Aggregated demand-side energy flexibility: A comprehensive review on characterization, forecasting and market prospects

Existing grids have been designed with traditional large centralized generation in mind; however, with the ever-increasing utilization of renewable distributed energy resources, the challenges of proper grid management have intensified. Demand-side energy flexibility is seen as one potential way to alleviate these challenges. Presently, residential demand-side energy flexibility has remained a largely untapped resource since individual prosumers are too small to provide enough capacity, thus necessitating the need for an aggregator. In view of the aforementioned, this paper conducts a literature review on the aggregated residential demand-side energy flexibility. The paper gives an overview of characterization methods of energy flexibility. The sources of residential energy flexibility are identified and categorized based on their flexibility characteristics. In addition, the quantification methods and parameters of energy flexibility are analyzed. Moreover, the forecasting methods of energy flexibility in the context of different flexibility sources are outlined. Additionally, an overview of existing markets and potential new emerging flexibility markets is given. The challenges and barriers faced by the aggregators attempting to enter flexibility markets are examined. Finally, the paper is concluded by providing a discussion of the key findings that summarize the current research directions and highlight the gaps for future development of aggregated energy flexibility.