The purpose of your solar powered
fridge should dictate the model you purchase and how you configure
its setup. If you are living completely off of the grid (or
stay in a remote location for any length of time) you will probably
want to choose a solely 12 or 24 watt DC unit with a battery and
connected to a solar cell or wind turbine.
SunDanzer produces popular products that fit that description.
Here's a solar refrigerator flyer
that contains some general information.
Backwoods Home Magazine has a great page reviewing solar DC
If you're looking for a backup
refrigeration system should there be a power outage, you can use the
same setup as above connected to a 110 to 12v DC battery charger.
The only time the battery would be in use & discharge is in the
event of a power failure. An normal fridge can also be run off
of solar with the use of a power inverter. They do however
draw more current and require a larger solar cell array due to their
lack of efficiency.
There is a type of refrigeration
that does require any panels, cells or even batteries and can be
made out of everyday materials like cardboard, dirt and recycled
metal. Cooling is achieved through conduction, convection and
Scientific American has a really cool (pun
intended) article about
solar heat refrigeration. The freezer page on this site
may also be of interest.