ICEE proposal
Mega-City Energy Efficiency and Ventilation– an improved Hong Kong model for better energy
efficiency and better air environment
1. Proposed Area of Focus (1 page mx)
Its importance
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Rapid urbanization in China and India has led to debates in favor of high-rise compact
and cities because of land saving and better energy efficiency. Nearly 70% of the
Chinese population will live in cities by 2030. Hong Kong is the most energy efficient
city in the developed world, often partly attributed to its high-rise compact city design.
Can Hong Kong become a model for large cities in other developing countries in the
region?
Both the building and transportation energy consumption are rising rapidly in China. 30
billion m2 buildings will be built in the next 20 years, on top of the existing 40 billion m2.
Past energy efficiency studies focused on equipment and system, building envelope,
operation and maintenance, and our data shows that urban form may be the determining
factor in energy use, which also affects the human behavior.
Serious pollution and extreme heat episodes in cities do not generally result from sudden
increases in pollutant emissions, but from meteorological conditions that diminish the
ability of the atmosphere to disperse pollutants, thus indicating the crucial role of urban
ventilation. The removal ability of pollutant and heat of a city probably determines the
city’s maximum size and maximum population density. HKU has been one of the first in
studying city ventilation.
Major challenges
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Our proposed study is challenged by the scientific difficulties in large-scale field
measurement, as well as the inability of existing computer simulation methods in
resolving tens of thousands of buildings in a city. The variable building heights causes
significant flow fluctuation at the urban canopy level, which also makes the field
measurement difficult.
Existing research mostly focuses on monitoring, meteorological studies considering
buildings as a roughness surface and wind engineering studies often deal with one
building or a building cluster. Our new state of the art turbulence porous model will allow
us to analyze the detailed airflow and heat transport at the city scale (5-20 km), but
further development is needed.
The energy consumption and anthropogenic heat data in individual households have been
difficult to obtain mainly attributed to the diversified energy usage behaviors. A detailed
survey on the energy consumption in Hong Kong will help understand the energy
consumption pattern and understand the impact of the urban form. The development of
smart meters offers such an opportunity.
2. Strength at HKU (1 page max)
Team members
Coordinator: Yuguo Li [ME]
Principal investigators: CH Liu (MECH), PC Lai and Mellissa Hart [Geography],
Stephen Lau and KP Cheung [Architecture], *Victor Li [EEE], *Wang Wenping
[Computer Science], *KM Lam [Civil Engineering] - *(new team members)
Synergy and record of collaboration
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HKU is well positioned among the other comparable institutions in Hong Kong and
indeed in the world, as we were one of the first to identify this major scientific problem.
We also developed the preliminary porous turbulence modelling approach together with
fast efficient computational algorithms that will allow us to analyze the detailed air flow
and heat/pollutant transport with the urban canopy layer (5-20 km). We have pioneered
our study in city ventilation and the transportation of heat and pollutant at city scale,
which provides the fundamental knowledge of heat/pollutant transport in a city.
This ICEE project is expected to provide new directions to building energy efficiency and
rapid air quality control in the rapid Chinese urbanization process. A new dimension of
the urban environment problem is identified, i.e. the removal mechanisms of airborne
pollutant from the urban canopy layer in high-rise compact cities. The length scale of the
urban canopy layer is between the meso-scale and the local street/neighborhood scale.
The proposed study needs a group effort from different disciplines. The preliminary study
by the project teams on different aspects (ME: building services and urban wind and
thermal environment; Geography: urban heat islands and applications of GIS;
Architecture: energy efficiency and urban compactness, ME & Civil: meso-scale and
urban wind climate; Geography: application of GIS; and CS: computer visualization)
demonstrates the need for such a project beyond an individual department level.
Our major weakness is lack of the expertise in meteorology (as compared to HKUST and
CityU). However, a new post-doc from the Institute of Atmospheric Physics at Chinese
Academy of Sciences has been appointed and due to arrive in February 2010.
Collaboration has been established with the HKUST, PolyU, Nanjing University,
Institute of Atmospheric Physics, New York University, University of British Columbia
etc.
The existing team members worked together in the past 2 years. A RGC group project
was submitted and shortlisted in 2009. Joint RGC projects/proposals between members in
the past years.
3. Sustainability of the Team (1/2 page max)
Our HKU team has initiated the city ventilation research for the last 3 years – just at the start of
ICEE. We have emerged as one of the major institutions in the urban air pollution research in
Hong Kong with a new direction and with a potential for a major impact.
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A short-listed RGC group proposal has been submitted and interviewed. The
unsuccessfully proposal at the end will be revised and submitted to Energy and
Conservation Fund.
We are in the process of discussing with the Energy Efficiency Office and Planning
Department on the possible promotion of our Hong Kong model idea.
We are in the process of applying for a Croucher Foundation Advanced Study Institute in
this area.
