Hydrogen PROduction by MEans of solar heat and power in highTEmperature Solid Oxide Electrolysers

Hydrogen from solar energy.

Prometeo aims to improve high-temperature solid oxide electrolysis (SOE) for the production of green hydrogen by making the most efficient use of heat and power generated from solar energy


PROMETEO is a European Horizon 2020 project that aims to develop an innovative prototype based on high-temperature solid oxide electrolysis (SOE) for the production of green hydrogen by making the most efficient use of heat and power generated from solar energy. PROMETEO will use the solid oxide technology to build a 25 kWe prototype electrolyser capable of producing 15 kg of hydrogen per day, with the potential to be replicated on the MWe industrial scale. The project will address the intermittent supply of solar energy by developing an innovative system to manage the energy conversion and re-generation phases.

PROMETEO will be designed to meet end-users’ needs for green hydrogen in three industrial applications: injection of hydrogen into the gas grid (SNAM, Italy), chemical storage of renewable electricity (Capital Energy, Spain) and use of hydrogen for ammonia and fertiliser production (Stamicarbon, the Netherlands).

The project will last three- and a half-year and it is supported by funding of € 2.5 million from the European Fuel Cells and Hydrogen Joint Undertaking (FCH JU). The final goal of PROMETEO is to move a step forward in the use of hydrogen for industrial decarbonization by 2030.



The main challenge in PROMETEO is to optimize the coupling of the SOE with two intermittent renewable sources: non-programmable renewable electricity and high-temperature solar heat from Concentrating Solar (CS) systems with Thermal Energy Storage (TES) to supply solar heat when power is made available aiming at producing the steam needed, resulting in an increase of the electrolysis efficiency.

For this purpose, a fully integrated optimized system will be developed and tested, where the SOE combined with the TES and ancillary components will efficiently convert intermittent heat and power sources to hydrogen. Particularly, attention will be focused on thermal insulation aspects, due to the big impact of any thermal losses on overall efficiency of the system.

To this end, PROMETEO targets the following goals:

1) optimize the integration of the SOE at system level to cope with intermittent heat and power sources and best valorise inexpensive electricity (e.g. by PV or wind);

2) develop dedicated solar steam generators with heat storage to buffer the intermittent nature of solar heat and minimize thermal cycling of the SOE in variable operation, considering customized solutions derived from previous experience and developments in the CSP field (i.e. use of inorganic salts and integrated heat exchangers);

3) develop a fully-integrated system at the prototype level (at least 25 kWe electrolyzer with at least 15 kg/day hydrogen production capacity) combined with RES and validated in a relevant environment (TRL 5), to be tested for at least 1,000 hours with performance evaluation: utilization factor, efficiency, reliability and durability;

4) developing optimized operational models to manage transients, start-up and stand-by operation thanks to the above-mentioned prototype;

5) system scale-up and industrial exploitation roadmapping, considering cases of practical interest under different scenarios carried out by industrial end-users, including:
o power grid balancing to facilitate RES integration in the grid;
o renewable hydrogen production as feedstock for the chemical industry;
o power-to-gas applications, coupling electric and gas grids (i.e. hydrogen injection in gas grid);

6) techno-economic & sustainability assessment of the process.



This project receives funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 101007194. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe Research.