En flödesutjämnande driftstrategi för Uppsalas fjärrvärmesystem : En ändrad styrning av framtemperaturen

Sammanfattning: This thesis examines a possible control strategy to minimize flow fluctuations in Uppsala’s district heating system. High variations in flow rate may lead to complications caused by hydraulic constraints in the district heating system. These complications, such as inadequate pressure and temperature levels, increase the risk of heat delivery failures. It is therefore important to avoid such situations both for the producer and for the customers. Typically, the forward temperature is controlled by using a rough correlation with respect to the outdoor temperature. This thesis examines a control strategy for the forward temperature that is not only based on present outdoor temperature, but also on time of the day. By controlling the forward temperature in this more sophisticated manner, flow fluctuations can be reduced. The new control strategy was created by studying collected operational data. Certain patterns in heat demand could then be revealed, leading to the construction of a software tool that simplifies compliance with the new control strategy. Potential benefits from a possible implementation of the new control strategy were then examined. The results show that there are reasons for implementing the strategy. As the flow fluctuations according to the simulations were reduced, the new control strategy therefore imposes a number of advantages. Beside the economical benefits, an increased net capacity is one crucial improvement. Another essential benefit is the expected improvement in heat delivery reliability leading to more satisfied customers.