Usually when you hear "solar" it's not followed by "cooling"! In this case, manufacturers have found a way to create solar-powered cooling units. Most units on the market are "hybrid" - meaning they use both grid energy and battery power. The batteries are charged by integrated solar panels.
Check out some of the options on the market:
Rotarctica is a company that's taken it a step further and has developed a unit that uses the sun for actual cooling. Again, not being an engineer, I don't completely understand...but, Treehugger has a great explanation of how these units work. Wikipedia also has a lot of good (I think) information.