& challenge

The Prometeo project aims to validate an innovative system prototype for the production of renewable hydrogen using solar fuels, moving the technology readiness level from TRL 3 to TRL 5.

By testing a large SOE stack in electrolysis mode Prometeo aspires to move a step forward in SOE performances to produce hydrogen from renewable energy sources.

The main challenge in Prometeo is to optimize the coupling of the Solid Oxide Electrolyser (SOE) with two intermittent renewable sources: electricity from renewables (PV, wind, or variable grid power) and high-temperature solar heat from Concentrating Solar (CS). The SOE system will be supported by a Thermal Energy Storage (TES) to balance solar heat supply in steam generation for high-temperature electrolysis. The integrated system aims to increase efficiency, flexibility and reliability of the electrolysis, while minimizing the production costs for hydrogen.


System prototype optimization

to advance the integration of the SOE with intermittent sources of renewable electricity and heat.


Thermal energy storage system

to buffer solar heat supply and minimize thermal cycling of the SOE in different operating modes


Renewable energy integration

to test the prototype for 1,000 h in terms of utilization factor, efficiency, reliability and durability.


Operational models optimization

to consider different working phases such as transient, nominal, partial load, start-up and stand-by operations.


Scale-up and exploitation roadmap

to consider future development scenarios by industrial end-users in the energy and chemical sectors


Techno-economic and sustainability assessment

to estimate the economic and environmental performances of the prototype.

The expected impacts address the call topic FCH-02-2-2020 “Highly efficient hydrogen production using solid oxide electrolysis integrated with renewable heat and power”.

The impacts are linked to the reduction of hydrogen cost produced from RES to support the deployment of hydrogen in industrial sectors and to lower the carbon footprint of the European economy. The topic specifically addresses high-temperature Solid Oxide Electrolysis (SOE) to be integrated with renewable heat as a source of cheap steam.

Technical impacts

  1. Hydrogen production  ≥ 98% equivalent to 15 kg/day H2;
  2. Electrical efficiency ≥ 85% and specific energy consumption <39 kWh/kg H2;
  3. Efficient operation strategy of SOE coupled with renewable electricity and heat for grid integration and balancing;
  4. SOE technology improvement for cheap green H2 production independently from constant RES supply.

Socio-economic impacts

  1. Proof of concept for sector coupling between electric and gas grids considering on-grid and off-grid applications, and different geographical and plant scales;
  2. Analysis of new market opportunities for SOE by considering the prototype upscaling from 1 to 100 MWe;
  3. Demonstrate the use of solar thermal technology to process heat for industrial applications.
ID Key Performance Indicators (KPI) Definition Unit Target
F-prod Hours of SOE operation (with hydrogen production) vs. total test hours % ≥98%
F-op Hours in which the SOE has been kept “hot” ≥ 650°C (i.e. ready-to-start) vs. total hours
F-tes Hours in which the SOE has been driven with heat directly discharged from the TESvs. total hours % ≥50%
T-op Hours of experimental validation runs of the prototype hours ≥1,000 hr
R-av Average H2 production rate: tot H2 produced vs. tot. hours of experimental validation of the prototype kgH2/day ≥ 5 kgH2/day
R-max Maximum measured instantaneous hydrogen production rate a full-capacity kgH2/day ≥ 15 kgH2/day
Loss Measured efficiency production loss after 1,000 hours operation % <1.2%
Eff-% Power-to-hydrogen energy conversion efficiency of the heat- integrated SOE system (LHV basis) % ≥ 85%
Eff-w Power-to-hydrogen conversion efficiency of the heat- integrated SOE system kWhe/kgH2 < 39 kWhe/kg
Sol-% Solar-to-Hydrogen enegy conversion efficiency: from global solar radiation to H2 energy (LHV basis) % ≥ 10%
Eff-tes Heat-to-TES-to-Heat conversion efficiency of the TES system on charge/discharge cycles % ≥ 85%
LOCH Levelized Cost of Hydrogen for the medium-long term (>2030) €/kgH2 ≥ 2 €/kgH2
C-tes Cost of the Thermal Energy Storage system per kWh thermal capacity €/kWht < 20 €/kWH
CAPEX Capital investment of a fully-integrated multi-MW SOE ready for connection to heat & power sources €/kWe < 300 €/kWe
O&M P&M costs of a fully-integrated 25 MWe SOE (not including electicity and water costs) €/year <750 k€/year