Evaluation of energy efficiency of air side air conditioning systems

Pao Yue-kong Library Electronic Theses Database

Evaluation of energy efficiency of air side air conditioning systems

 

Author: Hung, Cheung-hung
Title: Evaluation of energy efficiency of air side air conditioning systems
Degree: M.Sc.
Year: 2000
Subject: Commercial buildings -- Air conditioning -- China -- Hong Kong
Commercial buildings -- Energy consumption -- China -- Hong Kong
Air conditioning -- Efficiency -- China -- Hong Kong
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Building Services Engineering
Pages: xi, 104 leaves : ill. ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1516271
URI: http://theses.lib.polyu.edu.hk/handle/200/4737
Abstract: Central air conditioning systems are widely used in commercial and industrial buildings in Hong Kong. Air side air conditioning systems commonly used in office and commercial buildings include, fan coil systems, constant air volume systems and variable air volume (VAV) systems. The dual conduit VAV system is an extension of the basic VAV system and another version of the VAV air conditioning system is the dual duct system. Energy statistics [Census and Statistic Department. 1996] showed that about 57% of the electricity generated within and imported into Hong Kong each year was consumed in commercial buildings. The annual energy consumption of central air conditioning systems may account for up to 70% of the annual operating cost throughout the life cycle of such buildings. Therefore, even a relatively small saving in the energy use of the larger energy consumers can translate into significant reduction in the operating cost. Efforts have been made to comment on the ASHRAE Standards 90.1a: 1989 [CIBSE, 1996; ASHRAE, 1993] and the Code of Practice [EMSD, 1998] on design of air conditioning installations, with emphasis put on the requirements on the air side systems, and to comment on the effectiveness of such control on ensuring high energy efficiency. The Code of Practice is aiming at setting the maximum allowable energy consumption in commercial buildings for air conditioning and suggests to maintain a reasonable consumption in various types of air-conditioned areas. The advantages and the shortcomings of the implementation of the Code of Practice have been studied and the observations are described in this dissertation. Furthermore, a comparison of the Code with the ASHRAE Standard, Standard Government General Specification and common practice in the private sector is included. Comments on the requirements as specified in the Code of Practice on energy efficiency are also given. It is noted that majority of the air conditioning equipment currently available from suppliers / manufacturers can satisfy the Code's requirement. However, the dual conduit system may be banned when the Code of Practice on energy efficiency is enforced. Therefore, the capital cost, energy consumption and space requirement of this system have been studied in detail and compared with other system designs to justify this requirement. The simulation software: HTB2 and BECON, were used for simulating heat transfer in buildings and predicting electricity consumption for air conditioning in the case studies. The case studies were aimed to compare the energy consumption of different types of air side systems. The limitation, the restriction and constraints for the computer simulation have been studied. The life cycle cost of different types of air-side systems in buildings of different sizes have been studied based on predictions obtained using these programs. From the computer simulation, the energy consumption of the VAV system is found to be the lowest and the FCU system is the second lowest, whilst the dual conduit system has the highest energy consumption due to the additional AHU involved. The study embraced small, medium and large buildings. The life cycle cost of VAV system is also the lowest and FCU system is the second lowest while dual conduit system is the highest for a range of buildings including small, medium office buildings. Therefore, it is considered reasonable for the Code of Practice to prohibit the use of dual conduit systems.

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