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To mitigate the climate change issue, the Government of the Hong Kong Special Administrative Region (HKSAR) proposed the "Hong Kong Climate Change Plan 2030+" with an ambitious goal of reducing the carbon intensity to 65%–70% below 2005 levels by 2030. To achieve this target, the HKSAR Government has developed two District Cooling Systems (DCS) to promote the use of district energy system, enhancing the overall energy efficiency for cooling purpose. One of the government-owned DCSs is located at the Hong Kong-Zhuhai-Macao Bridge Hong Kong Port (HZMB-HKP), producing a total design cooling capacity of 24.16 MW to passenger clearance building and ancillary buildings there. This paper demonstrates how the DCS at HZMB-HKP could enhance overall energy efficiency for cooling purpose, through proper chiller sequencing control, and reduce CO2 emission significantly. An optimal seasonal chiller operation mode is also suggested to be adopted at the DCS at HZMB-HKP from cost-effectiveness perspective. Practical application: District Cooling Systems are considered as a promising solution to alleviate the climate change issue. An optimized chiller sequencing control strategy of DCS can effectively reduce overall cooling energy consumption, so as to achieve carbon neutrality. This paper outlines a case study on a cost-effective operational control strategy of the DCS at HZMB-HKP. The analysis of both the theoretical and practical sequencing control strategy can be taken as a reference for DCS development in the future. [ABSTRACT FROM AUTHOR]

Compared with photovoltaic (PV) or solar thermal (ST) system alone, the hybrid photovoltaic/thermal (PV/T) system has many advantages such as simultaneous production of electrical and thermal energies, efficient utilization on solar energy, space reduction and so on. However, there is limited data on both the energy and exergy performance comparisons of these three solar systems, especially for annual performance data. This paper aims to present a comparative study on the performances of the PV, ST and PV/T systems by a series of full-day experiments. Energy and exergy performances of these three solar utilization systems were all calculated and analyzed. Moreover, two typical evaluation methods, i.e. semi-empirical system efficiency model method and input–output method, were also used for evaluating the performances of these systems. Finally, based on the input–output method, the annual performances of the PV, ST and PV/T systems under typical meteorological conditions of Hong Kong region were predicted. The results show that the ST system has the highest total energy gain and energy efficiency and the PV system has the highest total exergy gain and exergy efficiency of these three systems. However, by a comprehensive consideration on the energy and exergy performances, the PV/T system has the best overall performance of these three solar systems. [ABSTRACT FROM AUTHOR]

Due to the visibility and controllability features of the latest distribution networks, there are potentials to model customer loads through a component-based approach more accurately. The electricity markets started in recent years enable trading and exchanges of electricity among traditional power stations and prosumers. It provides a possibility to improve the optimality of classical volt-var optimization (VVO) schemes. In this paper, a tri-level bottom-up load model and a market-based volt-var optimization (mVVO) model are proposed. The energy-to-voltage (ETV) parameter is proposed in our load model as a substitute for the widely used load-to-voltage (LTV) parameter to reflect long-term load characteristics. The mVVO model using ETV parameters aims to combine the optimal voltage regulation strategies and electricity purchase strategies from wholesale and retail markets for maximum cost saving. The case studies based on real load data of Hong Kong show that by coordinating the voltage regulation methods with market behaviors, utilities can reach a higher level of cost saving, in addition to energy saving. [ABSTRACT FROM AUTHOR]

In this paper, we estimate the energy efficiency of educational buildings with the case study of buildings in City University of Hong Kong by constructing an energy demand stochastic frontier model. The model is estimated by using the university statistical data from 2011 to 2015. For the consistent frequency of data among the variables, we have adopted the quadratic-match sum method to convert annual university report data into a monthly dataset. Our result shows the average energy efficiency is 0.87, implying that 13% of total energy consumption can be saved. We then calculate how much of the energy saving potential has been achieved by constructing the performance score, which increases from 0.08 to 0.17. It implies that the campus performs more efficiently in saving energy over time. We further develop econometric decomposition analysis based on the energy demand frontier model to identify the factors affecting energy consumption. It suggests that research activities account for a large share of overall energy consumption. Analysis on energy end-use shows university should improve efficiency in lab instrument as it is least efficient among the four usages. We expect this paper can provide the fundamental and methodological guideline for university-scale energy efficiency estimation. • Estimating energy efficiency of educational buildings needs to consider the composition of research related factors. • Energy efficiency of campus building presents increasing tendency with seasonal cycle over time. • Research related variables affect significantly on energy efficiency of educational buildings. • Energy use in lab instrument needs to be effectively managed to save energy. [ABSTRACT FROM AUTHOR]

