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  • We maintain the heartbeat of the grid

    STEAG is investing 100 million euros in six large-scale battery systems for primary reserve power through early 2017.

    It all started just about 80 years ago here in the western part of Westphalia: Lünen is the oldest STEAG site. It has two hard-coal-fired power plant units for generating standard 50 hertz current. One of them can directly produce the 16 2/3 hertz electricity required by German Railways through a traction power system. On the grounds of the plant, STEAG also is working on the future of energy supply: since the end of March 2016 the site accommodates the first of six large-scale battery systems. Their task is to even out the increasing fluctuations in the power supply within seconds. But how do these fluctuations occur at all? And why is it important to even them out immediately to ensure reliable power supply?


    “Provision of primary reserve power is of central importance for reliable power supply. In a sense it's the 'Champions League' of load regulation – and STEAG shows that new technologies can compete at the top of the league.”

    Christian Karalis, project manager STEAG

    Stable energy supply for the transition to sustainable energy
    The share of renewables in the German energy mix is increasing more and more in the course of the transition to sustainable energy – by the year 2035 it is expected to be 55 to 60 percent. From the viewpoint of environmental protection this is good news. However, more and more often the result is that the frequency in the power supply grid fluctuates around the target value of 50 hertz – because the production of solar or wind energy is unsteady and cannot be exactly forecast. Fluctuations in the power supply must be evened out immediately to ensure that the grid remains in stable condition and major system outages do not occur. For the purpose of this load regulation the operators of the transmission system (in Germany the companies Tennet TSO, 50Hertz Transmission, Amprion und TransnetBW) use the so-called operating reserve. We distinguish here between primary reserve power, secondary reserve power and 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 (further information is available at www.regelleistung.net). Primary reserve power is the “backbone” of load regulation – and consequently is the key to reliable power supply today and in future.

    Balanced within seconds
    The primary operating reserve is put out to tender every week by the transmission system operators. STEAG can provide this reserve in future even more efficiently while conserving resources. Within seconds, the large-scale battery systems can take up energy from the grid or feed it into the grid, fully automatically. Fluctuations caused by renewable sources of energy or by power plant failures or fluctuations in consumption then are compensated, and the frequency levels out again at 50 hertz. This makes the large-scale battery systems from STEAG an essential element in the implementation of the transition to sustainable energy. In developing the new systems, STEAG was able to draw on the experience gained with the LESSY battery system as part of a research and development project. Since mid-2014 a team has been working at STEAG to translate the lessons learned there into an economically viable concept. The core team is comprised of project manager Christian Karalis from the Trading & Optimization unit, Dr. Matthias Pracht from the Generation division, responsible for the technical management and coordination, and Dipl.-Ing. Michael Mühl from STEAG Energy Services, responsible for conceptual work and technical handling.

    Balanced within seconds 
    Resource-friendlier primary reserve power Until now, primary reserve power has been provided mostly by conventional power plants. For that they need to generate a certain minimum load for the period during which they are required to operate, and so they burn coal, oil, or gas. This is not the case with large-scale batteries. Hence valuable resources are conserved, CO2 emissions reduced and costs cut. 

    Learning from LESSY
    With the LESSY system installed at the Völklingen-Fenne power plant, from February 2014 through February 2016 STEAG gained valuable experience from the deployment of a large-scale battery (capacity one MW) for the provision of primary reserve power. The development of this lithium electricity storage system was sponsored by the German Federal Ministry of Education and Research. 

    Mastering complexity
    A large-scale project like this is a complex undertaking where there are many points to consider. For each site more than six expert opinions had to be furnished, for example on fire protection and nature conservation. “Owing to interdisciplinary collaboration within the STEAG Group and the cooperation with the local authorities, all requirements could be met in Lünen. The license for the site was issued in early March 2016 and work could begin on schedule,” says a very pleased Christian Karalis. Each large-scale battery system will consist of eleven containers. The containers with the technical systems are built by the industrial systems specialist Nidec in France, while the battery cells proper come from LG in South Korea. Colleagues Pracht and Mühl went to the Nidec plant in Roche-la-Molière in the Rhône-Alpe region to discuss the technical equipment of the containers and ensure the quality of their execution. In addition, Michael Mühl satisfied himself on site in South Korea that the high safety standards for the production of the battery cells and modules are met, and personally took part in tests for this purpose. The containers currently are being preconfigured with the technical systems by Nidec in France. They then only need to be fitted at the installation site with the battery modules and connected. The battery modules are brought to the various sites by ship and truck. During this process, certain temperatures need to be strictly maintained so that the batteries are not damaged.

    30 minutes minimum up time for highly reliable power supply
    Latest-generation high-efficiency lithium-ion batteries find use in the six systems. When partially charged, they are ideal for providing primary reserve power. Each system has a capacity of 15 MW, so that from the start of 2017 a total capacity of 90 MW will be available in the STEAG network. The 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 30 minutes. The background of this requirement of the German transmission system operators: major disruptions during which the supply frequency deviates significantly from the normal state for a lengthier period. Battery systems featuring storage capacities of, for example, only 15 minutes are drained or charged much more quickly. They consequently may not be able to provide primary reserve power for the entire duration of a major disruption and so ensure the stability of power supply. Major system failures could be the consequence. 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. “For reliable power supply, a minimum up time of 30 minutes is indispensable if, as society, we wish to continue to have a high standard of grid stability and security of supply, comparable to what we have now” Christian Karalis emphasizes.

    Economical and with great potential for the future 
    With its investment of some 100 million euros, STEAG becomes a pioneer in the use of large-scale battery systems. STEAG is convinced of the economy and viability of the technology and is investing this amount without availing itself of subsidies. To get a certain distribution in the grid, the large-scale batteries are being installed at six German power plant sites: Lünen, Herne and Duisburg-Walsum in North Rhine-Westphalia and Bexbach, Völklingen-Fenne and Weiher in the Saarland. The large-scale batteries make use of the infrastructure of the power plant sites, but operate independently. Conducing to their economical operation is, not least of all, their integration in the virtual power plant OneOpt, which integrates the distributed and central systems of STEAG (see www.steag-oneopt.com). One advantage: for the required backup STEAG does not have to build redundant systems at the sites. Should a battery fail, the needed primary reserve power can be provided from another source in the “virtual power plant” that is prequalified to provide primary reserve power. This substantially reduces the cost of the systems. 

    The system in Lünen will be put through trial operation from June to August 2016 before Trading & Optimization begins marketing. The experience will be applied to the building of the other systems so that all six large-scale battery systems will be in commercial operation by the beginning of 2017.