Abstract
Several previous studies have investigated active night cooling strategies to reduce the peak cooling load in buildings, primarily by precooling the building by the ventilation air during the night. In this study, active night cooling is supplied by the use of district cooling, mainly for cooling buildings by hydronic cooling systems, such as chilled beam or fan coil systems, but potentially also to cool the ventilation air if the outdoor air temperature is above the supply air temperature setpoint. A field test with active night cooling by district cooling was conducted during the summer of 2020 in three commercial buildings located in Gothenburg, Sweden. The active night cooling strategy was implemented by changing the time schedule operation of the buildings’ chilled beam systems to twenty-four hours per day for the first half of the summer and changing back to regular time schedules for the second half. The results showed that active night cooling failed to reduce the hourly maximum cooling power. However, the peak cooling load, corresponding to the 100 hours with the highest cooling power, was reduced with 6.5% for one of the buildings. Active night cooling also reduced the daytime energy usage between 0.7 and 4.6%. The field test demonstrated that some buildings and associated cooling systems are more compatible for active night cooling than others. The test also showed it was possible to achieve some cooling power and energy reductions with simple measures. However, providing active night cooling supplied by district cooling will cause additional costs for the building owners unless it is incentivized by the district cooling provider.
Highlights
The global energy use to supply buildings with space cooling is expected to increase threefold by the year 2050 compared to 2016 [1]
Despite several field tests conducted on active night cooling in commercial buildings, there are no prior field tests on active night cooling in commercial buildings with hydronic cooling systems supplied by district cooling
The aim of this study is to conduct a field test with active night cooling in three commercial buildings equipped with hydronic cooling systems supplied by district cooling
Summary
The global energy use to supply buildings with space cooling is expected to increase threefold by the year 2050 compared to 2016 [1] To avoid such a drastic increase, district cooling (DC) is a less primary energy intensive alternative compared to building individual airconditioners and chillers. Despite benefits with aggregated cooling demands on a city level, the district cooling provider has to maintain a sufficient amount of installed cooling capacity to supply the buildings during peak cooling load conditions. This often accompanies large investment and maintenance costs for peak load chillers that only need to operate for short periods each year [3]. One measure to reduce the number of peak chiller units is to incorporate a central thermal energy storage, such as a chilled water tank, charged during the night and discharged during the day [4], [5]
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