Alternative Energy Systems For the Home
How Solar Thermal Works In The Home
Active solar water heaters use pumps to circulate water or an antifreeze solution through heat-absorbing solar thermal collectors.
In an indirect system, also known as “closed loop,” a simple pump moves the antifreeze solution through a loop into the solar collector, through the collector’s pipes, and out of the solar collector. Then, the sun-warmed antifreeze solution flows into a heat-transfer unit where it warms the cool water heading into a conventional hot water tank. The antifreeze solution then returns to the pump and again flows into the solar collector without ever mixing with the building’s water. Indirect systems are encouraged in climates with extended periods of below-freezing temperatures.
In reality, both direct and indirect systems are somewhat more complicated than presented here. Differential thermostats, pumps, sensors, and controls are used so the simple systems illustrated work effectively and safely. However solar thermal technology is mature and proven with few maintenance requirements from the installed systems.
Collecting The Sun
Solar thermal systems also differ by the type of collector used to gather and store the sun’s energy. Flat plate collectors are the simplest and most common type. Copper pipes wind back and forth through the flat plate collector, which is painted black to absorb heat and covered with glass, or “glazing,” to prevent heat from escaping. Often the pipes are painted black and bonded to the material of the flat plate collector to maximize heat absorption.