What are the facts about solar thermal energy?


Above: A Solar Thermal Energy System in Greece

Solar thermal energy (STE) encompasses any system that uses the sun’s energy to heat water. The three classifications of solar thermal are:

  1. Low-temp: solar pool heaters
  2. Medium-temp: residential and commercial solar hot water systems
  3. High-temp: use mirrors to focus the sun’s energy, as in concentrated solar power collectors.

The key fact to understand about thermal systems is the fundamental difference between solar thermal and solar photovoltaic. The latter converts solar energy into electricity, while the former uses solar energy to heat water (which can produce electricity by driving a steam turbine).

Solar Thermal Energy Facts

#1 Solar thermal can be extremely cheap and cost effective.

As you can imagine, building a simple solar thermal panel is within the grasp of the average homeowner. At the risk of oversimplifying, all you need is a panel that contains a black backing, a series of copper piping through the panel, and a place to mount it. Of course, you’ll need to know basic plumbing to hook this system up to a house and provide hot water, but if you’re handy this is a great DIY project.

#2 Solar thermal and photovoltaic systems need similar conditions to work.

This should be rather obvious, but solar thermal systems work best and are most popular in places like Israel, Greece, Turkey, China, Australia, Japan, Austria, and China. Anywhere where electricity is expensive and sun is abundant.

#3 Solar thermal is more efficient than solar panels.

Converting sunlight into electricity is a bit more complicated than harnessing heat. While the average solar panel is something like 15% efficient (see solar panel efficiency), the transfer of solar heat energy into water can be more like 50% efficient, meaning much more energy can be harvested per unit area. It’s also important to note that solar thermal can store energy in the form of hot water, which is much more efficient than the electrical storage required by solar panels.

#4 Solar thermal is usually a better financial investment.

The cost of a residential solar thermal system is somewhere around $4,000-$6,000 (not counting federal tax rebates), with wholesale pricing around $1200-$2200. Solar panels are much more expensive (try calculating the cost of a solar array), closer to $10,000 and up. Combined with the greater efficiency of solar thermal energy and the overall return on investment is much greater.

For more information on this topic see the links listed above, as well as our page of solar energy diagrams.

Image Credit: Wikimedia Commons