KompEx LTA-CAES^® modular: Compressed air energy storage for site-independent use

A new type of technology aims to make the use of compressed air energy storage systems cheaper, more flexible and more sustainable in the future. Within the framework of the joint research project “KompEx LTA-CAES^® modular“ Fraunhofer UMSICHT and BOGE KOMPRESSOREN are developing a system technology for this purpose. A modular design and the combination of turbo- and piston machinery enable a site-independent use of the compressed air energy storage. The special feature of this low-temperature compressed air energy storage system is the use of the same machinery train for charging and discharging. In comparison to conventional compressed air energy storage systems with separated machinery units, a complete machinery train can be dispensed.

Fraunhofer UMSICHT develops the reversibly operable turbomachinery required for this purpose and is responsible for the overall design, economic evaluation and optimization of the entire plant. BOGE, the Bielefeld-located system manufacturer for compressed air solutions, develops and tests the reversibly operable piston machineries in parallel. The project creates the basis for the sustainable storage of electricity from renewable energy sources.

The transition from fossil fuels to regenerative energy sources requires new concepts for electricity storage systems in order to compensate fluctuating wind and solar power feed-in and to shift larger amounts of energy over days and/or weeks.

Pumped hydro energy storages are able to fulfil these tasks, but the usually large plants interfere considerably with the landscape and require a difference in height for their work. Compressed air energy storage systems, on the other hand, can also be used in flat areas. In windy northern Germany, for example, compressed air energy storage facilities using underground storage volumes – so-called salt caverns – with low land consumption and marginal environmental impact can be used to shift large amounts of energy.

Compressed air energy storage systems store electric energy in form of compressed air and use it to generate electricity when required. During charging, a compressor transports air from the atmosphere into the storage tank. During discharging, the compressed air is used to drive a generator-connected turbine and to generate electric energy again. Since air heats up strongly during compression and cools down drastically during expansion, the new technology is designed to store the occurring process heat and reuse it during expansion. Compared to conventional compressed air energy storage systems, the plant concept under investigation does not rely on the co-firing of fossil fuels. This increases efficiency and avoids emissions.

The plant layout developed in this project will be able to use alternative storage volumes such as steel pipe storages in addition to salt caverns by coupling turbo- and piston machinery. In contrast to conventional compressed air energy storage systems, the system thus can be used regardless of location. Due to the modular design of the system, it is also possible to build much smaller systems than before, which opens up new fields of application. For example, in order to store electricity in behind-the-meter applications in industry or to internationally support diesel power displacement in combination with renewable energies in off-grid systems.

• BOGE KOMPRESSOREN Otto Boge GmbH & Co. KG