This page was last modified on Thursday, February 26, 2009
FAQ - Solar Hot Water
Q: What is solar thermal?
A: Solar thermal is solar hot water. The panels contain pipes through which a fluid (water or water antifreeze, or other more exotic fluids) is circulated. The fluid absorbs solar heat while in the panel and is circulated through a second coil in preheat tank, where the solar heat is transferred to the cold inlet water. Final heating to a higher temperature is usually accomplished with a secondary gas or electric water heater, but the energy required to get to the desired temperature is greatly reduced by the solar pre-heating. If being used for a lower-temperature, less critical application, such as pool heating, often no supplementary heating is needed.
Q: Am I a candidate for solar thermal?
A: The more hot water you use, and the sunnier your south-facing location, the more likely that that solar thermal would be a good choice. While residential applications can sometimes be harder to justify economically, large commercial hot water or heating users are quite well served by the economics of solar thermal. If you are heating water or space with electric resistance heating, then solar thermal should be a distinct and immediate advantage.
Q: Would it make sense to heat my water or space using photovoltaics?
A: Absolutely NOT! PV efficiencies are typically in the 12-15% range, whereas solar thermal is in the 60% range. PV is appropriate for running lighting, appliances, PCs, phones, etc. For any heating application, solar thermal is usually the only worthwhile approach.