Solar Heating—and Cooling, too

Some solar systems can supplement hydronic (hot-water) heating systems, but don’t expect the same kind of efficiencies or payback as with solar collectors that just supply domestic hot water. That’s because these systems are expensive, and the highest demand for heat comes during the darkest months of the year. The most benefit comes in the shoulder seasons, spring and fall, when solar hydronics can supply 20 percent of the total annual heating load.

A more promising application, still in development, is using solar-heated water to drive chillers, cooling systems without compressors. It’s a tantalizing concept because solar output peaks at the same time as AC use. The challenge has been to design small-scale residential chillers that can run at the lower fluid temperatures that a solar array can produce.

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