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Reversible Solid Oxide Electrolyser (rSOC) for resilient energy systems


This project will focus on enabling more widespread integration of renewables through the use of r-SOC technology. Two business cases can be particularly addressed:

  • first, the renewable energies storage in off-grid remote areas, or in non- or low-interconnected islands, where there can already be an early market driven by emerging renewables curtailment and very high fossil generation costs [1];
  • second, eco-building or eco-districts, where renewable energies like PV are installed where energy storage is required to achieve consistently high penetration rates of PV production and increase profitability of PV investment while minimizing the amount of power purchased from the grid: this market has a short term, economically viable use. For residential houses, storage can allow increasing the consumption of local electricity generation from the 20-40% “natural” self-consumption to values above 50% [2], and either hydrogen or solid state battery storage or a combination of both is the most suitable option [3]. For commercial buildings where consumption profiles can be very different over a week (e.g. week-end with less or no consumption and potentially high production), the need of storage is even more evident in order not to curtail the PV production, and hydrogen-based P2P system can avoid the installation of MW-size battery systems. In addition, H2 produced can be used as fuel for vehicles if needs exist, and in case of H2 shortage, rSOC operating in fuel cell mode can be fueled with natural gas, thus offering flexibility and convergence of multiple usages.

For both cases, the rSOC technology, which allows a higher power-to-power efficiency and a maximized utilization rate, is beneficial for OPEX and CAPEX respectively. The development of these market segments will allow creating technological learning so that the larger energy storage market could be also assessed in the near future with such systems. In the project, one of those business cases, or any other documented business case will be targeted.

The following specific issues should be addressed:

  • Component development and system design for dynamic and reversible operation (e.g. high efficiency both in fuel cell and electrolysis mode, gas tightness, high durability in long term operation);
  • System operation strategies to manage switches from SOFC to SOEC operation mode: these should be aligned with ongoing normative and standardisation activities;
  • Reversible operation with both H2 and CH4 (SOFC) and steam (SOEC);
  • Optimise fuel utilisation and steam conversion rates to 80-85 % in both SOFC and SOEC mode on system level;
  • Develop a smart concept for electrical connection to decrease cost for power electronics;
  • Power modulation 50 - 100 % in fuel cell mode, H2 production rate modulation 70 – 100 % in electrolysis mode;
  • Minimise thermal losses and optimise thermal integration for maximum efficiency;
  • Demonstrate at system level a power of 50 kW (electrical) in electrolysis mode, and up to 20 kW (electrical) in fuel cell mode;
  • Concept design study for system scale-up towards 1 MWel (SOFC);
  • Prediction of production cost, electricity cost and hydrogen cost for up-scaled system based on real application and volume scenarios;
  • Develop a business model and a techno-economic analysis, including comparison of the overall efficiency, reliability and cost-competitiveness with other state-of-the-art power-to-power technologies, demonstrating distinct advantages of hydrogen based systems.

The consortium should include at least one SOEC stack/module manufacturer, research institutions and academic groups.

Liaison with representative bodies developing standards and procedures for rSOC operation is recommended.

It is expected that the technology starts at TRL 3 and reaches TRL 5 at the end of the project

Any safety-related event that may occur during execution of the project shall be reported to the European Commission's Joint Research Centre (JRC), which manages the European hydrogen safety reference database, HIAD (dedicated mailbox

The FCH 2 JU considers that proposals requesting a contribution from the EU of EUR 3 million would allow this specific challenge to be addressed appropriately. Nonetheless, this does not preclude submission and selection of proposals requesting other amounts.

Expected duration: 3 years

[1] FCH-JU, “Commercialisation of energy storage in Europe”, 2015


[3] Rasmus Luthander, « Photovoltaic self-consumption in buildings: A review”, Applied Energy 142(2015) 80–94

For hydrogen energy technologies to be able to compete in the energy storage market, the power-to-power round trip efficiency must be improved reducing at the same time costs.. Using two separate devices, namely an electrolyser and a fuel cell means both will be used part time, which increases the investment cost. Solid Oxide Cells (SOC) are intrinsically reversible and thus can be operated either in electrolysis mode to produce hydrogen from steam, or in fuel cell mode to produce electricity, depending on the needs. Thus, only one device is required, which is operated almost full time with fewer start/stops. In addition, Solid Oxide Fuel Cells (SOFC) and Solid Oxide Electrolysers (SOE) can achieve higher efficiencies while in SOFC mode electricity can be produced from H2 and/or CH4 using the same device, offering an additional flexibility.

The ability of reversible solid oxide cell (rSOC) devices to perform real dynamic cycling between power storage and power generation modes (SOE to SOFC and back) while keeping an acceptable degradation is still to be demonstrated though. Improvements to cell materials and construction are required as well as enhancements to system level issues of steam supply management, gas composition change during inversion from one mode to the other, thermal management, etc. The extensive cycling requirements to create a commercial rSOC system that can be coupled to renewable energy production systems such as wind and solar power has not been addressed to date.

The project should show a functional rSOC system operating in both modes allowing a proper validation of the performance characteristics (efficiency, modulation, operation dynamics) for future application scenarios. The following KPIs are expected to be reached at system level:

  • 200 full cycles from SOFC to SOEC and back during operation with minimum degradation (<2%/1,000 h);
  • Overall electrical energy efficiency target in electrolysis mode on steam ³75% (HHV), which is aligned with MAWP KPI (value for 2023);
  • Overall electrical energy efficiency target in fuel cell mode on methane ³ 55% (LHV), which is aligned with MAWP KPI (value for 2020 and 2023);
  • System operation time of >7,000 h;
  • Fuel utilisation and steam conversion rate of >80 % on large stack module level;
  • rSOC system CAPEX < 3.6 M€/(t/d) (electrical input in electrolysis mode), in a series production of 1,000 units/year. While no CAPEX target is set for high temperature electrolysis in the MAWP, the above values, by comparison to the KPI 2 for alkaline and PEM water electrolysis, is close to the 2018 value. For fuel cell mode it corresponds to a value of 3750 €/kW (electrical output), which is aligned with MAWP 2023 KPI for commercial mid-size fuel cells.