Deutsche Version  ACT
Thermal Storage
Large scale emission-free electricity storage 18.10.2016

Im ADELE-Projekt untersuchen Wissenschaftler seit Ende 2009 die Machbarkeit der „Adiabaten Druckluftspeicher-Technologie“ mit Fokus auf die Kernkomponenten Turbomaschinen, Wärmespeicher und Kaverne.

Compressed air instead of a pumped-storage power plant

Since 2009, scientists in the joint ADELE project are investigating adiabatic compressed air storage systems with a focus on turbo machines, thermal storage systems and caverns. In the ADELE-ING follow-up project, researchers are now comparing the various process versions. This is intended to drive forward the basic and detail engineering required for a preliminary demonstration plant and act as an investment basis.

Project status Final phase
Typical system size Energy 1040 MWh
Typical system size Output 260 MW
Efficiency AC/AC Approx. 70%
Storage loss [1/d] <3%/d
Cycle durability (80% discharge level) 100%
Typical discharge time 40 a
Response time when preparing the energy 4 h
Example application areas < 15 min
Temperature change Balance of daily fluctuations, daily charge and discharge, wholesale market, ancillary services, capacity markets
Storage medium Sensitive storage system
Storage construction Natural stone and ceramics
Project duration Pre-stressed concrete containment

Nearly the entire capacity of grid scale electrical energy storage in the world is realized by installation of pumped hydro power plants. However, its deployment potential will be limited in some areas due to different reasons such as topography of the landscape or lack of opportunities for grid connection.

Adiabatic CAES can serve as an alternative: A-CAES is believed to provide a high deployment potential for electrical energy storage in a multiple hundreds of MW/MWh up to GW/GWh scale per site at costs in the same order of magnitude as those of conventional pumped hydro plants. The previous ADELE-R&D-project co-funded by the federal German government had an emphasis on the development of the required, but until now commercially not available core components as well as on the basic process layout.

  • Electricity generation from renewable energy sources is volatile; storage may help integrating these generation into the electricity supply system. &copy; RWE Power AG
  • The axial compressor of a gas turbine serves as first compression stage. &copy; General Electric
  • One or two radial compressor casings will compress the air to its final pressure level. &copy; General Electric
  • low pressure regenerator type thermal energy storage (TES) &copy; Ed. Züblin AG
  • High pressure TES based on a concrete block. Pressurized air is passing the TES through a bundle of pipies – picture of prototyp in Carboneras, Spain &copy; Ed. Züblin AG
  • Potential for cost reduction: comparison of the cross section of the pressure vessel of a regenerator TES for a high pressure (left) and a low pressure (right) application. Both solutions provide identical useful inner diameter to store inventory material. &copy; Ed. Züblin AG
  • Pressure vessel large scale testing at Züblin: testing of technical feasibility by the means of a pre-stressed TES-section (cylinder disc) in actual size dimensions &copy; Ed. Züblin AG
  • Pressure vessel large scale testing at Züblin: testing of technical feasibility by the means of a pre-stressed TES-section (cylinder disc) in actual size dimensions &copy; Ed. Züblin AG
  • The HotReg- test rig at the DLR allows thermal cycling of up to 5 tons of storage inventory material under real conditions. &copy; DLR
  • DLR scientists preparing a new test campaign at the HotReg test rig &copy; DLR
  • Considering the local geomechanical boundary conditions, ESK staff (ESKGmbH - RWE Group) is planning the solution mining and operation of the subsurface caverns. &copy; ESK GmbH (RWE Group)
  • Expected cavern shape after solution mining as a result of 3D-modelling tools. &copy; ESK GmbH (RWE Group)
  • Caverns as storage is proven technology in natural gas and petroleum industry with several decades of operational experience. &copy; ESK GmbH (RWE Group)
  • Cutaway view of the Staßfurt salt saddle: example for cavern geology &copy; ESK GmbH (RWE Group)

Holistic approach

In order to get there, ADELE-ING is structured in a holistic and milestone oriented way:
The initial one year „concept phase“ shall identify and confirm the preferred ADELE-process layout. A multi criterion investigation (amongst others environmental, technical and economical performance) allows a comparison between a number of plant configurations and will provide the basis for the selection process.
Provided that economical perspective for this technology can be proven until the end of the year 2013, the selection process will be followed by the basic and detail engineering phase which covers the engineering for all core components as well as all auxiliary plant components (piping, valves, heat exchangers, peripheral balance-of-plant components) and as well as authority engineering to achieve all required permits for the demonstrator.   
In parallel the possible future role and significance of the ADELE-Technology for the German electricity supply system will be investigated from the perspective of a transmission system operator (TSO), independent research institutes, a power plant operator as well as a distribution system operator (DSO).

Further development of components and the entire plant

Compared to the so called “diabatic” or “conventional” compressed air energy storages, the “adiabatic” CAES process makes use of the heat generated during compression of the gaseous storage media „air“. Since the heat is captured and stored for later use during discharge, the adiabatic process can avoid heat losses during charge and co-firing of fossil fuel like natural gas (and green house gas emissions respectively) during discharge and thus raise the roundtrip efficiency up to 70 %. However, the concept requires new components which are not commercially available. Firstly high-temperature / high pressure turbines and expanders have to be developed, secondly large amounts of heat have to be handled at high temperature levels during charge and discharge mode. Furthermore the design of the entire plant layout including the interaction of all auxiliary and balance of plant components, the elaboration of operational strategies (design / off-design), dynamic load change behavior and last not least the drafting and execution of relevant permit procedures for this new technology will be scope of the ADELE-ING project.

Wirtschaftlichkeit und Dauerhaftigkeit

Großspeichertechnologien stellen eine Dienstleistung für das Stromversorgungssystem bereit. Sie müssen sich wirtschaftlich dadurch tragen, dass die Bereitstellung von Elektrizität bei der Entladung des Speichers mehr Einnahmen generiert, als Kosten für Strom zur Befüllung des Speichers anfallen. Darüber hinaus müssen durch den Betrieb die Kapitalkosten für die Investition sowie weitere variable Kosten erwirtschaftet werden. An den klassischen Märkten, wie Wholesale-Markt und Regelenergiemärkte, ist es jedoch entgegen vieler Prognosen gerade durch den Ausbau der Erneuerbaren Energien sowohl zu einem Preisverfall gekommen, als auch zu einem Sinken der sog. Spreizung zwischen hohen Strompreisen bei hoher Nachfrage (Peak) und niedrigen Strompreisen bei niedriger Nachfrage (Off-Peak). Gerade diese Peak-Off-Peak-Spreizung ist es jedoch, mit der Speicher ihre notwendigen Einnahmen generieren.

Market of the future

Besides technical development risks, the challenge is to develop today a technology to match highly uncertain future market requirements in order to be competitive amongst a number of different storage alternatives. Future boundary conditions set by the regulator are highly uncertain by nature and hardly to predict. Will there be enough incentive for high plant efficiency or will low investment costs at lower plant performance be the predominant driver for economical success? Due to the mentioned uncertainties the goal will be to develop a technical flexible as well as economical robust plant concept at the same time in order to be able to best adapt the technology to future needs.

Supported by: The Federal Government on the basis of a decision by the German Bundestag


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Research funding

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