Solar Thermal System Components
Solar thermal systems using glycol (the most common ST system) is one of several called active solar thermal systems. All this really means is that it uses a pump. A passive solar thermal system does not use a pump, but moves the liquid through other means.
The use of an anti-freeze mixture also classifies this as an indirect circulation system.
Some components of this system are:
Solar thermal collector panels
These are usually 4'x8'. Match these with the amount of water you want to heat. Typically, you will have five panels for a solar thermal system for a household of four. In Canada, glycol systems are preferred with a typical system being 2 or 3 panels. We have some simplified tips on sizing your system.
In a solar thermal system, these are most commonly flat plate collectors. All this really means is that it is a block of black material (polymer or metal). Tubes filled with the anti-freeze material run through this black material, collecting the heat absorbed from the sun.
Solar thermal tanks
Tanks are typically 50 - 100 gallons depending on your needs (size of your household). A rough guide is 20 to 25 gallons per person.
The heat exchanger
This relatively simple device passes heat from one substance to another-in this case, heat is exchanged from the anti-freeze (inside tubing) to water.
The effectiveness of a heat exchanger is measured in BTU/hr. A standard for a solar heat exchanger is 30,000 BTU/hr to 60,000 BTU/hr.
Solar thermal drainback systems have some similarities to the system described here, but they use water instead of glycol.
For warmer climates
If your climate is warm enough (never or rarely freezes) you may want to consider other collectors like a direct circulation system.