Heat recovery from district cooling

Sammanfattning: District cooling is increasing in the society and in many areas two separate infrastructural systems are used for heating and cooling. It’s an expensive and inefficient solution, by utilizing the heat in the return pipe of a district cooling system, one system could be used to supply customers with both heat and cold. By conducting a case study, this master thesis intends to investigate the potential system utilities with connecting heat clients to the district cooling return pipe through heat pumps. Based on customer data from an area with both district heating and cooling systems, simulations are made in MATLAB in order to answer how factors such as electricity consumption, cold and heat production will change when two large heat clients are connected to the district cooling system instead of the district heating system. These factors are dependent on the Seasonal Performance Factor of the heat pump, wherein a few different values are studied. The results show that both customers could be connected and that the cold production in the heat pumps could replace the central production plant for roughly 140 days of the year. At the same time the produced heat will have an efficiency that’s higher than the efficiency of the heat pump itself. The reason for this being the amount of saved electricity in the central production plant. A cost comparison was conducted between heat pumps and conventional district heating and showed that conventional district heating is much more expensive in the investigated area, mainly due to the high costs of building the infrastructure. Overall, the study has indicated that there are many advantages and that a combined district heating and cooling system would be efficient in the investigated area and other areas whit similar heat and cold demand. It could be efficient in areas with different heat and cold demand as well, the important factor being that the heat demand isn’t much higher than the cold demand during too long periods over the year.