Large, centralized PV power systems, mostly at the multi-megawatt scale, have also been built to supply power for local or regional electricity grids in a number of countries, including Germany, Switzerland, Italy and the USA
Compared with building-integrated PV systems,
large stand-alone PV plants can take advantage of economies of scale in purchasing and installing large numbers of PV modules and associated equipment, and can be located on sites that are optimal in terms of solar radiation. On the other hand, the electricity they produce is not used on-site and has to be distributed by the grid. This involves transmission losses, and the price paid for the power by a local electricity utility will usually only be the ‘wholesale’ price at which it can buy power from other sources (although in some countries such as Germany, PV power is purchased at premium prices). Large plants also require substantial areas of land, which has to be purchased or leased, adding to costs – although low-value ‘waste’ land, for example alongside motorways or railways, can be used. The land can often be used for other purposes as well as PV generation.
At Kobern-Gondorf in Germany the site is used as a nature reserve for endangered species of flora and fauna. In some large PV plants, such as the 4 MW installation at Sonnen in Germany, the arrays have been mounted at least one metre above the ground, minimizing shading to the vegetation beneath and even allowing sheep to graze beneath the panels. It would also, in principle,. be possible to have other forms of renewable energy generation alongside a large PV system, such as wind turbines – depending on wind conditions. Large PV power plants are more economically attractive in those areas of the world that have substantially greater annual total solar radiation than northern Europe. Areas such as north Africa or southern California not only have annual solar radiation totals more than twice those in Britain, but also have clearer skies. This means that the majority of the radiation is direct, making tracking and concentrating systems effective and further increasing the annual energy output. The price of electricity from such PV installations is likely to be