Energy Transition, Distributed Energy Resources, and Flexibility Services: A Systematic Literature Review

The Paris Agreement's worldwide pledge to keep global warming to 1.5°C has sped up the energy transition, and with this, the deployment of renewable energy sources, increasing the demand for electrical systems' flexibility. To investigate the role of Distributed Energy Resources (DERs) in providing flexibility services that support the integration of nonconventional renewable energy (NCRE), this study performs a systematic literature review using the PRISMA approach. DERs enable decentralized, smart grid-based energy models that complement conventional centralized systems. According to the review, which examines 697 papers published between 2010 and February 2024, research has grown exponentially since 2015, especially in Europe. The study examines the functions of emerging agents, such as prosumers, aggregators, and Distribution System Operators (DSOs), and highlights important flexibility services, such as frequency regulation, voltage control, and congestion management, using bibliometric and content analysis. The results show that although DERs greatly improve grid resilience and the integration of renewable energy sources, several institutional, economic, technological, and social barriers prevent their complete implementation. New market mechanisms and regulatory frameworks that promote flexibility and active demand-side participation are needed to address these issues.