I noticed this company Clean Energy Technology has this

Clean Cycle Generator

Intelligent Energy Production
Heat is just another form of energy, and it is frequently released out the stacks of industrial facilities, power plants, compression stations, and many other facilities.

Our technology converts heat from a variety of sources into clean, affordable electricity, which can be either sold back to the grid, or offset electrical costs.

Wondering if anyone has tried converting the heat output back to more usable energy? Seems like yields could go decently up?

Info on the generator: http://cetyinc.com/products-and-solutions/