Specialist Research Areas & Projects
Researchers : Dr H X Yang (leader), Dr K T Chan, Dr S M Deng, Prof Francis W H Yik
Collaborators : Dr Y Q Ni, Civil and Structural Engineering Department, HKPolyU
Research Fellow : Prof S J You
Research Students : Miss L Lu, Mr G Gang, Mr Y Y Fung, Mr K Tsang
Research Assistant : Mr D An, Mr C Lou, Dr C Ren, Dr Z Zhu
The research and consultancy activities in the Renewable Energy Research Group (RERG) include research and consultancy in building-integrated photovoltaic applications (BIPV), wind power generation, hybrid solar-wind power, solar thermal application, solar cooling technology and building energy conservation. We have a team of renewable energy R&D specialists in system simulation, system design, development of control devices and data collection/analysis. We have completed a number of high-profile research projects and consultancy projects in Hong Kong, Macao and Guangdong. Funded by the Industrial Support Fund, the first BIPV project in Hong Kong was set up in 1999 on the campus of The Hong Kong Polytechnic University. We have done a number of experiments for different PV systems. The project has attracted a lot of visitors from different sectors. Since then, a number of BIPV projects have been developed in Hong Kong. Besides, we developed the first solar street lighting project in 2000 and the first commercial grid-connected PV-Roof project in 2002 for Kadoorie Farm and Botanic Garden. So far, we have completed more than 5 research projects for the Research Grant Council, the University and other organizations, and 8 consultancy projects for local industry. We have set up the unique 2¡Ñ2m Solar Simulator Lab in the University. We anticipate more collaborations with local industry, the industry in Chinese mainland and overseas counterpart in the future.
Photovoltaic integration in buildings for electricity generation in Hong Kong
(HK$1,710,000, Innovative Technology Scheme)
This project was formerly started on 1st August 1997 and ended on 31 April 2000. All the work defined in the original proposal has been completed. Some work is even out of the scale of work proposed. The successful demonstration of the project has attracted a lot of people from various areas including Government officials, businessmen, industrialist, environmentalists, researchers and students. Research results from the simulation/experimental work are being and will be used by local industry for building-integrated photovoltaic applications for solar energy power generation in Hong Kong.
The main deliverables include the demonstration/experimental BIPV project and computer simulation and experimental monitoring results in terms of technical, operational, environmental and economical issues. The permitting/legal and potentiality issues have also been investigated. An experimental test has been done on grid-connected photovoltaic system. The performance data of the BIPV systems will be used as design guidelines for new BIPV developments.
The project benefit the local industry for developing related industrial products. In fact, a number of local manufacture companies are developing such products, e.g. PV curtain wall, PV-roof cladding, PV system controllers and remote PV systems. They are very interested in R&D collaboration and investing in solar energy research and developemnt. A number of PV projects are now being developed or initiated in Hong Kong due to the work in this project. Solar energy for electricity generation is now a big business in the world and a new business in Hong Kong. This is a very sucessful project with good results.
Energy performance evaluation of advanced-window frame systems
(HK$457,817, Research Grants Council)
The goal of this work is to investigate the influence of advanced-window frames on window's
energy performance and to develop the energy efficiency criteria for selecting
windows for the climates in Hong Kong and Mainland
For cooling-dominated climate in Hong Kong and Southern China, and heating-dominated climate in Northern China, U-value and solar radiation transmission through windows play important roles in heating and cooling energy consumption. How to select approximate windows for buildings remains a problem. As a result, no guidelines for local architects and building services engineers to choose appropriate windows for different types of buildings for energy conservation. This project intends to evaluate the existing window rating methods in developed countries for proposing a rating system based on the theoretical and experimental investigations for window frame systems. The results can be used for developing a design guideline for local engineers and built industry. The research will also benefit the local manufacturing industry for development of advanced window systems.
Study on hybrid solar-wind power generation for renewable energy applications in Hong Kong
(HK$170,000, The Hong Kong Polytechnic University)
In recent years, renewable energy applications in Hong Kong and the adjacent areas have developed rapidly. A number of high-profile solar energy projects have been or are being completed in Hong Kong. It is found that solar energy and wind energy for power generation are regarded as the most viable renewable energy sources. The combination of these two renewable energy systems, i.e. hybrid solar-wind systems, can provide reliable and continuous power supply in an area. This project aims to investigate the hybrid solar-wind energy system technology and its application for the Hong Kong weather and economic conditions. A simulation model for analyzing the probability and reliability of hybrid photovoltaic-wind power generation systems will be developed. An analysis of the complementary characteristics between solar irradiance and wind power will be made. An optimization procedure and design guideline of a hybrid photovoltaic wind energy system will be proposed for local engineers and energy industry. A small-size hybrid solar-wind energy system will be set up for simulation validation and demonstration purposes. Based on the outputs from the simulation and experiments, the potential and feasibility of the hybrid solar-wind technology application in Hong Kong will be assessed and predicted. An overall assessment of the value of the technology will be made for its application in Hong Kong. The technical, economic and management issues related to the application of this new technology in Hong Kong will aslo be investigated. The successful realization of the project will contribute to the Government's targets for a clean environment and high-tech industry in Hong Kong.
Development of an innovative building-integrated photovoltaic cladding technology
(HK$500,000, The Hong Kong Polytechnic University)
Application of photovoltaics in buildings (or building-integrated photovoltaics, BIPV) develops rapidly in Hong Kong and the world in recent years, but the cost is till high compared with traditional fossil fuel power generation. How to reduce the cost is always the priority. This project is proposed to investigate an innovative cladding techniquc, i.e. the direct-integrated photovoltaic technology (DIPV) for combing photovoltaic modules with building cladding so that the total cost is reduced and the aplication of BIPV could be made feasible. The thermal and structural perforamnce of the new BIPV cladding systems will be investigated by the solar energy research expertise in the BSE Department and the strucural engineering expertise in the Civil and Structural Department. The main objectives are as follows:
¡P To investigate the electrical and thermal effects of the DIPV roof elements on building¡¦s energy and environmental performance;
¡P To study the optimum design of the DIPV technology through numerical simulation;
¡P To simulate and test the structural strength of the developed DIPV systems to prevent damage from typhoons and to improve their structural design. A wind tunnel test and other structure lab tests will be needed;
¡P To develop an optimization procedure and guideline for using this technology;
¡P To assess the potential of this renewable energy technology application in Hong Kong;
¡P To demonstrate this technology for local industry by setting up an experimental system;
¡P To develop an innovative product or more products of this innovative technology for commercialisation.
Energy performance test of the indirect evaporative heat exchanger at Kowloon Park
(HK$50,000, The Four Gay Engineering Company)
This project was completed in March 2003. The following conclusions can be drawn from the study:
¡P This indirective evaporative heat exchanger or indirective evaporative cooling system (IECS) is suitable for Hong Kong¡¦s weather conditions with hot and humid climate. The latend enegy recovery due to evporation of condensate water is significant for the total energy recovery;
¡P The energy performance of the IECS is very good, especially for peak cooling load reduction. The IECS is highly reccommended for application in new central air-conditioning systems with new chiller plants or exiting air-conditioning systems with renovated chiller plant for reducing the initial investment of the new chillers;
¡P If the IECS is added to an existing A/C system without changing its chiller, the payback period ranges from 3-6 years depending on the actual equipment¡¦s initial cost. However, the payback period could be droped to about 2-4 years if a larger module is used (this tested module is a very small module of the module series provided by Four Gay Engineering Co. Ltd.);
¡P The operation and maintenance of the system is easy and reliable;
¡P Environmental factors have not been taken into account in the above economical analysis. If environmental benefits are considered, the payback period will be shorter. In fact, the energy conservation technology also reduces fossil fuel consumption so that environment is protected. Pollution from burning fossil fuels has caused a lot of serious environmental problems, e.g. particle emission and global warming gas generation.
This project is continued with more detailed theoretical investigation in simulation and simulation validation funded by the Department (HK$280,000)
Numerical investigation of natural convection in inclined channels
(HK$170,000, The Hong Kong Polytechnic University)
Natural convection of air in inclined channels including horizontal and vertical channels are widely available in various solar energy applications, such as solar collectors, double glazed semi-transparent PV wondows, ventilated PV roofs and PV walls, and TIM-walls. The heat and mass transfer, and the naturnal convection issues have been investigated by the research group. The numerical study of heat transfer in a ventilated photovoltaic (PV) panel is carried out for its effect on the energy performance of PV modules and cooling load of buildings. The buoyancy induced thermal fluid instability between two parallel horizontal plates has been investigated numerically by solving the governing equations of the base and perturbation fields using a fractional algorithm. The super-critical secondary flow properties of natural convection in an inclined channel (NCIC) have been explored numerically by virtue of Boussinesq type Navier- Stokes equations. The simulation results have been used in the development of optimized solar energy systems in which the concept of natural ventilation is incorporated.
Solar street lighting and solar garden lighting
(HK$200,000, British Council and Kadoorie Farm)
Remote solar lighting represents one of the major uses of solar energy applications for power generation. The detailed simulation model and advanced solar lighting controllers are developed by this project jointly funded by British Council and Kadoorie Farm. The optimum sizing problem has been solved through the simulation. Different adjustment methods have been investigated for improving the energy performance of solar lighting systems. The deliverables have been used in the solar street lighting and garden lighting systems along the main street in Kadoorie Farm, the first street lighted by solar energy resource in Hong Kong. Collaboration with local industry is now going well to develop more advanced solar lighting and garden lighting systems.
The solar street lighting and garden lighting systems in Kadoorie Farm
Researchers : Dr S K Tang (leader), Dr C M Mak, Dr Daniel W T Chan
Collaborators : Prof J Tian, Institute of Acoustics, Chinese Academy of Sciences, P.R.China
Dr N Peake, DAMTP, Cambridge
Yang, Division of Information Engineering, School of Electrical & Electronic
Engineering, Nanyang Technological University,
Research Students : Mr Elvis C K Lau, Mr Eddie S K Lau, Mr Stephen C H Ng,
Mr B R Vijaya Raghava Raju
Research Assistant : Mr Louis W L Chan
This research team focuses on advancing technology in enhancing the acoustic and vibration control in the built environment. Topics concerned include the application of active noise control, development of assessment methodology, noise prediction and control in flow ducts, air-borne and structure-borne sound transmission within residential estates and within buildings, acoustical environment performance, mobility studies, speech intelligibility in schools, architectural acoustics and signal diagnostics.
Efforts have also been made on the development of commercial usable products. A low pressure loss broadband compact duct flow silencer is in the design stage. Also, research works concerning vibration transmission within buildings will lead to the development of a realistic statistical energy model for use in new building design. In addition, it is planned to develop an active controller for transient noises.
The research team also gives advices to the industry in forms of brief communications and/or PolyU consultancy projects. The topics / issues cover nearly all branches of applied acoustics and are not restricted to those described above.
Research Projects :
Active control of sound transmission through panel structures
(HK$474,000, Research Grants Council)
Sound transmission through doors, windows or other panel structures has long been a problem in building services noise control. Daily life examples of it include the transmission of traffic and aircraft noise into living and sleeping rooms and the noise that goes into offices from air conditioning plant. While the high frequency component of the noise can be attenuated by materials like carpet, fibre glass and furniture, the low frequency component remains hard to attenuate due to the nature of the mentioned materials. It has been shown by other researchers that sound can be cancelled by another sound with the right phase and amplitude in an air duct. The cancellation sound characteristics are changed by a specially designed controller to adapt to the change in sound field. This method, which is known as active noise control, is proved to be very efficient in attenuating low frequency noise. In the present project, this idea is extended to three dimensional space. To be more related to daily life, the transmission of low frequency noise through plate structures (to simulate windows or doors) into an enclosure (and thus, a living or sleeping room) is studied and its active control investigated both experimentally and theoretically. It is hoped that an appropriate control system can be derived.
