Contact resistances between Crofer 22 APU and Crofer 22 H interconnect plates, Ni mesh and Ni-8YSZ anode interfaces were measured under an anode gas atmosphere (97%H 2 + 3%H 2 O) at 700 °C and 800 °C and current densities of 0 and 0.7 A/cm 2 for durations up to 3000 hours using the 4-point DC conductivity technique. Phase transformations within the steel samples close to the interface due to inter-diffusion of elements (Ni, Fe, Mn and Cr) were observed and analyzed. These phase transformations and the formation of oxide scales on steel as well as nickel mesh surface and grain boundaries do not seem to substantially affect the measured contact resistance with time.

HEXIS is developing and manufacturing SOFC-based micro-CHP systems for houses and/or small companies. This paper will present the long-term experiences on long-term and cyclic testing of fuel cell modules in lab tests as well as results on robustness and performance in the field. It was observed that degradation rates as low as approx. 0.3 %/kh, i.e. 13 mΩ cm²/kh on the short-stack level for over 50,000 h can be reached. These stacks have been analyzed with electrochemical impedance spectroscopy (EIS) at regular intervals, which can provide valuable insights in understanding fundamental degradation mechanisms for long term operation of SOFC stacks. Moreover, the paper will include highlights of new developments such as improvements on cell and stack level as well as new applications for the Hexis technology in general. Finally, the paper will outline some of the future challenges in Hexis’ development activities.

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HEXIS is developing and manufacturing SOFC-based micro-CHP systems for houses and / or small companies. While being a subsidiary of the Viessmann Group (until 06/2020) the company has been mostly focusing on the new generations of highly efficient (>95 % LHV) fuel cell modules – these modules are running in small quantities at customer sites - meanwhile, Hexis belongs to the h2e group and has expanded its technical activities. This paper will present the long-term experiences on long-term and cyclic testing of fuel cell modules in lab tests as well as results on robustness and performance in the field. It was observed that degradation rates as low as approx. 0.3 % / kh, i.e. 13 mΩ cm² / kh on the short-stack level for over 50,000 h can be reached. These stacks have been analyzed with electrochemical impedance spectroscopy (EIS) at regular intervals, which can provide valuable insights in understanding fundamental degradation mechanisms for long term operation of SOFC stacks. Moreover, the paper will include highlights of new developments since the new era for Hexis as an important part in the h2e group has started. These new developments are improvements on cell and stack level as well as new applications for the Hexis technology in general. Finally, the paper will outline some of the future challenges in Hexis’ development activities.