ADELE to store electricity efficiently, safely and in large quantities

Storing electricity efficiently, safely and in large quantities – this is certainly one of the key challenges of future power supply. RWE, General Electric (“GE”), Züblin, and Germany’s National Research Center for Aeronautics and Space (“DLR”) rise to this challenge by realizing their ADELE project. On 19 January 2010, the project members signed the corresponding development cooperation agreement in Berlin, Germany.

Based on the ADELE concept (ADELE standing for the German acronym for adiabatic compressed air energy storage for electricity supply), air will be compressed during periods when electricity supply exceeds the demand; the resulting heat will be buffered in a thermal energy storage, and air will be pressed into underground caverns. When electricity demand increases later on, this compressed air can then be used to generate power in a turbine by simultaneously recovering the heat.

“The massive and deliberate expansion of wind power requires smart solutions to ensure a non-stop continuous electricity supply. By means of the ADELE project, we take the lead to rapidly develop an efficient storage option”, said Dr. Jürgen Großmann, Chief Executive Officer of RWE AG. A well-balanced energy mix where all energy sources contribute their unique strengths will be a guarantor – also in the future – of environmentally friendly, safe and efficient electricity supply. In this context, innovations such as ADELE will help to optimize the coexistence and smooth interaction of the individual energy sources.

By means of a feasibility study, the project partners laid the foundations for this development program that starts now. The aim is to install an initial demonstration plant, which shall start its operation in 2013; it will have a storage capacity of one billion watt-hours (GWh) and generate electrical power of up to 200 megawatt. That way ADELE will be able to provide backup capacity within a very short time and replace forty state-of-the-art wind turbines for a period of five hours. The German Federal Ministry of Economics is willing to offer state funding, which underlines the special importance of this project. Altogether, the project members will contribute an amount of EUR 10 million.

“We will support this project through innovative compressors and air turbines. This equipment ensures that compressed air energy storage power stations are extremely reliable and can be operated with outstanding performance. Last but not least, the leading edge technology of these key components is the result of our continuous investments in research & development activities both at our technology locations in Germany and worldwide. In this connection, our European research center based in Garch-ing nearby Munich holds a key position”, stated Georg Knoth, GE’s CEO & Regional Executive for the German-speaking region.

During the compression process, the temperature of the air will play a decisive role since it rises to more than 600 °C – thus making high demands on the compressor technology. To ensure that the resulting heat will not be lost, it will be extracted from the compressed air, before the air is stored, and absorbed by thermal energy storage. As soon as power is to be generated and before the air will be able to drive a turbine, the cold, compressed air must be heated again by the thermal energy storage. This adiabatic approach whereby the heat of the compressed air is not lost but remains in the process and can be used for power generation differs from existing compressed-air reservoirs primarily by its significantly higher levels of efficiency. Furthermore, the compressed air will not be heated any longer by means of natural gas – thus avoiding CO2 emissions.

To implement this project, not only advanced turbo machines but also an innovative high-temperature thermal energy storage concept has been required. The realization of this key component is supported by Züblin as well as by DLR by dividing the corresponding workload.

“The development of a powerful heat accumulator featuring a very high internal pressure and an operating temperature of more than 600 degree Celsius confronts us with completely new challenges with respect to the design of the pressure chamber and the development of suitable storage materials. Such a task can only be solved by a break-through innovation because the thermal energy storage will be subject to stresses resulting from the cyclic temperature and pressure loads, which are much higher than usual”, explained Jörn Beckmann, Chief Executive Officer of Züblin.

Prof. Dr. Johann-Dietrich Wörner, Chairman of the Board of DLR, added: “Within the framework of the ADELE project, we will develop solutions for the conception, design, layout, and dimensioning of storage equipment and high-temperature insulation, which are core components and of decisive importance for the performance and cost efficiency of the overall structure.”

Suitable locations for compressed-air storage power plants are, in particular, regions with adequate geological salt structures, which can then be used to build underground caverns for the absorption of large quantities of compressed air. In addition, such salt structures should be close to wind turbines.

Concerning the selection of the location, Erdgasspeicher Kalle GmbH, a subsidiary of the RWE group, will contribute its know-how for the planning, installation, and operation of underground storage facilities.

GE (NYSE: GE) is an innovative and diversified technology company taking on the world’s toughest challenges. From aircraft engines and power generation to financial services, healthcare, and television programming, GE operates in more than 100 countries and employs about 300,000 people worldwide. In Germany, GE operates more than 40 locations and has a staff of about 7,000 employees. Key areas of its ac-tivities are green technologies, medical technology, research, and financial services. In 2004, GE established its European research center GE Global Research Europe close to Munich. Moreover, GE is among Germany’s most attractive employers. The company has been given the “2009 Award as Top Employer for Engineers” and has – according to the Jury of the German Sustainability Award 2009 – with its ecomagination initiative one of the three most sustainable future strategies in Germany.

Ed. Züblin AG, Stuttgart, is one of the leading German building contractors with a staff of about 14,000 employees and annual construction work amounting to EUR 3 billion. Since the formation of the company in 1898, Züblin continuously grew and now is the no. 1 company for building and engineering services in Germany. Its portfolio of services comprises all relevant construction tasks. Since 2005, the majority of Züblin is held by the Austrian STRABAG SE, one of the largest European building and construction groups.

The most important current Züblin projects in Germany include the Opera Tower and the Air Rail Center in Frankfurt, the ADAC headquarters in Munich, the Rhine Gallery in Ludwigshafen as well as the West German Proton Therapy Center in Essen and the Virus Research Facility of the Friedrich Löffler Institute on the Riems island. Following the development of a heat accumulator for solar power plants, ADELE is already the second project in the area of energy storage, which will be jointly supported by Züblin and DLR. The Züblin business divisions Central Technology and Ooms-Ittner-Hof are significantly involved in the ADELE project.

Deutsches Zentrum für Luft- und Raumfahrt (“DLR”): DLR is the national research center for aeronautics and space of the Federal Republic of Germany. Its extensive research and development work in aeronautics, space, transportation, and energy is integrated into national and international cooperative ventures. Over and beyond its own research projects, DLR serves as Germany’s Space Agency. The German federal government has given DLR responsibility for the forward planning and implementa-tion of the German space program as well as international representation of Germany’s interests. DLR has thirteen locations and employs a staff of approximately 6,500 people.