Facing the high share of variable renewable energy in the power system: Flexibility and stability requirements

Power systems with a high share of variable renewable energy (VRE) represent a challenge to system operators because of the increased flexibility requirements and stability. This study analyses the performance of a real power grid with a high penetration of VRE (mainly wind and solar photovoltaic). A rule-based power model is developed to simulate the power system behaviour. One European country was selected (Spain), with limited international interconnections and well-established decarbonisation scenarios by national and European orga-nisations. Flexibility requirements in the future power system were found through power plants' flexibility and stability constraints (i.e., inertia) and the expected changes in grid interconnection. The model results indicate that the ambitious targets for grid decarbonisation are not realistic because of these requirements. Considering the share of VRE for a sustainable transition (ST) scenario in 2030 (33% power generation) and in 2040 (35%), CO2-equivalent emissions will be reduced up to 157 and 159 kg CO2/MWh, respectively, which is well above Paris targets. Furthermore, no scenario allows meeting the expected environmental targets. Therefore, in power systems with more than 39% VRE, the results suggest that new technologies should be considered with emissions below-113 kgCO2/MWh, a maximum cost of-134 euro /MWh, and an inertia constant above 5 s.