My new solar cooler prototype is based on the Vuilleumier cycle. It uses compressed air as the working gas and solar energy to create pressure variations within the system, which are then used to drive a cooling process.
In this simplest configuration, the displacers are moved manually by metal cables.

This is a closeup of one of the displacers (the "hot" one) in motion to the left, forcing air around itself to the right and heating it regeneratively.

Here's how I'm probably going to test this prototype, in my backyard, using an old hot tub as the ambient water bath. I plan to use a few mirrors to aim extra sunlight at the hot end and then measure the cooling effect at the cold end somehow.

Here's a page of background info on the Vuilleumier cooling cycle. I'll be adding more info (and info that is more comprehensible!!!) soon.

Marc's Solar-AC FAQ entry on Vuilleumier cycle

Marc Ringuette, 2 December 2003