We've written many times on solar PV electricity, the most common form of homeowner solar. We've also written about solar thermal hot water heating. But another method for utilizing solar to reduce your energy bill is solar powered air conditioning!
Solar powered air conditioning works on the absorption cycle. From wikipedia on absorption refrigerator:
An absorption refrigerator is a refrigerator that uses a heat source (e.g., solar, kerosene-fueled flame) to provide the energy needed to drive the cooling system. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where noise from the compressor is problematic, or where surplus heat is available (e.g., from turbine exhausts or industrial processes, or from solar plants).
I'm still trying to wrap my head around the absorption process, but the main idea is that energy is supplied to a refrigeration process by a heat source, not a electricity powered compressor, like what is used in a traditional air conditioner. Oh yea, there's also a thing called an absorber.
Mother Earth News has a great article on solar powered heat pump which uses absorption (keep in mind the article was written in 1984). Of course a heat pump can perform heating and cooling, but the principles of a solar powered heat pump are the same for a solar powered AC unit.
For obvious reasons, the absorption cycle lends itself well to solar-thermal energy. Converting the heat output of a solar panel into rotating motion (to spin a compressor) would be a complicated and expensive procedure; an absorption-cycle heat pump, however, has no moving parts and requires only heat at fairly low temperatures to operate. Technicians have been working on solar-driven absorption-cycle heat pumps for over a decade, but the hang-up has been that the best COP's have only been about 0.7, requiring a singledwelling collector area of 600 to 700 square feet . . . a prohibitive amount.
And in describing how the energy yield of different heating methods breaks down:
In terms of energy delivered compared with energy consumed, a conventional compressor-driven heat pump takes 100 Btu from a power plant and yields 164 Btu into a home when the outdoor temperature is 37°F. (In comparison, a resistance heater delivers 35 Btu at the same expense of energy.) Dao's single-effect heat pump, however, could yield 237 Btu at the same outside temperature.
GasAirConditioning.org has a nice explanation of how absorption cooling works, and they also have a pretty good schematic:
In a solar powered air conditioner, parabolic troughs collect the sun's energy to heat a fluid. This fluid is then sent to the generator, which works with the condenser to start the refrigeration process. In this process, only a small amount of electricity is required to power a pump and fan. Austin Solar AC writes a brief description of the process (diagram shown at the top of the post):
The diagram above shows sunlight striking the parabolic solar energy collector located on the roof of a home. The collector heats up the transfer fluid, which is held in a special storage tank. This heat is then used to power the absorption cycle air conditioning unit. Home heating and hot water can also be provided utilizing the solar energy collected.
I still have some questions as to the costs of solar air conditioning vs. traditional air conditioning and maybe one of the companies above can help with a cost analysis of the two technologies, but it sure looks interesting!