Hydrogen and other fuels are expected to play a key role as energy carrier for the transport sector and as energy buffer for the integration of large amounts of renewable energy into the grid. Therefore the development of carbon lean technologies producing hydrogen at reasonable price from renewable or low CO2 emitting sources like nuclear is of utmost importance. It is the case of water electrolysis, and among the various technologies, high temperature steam electrolysis (so-called HTE or SOE for Solid Oxide Electrolysis) presents a major interest, since less electricity is required to dissociate water at high temperature, the remaining part of the required dissociation energy being added as heat, available at a lower price level. In addition, technologies that offer the possibility not only to transform energy without CO2 emissions, but even to recycle CO2 produced elsewhere are rare. High temperature co-electrolysis offers such a possibility, by a joint electrolysis of CO2 and H2O, to produce syngas (H2+CO), which is the standard intermediate for the subsequent production of methane or other gaseous or liquid fuels after an additional processing step.These aspects are covered by the SOPHIA project.A 3 kWe-size pressurized HTE system, coupled to a concentrated solar energy source will be designed, fabricated and operated on-sun for proof of principle. Second, it will prove the concept of co-electrolysis at the stack level while operated also pressurized. The achievement of such targets needs key developments that are addressed into SOPHIA.Further, SOPHIA identifies different “power to gas” scenarios of complete process chain (including power, heat and CO2 sources) for the technological concept development and its end-products valorisation. A techno-economic analysis will be carried out for different case studies identified for concepts industrialization and a Life Cycle Analysis with respect to environmental aspects according to Eco-indicator 99 will be performed.