The new issue of JLC came yesterday and they have an article on Direct Exchange Geothermal Technology.
They don't use water for heat transfer, but directly burry, or put into wells, copper carrying the refigerant.
It list too companies ECR Tech, http://www.erctech.com, with EarthLink brand.
And American Geothermal, http://www.amgeo.com But all I could find on their web site was for industrial processing and heat recovery.
Anybody know anything about this? How long has it been around?