Night cooling optimization using post processed control systems data

Abstract

Carbon emission reduction and energy efficiency are highly important goals for the built environment, and society as a whole. One way that the building sector works with improving energy efficiency is advanced control of, among other things, airflow, heating, cooling and solar shading. When these control systems are installed there is often a possibility to gather historical data, and this study examines the possibility to use that data in combination with a building energy simulation to analyse the systems control and find potential improvements. Night cooling, to decrease the cooling need in buildings by over-ventilating at night with cool outdoor air, was used as an example of a systems control function to be evaluated and potentially improved. A case study was carried out, where the night cooling function in an office building located in Göteborg was examined. As a first step a building energy simulation was done using post processed control systems data as input, and the simulation was calibrated to come as close as possible to the measured behaviour of the building. As a second step different alterations to the night cooling control were evaluated using the calibrated model. The alterations were evaluated by comparing three different indicators for energy efficiency; bought energy, electricity cost and specific energy use according to Swedish building regulations. This was done to investigate if prioritizing different indicators would lead to different optimal night cooling strategies. The study suggests that the building performance for all indicators can be improved, even though the studied building is new and built with a high aim when it comes to control and energy efficiency. Proposed alterations are to make sure that the active cooling is completely disabled during night cooling, and to limit the airflow to avoid the peak when the night cooling initiates. There are some differences between the results of the different indicators, but for this studied building the difference is not large enough to lead to different night cooling strategies.