Establishment of noise level distributions and development of a noise criterion in building services engineering
(HK$239,980, The Hong Kong Polytechnic University)
The distributions of noise levels in the community, may it come from transportation or mechanical services, usually determines the setting up / selection of noise criteria and the noise mitigation methods to be employed. An understanding of them will result in a simpler noise measurement procedure and specification for acoustical environment. In addition, such understanding enables prediction of acoustical parameters without measurements. There has been research elsewhere studying the statistical distribution of traffic noise level. A recent investigation by the author has shown that the noise level inside office buildings has a particular probability density distribution.
The present study is an attempt to find out the distributions of community noise levels, which are mostly unknown to the knowledge of the author, and to the setting up of a suitable / unified noise criterion for general use as this topic remains controversial, despite the continuous effort of active researchers.
An investigation on the self-noise generation of the dissipative silencer and its control
(HK$985,817, Research Grants Council)
This research proposal deals with a flow-induced noise problem that occurs in the conventional silencers in the air conditioning systems of modern buildings. Both theoretical and experimental investigations on its generation mechanisms and control method are included. In a modern building, the air conditioning system provides thermal comfort control in its interior but it also generates noise. This noise can propagate to the building interior through the ductworks and can go to the surrounding of the building causing nuisance to its own users and its neighbours. Dissipative silencers are commonly used to attenuate this kind of noise. This kind of dissipative silencer attenuates noise by the viscous actions in the porous material lining (usually made of fibreglass) inside the silencer. Effective range of noise control is limited to the middle to high frequency. Splitters made of porous materials are included in the silencers to increase their sound attenuation capacity. However, the restriction on the turbulent flow due to the silencer installation and the splitters create flow instability problem, introducing additional vorticity into the flow which interacts with the solid boundaries no matter they are rigid or porous and eventually produces noise. The vorticity within the original turbulent flow will also radiate sound as its motions are restricted by the configuration of the silencer. Though the level of this self-noise may not be high enough to override the overall noise attenuation provided by the porous materials, this self-noise does reduce the performance of the silencer. However, if it is of low frequency, there will be a risk of low frequency noise amplification by the silencer. The results of the present proposed research can provide a reliable physical model for the generation mechanism of this self-noise and thus its prediction. With a clearer understanding on its generation mechanism, a control method can be derived and tested in the laboratory.
Generalization of noise level distribution theory for improved noise assessment, prediction and control in the built environment
(HK$718,404, Research Grants Council)
Noise pollution has become an important issue in every metropolis. The sources of noise include at least the ground transportation, aircraft, building services, industrial and human activities. For Hong Kong, which is a hilly, congested but highly dynamic city, this problem has become acute with the continuously growing population. Though the economy has not grown very fast in the past few years, the construction of large-scale infra-structures will eventually spread noise pollution issue from the urban areas to the sub-urban and rural areas. Every new establishment or re-development therefore requires serious noise pollution assessment before construction can be started. A reliable scheme for noise prediction is of prime importance for noise control within the existing and future environment. However, despite the effort of many researchers, such a prediction scheme does not yet exist. There are schemes which enable the estimation of noise level under a given traffic condition also but they are non-general and appear to be case/city dependent. They are to some extent uncorrelated such that ambiguous results can be obtained.
Experience and the results of the author's research, which will be discussed later in this proposal, suggest statistically that environmental noise, no matter it is outdoor or indoor, is not as random as the current researchers believe. It is highly probable that a generalized form of environmental noise level distribution does exist. This project is specifically intended to attempt to determine the form of such a distribution and contribute to the development of a theory for environmental noise. The outcome will contribute to the development of a reliable and informative prediction scheme for noise environment and may also find applications in the field of applied statistics.
An investigation on the effectiveness of balconies as noise barriers
(HK$359,075.5, The Hong Kong Polytechnic University)
Balconies at building façades are believed to be able to provide screening for noise from ground sources. However, the multiple reflections by adjacent balconies and the reverberation inside a balcony have resulted in noise amplification instead of reduction, especially at the low frequency range where resonance is likely to occur. The project is set up to investigate the actual effectiveness of balconies as noise screening devices for residential buildings. Methods to improve the screening effects of balconies on building facades will also be explored. These methods include the alteration in balcony shapes and the use of new durable passive sound absorbers in the balconies. A model will be set up for reliable prediction of balcony insertion loss. The results of the present results will be feedback to the profession for the setting up of ¡§good practice¡¨.
Development of a low pressure loss broadband silencer
(HK$677,040, Research Grant Council)
This project is an attempt to develop a low static pressure loss broadband compact silencer for practical use in buildings. The low frequency noise from the air conditioning system has long been a problem in the building industry. This is of particular importance for a high-rise and congested city like Hong Kong. The conventional dissipative silencer is intrusive, resulting in a considerable static pressure drop across it and thus high fan power consumption is resulted. The performance of the dissipative silencer is also not satisfactory at low frequencies. The concept of the two-dimensional drum silencer has been tested successfully in our laboratory. However, the effect of flow and the issue of optimization have to be done before a real product can be produced for practical use.
An investigation on improved sound and vibration transmission prediction for high-rise buildings in Hong Kong
(HK$170,000, The Hong Kong Polytechnic University)
In this project, theoretical models will be developed to predict sound and vibration transmission between building components. This will build on existing models used for European style masonry buildings. These models will be validated with laboratory studies of transmission between individual components. These laboratory measurements will be supported by extensive site measurements. Special attention will be made to improve the sound transmission performance at low frequencies and in the development of experimental techniques for large-scale projects. The present project will provide a deeper understanding on the properties of buildings and will also allow noise control schemes to be developed in the future.
Investigation of regenerated noise in ventilation systems
(HK$139,000, The Hong Kong Polytechnic University)
There is increasing concern about the noise generated by the interaction of air flow and duct elements in ventilation systems. This type of noise is known as regenerated noise. The accurate prediction and control of the regenerated noise in ventilation systems is of considerable importance in engineering. Nevertheless, the existing design methods such as ASHRAE Handbook and Part B12 of the CIBSE Guide for predicting regenerated noise due to air duct elements are recognized as being inaccurate in practical systems. This project builds upon the earlier work of the applicant on direct predictions of regenerated noise from turbulent kinetic energy in the vicinity of an isolated spoiler in air ducts using computer tools. The aim of this study is to extend the earlier work of the applicant to the study of situations involving two spoilers and to develop a generalized method of predicting regenerated noise in ventilation systems.
Study of structure-borne sound due to HVAC equipment
(HK$200,000, The Hong Kong Polytechnic University)
Study of interior sound fields using the finite element method
(HK$90,000, The Hong Kong Polytechnic University)
Despite the benefits of thermal comfort provided by rooftop equipment such as air-conditioning equipment, vibratory equipment can cause problems in an indoor acoustical environment. The building structure where the rooftop equipment is placed vibrates and emits sound into indoor space. Although considerable engineering work such as the installation of vibration isolators is employed, the amount of sound emitted by the structure of the building into the indoor space is still unclear. In order to reduce the interior noise levels at the design stage, it would be valuable if a computer-modelling technique could be employed to simulate the indoor sound fields caused by external vibratory forces imposed on the top of the room space. The aims of the study are therefore to model the interior sound fields due to vibratory rooftop equipment; and investigate the possibility of predicting and controlling the interior sound fields by a computer modelling technique.
Application and development of computer modelling techniques to the study of HVAC silencers
(HK$191,000 The Hong Kong Polytechnic University)
Concern has increasingly been expressed in Hong Kong over the quality of the indoor acoustical environment in office buildings. Noise from air-conditioning systems is usually one of the major sources of noise in offices. Various sources of noise are encountered in HVAC systems. Silencers are commonly used in a wide variety of applications. HVAC flow air ducts commonly make use of silencing elements to attenuate the noise levels carried by the air and radiated to the office environment. Restrictive environmental legislation, codes of practice and design guides for indoor environment require that such systems be designed with a high performance and reliability.
Various techniques are currently available for modelling and testing air duct silencers. Empirical, analytical and numerical techniques have been employed and have proven to be reliable under controlled conditions and for different applications and duct system configurations. For more complex geometries (larger attenuation values are required), numerical techniques such as the finite element method and the boundary element method are applied with advantage. The principal objectives of this research are: to model the silences in HVAC systems by computer simulation; and to analyse the performance of the HVAC silencers.
Researchers : Dr S W Wang (leader), Dr M L Chen, Dr S M Deng
Collaborator : Dr J N Cao, Department of Computer, The Hong Kong Polytechnic University
Prof A Dexter, Department of Engineering
Sciences, The University of Oxford,
Research Students : Mr Jet J T Cui, Miss J Y Qin, Miss Linda F Xiao, Mr X Xu
Research Associate : Dr Z M Jiang
Research Assistant : Mr S Lo, Mr Z Y Xu
The areas of expertise and strengths of this research group are related to the robust control, optimization and assessment strategies of building services system, fault detection and diagnosis strategies, dynamic simulation of building systems, building automation and intelligent building system technologies. This group is also active in the development of web-services for remote building monitoring and diagnosis. Training courses on intelligent building technology, building control and optimization have been offered to professionals in the industry.
An Intelligent Building Laboratory is established. It consists of two integrated intelligent building and building management systems, integrated BACnet controllers, an integrated LonWorks control networks, an integrated home automation system, building emulators, an IBMS integration and management software (IBmanager), teaching software packages (BMSonline and BACnetViewer), etc. The laboratory provides the test facilities for research and development on intelligent building system integration and BMS communication, advanced building system control, management and diagnosis, facilities management software development besides supporting teaching.
IB Manager Network
Sensor fault detection, diagnosis and evaluation of building management systems
(HK$405,000, Research Grants Council)
The objective of this project is to develop a suitable method and the strategies to detect faulty sensors, to diagnose (locate) the faulty sensors and to evaluate the magnitude of the sensor faults. The strategies are to be used in the advanced Building Management Systems to ensure and enhance that the monitoring and control of BMS and on computers to evaluate sensor faults using the data recorded in BMS commissioning stage to increase the efficiency and quality of BMS commissioning.
Fault validation and fault tolerant control of building automation systems
(HK$710,000, Research Grants Council)
In the building HVAC field, developments on fault detection and diagnosis have been focused on HVAC components and systems. However, the existence of monitoring and control faults in outdoor air ventilation control and air handling units of air-conditioning systems is a common problem for the application of BASs in Hong Kong as well as in other countries. As a consequence, faulty monitoring and controls result in poor indoor air quality and energy waste and affect the further development of BASs.
The objective of this project is to develop a strategy to detect/diagnose the faults (in flow, air temperature, and differential enthalpy and differential flow measurements) and correct or recover the measurements in the presence of bias or failure, and a relevant control strategy that can adapt itself to maintain acceptable control performance of Building Automation Systems in the presence of measurement faults.
Robust and optimal DDC control of outdoor air ventilation in buildings
(HK$470,000, Research Grants Council)
The objective of the project is to develop a robust ventilation control strategy that optimizes the ventilation management by taking into account both requirements for good indoor air quality and for minimizing the air conditioning loads and hence the energy cost. The demand controlled ventilation strategy detects the dynamic changes of the occupant load, and controls the outdoor ventilation airflow rate to follow these changes. The strategy improves robustness and accuracy of the ventilation control, with reduced sensitivity to CO2 and outdoor airflow measurement errors, in and between different modes of ventilation control.
Adaptive and optimal control building air-conditioning systems
(HK$240,000, The Hong Kong Polytechnic University)
The objective of the project is to develop and evaluate the strategies and methods for on-line control optimization of variable-speed seawater pumps, which is supported by real time parameter estimation and on-line prediction of system performance based on Genetic Algorithm and fuzzy-based supervision. On-line optimization is achieved by optimizing and resetting the pressure setpoint of seawater supply pressure.
