SunPower will add 40MW of capacity to complete the contract for the development of a 250MW California Valley Solar Ranch for Pacific Gas and Electric Company (PG&E).

The new contract adds to SunPower’s existing contract for 210MW executed in August 2008.

When complete, the solar power plant will be the first central station solar power plant in the world, SunPower said.

The plant will be built in phases, with the first phase due to begin operation in 2011.