New Report Finds Thermal Energy Storage Could Add Value To Solar Energy

June 11, 2014 by  
Filed under Green Energy News

Concentrating Solar Power

Published on June 10th, 2014
by Tina Casey


A new report from NREL, the National Renewable Energy Laboratory, could help spur the development of more utility scale concentrating solar power plants with thermal energy storage features while boosting the market for solar cells, too. The report indicates that CSP/energy storage projects could add value to utility scale solar energy in California, and they would enable more solar cell development by creating additional grid flexibility.

California’s ambitious renewable energy goal for 2020 also plays a key role, so keep in mind that the NREL added-value findings for thermal energy storage are transferable to only to other states with similar aspirations.

Concentrating solar power with thermal energy storage (courtesy of SolarReserve).

Concentrating Solar Power With Thermal Energy Storage

We’ve been having a lively discussion about concentrating solar power over here at CleanTechnica (not quite as lively as the fuel cell discussion, but whatever), and the new report adds another wrinkle.

For those of you new to the subject, concentrating solar power (CSP) typically works by using mirrors to literally concentrate solar energy onto a narrow field containing a system of pipes. Liquid in the pipes is heated and circulated to an electricity generating station, where it boils water to run a steam-powered turbine.

The objections to CSP focus on cost (it’s expensive) and simplicity (it’s not) compared to directly converting solar energy to electricity with photovoltaic cells.

The advantage of CSP, though, is that once the liquid is heated you have a readymade “battery” for storing heat, aka thermal energy storage. If you can figure out a way to keep the liquid hot for several hours after sundown, you can still run your solar-powered generator in the dark (the new Crescent Dunes CSP plant in Nevada, for example, uses a molten salt thermal energy storage system).

The New NREL CSP With TES Report

The new NREL CSP with TES (thermal energy storage) report is called “Estimating the Value of Utility-Scale Solar Technologies in California Under a 40% Renewable Portfolio Standard.”

In a nutshell, NREL found that when you compare the CSP/TES combo to variable technologies (yes we mean you, wind and solar), you get an increase in value of five cents per kilowatt hour.

That’s assuming California meets its mandatory 2020 renewable energy goal of 33 percent and includes a lot of wind and solar in the mix, especially distributed solar.

If you boost the goal to 40 percent, which Governor Jerry Brown sees as a possibility, NREL arrives at an added value of six cents per kilowatt hour.

The key point to keep in mind is that the CSP technology alone is not doing the heavy lifting. The difference is the inherent ability of CSP plants to transfer solar energy into stored energy. Here’s how NREL runs it down:

Concentrating solar power (CSP) with thermal energy storage (TES) is a unique source of solar energy in that its output can be shifted over time and also controlled in response to system operator signals, allowing for provision of a wide range of grid services.

That also dovetails with the other key point, which is that the CSP/TES combo adds value relative to wind and solar sources that don’t have energy storage. The more variable energy sources that enter the grid, the more valuable your storage capabilities become.


A similar storage/value dynamic is also at play in the conventional energy field, as electricity consumers seek to avoid grid brownouts, outages, high peak rates, and extra demand charges by storing grid-supplied energy on their own property.

With that in mind, the picture for CSP/TES could change somewhat as new, more cost-effective forms of standalone solar and wind energy storage systems come into the utility-scale and distributed markets, so stay tuned.

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About the Author

Tina Casey 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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  • We have used this technology in the UK for the Award winning, Zero Carbon building, Solar House, which uses an earth energy bank to store the energy for use at a later point during the year when your hot water demand is more than that being produced. @newformenergy

  • From the cited NREL report executive summary:

    “Additionally, while this analysis provides insight into the value of CSP-TES providing grid flexibility it does not examine the role of such flexibility in enabling greater penetration of wind and solar PV. Further analysis is needed to examine the portfolio benefits of CSP in meeting higher penetrations of variable generation resources.”

    The second sentence is key. That is what green billionaires are for. To fund follow up market and marketing studies on renewables like CSP v. PV. I have a big jar full of coins on my dresser and highly doubt there is a billion dollars in there. Maybe $50. There’s always a business consultancy willing and able to do studies. Fifty dollars would pay for the first quarter hour of a consultant’s time. Anyone know any billionaires?

    Nicely written. I always thought it was cool that Golden, CO was home of Coors, Colorado School of Mines and NREL. Coors family is kind of conservative. Like really kind of. Mines is, well, about minerals exploitation. So one of those things is not like the others.

  • The NREL report goes into the Sybil Fawlty file (“special subject : the bleeding obvious”). What’s new here is the estimate of added value: 5c a kwh. This is enormous, as utility pv solar goes for around that. Storage doubles the value. The incentives will have to be rejigged to give a very large premium to despatchable capacity from CSP+S and geothermal.

    Note that unlike pv, CSP really does depend on a sunny climate: US Southwest, Andalusia, North Africa, Australia. It’s no good in Northern Europe.

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