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The Ivanpah Solar Electric Generating System officially came online on February 13, becoming the world's largest source of solar power. With a capacity of 392 megawatts, the solar system will be able to generate enough power for 140,000 homes in California. The $2.2 billion Ivanpah project is located in the Mojave Desert and is a joint venture by NRG Energy (NYSE:NRG), Google, and Brightsource Energy. Secretary of Energy Ernest Moniz toured the plant today with NRG CEO David Crane.

Ivanpah uses concentrated solar power (CSP), which uses hundreds of thousands of mirrors to reflect the sun toward a tower. This heats a boiler in the tower, which creates steam to drive turbines and make electricity.

The project received a $1.6 billion loan guarantee from the U.S. Department of Energy, helping the project developer, Brightsource Energy, to finance the project. Ivanpah is seen as a milestone for the solar power, as it can consistently generating electricity on a large-scale. It is also a sign of progress for the solar industry, which is rapidly growing and bringing down costs. Although solar power only makes up about 1% of total electricity generation, it now employs 140,000 people, more than the coal industry's almost 90,000.

Yet future growth in solar will likely not come from CSP technology, which is expensive and requires a lot of land. Ivanpah fought for years with environmentalists concerned about the effect on desert wildlife. Replicating projects on the scale of Ivanpah is probably not likely, particularly in areas with greater densities of people and less sun exposure. Instead, rooftop photovoltaic solar power may be the preferred technology, generating solar on site without the need for long distance transmission. Costs for rooftop solar are rapidly declining, and will likely grow exponentially in the coming years. However, the speed at which solar expands will depend on incentives from Congress, many of which are set to expire in 2016.

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