Optimization of district coolingsystems : A case study in a Swedish industrial setting

Abstract: Energy utilization as well as heating and cooling specifically constitutes a large share of the energy consumption in the EU. Reducing greenhouse gas emissions in this sector is thereby of importance to mitigate climate change and fulfill the criteria stated by the Paris Agreement of limiting the increasing global mean temperature to 1.5 °C. There are multiple ways in which cooling demand might be satisfied, including district cooling where the cold from a certain resource is distributed to the user through a network of pipes. This project considers the optimization of district cooling systems in industrial settings through a case study at Scania’s facilities in Södertälje which is located south of Stockholm, Sweden. Scania is a part of the manufacturing industry, producing trucks and busses. The factory uses a district cooling system with designed temperatures of 11 and 18 °C for the inlet and outlet respectively. However, the designed values are currently unable to be met. The share of cooling demand of three main end users in the factory, electrical cabinets, washing machines and processing machines, was considered. Furthermore, the temperature that each machine type theoretically could be supplied with was examined, showing that a higher supply temperature than 11 °C would still fulfill machine requirements for certain components. It was concluded that processing machines would be the most suitable for the implementation of improvement measures, such as increasing supply temperatures, considering the amount of cooling demand as well as required supply temperatures. Moreover, a MATLAB model to assess available cooling capacity for multiple streams at different temperature levels was developed and applied to the case study. End user components at Scania was divided into four streams depending on inlet and outlet temperatures required, showing that cooling demand for streams at higher temperature levels could be either partially or completely satisfied through the reuse of cold from lower temperature levels. This could be done by using the return from streams at lower temperature levels as inlet for streams at higher temperature levels.