Demonstration of High-Temperature Co-Electrolysis Systems
Authors: Schwarze Konstantin , Meisel Peter , Blumentritt Robert , Hauptmeier Karl , Posdziech Oliver 
Published: July 2021

The High-Temperature Electrolysis (HTE) process based on Solid Oxide Cells (SOC) uses green electricity to efficiently generate a renewable molecular feedstock for industry and mobility. Therefore, it is a key technology to link the electricity sector with other industries and to evolve the electricity transition into a full energy transition. After years of development HTE is now on the threshold to reach market readiness and competitiveness compared to other electrolysis technologies. Yet, HTE still needs to proof its advantages and reliability in relevant industrial environments over relevant operation times.
The present paper shows the latest achievements of Sunfire’s development within the product lines Sunfire-HyLink (steam electrolysis systems) and Sunfire-SynLink (co-electrolysis systems).
The world’s largest HTE is a HyLink implementation that was installed in late 2020 in Salzgitter (Germany) within the GrInHy2.0 project. It is a 720 kWAC electrolyzer with a compression and drying unit designed by Paul Wurth. It produces up to 200 Nm³/h hydrogen from simple heating steam for the local iron-and-steel works operated by the project partner Salzgitter Flachstahl. The commissioning was finished in February 2021 and the system is now in operation for approx. 1,000 hours. First results from both dynamic and stationary operation will be shown. Also the achieved efficiency and production rate in normal operation will be evaluated for full load and part load. Additionally the potential to reduce the carbon footprint by replacing “grey” hydrogen with “green” produced by HTE will be analyzed.
While the HyLink system in Salzgitter consists of eight smaller Generation 1 modules that are integrated in one 40’ ISO container, Sunfire is already testing a next generation module in its testing facilities in Dresden (Germany). The Generation 2 module is designed as SynLink module from the scratch and provides a capacity of 240 kWAC, i.e. 62.5 Nm³/h production rate. The design allows for operation in either steam electrolysis mode or co-electrolysis mode. It also includes the capability to internally reform hydrocarbons, which enables the integration of carbon-rich residual gases from connected processes like Fischer Tropsch Synthesis, Methanization or biogas plants. The present paper describes the major design improvements and findings from the module tests in Sunfire’s test facilities.
Finally, an outlook on next development steps and upcoming project is given. On module level Sunfire’s designing a Generation 3, which is a first MW-scale module. On project site Sunfire will established itself on the MW-scale with both HyLink and SynLink projects. HyLink will be scaled up to 2.5 MW within the MultiPLHY project at a Neste refinery in Rotterdam (Netherlands). SynLink will be demonstrated on a multi-MW scale by Sunfire’s daughter company Norsk e-Fuel in Heroya (Norway). The detailed outlook will provided insight on how HTE will play a major role in the near future to efficiently produce renewable feedstock for an economy with a drastically reduced carbon footprint.

Figure 1