HOW PV WORKS
The photovoltaic effect (a physical phenomenon of light-electricity conversion) was discovered in 1839 by the French physicist Alexandre Edmond Becquerel. Experimenting with metal electrodes and electrolyte, he discovered that conductance rises with illumination. A few decades later, in the 1870's, discoveries by Willoughby Smith and William Adams led to the first selenium solar cell construction.
A comprehensive description of the photovoltaic effect was written in 1904 by Albert Einstein. His theoretical explanation led to the discovery of a method for mono-crystalline silicon production (Jan Czochralski, 1918), but it wasn’t until 1941 that the first silicon solar cell was constructed.
The basic element of a PV system is this solar or photovoltaic cell. The most common type of cell is made of crystalline silicon. High purity silicon undergoes a series of processes, the end result of which is a cell with semiconductor layers. When light falls on the cells, the electrical charges in the semiconductor layers separate and produce a DC voltage. The voltage created depends on the specific cell material; for silicon this is around 0.5-0.6V DC. Normally this is too low to be of use but in a PV module (panel) cells are connected in series to make higher and higher voltages. In an array or system of a PV plant, modules are connected in series (a string) to produce even higher voltages. In commercial installations string voltages of over 800V are not uncommon. Through conversion of these DC voltages to AC via an Inverter, high power outputs are possible which are usable on the national electricity transmission network.
Electricity always takes the path of least resistance, hence the first use will always be on site to the home or business and then back to the grid. A monitor keeps track of the total electricity generated and, in the case of larger commercial projects, how much energy is being fed back to the grid. Those living remotely can opt for an off-grid connection, in which case batteries must provide storage for night time use.
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