Capturing Battery Flexibility in a General and Scalable Way Using the FlexOffer Model

To solve the problems caused by the intermittent generation of Renewable Energy Sources, the concept of energy flexibility is of utmost importance, and batteries are devices with high potential in this regard. However, current exact mathematical models specifying battery flexibility cannot scale (exponentially growing runtime) with long time horizons and many batteries. In this paper, we propose to use the FlexOffer (FO) model for this purpose, because: 1) FO is a general model, capturing all types of flexible assets in a unified format and 2) being approximate, it scales very well in terms of number of devices and time horizons. First, we describe the different types of FOs: standard, total-energy constraint and dependency-based (DFOs). Then, we present and discuss FO generation techniques, and provide an analytic method for generating DFOs. Finally, we perform simulations for measuring flexibility in economic terms and time needed for optimization and aggregation. We show that DFOs retain most of the flexibility, while vastly outperforming exact models in optimization and aggregation speed.