• Automatic MiC envelopes and layout generation by a novel SSG-MOO method. • Multi-objective optimization formulation for passive MiC design. • A pilot MiC study in Hong Kong produced 5 selected Pareto optima out of 625. • Up to 0.42% energy savings and 9.71% spatial daylight autonomy improvement against the baseline. • A multi-level analysis of results and design strategies for practitioners. Modular-integrated Construction (MiC) is an emerging construction technique promoted in the building sector for high productivity and low waste emission in the construction phase; yet, the standardized modules also bring new challenges, such as balancing passive energy efficiency and spatial daylight autonomy, to the operational phase. This paper proposes a Symmetric Skeleton Grammar-based Multi-Objective Optimization (SSG-MOO) method to formulate parametric MiC envelopes and detailed layout, with the two objective functions being energy efficiency and interior daylight performance in the operational phase. Pareto optima of the SSG-MOO, computed by the Non-dominated Sorting Genetic Algorithm II, are generally verified and analyzed in three levels, i.e., MOO's solution space, SSG layout, and MiC design parameters. A case study of MiC residential building in Hong Kong demonstrated the SSG-MOO method through five new passive MiC designs (i.e., spatial reorganization of three architectural modules, and parameter tuning of the envelops and corridors), achieving up to 0.42% energy savings and 9.71% spatial daylight autonomy improvement compared to the baseline design. The contribution of this paper is two-fold, including a novel and sound SSG-MOO formulation for parametric MiC designs, and offering time-efficient and evidence-based design tactics for MiC designers and industrial practitioners to push boundaries of MiC. [ABSTRACT FROM AUTHOR]

Energy consumption is an important indicator for measuring economic development and is closely related to the atmospheric environment. As a demonstration zone for China's high-quality development, the Guangdong–Hong Kong–Macao Greater Bay Area imposes higher requirements on ecological environment and sustainable development. Therefore, accurate data on energy consumption is crucial for high-quality green development. However, the statistical data on local energy consumption in China is insufficient, and the lack of data is severe, which hinders the analysis of energy consumption at the metropolitan level and the precise implementation of energy policies. Nighttime light data have been widely used in the inversion of energy consumption, but they can only reflect socio-economic activities at night with certain limitations. In this study, a random forest model was developed to estimate metropolitan-level energy consumption in the Guangdong–Hong Kong–Macao Greater Bay Area from 2000 to 2020 based on nighttime light data, population data, and urban impervious surface data. The estimation results show that our model shows good performance with an R2 greater than 0.9783 and MAPE less than 9%. A long time series dataset from 2000 to 2020 on energy consumption distribution at a resolution of 500 m in the Guangdong–Hong Kong–Macao Greater Bay Area was built using our model with a top-down weight allocation method. The spatial and temporal dynamics of energy consumption in the Greater Bay Area were assessed at both the metropolitan and grid levels. The results show a significant increase in energy consumption in the Greater Bay Area with a clear clustering, and approximately 90% of energy consumption is concentrated in 22% of the area. This study established an energy consumption estimation model that comprehensively considers population, urban distribution, and nighttime light data, which effectively solves the problem of missing statistical data and accurately reflects the spatial distribution of energy consumption of the whole Bay Area. This study provides a reference for spatial pattern analysis and refined urban management and energy allocation for regions lacking statistical data on energy consumption. [ABSTRACT FROM AUTHOR]

