If a thermosiphon system isn’t an option, your next choice is a pump circulation system. This system is pretty similar to the thermosiphon system except that the force that moves the heat transfer liquid is a small electric pump. Most systems use AC pumps that run off household current, but, as noted below, another very smart option is a DC pump powered by a small solar electric (PV) panel.
Solar collectors in pump systems are usually mounted on roofs, but can also be mounted on wood or metal racks on the ground, so long as they are in full sunlight all year round. Solar hot water tanks are located inside homes, usually in basements or utility rooms next to the conventional water heater, soon to be relegated to the status of backup water heater.
The small electric pump, which is located inside, forces the heat transfer liquid up through the panels and then back down to the thermal storage tank.
Read about the two kinds of pump circulation systems: Open-Loop and Closed-Loop .
Power Your Solar Hot Water System with Solar Energy
If you are concerned about the electricity required to run the pump in a solar hot water system (to be honest, it’s really not that much) or if you want to go totally solar and simplify your system, you can run a solar hot water system off a small solar electric or PV panel — a 30- or 50-watt PV. In such systems, a PV panel is mounted next to the solar hot water panels and is wired to a DC pump. (PVs produce direct current electricity.) When the sun rises, the PV panels begin to produce DC current. Electricity flows to the pump, waking it up from its evening snooze. The pump then begins to propel the heat transfer fluid in the system through the panels and through the pipes. Heat generated by the solar collectors therefore begins to flow from the panels to the storage tank. When the sun sets, the system shuts off.
PV direct systems are simple and cost-effective, and eliminate the need for sensors and controls that can break down. One manufacturer, Sol-Reliant, produces a sleek system with a built-in 35-watt PV panel. It is one of the easiest systems to install. You can learn more about it at
http://www.solreliant.com .
Read A Short History of PV Cells and Solar Energy .
What is a Solar Hot Water System?
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