Climate variability on Fit for 55 European power systems

3. To assess power system dynamics during the most prevalent weather patterns in order to consistently link an event (e.g., reduced availability of renewable resources) in one region with the same event in other regions. Furthermore, the results suggest the possibility of using weather patterns to predict power systems’ variables using seasonal/sub-seasonal forecasts in Europe as already explored by [57, 58]. Our findings are, as such, of relevance to various audiences involved in the analysis of the European power system, ranging from researchers, to energy system planners and policymakers. First, for energy system planners, for example for system operators, power generation com- panies or national regulatory authorities, the climate variability and co-variability are essential to consider for the robust configuration and dimensioning of the power system. To provide for system adequacy, planning decisions need to incorporate variability at the system level over an appropriate time. Moreover, the patterns of co-variability shown in this study offer opportunities for complementarities in system planning that could be realised as synergies through network planning or could result in enhanced revenue and risk hedging opportunities for market participants. Indeed, we find power systems operations between two or more European regions to be largely correlated. While co-variability is, in general, stronger between neighbouring regions, we also find an evident correlation between some distant regions: for example, the Iberian pen-

insula and the Northern region exhibit a negative correlation for wind generation, net demand and net export of electricity. Such co-variability is important for system planners as its impact on the design of resilient energy systems may be fundamental to improving the integration of renewable energy sources into European power systems [23]. Our results are among the first to show the comprehensive effect of weather patterns on European power system dynamics. While the results for wind generation are consistent with [23], our findings also create insights into cross-border electricity exchanges and the electricity demand. The results thereby show how the use of power system models enables the quantifica- tion of the daily variability of the main energy variables, including aspects of importance for energy system planning purposes (e.g., curtailment and storage operations). Second, for pol- icymakers, the results offer insights into the potential impact on power systems of the transi- tion towards clean primary and mostly variable renewable energy supply. This calls for anticipatory policy and regulatory design as the increasing variability will accompany changes in capacity utilisation and hence also the economics of power system assets. For example, in the recently adopted electricity market design reformation, the European Commission recom- mends enhanced flexibility in future European power systems in order to accommodate vari- ability in demand and supply patterns, as these are highly dependent on climatic variables [1].

This study is therefore intended to engage policymakers in order to ensure that the impact of climate variability on power system security is adequately assessed. We find coupling between regions to be at the same time potentially beneficial and a threat to system adequacy and security of supply. For example, the negative correlation of hydro- power generation between two regions means that one of the two regions can potentially sup- ply the flexibility needed by the other region with lower levels of water in its hydropower reservoirs. On the other hand, a positive correlation of renewable sources (e.g., wind power) might mean that low-wind periods are potentially extended to multiple regions, leading to large-scale supply/demand issues. Climatic conditions are not the only source of uncertainty but, especially in systems with large shares of renewable energy generation, they are a key contributor. Variability of produc- tion and demand play an important role in the methodology for the short-term and seasonal PLOS ONE Climate variability on Fit for 55 European power systems PLOS ONE | https://doi.org/10.1371/journal.pone.0289705 December 20, 2023 12 / 16