Development of tubular proton conducting electr olysers

摘要

High temperature electrolysis (HTE) of steam offers high efficiency of conversion of renewable and peak electricity to H2 and may increase efficiency further by utilising available sources of heat and steam from solar, geothermal, or nuclear power plants. They operate therefore ideally best at temperatures above those of the supplied steam (e.g.. 200-600 °C). Technologies developed to date comprise solid oxide electrolyser cells (SOECs) utilising oxide ion conducting electrolytes operating by virtue of necessity around 800 °C. They produce hydrogen on the steam feed side, and separation and drying of H2 cost energy and add plant complexity and footprint. In comparison, a high temperature proton conducting electrolyte will instead pump protons (H~+) and form dry H2, leaving O2 on the steam side. Such proton ceramic electrolyser cells (PCECs) thus require less separation process stages and can produce pressurised dry H2 direcdy. Protons exhibit lower activation energies than oxide ions, and ceramic proton conductors will be able to operate at lower temperatures - 600-800 °C - i.e., closer to the ideal range for integration with solar and geothermal plants. The main objective of the European project "ELECTRA FCH-JTI 621244" (2014-2017) is to develop and demonstrate scalable fabrication of tubular HTE cells with proton conducting electrolytes. The robust tubular cells will be assembled in a flexible 1 kW multi-tube module to produce pure dry pressurised H2 more efficiendy than competing technologies. The cells will reliably operate at temperatures up to 600 °C in steam electrolysis mode to promote efficient integration of PCEC technology in geothermal and solar heat power plants. We briefly report below main results achieved so far in terms of materials development, assembly and evaluation of performance. Results on process operability requirements for this system are reported in another contribution.