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Published on March 8th, 2010 | by Susan Kraemer

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Could Mixing Solar + Gas Speed Utility-Scale Solar Deployment?

March 8th, 2010 by  


A Florida Power and Light hybrid of solar and gas at the Martin Next Generation Solar Energy Center in Florida could provide a road map for helping shepherd utility-scale solar past regulatory roadblocks. Perhaps by combining solar with fossil energy plants (that are always somehow on the fast-track ) we can finally ease utility-scale solar into the marketplace.

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At the hybrid gas/solar plant in Martin, a relatively modest 70 MW heliostat solar thermal power plant – but which is nevertheless second in size only to its much larger US heliostat solar thermal prototype that totals 354 MW – SEGS, that has operated since the ’80’s in California’s Mojave – is to be grafted onto an existing natural gas plant; one that is itself the largest in the US.

The capacity of the natural gas plant has been gradually built up over the years. It comprises three 800 MW steam-generating units, two 450 MW combined-cycle units and two 160 MW combustion turbine peaking units, and now totals 3,800 MW.

However, the solar portion is large enough so that because of the size of each source, this pilot project will definitively answer the question: “But is this doable at full-scale?” Small solar projects already sometimes use a small gas turbine for cloudy days backup, but this is a first at this scale.

Larger  similar heliostat-based solar thermal projects Brightsource (440 MW) Solar Reserve (150 MW) and Abengoa (250 MW) are currently bogged down in the regulatory review pipeline in California. The difference?  Theirs are not married to natural gas plants.

Using the same heliostat solar thermal technology as is used at the 354 MW SEGS, the $476 million solar installation comprises mirrors that will rotate with the sun to concentrate the sun’s rays into a vacuum-sealed tube that contains a synthetic oil, which heats up to 748 degrees Fahrenheit. The boiling oil is then used to produce steam that is fed into an existing turbine at the gas plant to produce electricity.

The full-scale pilot test will show natural gas producers how solar could be added cheaply, reducing their greenhouse gas emissions. Because the new solar thermal project does not need to build a new steam turbine or new high-power transmission lines, (since the natural gas plant already is so equipped) these extra solar electrons are 20% cheaper than if they were built as a stand alone project.

The traditional natural gas business is dominated by fossil energy companies who find it easier to move projects expeditiously through the environmental review process because these are old established companies that know how to grease the skids. More shotgun marriages between a fossil fuel and solar might make that process speed up for utility-scale solar too.

Currently, not mere MW, but tens of GW-worth of solar projects are backed up in the approval pipeline in California alone, and many of these employ similar heliostat solar thermal mirror technology as both the SEGS original and this project. Because, like fossil electricity, they ultimately use steam to generate electricity, heliostat-based solar thermal projects are a natural marriage partner for a fossil electricity plant.

Solar, while it now supplies close to 2.5% of the California grid from rooftop PV, has made little dent in utility-scale power on the grid. This project in Florida could help change that.

And then, once natural gas peaks, the solar will still be there;  pumping out juice.

Image: Martin Next Generation Solar Energy Center

Source: New York Times

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About the Author

writes at CleanTechnica, CSP-Today and Renewable Energy World.  She has also been published at Wind Energy Update, Solar Plaza, Earthtechling PV-Insider , and GreenProphet, Ecoseed, NRDC OnEarth, MatterNetwork, Celsius, EnergyNow, and Scientific American. As a former serial entrepreneur in product design, Susan brings an innovator's perspective on inventing a carbon-constrained civilization: If necessity is the mother of invention, solving climate change is the mother of all necessities! As a lover of history and sci-fi, she enjoys chronicling the strange future we are creating in these interesting times.    Follow Susan on Twitter @dotcommodity.



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