Using a roof mounted solar thermal collector as a heat source, and a geothermal loop as a heat sink, drive a thermoacoustic engine -- this is an engine which turns a temperature differential into sound energy.
Use the sound energy created here to drive a second thermoacoustic device; this being used
as a heat pump, so that it uses sound energy to create/maintain a temperature differential.
Use the thermoacoustic heat pump to move heat out of your house (or refrigerator or freezer) into the geothermal loop.
I don't know if this is more or less efficient than an absorbtion chiller, nor do I know if it would have a higher or lower up-front cost, but I do know that it can produce temperatures below the freezing point of water without needing to use a toxic refrigerant (ammonia), as an absorbtion chiller would.
As an added advantage (compared to the absorbtion chiller it might replace), the heat pump can be run using an electrically driven speaker, if the sun isn't shining to drive the "motor" part.
If we were to compare a electric speaker driven version of this, to a conventional (compression) heat pump, I'm quite certain that it would last longer, and require less maintenance, and be more energy efficient, and also avoid potentially harmful refrigerants. It might cost more up front, but that would balance out over time.