Solar cells are the key components and the smallest units of photovoltaic system. Combined to form solar modules, arrays or panels, they capture the solar radiation that impacts them. Direct current is generated between the upper and lower surfaces of the cells.
This current can be as much as 0.5 V per cell and is used for producing electricity. An individual solar cells measures between 10 and 15 sq. cm and consists mainly of silicon, an element that occurs very commonly in Nature. Conventional solar cells attain an efficiency of up to 17%, which means that up to 170 Wh (watts per hour) is generated per square meter.
The total output of a photovoltaic system is measured in kWp (kilowatt peak). An average photovoltaic system with an output of 1 kWp saves the environment up to 500 kg carbon dioxide and other pollutants every year.
Components of a solar thermal unit: