Two large mirror array solar generation stations are under development in California that will become the world’s largest solar farms with a combined capacity of 800 MW.

An array of mirrors covering the surface of an 11m diameter dish focuses solar energy on the receiver end of a Stirling engine using hydrogen as the working fluid. The internal side of the receiver then heats the hydrogen, which expands driving a piston, crank shaft, and drive shaft assembly connected to a generator.

A 500 MW, 20,000 dish array in the Mojave Desert northeast of Los Angeles is to sell its output to Southern California Edison (SCE) under a 20-year deal recently approved by the California Public Utilities Commission (PUC). SCE has an option to expand the project to 850 MW.

A second 300 MW array will be located near San Diego with output contracted to San Diego Gas & Electric (SDG&E) under an initial 20-year agreement. SDG&E has options on two future phases that could add up to 600 MW to the 12,000 dish array located in the Imperial Valley of Southern California.

Made by Stirling Energy Systems (SES) in Phoenix, Arizona, the first farm is due to begin operations in 2009.