"The RelHy project targets the development of novel or improved, low cost materials (and the associated manufacturing process) for their integration in efficient and durable components for the next generation of electrolysers based on Solid Oxide Electrolysis Cells (SOEC). It is specifically tailored for 1) Optimisation of novel or improved cell, interconnect and sealing materials, 2) Achievement of innovative designs for SOE stacks to improve durability. As such, it is positioned as a bridge between currently good performing electrolysis cells and their efficient and reliable integration into advanced stacks to pave the way for the production of a new generation of electrolysers. To achieve these goals, the RelHy project is based on the coupled development of instrumented single repeat units and stacks and of associated simulation tools (from cell to stack scale). This mixed experimental and simulation approach will be used on several batches of materials - to give specifications for novel or improved materials and evaluate them, where special attention is paid to material compatibility (between electrodes, electrolyte, coating, interconnects and sealing). - to propose innovative designs able to overcome the present limiting parameters and to increase stack reliability, durability and performance. These material and design innovations will be validated at laboratory scale on a 25-cell stack prototype and its competitiveness will be assessed. Since the project is centered on R&D activities, the RelHy multidisciplinary European consortium is merging expertise from two university laboratories and three research centres already recognised for material development and cell production, instrumentation and testing, and modelling (DTU-Risoe, Imperial College, ECN, EIFER and CEA) and also from a fuel cell stack manufacturer that can produce electrolyser stacks (TOFC) and from an energy company (HELION) that can specify the operation conditions and assess the competitiveness of the innovative electrolyser prototype and its potential integration. The main issue addressed in the project is the simultaneous achievement of both, lifetime (degradation close to 1% for 1000 hr on single repeat units at 800°C) and efficiency (0.03 to 0.04 gH2/cm2/hr, i.e. approximately 1 A/cm2 with water utilisation >60% and a stack efficiency > 90%). These operation points and degradation values will yield an efficiency of up to 80% (LHV) at the system level with >99% availability. Cost issues will also be addressed by considering cost effective materials and processes in order to meet the “non energy” 1€/kg H2 target."