We are also in the discussion with Tsinghua University on the study of city ventilation in
the national 12.5 plan.
We are in the process of discussing with the major developers on the promotion of the
reasonable high-rise compact city model of Hong Kong in the mainland China.
We are part of the International Energy Agency Ann3x 53 project on energy use in
buildings with more than 10 participating countries.
Expected internal/external support
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Continuing GRF grants
ITF grant for innovation of energy and urban planning technologies in city urban air
pollution.
A theme based research proposal could be initiated.
4. Work Plan (1 1/2 page)
The following studies will be carried out as part of this project.
Project 1 – Mega-city ventilation - Multi-scale ground field measurements and multi-scale
computer simulations and wind tunnel analysis
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Improvement of the multi-scale city ventilation model based on the porous media
approach. Responsible: Yuguo Li and Chun-Ho Liu
Further development and application of a measurement system for urban ventilation at a
district level. Responsible: Yuguo Li, and Chun-Ho Liu
Development of a simplified geometrical model of the urban profile in Hong Kong for
the modelling. Responsible: PC Lai
Wind tunnel testing for model development. Responsible: KM Lam
3D dynamic visualization of complex air flows using virtual reality technology and fast
geometric modeling of realistic city buildings and terrains.. Responsible: Weiping Wang
Ground based field measurement –A modest monitoring network of 60 carbon monoxide (CO)
sensors is being developed in an existing smaller RGC project on city ventilation, a few on the
mountain slope and in the harbour, and most in streets to be installed at pedestrian level (1.5 m),
middle level (50m) and high level (100 m) in the central area along the principal and secondary
streets in the Sai Ying Pun control volume. These sensors can automatically record the data for a
month or more. The collected data for fair weather conditions will be chosen for analysis during
both summer and winter seasons. We will add additional 60 temperature/relative humidity
sensors in the ground based measurement network. Various mobile monitoring stations will also
be used for this study if additional fast response CO sensors can be purchased. The mobile
stations include the use of the city tram which runs the east-westerly street along Hong Kong
island northern shore (8 km from the east to the west at the harbour level), the peak tram along
the peak slope (allowing a vertical measurement of up to 400 m), two selected buses on fixed
routes on Hong Kong island and Kowloon each, and two taxis which run randomly on Hong
Kong island and Kowloon each (in Hong Kong there are so-called Kowloon and Hong Kong
island limited taxis). An additional network will be developed in the Mong Kok control volume.
Multi-scale air quality and thermal environment simulations – The grid resolutions and domain
sizes for air quality studies range both spatially and temporally over 5-7 orders of magnitude.
The air quality in a building (length 1-10 m) is associated with that of the neighborhood scale
(length 100 m – 1 km) close to the building, which is associated with the whole city scale (length
1-10 km) air quality, and then the regional scale (length 50-200 km) air quality and finally the
global-scale atmospheric physics and chemistry. Meso-scale (regional-scale) meteorological
models generally assume hydrostatic conditions, while for building scale, the Reynolds-averaged
turbulence equations are solved (computational fluid dynamics). Evidentially, solving the fullrange of spatio-temporal scale is beyond the capability of the conventional CFD approaches and
modeling algorithms.
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There will be a development for further enhancement so that the urban canopy layer
climate can be studied. The first is to enhance the capability of our porous turbulence
model to include the effects of thermal flows.
The second effort is to integrate such a canopy layer turbulence model with the mesoscale meteorology model. Two approaches may be possible. The easiest is to extract
some meso-scale model data as the city-scale model boundary conditions. The city-scale
model will consider the detailed thermally induced flows at building walls and hill slopes.
The relatively larger scale sea-land breeze is considered in the meso-scale model. This
approach does not benefit the development of the meso-scale model. It may be possible
to use the city scale model to develop better surface parameterization in the meso-scale
model.
The third effort here is also in the development of efficient numerical algorithms and
physical models. A fast and efficient algorithm will permit us to study a longer period,
say an entire year using the combined meso-scale and city-scale models. (This is done in
UDF Computational Science)
Project 2 – Mega-city Energy Efficiency in Hong Kong, Singapore and Shanghai
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Building energy consumption data system by appliance, by activity and by minute in
selected homes in Hong Kong, Singapore and Shanghai. Responsible: KP Cheung, Victor
Li and Yuguo Li
Understanding the impact of urban morphology on energy performance in Hong Kong,
Singapore and Shanghai, and implication to urban planning. Responsible: Stephen Lau
Further development and application of a measurement system for urban heat removal at
a district level. Responsible: Chun-Ho Liu and Melissa Hart
The impact of urban morphology on energy performance in large compact cities– Cities are
altogether built volume, empty spaces, buildings, streets networks, parks, etc. These compose
urban forms. A city presents different urban forms, and so do different cities. All these elements
interact with the micro-climate and influence the energy consumption of buildings and
transportation. In order to assess to which extent the morphological parameters can influence
energy consumption, we first have to characterize urban morphologies by means of a set of
indicators such as built density, floor area ratio, porosity, sinuosity, occlusivity, etc. These
morphological parameters strongly influence energy consumption; therefore, it is possible to
draw conclusions as to which parameters are relevant when it comes to designing an energy
efficient city.
