NRP's Joint Synthesis on 'Electricity Storage via Adiabatic Air Compression' now online
Please find the National Research Programmes (NRP) joint synthesis on 'Electricity Storage via Adiabatic Air Compression' here: in English, in German and in French.
Summary: The phasing out of nuclear power plants and the expansion of solar and wind energy mean that electricity production is becoming more volatile. New storage systems are needed to ensure that electricity is available as and when it is required.
A promising technology for this purpose is adiabatic compressed air storage. It uses excess electricity from solar and wind energy systems to compress ambient air and store it in an underground cavity. When it is required, the compressed air is expanded again, driving a turbine and generating electricity once more. As the heat which was generated during compression is used for this process, the efficiency level stands at 65% to 75%, which is similar to that achieved by pumped-storage systems. The environmental compatibility of compressed air energy storage (CAES), in terms of the potential for emitting greenhouse gases and the damage inflicted on ecosystems, is also comparable to that of pumped-storage systems.
CAES systems are technically feasible. Important components such as turbomachinery and heat accumulators are either already available on the market or have been tested in a pilot plant. The process for constructing cavities is also well-developed due to the experience gained in tunnel and cavern construction.
Adiabatic CAES therefore represents an efficient, environmentally friendly and technically feasible storage solution. Due to the high capital costs and the unclear economic and legal framework conditions, however, it is uncertain whether they can be economically viable. This also complicates the financing of a demonstration plant.
White Paper Power-to-X Completed!
On July 8, 2019 the White Paper Power to X was officially introduced to the public.In a joint research project of five Swiss competence centers for energy research, scientists of the Paul Scherrer Institute (PSI), the Swiss Federal Laboratories for Materials Science and Technology (Empa), ETH Zurich, the Zurich University for Applied Sciences (ZHAW), the University of Applied Sciences Rapperswil (HSR), the University of Geneva, and the University of Lucerne have prepared a white paper on "Power-to-X" for consideration by the Swiss Federal Energy Research Commission. The goal of the white paper is to gather together the most important insights available on Power-to-X technologies. Among other things, the study sheds light on contributions that could be made to Switzerland's energy strategy by different technologies based on conversion and storage of various forms of energy. The experts presented the findings of this study on July 8, 2019 at ETH Zürich.
The white paper is currently in revision. Please contact us for further information.
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The Swiss Competence Center for Heat and Electricity Storage
HYDROGEN PRODUCTION VIA REDOX FLOW BATTERY |
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ADVANCED ADIABATIC COMPRESSED AIR STORAGE |
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DEMONSTRATORS |
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SODIUM ION BATTERY |
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CO- ELECTROLYSIS |
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ASSESSMENT OF ENERGY STORAGE IN SWITZERLAND |
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A ranking for storage options, depending on cycle time is given. At a system size of 1 MW, for short (< 1 min) term storage battery systems are most economic and associates with the least greenhouse gas emissions, while for medium term storage (day), battery is still advantageous in terms of cost, but not in terms of green-house gas emissions, Batteries fall behind pumped hydro and adiabatic air storage.
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REDOX FLOW BATTERY (RFB)
Like in fuel cells, the redox flow cell is supplied with fuel (electrolyte) form external. Like an accumulator the process is fully reversible in one device. Since the electrolytes are in liquid phase, storing them is straight forward (plastic containers can do the job). However, the down side of RFB is a low energy density and the relatively low energy efficiency of (80-85%) compared to other batteries. This limits the use of RFB to niche applications so far, but makes them interesting for research. During phase I of the SCCER Hae, an idea was formulated: If the redox couple were Cerium III/IV combined with Vanadium II/III as electrolytes, a parallel catalytic reaction can produce hydrogen and oxygen, thus the cell can do electrolysis once the electrolyte is fully charged. This is interesting for processes which require a continuous stream of hydrogen, like biogas upgrading at waste water treatment plants. More details are available in the SCCER HaE Annual Activity Report 2016, p. 37-38 .ADVANCED ADIABATIC COMPRESSED AIR ENERGY STORAGE (AA-CAES)
The growing share of fluctuating renewable energy sources like wind and solar requires short- and long-term energy storage to guarantee the power supply. Pumped hydro storage is at present the main option for large-scale storage. Electricity Storage systems based on pumped hydro are available since little more than 100 years and the massive capacity build up started in the 1970’s. Therefore the best locations for such installations are already explored. One promising alternative to pumped hydro storage is advanced adiabatic compressed air energy storage (AA-CAES) with an estimated round-trip efficiency of more than 70%. In Phase I, a demonstration plant was commissioned. The close collaboration of three research groups and the industrial partner enabled the fast progress, supported by project funding from the CTI SCCER- and the NRP 70 programme. More details are available in the SCCER HaE Annual Activity Report 2016, p. 5-9.DEMONSTRATORS
Many concepts for energy storage exist on paper, on material level and lab scale devices. The assessment of the concepts in terms of their suitability for everyday use can be done only on demonstrators of power and capacities of about 1/100 to 1/10 below the real application. Two of such demonstrators are described in separate highlights (AA-CAES and RFB with Hydrogen production and the hydrogen filling station). Within the SCCER, three more demonstrator projects can be reported. Already at the beginning of Phase I the 25 KW power to gas plant at the HSR in Rapperswil was put into operation and two years of experience with this plant was gathered. The energy system integration platform (ESI), an installation with increased complexity was commissioned in phase I of the SCCER. Here, the interplay of different conversion type storage systems is explored on a 100kW scale. More details are available in the SCCER HaE Annual Activity Report 2016, p. 63-66.