Another option would be a solar-assisted heatpump system. You can make individial heat-exchanger panels with 4'x 8' sheets of 1/32" steel. Tack weld a bunch of washers onto the face of one sheet and then tack-weld the second sheet on top of those. The washers are in the middle of the "sandwitch". Then weld a couple of tubing inlet/outlets on opposite corners of one face. Then weld up the outer edges so the two sheets form a sealed hollow space. The washers are spacers to keep the sheets from getting squashed together.

Paint the whole thing flat black and put it on the roof. Then circulate glycol solution through it.

The glycol solution is circulated down from the panel and through the evaporator on the heatpump.

With solar assist, a heatpump can collect up to 12kw of heat for every 1kw used to drive the compressor. That's based on something like the new "eco-refrigerant" R12 replacement, not 134a(toxic, poor refrigerant).

The more panels you put up and connect in series, the larger your collector surface, the more efficient the system becomes.

In the summer-time, drop the panels down into the shade and circulate the glycol through the condenser to dump heat outside.

(Allen County-WANE-October 1, 2004) With heating costs expected to be expensive again this winter, many people are looking for cheaper heating alternatives.

While it's not commonly known, one alternative has been around for 60 years. It's Geothermal Heating and Cooling, and it has been picking up in popularity.

The geothermal system uses plastic pipes submerged to the bottom of a pond to collect the Earth's natural heat. The system then transfers that head through the pipes to the connected building.

One of the largest ponds in northern Indiana used for the service could offer a 600 ton heating and cooling capacity. That could result in great savings for consumers.

Autoliv, a company providing Geothermal energy, couldn't give specific savings statistics, but did says a 2,500 square-foot home would pay $1,000 annually for natural gas, while the same home would pay $500 for geothermal energy.

The equipment used for geothermal energy is, however, more expensive than conventional heating. Equipment typical costs $1,500 to $2,000 more, making the savings come after a long-term investment.

http://www.wane.com/Global/story.asp?S=2376284&nav=0RYbRXki"

 From what i understand you need some 300 feet of tubing buried approx 7 feet is a back and forward motion under your yard/lawn. This combined with a solar heater and smart heat exchager will suffice.