This study aims at estimating which, where, and how much storage and flexibility will be needed in the European power system to meet 2030 goals, in the perspective of the EUCO30 scenario.
The flexibility of a power system is its ability to accommodate both predictable and unpredictable changes in generation (e.g. coming from variable RES) and demand in a way that meets reliability standard and avoids (costly) curtailment. The ability of a power system to cope with large changes depends on the availability of flexibility means. Flexible thermal plants, storage technologies, demand response and RES with a better controllability can constitute important flexibility means. Furthermore, interconnections and reinforcements of the electrical grid are also a way to provide flexibility to the system, as it can help to balance the system over a wider area with smoother variations. In addition, the coupling of the electricity grids with the gas and heat grids can also provide additional flexibility through conversion and storage of energy which can be used to generate demand or generate electricity (power-to-gas and gas-to-power for instance).
The traditional power systems with low variable renewables rarely faced problems due to the cyclic operation constraints of the power plants. The demand changes were largely predictable, and the variation was slow. The baseload plants, which are inflexible, were first in the merit order as having the lowest variable costs and the mid peak load plants followed in the merit order, thus had to shut down and start up, but at well planned time intervals. On the contrary, in a system with high contribution by variable RES such as the future European electricity system, four sorts of variability occur, entailed by the different timescales of the temporal variabilities of RES and load. Firstly, the largely unpredictable variations in short or very short time intervals (e.g. drop of PV generation due to clouds, drop of wind generation due to wind gusts). Secondly, the largely predictable daily multi-hour variability, as for example due to solar. Thirdly, the also largely predictable variability over a few days due to meteorological conditions (e.g. wind regimes) or the weekday/weekend demand structure. Fourthly, the seasonal variability of the solar, wind and demand, that could lead to a weak availability of RES combined with a high load over a significant time period. The four types of flexibility need call upon different resources, in particular in terms of energy-to-power ratio and of time response. The short-term variability requires frequency reserves. The multi-hour daily and the weakly variabilities require power resources able to operate at low cost over a multi-hour schedule and at the same time have high ramping capabilities. The fourth type of variability requires long-term storage and/or thermal generating units in reserve. These variabilities occur in different points of the grid. Because the grid is not a copper plate (even within a country), balancing load and generation at a country level is not enough: congestions and voltage problems could occur at the transmission level or the distribution level. These grids constraints might have a significant impact on the storage/flexibility needs: they might determine where these means should be located, but they might also increase the needs (i.e. if they are not needed at the same time to balance the system at a national level and to solve local issues) and their characteristics (e.g. energy-to-power ratio) might be impacted.
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“The study is carried out for the European Commission and expresses the opinion of the organisation having undertaken them. To this end, it does not reflect the views of the European Commission, TSOs, project promoters and other stakeholders involved. The European Commission does not guarantee the accuracy of the information given in the study, nor does it accept responsibility for any use made thereof.”