for short. On their webpage they say they are aiming for 85% Carnot effi

You reminded me of Lonnie Johnson's "Johnson Thermo-Electrochemical Convertor", or JTEC for short. On their webpage they say they are aiming for 85% Carnot efficiency for converting heat to electricity, and it can run in reverse to become a heat pump[0][1]. Sadly, I can find no third-party measurements of how well it performs in practice, so I guess it's still in the R&D phase. I did find a nice talk by Johnson about the project though[2]. [0] http://www.johnsonems.com/about/ http://www.johnsonems.com/about/ [1] http://www.johnsonems.com/benefits/ http://www.johnsonems.com/benefits/ [2] https://www.youtube.com/watch?v=F6FUk2E9-68 https://www.youtube.com/watch?v=F6FUk2E9-68