The sun's light and heat is unlimited and always available during cloudless, daylight hours.
Passive solar energy requires creative design more than new technology. For example, you can capture the sun's heat with large south facing windows and exterior walls covered in dark paint.
Solar cells convert the sun's rays into energy. They can range in size from small disk to power a garden lamp to large panels that can be placed on a rooftop to power homes and buildings. Energy can be stored in batteries for use during cloudy days or evenings.
Solar technology is still under development and not widespread, which partially accounts for its high cost. The typical home solar installation, even with government subsidies, only pays for itself after at least a decade of use.
Because solar energy requires no expendable fuel and produces no byproducts, it is an environmentally friendly source of power.