This project includes the development and evaluation of the strategies for on-line identification of the essential parameters of indirect seawater cooled and direct seawater cooled chilling systems, to test and implement Genetic Algorithm in on-line parameter identification and on-line prediction of system performance, and to implement fuzzy-based strategies for supervision of the pressure setpoint reset control.
Development of an intelligent building platform integrating BMS and FMS on internet
(HK$200,000, The Hong Kong Polytechnic University)
In the recent years, there is a clear trend to adopt Internet/Intranet as the underlying infrastructure for intelligent building management. In this project, we aim at developing the framework and methods for integrating Building Management Systems (BMS) and Facilities Management Systems (FMS) using Internet and middleware. We will also develop techniques to support efficient remote access to the integrated system. Three main issues will be addressed:
• Integration of building control networks and Facilities Management via Internet;
• Development of middleware supporting convenient data exchange with client systems,
• Web-based remote access of BMS and database integration.
Fault diagnosis and sensor fault isolation of centralized chilling systems for intelligent management and robust control
(HK$200,000, The Hong Kong Polytechnic University)
Centralized building chilling systems are one of the major energy consumers. Building Management System has become an essential part of the system in the last two decades. The recent advances in network technology and the compatibility of BMS network protocols allows the Direct Digital Control (DDC) panels of individual chillers to be conveniently integrated into the BMS systems, allowing the BMS to have rich information including the internal component operational conditions of chillers and the chilling system.
However, nowadays, most Building Management Systems (BMS) installed in practical central chilling systems are not utilized sufficiently. The measurement uncertainties and errors, together with component faults, as well as the lack of diagnosis tools and software, result in unreliable monitoring, diagnosis and automatic control. In consequence, automatic controls of many chilling systems are not working properly and system/component degradations might be ignored for a long time.
The objective of this project is to develop methods/strategies for the detection and diagnosis of chilling plant degradations isolating the measurement errors, in order to achieve robust control, automatic commissioning and preventive maintenance. These methods/strategies will enhance the accuracy and robustness of monitoring, diagnosis and control, and therefore provide a means for improving building energy efficiency and intelligent control, benefiting the development of intelligent and sustainable buildings in Hong Kong.
Researchers : Prof Francis W H Yik, Dr C K Chau, Dr W L Lee,
Dr Daniel W T Chan, Dr J L Niu, Dr T M Chung, Dr S K Tang,
Dr H X Yang, Dr Horace K W Mui, Prof J Burnett
: Prof P Jones, The Welsh School of Architecture, University of Wales,
Dr Esmond Mok, Dr Lillian Pun, Mr Geofrey Shea of Land Surveying
and Infomatics Department, The Hong Kong Polytechnic University
Research Fellow : Prof M Bojic
Research Students : Miss Angela S H Chan, Mr T M Leung
Research Assistants :
The Department has made considerable progress in its research and development work in the area of building environmental performance in the past few years. Development of and major review on the different versions of Hong Kong Building Environmental Assessment Method (HK-BEAM) for new and existing office buildings and high-rise residential buildings has also been completed. A new and more comprehensive version of HK-BEAM for new and existing building developments was released in May 2003. The publicity of HK-BEAM has grown substantially in the past year reflecting greater awareness to Hong Kong¡¦s environment.
The Department is expanding the HK-BEAM scheme into an assessment framework that would embrace all types of buildings. In addition to the assessment schemes, the framework would include provision of supporting information and analysis tools to allow wider dissemination of the assessment scheme, the methods and techniques for evaluating the environmental performance of buildings, and measures for achieving higher standards. The Department is actively seeking collaboration with, and funding from, interested parties to develop the scheme.
The continuous enhancement of HK-BEAM also spins off a variety of coordinated active research studies. These studies include energy efficiency of building services, thermal performance of building envelopes, wind environment around buildings, natural ventilation and daylight applications in residential buildings, indoor environmental conditions, thermal comfort, building acoustics, human factors, building econometrics and decision making processes, benchmarking building environmental performance, development of simulation programs for prediction of energy and environmental performance of buildings and plants, life cycle analysis and economic factors to be considered in building environmental assessments.
Advanced building technology in a dense urban environment (Building environmental performance)
(HK$5,801,178, The Hong Kong Polytechnic University)
The project focuses on three major tasks, namely design optimization of new high-rise residential building envelop, design optimization of new air-conditioned buildings and the heating, ventilation and air conditioning systems and the benchmarking of existing buildings. In the first task, effects of all environmental aspects, such as wind and rain, solar heat, noise and lighting, on the built environment are analyzed with theoretical, computational and experimental techniques. Physical models for design are reviewed and re-defined. The second task is the development of the design software HTB2/BECON. The third task focuses on benchmarking performance of buildings. This is done through extensive site surveys and the applications of econometrical methods. Outputs are consolidated in the Hong Kong Building Environmental Assessment Method (HK-BEAM).
Development of a computer simulation package for studies on the environmental performance of buildings in Hong Kong in estate or district-wide scales
(HK$500,000, The Hong Kong Polytechnic University)
The aim of the project is to develop a computer simulation package for use in studies on the environmental performance of a group of buildings, such as buildings within an estate or in a district. On the basis of a geographical database built from GIS data, the program will be able to:
¡P Generate data for the description of the geometry of the buildings and the surrounding terrains in a selected geographical region in Hong Kong;
¡P Allow users to choose the boundaries of the area within which the building and terrain geometric data are required, to edit the geometric data to incorporate new buildings within the area or to make changes to the buildings and the terrain geometry, and to choose the data format for exporting the data that would meet the specific data input requirement of the simulation program to be used in the study, e.g. computational fluid dynamics (CFD) simulation of air-movement around the buildings; and
¡P Allow users to predict the solar and daylight intensities at the façades of the buildings, taking into account the inter-shadowing effect of adjacent buildings, and the simultaneous cooling demand of a large number of buildings in a district through using the calculation routines linked to the front-end of the program.
The project is intended to be a pilot study for the development of a more comprehensive program that will embrace a geographical database that covers the entire Hong Kong. The study focuses on developing the methodologies required for realising the abovementioned functions, leaving the more laborious tasks of repeating the methods for expanding the database to cover the entire Hong Kong to be done when subsequent funding can be made available.
Development of a multi-criteria decision making model for sustainable building development for Hong Kong
(HK$421,600, Research Grants Council)
With the increase in public awareness of environmental issues during the late 1980s and early 1990s, sustainable development is becoming one of the major policy issue of the Hong Kong SAR government. Policy makers are now facing additional challenges on how to prioritize the allocation of limited community resources in environmental issues. The most cost effective and efficient manner is through imposing statutory controls on issues that are most neglected and less focused by the developers and building designers. In achieving this, a model to predict how the developers and designers act when confronting with a set of diverse design issues is needed.
The principal objective of this research is to formulate a model to predict how designers and developers in Hong Kong will perform when they are confronted with tradeoff during a complicated design process. This in turn will become a decision making tool for the policy makers to formulate environmental strategy at the most effective way. The findings of this proposed study can help to reveal the amount of money that developers are willing to pay for various design attributes, ranging from aesthetics, indoor air quality, acoustical performance to environmental impact.
The long-term significance of this study is to enhance our understanding of the behavior of developers and designers towards a diverse set of design issues. This understanding can provide insight for the policy makers to formulate a regional strategy for allocating the limited community resources in the most effective and efficient manner during their pursuit of sustainability excellence. The major value to policy makers lies on how statutory controls should be imposed on issues that affect the social and environmental cost for a district, city, country or region at large. The proposed study can also help to train students to gain interdisciplinary knowledge and experience in building design and impact assessment process.
Determining Resource Impact Factors for Buildings in Hong Kong
(HK$198,000, The Hong Kong Polytechnic University)
The principal objective of this study is to develop a set of resource impact factors for evaluating the potential environmental impact of the various environmental stressors. The primary focus of the environmental stressors in this study is energy use and recycling. Besides, it is the intent of this study to develop a systematic approach to derive a weighting scale for various environmental stressors. In this study, a new weighting scale based on the relative potential impact of various environmental stressors will be derived.
The long-term significance of this study is to enhance our understanding of the potential impact of environmental stressors. Furthermore, the proposed study can potentially contribute to the formulation of a more valuable building assessment scheme for Hong Kong, which in turn would lead us to use our resources more effectively and efficiently.
Energy Policy for Building Environmental Performance Model in Hong Kong
(HK$83,722, The Hong Kong Polytechnic University)
From a previous study, the energy consumption between the traditional and Building Environmental Performance Model (BEPM) air conditioning system was calculated. The coil load for the traditional air conditioning system in the measuring year of a building was 15,104,054 kWh. With the integration of the BEPM, the total coil load was 14,020,000kWh, with percentage saving of 7.15%. For the fresh air load, the energy consumption of the traditional system was 2,690,000kWh and with the BEPM was 2,250,000 kWh, with percentage saving of 16.4%. The total energy saving was 1,520,000kWh for the updated system. Assuming the unit cost of the electrical bill was HK$ 0.86 per kWh, the saving of the energy cost was more than HK$ 1.3 million per year. Therefore, when BEPM concept is promoted to all the air conditioned building in Hong Kong, a huge amount of saving in energy cost can be achieved.
This study aims to enhance and prompt the conventional operation of the air-side system by incorporating temperature reset with adaptive comfort temperature control, in order to save energy, by achieving a realistic adaptive comfort temperature. Together with the new demand control ventilation system and other quantified uncontrollable system parameters, the energy required to combat the hot and humid climate in high-rise buildings in Hong Kong will be more effectively used.
A novel approach for resolving the priority issues in the building energy and environmental assessment scheme for Hong Kong
(HK$240,000, The Hong Kong Polytechnic University)
Many voluntary building environment assessment schemes have emerged around the world as tools intended to improve environmental performance and help achieve sustainability. The voluntary approach, offers greater flexibility for building owners to reach targets so as to gain a better public image, and is useful for the policy makers to promote dialogues with the private sector and to raise public awareness of environmental issues. The assessment process is usually conducted by comparing the assessed building against a set of prescribed quantitative and qualitative performance indicators of diverse objectives. Credits will be awarded to the assessed building once the listed criteria are fulfilled, to offer encouragement in achieving the environmental objectives. To ensure a successful voluntary environmental assessment scheme, the credit allocation strategy adopted should be able to award more credits to the profit-oriented developers for a diminishing economic return.
This research is to formulate a strategy of incorporating developers¡¦ economic interests into the credit weighting structure of Hong Kong Building Environmental Assessment Method (HKBEAM), and to provide insight for the scheme owners and policy makers to rescale the current weighting allocated to the diverse objectives. The formulation of credit weighting scale begins with the development of Economic benefit-cost ratios and Environmental impact-cost ratios for various criteria. This will help the developers to prioritize criteria selection for achieving a maximum number of credits at a minimum cost under the current assessment scheme; to enhance our understanding of the potential impacts of performance indicators economically and environmentally; and to train the students to have the multidisciplinary perspectives in building environmental impact assessment.
Life cycle energy analysis of building construction
(Contract research project, Electrical and Mechanical Services Department, HKSAR Government)
Sustainable building development requires a clear understanding about the environmental and economic impacts of buildings, from cradle to grave, and how the impacts can be minimized through optimizing the design. The project involves the development of a Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) tool for commercial buildings in Hong Kong. The tool is to include a database on life cycle impacts and costs for various building materials and services systems and an efficient recurrent energy use prediction model.
According to ISO 14040, an LCA involves four interacting stages, including goal and scope definition, inventory analysis, impact assessment and result interpretation. Although LCA models for buildings are available from overseas vendors, the inventory databases that accompany such models contain data that are specific to their respective places of origin. For applications in Hong Kong, such data would need to be edited to reflect the actual situations in the local construction industry. Corrections to the inventory data to be made include the energy mix in the countries of origin from which Hong Kong imports construction materials, the energy use and the associated impacts incurred due to transportation of the materials to Hong Kong, the energy use and waste generation due to local construction activities, and the demolition of buildings and treatments for the construction and demolition (C&D) wastes.
