Power Load Profile of International Commerce Centre (icc) and Potential Cost Saving Methods

Research paper

Power load profile of International Commerce Centre (ICC) and potential cost saving methods

1. Abstract

Hong Kong is an Asian city with a subtropical climate. For every year, commercial business deplete approximately 60% [1] of the total electrical supply in Hong Kong. Due to the humidity and hot weather, the energy consumption of building are contingent on cooling load demand of HVAC system which is nearly 40% [1]of total commercial energy end-uses .In regard to the Hong Kong land policy, developers are willing to construct high rise buildings to provide more room for occupancy and to attain the benefit . As a result, there is a trend of building super-high buildings. In addition, the International Commerce Center is one of the examples which is also super high and the highest construction in Hong Kong. This paper, it provides review of energy consumption and the power load profile of ICC in 2011 , 2012 and 2013. In order to determine the potential cost saving and payback period, various energy saving methods will be listed individually.

2.Introduction

The population of Hong Kong has risen since it became a colony of the British Empire .In last decade, the population has been increased to 7,100,000 from 2001. This great increase in population results in higher land demand for residential and commercial use. Due to the land policy and over-population, the developers tend to construct high-rise buildings which can provide more room for occupant’s activities and increase the profit margin.

According to EMSD [1], HVAC, lighting, water supply system and office equipment are the major components (in either residential or commercial buildings) that require high energy consumption. Hong Kong is located in typical subtropical zone and the weather is hot and humid in spring and summer .During the humid and hot months, the cooling load demand of commercial building increases rapidly for space conditioning and removal of thermal storage effect. With the improvement in living standard , the electricity consumption per capita has been increased from 5446(GJ) to 5966 GJ in 10 years [3] . Based on the data, it could be predicted that the energy consumption in Hong Kong will continuously rise with the upsurge of population.

2.1 Description of International Commerce Centre

International Commerce Centre (ICC) is the highest commercial building, and one of the super-high rise buildings in Hong Kong. It was awarded with grade A by the Hong Kong Government’s Rating and Valuation Department . The building rises 480 metres above the ground and contains 118-storeys with total gross floor area of approximately 450,000 square metres which can accommodate more than twenty thousand people during office hours .[4]

For the space conditioning system, the operation system adopted by engineers is determined by its grading. For the International Commerce Centre, it is divided into 2 zones which are the arcade and the office tower . The space cooling of arcade is provided by a constant air volume system (CAV) with Air Handling Units (AHU). By considering the local control of each air conditioning zone and potential of energy saving , Variable Air Volume (VAV) system is chosen. The cooling load demand of office tower is served by numerous VAV boxes and two Air handling Units (AHU) on each floor. Primary Air Handling Units are installed to perform pre-cooling and better air treatment for AHUs.

For the chiller system, the selection of components is mainly determined by coefficient of performance (COP) of chillers, operating cost and cost of installation. The advantage of using water cooled chillers are high energy coefficient of heat rejection process. Thus, the total cooling load of ICC is supported by 7 set of 2040 tons water cooled chillers. With the trend of constructing super high-rise building , buildings with large number of storeys will be constructed in order to solve the consequence of over population. By considering the carbon emission rate and electricity consumption, It is necessary to study the characteristics of the power load profile of Hong Kong’s super high rise buildings and perform situation analysis to understand the condition of energy intake.

3. Literature Review

3.1 Energy use in commercial buildings in Hong Kong

The amount of energy consumption in a building depends on several factors. Lam, Chan & Tsang (2003)[5] state that the design of a building envelope, the operating efficiency of the HVAC system , ventilation load for providing fine indoor air quality, numbers, types of lamps and theirs efficacy , office equipment , operation and maintenance.  Lam JC, Chan ALS [6] indicates that it is necessary to identify the major services or end-users of energy. It has also mentioned there are four major consumer of energy which are heating, ventilation and air conditioning (HVAC) , lighting , electrical equipment and vertical transportation system in the building . A recent energy audit conducted by EMSD (2013) has listed that the annual energy consumption for space conditioning in office building is 6711 TJ (53.76%). Meanwhile, the lighting and office equipment are 1784 TJ (14.4%) and 1577 (12.63%) respectively.
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Table 1. Energy use in commercial (office ) building in Hong Kong[1]
3.1.2 HVAC
Lam (2000) [8] describes that the major components of HVAC system could be divided into 2 groups, which are the air side and the water system. The chiller plant in the water side system could consume more than 40% of the total annual electricity expenditure .Additionally, the pumps and fans takes 10% of the total annual electricity supply. As a result air-conditioning accounts for nearly 50% of the total annual electricity use. Therefore, it is important to study the performance and control system plant in order to improve system efficiency and reduce energy demand.

4.Objectives

As the population growth affects the limitation of natural resources, the developers are willing to build super-high rise building to solve the land demand. Furthermore, this kind of project could improve their reputation and have the potential of being granted landmark status which may help the company earn more from future projects. However, the energy consumption of super-high rise building is not well-known. Building services engineers may need to focus their efforts on system selection in order to reduce the total energy consumption. As facility management team might not have relevant experience in managing super high rise building, they may have difficulty optimizing the system performance and studying the operation cost .Thus, the objective of this study is to understand and analyze the power load profile of super high rise building and its characteristics which may provide more information to engineers for design consideration.