Design, Laboratory Characterization, Acceptance Tests, Commissioning and Start-up of a 2.6 MW High Temperature Steam Electrolysis System in a Refinery

Solid Oxide Electrolysis Cell (SOEC) technology is the electrolysis technology able to produce hydrogen with the highest efficiency, in particular when utilizing industrial excess heat to produce steam. Compared to other electrolysis solutions, SOEC technology is the most efficient on the market because the high-temperature-process significantly reduces the amount of electricity required. Though proofs-of concept have been achieved at different relevant scales, it has never been operated at a multi-MW scale in industrial environment and with heat coupling. The European project MULTIPLHY aims to install, integrate and operate a 2.6 MW SOEC system at a renewable products refinery in Rotterdam (NL). The unit, designed and manufactured by Sunfire, is made of 12 modules and is designed to deliver a flow rate of hydrogen of 60 kg/h at an operating temperature of 850 °C. Each module went through a factory acceptance test before shipment to Rotterdam. They were able to demonstrate an electrical efficiency of 84 % el,LHV as expected with the HTE technology (figure 1a). In order to meet the quality and pressure criteria of the refinery process, a Hydrogen Processing Unit (HPU) has been designed by Paul Wurth and its components validated. On NESTE side, the plot has been prepared in Rotterdam refinery, to receive the HTE and HPU units and to provide the requested power line and other utilities. The whole unit has been successfully installed (figure 1b) on site and the commissioning performed. The unit has been started. In parallel, long term stack tests have been performed at laboratory scale in order to assess the technology performance, durability and to validate the operation strategy before implementing it on the demonstration unit on site. Two types of stacks have been considered; made of either electrode supported cells, from CEA, or electrolyte supported cells, from Sunfire. Stacks with powers between a few kW and up to 10-to-20 kW have been evaluated. Due to the continuous improvement performed by both CEA and Sunfire, several generation of stacks have been characterized over the project duration. A harmonized protocol has been defined, which includes the recording of performance maps, several steps at constant current in thermoneutral conditions, as well as load point and thermal cycles. Altogether, 43,000 h of tests have been accumulated. Thanks to a smart operation strategy adopted for all stack types and sizes, consisting in compensating degradation by a stack temperature evolution over time, they could be operated over those durations without any hydrogen production loss, the current density being kept constant over the whole duration. Therefore, no hydrogen production loss has been recorded for any of the tests performed. Figure 1