Unfortunately, LCA is, as yet, a new concept seldom practiced in Hong Kong, and virtually no life cycle inventory data are available. The approach that will be taken is to use, as a starting point, inventory data that are available in established databases that are commercially available. The unit processes involved in the production of each building material/component, from extraction of raw materials through disposal of the building material/component, and the impacts associated with each unit process, will be identified. Those unit processes that are significantly different from local practices (e.g. construction methods and C&D waste handling) would be replaced by data that are appropriate to local situations; and processes missing (e.g. shipment from place of production to Hong Kong) will included. This requires a detailed understanding of what types of building materials and services systems are used in commercial buildings in Hong Kong, the construction processes used in building sites, any off-site processing and pre-fabrication work, and C&D waste handling in Hong Kong. These form the objectives of the survey part to be undertaken in the proj ect.
Since the life cycle energy use of a building and to a large extent the life cycle cost of the building as well is dominated by the re-current energy use during the occupied stage, the LCA/LCC study should include predictions of the impacts of using alternative building design features on the re-current energy use. Given that numerous options may be considered during the design stage, an efficiency simulation tool that can account for the effects of changes in use of materials is essential. The development of a building energy prediction model that can satisfy this need is also included as a part of the project work.
Researchers : Dr K T Chan (leader), Mr Joseph H K Lai, Prof Francis W H Yik
: Prof P Jones, Welsh School of Architecture, Cardiff University,
Research Student : Mr Ringo H K Lee
It is essential that the building services systems can function to satisfy the user expectation and provide healthy and safe indoor environments. While achieving these requirements, it is also important to keep down the operating cost and maintain a high standard of service. This requires a proper design of the systems, a sound operating strategy, and an effective maintenance programme. Research work on O&M aims to benchmark the performance of installed services systems, establish energy effective operating strategy and preventive maintenance programme, develop methods to improve system efficiency in a cost-effective framework, and provide feedback of system operation to the design process.
Development of operation and maintenance strategy for systems performance optimization of hotel building services
(HK$505,321, Industrial Support Fund, with Hotel Grand Stanford Inter-continental)
This research project is undertaken under a Teaching Company Programme set up between The Hong Kong Polytechnic University and the Grand Stanford Inter-continental Hong Kong.
In hotels it is essential that the building services systems can function to satisfy the user expectation and provide healthy and safe indoor environments. While achieving these requirements, it is also important to keep down the operating cost and maintain a high standard of service. This requires a proper design of the systems, a sound operating strategy, and an effective maintenance programme.
The scope of this research project is to evaluate the performance of the hotel's existing services systems and to develop methods to improve system efficiency in a cost-effective framework. The existing systems will be investigated for any necessary retrofitting for energy conservation and environmental protection. This includes evaluation of the system retrofitting alternatives and development of energy effective operating strategy and preventive maintenance programme.
To realize the objectives of this project, it requires a close involvement in the operating and maintenance activities in the hotel. A teaching company scheme will best suit this requirement by appointing a teaching company associate (TCA) to work with the hotel maintenance team for two years.
The rationale for effective operation and maintenance of building services systems has been receiving much less attention than it deserves. Also, system designs are often developed with little concern on operation and maintenance requirement. This project will contribute to the development of a rational approach to achieve effective system operation in hotels, and will demonstrate an example in the feedback of the operation and maintenance experience to design.
Progress has been to:
¡P Evaluate the performance of the existing systems through a detail energy audit;
¡P Establish operation and maintenance structure;
¡P Analyse effects of O&M on energy and environmental performance;
¡P Establish schemes for maintenance decision making;
¡P Develop models for cost-effective maintenance and criteria for maintenance performance assessment.
Economic, management and contractual considerations in outsourcing operation and maintenance work for commercial buildings
(Staff development programme, The Hong Kong Polytechnic University)
Operation and Maintenance (O&M) work in buildings is traditionally undertaken by in-house O&M staff employed directly by building owners. In recent years, the economic downturn triggered downsizing of companies, which is often associated with outsourcing the building O&M work.
The success of outsourcing hinges on a complete set of equitable and enforceable contractual conditions, which should be able to clearly define the obligations and liabilities between the employer and the contractor. Inevitably, forming, enforcing and monitoring the contract work will incur transaction costs although the benefit of reduction in in-house manpower resources may outweigh these transaction costs. All in all, the total costs and benefits, both pecuniary and non-pecuniary, should be thoroughly scrutinized before an outsourcing decision is made.
Problems are often encountered in executing/managing outsourced O&M contracts, which arise from such as ambiguity in defining the demarcation of the scope of the contract work, varied interpretation of contract terms and unwillingness of in-house staff to cooperate with the contractor. Investigating the causes and finding solutions for these problems should be of great value to the industry.
With regard to the topic, a research study with the following objectives has commenced in Jan 2003:
¡P To investigate the current management practices in in-house and outsourced operation and maintenance (O&M) work in commercial buildings.
¡P To investigate various problematic contractual conditions taking into account relevant statutory requirements and trade practice in outsourced O&M contracts.
¡P To evaluate the performance of outsourced O&M contracts from monetary and quality service viewpoints.
¡P To make clear the impacts of management, contractual and economic considerations to the success of outsourcing O&M work.
¡P To develop a framework to guide building management to make outsourcing decision.
A number of representative commercial buildings in Hong Kong will be selected for conducting the study. Data will be collected mainly via site visits, questionnaire surveys and interviews with O&M contractors and building owners. The data/results so obtained will be analyzed, in order to explore problems and opportunities and finally, to derive constructive recommendations for the practice of outsourcing O&M work.
Researchers : Dr Y P Du (leader), Dr M L Chen, Prof J Burnett
: Prof W S Dong, Cold and Arid Regions & Environmental Engineering
Institute, Chinese Academy of Sciences,
Prof Y J Zhang, Chinese Academy of Meteorological Sciences,
Prof Z C Fu, Institute of Electrical Power, Shanghai JiaoTong
Research Fellow : Dr J Z Wang
Research Students : Mr Sammy S K Kong, Mr Z H Yuan, Mr Q B Zhou
Research Assistant : Mr C P Chen
This research team is in pursuit of innovation of advanced technology in electrical installations and systems in buildings. Current research is focused on power quality & control, electromagnetic environments and protection against lightning. The topics in the area of power quality & control includes modeling of electrical distribution systems, analysis of power quality events (harmonics, surge, etc.) in systems, harmonic mitigation and control using active power filters or others, and reliability of electrical equipment and systems. The topics in the area of electromagnetic environments include identification and modeling of low-frequency, high-frequency and pulse interference sources, characterization of electromagnetic environments, mitigation and control of electromagnetic fields, and electromagnetic shielding. The topics in the area of lightning protection includes characterization of lightning-caused transient currents and fields, model for prediction of probability of lightning striking to a building, effects of bonding and earthing practices on lightning current dispersion, mechanism of building-triggered upward lightning, and development of new effective lightning rod/air terminals.
The research in this group will underpin the development of guidelines, tools and products for quality electrical services in buildings. A design guide of magnetic fields for electrical installations has been developed. A software package for evaluating magnetic fields in buildings is currently available. A novel filtering network for control harmonics in building distribution systems is being developed. A new lightning rod/terminal, with which lightning risk to buildings can be effectively reduced, will be designed and tested soon.
The research team has a strong relationship with local industry, especially in building services industry. The team has been involved in more than 20 consultancy projects in the past five years. Most of the projects were related to investigation, analysis and mitigation of electromagnetic interference associated with electromagnetic fields, harmonics, surges, etc. Design of electromagnetic shielding rooms is another key area of the consultancy service.
Development of harmonic impedance database for LV power cables
(HK$$487817, Research Grants Council)
Electric cables are widely used for low-voltage power distribution in buildings. As harmonics continue to increase in commercial buildings, harmonic analysis is increasingly being undertaken to solve and/or avoid harmonics-related problems. The analysis requires a knowledge of circuit impedances of distribution cables at harmonic frequencies. Such information is also required in the energy-efficiency code, recently published by the Hong Kong government. However, the harmonic characteristics of low-voltage cables specified to British Standards have not been sufficiently addressed, nor is a harmonic impedance database available to aid designers.
This project is focused on the development of harmonic impedance database of power cables used in low-voltage electrical installations. The objectives of this project are (1) to develop the methods for impedance characterization and measurement at harmonic frequencies; (2) to develop an impedance database of low-voltage cables for harmonic analysis; (3) to develop semi-empirical and/or numerical models of cable impedance for prediction purpose. The project will investigate the methods of impedance characterization and measurement at harmonic frequencies, and provide technical information necessary for harmonic analysis in buildings, as well as development of harmonic regulations in Hong Kong. The project outputs will assist the engineers in achieving harmonics compliance, and having electromagnetically compatible power supply in the buildings.
The electromagnetic environment in high-rise buildings during direct lightning strokes
($535,000, Research Grants Council)
Traditionally, the problem of building lightning protection was addressed by electrical engineers from the point of view of safety and insulation design. The increasing use of susceptible electronic equipment in buildings in recent decades has made it necessary to investigate the problem also from the view point of electromagnetic interference, or electromagnetic compatibility (EMC).
Building lightning protection systems are composed of three parts, i.e., the air terminal, the down conductor, and the earthing system. In modern practices of building lightning protection, the reinforcing steel structures are often adopted as the down conductors. During a direct lightning stroke, the lightning current, up to hundreds of kilo-amperes, distributes in the different parts of such structures and generates impulsive magnetic fields inside the building. It may create interference problems, such as, damages to or malfunctions of susceptible electronic systems.
Recognizing that there is insufficient work done in this area for the high-rise buildings in Hong Kong, this project is proposed (1) to Develop models of lightning protection systems, and application software for computation; (2) to study surge current distribution in conducting structure, as well as impulse magnetic fields in the premise of a building; and (3) to carry out laboratory measurement for model verification.
Design guide of magnetic fields for electrical installations in large buildings
($465,000, Research Grants Council)
High-tech equipment continues to proliferate in modern buildings for business use. Such equipment (e.g. video display units) is often susceptible to power-frequency magnetic interference, and requires a ¡§clean¡¨ magnetic field environment for operation. It was showed that VDUs were likely to be affected by an external ELF magnetic field as low as 10 mG. On the other hand, electric power consumption in the buildings keeps on increasing. The power-frequency magnetic field environment is getting worse. Tens of mG magnetic fields in the office areas are not uncommon. Interference problems in buildings are increasingly being experienced.
The development of comprehensive design guidance for building electrical services is the main goal of the research project. It will be achieved by (1) identifying practical situations in buildings, (2) studying mitigation and shielding techniques applied for building electrical systems and (3) developing evaluation software. There are five major sections covered in the guide: fundamentals, modeling & analysis, magnetic field characterization, interference to VDUs and magnetic field mitigation.
System-level control of harmonics over building distribution systems using a coordinated filtering network
(HK$400,000, the Hong Kong Polytechnic University)
Voltage and current harmonics, which may cause operation problems of distribution systems and end-user equipment, are of concern increasingly in buildings. As tenants usually complain to landlords whenever there are harmonic problems, it is necessary to develop a cost-effective tool for landlords to control harmonics over building distribution systems.
This research project proposes to develop a filtering network, in which distributed active filters are coordinated via a central unit to maintain system harmonic voltage at appropriate levels, to keep harmonic current injected into supply networks within the limits, and to minimize system losses and other harmonic indices as well. The issues of its architecture and control will be addressed. As the landlords will be provided with the tool for control of system harmonics, harmonic limits given in IEEE Std. 519-1992 can be complied to ensure a compatible environment in buildings. The tariffs on excessive harmonic currents from end-user equipment will become technically feasible as well.
Modeling of high current, low voltage busbar and cabling systems in buildings
($478,400, Research Grants Council)
The quality of the electricity supply to tenants is increasingly of concern in recent years. The quality is defined in terms of electromagnetic phenomena, such as voltage stability, voltage balance, voltage distortion, transient, as well as electromagnetic field emission, and is greatly affected by the distribution systems in buildings.
