Dealing with renewables integration: A comparative study of Belgian and French balancing systems

The rise of renewable energy creates new real-time flexibility challenges for Transmission System Operators (TSOs), affecting the demand for reserve energy. In parallel, reactive and proactive balancing philosophies continue to coexist in Europe. They differ primarily in the incentives provided to Balancing Responsible Parties (BRPs) to support the TSO in actively maintaining system balance, with greater involvement expected under the reactive approach. While there is a harmonization push at the European level towards the reactive model, this study analyzes the impact of renewables on reserve energy demand in two countries relying on contrasting balancing approaches: Belgium’s reactive system and France’s proactive system, which is transitioning to comply with EU directives. Using a SARIMAX model on 2021 data, we find an asymmetrical effect of renewables on reserve energy needs, leading particularly to an increase in downward activation to cope with moments of overproduction. It confirms a pattern already observed in the French context but allows for extending the observation to a very different balancing model, the Belgian one. Additionally, this comparative framework highlights the Belgian reactive model’s greater ability to mitigate the asymmetrical effect. Importantly, we show that this smoother effect observed in Belgium is associated with a lower balancing cost for the TSO relative to load. Finally, we identify market design developments that would mitigate the asymmetric phenomenon in both systems.