This idea is 3/4 baked, since people are in fact working on it, but it would be really nice if there a wide variety of small sizes of absorbtion chillers/absorbtion heat pumps, appropriate for domestic cooling and heating.
It would be very nice to be able to heat one's home by using a solar thermal loop as the high temperature input of an absorbtion heat pump, a geothermal loop as the low temperature heat input, and the home's interior as the heat output. This allows the solar panels to be much smaller than they would need to be if they were warming the house by themselves. It also uses much less energy than geothermal and a compression based heat pump.
Similarly, it would be nice to cool one's home by using a solar thermal loop as the high temperature input of an absorbtion heat pump, a geothermal loop as the heat sink, and one's home's interior as the heat source. It's much less unsightly (and probably more energy efficient) to send waste heat into the ground than into a cooling tower, and as I already said, it uses much less energy than geothermal with a compression type heat pump.
The reason why such geosolarthermal heating/cooling systems aren't common is because there are very very few absorbtion heat pumps sized and priced properly for home use.
(To get heating and cooling when the sun isn't shining, one can either store the heat of the sun somehow, or else use combustion -- perhaps in the form of a micro CHP system -- to provide the heat. Curiously, some CHP systems come with an absorbtion chiller so they can provide cooling, but they don't use it to amplify their heating capacity.)-- goldbb, Feb 24 2009random, halfbakery