This project investigates the electromagnetic phenomena associated with low-voltage distribution cables and busbar systems in buildings. It aims to (1) to quantify and model the impedance and magnetic fields of busbars and high current capacity cable risers in low-voltage installations; and (2) to provide design and operational data for use in existing commercially available software code, or suitably modified code.
Study of lightning electromagnetic pulses and currents for building lightning protection
(HK$202,000, The Hong Kong Polytechnic University)
The use of electromagnetic susceptive instruments in modern buildings has brought increasing concerns of electromagnetic interference associated with lightning. This project aims to investigate the characteristics of lightning currents and transit electromagnetic fields radiated by lightning, in order to discuss the optimal protection scheme for buildings against lightning. The specific objectives include: (1) investigating the signatures of currents of lightning strokes, and identifying the main factors affecting lightning currents; (2) observing and analyzing the transit electromagnetic fields radiated by lightning, and unveiling the features of electromagnetic pulses produced by lightning during its various developing stages; (3) discussing alternative measures for limiting the magnitude of lightning currents and shielding radiated fields from lightning, and suggesting improvements for lightning protection.
Modelling of the path of lightning striking to a building for lightning protection study
(HK$400,000, The Hong Kong Polytechnic University)
A lightning strike to a building has the power to penetrate through roofs, to cause walls of bricks and concrete to partially explode, to ignite deadly fires, and to cause electronic equipment to malfunction or permanently damaged. Traditionally a lightning protection system (LPS) is used to protect buildings and its contents. It is intended to intercept lightning discharges and channel the discharge current directly to ground. However, many studies have reported that lightning discharges ignore the dedicated lightning protection system (LPS), and strike directly the roofs or sidewalls of a building instead. Such phenomena cannot be explained with traditional lightning protection theories. The traditional LPS design may prove ineffective.
As one step of long-term research on lightning protection in buildings, this project aims to develop a simulation model for lighting discharges to high-rise buildings, and to study statistical characteristics by incorporating the structural detail into lightning study. The objectives are (1) to identify the major factors affecting the development of lightning, and to propose a physical model for lightning discharges to high-rise buildings; (2) to develop a numerical simulation approach based on the proposed model.
Architecture shielding in modern building during lightning strokes
(HK$200,000, the Hong Kong Polytechnic University)
As sensitive electronic systems continue to proliferate in modern buildings, electromagnetic interference is increasingly of concern. Lightning, as a high-discharge phenomenon, is a major source of electromagnetic interference in buildings. It can cause equipment to malfunction or to be permanently damaged.
Steelwork is an essential element in a high-rise building, which can alter the electromagnetic environment during a lightning strike. As little research work has been performed on the shielding effects of building steelwork, we propose a research project with the objectives; (1) developing an electrical model for the study of shielding against lightning impulsive fields; (2) developing theoretical tools for shielding analysis; and (3) evaluating shielding performance and properties of structural steelwork during a lightning strike.
Researchers : Prof Francis W H Yik, Dr K T Chan, Dr T Y Chen, Dr T M Chung, Dr S M Deng, Dr W L Lee, Dr J L Niu
: Prof P Jones, The Welsh School of Architecture, University of Wales,
Prof M Bojic,
Research Students : Mr H C Lam, Mr Z Li, Mr Z P Lin, Mr F W Yu
Research Associates : Dr I Lun, Dr Paul S K Sat, Dr Kenny S Y Wan, Mr J Yang, Ms H Zhang
Research Assistant : Miss E Fung
Heating, ventilation and air-conditioning (HVAC) of buildings is the dominant electricity end-use in Hong Kong. Enhancing building designs to reduce reliance on HVAC systems for indoor comfort and air quality control, and enhancing the energy efficiency of HVAC systems, are the key means to energy conservation and environment protection. There is much room for improvement in respect of design, installation, testing and commissioning, and operation and maintenance of buildings and HVAC systems. As the project descriptions below will show, the Department is active in research in this important area. The research covers development of methods and computing tools for more accurate and efficient prediction of heat transfer in buildings and indoor environments; methods for optimising system performance; design features that allow greater use of natural ventilation and daylight; methods for assessing and benchmarking performance; and new technologies for HVAC and energy studies. Focus is currently on commercial, hotel and residential buildings.
Development of environment responsive façade engineering to enhance liveability, sustainability and energy conservation in optimized design of public housing
(HK$1,284,000, Housing Authority Research Funds)
The objectives of the project include:
¡P to determine façade design features that have the potential to substantially enhance the liveability, sustainability and energy conservation in optimised design of public housing in Hong Kong;
¡P to assess the technical feasibility and economic and environmental viability of the various features for application to new public housing designs and to retrofit existing public housing in Hong Kong;
¡P to estimate the benefits that could be derived when such features are extensively applied to new and existing public housing in Hong Kong;
¡P to establish further research directions and plans, such as experimental verifications of the effects of features that are identified to have great potential, for confirming the effectiveness and identification of problems that may be encountered in construction; and
¡P to demonstrate the application of simulation tools to the evaluation of the benefits of various unconventional / innovative design features, including how such tools should be used, caution that should be exercised in their use, and their limitations.
Feasible façade features include:
¡P Strategic use of thermal mass, insulation and surface finish material for attenuating and delaying space heat gains;
¡P Optimised design of shading devices (e.g. vertical, horizontal and inclined fins and canopies), including fixed devices and adjustable devices;
¡P Use of walls with naturally or mechanically ventilated cavity and vent shafts for advantageous utilisation of the buoyancy driven air flow and the thermal inertia of the fabric for ventilation provision and control of the indoor thermal environment;
¡P Use of fin projections to guide wind flow or create desirable pressure differences for enhancing cross natural ventilation;
¡P Use of windows with ¡§smart¡¨ glazing, double-glazing, with or without inter-pane ventilation or cooling water circulation;
¡P Use of windows with external, internal and inter-pane blinds, or inter-pane film(s), for reducing solar and conduction gain;
¡P Use of reflectors (motorised or fixed) to deepen daylight penetration or to better distribute the daylight into premises.
Various façade design options, such as those listed above, would have varying degrees of impact on façade design, the construction processes and cost, reliability in operation and complexity in maintenance. Among the options identified during the study, those that would function without the need for sophisticated controls, regular maintenance and continued supply of energy should be preferred. The economic viability of the options would require particular attention, as the investments would be from the public purse. An option should be taken only if it would lead to benefits that outweigh its cost to all stakeholders from a life cycle perspective. Given the numerous features available, the focus for the study would be to identify the most promising façade design features that would be technically feasible and economically and environmentally viable for application to public housing designs, so as to enhance the liveability, sustainability and energy conservation in optimised design of public housing in Hong Kong.
Method and data for modelling humidity in residential buildings in Hong Kong
(HK$537,817, Research Grants Council)
Due to the hot and humid climate, buildings in Hong Kong are subject to problems caused by high humidity, such as growth of mould and mildew, peeling of paint or wallpaper off walls, etc. Besides degradation of building materials, high indoor humidity will cause thermal discomfort, mould infestation can have serious adverse health implications for occupants, and intense dehumidification load will lead to greater energy use for air-conditioning. Humidity problems are more acute in residential buildings than in commercial buildings. The presence of more and intensive moisture sources (e.g. bathroom and kitchen), less extensive provision of air-conditioning, and higher rate of transport of outdoor air, through open windows or by infiltration, into residential buildings explain for the differences in the impacts of high humidity on the two types of buildings. Therefore, the proposed research will concentrate on residential buildings.
Central to the formulation of mitigation methods for humidity problems in buildings is the ability to accurately predict humidity levels that may arise in buildings. However, a practical simulation tool for such studies is not yet available. Application of heat and moisture transfer models may also be limited by unavailability of moisture transport property data for building materials, although more data have been made available recently. Furthermore, data for quantification of the intensities of various moisture sources that present in residential flats in Hong Kong are lacking.
The proposed research has the target to establish a suitable simulation tool, and the required data, for the prediction of humidity levels inside residential flats. Surveys and experiments will be conducted to obtain data on the intensities of various moisture sources. Experimental measurement of moisture adsorption and desorption characteristics of building and furnishing materials will also be conducted, if the required data are not already available in the literature. On the basis of the survey, measurement and simulation results, moisture levels likely to arise in residential flats can be predicted, which will allow the severity of humidity problems to be assessed and guidelines on active and passive methods for mitigation of moisture problems to be formulated.
Control methods for optimising fan energy use in variable air volume (VAV) air-conditioning systems
(HK$485,000, Research Grants Council)
Up to 50% of the energy use in a typical office/commercial building in Hong Kong is for air-conditioning which is shared between the central chiller plant and the air-handling equipment in the ratio of about 60:40. Having recognized the dominant load, most building energy efficiency improvement initiatives focus on improving the efficiency of the chiller plant. Apart from retrofitting variable air volume (VAV) systems with fan inlet guide vane control to variable fan speed control, few have been done to further improve the energy efficiency of the air-side systems.
Recent advancement in direct digital control technology has given rise to new opportunities to significantly reduce the fan energy use in VAV systems. The key to this is to minimize the need of throttling the air for controlling flow rate. The recently proposed terminal regulated air volume system and duct static pressure reset algorithm are feasible schemes but much work still need to be done to bring such conceptual system control methods into practical use. This proposed research work aims to develop a practical control method along the line of these concepts and will include detailed simulation studies for identifying and solving the associated problems. Laboratory and in-situ experiments will be included for quantification of the effectiveness of the methods under real operating conditions.
Modeling and control of a VAV air handler with a DX coil
(HK$423,000, Research Grants Council)
Variable Air Volume (VAV) air conditioning (A/C) systems can offer greater fan energy saving potential during part load operation, and therefore find wide applications in buildings all over the world. Although using a Direct Expansion (DX) cooling coil in VAV air handlers can offer more advantages than using a chilled water coil, DX cooling coils have rarely been used in VAV air handlers, mainly because of the inability to match the cooling capacity of the condensing unit with a varying VAV load.
This proposed project aims to develop a novel capacity control strategy that helps eliminate this inability, through mathematical modeling and laboratory experimental work. A dynamic mathematical model for a VAV air handler with DX coil will be developed and experimentally validated, based on the previous separate modeling work for both DX refrigeration systems and VAV air conditioning systems. The model so derived can provide essential insights to system dynamics, and will be useful in developing the novel capacity control strategy. This novel capacity control strategy will be based on the principle of energy balance and a number of real-time measured key operating parameters in VAV air handlers with DX coil to adjust the compressor speed for capacity control of the condensing unit.
Successfully carrying out the proposed project will help improve the energy efficiency of building air conditioning, and reduce the capital and maintenance cost of air conditioning installations in buildings, both in Hong Kong and elsewhere.
Optimum condensing temperature at part-load operation of air-cooled chillers for energy efficiency
(HK$457,817, Research Grants Council)
Air-cooled chillers are often designed to work at the summer design conditions. During the intermediate seasons and winter, the cooling plants have also to operate because of the high internal load, and there is opportunity for the chillers to operate at lower condensing temperature and hence higher efficiency. However, there are no developed methods nor quantifying analyses to support the operation at reduced condensing temperature and the energy saving potential has not been explored.
This project is to develop a possible control strategy for air-cooled chillers at part-load conditions for energy saving. The objectives are:
¡P To investigate the operation of air-cooled multiple-chiller plant at part-load under the local climatic conditions;
¡P To develop control method for possible operation at lower condensing temperature of air-cooled reciprocating chillers in mild weather;
¡P To determine the reduction of energy consumption by implementing the above control of air-cooled chillers used in commercial buildings.
