In 2018, a 5/15 kWDCreversible solid oxide cell system was developed and successfully operated by Forschungszentrum Jülich. Based on the knowledge gained with this first system, an optimized system in the power class of 10/40 kWACwas developed afterwards in 2019 that uses the well-established Integrated Module. This module consists of four 20-layer sub-stacks, two heat exchangers and five heating plates. It represents the main components of the system. The basic system layout was retained in general from the previous system and adjusted in accordance with the higher power level, as well as the supporting balance of plant components. The layout of the demonstrator system and its results are described. During the experimental evaluation in fuel cell mode, the system could provide an electrical output power from 1.7 to 13 kWAC. The maximum system efficiency of 63.3% based on the lower heating value (LHV) could be reached at a system power of 10.4 kWAC. This operating point was also analyzed regarding the temperature distribution in the stack and efficiency losses. In electrolysis mode, a maximum efficiency of 71.1% (LHV) was achieved with an electrical power input of −49.6 kWAC. At this operating point, about 11.7 Nm3h−1of hydrogen are generated. The stack temperature distribution and the efficiency losses are also analyzed for the electrolysis mode. Finally, the potential for the efficiency optimization through higher heat integration in this mode is experimentally evaluated and discussed.

A 5/15 kW-class reversible Solid Oxide Cell (rSOC) system was developed and experimentally investigated at the Forschungszentrum Jülich GmbH. The main component of this system is the well-established Jülich Integrated Module, which consists of four 10-layer SOC sub-stacks with an active cell area per layer of 320 cm 2 . The other necessary system components, such as the evaporator, condenser and blowers are compactly arranged in the vicinity of the Integrated Module. The system’s total operation time was more than 9000 h, in detail 2607 h in fuel cells, 6043 h in electrolysis and 448 h in hot standby mode. In fuel cell mode, a power of 5374 W DC at 0.5 A cm −2 at a fuel utilization of 97.3% was delivered, which resulted in a DC electrical system’s efficiency of 62.7% (LHV). Furthermore, in electrolysis mode, a power of −14347 W DC was consumed at 0.89 A cm −2 . At this operating point, the system’s DC efficiency reached 70% at a steam utilization of 85%.

With their high electrochemical efficiency, solid oxide fuel cells (SOFCs) and solid oxide electrolyzers (SOEs) offer viable means of reducing energy sector greenhouse gas emissions and storing surplus renewably‐generated power. At present, these systems have operating temperatures of over 600 °C. During start‐up, following cooling or in an emergency shut‐off situation, a premixed safety gas is necessary which prevents damage to the cell's anode substrate. To date, safety gas has been industrially produced and stored in compressed gas cylinders. Given an SOFC system's size, these cylinders must be transported and stored in close proximity and replaced following gas expenditure. The storage space required, as well as the continuous replacement of gas cylinders, increases system size and costs. This paper presents a solution to this problem in the form of a specially developed safety gas generator that generates an on‐demand synthetic safety gas via the system's infrastructure. The functionality of this component is experimentally validated in tests conducted with a 4‐cell stack.

At the Forschungszentrum Julich, an SOFC subsystem was built and operated. This subsystem consists of the well-established integrated module, combined with a low temperature off-gas recirculation loop. The recirculation loop is driven by a hermetic side-channel blower that operates at gas temperatures of 160 degrees C. During the test phase, a system fuel utilization of 93% and electrical efficiencies of more than 60% could be demonstrated with the subsystem.

Systems based on planar SOFC stacks have a great potential to become compact high efficient power plants. At Forschungszentrum Julich system technology is under development aiming at a 20kW demonstration plant. An important challenge is to realize a compact and efficient system. To achieve this, Julich has invented an Integrated Module, which incorporates all hot parts of the system. After a few years of development four stacks with a nominal power of 5kW were assembled and characterized with proper quality. After integrating them into the system operation was started and 21.3kW gross power were achieved. Because of a leakage in the periphery the test had to be interrupted after 550h of operation under load. Because repair would have taken too long, the test was continued with two modules of 5kW power each. The system was in operation under load for 4,000h.