Solar absorption chillers are thermally powered like adsorption chillers but use a solid adsorbent rather than the liquid absorbent. Both use water as the refrigerant and both require very low pressures to operate.

As you can see by the article referenced below the scale of these systems can be quite large. SolarAire offers adsorption chillers as small as 2.1 tons (will cool an area of 900-1,400 s.f.) DR

http://www.solarserver.de/solarmagazin/anlage-e.html

Absorption refrigeration has been around since the 1920’s, and is still used widely in RV’s, remote cabins and anywhere electric-compression refrigeration is not an option. Even Albert Einstein had a patent on aborption refrigeration. For an interesting discussion on this go to: http://en.wikipedia.org/wiki/Einstein_refrigerator