New Concepts in Energy Storage Could Break Barriers

April 20, 2019

Sticky social question for the transition to green energy is the displacement, not only of workers like coal miners, but of existing generators, which are often major employers, and perhaps as importantly, big sources for local tax revenues in hard pressed communities.
German effort at repurposing coal plants as energy storage units could hold promise.
Add this idea to what I posted on last week, the updating of coal and other mine sites to pumped storage energy facilities – means there could be attractive opportunities to get reluctant electorates to buy into a Green New Deal type program.


The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt or DLR) is investigating whether Germany’s coal plants could be reused as energy storage assets.  
The research body, which has a track record in concentrated solar power (CSP) development, is planning a pilot that will involve ripping out the boiler from an old coal plant and replacing it with a molten salt thermal storage tank that will be heated using excess renewable energy.
If the concept works, then advocates say it could help safeguard coal generation jobs while giving Germany tens of gigawatts of storage capacity for renewable energy load-shifting on the German grid. 

Furthermore, a single pilot could be enough to prove the commercial viability of the concept, since the technology, described as a Carnot battery, is based on commercially available industrial components and standard engineering practices. 

Dr. Michael Geyer, senior adviser at DLR’s Institute of Engineering Thermodynamics in Almeria, Spain, said the center is preparing a commercial-scale pilot in association with an unnamed German utility. A feasibility study for the pilot had already been awarded, he confirmed.
Geyer explained that engineering proposals would take 12 to 18 months and construction could take another year and a half, meaning the pilot plant could be up and running within three years. The pilot is being financed as a public-private initiative, he said.   

According to its website, DLR has been researching Carnot batteries since 2014. Experience with molten salt storage in CSP plants, meanwhile, stretches back almost a decade.

This is significantly longer than the operational track record of grid-scale lithium-ion battery plants, Geyer noted. Thermal storage tanks are relatively low-tech, low-risk engineering concepts, he said, requiring only a steel tank, concrete base and the salt itself.
The principal engineering task is to fit the tank into a coal plant, he said. These plants were not designed to house molten salt storage containers, he admitted, and a Carnot battery built from scratch would likely not resemble a coal plant. 
But in Germany utilities are interested in the concept as a way of extending the lifespan of coal generation assets that have now been given a final cutoff date of 2038. Geyer said 7 gigawatts of coal generation were due to close down by 2023, rising to 23 gigawatts by 2030.
Most if not all of this capacity could potentially be turned into Carnot batteries, he said. “This is a commonsense application to make use of existing infrastructure,” he said.

6 Responses to “New Concepts in Energy Storage Could Break Barriers”

  1. Canman Says:

    The Carnot battery is undoubtedly named after Carnot’s law for the efficiency of heat engines, where the maximum efficiency equals one minus the absolute cold temp divided by the absolute hot temp. This means you’re going to lose a large portion of energy compared to pumped storage or an electro-chemical battery.

    • greenman3610 Says:

      the efficiency is not as good as pumped storage – the article notes:

      ” …the round-trip efficiency of the storage process is only about 40 percent.

      DLR hopes to raise this level to 60 percent using heat-pump technology, in a manner analogous to that being pursued by the Alphabet spinoff Malta.”

      – also you gain by using existing site and transmission infrastructure, which is an expensive piece of the puzzle.

      If you are using renewable energy, free fuel, during times when it would otherwise be curtailed, or dumped, you are creating value for pretty cheap input.

  2. greenman3610 Says:

    fyi pumped storage efficiency is 75 percent and up.

  3. sailrick Says:

    What about using silicon to store heat instead of molten salt? Silicon is the heat storage medium in the Sun in a Box system designed at MIT
    For that matter, why not use is in solar thermal (CSP) plants?

    MIT’s conceptual “sun-in-a-box” energy storage system plugs into molten silicon

    there are a few problems with salt as a storage medium – for one, it becomes quite corrosive when the heat is cranked up.

    Salt tops out at about 1,000° F (538° C), after which its damaging effects become too problematic. So the MIT team looked for a new material that could store more heat, which in turn raises the energy density of the system. They eventually settled on silicon, which can be heated to over 4,000° F (2,200° C) and is abundant to boot.

  4. dumboldguy Says:

    So let’s hurry up and build some, although it seems like throwing rather smallish snowballs into the gates of hell.

  5. rhymeswithgoalie Says:

    The research body, which has a track record in concentrated solar power (CSP) development, is planning a pilot that will involve ripping out the boiler from an old coal plant and replacing it with a molten salt thermal storage tank that will be heated using excess renewable energy.

    One of my sisters works as a design engineer for industrial plants which require usually custom configurations of expensive* pipes, pumps and valves. Molten salts require touchy ceramic or super-high-grade lined metal plumbing, and costs for increased maintenance and inspection should be taken into account (i.e., costs which are unlikely to drop much on the transition from prototyping to common use). At least molten salts are not toxic to humans.

    *Which is one reason I like waterless PV/wind technology: No industrial plumbing to design and maintain.

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