Optimal operation of district heating networks through demand response

In this paper, an optimization method aiming at minimizing the thermal peaks in district heating networks is proposed. The method relies on a thermo-fluid dynamic model of both the supply and return networks and permits to analyze the opportunities for thermal peak shaving through “virtual storage”. The latter is obtained through variation of the thermal request profiles of the users. The presence of a peak in the morning is due to the shut-down or attenuation of the heating systems during the night, which lead to a dramatical increase of the thermal request early in the morning. The peak compromises a full exploitation of cogeneration and renewable plants that are able to cover just a portion of the maximum load. Consequently, boilers have to be used, leading the system to a performance reduction and to an increase of primary energy consumption. Moreover, the peak makes the possibility of network extension quite difficult, because of the limitation on mass flow rates in the pipes. For this reason, a model is developed to make the thermal profile as flat as possible. The model is applied to a portion of the Turin district heating network, which is the largest network in Italy. Results show that reductions between 20% and 42% are possible, depending on the maximum changes in the possible schedules.