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

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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
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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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

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