Exploring demand side flexibility through aggregation of individual devices

As the penetration of variable renewable energy sources increases, maintaining balance between supply and demand becomes challenging, which necessitates increased flexibility in operations across both sides of the energy system. While substantial research has focused on supply-side flexibility, this work shifts attention to demand-side management and reviews the flexibility potential achieved through the aggregation of diverse loads, including non-controllable loads, shiftable loads, interruptible loads, thermostatically controlled loads and home battery energy storage systems. Additionally, the participation of aggregated loads in various markets, particularly in day-ahead and balancing markets, is investigated showing substantial cost saving potentials: aggregation demonstrates 1 %–44 % operational cost reduction in the day-ahead market, while 6.7 %–43.8 % in balancing market through ferquency reserve services. Multi-market participation strategies combining different load types can achieve up to 50 % overall cost reductions, with larger aggregations showing higher optimization potential through advanced clustering methods. By addressing both technical and economic aspects, this review aims to guide aggregators and policymakers in optimizing demand-side resources to improve grid resilience, enhance renewable energy integration, and maximize user participation in flexibility markets.