Buildings are responsible for about 92% of the total energy end-use in Hong Kong, of which above 70% is from the commercial sector. Most of the buildings in Hong Kong are high-rise, and approximately 15% of the total building stock is commercial buildings. Despite the considerable improvement in the understanding of the life cycle energy use of office buildings, there is still a lack of research into the life cycle energy demand of high-rise office buildings. Such knowledge is however essential for facilitating building energy conservation in the high-rise urban environment. The aim of this paper is to investigate the life cycle energy use of high-rise office buildings. The research was carried out through a critical literature review and case studies of ten real-life high-rise office buildings in Hong Kong. Results show that the life cycle energy consumption is 51.78–73.64 GJ/m 2 over the 50-year study period. Building operation consumes 78–89% and the rest (i.e. 11–22%) is taken by the embodied energy. Despite the distinction in terms of the amount of embodied energy between high-rise buildings and low-rise counterparts, no clear correlation is found between building height and embodied energy intensity. Moreover, energy use for material manufacturing and transport should be prioritised in reducing the embodied energy, of which the transport energy needs to be taken into extra consideration for the case of Hong Kong. The findings should inform construction industry participants of the significant potential in reducing the embodied energy of high-rise office buildings. The paper profiles the life cycle energy use of high-rise office buildings and should be important for the policy formulation towards the holistic energy conservation in high-rise buildings over their lifespans. [ABSTRACT FROM AUTHOR]

Electricity consumption in cities is steadily increasing. Using a life cycle approach and fuel mix data from power companies’ sustainability reports, this paper analyzes greenhouse gas (GHG) emissions from electricity consumption in Hong Kong. The results show that coal contributed on an average 74.3 percent, liquefied natural gas 25.1 percent, and oil 0.6 percent of the thermal energy consumed for generating electricity in Hong Kong between 2002 and 2015. Besides, Hong Kong imported an average of 7.96 billion kWh per year net electricity from a nuclear power plant in Shenzhen. During this period, GHG emissions from annual electricity consumption ranged between 27.0 and 34.1 million tons (MT) and the emission factor ranged between 702 and 792 g CO 2 -eq/kWh. Hong Kong’s gross domestic product (GDP) increased steadily from USD 176 billion in 2002 to USD 297 billion by 2015. As a result, Hong Kong’s electricity productivity increased from 4.62 to 6.75 USD/kWh while GHG emission from electricity consumption per GDP decreased from 0.153 to 0.104 MT CO 2 -eq/USD billion. Hong Kong’s annual electricity consumption was predicted over the short-term period (2016–2020) and medium term (up to year 2030). Electricity consumption is likely to increase to 44.63 billion kWh by 2030 while GHG emissions from electricity consumption would increase to 33.92 MT of CO 2 -eq. The implications are discussed at the end of the paper. [ABSTRACT FROM AUTHOR]

The economic structure of a city evolves as the city develops, resulting in a change in energy consumption. This paper presents a historical review of Hong Kong's economic development and energy consumption from 1970 to 2015. Based on the official data from the Hong Kong government, it was found that Hong Kong's gross domestic product increased from HKD 208 billion in 1970 to HKD 2398 billion in 2015 in which the contribution from the manufacturing sector peaked in 1985. Energy consumption increased by 9.3 times from 140.2 PJ in 1970 (mostly oil products) to 1298.2 PJ (including oil products, natural gas, coal, and imported electricity) in 2015. The greenhouse gas (GHG) emissions due to energy consumption were determined based on emission factors for different fuels. Results show that GHG emissions increased from 10.7 million tons (Mt) of CO2-equivalent in 1970 to 99.1 Mt of CO2-equivalent in 2015. [ABSTRACT FROM AUTHOR]

A comparison study on using air-cooled and water-cooled conventional and oil-free chillers in hospitals in Hong Kong is reported. The study commenced with a comprehensive literature review to reaffirm the effectiveness of recommended precaution measures for containing the risk of Legionnaires’ disease (LD) associated with using cooling towers. Numerical performance models for oil-free chillers established for use in the study are presented. Based on recorded cooling demands of two existing hospitals, the life-cycle energy consumption and cost of system options involving different combinations of heat rejection method and chiller type were evaluated, compared and discussed. The results show that water-cooled air-conditioning systems with conventional chillers and cooling towers are still more energy efficient than air-cooled systems with oil-free chillers. Water-cooled oil-free chillers may become an economically viable choice when their price is lowered in future. Pilot installation is recommendable, as it would allow the reliability and maintainability of the new oil-free chillers to be ascertained.Practical applications: Findings of the literature review reaffirmed the effectiveness of measures recommended in contemporary guidelines for LD prevention, which would ease the mind of owners, designers and operation and maintenance personnel in regard of using cooling towers in hospitals. The numerical models for oil-free chillers presented in the paper are useful for evaluation of the energy consumption of this new type of chiller and for comparison with other types of chillers. The study approach described in the paper, including the energy consumption prediction and life-cycle cost evaluation methods, provides a useful framework for similar studies. [ABSTRACT FROM PUBLISHER]

