Solar energy results from the fusion process in the Sun, where Hydrogen combines to form Helium. Solar irradiance at the Earth’s orbit is almost constant at 1,367 kW/m², however at the earth surface solar irradiation changes between 0-1100 W/m². The amount of incoming solar energy to the Earth greatly exceeds world energy consumption.

The efforts to utilize the solar irradiation in the energy production have gained speed especially after the 1970’s. Since that time, as systems have improved technically the costs also have decreased while the importance of the resource has been acknowledged with regard to the environmental benefits.

Solar energy embraces a wide spectrum of technologies that change significantly in terms of technological level, applications and methods. However it is possible to classify solar energy in two main groups:

 

•	Thermal Solar Technologies: These systems produce primarily heat. The heat can be directly used or can be used to generate electricity.
•	Photovoltaic Systems: Also called solar cells, photovoltaic cells are  semiconductor devices that convert sunlight to electricity directly.