Solar Energy Was America's Sole New Power Source in October

Get ready for a photovoltaic building boom. 
A solar thermal power plant (Reuters).

In October, power plants generating 530 megawatts of electricity came online in the United States. And every single electron put on the grid came from the sun, according to a report released today.

It’s possible to make too much of the fact that solar energy was the sole source of new electricity capacity in US that month. After all, the completion dates of power plants can be random. That’s particularly true for complex, multibillion-dollar, fossil fuel power stations that can take years to build and are subject to oversight by state regulators.

However, it is also possible to be too dismissive of this energy shift and the fact that solar supplanted coal and natural gas in October. It’s not a huge amount of power – at peak output 530 megawatts is what a medium-sized natural gas-fired power plant would generate. But it’s a clear sign that solar is no longer a niche play – especially when you consider that the October’s numbers don’t include the installation of roof photovoltaic panels on homes and businesses. In California alone, for instance,  19.5 megawatts of rooftop solar was installed in the territories of the state’s three big utilities just in October.

The chart below shows monthly installation statistics for rooftop solar under the California Solar Initiative, a state program to subsidize the installation of 1,940 megawatts of rooftop solar.

That only solar power plants came online in October speaks to some inherent advantages solar holds over fossil fuels – beyond not roasting the planet. One is that photovoltaic power stations can be built relatively quickly given that they essentially involve deploying thousands of solar panels over hundreds or thousands of acres of land. Photovoltaic power plants are modular, meaning that you can build them small near cities to avoid the huge costs of new transmission lines, or build them big to take advantage of economies of scale. More than half of the new solar power plants that came online in October were photovoltaic.

The rest were solar thermal projects that use thousands of mirrors called heliostats to focus the sun on a liquid-filled boiler to create steam that drives an electricity-generating turbine. Such projects more resemble a natural gas-fired power plant in their complexity and the years it takes to construct them.

But they also have an advantage over photovoltaic power plants – the heat solar thermal power plants produce can be stored to run the turbine at night and other times when the sun isn’t shining. The 250-megawatt Solana Generating Station that came online in Arizona in October, for example, is the first in the U.S. with an energy storage system that allows it to keep electricity flowing to the grid six hours after the sun sets.

And if a report issued yesterday is accurate, October will not be an aberration. The number of planned photovoltaic installations in the pipeline has grown 7% to 43,000 megawatts over the past year as developers rush to get projects online before a key federal tax credit for renewable energy falls from 30 percent to 10 percent at the end of 2016. If all were built, that’s enough electricity to power six million American homes. 

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Todd Woody is an environmental and technology journalist based in California. He has written for The New York Times and Quartz, and was previously an editor and writer at FortuneForbes, and Business 2.0.

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