تجزیه و تحلیل حساسیت و پیامدهای اقدامات حفاظت از انرژی

Electricity use characteristics of 10 air-conditioned office buildings in subtropical Hong Kong were investigated. Monthly electricity consumption data were gathered and analysed. The annual electricity use per unit gross floor area ranged from 233 to 368 kWh/m2, with a mean of 292 kWh/m2. The ranges of percentage consumption for the four major electricity end-users – namely heating, ventilation and air-conditioning (HVAC), lighting, electrical equipment, and lifts and escalators – were 40.1–50.7%, 22.1–29%, 16.6–32.9% and 2.2–5.3%, respectively. Ten key design variables were identified in the parametric and sensitivity analysis using building energy simulation technique. Analysis of the resulting influence coefficients suggested that indoor design condition (from 22 to 25.5 °C), electric lighting (a modest 2 W/m2 reduction in the current lighting code) and chiller COP (from air- to water-cooled) could offer great electricity savings potential, in the order of 14%, 5.2% and 11%, respectively.

Buildings, energy and the environment are key issues facing the building professions worldwide, and energy is a key element in the overall efforts to achieve sustainable development [1] and [2]. In Hong Kong, there is a growing concern about energy consumption in buildings, especially non-domestic buildings, and its implications for the environment. In 2005, nearly two-thirds of the imported primary energy requirement (mainly coal and oil products, including natural gas) was used for electricity generation [3]. Electricity use in buildings is thus a key energy end-user. Earlier work on the energy consumption situation revealed that electricity consumption in non-domestic buildings, particularly fully air-conditioned office buildings continued to grow even during the economic downturn in the late 1990s [4]. Recently, the much publicised report by the Inter-governmental Panel on Climate Change (IPCC) [5] has helped generate a lot of interests in having a better understanding of the energy use characteristics of fully air-conditioned office buildings in Hong Kong, especially the likely impacts of changes in the building and building services designs would have on the thermal performance and energy use. This information is useful in any building energy efficiency programmes, whether it is related to the formulation of energy guidelines/codes for new building designs or the estimation of energy savings potential of energy conservation measures (ECMs) for retrofitting existing buildings [6] and [7]. There had been several studies on the energy performance of office buildings in subtropical Hong Kong. These were largely on energy simulations using generic building types [8], [9] and [10] or energy signatures involving energy audits and surveys of existing commercial buildings (office and shopping complexes) [11], [12], [13] and [14]. The primary aim of the present work is to investigate the sensitivity of energy performance of purpose-built fully air-conditioned office buildings in subtropical Hong Kong through parametric analysis of existing buildings. The purposes of the analysis are to assess the significance and impact of input design parameters, and to identify important characteristics of the input and output variables and the corresponding energy conservation measures.

Electricity consumption characteristics of 10 fully air-conditioned office buildings in subtropical Hong Kong were investigated. The consumption patterns showed distinct seasonal variations, indicating peak electrical demands during the hot, humid summer months from June to September, due to the corresponding cooling requirements. The annual electricity use per unit gross floor area (GFA) was found to range from 233 to 368 kWh/m2, with an average of 292 kWh/m2. The difference in electricity use per unit GFA was due mainly to the variations in lighting and equipment load density, the electricity use for vertical transportation (i.e., lifts and escalators) and building operating hours. Ranges of percentage consumption for the HVAC, lighting, electrical equipment and lifts and escalators were 40.1–50.7%, 22.1–29%, 16.6–32.9% and 2.2–5.3%, respectively. DOE-2 simulation was conducted. The measured monthly electricity consumption was used to calibrate the simulations by comparing with the computed values. All but one building met the ASHRAE error criteria (i.e., 5% or less mean bias error and 15% or less root mean square error). Sensitivity analysis was conducted for individual buildings. Examples of energy conservation measures – raising the indoor design condition, applying solar film to glazing units, lowering lighting load density and replacing air-cooled chillers with water-cooled – were analysed, and the estimated annual electricity savings due to these four ECMs were 34.1, 12.6, 60.1 and 34.1 kWh/m2, respectively. On a sector-wide basis, the mean influence coefficients from the sensitivity analysis revealed that a mandatory 25.5 °C indoor design condition, a modest 2 W/m2 reduction in the current lighting code and a territory-wide application of water-cooled air-conditioning systems could offer great electricity savings potential, in the order of 14%, 5.2% and 11%, respectively.