There are two distinct types of “solar systems.”Many people don’t realize that there are actually two kinds of “solar systems” that can go on your roof. One heats water. The other makes electricity.
In the Aug. 28–Sept. 3 column I discussed solar water heating… but the photo that ran with the article showed a solar electric system. Although the photo may have been confusing, it’s actually not hard for a passerby to tell them apart.
A solar water heater is usually fairly small—two or three rectangular collectors (many people call them “panels”) connected with insulated pipes that run to a storage tank. Often the tank is in the garage or elsewhere on ground level; sometimes it’s lying on the roof above the collectors. These few collectors are all you need to make nearly all of the hot water your family uses in a day. (On rainy days, an electric element in the tank helps heat the water.) If you looked through the glass cover on the collector, you’d see a solid black metal plate with pipes attached—pretty simple, but very effective at collecting the sun’s heat for your family.
A solar electric system (also known as photovoltaics, or PV) usually includes many more “panels” (properly called “modules”). It would not be unusual to see an array containing more than a dozen modules on a residential roof—sometimes as many as the roof can fit on its south-facing surface. Commercial systems may have many more modules, depending on how much power is needed. Some PV modules are a deep blue color and catch the light in interesting patterns; these are made of polycrystalline silicon. Other modules are assembled from individual solar cells connected with fine silver wires. Still others may be a dark brown film, which might be laminated directly to roofing material.
This series of columns in the Maui Weekly explores both kinds of solar energy systems and what they can do for you. Solar water heating systems are by far the most cost-effective way to heat water, but they don’t make electricity. Solar electric systems do make electricity, but should not be used to heat water.
Stay tuned for more details!
In partnership with the state’s energy office, the Maui Weekly provides this feature to help Valley Isle homeowners reduce their utility bills and increase their environmental awareness.