2012-11-03 Upgrade in process
Objective - Indoor AP System - 75-85 degrees 24/7
Tank to sit on 12 inches of sand and have about 10" of sand contained in a secondary shell around the tank. The sides and top to be insulated with 2 inch foam sheeting. Maintenance access via swing up door, hinged at the level of the tank top edge.
I expect the water temperature to be maintained passively to the degree practical. Heat when needed from a black pipe coil collector. Chilling when needed from accelerated evaporation.
2012-11-10 update My calculations indicate that the mass of the sand will be 16000 lbs plus the water 5845 lbs for a total mass of 21,845 lbs. I am expecting a temperature differential of 10-12 degrees Mean daily OAT to tank temp.
That should reduce the heating and cooling load significantly, perhaps to passive control levels.
2012-11-11 Another change - I am going to embed a 200 ft. 1/2 in. plastic tubing loop in the sand terminated outside the dome. The tubing will connect to a plastic tube solar collector via a thermostat controlled valve to capture available heat when needed.