Key district heating technologies for building energy flexibility: A review

In the background of the continued integration of renewable energy sources (RES) and the increasing flexibility on the demand side, the diversity and complexity of new technologies for heating present increased challenges for design and operation of district heating systems (DHS). This work first reviews the progress of the new generation of DHS, followed by providing an overview of investigations on building energy flexibility in the field of heating, with a focus on the characterization and quantification of energy flexibility, the realization of thermal flexibility, and the use of building thermal mass in demand side management (DSM). Different technologies were categorized and summarized according to the composition of the new generation of DHS. Control strategies such as model predictive control were also examined. In particular, the concept of building thermal battery is used to analyze buildings or prosumers thermal energy flexibility. Finally, new elements of DHS development and potential challenges were discussed.