There is also a couple of sections on ground loop heat pumps in the book "Sustainable Energy - without the hot air" by David MacKay: http://www.withouthotair.c

There is also a couple of sections on ground loop heat pumps in the book "Sustainable Energy - without the hot air" by David MacKay: http://www.withouthotair.com/c21/page_152.shtml http://www.withouthotair.com/c21/page_152.shtml