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Advanced Electrolyser for Hydrogen Production with Renewable Energy Sources

Final Report Summary - ADEL (Advanced Electrolyser for Hydrogen Production with Renewable Energy Sources)

ADEL (ADvanced ELectrolyser for Hydrogen Production with Renewable Energy Sources) aimed at developing a new steam electrolyser concept. The approach was to lower the electrolyser operating temperature to increase its lifetime and to couple flexibility with thermal sources. The challenge is to maintain satisfactory performance and to optimise the energy transformation efficiency at the level of the complete system, including the heat and power source. Efforts comprised materials, cell and stack development and their testing under conditions derived from the renewable energy availability, the design of electrolyser units including the balance of plant components, and the conceptual integration of such units in case studies. The following main results have been obtained:
- The developed Generation 2 components show improved performance. Electrolyser stacks generally behave very well under load cycling conditions, but their base degradation rates remain above the project goal.
- Post-test SEM examinations show an alteration of the electrolyte/cathode interface but neither anode delamination nor chromium poisoning under electrolyser operating conditions. Possible degradation mechanism could be Ni removal from the interface. The phenomena is not sufficiently understood, and within the project, it was not possible to quantify to what extent this phenomenon explains the degradation (corrosion?).
- By coupling system simulation work with material development activities, specific test protocols were defined from the system requirements to test stacks under transient conditions and to define a realistic system operating window from materials constraints.
- System modelling shows that the electrolyser operating temperature (700 vs 800°C) has little impact on the efficiency and cost. The initial design temperature of 600°C is too low for SOE from a materials performance side. Pressurised operations have also limited impact as long as sweep air is used, as savings are set off by air pressurisation. As a consequence, optimised durability and performance is the critical couple to optimise, independent from electrolyser operating temperature.
- The allothermal source of heat is mainly required for steam generation. Consequently a large variety of heat sources can be considered. High temperature coupling provides limited efficiency gains with respect to the increased complexity and cost.
- High temperature electrolysers present very high power conversion efficiencies, decent load following capabilities and high capital costs. Different opportunities for electrolysis were controversially discussed:
o Grid balancing cases compete with Smart grids as strong alternative.
o Chemical storage (power to gas) as alternative for energy transport in the context of power-lines congestion or seasonal electricity storage with increased solar electricity production.
o Distributed hydrogen production for fuel cell cars, although hydrogen is currently considered more as a chemical than an energy carrier. Synthetic fuels derived from coelectrolysis using CO2 would couple renewable energy to standard energy markets more directly.
- Hydrogen production costs with high temperature electrolysis from renewable energy sources range from 6-17 €/kg calculated for four scenarios and are not yet fully competitive. The major cost is still the stack related to the limited lifetime. Another substantial cost part is the equipment for harvesting the renewable energy.
- The specifications of a demonstrator coupling an ADvanced ELectrolyser with a solar tower were elaborated.
The project achieved its objectives to a large extent, lacking progress in durability. Further activities in this field should focus on optimising performance, lifetime and costs independent from temperature constraints, and include a technology demonstration under real conditions.

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Olivier Bucheli
HTceramix SA