All life on Earth depends on energy from the sun. Solar energy is the source of energy for photosynthesis. It provides the warmth necessary for plants and animals to survive. The heat from the sun causes water on the Earth's surface to evaporate and form clouds that eventually provide fresh rainwater. Nevertheless, in the 20th century, the sun's energy has become an increasingly attractive source for small amounts of needs. A number of devices for …showed first 75 words of 499 total…

…showed last 75 words of 499 total…a heliostat that directs the sun's rays from the mirror to the target. Positioning motors, drives, and controllers make such systems expensive. Less costly collectors can produce temperatures lower than those of more advanced concentrating collectors but higher than those of flat-plate collectors. For example, parabolic reflectors that concentrate sunlight on black pipes can produce fluid temperatures of about 400B0 to 55 0B0F and can concentrate the solar energy up to 50 times its original strength.