If you have access to a solar pond, the best way to utilize its storage capabilty is to use a water source heat pump. There has been a discussion concerning the Minton water wheel and its large scale practical use...I think the "Mother Earth News" had the best summation: It just doesn't work. However, low grade heat can be used if a heat pump is involved. The typical COPs for ground source systems are 4, and a water source design would be even higher. This means that for every $1 in energy you buy (or generate) you get at least $4 worth of heat energy out of the pond. This energy can be used for space heating, domestic water heating, etc. As an air-conditioning system, it would be just about as efficient as they get, with a SEER of 14 or more.
These systems are not cheap, but compared to building a 40' steel wheel and buying a couple of thousand pounds of refrigerant, they might look pretty good.
Pat
