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30 years in operation - and still ahead of its time? Compressed air energy storage power plant in Huntorf, Germany
© E.ON Kraftwerke GmbH, Wilhelmshaven
Intergration of regenerative power generators
Projektinfo 05/2007
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Compressed air energy storage power plants

In Germany, wind energy utilisation is growing dynamically. There is potential for further expansion on land, and offshore, and the technology for realisation is mature. Already 5 % of the electricity generated in Germany comes from wind energy. According to the plans of the European Union, renewable energy sources as a whole should reach 20 % Europe-wide by 2020.

This requires adjustments to electricity grids, the power plant mix, and energy management, as wind turbines do not produce in a demand-oriented manner, but in a weather-dependent manner. The short-term fluctuations in the electricity feed volume can indeed be predicted quite well, however inexactness remains in the forecasts. Added to this, wind turbines are mostly installed in weak grid areas in coastal regions, and far from large consumption centres.

Already today, it does happen that wind turbines in the North are prohibited from feeding electricity into the grid for some periods, due to grid overloading. According to the so-called dena grid study, the demand for balancing energy, i.e. energy to balance supply and demand, will increase to more than double by 2015. Simultaneously, 400 kilometres of power routes must be enhanced, and 850 kilometres must be newly built. Many experts doubt that this is possible in the short amount of time available. Alleviation could be provided by large energy storage systems, which allow the energy supply from wind parks to be planned and controlled similarly to the energy supply from conventional power plants.

The established pumped storage power plants, however, with their space requirements and their special site-related needs, are not suitable for broad implementation, especially as wind turbines' peak outputs are concentrated in the flat Northern regions.

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A more promising solution is buried deep underground: Northern Germany's widespread salt domes offer ideal conditions for the construction of the large caverns which are the central component of compressed air energy storage power plants. Worldwide, there are as yet only two of these so-called CAES (compressed air energy storage) power plants, which store excess energy as compressed air, and when required, convert it, together with natural gas, back into electricity. Research into whether and how wind energy can be better integrated into the German and European electricity supply by means of CAES power plants, is being conducted in various studies, sponsored by the German Federal Ministry for the Environment. The technological prerequisites, opportunities and costs are being examined in comparison to other solutions. Meanwhile, surprising possibilities for utilisation of natural gas deposits which were previously thought to be no longer usable have also become apparent.

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Project coordination
RWTH Aachen, IAEW