Cavernous energy sources

Cavernous energy sources

Efficient energy storage remains a major challenge as we look to the future. Under the ADELE project, RWE is working hard to achieve a technological, high-pressure breakthrough.

Wind doesn’t just blow when power is required – so what can be done with excess energy so that it can be used when it’s needed? In pump storage power stations, electrical energy is stored by pumping water upwards. When it then flows down, it produces electricity, and it is a solution that has been used and developed by RWE since 1906. Soon, however, there could be a revolution in this field under the name ADELE – “Adiabater Druckluftspeicher für die Elektrizitätsversorgung”, or “adiabatic compressed air store for electricity provision”. It may sound complex, but in principle it is a simple concept that will enable energy storage on a far larger scale than has previously been possible.

The first advantage of ADELE when it comes to energy storage is its location. The project can be found in the mountainous Staßfurt area (Saxony-Anhalt) of Germany, where salt is collected from huge layers. Pumping water into the ground loosens the salt, which then rises up as part of a solution. This results in sealed-off caverns below the ground in the salt anticline. The ADELE project plans to pump compressed air into these caverns – once electricity is required again, this air will then drive a generator to produce power.

ADELE makes all the difference

Compressing the air also generates heat automatically – as when pumping a bike tyre. Previous compressed air power stations have released this heat into the atmosphere, unused. Heat is necessary, however, when the compressed air is used in a turbine to generate power. Up until now, this was obtained by burning natural gas. As a result, the efficiency rating was low, CO2 was released into the atmosphere and energy costs were high.

With ADELE, things are different. The heat generated during air compression is actually stored and is then used later on to heat the air flowing through the turbine when producing power. This requires a heat store filled with ceramic material that functions like a thermos flask – albeit one capable of maintaining temperatures of around 620°C. As a result, 70% of the energy originally released, which otherwise would have gone unused, is recovered. RWE is working with General Electric, Züblin and the German Aerospace Centre on the ADELE project. The various parties involved in the project have stumped up 12 million euros for the development phrase, which will continue until 2013.

There is global demand for the efficient energy storage prototype, and in Germany there are several salt layers suitable for this solution. These are primarily found in the north and centre of the country, where the need is particularly high as a result of wind turbines.

ADELE is not RWE’s sole initiative in this field: as a founder member of the EASE (European Association for Storage of Energy), the firm is in constant discussion with twelve other energy companies regarding key issues in energy storage, its methods and their implementation – e.g. batteries in electric cars. Targeted research and development, as well as practical testing of storage technologies are thus hugely important to the association.

Image: Public Domain
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