A comprehensive review of sector coupling as a strategy for power system flexibility

The European Union's 2030 climate targets require a fundamental transformation of the energy system, emphasizing the integration of renewable energy and the electrification of key sectors such as heating, cooling, transportation, and industry. The inherent unpredictability of renewable energy sources like wind and solar, however, makes this transition extremely difficult and creates operational uncertainties, makes system planning more difficult, and puts pressure on policy coordination. These issues affect the financial sustainability of energy systems in addition to grid stability and reliability. As a result, sector coupling is comprehensively reviewed in this paper as a strategic method to improve system flexibility. Sector coupling enhances the integration of relevant technologies, such as battery storage, hydrogen systems, and power-to-x solutions, and allows for synergies among energy carriers by connecting the electrical sector with other domains, such as transportation, heating, gas, and hydrogen. Along with the technical aspect, this study investigates how market design, financial innovation, and regulatory frameworks facilitate cross-sector investment and integration, which helps the clean energy transition and improves system flexibility overall.