But concerns over collector area depend on location. In the developing world, solar powered ice makers allow locals to store the village's food or medicine without any electricity. For example, in May charitable organization, Heifer International, set up three solar ice makers in remote areas of Kenya. Each will be able to keep 26.5 gallons (100 liters) of milk chilled. More than 500 members of two dairy cooperatives are expected to benefit directly.
Most of the interest in such solar refrigeration in Western countries comes from the commercial, not residential, sectors. Cost is one reason—absorption chiller systems typically cost $7,000 to $10,000 per ton of cooling; one-ton window air conditioners from big box retailers start around $250—but companies can save on electric bill as well as enjoy a more benign environmental image.
Building occupancy patterns is another; most Americans are not at home during the day. "We don't have as much daytime occupancy in residential buildings as in commercial," says Pat Hale, sales manager for Yazaki Energy Systems, in Plano, Tex. Other problems include the expense of retrofitting homes to add plumbing to the attic. And the high temperatures associated with concentrating solar collectors raise liability concerns.
But some entrepreneurs think a residential market nevertheless is emerging. Walter Ross is CEO of Austin Solar AC, a start-up that is testing 36,000 and 60,000 Btu solar-fired chillers. The units provide cooling in summer and heating during winter by just using the sun's heat directly. "We're getting a lot of interest from people who have been using propane for heating," he said. "The biggest issue we run into with these is siting: Most neighborhood associations won't allow these things on your roof."