It's been a big summer for concentrating solar power in California. After years of waiting for regulatory approval, a number of CSP plants have been cleared for development by the California Energy Commission. The latest is a four-site, 1 GW development of parabolic troughs from Solar Millennium.

The CEC approval of the Blythe Solar Power Project comes weeks after a 250-MW plant from NextEra Resources received approval. Solar Millennium still needs to get the green light from the federal Bureau of Land Management. If given the go-ahead in October as expected, construction could begin by the end of the year. If ground is not broken, the project will not qualify for the grant program that expires on December 31.

There are another six projects in California worth 3 GW that are on the BLM's “fast track” list for approval. If constructed in the next few years, they will be the single biggest factor in getting California to its ambitious target of 33 percent renewable energy by 2020.

Keep posted for more announcements. This fall is likely to be a busy one for regulators and CSP developers as they try to get steel in the ground before the end of the year.

Below is an overview of the Solar Millennium parabolic trough technology.