The long-term significance of this proposed project rests on its contribution to energy conservation in the building sector of Hong Kong. The outcome, i.e. condensing temperature control method and part-load operating strategy of air-cooled chillers, will support building operators in setting operating scheme of cooling plant and cutting the electrical bill, and enable building services engineers to evaluate energy effectiveness of chiller plant design alternatives in the design stage. As the volume of buildings will continue to grow, and the electricity consumption by buildings will continue to be the major energy outgoing in Hong Kong, it is essential to develop energy saving measures for efficient operation of cooling plant.
Energy performance studies for hotel buildings in Hong Kong
(HK$260,000, The Hong Kong Polytechnic University)
There has been an increasing interest in studying energy efficiency and performance in buildings including hotel buildings. In Hong Kong, in a typical medium size hotel, the annual energy bills might amount tens of million of dollars, contributing significantly to hotel¡¦s total operating cost. This has also adverse impact on our environment.
With the energy and water consumption data available from a total of 17 quality hotels, this project is proposed to o carry out a detailed analysis of energy consumption data from the 17 hotels in HK;, so that an energy signature (or performance line) for each hotel buildings, which is related to average occupancy and external weather condition, may be obtained; In addition, an energy database for hotel buildings audited (Survey of major building services systems, instrumentation, energy use index, etc.) will be developed, Finally, guidance on future building services systems design for hotel building to achieve energy efficient operation will be provided.
A study of a desuperheater heat recovery system complete with a reversibly used water cooling tower (RUWCT) for hot water supply
(HK$560,000, The Hong Kong Polytechnic University)
Recovering heat rejected from the condenser in a refrigeration system to generate service hot water for buildings is commonly seen in both tropics and subtropics. This has the advantages of increasing the overall energy efficiency of a refrigeration system and reducing heat pollution to the environment. It is also advantageous in minimizing the total installation and operating costs, because the need for a boiler plant may be eliminated.
This study included a critical literature review on heat recovery from air-conditioning / refrigeration systems, with particular emphasis on the direct condenser heat recovery and its related mathematical simulation models. The review identified that the application of desuperheaters to recover heat has concentrated on small-scaled residential air-conditioning or heat pump units. Moreover, during cold seasons in subtropics, there may not be sufficient heat from buildings to be recovered due to reduced building cooling loads. Consequently, backup heating provisions, usually by electricity, are often required.
In order to provide a year-round service hot
water supply without requiring backup electric water-heaters, an existing
standard water cooling tower may be used in a reverse mode, as part of a desuperheater heat recovery system, to extract heat from ambient
air in subtropics when necessary. This reversely used water cooling tower
(RUWCT) can be an idle cooling tower in an air-conditioning plant. A number
of RUWCTs have been successfully installed and operated
in subtropics in southern
The heat and mass transfer characteristics of a RUWCT have been studied in greater detail, which is based on the theory of direct contact heat and mass transfer between moist air and water. The thesis reports on the differences in heat and mass transfer process taking place in a RUWCT, a standard water cooling tower and a spray room. A corrective factor that accounts for the change of chilled water mass flow rate is incorporated in the theoretical analysis of a RUWCT. The condensation of water vapor from moist air causes the change in chilled water flow rate. The introduction of the ratio of latent heat to total heat transferred helps to complete the theoretical analysis, and to better understand the heat and mass transfer characteristics in a RUWCT. The algorithms developed from the theoretical analysis are capable of predicting the heat exchange capacity of a RUWCT at any operating conditions. This theoretical analysis is the first of its kind.
Extensive field experimental work on the heat and mass transfer characteristics of a RUWCT has been carried out in a hotel building in Haikou, Hainan province of China, where the RUWCT is installed. Results from the experimental work indicate that the theoretical analysis can represent the heat and mass transfer characteristics in a RUWCT with an acceptable accuracy. Furthermore, a procedure for calculating the thermal performance of a RUWCT has been developed based on the theoretical analysis and the field experimental work.
A numerical analysis for a RUWCT is undertaken to determine both air and water states at any horizontal sections along the tower height. A set of simultaneous differential equations has been developed to describe the correlation of fluid parameters and their variations within the tower. These differential equations are solved by a fourth-order Runge-Kutta method. The numerical analysis can help to better understand the variance of air and water states inside a RUWCT. Field experimental data confirm that the calculated air and water parameters at the tower inlet and outlet based on the numerical analysis are acceptable.
A steady-state mathematical model is developed to simulate the operational performance of a water chiller plant complete with a desuperheater heat recovery system and a RUWCT. The simulation results based on the technical specifications of the same plant used in the RUWCT experimental work indicate that the model is stable and behaves as expected. With the aid of the model developed, a number of the operational parameters of such a heat recovery system have been studied. This model will be useful in future studies on the optimum design of a water chiller complete with a desuperheater and a RUWCT for heat recovery.
Studies of establishing methodologies for assessing building energy efficiency, with particular reference to large air conditioned buildings in Hong Kong
(HK$200,000, The Hong Kong Polytechnic University)
Energy consumption in various buildings for operating building engineering services systems accounts for a significant part of total energy consumption in many parts of the world. One of the most effective ways is to establish a set of systematic methods to assess the efficiency of energy utilisation in existing buildings. However assessing the efficiency of building energy use is difficult because energy used in buildings is to maintain suitable indoor built environment and to provide building occupants with quality services, which cannot be easily quantified using energy terms.
The proposed project is to investigate establishing a set of appropriate methodologies for assessing the efficiencies of total building energy use and of energy use by various building services systems, using Energy Performance Index (EPI).
The project will develop a systematic approach to the assessment of efficiency of building energy use. This will be preliminary modelled based on buildings in Hong Kong, but the principles can be applied to all buildings in other parts of the world, with appropriate modification.
The use of heat rejected from residential DX air-cooled condenser for clothes drying in Hong Kong (HK$250,000, The Hong Kong Polytechnic University)
Clothes drying, done for ages by the Sun and wind, has become in industrialized societies an important consumer of electrical or other energy forms through the use of tumbler dryers. In Hong Kong, clothes drying has become increasingly confined to indoors due to convenience if not regulation. On the other hand, residential buildings in Hong Kong are air conditioned by either window type or split type air conditioners. This presents an opportunity for the re-use of heated air after passing through an air cooled split type DX air conditioner for drying clothes, thus improving the energy efficiency of residential air conditioning or clothes drying and reducing heat pollution to the environment.
Both laboratory experimental work and mathematical modeling work will be included and the major emphasis will be put on the mathematical modelling to study the effect of clothes drying using heat rejected from a split air conditioner's condenser. The experimental work to be involved will be limited to investigating the clothes-drying process using warmer air exiting from an air cooled condenser of a residential air conditioner. A split type residential air conditioner will be purchased and a temporary enclosure for hanging wet clothes after spinning drying in a washing machine will be built. Experiments will be carried out at various condenser air mass flow rates and various heat rejection rates (i.e., various air conditioner operating conditions) to quantify a clothes-drying process in terms of drying rate (drying time required). Comparative studies of drying clothes with and without heated air from a condenser will be included.
The proposed project will cover an economic analysis of the use of heated air exiting from a residential DX split type air conditioner for clothes drying. The experimental comparative studies would provide adequate data for carrying out such an analysis. The analysis would also compare the total cost involved in this proposed drying approach with that by using electricity drying. It should also be noted that condenser heat is only available when an air conditioner is used in air conditioning seasons from April to October in Hong Kong.
A prototype of the enclosure to be used as a drying chamber will be designed after the experimental work, so that the dimensions can be optimised, and the suitable arrangements for clothes hanging will also be studied.
Strategies for air conditioning in bedroom in subtropical area
(HK$560,000, The Hong Kong Polytechnic University)
Traditionally, air conditioning is used in workplace (e.g., office buildings), in public places (e.g., museum), and therefore currently design standards for building air conditioning are based on these traditional applications. However, with the increase of living standard, the residential air conditioning has become increasingly important. One of residential air conditioning applications is for air conditioning in bedroom to maintain a suitable sleeping environment for occupants (for example, in Hong Kong SAR, air conditioning is used overnight for several summer months so that people can sleep well). The objectives of the proposed project are as follows:
A detailed review on the research work about sleeping which is a branch of medical science will be firstly carried out. It is expected that the review will provide much useful information on suitable sleeping environment and on the quality of sleep. This will be followed by further review on any other work relating to thermal comfort, particularly in sleeping environment.
In the study of determining thermal comfort in bedroom, subjective questionnaire and objective measurement approach will be adopted. Objective measurement will be done in a controlled environmental chamber (available in the laboratory of BSE department) where indoor thermal parameters can be varied, and body surface temperatures of testees will be measured, under different body covers of various clo values. Questionnaire survey for subjective evaluations about the thermal comfort and IAQ in bedroom both in Hong Kong and in Shanghai will be undertaken.
In the study of fresh air requirement in bedroom, experimental approaches will be adopted. Air quality indicators such as CO2 will be continuously monitored during a sleeping process, under various fresh air supply rates.
In order to determine the characteristics of cooling load for a bedroom, both experimental and computer simulation approaches will be adopted. A typical bedroom in a residential flat in Hong Kong will be selected where extensive experiments will be conducted to measure the actual cooling load during a sleeping process. Computer simulation by using reputable commercially available software packages will also be carried out using the same bedroom's building parameters. Estimations of sensible / total heat ratio and the energy use for residential energy use may then be derived.
The outputs of this project will also give useful suggestions to air conditioners' manufacturers to improve their products for bedroom application.
A new grey-box method for efficient and accurate prediction of building cooling load
(HK$200,000, The Hong Kong Polytechnic University)
The currently available building energy prediction methods are too time-consuming for use in sustainable building designs that involve impact evaluation for an extensive range of design options. A new grey-box method will be developed to largely speed-up building cooling load estimations without sacrificing accuracy. Parameters that characterise transient heat transfer through multiple-layered walls will be derived from first principle. The required model, in the form of semi-symbolic transfer functions, will be derived based on semi-symbolic network analysis techniques. A large set of annual cooling load data will be generated through detailed simulations, which will then be used to determine the coefficients in the semi-symbolic transfer function model. Since all the influential variables of a building are embedded in the model, it will be able to reflect the impacts of using different design options and will be an efficient tool for optimal design and life-cycle analysis of buildings.
Cost planning model for effective implementation of demand side management for commercial buildings in Hong Kong
(HK$200,000, The Hong Kong Polytechnic University)
Demand side management programme (DSM) is defined as the implementation of measures to influence the amount or timing of customers¡¦ energy use, so that capital expenditure on new generating equipment can be postponed, and also, to minimise the impact on the environment. In Hong Kong, the first Utilities sponsored DSM resource plan was implemented on 1st July 2000, and is scheduled for a period of 3 years. The budget allowed for all the rebate-type DSM programmes, are expected to last throughout the scheduled resource period. There include rebates for the use of energy efficient lighting and HVAC installations in non-residential premises. After one year of implementation of the DSM programme, the budget allowed for the lighting rebate programmes has already been exhausted, but there is still large amount of surplus for the HVAC rebate programmes. Low participation rate for the HVAC rebate programmes and over-subscription of the lighting rebate programmes indicate that a review of the budget and the rebate allocation strategy of the DSM programme are needed. The aims and objectives of this project are to formulate a cost planning model for the most appropriate budget and rebate allocation strategy to maximize the reduction of CO2 emissions for the commercial buildings in Hong Kong.
Development of building energy simulation software HTB2 and BECON
(HK$200,000, The Hong Kong Polytechnic University)
Designing energy efficient buildings involves evaluation of the cooling loads of various indoor spaces and the energy use for indoor environmental control as the building is subject to changes in the weather and the occupation conditions. These studies require a suitable computing tool to help handle the complex calculations involved for modelling the thermal performance of the building envelope and the air-conditioning system, including various feasible design options.
Besides being a detailed building heat transfer simulation model, HTB2 offers a high degree of flexibility in the definition of occupancy, lighting and equipment loads, infiltration rates, on/off patterns of heating and cooling systems and indoor control set points for the simulation. Thus, the complex patterns that would arise in real buildings can be modelled in detail.
