I found a brilliant solar heating design called Annualized Geo Solar online. It uses solar air collectors (or even a metal roof surface) and pumps the air via air tubes into a partially insulated and waterproofed soil mass beneath the house (about 8 or so feet beneath the uninsulated concrete floor slab. It also required the house to be super-insulated. You run the system during the summer months and because of the distance between the "heat deposit tubes" and the concrete floor slab, there is a heat lag where the heat reaches the house in about 6 months.
Here are a couple links:
Website of Architect who developed AGS
In depth PDF paper