Full-scale measurement and validated simulation of cooling load reduction due to nighttime natural ventilation of a large atrium
da Graça GC
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In buildings with exposed internal thermal mass, natural ventilation (NV) can be used for nighttime pre-cooling (NVC) of the building for the next day. In many cases, these natural cooling systems are used in combination with conventional mechanical cooling systems (an approach known as hybrid cooling). The use of these systems is still limited, in part as a result of the lack of field studies that measure actual cooling load reduction that can be obtained when using an NVC system. This paper presents the first measured energy savings due to NVC in a non-residential building. This study had two objectives: measure daytime cooling load reduction due to NVC in the previous night; and validate thermal and airflow simulation tools that are used in design of NV and NVC systems. The results are encouraging: comparison of the cooling demand of similar days with and without NVC in the previous night shows that, on average, the NVC system reduces the daytime cooling load by 27%. The dynamic thermal simulations were able to predict the cooling load reduction, internal air temperature and bulk airflow rates with average errors of 1.7%, 11.2% and 14.1%, respectively.