1.1 Solar Energy Today
Several kinds of very practical solar energy systems are in use today.
The two most common are passive solar heated homes (or small buildings)
and small stand-alone photo-voltaic (solar electric) systems. These
two applications of solar energy have proven themselves popular over
a decade of use. They also illustrate the two basic methods of harnessing
solar energy: solar thermal systems and solar electric systems.
Solar thermal systems convert the radiant energy of the sun into heat and then use that heat energy as desired. The solar electric systems convert the radiant energy of the Sun directly into electrical energy which can then be used as most electrical energy is used today.
Among the less popular, but still effective, solar energy systems are: domestic water heating systems, remote solar powered water pumping systems and remote electric power systems for radio repeaters.
Of course, almost all spacecraft use solar power for their instrumentation and communication. The Mir Co-operative Solar Array Program is one example.
1.2 Solar Energy Tomorrow
Several applications of solar energy are now being tested and may
be used in the near future. Some of these are large scale photo-voltaic
systems supplying power to the electric utility grid and solar thermal
electric power systems to supply power to the utility grid (power
tower systems).