The history of solar energy goes back to 400 B.C., when the ancient Greeks and Romans used the sun to heat certain areas in their homes. Solar energy is the earliest form of energy that is still being used as a power source for many domestic, industrial, and technological operations.
In 1865 a French math instructor, Auguste Mouchout, invented the first machine that could transform solar energy into mechanical power. The machine worked by allowing the sun to heat water until it turned to steam. Concerned about people's dependence on coal as an energy source, Mouchout strove to find other power sources. His invention, a steam engine that could also be used as a refrigeration device, is known as the first solar motor.
At the height of Mouchout's popularity, Englishman William Grylls Adams published a book entitled A Substitute for Fuel in Tropical Countries. This book was based on his own invention, the power tower. With the help of his apprentice, Richard Day, he constructed a reflector using 17-by-10-inch flat silver mirrors set up in a curve to absorb the sun's energy. This invention was able to convert solar energy into 2.5 horsepower of mechanical energy, which was definitely stronger than the 0.5 horsepower generated by Mouchout's machine. Adams was the person who defined the solar tower concept that is still being applied in many technologies today.
In the early 1800s, John Ericsson, an inventor who designed and built warships, developed a heat engine that could be used to power carriages. Later in his life he created a parabolic trough that enabled him to store solar energy. This machine was simpler and less expensive than the solar energy converters already invented by Mouchout and Adams.
Henry E. Willsie, one of the pioneers of solar energy invention, began running a series of tests on ways to store solar energy in the early 1900s. He started by heating gallons of water with the sun's rays and then putting the water in insulated containers. Inserting tubes into these containers, he added sulfur dioxide through electrolysis, making solar energy far more efficient to use. This whole process could power a steam engine at 15 horsepower—the most powerful solar motor invented up to that point. His insulated energy invention was also the first method able to channel the sun's energy during the night, after the sun went down.
Today, a number of solar energy innovations are being used in homes and businesses. In architecture, a number of solar energy housing developments have been built. In agriculture, solar machines assist in heating water and completing other tasks on some farms, as well as in electric supply. Solar energy is also being utilized by the automobile industry, particularly in hybrid electric cars. The sun has definitely provided a clean and economical alternative power supply—and has made a big impact on the way society functions today.