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Flexible Storage for Strong Winds

Water electrolysis for the large-scale storage of wind power in the form of hydrogen

The goal of the German federal government is for renewable energies to have a substantial share in the future energy mix. However, the energy supply of the future should also be reliable and affordable in addition to being environmentally friendly.

Compared to 1990, greenhouse gas emissions are to be reduced by 80–95% and the share of renewables increased to 60 % of the gross end energy consumption and 80% of gross electricity consumption.
The intensive expansion of renewables energies poses great challenges. Wind power and solar energy are subject to high and rapid fluctuations – these variations, which are due to their location and the weather, must be compensated for in order to guarantee a continuous supply of sufficient power. This must be taken into account during conversion, storage and transport. The power transmission and distribution grids must be expanded and large amounts of energy must be stored. Finally, energy consumption by the consumers must become more flexible, for example with new power supply concepts or smart appliances that adapt their electricity consumption automatically according to grid load.

Hydrogen storage is very important in connection with renewable energies. Large quantities of hydrogen produced by means of electrolysis using renewable electricity serve as chemical storage and can be used in different ways: it is most effectively utilized to power fuel cell vehicles. In addition, reconverting it in gas turbines and fuel cells is also a viable option. Using CO2 from power plants and biogas facilities, methane can be produced in an intermediate step (methanation) and fed into the existing natural gas grid.

Current large-scale electrolysis facilities are based on alkaline electrolysers operated largely without cycling or partial load. As a consequence, surplus electricity, for example during periods of strong wind, cannot be utilized and is therefore wasted.

Other methods of electrolysis may provide a solution to this problem. Jülich scientists and engineers at the Institute of Energy and Climate Research (IEK) are developing techniques that involve a ceramic electrolyte and a polymer electrolyte membrane (PEM), i.e. that use different materials and components. Experts from Electrochemical Process Engineering (IEK-3) focus on developing new materials for functional layers to increase performance and minimize conversion losses and material costs. Not only can PEM electrolysis absorb extreme overloads, it also increases efficiency and simplifies plant set-up.

Important challenges must still be overcome before these promising technologies can be widely introduced. For example, the power density and lifetime of PEM systems must be increased and production costs reduced until the method is profitable. In addition, adjustments will have to be made for the grid requirements associated with large-scale operation: facilities will have to be scaled until they reach the megawatt range while at the same time being able to operate at partial load spontaneously.

In order to demonstrate practical applicability, the impact of the new methods on the energy economy and environmental technology are analysed using computer-assisted models.