Directly associated with the Walipini idea is the geo-thermal or earth battery concept. The University of Minnesota gives away a free design manual. They want your contact information as this is an ongoing project/study. Their design buries about a 100 ton pile of rock and they run heat ducts through the rock pile to moderate temperature.

Here is another design: [link to www.youtube.com (secure)] (7.2 minutes - part of a series)