Solar Hot Water
A lot of folks out there think of one thing when they hear the term "solar power". They think of electricity. Actually, two kinds of solar power exist - solar electric and solar thermal. Solar electric uses photovoltaic (PV) panels that transform light photons to electricity. Solar thermal heats water.
Solar thermal has many uses. It can be used to heat the water that is used for showers and laundry. It can be used in a radiant heat system to heat floors or living spaces. It can also be used to heat swimming pools.
How Does It Work?
There are many different types of solar thermal systems, so for the sake of simplicity we will discuss a simple drainback system. This system consists of solar collectors, a heat-exchange tank, a pump, and a controller. Solar fluid - in this case, tap water - resides in the heat exchange tank (that looks like a traditional hot water heater) and is pumped up to the solar collectors on the roof (or wherever the panels are located - they do not HAVE to be on the roof). The collectors have hundreds of feet of tubing inside them in which the water is circulated. When the sun shines on the solar panels, the water in the tubes in the collectors gets very hot and returns to the solar heat exchange tank. The domestic water is pumped through a coil of copper tubing and this coil is inside the solar heat exchange tank. The heat from the water in the tank is transferred to the potable water in the coil of copper tubing, heating the domestic water that is later used for household processes.
Solar thermal has a much quicker payoff than solar electric - usually 5 to 7 years. It is especially effective where a large concentration of people reside, like a dormitory, fraternity, sorority, or even a jail. These examples tend to be the most popular installation sites for solar hot water systems. The system configurations for these types of locations usually consists of one 120-gallon solar heat exchange tank with a pump and controller, and four or five 4' x 10' solar collectors.
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