Large grid-connected PV systems can provide the energy needed by many customers. In urban areas, PV arrays are commonly used on rooftops to supplement power use, feeding power back into the grid. In rural areas, they may be the sole source of electricity, used to directly power DC equipment or to charge a storage battery. Large PV power stations can cover tens or hundreds of hectares and have outputs of up to hundreds of megawatts. The drive to reduce GHGs and increase the sustainability of power supplies is leading many governments to offer incentives for solar energy to improve the return on investment, with attractive feed-in tariffs available for private installations connected to the grid. PV cells are made from layers of semi-conducting material, usually silicon. When light shines on the cell it creates an electric field across these layers. The stronger the sunshine, the more electricity is produced. Groups of cells are mounted together in panels or modules that can be mounted on a roof. Each panel is rated by its DC output power measured in kilowatts peak (kWp). This is the rate at which it generates energy at peak performance in full direct sunlight during the summer. The efficiency of a panel determines the area needed to produce the same rated output: an 10% efficient panel will have twice the area of a 20% efficient panel with the same rating. An inverter is used in order to convert the DC output to AC to feed into the grid, which reduces the efficiency further. The biggest challenge the industry faces is to deliver higher efficiencies at affordable cost, and several companies have begun to embed ICT electronics into PV modules in order to optimise performance.
There are a number of systems available for improving the output of solar PV arrays by ensuring that the maximum possible electricity is generated from the available sunshine. These include: