Thermal storage capacity in the entire building stock of Denmark for energy flexibility strategies and building-to-grid services

Buildings have an enormous untapped potential to perform demand response thanks to their energy flexibility. These building energy flexibility actions mainly rely on different forms of energy storage (e.g., electric batteries, water tanks) or dispatchable on-site energy supply and services. The thermal inertia of the indoor environment also holds a large energy storage capacity, which can easily be leveraged with heating/cooling temperature setpoint modulation. If this approach has proven promising for building demand response, large-scale capacity estimates are lacking. This article gives an estimate of the heat storage capacity in the indoor environment of the entire building stock in Denmark. The latter is comparable to that of all combined batteries in large fleets of electric vehicles or the entirety of industrial-size storage tanks in district heating plants. The indoor environment of the building stock is a readily available and massive thermal storage tank awaiting to be used to help the grids at minimum costs.