Here’s a 200 year old idea with merit: A Stirling engine, modified to capture the waste heat of industrial processes to make electricity. Gar noted Stirling Energy Systems’ efforts in this vein to make electricity from solar thermal collectors using a Stirling engine a year ago, but instead of the sun, a startup in my neighborhood, ReGen, is developing a Stirling that will specialize in using the low to moderate heat generated by landfill gas systems, paper mills, steel mills, chemical and petroleum refining facilities, glass ovens, cement plants, and similar locations:

The Stirling engine, which once powered tractors and fell into disuse when the internal combustion engine came into vogue, uses an external heat source, such as waste heat. Its high efficiency comes from using a heat exchanger to cool the hot expanded gas while retaining some of that heat to power the next cycle, according to Conde. The heat recovered in the cooling cycle then can be recycled.

Converting low-temperature industrial waste heat to industrial-scale power represents a multi-billion dollar market opportunity that is currently not addressed by commercially available technologies…

How this differs from Recycled Energy Development’s technology for turning waste heat into electricity I do not know, maybe it’s similar, but I bet Sean Casten can say.