The generation of energy from sunlight is directly linked to what is called the photovoltaic effect, first observed in 1893 by physicist Alexandre-Edmond Becquerel.
Converting the sun's energy is through the modules, or photovoltaic panels. The technologies known and used in electricity generation panels are monocrystalline, polycrystalline and amorphous and microamorfos.
These green technologies (which also include The wind, biomass, wave energy and tidal ener water for example) are mostly applied in the production of electricity and therefore we speak of photovoltaic or water heating, which is called thermal energy. Another designation is respectively solar photovoltaic or solar thermal energy.

In the generation of photovoltaic solar energy there are two main application fields: the integration into the electricity distribution network (grid connected) and its subsequent sale to the grid and use in isolated or autonomous systems, which provide electrical power in places where there is access to electricity network.

Similar to what happens in Germany, many countries, including Portugal, took political decisions in order to subsidize the production of electricity through alternative energy and non-poluting energy. Guided by the renewable energy law (German: Erneuerbare Energien Gesetz, or EEG) obliges the state distributors and producers of conventional energy and national energy agencies to buy green energy at a higher price than the market price.