My personal focus is on eventually retireing to a place that has cheap land and lots of water, so I'm looking at snow country (thanks, Gary, at "built-it-solar").
That being said, I had done a study of my alternative-cooling options if I decided on living in hot country.
If the humidity is low, I was very impressed by the mist-evaporation at the top of a cooling tower, like the visitors center at Zion national park. A small PV panel would be enough to run the small water pump.
After the initial heavy insulation on walls/ceiling, double paned windows, complete surround awnings to shade the outer walls, and a PV fan ventilating the attic to keep the ceiling cool...here's my favorite options from "build-it-solar" ideas.
A solar chimney is a narrow and wide masonry fixture with a row of clay pipes running up it. The wide side is painted black and facing the afternoon sun. When air heats in the tubes, the hot air rises, pulling air through the house. If the house is sealed well, the house air can be drawn from geothermal trenches (obviously, a PV fan would help). This is where a row of air tubes go straight down to a gravel condensate trap about 10 feet deep. Then the tubes run in trenches across the property at a slight up angle (so condensate runs away from the house) the tubes then are joined and a pipe is routed to the house. Even in the hot desert, the soil is lower than 60 degrees when its 10 feet down.
I was concerned about funky smelling air, so personally, I'd want to route the incoming air through a couple of 18-wheeler Diesel turbo intercoolers that are spliced into the (insulated) central air ducting. An intercooler is a large aluminum air-to-air heat exchanger. This would keep the cool air-flow that is coming from the ground and going up the solar chimney separate from the circulating house air. If it doesn't flow quite well enough, a small PV fan could boost it.
If additional cooling was needed to get the house down to 75 degrees (a small lot can only have a few geothermal tubes, and although deep-drilling them works, it is very expensive) one option is to make up a couple of ammonia-absorption refrigeration units from junk. Set them side-by-side, and rig it so they alternate cycles. A small PV motor can rotate a shade that alternates putting one heater in the sun, and the other in the shade, with a linkage operating routing valves.
http://en.wikipedia.org/wiki/Absorption_refrigeration
Basically, its an aluminum radiator set in the back yard in the sun with reflectors, and is filled 3/4ths with half water/half ammonia. The ammonia boils out into a vapor (at a barely warm temp) and is routed through an insulated pipe into the top of the intercooler that is set above the central air ducting. A valve shuts, trapping the warm vapor, which is cooled by a PV fan. Then another valve opens, allowing the condensing vapor to pass down into the A/C intercooler that's inside the ducting. As the ammonia condenses it gets very cold, then trickles downhill to the bottom of the heater.
http://en.wikipedia.org/wiki/Icyball
Shaft seals wearing out in the valves and pumps, which can lead to ammonia leaks, can be avoided by using reciprocating magnets outside stainless steel pipes to actuate internal devices (Einstein patented this in the 1930's).
http://en.wikipedia.org/wiki/Einstein_refrigerator
If you are still concerned, a small part of the central air ducting can be routed outside the house to cool the ducted air, and it would be easy to custom braze an aluminum tube condenser where the ammonia seals are on the tube ends and the ducting seals are slightly nearer the center of the turbes so ammonia leaks couldn't get into the ducting, but would vent to the outside air.
Also, the big "Watt-hog" in an A/C system is the Freon compressor. A "Butane-vapor" engine can be made from two radiators, one sitting in the sun with reflectors, and one up high in the shade, possibly with a fan. It operates like an unusually simple steam engine, using a one-piston A/C compressor. I know butane is flammable, but the system is small, completely sealed, the butane part doesn't use electricity, and I'm not concerned about having gasoline in the lawnmower in my garage either.
A central A/C condenser (the radiator with a fan in the back yard) can have the 110 VAC motor removed, and the shaft for fan extended up the side of the house to the roof (on the backside not visible from the street) and a combination VAWT and small PV panel powering a DC motor sharing the same vertical shaft. Or, you could just put the whole thing on the patio roof with a short fence around it to hide it. Just a few ideas to kick around. -Ron
"give a man a fish, and he'll be fed for a day,...but teach him to fish, and his wife will never see him again"
"build a politician a fire, and he'll be warm for a night,...but set him on fire, and he'll be warm for the rest of his life"
