Concentrated solar power with thermal energy storage can help utilities' bottom line, study shows

Dec 21, 2012

(—The storage capacity of concentrating solar power (CSP) can add significant value to a utility company's optimal mix of energy sources, a new report by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) suggests. 

The report found that CSP with a six-hour can lower peak net loads when the sun isn't shining, enough to add $35.80 per megawatt hour to the capacity and operational value of the utility, compared to photovoltaic (PV) solar power alone, and even higher extra value when compared to CSP without . The net load is the normal load minus variable renewables such as photovoltaic and wind.
The additional value comes because thermal storage allows CSP to displace more expensive gas-fired generation during peak loads, rather than displacing lower-priced coal; and because it can continue to flatten the peak load in the evenings when PV isn't contributing to the mix because the sun has set.
The report, "Simulating the Value of with in a Production Cost Model," by NREL's Paul Denholm and Marissa Hummon, noted that the $35.80 per megawatt extra value would come in a scenario in which there is relatively high penetration of renewables into the utility's mix, about 34 percent. If the penetration was lower, the extra value would be lessened.
The authors simulated grid operations in two balancing areas primarily in Colorado. NREL is also using the same methodology it developed for the Colorado scenario for the more complex California system controlled by the California Independent System Operator. A report on the value that CSP with thermal storage adds to the California system is expected early next year.
The Colorado study marks one of the first times that the operational and capacity value of CSP with thermal storage has been evaluated using a production cost model, a traditional utility planning tool.
The NREL authors employed Energy Exemplar's PLEXOS simulation model that allowed them to isolate the relative value of storage (TES) with and without storage.
CSP with TES, with an ability to store thermal energy in, say, molten salt, can use its heat-energy to drive turbines at power plants over much longer stretches of the day.
"We've known for a long time that CSP with storage adds significant value, however, we are now able to quantify this value in the language utilities understand," said Mark Mehos, manager of NREL's Concentrating program.
Compared to other renewable options, at high penetration levels CSP with TES can be dispatched to displace natural gas rather than coal. This is important because electricity produced from natural gas fired generators is typically more costly than that produced from coal.
"With CSP with thermal storage, you aren't diving as deep into the generation stack, displacing cheaper and cheaper fuel," Denholm said. "You're always displacing the highest-cost fuel."
Also, CSP with TES can lower peak net loads in the evenings when electricity use can still be high, but PV isn't available. So, it helps utilities offset the need to build new gas-fired generators in order to meet the electricity demand when the sun goes down.
"CSP with can continually reduce that peak demand as the peak moves into the evening," Hummon said. "It continually maintains a high operational value and high capacity value."

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3 / 5 (2) Dec 21, 2012
The conclusions of the study are flawed and slanted to justify the use of higher cost RE. If the RE mix was 34% or higher, natural gas peaking would be used for peak periods when the sun isn't shinning. Therefore more costly than thermal storage. But below the 34%, other load following fossil plant can perform peaking functions less expensive than thermal storage which by the way is an additional cost on top daytime cost of solar.
2.3 / 5 (6) Dec 21, 2012
Everyone is an idiot, and they still are not understanding how this works.

The only "daytime costs" for solar are labor and maintenance costs, which you have for ALL industrial/commercial power plants anyway.

The "fuel cost" is zero with solar.

If the only thing you did was run a CSP plant during the day with no storage, you'd still save about half the coal consumption.

Consider this, if hydroelectric dams ran only during the day, would they be useless? No. They'd still offset half as much other fuels anyway, and the fuel cost would still be zero.

The way they go wrong is they are looking at this as a "five year model" and you really need to think in 10 years or more. The syste pays for itself because you never buy fuel. And it pays for the fuel equivalent every year, and it turns out the system costs about as much as 5 to 10 years worth of FUEL ALONE would cost for the Coal system. What this means is that in the 5 to 10 year range the solar system is cheaper.
2.3 / 5 (6) Dec 21, 2012
After 5 to 10 years, the CSP system should be only a tiny fraction of the coal power cost, because you can't get ride of maintenance and repairs no matter what.

Do some maths at realistic efficiencies. If you must buy 40MW worth of coal for an entire year, (and to compare apples to apples use only 12 hours per day so we compare on the time solar normally effects,) what you will find is the COAL ONLY for a year or two costs as much or more than the entire solar plant costs to design, build, and install.

The coal plant requires boilers, turbines, and maintenance too.

But every year's worth of coal fuel costs just as much as the entire plant costs to build, and somehow people don't figure that into the real long-term cost of operation of solar, which is in fact 1.5 to 2 orders of magnitude LESS than Coal.

Now you can't reduce transmission because you need lines and such, but I'm sick of the lies claiming solar somehow costs more than Coal. It's bullshit.
1.8 / 5 (8) Dec 21, 2012
Hi Lurker2358.

Heartily agree.

Add to that the fact that fossil fuels will soon enough become more dear and more difficult/dangerous to mine, transport and burn, and solar becomes infinitely more practical/cheaper for the longer term, especially as the sunlight does not get more expensive to 'get' as time goes on like fossil fuels do (if anything, improved technologies will reduce costs/increase efficiencies of solar as time goes on).

Kudos for bringing some sanity/objectivity to the discourse. Cheers and have a safe holiday season, Lurker, everyone!
4 / 5 (4) Dec 21, 2012
For one the capital costs must be amortized and then there are regulatory and administrative costs among others.

I was Project Manager with engineering and construction of the world first utility scale solar stations at Kramer, developer of several csp solar power plants and have a solar direct steam Patent. So tell me who is stupid?
4 / 5 (4) Dec 21, 2012
First I said the report was flawed and pointed out the flaws. I did not say I was against solar. But it appears there are too many fanatics out there that want to ambush meaningful discussion and throw around insults
3 / 5 (2) Dec 21, 2012

My solar direct steam patent is being incorporated in China and SE Asia and under study by NREL in the US. Yes i can see the costs coming down