SOLAR HOT WATER
"Thermal Solar" is solar used as a heat source. Heating domestic hot water, radiant in-floor heat and pool/spa heating are examples of thermal solar. Thermal technology is a very different technology from PV although it sometimes looks somewhat similar installed. When you see a row of solar panels on a roof, the question is, "are they solar electric panels producing power which goes to an electric box in or on the building they are on or near, or are they full of a water/glycol mixture that warms up directly from the sun to heat water in a tank inside the building they are on or near?". How can you tell the difference?
The electric panels are usually smaller and not tilted as steeply to the south. PV panels have wires only coming from them (though this is often in conduit which resembles pipe). The Thermal panels are much larger and look like clusters of pipes with glass over them tilted up at a very steep angles. They have copper pipe wrapped in heavy insulation coming out of them.
Thermal solar is much more efficient energy transfer than PV. Thermal is close to 70% and PV is 20% at best. Thermal solar has the problems of leaks and pressure maintainance and proper insulation. A system done properly can work without problems for as long as thirty years. Some installers recommend changing the glycol every 5 years, but some have been known to let it go without changing for much longer periods of time.
This is the woolmill in Hall MT. They wash wool in 30 gallon sinks here and are off-setting as much as $5,000.00 in propane per year. This system, installed in the spring of '04, is providing about half of all of the hot water demanded by the business for year around operation.