High-temperature solid-oxide electolyser (SOEC) is a technology for electrolysis of steam into hydrogen or co-electrolysis of steam and CO2 into syngas [1-6]. In this factsheet, the focus is on hydrogen production.
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Solid-oxide electrolyzers are most commonly used high-temperature electrolyzers  but it is also the least developed electrolysis technology . Solid-oxide electrolysers operate between 650-1000 °C and already offer impressively higher efficiency level (93%, higher heating value (HHV)) than other electrolyzers . The electrical efficiencies could be increased up to 97 % (HHV) by integrating derived heat and thermal coupling to exothermal processes such as chemical methanation .
Broadly, there are two categories of SOEC: electrolyte supported (operating temperature > 800 °C) and anode supported (operating temperature 600 -850°C). As it mainly requires ceramics and few rare materials for the catalyst layer, It has a substantial cost reduction potential in the future . Yet, the need for external high-temperature heat source (preferably from renewables such as concentrated solar power (CSP) or geothermal or industrial waste heat) at vincinity also provides challenges to its economic viability .
However, It can, in principle, also be operated without external high-temperature heat sources by using heat recovery, high-efficiency insulation, and compensating heat losses from electrical heating. Despite high capacity and efficiency, the electrolyser currently has reached life-time of 25000 operation hours and technology improvements such as stabilising components materials, developing new materials and lowering the operation temperature (500 -700 C) are being done to improve it further . Current capacities of operational SOEC system are in the range lower than 1 MW, however, a 2.6 MW SOEC system is currently being developed in Rotterdam within the framework of H2020 MULTIPLHY .All information in the datasheets is also available in ESDL (Energy System Discription Language). You can find them in the Energy Data Repository (EDR).