These resources, however, are difficult to control and monitor, they are significantly smaller in size than traditional generation units, are very numerous, and are highly distributed over the grid. As a result, a new approach to managing energy demand is emerging that introduces the figure of the aggregator, which allows utilities to operate as a single entity to provide greater capacity and flexibility to balance the system. In this new vision, the users of the electricity system, whether they are passive users or prosumers, represent a significant potential for the flexibility of the entire system, for example, in terms of their willingness and ability to vary their consumption profiles.

This report analyzes the issue of flexibility by considering several aspects. First, the regulatory environment that motivates and fuels interest in this issue is analyzed, highlighting the importance of users becoming aware of their new role within the electricity system. The problem of defining and mathematically representing flexibility in order to formulate appropriate optimization problems on the aggregator or network operator side, such as participation in the service market, is then investigated.

To this end, a number of models, commonly discussed in the literature, which can be used to describe electric loads are reviewed, and the main approaches proposed for solving the flexibility aggregation problem are then reviewed. In addition, with reference to the Italian building stock, an approach is presented for the modeling and characterization of buildings, aimed at the related energy simulation in dynamic regime.

This study represents a preliminary step for an assessment of thermal and electrical flexibility of residential buildings, also with a view to an integration between different energy carriers. Finally, a survey is reported that was developed to first identify the energy needs and possible flexible loads of industrial users, and then to communicate the potential participation of these users in grid services.