Novel effective room temperature-based predictive feedback control method for large-scale district heating substation

Abstract

• A predictive feedback control strategy based on effective room temperature is proposed. • The feasibility of the method is verified using an existing district heating substation. • The proposed method is flexible and performs well in terms of anti-interference. • The proposed method can reduce thermal energy consumption by 6.1%. Conventional district heating (DH) substations in China use a feed-forward adjustment method that predicts the water supply temperature based on the outdoor temperature. This method does not consider the delay of the pipe network and the thermal inertia of the building. Most importantly, the lack of closed-loop feedback on the indoor temperature results in high energy consumption and large fluctuations in room temperature. In this study, a predictive feedback system based on effective temperature control has been proposed to improve the quality of district heating. First, a dynamic simulation control model of a DH substation was created based on measured data. Then, through dynamic simulation analysis, the influence of the heating network delay on the room temperature was observed to be smaller than the influence of the building's thermal inertia, which confirmed that predictive feedback control based on effective temperature could be achieved. Finally, the new control method was compared to two conventional control methods. Based on the comparison with the two conventional controls, refining the timespan of the feed-forward control was found to be ineffective for improving room temperature stability owing to thermal inertia. The new control method demonstrated high control flexibility and strong anti-interference, and the indoor temperature fluctuation decreased from ±1.1 °C to ±0.3 °C compared with conventional control methods. In this case, under the premise that thermal comfort is not affected, the room temperature setting can be reduced by 0.5 °C, resulting in an energy saving of 6.1%, with a payback return period of less than a year. This method only requires installing room temperature sensing equipment and linking the feedback control algorithm to the original control system and is therefore easy to achieve.