Solar Thermal Using Glycol
The most popular, most highly recommended solar thermal system:
Glycol (non-toxic antifreeze mixture) runs through a system of piping, connected at one end to a solar collector plate* and at the other end to a holding tank. The anti-freeze is pumped through this closed loop system, where it is heated in the solar panel then has its heat transferred to water in a water tank, similar to the tank in any regular water heater.
The water is then transferred to your regular water heater, where it is finally heated to the temperature you choose-- regulated by a thermostat just as it is with a conventional water heater. You will never notice the difference-- except in significant long term savings.
Another kind of solar thermal closed loop, drainback systems, use water (not glycol).
Some experts caution against problems with overheating your closed loop solar thermal system. Especially in the Deep South climate, when the system is not in use, the plate can heat the stagnant glycol to over 400 degrees Fahrenheit. This can be dealt with through the use of an additive that will inhibit this glycol breakdown caused by overheating. You can also have venting built into the thermal collector.
If you do live in a warm climate, there are other collectors or solar thermal heating systems.
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The total annual maintenance costs will be about $25 at the most. You may need to replace the glycol once a year. You might want to have a service technician come in to check on your circulating pump and other components every three to five years.
Other solar thermal systems
An entirely different system can be used to heat swimming pool water. Learn more about solar pool heaters.
*Solar collectors used in this system are very different from solar panels used in solar electricity systems.