Towards a defossilized building sector with field tests in the lab: Review, development, and evaluation

The transformation process in the building sector towards future city concepts requires changes in our society that aim for significant emission reduction until 2045. Currently, buildings in Germany are constructed and operated in such a way that no changes need to be made to them for decades. Therefore, any upcoming changes that do not achieve the climate goals must be avoided immediately. However, making the optimal decision for a change is complex due to (a) multi-domain (e.g., design and control), (b) multi-scale (e.g., single-family building and urban energy system), (c) multi-stakeholder (e.g., users and practice), and (d) long-term implications (up to decades). Conventional testing facilities and methods do not account for the integration of (a)-(d). Therefore, their technology readiness level is limited by 6. This paper introduces an approach that aims at (1) a multi-domain and multi-scale approach by applying process systems engineering to the building sector and that aims at (2) stakeholder integration already in the research process by applying the living lab approach. We combine the two methods, yielding a field test in the lab infrastructure pushing the technology readiness level to 7–8. In all, it consists of five test benches (Refrigerant Cycle Lab, FlexFass, RT-Lab, Raumklimalabor, and InFis). This work focuses on the Refrigerant Cycle Lab. Its concept is based on two further Hardware-in-the-Loop test benches which are extended by a safety system that ensures automated operation dedicated to heat pumps with flammable refrigerants. In two case studies, we show that field tests in the lab allow multi-domain and multi-scale testing. Both aspects support accelerating the transformation process towards a defossilized building sector. In the next step, the combination of test benches at different locations is promising to reduce the need to set up identical experiments at different locations. In the long term, the laboratory is designed to include external stakeholders to avoid time-consuming iterations and can, therefore, save resources, time, and money for our complex transformation process. [Display omitted] •Hardware-in-the-Loop environments for heat pumps handling flammable refrigerants are key for field tests in the lab.•Experiments under quasi-field test conditions push the technology readiness level of conventional testing methods (4–6) towards field tests in the lab (7-8).•Capturing the design and control domain and potential stakeholder