We choose to study Hong Kong and Shanghai (and perhaps Singapore). The proposal focuses on
the relationships between city morphology, density and energy efficiency in high-density cities.
These different forms of density have a strong impact on energy needs. Our data will be
compared to the literature data for other US and European cities. The smart meter measurement
system will be used.
Efficient removal of heat in a high-rise compact city – The urban canopy layer consists of
buildings by street networks, parks and other open spaces, and it can be can be more than 100 m
deep on average in Hong Kong. Human activities, including traffic within the urban canopy layer,
release not only airborne contaminants but also heat. To understand and improve removal
mechanisms of heat from the urban canopy layer, we need to analyze the heat sources/sinks
within it and surface fluxes. Such analysis will be obtained by simple analytical physical models,
urban field measurement, satellite remote sensing (data from providers only), and meso-scale and
city-scale coupling wind flow models.
In addition, we have an existing project with International Energy Agency Annex 53 project on
energy consumption in buildings. More than 10 case studies are being carried out in China,
Japan, US and major European countries. Our contribution will be a new human behavior model
integrated into the existing building energy consumption analysis software Energy Plus. Such a
model will be used to analyze the impact of the urban morphology. Our measurement in this
ICEE project can become part of the IEA effort.
5. Impact of Research (1/2 page)
Deliverables in two years
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AoE proposal or theme-based proposal on megacity energy efficiency and aero-environment.
One better established interdisciplinary team at HKU on mega-city energy and ventilation.
1 monograph on energy efficiency and aero-environment in mega-cities
Joint GRF, NSFC, 12.5 or 973 proposals
>15 high quality journal publications
Expected impact
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Our work will likely to promote the successful urbanization model of Hong Kong into
mainland China, which will be supported by the Hong Kong Government and major
developers.
A city-scale heat and pollutant transport simulation software with powerful visualization
capabilities to be made available to other users.
A starting point for HKU to undertake city-scale energy efficiency and air environment
analysis for other mega-cities in Asia and in the world, which is not available today.
New urban planning guidelines will be developed in terms of the impact of different
urban morphology parameters.
Our new surface parameterization for urbanization and high-rise compact cities, which is
the first of its kind, will contribute to the international scientific community for
meteorological, environmental & even energy estimate application. Existing surface
parameterizations are mainly designed for low-rise structures or rural open terrain that is
unable to handle the dense cities nowadays.
6. Budget Request (1/2 page) (see the revised budget)
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One workshop on mega-city energy efficiency and ventilation in Hong Kong (HK$300k)
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2 visiting professors (One month each, HK$150k)
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5 academic visits by HKU staff and students (30 k each, total HK$150k)
ICEE
(HK$m)
Major equipment
Meteorological
1.3
Matching from Matching from
Faculty of
ME
Engineering
Temperature Profiler (Kippnen)
Infrared camera
Research personnel
3 post-doctoral fellows
(3 x $0.3m x 3yrs)
Research events
Monographs preparation (1 x
$0.5m)
(symposia, 4 overseas experts
travel+lodging) (requested in
city vent project)
One workshop
Research collaboration
2 visiting professors
5 academic visits (HKU
staff/students to overseas
institutions)
Total
0.6
1.8 of
2.7
0.45
0.45
0.45
0.45
0
0.3
0.15
0.15
HK$4.3
Revised budget
Note: This revised budget is suggested based on the major deliverables of this project. The
monograph must be delivered as a condition of the ICEE award. This budget is also based on the
existing team profile – including two post-docs recruited at Mechanical Engineering using other
funds in the area, 6 Mphil/PhD students under the supervision of CH Liu, 2 PhD students with
Yuguo Li, hence this proposed focused on team building and equipment.
ICEE (HK$m)
Major equipment
Part of the cost of the Meteorological
Temperature Profiler (Kippnen) or infrared camera
subject to debate of the team
Research students
Two MPhil students to Geography, Architecture or other
other departments (0.10 X 2 = 0.2)
Research events
Monographs preparation (1 x $0.4m)
(symposia, 4 overseas experts travel+lodging)
+ workshop if needed. Responsible staff: Yuguo Li and
CH Liu
Research collaboration
0.65
0.20
0.40
6 academic visits (HKU staff/students to overseas
0.15
institutions or overseas visiting us HK$25,000 maxim for
each visit, in principle, one for each participating
department )
HK$1.40
Total