Mismatch between the solar and wind electricity production and consumption pattern

A fundamental issue with the wind and solar electricity is the dependence of the production on the weather, while the electricity consumption is dictated by human activity. The matching between electricity production and consumption must be kept at all time to ensure grid reliability. In case of oversupply of electricity, some renewable resources need to be disconnected from the grid.

Reversible high temperature electrolyser to support the integration of wind and solar electricity into the electrical grid

High temperature steam electrolysers use electricity to produce hydrogen that can be used as a fuel or stored for a later time. A reversible electrolyser is capable of converting this hydrogen back into electricity, meaning it can store electrical energy in the form of a chemical fuel that can be easily stored for short or long period of time. Since this technology is based on Reversible Solid Oxide Cells, it is referred to as ReSOC. The technology is not yet mature in terms of performance and cost for market entry. The partners of the BALANCE project are joining their effort to develop this technology to demonstrate its feasibility. Reversible electrolyser technology is expected to support the growth of wind and solar energy by providing grid balancing services.

The partners of the BALANCE project aim at:

Producing new generation of solid oxide cells with clear progress in terms of performance and durability with respect to state-of-the-art by optimisation and integration of alternative fuel electrode materials and nanostructured oxygen electrodes. The aim is to allow operation at lower temperature (700°C) with an area specific resistance of 0.2 ohm cm2 in electrolysis mode. Stability target are of < 0.5 % /1000 h at 700°C in Solid Oxide Electrolyser (SOE) mode with a current density of 1.25 A/cm2.

Optimising existing Solid Oxide Fuel Cell (SOFC) or SOE stack designs for reversible operation with the support of simulation tools. Stacks will be manufactured, tested and implementing in a demonstration system. In order to reduce cost, low cost ferritic stainless steels will be considered for interconnects and their durability will be assessed and potentially enhanced with protective coatings. The stack target is to have not less than 20% of loss of performance between cell and stack and a degradation rate of less than 2%/ 1,000 h in SOE mode.

Validating the ReSOC concept and performance target at system level with a system prototype. Its targets are 50 % efficiency in SOFC mode and 90 % in electrolysis mode at multi-kW scale. In addition, the reversibility and flexible operation will be demonstrated in a 2500 h test.

The suitability of ReSOC technology in different industrial environment will be investigated. System modelling, exergy analysis and techno-economic analysis will be used for different ReSOC plant configurations producing hydrogen or fuel via chemical conversion processes and providing grid stabilisation services. The system will encompass grid connection, ReSOC unit, possible hydrogen or syngas chemical conversion step and gas or fuel storage. The exergy analysis will provide the identification of the process step with major losses, optimise the process flow chart and provide specification for Balance-of-Plant components. Life cycle analysis will be conducted for deeper understanding of the process cost and environmental impact.