© DLR
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.
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.
