STEAG large - scale battery systems for a more reliable power supply
With the transition to sustainable energy, the proportion of renewable energy sources within the electricity mix in Germany continues to grow: plans call for 55 to 60 percent renewable energy by 2035. This is good news, but also leads to increasingly large fluctuations in the power supply. These fluctuations need to be quickly evened out. To make this possible, STEAG is breaking new ground: by early 2017, we will have invested 100 million euros in six large-scale battery systems—without taking any subsidies. In order to ensure a certain distribution across the grid, large-scale battery systems are being built at six STEAG sites in Germany: Lünen, Herne, and Duisburg-Walsum in North Rhine-Westphalia as well as Bexbach, Völklingen-Fenne, and Weiher in Saarland. Here you can learn about what these systems do and why they will be increasingly important to a reliable power supply in the future.
How fluctuations in the power supply occur
Fluctuations in the power supply occur when the total electricity being fed into the grid differs from the current level of consumption. The increasing proportion of renewable energy sources within the electricity mix in Germany has caused these fluctuations to increase, since the production of solar or wind energy is uneven and cannot be precisely predicted. Sunshine and wind don’t always follow forecasts. Unexpectedly higher or lower consumption, errors in the daily forecasts of electricity needs, and power plant failures can lead to fluctuations in the power supply. Then, suddenly more or less electricity is available than is used, and the frequency deviates from the target of 50 hertz.
Why these fluctuations need to be evened out immediately
If the fluctuation in the power supply is ten millihertz or more, it must be immediately evened out so that the power supply remains stable. This is called “load regulation.” An unstable power supply could cause damage to electrical systems, such as machines in industrial plants or technical equipment in the electrical grid. This could result in the dreaded blackout, a total failure of the electrical grid.
How fluctuations in the electricity supply are evened out
The operators of Germany’s nationwide transmission system (Tennet TSO, 50Hertz Transmission, Amprion, and TransnetBW) have the responsibility of constantly maintaining the load balance between electricity generation and consumption and thus guaranteeing the stability of the power supply. This is the purpose of the operating reserve, which is put out to tender every week and kept available by the providers. If not enough energy is fed into the grid, the power line frequency falls under 50 hertz, and energy must be fed in (positive operating reserve); if too much energy is fed into the grid, the power line frequency rises above 50 hertz, and energy must be taken out of the grid (negative operating reserve). In Germany there is primary and secondary reserve power as well as minute reserve power. Primary reserve power must be made available in the required amount within 30 seconds, secondary reserve power within 5 minutes, and minute reserve power within 15 minutes.
How our large-scale battery systems will help with load regulation in the future
In order to provide primary reserve power, which is put out to tender every week by the transmission system operators, at STEAG we are breaking new ground for the future. Until now, primary reserve power has been provided mostly by conventional power plants. For the first time, we will be rolling out major installations of large-scale battery systems to provide this reserve power. Within seconds they can even out frequency fluctuations in the power supply by feeding energy into the grid when the frequency is too low, or by storing energy when the frequency is too high. These systems will meet all the currently valid criteria for the performance of battery storage systems used for primary reserve power—including minimum up times of over 30 minutes. In developing these new large-scale battery systems, we were able to draw on our experience with the LESSY battery system as part of a research and development project with Evonik and other partners. With the LESSY system installed at the Völklingen-Fenne power plant, we were one of the first providers to use a large-scale battery (with a capacity of one MW) for primary reserve power from February 2014 through February 2016.
Why primary reserve power needs to be available for 30 minutes
Primary reserve power is the “backbone” of load regulation: it needs to be available for at least 30 minutes so that even during major disruptions with long-lasting fluctuations the power supply can be maintained and safe and stable operations can be restored. This has been confirmed by simulations by STEAG using actual major disruptions as examples—for instance, the blackouts that resulted from shutting off two high-voltage lines over the river Ems in 2006 to allow a cruise ship to pass underneath.
How our large-scale battery systems are structured
As with portable electronic devices, large amounts of energy require multiple batteries. Our large-scale battery systems work very similarly: basically they are giant, rechargeable lithium-ion batteries that can be linked via a control center. When partially charged, they are ideal for providing primary reserve power. Each large-scale battery system consists of ten containers with a total capacity of 15 MW—more capacity than is offered by any previously installed system in Germany. In total, by early 2017, we will have built six systems with a capacity of more than 120 MWh—more than the total of all other systems with the same technology. This storage capacity could theoretically provide power for 300,000 households for one hour.
How our large - scale battery systems are manufactured
Our large-scale battery systems are a German-French-South Korean coproduction. The containers with the technical systems are built and pre-configured by the industrial systems specialist Nidec in France, while the battery cells and modules are manufactured by LG in Ochang, South Korea. A specialized manufacturing process ensures that the JH3 lithium-ion battery cells are compact as well as very safe and stable. A certain number of battery cells is assembled into a module. Each module has a protective circuit as well as a management system that monitors the status of the batteries. Then the battery modules are brought to the various installation sites by ship and truck. During this process, certain temperatures need to be strictly maintained so that the batteries are not damaged. At each site, racks of 17 battery modules are assembled, which are installed in the containers and connected.
The environmental advantages of our large-scale battery systems
Until now, primary reserve power has been provided mostly by conventional power plants, which increase or decrease power production depending on whether energy needs to be fed into the grid or taken out. However, they need to generate a certain minimum load for the entire week during which they are required to operate, and so they burn coal, oil, or gas. This is not the case with our large-scale batteries. Thus, along with providing the necessary storage capacity to integrate renewable energy sources, we make a valuable contribution to protecting the climate and conserving resources.
Why large - scale battery systems will become increasingly important in the future
As conventional power plants are gradually taken from the grid in the near future, load regulation will likely have to take place for an increasing number of hours of the year almost without any conventional power plants. By then at the latest, large-scale batteries will be a very efficient, cost-effective, and in our view indispensable alternative to today’s conventional power plants for primary reserve power and a reliable power supply.
As part of the transition to sustainable energy, large-scale batteries will be able to take on additional responsibilities in the future, such as ensuring power supply in decentralized grids, which are becoming increasingly important. Here, too, large-scale batteries can even out differences from fluctuating amounts of power fed into the grid and consumed. Decentralized grids will thus become more independent of the national high-voltage grid, which will reduce the need to expand this grid.
As it brings six of these large-scale battery systems online, STEAG is pioneering a major step into the future of energy.