Potential benefits of implementing demand response into Vattenfall’s district cooling grid in Uppsala, Sweden

Abstract: Lately, there has been an increased cooling demand in Vattenfall’s district cooling (DC) network in Uppsala, Sweden. This especially occurs on warmer summer days, during so-called peak demand periods, where there is limited cooling capacity combined with limited distribution capacity in the network. This has led to Vattenfall wanting to investigate the potential benefits of implementingthe control mechanism demand response (DR), meaning that Vattenfall would have the possibility to regulate the outtake during peak periods. This needs to be tested first with a model, where the main objectives are to evaluate how customers could potentially get affected and how much DC energy can be shifted to non-peak periods. The term DR implies that there is a change in demand as a reaction to the status or available capacity in the energy network. Potential benefits from using DR could balance the grid but also increase the demand flexibility since the load can be moved in time to avoid peaks. This could take advantage of existing infrastructure and delay or make redundant possible investments in new distribution- or cooling production technologies. The result from the model will answer and evaluate four research questions: what time of the day is the peak period? Which are strong correlating variables/parameters to a high DC demand? How will the comfort of the customer get affected? and how much DC can be shifted.  The study method was creating a building model in the simulation program IDA Indoor Climate and Energy (ICE), where DR was tested through a self-built macro. The model was based on the customers in the DC network to make it correspond to a typical comfort cooling customer with mainly office and smaller share department store business. The model was simulated for four DRscenarios (DRSs) where the cooling systems were controlled during peak periods, where the supply was decreased, and during non-peak periods where it was instead increased. These scenarios were then compared to the results from a reference scenario (RefS) where no DR was applied. The simulation period was chosen to be a summer period where weather data from 2018 was used as a reference for warm summer days. The result calculations were based on simulations where data from a four-week period were used. The results showed that the time for peak demand period during warmer summer days was 12:00 –16:00 and two of the strongest correlating parameters to a high DC demand were the time of day and the outdoor temperature. When the set-point temperature for the room cooling units (RCUs) in the office areas was increased with 1°C for the DRSs, the thermal comfort was approximately the same compared to the comfort in the RefS. However, an increase of 2°C in the DRSs did have a negative impact on thermal comfort. When the set-point for the RCUs was increased with 1°C, the largest hourly DC power difference was 25% less cooling power in the DRS than in RefS. However, an increase of 2°C gave the largest hourly DC power difference of 43% compared to the RefS. The conclusion of the results showed that there could be potential benefits from applying DR both for the (office comfort) customers and Vattenfall. Recommendations for future investigationswould be to test it in real buildings, create a business model, and evaluate if customers are interested in this more sustainable demand solution.