Cooling my A/C condenser

[NiHaoMike]

Try painting the roof white (or at least a light color) if you can. Also shade windows letting in direct sunlight.

The idea of a "hybrid" A/C is a great one but converting a regular one isn't going to work well since it's not designed for such low condensing temperatures. Done properly, however, it would work very well indeed. My friend Brittany Benzaia developed a hybrid A/C that uses a switched reluctance centrifugal compressor so it can use water as a refrigerant. (There's a sealed loop as well as an open loop.) The fact that the compressor is free flowing when off means that "bypass mode" (evaporative cooler only) is done by switching off the compressor, and there's almost no transition between bypass and normal mode. She claims that in Arizona (very hot and dry for those who don't know), it gets the equivalent of 40 SEER.

As an aside, A/Cs originally used toxic chemicals like methylene chloride and ammonia. Because of the obvious safety issues, they found that CFCs were safer alternatives. Then came the ozone depletion problem and they went to HFCs. Then they claim that HFCs cause global warming, so now they're trying to find further alternatives. (The issue with HFCs in air conditioning is moot when aerosol products put orders of magnitude more HFCs into the atmosphere than leaky A/C equipment.) Water (R718) makes a great refrigerant for air conditioning, except its low vapor pressure calls for a high volume flow rate at a given capacity. Direct off line induction motors are limited to 3600 or 3000 RPM, meaning the compressor would need to be impractically large to get a useful capacity. Inverter driven switched reluctance motors (or any inverter driven motor for that matter) are not subject to that limitation and can operate at very high speeds. The compressor in the hybrid A/C can rev as high as 100kRPMs or more if it needs to.