While a few hardcore greenies have decided to give up refrigeration altogether (see Can I go without a refrigerator?), most of us balk at the idea of having to store dairy products on the porch in winter (and what, no calcium in summer time?). There's still that 450 to 1,000 annual, CO2-emitting kWh to worry about, though.
A couple of NASA scientists came up with an ideal solution: solar-powered refrigeration. It's not a new concept, but the NASA-backed SunDanzer solar refrigerator is one of the most widely available and intensely practical applications of the idea.
SunDanzer is a top-load, chest-style refrigerator (or freezer). It uses the vapor-compression type of system that probably runs your current home refrigerator. It reaches the same low temperatures. The only real difference is SunDanzer plugs into a solar-panel system instead of into a regular wall outlet.
To maintain optimal refrigeration, the solar panels need five hours of direct sunlight per day [source: NASA]. Does that mean your milk goes bad when you've got a cloudy spell? No, and here's the intensely practical part: The unit can store excess energy, so it can actually go for a week without sun and still keep things cold. Plus, there's a battery backup just in case.
Depending on size, a SunDanzer runs anywhere from $650 to $1,300.
Next up, a "Blue" phone that's really pretty green.