Flat panels in this category (non-concentrating) are used to heat a fluid, usually water, for residential applications. For simple swimming pool heat, a thermocouple signals a pump to run when temperatures are warm enough to provide usable heat.
One panel version uses a sputtered, blue-copper absorber surface. The extruded aluminum frame is welded on each corner with an electrostatic powdercoat finish. Polyurethane hard-foam insulation minimizes heat loss. Such panels are often available in 4 x 8 ft, and 4 x 10 ft sizes.
One hybrid photovoltaic-thermal collector combines functions of both into one panel. It simultaneously produces electricity and hot water.
One manufacturer of commercial solar thermal systems specializes in 65 to 130 ft. collectors with features such as a PVD coating for best solar absorption, a laser welded absorber and serpentine heat-transfer system, and materials that exhibit low heat loss and high insulation values. The company adds that the equipment is versatile so that it mounts on a roof or stand on the ground. A weather-resistant anthracite powder coated aluminum frame ensure a long useful working life, and the company backs that claim up with a 10-year warranty and SRCC-OG100 certification.
The flat plate collector is available as a single-piece large collector. Manufacturers may also offer a variety of light-duty commercial solar thermal collectors, storage tanks, controls, and accessories for a single source solar package.
Another solar equipment manufacturer offers thermal solar equipment in low-pressure and highpressure models. A low-pressure gravity-feed design consists of a vacuum glass tube collector, an insulated storage tank and optional stand parts. The evacuated glass tubes are filled with water and exposed to sun, thus heating the water.
Because the specific gravity of cold water is heavier than hot water, the hot water in the glass tubes rises in the insulated water tank, while cold water in the tank sinks into the glass tubes. As this cycle continues, water in the solar water tank slowly circulates while its temperature rises. The effect, called a thermosyphon, is based on natural convection.
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