Impact of Building-Grid interaction signals on energy flexibility at cluster Level: Insights from two case studies

The increasing integration of renewable energy sources into power grids introduces operational challenges due to their time-varying electricity supply and limited predictability. Building-grid interaction (BGI) signals have emerged as a strategy to enhance energy flexibility, yet their impact on distribution transformer performance and aging remains underexplored. This study investigates the role of single vs. sequential BGI signals in two energy-efficient building clusters in Germany and Switzerland, using a co-simulation framework that integrates building performance simulation tools with numerical computing methods. Single BGI signals, such as electricity price and CO₂eq intensity, were compared to sequential BGI signals, which incorporate a transformer critical status signal to dynamically adjust flexibility responses. The results reveal distinct impacts on transformer aging and grid stress between the two clusters. In the German building cluster, sequential BGI signals effectively mitigated demand-driven transformer stress, reducing aging compared to single-signal cases, which impacted peak loads. Conversely, in the Swiss building cluster, photovoltaic feed-in was the dominant aging factor. Here, single BGI signals slightly lowered aging through improved self-consumption, while transformer critical status signals occasionally increased aging by reducing self-consumption during overload events. Across both clusters, energy and cost savings were analysed, with building-grid interaction signal integration successfully maintaining thermal comfort boundaries. These findings provide insights for energy flexibility aggregators on the potential trade-offs between grid stability, economic efficiency, and emission reductions in flexible building operations.