A special version of HTB2 has been developed which, in conjunction the air-conditioning system simulation program BECON, can predict the energy use for air-conditioning in complex buildings in Hong Kong. BECON is incorporated with air-conditioning plant models that would allow it to simulate the performance of most types of air-conditioning system designs that can be found in commercial buildings in Hong Kong.
Current applications of HTB2 and BECON, as a package, include:
¡P Assessment of energy performance of buildings under the HK-BEAM scheme;
¡P Various consultancy studies, including the Preliminary Phase Study on Wider Application of Water-cooled Air-conditioning Systems in Hong Kong; and
¡P Design and research projects involving evaluation of overall building and system energy performance, by staff and students in the Department.
Further development of HTB2 and BECON continues, including front-end developments for enhancing the user-friendliness of the programs, and the range of systems the program can model. A special version of BECON for modelling district cooling systems has been developed. Integration of HTB2 and BECON to become a simultaneous building and air-conditioning system simulation program is on going. At present, a model that can predict the performance of VAV systems serving multiple spaces has been developed.
Another version of BECON, named as BECRES, is available for predicting electricity use for air-conditioning in residential buildings, where window or split type air-conditioners are used.
Cointegration analysis of electricity demand in association with energy efficiency of commercial and residential buildings
(HK$200,000, The Hong Kong Polytechnic University)
This project aims to evaluate the impact of energy efficiency and the growth in the stock of commercial and residential buildings on the future electricity demand in the Hong Kong SAR. The study has two components, namely the analysis of the implication of energy saving measures on energy requirement and the development of an electricity demand forecast model. In the first component, the Building (Energy Efficiency) Regulation, the codes of practice for energy efficiency of air-conditioning and lighting installations will be investigated. Alternative design options for building envelope construction and unconventional energy conservation schemes in commercial and residential buildings will be studied with the aid of energy simulation software. In the second component, the economic factors, seasonal weather changes and the types and volumes of new buildings will be investigated for electricity demand forecast. The influence of the codes of practice for energy efficiency and system design options for energy saving will then be coupled to the electricity demand prediction model.
Macro energy demand trend analyses in other countries often do not embrace building performance factors. This project attempts to incorporate the technical performance of building energy saving measures into the energy forecast model. The research will produce new results quantifying the significance of energy saving measures in commercial and residential buildings on the total energy consumption in Hong Kong and the prediction of electricity demand in future for planning and policy making. The results will also illustrate the degree of importance of building design factors on energy consumption at macro level, and therefore will be significance worldwide. The objectives are:
¡P To assess the changes of building energy requirement by implementing building envelope design alternatives and codes of practice for energy efficiency of air conditioning, electrical and lighting installations.
¡P To determine the relations of total electricity demand with economic changes, seasonal climatic changes, stocks of buildings and energy effectiveness of building systems.
¡P To develop an econometric model of electricity demand, using a cointegration technique and error-correction method.
¡P To predict the range of electricity demand in the short-run and long-run using the results of building energy simulation and the econometric model.
Researchers : Dr J L Niu, Dr Daniel W T Chan, Dr C K Chau, Dr C M Mak, Mr G Powell,
Dr M Y Chan, Dr Horace K W Mui, Dr S K Tang
: Prof Per Heiselberg, Hybrid Ventilation Center, Aalborg University,
Prof Phil Jones, University of Wales, UK
Prof R Y Zhao and
Prof H F Di, Department of Building Science and
Technology, Tsinghua University,
Prof H Yoshino, Tohoku University, Japan
Prof R Luo, Tsinghua University, Dr Z J Zhu, The University of Science of Technology of
Research Fellow : Dr Thomas Tung
Research Student : Mr N P Gao, Mr Leo K C Law, Miss Emma S H Leung, Mr F Li, Miss Cinnie Tam, Mr C S Wong, Mr H T Xu
Research Associate : Dr Issac Lun
Research Assistant : Mr Jacky Cheng, Mr K W Shek, Ms Jean Tang
Our research in Indoor Air Quality embraces the following areas:
¡P Development of low-energy air conditioning systems, which integrate radiant cooling, desiccant dehumidification, and personal ventilation systems.
¡P Application of turbulence modeling and CFD(computational fluid dynamics) for building ventilation study; assessment of spread risks of air-borne and droplets-transmitted diseases in built environment
¡P Characterization of indoor air pollutant emission from building materials and development of standard testing methods;
¡P Total exposure assessment of Hong Kong population to indoor air pollutant; evaluate the economic health benefit associated with improvement in indoor air quality.
¡P Indoor air quality control in special premises: schools; underground carparks; shopping malls
¡P Tracer-gas technique for building ventilation measurements
¡P Development of air-cleaning technologies including PCO(photo-catalytic-oxidization) technologies
Also, consultancy services are provided to the local government and industry in the following aspects:
¡P Diagnosis of indoor air quality, and auditing of building energy consumptions
¡P Testing of air-cleaning efficiencies of commercial products
¡P CFD(Computational fluid dynamics) analysis of building ventilation and wind environments
Integration of desiccant cooling and cooled-ceiling in commercial air-conditioning systems
(HK$495,000, Research Grant Council)
This project aims at the research and development of an alternative air-conditioning system, which integrates the emerging chilled-ceiling technology for sensible heat removal, and the desiccant technology for moisture removal. The objective is to develop a computer model that will be able to simulate the performances of such a system, and to use the integrated model to perform an overall system simulation to study the annual energy consumption of various system configurations, and the indoor air quality and comfort level that is achieved. The outcome is expected to be conceptually applicable system configurations, comprising detailed life-cycle cost analysis, and performance estimations, and design calculation procedures. It is envisaged that this system combination is likely to replace the current primary-air-unit and fan-coil-unit combination design that is widely used in large air-conditioned commercial buildings. The system offers independent humidity and temperature control, greater potentials of using natural cooling and low-grade energy sources, and better economy of using CFC-free refrigeration systems. It is expected that, based on the exact outcome in these aspects, further funding will be obtained from the industry and a working system will be built for demonstration.
Optimized air supply temperature and velocity with radiant cooling and desiccant humidity control a/c systems
(HK$581,817, Research Grants Council)
Indoor thermal comfort is affected by environmental parameters including air temperature, air movement characterized by mean velocity and turbulence, air humidity, and mean radiant temperature affected by window insolation and wall surface temperature. A conventional air-conditioning system in cooling mode typically aims to control the air temperature, humidity, and air movement in terms of mean velocity. This is typically achieved by supplying a cold air of around 14¢XC. The inherent characteristics of this air-conditioning mode are that it is the cold air that has higher velocity, which is counter to what the human body desires. Design engineers have to limit the air velocities in occupied zones to avoid risks of drafts. As a result, overcooled air-conditioned room, which is in strong contrast with the hot and humid outdoor climate, has become the practice. This has a number of undesirable consequences regarding thermal comfort, indoor air quality, and energy conservation.
This project will investigate the new indoor environmental characteristics that can be achieved with a hybrid air conditioning system. The system combines chilled-ceiling and desiccant-dehumidification, the former controlling both radiant and air temperatures, and the latter controlling the humidity and air movement. The system offers more independent or separate control of the four environmental parameters. Ventilation air can be supplied to the proximity of occupants at a raised temperature with raised air-movement, which will be controllable by the occupants. Our hypothesis is that this system will be favorable for improving indoor air quality, raising thermal comfort acceptability, and reducing energy use. Finding the optimum combination of these environmental parameters and the air diffuser design to realize this combination are the objectives of the proposal.
Numerical and experimental investigations of PER and thermal comfort under micro-climate control conditions
(HK$503,083, Research Grants Council)
A conventional air conditioning (AC) system is designed to create a uniform environment in the whole occupied zone defined as the space up to 1.7 meter from the floor. There are two obvious problems: a). Fresh air is mixed with indoor air pollutants prior to its inhalation by the occupants. b). Individual thermal preferences are not accommodated. In addition, there is an inherent energy-wasteful feature. Displacement ventilation systems improve the ventilation effectiveness to a certain extent by utilizing thermal stratification. The so-called task air-conditioning (TAC) system aims to satisfy individual preferences. A more novel system is to direct the fresh air supply to the human nose prior to any possible mixing with pollutants. Our hypothesis is that this direct ventilation method can be best incorporated into a TAC system.
This research aims to develop a new generation of air-conditioning system with significantly high energy-efficiency and pollutant-exposure-reduction (PER) efficacy. To this end, we will develop a numerical thermal manikin (NTM) of realistic geometry, with proper thermal boundary conditions derived from human physiology studies, and integrate the NTM into Computation fluid Dynamics (CFD) model. The numerical simulation will be validated against measurements using a state-of-the-art physical thermal manikin. With the validated NTM, our focus will be on the interaction between any direct air supply methods and the respiration flow and the thermal plume around the human body. Finally, a comprehensive thermal comfort and PER will be assessed under a microenvironment AC system, which will integrate radiant cooling, individual air movement control and direct ventilation air supply.
Developing mass-transfer-based models for the prediction of indoor air pollutant emissions from building materials in real buildings
(HK$469,404, Research Grants Council)
Building interior materials have been identified as significant indoor air pollutant emission sources. Selecting low-emission building products is a more cost-effective solution to improve indoor air quality (IAQ), compared with ventilation method, which is energy-intensive in both cold and hot, humid climates. The aim of this research is to develop experimental and mathematical-modeling methods for the quantification of pollutant emission from building materials in their actual use conditions.
Emission test chamber and emission test cell are two types of testing facilities developed over the years to characterize material emission processes. Current standards only require that the emission rate profile be documented. The problem is that the emission rate thus obtained is test-condition specific, and can only be used to compare and rank the emission strengths between the tested samples under the specific test conditions, but cannot be extended to predict the pollutant concentrations in a real building. To evaluate the actual impact of a particular material on indoor air quality, modeling methods based upon mass transfer and sorption theories are required. For this purpose, emission test cell can be used to explicitly determine the model parameters required in a comprehensive IAQ model. In this project, the European pre-standard emission test cell called field and laboratory emission cell (FLEC) will be adopted, in view of its low cost and good repeatability, and potential to be adopted as a standard in Asia.
We apply fundamental mass-transfer methods to analyze the pollutant emission processes in a standard test cell. The surface convective mass¡Vtransfer coefficient and the material internal diffusion processes will be experimentally determined separately so that the material phase properties identified in this way are independent of test conditions. The results can be used to analyze the pollutant levels in actual use, so that proper selection criteria can be set-up based upon the health impact, and applicable IAQ control strategies can be evaluated.
Fuzzy air quality indices for management of indoor air quality in air conditioned buildings
(HK$324,000, Research Grants Council)
Building services engineers cut the first corner of indoor air quality (IAQ) in the 1973 when the oil embargo triggered off a new era in energy conservation. ASHRAE Standard 90-1975 and 62-1983 allowed outdoor air ventilation rate to set as low as 2.5 l/s/person in non-smoking air-conditioned offices. Unfortunately, building occupants have used the synthetic material indoor abusively. All these incidences triggers off the well known ¡¥Sick Building Syndrome¡¦ which incurs billions of dollars in medical costs and lost in working proficiency as well as the loss of lives due to the ¡¥Building Related Illness¡¦.
Despite the tremendous effort put into research and engineering to right the wrongs, IAQ seems to be an unavoidable problem issue in air-conditioned offices. In the past decade, research workers spent a great effort in determining effective solutions to revert the IAQ back into acceptable conditions. The enlightenment lies in two directions. First, the traditional IAQ criteria are found to be erroneously set at two polarized extremes between health and comfort conditions only. This prompts the research workers to look into the in-between uncertainties regions which generally inducing the more well known health complaints of ¡¥sick building syndrome¡¦. Second, the two most important IAQ criteria for volatile organic compounds and bioaerosol are so little known that they remain as two blind spots in all management schemes for acceptable IAQ.
