The Sun is by far the largest energy source in the solar system. Amount of the solar energy that is every minute reaching Earth is enough to satisfy annual energetic needs of the mankind at the current stage of development. Despite its huge potential, only small percentage of energetic needs is covered with the use of solar energy. This is partially because of the slow development of current technologies that are using solar energy, although the main reason lies in the current price of the system that is used for exploiting the solar energy.
There are couple of methods of exploiting the Sun's energy. The simplest and the cheapest method of using the solar energy is surely heating of the water or some other liquid for use in households. Elements that are using Sun's energy for water heating are called solar collectors and they're usually set on rooftops of houses and buildings. The second method of using the Sun's energy is concentrating the solar energy with the help of mirror system and creating the large amounts of thermal energy which is later, in standard generators transformed into an electrical energy. These facilities can be very big and are usually built in deserts and are used for normal commercial production of electrical energy.
Photovoltaic cells are third and the most desirable method of exploiting the Sun's energy, but because of the weak efficiency and large expenses this method isn't used on the larger scale. Photovoltaic cells are directly transforming solar energy to an electrical energy. Photovoltaic cells are usually used on places where it isn't possible using some other energy source, for instance on satellites, on road signs, etc. Additionally they're used for powering many of small consumers like pocket calculators.
Photovoltaic effect was discovered by French physicist Alexandre-Edmond Becquerel (1820-1891) in the year 1839. Photovoltaic cells are built out of two layers-positive and negative, and the difference of potentials between these two layers depends upon the intensity of the solar radiation. Solar energy is coming on Earth in the shape of photons. Photons once they fall on the solar cell's, are transferring all of their energy to the panel, making it possible for negatively charged electrons to burst out of the atom. These electrons after picking up the energy from photons have enough energy to move around and are moving towards other (negative) side of the panel and this is how the difference in potentials happens and electrical energy generates. Photovoltaic cells are made up from silicon and silicon is one of the most common elements on Earth.