Solar water heating on roof in Washington, D.C.
Image by singhvp93

Evacuated-tube solar collectors on a roof in Washington, DC.

Solar Thermal Systems

Solar thermal systems convert solar radiation to thermal energy. These systems differ from PV systems, as PV systems convert solar radiation to electricity, not thermal energy.

How do they work?

The main components of a solar thermal system are solar collectors and a hot water tank. Solar collectors, like solar panels, are installed on the roof of a building. Solar collectors convert solar radiation to heat, which is then transferred to a hot water tank through a heat transfer fluid. The heat transfer fluid is comprised of either water, ethylene glycol, or a combination of the two liquids. There are two types of solar collectors: flat-plate and evacuated-tube. The question of which collector is preferred for your system depends on a number of factors: the roof of the building in question, your budget, the climate of your location, and the type of system you want to design.

Once the hot water tank is heated, hot water can be dispensed throughout your home or transferred to a boiler. If your solar thermal system does not generate enough heat to the hot water tank, a backup system will kick in.

What kinds of solar thermal systems are there?

There are two types of solar thermal systems available: active and passive. Active systems are more expensive than passive systems, but are also more efficient. The most common uses for these systems are:

  • Domestic Hot Water (DHW)
  • Swimming Pool or Hot Tub Heating
  • Space Heating Systems 

Why go solar thermal?

The installation of a solar thermal system will:

  • meet 90-100% of your hot water needs in the summer
  • reduce your emission of greenhouse gases
  • lessen your dependence on nonrenewable energy sources, which are subject to price fluctuations
  • lead to long-term financial savings
  • lead to marketing and public relation benefits for businesses

How much will it cost?

Estimate the cost and energy efficiency of a solar thermal system.

Last updated September 1, 2021