The applications are diverse and date back millennia.
In Europe, farmers used elaborate field orientation and thermal mass to increase crop yields during the Little Ice Age.
Solar power generally describes technologies that convert sunlight into electricity and in some cases thermal or mechanical power.
This is the first known example of a solar powered mechanical device.
The progeny of these early developments are concentrating solar power plants.
This breakthrough marked a fundamental change in how power is generated.
Prices on the other hand have fallen from $300 per watt to less than $3 per watt.
The diversity of form and long history of solar energy are manifest in a wide variety of applications.
Some classifications of solar technology are active, passive, direct and indirect.
Passive solar systems use non-mechanical techniques of controlling, converting and distributing sunlight into usable outputs such as heating, lighting, cooling or ventilation.
Direct solar generally refers to technologies or effects that involve a single conversion of sunlight which results in a usable form of energy.
A solar cell or photovoltaic cell is a device that converts light into electricity using the photovoltaic effect.
One cost effective use has been in very low-power devices such as calculators with LCDs.
A third use has been in powering orbiting satellites and spacecraft.
The panels should be mounted perpendicular to the arc of the sun to maximize usefulness.
However, these solar panels may also be used to charge batteries or other energy storage device.
Total peak power of installed PV is around 6,000 MW as of the end of 2006.
Declining manufacturing costs (dropping at 3 to 5% a year in recent years) are expanding the range of cost-effective uses.