The ELECTRA project1 of the FCH JU – taking proton ceramic electrolysers (PCEs) from button-cell to pressurised tubular stack level – is concluding in 2017. ELECTRA has developed PCEs based on proton conducting barium zirconate as electrolyte. Like solid-oxide electrolysers (SOEs) they utilise available heat or steam from waste or renewable geothermal or solarthermal sources to increase the electrical efficiency. PCEs operate at intermediately high temperatures – up to 700°C – and unlike SOEs they produce directly dry pressurised hydrogen and oxygen diluted with steam. Hence the hydrogen is produced at the total pressure of the unit in a simpler, more efficient, and safer process than competing electrolysers.
The project and its partners have developed materials and procedures for production of segmented tubular cells, involving extrusion, co-sintering and novel sealing technologies. Novel oxygen+steam-side electrode materials with good electrocatalytic properties and stability in steam have been applied on tubular segments to yield unprecedented currents and hydrogen fluxes in PCEs. A multi-tubular high pressure module with capability to monitor and replace individual tubes has been designed, built, and tested. The balance of plant and techno-economics of the integration of PCEs with various sources of electricity and heat or steam have been modelled. Mass-produced PCEs may be inexpensive and will, with available heat or steam, produce hydrogen competitive to e.g. alkaline electrolysis.
The project has also tested and modelled co-electrolysis of CO2 and steam. In so-called co-ionic mode using both proton and oxide ion conduction, it produces syngas at a CO:H2 ratio of 1:2, variable by varying the materials and conditions.
Prof. Truls Norby at University of Oslo (UiO) has led a team consisting of institutes SINTEF (NO) and ITQ/CSIC (ES), SMEs Carbon Recycling International (IS) and Marion Technology (FR), and industries Abengoa Hidrógeno (ES) and CoorsTek Membrane Sciences (NO). The project has run from 2014 to 2017. Partners are now pursuing PCE technology of multi-module units of 10 kW and above to deliver hydrogen at 30-50 bar – serving industries with competitive hydrogen where heat/steam and peak/renewable electricity are available.
1. High temperature electrolyser with novel proton ceramic tubular modules of superior efficiency, robustness, and lifetime economy, FCH JU Grant agreement 621244, 2014-2017.