The largest single site solar power plant in Europe hit the grid in late 2010: Rovigo, Italy (Photo: SunEdison)
In 2010 large scale photovoltaic (PV) plants with a cumulative power of more than 2 GWp (Giga Watt / Peak) were connected to the grid. Market leader was Germany with more than 1 GWp new power capacity installed, closely followed by Italy and the Czech Republic. Among Asian countries it is worth to mention China with several large scale PV power plants put into service.
The largest solar power plant in the world went online in Canada: The Sarnia Solar Project, which sees 1,3 million modules spread over 950 acres of land, has the potential to supply the energy needs of up to 12,800 households. It produces 80 megawatts of energy.
In Rovigo, Italy, Europe's largest PV site joined the grid in November 2010. SunEdison, a subsidiary of the silicon wafer manufacturer MEMC Electronic Materials, is right by claiming to run the biggest site, but even it admits the claim comes with a qualifier by calling the 70-megawatt plant "Europe's largest single site solar farm." Brandenburg, Germany's Finsterwalde Solar Park, for example, is considered by many to be Europe's largest solar PV plant. But it is technically a series of three interconnected plants referred to as Finsterwalde I, Finsterwalde II, and Finsterwalde III. Together they make up 81 megawatts. While Spain is also known for its aggressive adoption of solar power, the country contains mostly solar farms in the 10- to 30-megawatt range. Olmedilla Photovoltaic Park, currently Spain's largest solar PV farm, produces 60 megawatts.
A detailed overview and description of the world's largest solar electric installations is available here. One thousand PV plants are included in the list – the power range spans from 2 MWp to 97 MWp. The cumulative power of PV systems presented is more than 5800 MWp and increases very fast.
Wikipedia also has a good overview of the largest PV sites in the world.
Energy Union supports the drive for large scale solar power plants to support Intelligent Energy.