Monday, September 14, 2009

What are Solar Water Controls?

AKA: differential controls, PV module

In active systems using pumps, whenever the collector is hotter than the storage tank, the pump should be on and the system circulating. When the tank is hotter than the collector, the pump should be off. This function is performed by either a differential thermostat control system or the use of a PV-powered pump. The differential thermostat controller compares heat sensor readings from the storage tank and collectors and switches the pump accordingly.

With a PV-powered pump, a solar-electric panel is connected directly to the pump. It´s a simple setup—when the sun comes out, the pump comes on. The brighter the sun, the faster it pumps. Controls are not needed in batch heater systems, where energy is moved by simple water pressure, or in thermosyphon systems, where energy is moved naturally by heat rising.

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