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Published on February 14th, 2014 | by Tina Casey


Giant Solar Battery Made Of Salt (Almost) Ready To Charge Up

February 14th, 2014 by  

It basically runs on salt but nevertheless Crescent Dunes, the new 110 megawatt solar power and energy storage facility near Tonopah, Nevada, is billed as the “most advanced solar plant in the world” on top of laying claim to being the largest facility of its kind in the world. Now that construction is complete, the commissioning phase is under way so this is a good time to catch up and see what all the excitement is about.

We’re particularly interested in this project because we helped finance it and so did you, if you pay federal income tax. We’re not talking Kickstarter or Indiegogo either. In 2011 we taxpayers backed a $737 million Department of Energy loan to SolarReserve, the project developer.

That puts you and me in the same league as other project investors, the global engineering firm ACS Cobra and the financial services giant Santander, which was named “Sustainable Global Bank of the Year” last year. Not bad, right?

Crescent Dunes molten salt solar power plant

Crescent Dunes courtesy of SolarReserve.

The Salt Battery

Now, about that salt battery. Crescent Dunes represents the next generation of solar power plants, in which integrated thermal energy storage in the form of molten salt enables the plant to keep churning out electricity long after dark.

The storage feature enables the plant to smooth out spikes that are characteristic of solar energy, not only day-night cycles but also smaller bumps like weather and cloud cover.

Go ahead and pat yourself on the back for this one, too. Our Energy Department laid the foundation for cost-effective molten salt energy storage for solar power plants back in the 1990’s with two demo plants using a “solar salt” composed of sodium nitrate and potassium (you can read all about it in this 2013 NREL report on molten salt).

The Crescent Dunes Solar Energy Project

In terms of efficiency, Crescent Dunes represents a step up from the demo plants. More than ten thousand ground-mounted mirrors called heliostats collect solar energy and focus it on a central tower, where molten salt is circulated. The heated salt goes down to power a steam turbine, which generates the electricity.

The molten salt also serves as a “salt battery,” storing energy in the form of heat. When the heliostats are not contributing fresh solar energy, retained heat in the molten salt will continue to produce enough steam to generate electricity for about six hours.

With construction complete, the initial shakedown phase currently under way includes energizing the grid connection and other electrical systems. The heliostats are also undergoing the first stages of calibration for maximum efficiency.

The next steps include a number of stages that are common among conventional power plants, including revving up pathways for water, air, steam, and cooling.

SolarReserve points out, though, that among other differences the dry cooled condenser sported by Crescent Dunes will result in far less water consumption than conventional steam power plants.

The plant is expected to get up to speed later this year and when it does, the utility NV Energy already has dibs on 100 percent of its 500,000 MWh per year, which is enough electricity for 75,000 homes during peak periods.

US Solar Industry Races Ahead While Fossil Fuel Infrastructure Crumbles

Not for nothing, but while we’re on the subject of record-breaking solar power plants supported by us taxpayers, just yesterday the Energy Department held a dedication ceremony for another showpiece for US solar tech leadership, the Ivanpah concentrating solar power plant in California.

Facilities like Crescent Dunes and Ivanpah are not impact free, of course, especially when it comes to the construction supply chain.

However, there is no disputing the fact that once they are up and running, solar facilities do not require the kind of destructive energy harvesting operations required of fossil fuel power plants, and they do not produce the emissions that result from burning fossil fuels.

A recent series of events involving the fossil fuel infrastructure also underscores another indisputable fact, which is that infrastructure crumbles.

There are always going to be infrastructure episodes even under a best case scenario, where ample public and private resources are dedicated to efficient monitoring, troubleshooting, maintainence, and repair.

There is increasing evidence, though, that the US fossil fuel infrastructure has not been attended to, and it’s not getting any younger. Examples from the past few weeks include the Elk River coal washing chemical spill, the Dan River coal ash spill, the Kanawha River coal slurry spill, and a huge gas explosion in a Louisiana-to-New-York gas line that  put an entire rural Kentucky county in a state of emergency (fortunately with no lives lost — imagine if that had happened in a more populated area…).

Speaking of gas, hop on over to the Journal of Science and take a look at some research on what’s been leaking out from our aging natural gas infrastructure (h/t: grist.org).

As for oil pipelines, cleanup is still continuing with no end in sight from the 2010 Kalamazoo River oil spill (the largest ever inland oil spill in the US), and last we heard oil is still being found in a 12-acre cove after last year’s Lake Conway oil spill.

And don’t even get us started on fossil fuel disasters related to rail transport.

The point is, when you take infrastructure risks into account, it’s all the more clear that the US cannot sustain a fossil fuel economy for much longer.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

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