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Design Study for the European Underground Research Infra-structure related to Advanced Adiabatic Compressed Air Energy Storage

Periodic Reporting for period 2 - RICAS2020 (Design Study for the European Underground Research Infra-structure related to Advanced Adiabatic Compressed Air Energy Storage)

Reporting period: 2016-12-01 to 2018-05-31

As a consequence from increasing energy production by renewables, the demand for technologies for storing adequate, sustainable and cost-efficient forms of energy is consequently increasing. Compressed Air Energy Storage (CAES), where compressed air is stored in underground caverns, is a well-known option of energy storage and the only currently feasible large-scale energy storage technology apart from pumped hydrostorage. The currently only existing CAES plants are diabatic ones, where fuel is added in the discharging phase. The Adiabatic CAES, where no fuel is added in the process has been studied as pure green storage alternative and is designed to deliver higher efficiencies via a zero-carbon process to an efficiency of about 70%. Nevertheless, research on this method contends with difficulties like the geological restriction to salt domes.
RICAS2020 will meet this challenge by providing an innovative design concept independently from the encountered geological conditions. Energy will be directly stored at all places where high energy demands exist. RICAS2020 shall be located as an extension of the independent research infrastructure “research@ZaB” in Eisenerz, Austria.
The main conceptual design requirements of the RICAS2020 research infrastructure were specified in Work Package WP2 Design Requirements and Feasibility Study. Design alternatives were proofed in relation to the associated costs and the current and future strategic relevance & feasibility. The concepts are oriented to a realization of the research infrastructure as a 5 MW prototype.
In WP3 Concept and Engineering Plans for Thermal Energy Storage a quasi-one-dimensional heat transfer model to predict the thermodynamics of TES systems was developed and validated by ETH. Three groups of high-temperature materials (rocks, concrete, and ceramics) were considered and based on a thermodynamic and environmental analysis, the ideal storage material are rocks from the excavation site.
In WP4 numerical simulations were performed with a focus on the development of a new breakthrough realistic simulation approach. This approach allows overcoming limitations of the existing tunnel excavation simulation procedure in ABAQUS, namely, stress-free installation of the support elements with an intact thickness.
The aim of WP5 Concept for Innovative (Cavern) Excavation Methods was to develop an innovative tunnelling technology to be used in the construction of the large air storage caverns that will be needed for an Advanced Adiabatic Compressed Air Energy Storage power plant (AA-CAES). Initial studies on the efficiency of laser ablation under various external conditions showed that the specific energies required make the removal of rock material via melting and vaporisation bye laser irradiation unfeasible and uneconomical. From observations of these initial studies concepts combining laser ablation and mechanical cutting were developed.
WP6 Concept for New and Advanced Materials contains an evaluation of the initial location requirement as well as the possible lining material and structural solution. For the RICAS2020 project, the most promising design for the storage is represented by a segmented liner solution with internal polymeric based sprayable membrane.
In WP7 Safety and Security Assessment Concept information on relevant CAES projects, as well as other underground gas storage installations, namely CO2 and natural gas storage was worked out. Furthermore the corresponding norms and regulations for CAES, CO2, and natural gas storage are described. The safety aspects of underground gas storage are also investigated through two case studies. They provide information on the long term aspects of an underground gas storage facility.The safety aspects of the test facility were analyzed, according to the standard ISO 31 000.
In WP8 an environmental analysis of RICAS2020 concept has been performed to determine the hotspots for the whole life cycle, from the resources obtaining, the construction until the operation. To do the analysis, the life cycle inventory data related to each compartment of RICAS concept (excavation process, TES infrastructure, cavern construction, machinery and operation) has been created.Furthermore a detailed social analysis of RICAS2020 has been done.
WP9 ensured that the dissemination and exploitation activities were successfully performed. A RICAS2020 project website ( was launched at the beginning of the project. Dissemination activities like presentations, publications and press articles have been carried out. Furthermore discussions with funding bodies and the Austrian ministry took place to foster the realization of the RICAS2020 research infrastructure as follow-up of this design study. Further important activities of dissemination were the creation of a project video and a project flyer, as well as the organisation of RICAS conferences and workshops.
Currently the most mature energy storage technology is Pumped Hydro Energy Storage (PHES). However, this technology has its own disadvantages such as geographical limitations and the need of a great space requirement on the surface. A good alternative is a Compressed Air Energy Storage (CAES). Newertheless, AA-CAES has crucial restrictions such as dependence on geology (salt or porous rocks), geographical limitations (underwater air bags) or need large areas on surface to install the cisterns and tanks. RICAS2020 will help to overcome these factors which impose limits on the applicability of the AA-CAES technology. One of the main outcomes of the research in the underground infrastructure will be an opportunity to store compressed air in an underground storage cavern in any geological formation, which means in future AA-CAES facilities could be implemented wherever required, for instance very close to big cities or other high capacity energy consumers.
The results of the project include new concepts for rock cutting technologies that have not yet been implemented. A successful implementation of the concepts will yield a compact tunnelling machine that is capable of drilling hard rock with little tool consumption and thus low standing times, while also being able to create flexible tunnel geometries with comparatively little noise pollution. This technology is thus potentially important for tunnel construction in urban environments, where drill-and-blast creates too much noise and vibrations, and where full-scale tunnel drilling machines are not flexible enough. Furthermore a suitable basis is developed for further and more detailed investigations in the area of implementation of safety and security issues, safety assessment and measures and the obligatory approval procedure.
Finally, the results have shown a better environmentally friendly profile for RICAS2020 concept, in front of PHES. In regards to social influence it has been determined that it is very important to consider a communication strategy to the society in order to ensure the well-acceptance of the technology. On the other hand, RICAS2020 concept has been proved to be a technology with no impact on landscape (no noise, no vibrations and no emissions). It has been determined also that the implementation of RICAS2020 concept can generate job opportunities to local communities and increase the access to energy sources to the society and the promotion of renewable energy sources (RES).