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Electrolysis cells allow for large-scale energy storage

By State of Green , 19 Feb 2018

The Technical University of Denmark has tested the ability of electrolysis cells to store power generated by wind turbines at a wind farm on the Danish island of Bornholm.

Electrolysis cells use electricity to split for example water molecules (H20) to hydrogen (H2) and oxygen (O2). This way, excess electicity from rewnewable energy sources such as wind turbines can be converted to bound energy in hydrogen molecules and be stored as a gas for later use.

Together with the company Haldor Topsøe, the Technical University of Denmark’s Department of Electrical Engineering and Aalborg University, the Technical University of Denmark’s Department of Energy Conversion and Storage tested modern electrolysis cell and stack design in a virtual reality simulated environment based on highly detailed wind data sourced from the wind farm on the Danish island of Bornholm in the research project, Towards Solid Oxide Electrolysis Plants in 2020.

The project was executed with support from the Danish Transmission Systems Operator, Energinet, in the so-called ForskEl program.

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– We always talk about the advantages of using electrolysis cells to convert excess energy from renewable energy sources such as wind turbines to gas, and now we did in an ultra-modern stack, says Senior Researcher Ming Chen from the Technical University of Denmark’s Department of Energy Conversion and Storage.

The Bornholm distribution system is a part of the Nordic energy grid, which is fully integrated in the energy market D2 and connected to Sweden’s main grid via cable. The Bornholm system consists of approximately 28,000 electricity customers and accommodates a long row of sustainable energy sources with low CO2 emissions, including wind power from four wind farms consisting of 38 wind turbines in total, which can produce approximately 30MW.

Just like the real world
The ForskEL project used data based on the wind profile from one of the four wind farms.

– We had access to all wind data from 2013 from the Bornholm wind farm, divided into five minute intervals. It gave us the possibility to create precise simulations with our cells and stacks based on realistic data, Ming Chen explains.  It was precisely as it is in the real world, notwithstanding the fact that we scaled the wind data down by a factor of 1000 to make it possible to test a simple stack instead of having to establish a full-size electrolysis facility.

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Two test scenarios
The ForskEL team created two different test scenarios based on wind data from December 2013, as December is a month with large wind fluctuations, which are very hard for the cells and the stacks. This gave the researchers the possibility to test a stack of 7.5 kW during harsh environmental conditions.

The first scenario simulated a constant flow of gas, while the second simulated variable conditions, where the flow of gas varied according to need. The stack, which consisted of 75 connected electrolysis cells was tested for a total of 2000 hours.

In both scenarios the stacks behaved identically and both were able to cope with the variations.

– We have now successfully demonstrated, that the newest cells and stack designs are robust and that they can cope with dynamic operations with fluctuating additions of steam and/or different power loads, says Haldor Topsøe’s Director of Research Peter Blennow and adds:

– We still need to test them under real, full-scale conditions, where other variables will have an influence, but we have demonstrated that the technology works and is robust.

Ming Chen agrees.

–  The cells and the stack functioned impeccably during hard operating conditions in both scenarios. This means that the cells and the stacks can be installed and used for large-scale energy storage without problems, Ming Chen says.

The researchers from the Technical University of Denmark’s Department of Energy Conversion and Storage will now work on further improving the electrolysis cells.

About the project
The ForskEL project “Towards Solid Oxide Electrolysis Plants in 2020” was financed by Energinet.dk and consisted of close cooperation between four experts who work with different aspects of energy and energy systems.

The Technical University of Denmark’s Department of Energy Conversion and Storage developed and optimised the electrolysis cells, while Haldor Topsøe A/S built the cells together in the electrolysis stack with optimal service and lifespan.

The Technical University of Denmark’s Department of Electrical Engineering was responsible for the simulations of how the electrolysis stack would impact the existing electricity grid and created a power supply unit with new design and improved efficiency.

Aalborg University developed a strategy which describes how the electrolysis technology can be implemented in the future Danish energy system.

Source: Energy Supply Denmark, the Technical University of Denmark

 

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