The definition
		The word “photovoltaic” comes from the prefix “photo” which means light and the word “voltaic” derived from the name of the person who invented electric batteries, the Italian physicist Alessandro Volta. Photovoltaic is therefore synonymous with “photo-battery” and is therefore a device which transforms light into electrical current. Photovoltaics have been around for a long time, for it was in 1839 that French physicist Antoine Bequerel discovered the photovoltaic effect.

		The cell
		A photovoltaic cell directly converts part of sunlight into electricity. A photovoltaic cell is made up of two layers of a semi-conductor material – silicon – with internal metal contacts to collect the energy released. One layer of the silicon is N-type silicon (negative doped) and the other is P-type (positive doped), creating electrical current when the photons from the sunlight knock the electrons into a higher state of energy. When light (photons) hits the silicon in the solar cell, it frees electrons from the metal. The electric field allows electrons to flow from the P side to the N side and pass through an external current path back to their original side. This electron flow provides the current.

		Materials
		Silicon, a raw material that is abundant on earth, is the main component used to make photovoltaic cells. There are several types of silicon: Single-crystal silicon is very pure and provides efficient conversion, with up to 14% of the captured energy turned into electricity;  Polycrystalline silicon is less pure and less energy-efficient, with up to 12% conversion efficiency;  Amorphous silicon is much less pure and provides up to 8% efficiency. The current photovoltaic cells used to produce electricity are primarily made of single-crystal and polycrystalline silicon and are mounted in rigid glass panels. However, amorphous silicon technology, used in solar calculators and watches, is highly suitable to the logistics warehouses GSE builds, due partly to the following characteristics: Flexible slope and orientation conditions, Less sensitive to low and diffuse light conditions, Flexible material, Low weight, Not subject to wind influences, An integral part of building design and construction.

		The photovoltaic power station
		... also called a photovoltaic generator, is characterised by the peak capacity (Wc) which is the maximum power developed in optimal sunlight conditions. Several photovoltaic modules (or panels) connected into an array,   Several strings (lines of arrays of modules) connected in parallel arrangements,  A separate support structure for the modules on top of the roof (such as the photovoltaic membrane or metal casings for example),  An inverter, which converts direct current from the PV modules into alternating current,  A circuit-breaker and a production meter, And batteries, for off-grid isolated sites.

		The application
		Photovoltaic power supply systems provide electrification for isolated sites, such as hikers’ huts in the mountains, farm buildings and other activities or dwellings which are far from the electrical grid. But today, a photovoltaic power station also means producing electricity for sale to the grid. This PV-supplied energy goes back to the electrical grid as part of its supply based on the terms of a purchase contract set up with the distributor. This application is growing due to the European policy on Renewable Energy development.

		How it works
		Within this scope, the photovoltaic modules produce direct current which is transmitted by cables to the inverter which converts it into alternative current before sending it to the distribution grid through a circuit-breaker and a meter. This electrical production is sold, based on the purchase contract set up with the grid manager. In France, the contract is reached with EDF for a 20-year period. The European Union’s objective is to have photovoltaic energy contribute to 20% of the electricity production in France by 2020.

Nazca, the GSE group subsidiary, designs and builds turnkey building-integrated photovoltaic power supply systems on rooftops for industrial and logistics buildings. + more info on the GSE site...