fantastic idea

ws9876

http://www.treehugger.com/clean-technology/breakthrough-grid-scale-renewable-energy-storage-battery-made-gravel.html#14449617462751&action=collapse_widget&id=0&data=

what do you think??

inetdog

I think that their Reciprocating Heat Pump/Engine is likely to be no better than existing Stirling Cycle designs which do not work in practical sizes and applications here on the earth's surface.

ws9876

They have  a working proto.