In this study, the criteria for the whole range of IAQ conditions will be reviewed and a new approach will be developed for setting acceptable IAQ criteria. It will involve the transformation of semantic variables developed in a sick building syndrome model into a range of IAQ criteria meeting various building management and investment plans. The uncertainties in the semantic variable is best evaluated by the fuzzy logic theory. Then the two types of indicators for VOC and bioaerosol will be fundamentally interpreted with respect to their constituents. VOC will be analyzed by using the GCMS system, and the bioaerosol will be analyzed by three systems ¡V the MIDI, Biolog and Riboprinter methods. To make these results practically applicable, a new indicator will be developed for the VOC and bioaerosol. First of all, VOC and bio-markers will be determined by calibrating with the building factors. The neural network technique will be employed to take into account of the dynamic nature during the building life cycle so that the VOC and bioaerosol indicators can be constantly updated and regenerated.
Development of an ICU extraction equipment for preventing the transmission of contaminant exhaled air in intensive care unit (ICU) or isolation ward of hospital
(HK$95,000, The Hong Kong Polytechnic University)
In 2003, the World Health Organization received reports of ¡§Severe Acute Respiratory Syndrome (SARS)¡¨ in various parts of the World. Until the 13th of June, there were 1755 people affected by atypical pneumonia in Hong Kong. While the mechanisms of the SARS is till under investigation, there are much information released which enable the engineers to develop a system to reduce the risk of spreading of SARS in the hospital. The outbreak of SARS also prompts the building services engineers the need to review the current air circulation patterns around the patients indoors with the objective to develop a new type of systems to reduce the risk of microbial disease.
This study developed a personal respiratory protective equipment with the capability of reducing risk of the nosocomial transmission of SARS. A prototype was built, and airflow, velocity profile measurements and smoke tests were performed. It was found that the performance of the extractor is well correlated with the design specification.
A new composite thermal comfort and indoor air quality model for air-conditioned offices
(HK$453,404, Research Grants Council)
Central air-conditioning systems have been used extensively in high rise buildings in Hong Kong since 1960s. Unfortunately, the Cantonese translated the term wrongly to literally mean ¡¥Cold Air System¡¦. Since then, the notion that air-conditioned space has to be ¡¥cold¡¦ has been deeply implanted into the minds of occupants. Even when energy conservation became a design issue due to the energy crisis in 1973, the call for colder indoor air temperature still prevails. Dressing codes with a relatively high clo value (higher clothes insulation) in summer has consequently become a culture in offices. Given the stock of office buildings in Hong Kong, the energy spent on cooling the clothes in summer is very significant.
On the other hand, indoor air quality (IAQ) has attracted a great deal of concern. IAQ remains an undetermined issue because there are many unknowns, hence ¡¥not under control¡¦ factors. While models for thermal comfort (ASHRAE S55-1995) and IAQ comfort are well developed, the thermal comfort and IAQ comfort are not so well established in real life. It is largely due to the lack of a near field study between the interaction of air circulation and the human body. In particular, thermal and IAQ comfort are investigated as a composite quality which reflects the realistic total state of the mind to an individual¡¦s immediate environment.
This study utilizes the opportunities of a rare collaboration between the building services engineering (BSE) and the textile and clothing (T&C) disciplines, and the availability of both a ¡¥thermal manikin¡¦ and a newly designed ¡¥perspirative manikin¡¦. An empirical thermal comfort evaluation system is presently being constructed which links the thermal manikin and an indoor thermal comfort evaluation stack for near field measurement. Dr. Fan from T&C has developed a heat transfer model for cloth materials and dress configuration. The combined efforts from these two departments aim to produce the near field performance of three types of air circulation patterns for three most prevalent types of air side system: variable air volume system, fan coil system and displacement system. The deliverable is a new composite thermal comfort and IAQ model and a data base for air-conditioned offices, to enhance the office indoor environment, and to support the choice of air-conditioned system to match the activities and culture of a company occupying indoor spaces. In particular, the results will enable the designers to control the indoor environment appropriate to various indoor scenarios.
The total exposure assessment of Hong Kong population to various air pollutants
(HK$680,371, The Hong Kong Polytechnic University)
There is much concern in Hong Kong about people exposure to pollutants, including indoor pollutants. Whilst pollutants indoors are a major interest of building services engineers, the exposure to such pollutants must be set against the exposure overall. The exposure to a pollutant could be defined as the event when a person comes into contact with a pollutant of a certain concentration during a certain period of time. Although exposure itself is not a direct health risk indicator, the adverse health risk effects associated with the pollutants found in the environment can be determined based on the total exposure assessment and epidemiological study. One of the critical information needs for total exposure assessment is the detailed data on human activity patterns among the subgroups since these parts can determine the duration, frequency and intensity of exposures.
Although numerous efforts have been undertaken to quantity the concentrations of various pollutants in different outdoor and indoor microenvironments, time exposure is always a missing puzzle in their research masterpiece. Accordingly, there is a need to have a reasonable accurate estimate on the total exposures of the population to various environmental air pollutants and this aspect will be addressed in the proposed study.
The primary objectives of this study is to obtain representative information regarding the activities and locations of Hong Kong population, especially those specific activities and locations which are most relevant to air pollutant exposures. The study also was designed to permit some comparisons among various demographic subgroups of Hong Kong population. The pollutants going to measure in this study are those identified to have significant health impacts to human beings, which include Carbon Monoxide, Nitrogen Oxides, Sulfur Dioxide, Total Volatile Organic Compounds, Respiratory Particulate, Bioaerosol and etc.
Survey of energy consumption and indoor thermal environment of Chinese urban residential buildings and development of sustainable indoor climate technologies
(Funded by Japanese National Science Foundation)
with Prof H Yoshino (Tohoku University, Japan), Prof R Y Zhao (Tsinghua, China), Prof J P Liu Xi¡¦an University of Arch. & Tech g, China)
Development of individually controlled environmental system
with Prof R Y Zhao and Prof H F Di, Department of Building Science and Technology, Tsinghua University.
Evaluation of turbulence model and numerical methods for CFD application to Built environment studies,
with Dr Z J Zhu, The University of Science of Technology of
Validation of CFD simulation of single-sided ventilation
Prof Per Heiselberg, Hybrid Ventilation Center, Aalborg University,
Researchers : Dr T M Chung (leader), Prof J Burnett, Daniel W T To
: Dr J Mardaljevic, IESD, De Montfort University,
Research Students : Miss H D Cheung, Mr T T To
Current research efforts in lighting can be divided into two major areas: daylighting and artificial lighting. Daylighting research concentrates on the study of assessment methods for high-rise buildings in dense urban areas. A study on the feasibility of applying horizontal light pipes for high rise buildings in Hong Kong has been initiated. Artificial lighting research deals with the effect of temperature on new family of fluorescent lamps which are designed to operate at high ambient temperatures.
Research Projects :
A new schema to quantify solar access and daylight availability for dense urban environments
(HK$433,404 Research Grants Council)
The high density urban environment in Hong Kong poses a challenge to the society of Hong Kong in maintaining the quality of the living/working environment in accord with environmentally responsive designs that allow adequate access to sunlight and daylight. Requirements stipulated in the current Building Ordinance are out-dated. This project will develop a new protocol to quantify solar access and daylight availability for dense urban environments. It will employ a newly developed image-based technique to predict the total annual irradiation across building facades in complex urban settings. A comparison will be made between the new technique and a standard approach that is based on simple, overcast sky conditions. Occupant and building surveys will relate user satisfaction of daylighting and electric lighting usage to the solar access and daylight availability as quantified by the irradiation mapping and daylight simulation. The optimum ¡¥packing density¡¦/form for high-rise building developments will be determined on the basis of maximizing solar access. Proposals to adopt quantification of solar access and daylight availability in planning decisions will be made. It is expected that this research will help the establishment of a performance-based building regulation on solar access and daylight availability. The findings will also have relevance for the assessment of the economic viability of building integrated photovoltaic installations on building facades in Hong Kong.
Applicability of horizontal light pipes for daylighting multistorey buildings in a dense urban environment
(HK$452,812 Research Grants Council)
Due to an increasing demand for an improvement in indoor environmental conditions and a need for energy saving, utilization of daylight in buildings has become more important. Daylighting in high rise buildings located in dense urban environments has always been a challenge to building designers. Daylight can only penetrate a limited depth from the window wall, heavy obstructions make the daylight penetration depth even smaller. The invention of passive solar light pipes and other innovative daylighting systems which bring natural light deeper into the building may provide a solution to the problem. However, there is a lack of data of the performance of light pipes in multistory buildings in urban locations. This project will investigate the performance of light pipes which transport light horizontally in high density urban environments. It will employ mainly computer simulation study to produce data of daylight availability and light transport performance of light pipes. The interaction of the external daylight with the optical properties of light pipe systems will be studied. Dynamic illuminance simulations will be undertaken using a state-of-art lighting simulation software. The results from this study will be useful for the analysis of the cost effectiveness and acceptability of passive solar light pipe and other innovative daylighting systems. The findings will contribute to the sustainable development of buildings in the world.
Investigation of the luminous and electrical performance of different combinations of lamps and ballasts
(HK$50,000, The Hong Kong Polytechnic University)
Different combinations of fluorescent lamps and ballasts may have quite different electrical characteristics and light output performance. Luminous characteristics of lamps are usually given only for standard photometric conditions. Lighting design calculations use the manufacturer quoted light output values which are supposedly tested under standard photometric conditions. Designing using these standard photometric values when ¡§non-standard¡¨ combinations of lamp and ballast are used and when operating conditions differ to the standard photometric conditions may cause significant error. Little guidance has been given by lighting codes as to how to correct for non-standard photometric conditions. This proposed research would provide data for the correction with respect to non-standard operating conditions. The electrical characteristics of lamp-ballast systems will have effect on the power quality of a building. This is an important issue especially for electronic ballasts which, for products in the market, may employ widely different circuits and have a wide range of quality. Dimmable electronic ballasts will also produce a significant amount of harmonics. Data produced in this proposed research will help lighting and electrical services engineers to select lighting products and to apply measures to improve power quality if necessary.
Design guidelines for fluorescent lighting installations with digital control-gears
(HK$180,000, The Hong Kong Polytechnic University)
Dimmable electronic ballasts which can be linked to detectors of illuminance, motion and infrared signals will become more popular in early 21st century as the price become lower. Current design calculations were developed for the fixed output lighting installation. This proposal makes hypothesis that the photometry properties and maintenance factors of lamps and luminaires for use with fixed output ballasts may not be applicable to the design of installations that employs dimmable ballasts and constant illuminance sensors. Hence, studies are proposed to investigate into the problem with an aim to give recommendations for the design of lighting installations using variable output ballasts and digital control gears.
Data and model to establish daylighting criteria for building environmental assessment in Hong Kong
(HK$218,718, The Hong Kong Polytechnic University)
In recent years, the Department of Building
Services Engineering developed the HK-BEAM scheme. One of the items assessed
is daylighting design. However, due to the lack
of local data, the daylighting criteria are based
essentially on recommendations and guidelines used in the
It is proposed to carry out experimental measurements using scale models and computer simulation using a powerful lighting simulation program to obtain data for validation of the current daylighting assessment criteria.
Daylighting design and assessment methods for high-rise buildings in dense urban environments
(HK$732,000, The Hong Kong Polytechnic University)
This project addresses the problem of the lack of assessment tools and criteria for daylighting design in Hong Kong. The first task of the project is to review existing Building Regulations in Hong Kong on daylighting requirements and to compare these requirements with similar codes or standards in other countries/areas. Then a review will be carried out concerning the methods and parameters/variables used for regulatory control for daylighting and for assessing daylighting design for good practice. An assessment of user perception and preference of daylighting will be carried out. The final aim of the project is to develop a set of performance-based assessment criteria for daylighting requirements in buildings in Hong Kong.