B074 Office IEQ & Energy

A modeling study of energy consumption and occupant acceptance of environmental policies for air-conditioned offices in Hong Kong

Brief:

Air-conditioned office buildings in cities in the developed countries are one of the biggest consumers of electricity, especially those in the subtropical climate regions. A good indoor environmental policy should respond to energy conservation as well as indoor comfort. With the help of indoor environmental quality (IEQ) acceptance model for air-conditioned offices, this study investigates the energy consumption implications that correspond with occupant thermal comfort for two indoor environmental policies, namely, (A) with air temperature=20- 25.5°C, RH=40-70%, air speed=0.2ms⁻¹; and (B) with air temperature=25.5°C, RH=70%, air speed=0.3ms⁻¹. The thermal energy consumption factors including heat gains through building fabric, outdoor air for ventilation, heat generated by the occupants and equipment in the space are evaluated. The Predicted Mean Vote (PMV) and the probable clothing behavior form the basis for the determination of the occupant thermal acceptance.

This study also presents useful information on office energy performance evaluation. Comparing the result of the two indoor environmental policies with the existing profiles of Hong Kong office building energy consumption (i.e. ‘no policy’ cases) shows that the expected annual thermal energy saving can reach 2% when applying (A) or 9% when applying (B). Taking −0.5≤PMV≤0.5 as the acceptable threshold of thermal comfort, the 95% satisfied occupants in the ‘no policy’ cases (average clothing value=0.73clo) drops to 94% (0.59clo) under (A) and 59% (0.35clo) under (B). If a hypothetical minimum clothing value of 0.3clo is imposed on the Monte Carlo simulations for (B), 6% occupants (PMV≥2.5) will feel ‘hot’, 14% (2.5<PMV≤1.5) ‘warm’ and 21% (1.5<PMV≤0.5) ‘slightly warm’.

Further Information:

Wong LT, Mui KW, 2009. A modeling study of energy consumption and occupant acceptance of environmental policies for air-conditioned offices in Hong Kong, The First International Conference on Applied Energy (ICAE09), 5-7 January, Hong Kong University, pp. 833-842.