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Wind and solar farms do not generate enough electricity at all times and in all weather conditions. Germany's energy transition hinges on the storage of power from renewables — and batteries come to the rescue.
In Germany, 42% of total electricity generation comes from renewable sources. Nuclear energy accounts for a little over 12% of the mix, with 28% of the total coming from coal-fired plants.
As the country's energy transition takes its course, coal-fired stations are to be closed down by 2038 at the latest. These are the very power plants that have so far reliably balanced all power grid fluctuations.
After all, wind and solar farms cannot always provide the required amount of electricity around the clock because of weather and seasonal conditions.
But when renewables provide more than enough power at any given time, it ideally needs to be stored for a rainy day. To do that, numerous companies bank on huge battery facilities using old or new batteries from electric vehicles. Three such facilities are located in the western German state of North Rhine-Westphalia.
Even a small line frequency drop from 50 hertz to 47 hertz can have serious consequences for Germany's power grid and can potentially lead to blackouts. They could occur during protracted periods of weak winds and overcast skies in the winter months, meaning that not enough power comes from solar and wind farms while demand remains high.
This is why high-capacity battery storage facilities are viewed as an essential component of a successful energy transition leading to a larger use of renewables. "Such storage technology has a big potential," Alexa Velten from service provider EnergyAgency.NRW told DW.
It's technology that pays off for operators. Excessive power from renewables can be bought at relatively cheap prices and sold on-demand with a good profit.
Velten says it takes no longer than an hour to get a capacity of 12 megawatt-hours. It can be fed into the grid just as fast and almost nothing gets lost in between. "The self-drain rate of such a storage facility is only about 4% to 5% per month."
Munich-based system developer The Mobility House (THM) is heavily involved in such storage projects. At Werdohl-Elvering, on the premises of an abandoned coal-fired plant, THM and its partners such as Daimler combined 2,000 lithium-ion modules from 600 Smart electric cars to create a power storage plant with a capacity of 10 megawatt-hours.
Decommissioned power plants provide the infrastructure that huge power storage facilities need, above all the existing power lines. North Rhine-Westphalia has a lot of such sites and is therefore well-suited for storage facilities.
German utility RWE has made use of the existing power line infrastructure at Herdecke, formerly home to a pumped-storage power plant. The company has meanwhile installed a battery array with a capacity of 7 megawatt-hours.
Yet another storage site is at Lünen where waste management company Remondis helped build a capacity of 13 megawatt-hours from 1,000 used car batteries.
Here they use batteries from Tesla, so-called second-use batteries, which the carmaker had originally built for the first E-Smart. Alexa Velten says the use of these old batteries in a storage facility "extends their lifespan by up to 10 years." Only after that do they have to be recycled.
But they have to be recycled at some point, explaining Remondis' interest in the project — the batteries contain a number of precious rare earths.
Whether first-use or second-use batteries — they are both able to store power from renewables. Their demand is bound to soar as more and more coal-powered plants are taken off the grid in Germany.
At the same time, the search for alternative raw materials for the production of batteries continues unabated, according to Velten. This is because the rare earths needed right now to produce lithium-ion batteries are not just rare but also very expensive.
This article was adapted from German.