Analyzing the future role of power transmission in the European energy system

To integrate renewable energy generation, our energy systems need to become more flexible than they are today. While many studies on planning flexibility options have emerged in the last years, the literature still lacks of a better understanding of investments into power transmission infrastructures. Here, our study makes three contributions. We aim to re-understand the role of power transmission in the context of, first, the many available and competing flexibility options; second, the major uncertainties in societal preferences on energy technologies; and third, different ways of modeling power flows in energy system optimization models. Our methods base on the energy system optimization model (REMix) for planning the transition of Europe’s energy system. We also consider interactions with the heating and transport sectors. A broad set of scenarios explores how investments in transmission are affected by certain strategies regarding grid expansion, solar power imports and hydrogen generation. The power flows in the transmission grid are modeled in three different ways, once as transport model, as direct current power flow and with profiles of power transfer distribution factors. In all scenarios explored, deploying transmission systems contributes significantly to system adequacy. Storage technologies are needed, but investments in transmission are at least two times higher. Imports from concentrated solar power plants in North Africa call for larger transmission systems. Combined with hydrogen systems the need for transmission culminates. If investments in new power transmission infrastructure are restricted (for example as a consequence of social opposition), grid expansion can be replaced by additional power generation and storage technologies for slightly higher system costs. The different ways of modeling the power flows within REMix caused only minor changes on the investments in load balancing technologies. At least with a spatial resolution of mostly one node per country, it does not seem to matter how the power flow distribution is modeled. As next steps, we recommend improving the spatial distribution to avoid underestimating the need for flexibility due to aggregation of spatially explicit information. Our results are relevant for energy policy makers as well as energy modelers.