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

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 cm2. 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 WDC 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 WDC 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%.

A 5 kW-class reversible Solid Oxide Cell (rSOC) system was developed and experimentally investigated at the Forschungszentrum Jülich in Germany. The main component of this system is the well-established Jülich Integrated Module, which consists of a 40-layer SOC stack (composed of four 10-layer sub-stacks) with an active cell area per layer of 320 cm². The other necessary system components, such as the evaporator, condenser and blowers are compactly arranged in the vicinity of the Integrated Module. In fuel cell mode, a power of 5374 WDC at 500 mA cm-2 and a maximum fuel utilization of 97.3% was achieved, which resulted in a DC electrical system efficiency of 62.7%. Furthermore, in electrolysis mode, a power of -14347 WDC was attained at 887 mA cm-2. At this operating point, the system’s DC efficiency reached 70% at a steam utilization of 85%.

At the Forschungszentrum Jülich, 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°C. During the test phase, a system fuel utilization of 93% and electrical efficiencies of more than 60% could be demonstrated with the subsystem.

In 2018, a 5/15 kW reversible solid oxide cell system was developed and successfully operated. Based on these positive outcomes, a larger system in the power class of 10/40 kW was planned, with the well-established “Integrated Module” constituting a core element. This module consists of four 20-layer sub-stacks, two heat exchangers, and five heating plates. The basic structure was retained as per the previous system and the surrounding balance of plant components were adjusted in accordance with the higher power level. This adaptation is outlined using the example of an air heat exchanger. A possible efficiency optimization in electrolysis mode via a highly efficient steam generation process is also described and substantiated by experimental results.