As part of the research project “Lean gas CHP”, we installed our mobile Stirling CHP on the site of a landfill and powered it with landfill gas over a period of 4 weeks in January 2020. Unlike previous field tests, the cooling circuit had to be maintained frost-proof. We were very curious about how the CHP would behave because of the higher viscosity of the coolant on the one hand and the relatively narrow cross-section of the Stirling engine’s cooler on the other hand. In addition, the coolant has a lower heat capacity compared to pure water. We invite you to take a look into the test protocol of BEST Research/ Wieselburg and to particularly pay attention onto the excellent overall efficiency of 30 %.