As with hydropower, solar energy has a long history. Many pre-historic cultures used it to warm their dwellings, dry their clothes, and cure their food. The importance of solar energy was so great that most cultures revered the Sun and created rudimentary observatories to track its location in the sky (ex. Stonehenge).
Some found solar energy so important that they even codified its power in their laws.
Ancient Romans relied so heavily on solar energy to heat their homes and bathhouses that it was illegal to build a house or dwelling so tall so as to block the sunlight of any neighbor.
Ancient Rome was not the only culture to rely heavily on the Sun for energy. The Anasazi cliff dwellers of the ancient American Southwest also used their knowledge of the Sun’s motion in the sky to heat and cool their homes. They built their dwellings into the sides of cliffs that faced the south. In the winter, sunlight was able to shine on their homes, while the cliffs protected their homes from cold northern winds that might blow.
In the summer, the overhangs from the cliffs shaded their homes from the Sun, and thus made it cooler.
Just as with hydropower, solar energy began to wane as a conventional energy source as fossil fuels and nuclear energy became cheap and reliable. The expense and variability of using sunlight has relegated its use to unusual situations where fossils fuels and nuclear energy are not available or where they are prohibitive to use or maintain. A perfect example of this is on satellites, which need energy to power all on board computers and instrumentation. Using fossil fuels to power a satellite over its lifetime would require quantities of oxygen and fuel that would be prohibitive to shoot into orbit. Nuclear material would be fine for powering the spacecraft, but would become very problematic when the satellites life was over and it came crashing back to Earth.
An example of solar energy that is closer to home are interstate call boxes that are in remote locations. Rather than spending a lot of money to run telephone and electric lines out to these call boxes, one can use a solar panel equipped with a battery and a cell or satellite phone.
Outside of these few types of uses, though, solar energy has seen limited usage. In fact, in some parts of the U.S., the use of solar energy is prohibited. Covenants in some modern subdivisions that have homeowners associations actually forbid the use of solar panels or clotheslines for drying clothes. The reason for this is one of aesthetics: using solar systems can look “ugly” and hurt property values. Some states, such as California, have actually written state laws that prohibit subdivision convents from doing this.
I’m pretty worried about this folks that bring this kind of laws that forbid use of solar energy! People still has to learn that energy is not free, but is everywhere, and sometimes clean, but not pretty.