Low-parameter linear model to activate the flexibility of the building thermal mass in energy system optimization

As buildings are becoming an integrated part of the energy system, the potential activation of the thermal mass as a source of flexibility needs to be considered in energy system modeling. Since energy system models represent larger and integrated systems, often as linear programs, the thermal mass activation of buildings needs to be formulated accordingly to be included as a flexibility asset in the energy system optimization problem. The article provides a linear model of the energy stored in the building thermal mass compared to a reference operation scenario without demand response. This formulation in relative terms significantly reduces the number of model parameters to be identified using field measurements and enables the analysis of the aggregated energy flexibility in energy system models. The thermal mass activation is demonstrated in a case study which also includes validation. In addition, a comparison of the thermal mass activation and batteries is made. It is concluded that the provided linear deviation-based formulation is appropriate for representing the potential of flexibility provision from the thermal mass in buildings for the purpose of energy system planning.