Deviation of design air-conditioning load based on weather database of reference weather year and actual weather year

Abstract

Abstract In Japan, in order to determine the capacity of air-conditioning equipment, designers usually use the weather database of Reference Weather Year (RWY) to obtain the design air-conditioning load by using software such as New HASP/ACLD and Building Energy Simulation Tool (BEST) that are often used in Japan. In recent years, with the global warming due to climate change, the weather database used to calculate air conditioning load also changes. Thus, in order to determine an appropriate capacity of air-conditioning equipment for energy conservation of buildings, the deviation of design air-conditioning load calculated using the weather database of RWY and Actual Weather Year (AWY) should be discussed. In this paper, New HASP/ACLD was used to calculate the building heat loads of eight major Japanese cities over 30 years (1981–2010) between RWY and AWY. The heat load at an exceedance probability of 2.5% is defined as the design air-conditioning load in this paper. Comparing the design air-conditioning load obtained from RWY and AWY, it is shown that it is not necessarily the most appropriate when using the RWY to calculate the design air-conditioning load, especially for heating load in winter. Additionally, it is also shown that the annual heating load time ratio has decreased and the annual cooling load time ratio has increased over the 30 years.