Solar powered below-ground sand bed air conditioner

[txlibdem]

I've seen the commercial systems that are on the market and they're all out of my price range (which is basically zero). So I have been wondering if one could use a below-ground sand bed in the summer to store the cold, sort of the reverse of those systems designed to provide heat in winter. I'd have to be able to do it myself due to budget issues.

Here is an illustration of how a sand bed heat system might work:
http://static.mgnetwork.com/rtd/pdfs/20110308_solar.pdf
...pretty simple, just two loops of pex tubing (very common). One from the solar water heater that circles around inside the sand to heat it up, another completely separate loop which takes the heat from the sand and circulates it through a radiant floor heating system.

My thought was that in summer that whole setup would be useless where I am. But if I setup a third loop of pex or copper tubing that snakes around in the sand but is connected to an external freezer unit, loops inside the freezer to cool the antifreeze solution then the sand as it circulates around. The power to run the freezer would come from a couple of solar panels (haven't done the math to determine exactly how many it would take). Then a separate set of tubing, PVC 4" maybe, would loop inside the sand bed and fans would blow the cooled air into the house.

Since the house is already very well insulated and caulked I'm not worried about losses too much.

PS, I don't have radiant heating, that was just in the illustration I found so I'd be using the PVC 4" in the winter also as a backup heat source (already get plenty of solar heat gain when we open south-facing windows).

Any thoughts?