With Germany’s coal plants scheduled to close by 2038, operators now face some major decisions about how to restructure energy systems. One idea is to convert polluting power stations into batteries. L. Michael Buchsbaum takes a look.

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Since German lignite fuels seven of the EU’s top ten pollutors, if the country is going to seriously reduce its emissions, it has to shut these polluters down—and fast. But given that coal fired plants provide roughly one third of Germany’s power, immediately closing them is not feasible.

In addition, these coal plant complexes are a crucial part of regional economies in the lignite fields west of Cologne in the state of North-Rhine Westphalia and the Lusatian coal areas southeast of Berlin in Brandenburg and Saxony. With their operating days now numbered, finding ways to keep workers employed while still generating power is a primary goal of Germany’s envisioned “Coal Exit.”

However, as power generators worldwide have moved away from coal, many plants were simply converted to burn fossil gas. That is especially true in the U.S., where (mostly) fracked gas now accounts for the largest share of electrical generation. Though arguably not any better for the environment, one benefit to fuel switching is that centralized plants can still use existing infrastructure and grid connections, and most workers keep their jobs.

But a greener idea that’s gaining traction is re-developing older power plants into giant batteries. These would hold excess renewable energy produced by solar and wind farms during peak operating times and releasing that power back onto the grid when needed. Additionally, centralized battery stations can also be seamlessly plugged into the grid, helping to balance load with demand and further taking advantage of clean production opportunities.

Batteries balance out renewable energy

Once seen as far-fetched, as the technology improves, battery demand is expected to accelerate to as much as 50 gigawatts of installed capacity globally by 2030 according to the Fraunhofer research group.

In some places, this is already happening. In Australia, several 50+ MW batteries are helping balance the grid, including the giant 100MW/129MWh Tesla supplied battery in Hornsdale.

And in the US, developers in California are now pushing for the swift construction and installation of over 300 MW of storage within the next three years. Nearby in sunny Arizona, battery supplier AES is set to install 100 megawatts of stationary storage for utility Arizona Public Service this year, the first of a whopping 850MW of planned energy storage and 100 MW of solar generation set to be installed by 2025. But though an effective strategy in the desert, can it be done here in Germany too?

Germans test out salt thermal storage

Yes! says the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt or DLR) which is currently working with Swedish-utility Vattenfall and start up SaltX to develop a pilot 10MW salt battery in the Reuter power plant in Berlin. The project involves replacing the old coal boiler with a molten salt thermal storage tank that will be heated using excess renewable energy.

Based on proven Carnot battery technology that’s already commercially available, this single pilot could be enough to prove the commercial viability of the concept. Though according to its website, DLR has been researching Carnot batteries since 2014, successful industrial experience with molten salt storage in concentrated solar power plants worldwide stretches back almost a decade. So only the application here is new.

At the Reuter plant, which supplies 600,000 households in the nation’s capital with heat, “power” now comes from calcium oxide, aka quicklime. Vattenfall and SaltX are taking advantage of the simple chemical reaction that occurs when quicklime becomes wet: as its salt-like grains soak up water, it becomes calcium hydroxide and releases large amounts of heat in the process. By removing the water again, essentially by baking it, the substance turns back into calcium oxide. Making more heat requires hitting the repeat button.

Even better, officials say the process can absorb ten times more energy than water, which is currently used for power-to-heat facilities. “If your ambition is to be fossil-free within a generation, you have to consider various alternatives to reach that,” said Simon Ahlin, a representative of SaltX. “This is a solution that’s available in a short time frame.”

Financed as a public-private initiative, if all goes well, the pilot plant could be up and running by 2022. Vattenfall is planning to run a test operation through the end of the summer.

As envisioned, similar future Carnot batteries would complement lithium-ion battery plants throughout the German grid, delivering primary and secondary frequency control services.

Pumping out clean power

In an April report, Germany’s conservative Economy and Energy Ministry accepted the feasibility of transitioning towards battery back up, but the government itself has taken no position on which type of storage technology should be pursued. However, to be fair, converting power systems on such a large scale has never before been tried, meaning multiple conversion strategies are needed.

East of Berlin, LEAG Energy, a subsidiary of Czech energy company EPH, also owns a cluster of lignite burning coal plants that currently produce about 10 percent of Germany’s overall electricity. As part of that company’s pursuit of greener solutions, LEAG has entered into a consortium with clean-energy developers Baywa r.e. GmbH as well as former plant owner Vattenfall to construct a 53-megawatt large-scale battery near the twenty-year old Schwarze Pumpe lignite-fired power station.

Along with Czech contractor EGEM and local service companies, the group has begun building their “Big Battery Lusatia” battery storage facility next to the existing plant making it the biggest of its kind in Europe and helping to ensure smooth grid operation.

Comprising 13 containers full of battery racks and spreading across an area the size of a football field, LEAG itself is investing €25 million in the new lithium-ion storage facility. The goal is to be in operation by the summer of 2020.

This is all happening in one of the regions in Germany which was been vocally opposed to the coal phase-out, because the local economy depends so much in that industry. Hopefully the new batteries will be a pathway towards a just transition.