Footnotes

Solar collectors are devices that are used to collect solar energy and transfer this energy in order to heat water. Along with solar panels, solar collectors (Solarkollektoren) are the most common type of renewable energy technology that is used in modern homes. There are a few different types of solar collectors on the market, including the two most popular categories of flat plate collectors and evacuated tube collectors. The design and construction of solar collection technology is improving all the time, as more and more people use these devices and more investment money starts flowing in for manufacturers and developers. The two most common categories of solar collectors are concentrating devices and non concentrating devices, the later of which uses the same area for collection and absorption.

Flat plate collectors were first developed by Hotel and Whillier in the 1950s, and have become the most common type since this time. They use some kind of dark flat-plate absorber, a transparent cover, a heat-transport fluid, and a heat insulating backing made from a thin absorber sheet. The heat transport fluid could be one of many things, with popular choices being air, antifreeze, and water. In contrast to flat plate technology, evacuated tubes use heat pipes instead of allowing liquid to pass directly through. There are advantages to both of these technologies, with flat plate collectors usually losing more heat to the environment than evacuated tube designs. However, flat plate technology is also more simple and less expensive, despite the fact it is not as efficient.

While solar collectors normally describe one of these water heating technologies, the term is also used to describe commercial electricity systems. Parabolic troughs are also used to generate electricity through solar collection, as are power towers and parabolic dishes. Solar collectors are likely to become even more popular in the 21st century, as people around the world look for new ways to save money on their energy bills and become more involved in sustainable energy solutions that help the planet.