Mitigation of district cooling peakloads in commercial buildings

Abstract: The district cooling network is designed, dimensioned and operated based on the largest power demands. If each district cooling consumer would lower their peak load, the system could serve a greater clientele. This would be beneficial both from an environmental and economic perspective as the system ought not to expand as extensively. This is most crucial at the time being as the need for cooling in commercial buildings is increasing. Furthermore, the price of district cooling is based on each user’s peak power demands each year in the pricing models studied. Some more and some less successful examples of mitigating district peak load exists. The aim of this study was to analyze the use of district cooling is Vasakronan’s facilities in Stockholm, focusing on peak loads. Not only operational causes were to be covered but also natural causes such as the outdoor temperature. The question to be answered was “How can the use of district cooling in Vasakronan’s facilities be adapted in order to sustainably reduce the peak loads?”. A model was developed in Microsoft Excel for analyzing the causality between ambient parameters and district cooling peak loads. Based on the causes of district cooling peak loads, the facilities were categorized and reducing measures has been proposed, modelled and analyzed. An economic analysis for the recommended measures, including both the potentially lower cost from reducing the peak loads and the cost of installing or using a new product or service was conducted. It was concluded that a reduction of the charged peak load of 28% could be reached if increasing DT to 10°C and installing power monitors in all facilities concerned. These peak load mitigating measures are relatively simple, can be applied to the existing operating and cooling system and does not come with high investment costs. The annual cost reduction of these measures reach 12%, corresponds to 3,3 million SEK. This corresponds to a facility value increase of 65 million SEK. Thus, the recommended peak load mitigating measures was the proposed DT-increasing measures and installing a power monitor. To reduce the district cooling peak load further, four peak load mitigating measures was studied: cooling machines, night cooling, water and PCM TES. Cooling machines, water and PCM TES showed a potential to reduce the peak load level more than night cooling. However, night cooling can be applied to the existing operating system, and does not require space-requiring installations or high investments. Thus, night cooling -3- was recommended as a measure if wanting to reduce the peak load level further. However, one should be careful when implementing night cooling as it can cause an uncomfortable indoor environment.