A systematic review of systemic challenges and transition strategies for integrating renewable energy sources into conventional electricity generation in the European Union

This review investigates the integration of renewable energy sources (RES) into the European Union's electricity system, focusing on the infrastructural, regulatory, and systemic complexities encountered during the transition to a low-carbon model. The rising penetration of intermittent sources such as wind and solar has created operational challenges for grid stability, dispatchability and overall system flexibility. Empirical studies highlight the growing role of energy storage technologies, sector coupling and coordinated planning tools in addressing these challenges. Considerable divergence persists among national strategies because of heterogeneous climatic, geographic and socio economic conditions, which shape the timing and scope of fossil fuel phase out, especially in coal dependent member states such as Germany and Poland. Financial instruments ranging from tax relief to auction based procurement and shared ownership models have been implemented. However, their effectiveness remains constrained by site specific factors, including resource variability and differing levels of public engagement. Regulatory heterogeneity across EU member states, particularly in the application of renewable portfolio standards, continues to impede convergence in integration efforts. Environmental assessments of high RES penetration scenarios indicate substantial emission reduction potential when integration is aligned with local generation patterns and infrastructure capabilities. The review traces the structural interplay between technological development, institutional arrangements and socio economic determinants in shaping the evolving configuration of the EU electricity sector.