In this paper, we study the recent energy use intensity (EUI) in kWh/m2/year of Hong Kong's secondary schools. We found a 22% increase of EUI from, 2003 (86 kWh/m2/year) to 2017 (105 kWh/m2/year) approximately. It may be due to the increase in the number of air-conditioned classrooms. We then use a novel two-stage regression-based approach to analyse the most important set of statistically significant energy performance factors. Then, the energy use intensity (EUI) is normalized with these energy performance factors to find the benchmarking scores used to assess whether the electricity tariff affects schools' energy efficiency. In the first stage of the approach, we first conduct three methods of fitting regression models, backward, forward, and stepwise (OLS), to find a set of normalized factors and construct the benchmarking model. The first stage provides the normalized EUI range, approximately between 50 and 163 kWh/m2/year. In the second stage, if better goodness of fit is desired in the second stage, convex nonparametric least squares (CNLS) regression analyses are employed with the same set of normalized factors. This two-stage regression-based approach is called the OLS-CNLS approach. Using simple EUI (kWh/m2/year) results, we find that high tariff schools' energy efficiency is better than low tariff schools. However, the benchmarking scores (normalized EUIs) of the OLS-CNLS approach show that the null hypothesis cannot be rejected. The energy efficiency of high tariff schools is not significantly better than that of low tariff schools. It implies that the tariff level is not a crucial factor associated with secondary schools' energy efficiency in Hong Kong. As the OLS-CNLS approach allows us to take all the significant energy performance factors into consideration to address the electricity tariff concern, the funding/budget policies probably motivate the school management to look for better EUI. • HK secondary school kWh/m2/yr increases to 105 in 2017 from 85 in 2002. • OLS-CNLS are proposed for developing benchmarking models. • OLS-CNLS is an enhanced regression-based method comparing with CNLS. • Benchmarking results show the insignificance of electricity tariff to EUI. [ABSTRACT FROM AUTHOR]

This paper investigates the pump efficiency of existing water supply systems in high-rise buildings in Hong Kong and provides economic justification for pump replacement by comparing the long-term energy cost savings to the initial installation costs. Energy consumptions of water supply pumps were measured with the pump efficiencies determined from the water consumptions of 20 water supply systems in buildings. The study results indicate that for typical pump motor ratings that range from 1 to 40 kW in a high-rise water system, with new pump efficiencies and annual pump efficiency drops that range from 0.68 to 0.74 and 0.012 to 0.028 respectively, a shorter replacement period can be justified on energy cost grounds for larger pumps with greater annual efficiency drops.Practical application: This paper exhibits numerical solutions of replacement period justified on energy cost grounds for typical pump motor ratings that range from 1 to 40 kW in a high-rise water system, with new pump efficiencies and annual pump efficiency drops that range from 0.68 to 0.74 and 0.012 to 0.028, respectively. [ABSTRACT FROM AUTHOR]

Energy consumption of lift systems is one key issue in modern high-rise buildings, drawing property owners' attention and accounting for 6% of total electricity consumption by end-use in Hong Kong. A Benchmarking Energy Performance Indicator (BEPI), , measured in J.kg−1.m−1 and proposed by the first author of this paper for lift installations is mentioned in the Technical Guidelines of the Building Energy Code , as one emerging good engineering practice. BEPI is a fair parameter for comparing energy performance of lifts irrespective of their brand, model, travel, speed, capacity and control. It considers energy performance due to both the motor drive efficiency and traffic control intelligence. However, one main obstacle to make it statutory is the lacking of a generic monitor able to retrieve three sets of real time data (normally unavailable on an existing lift) to compute the BEPI, namely energy consumption, instantaneous car load and traveling distance, and to collect ample data statistically reliable enough to determine an acceptable threshold value. This paper describes the development of a proof-of-concept prototype BEPI monitor by giving full technical details on the rationale and history of development, the hardware components, software framework, and updated numerical results of one implementation inside the headquarters of Electrical & Mechanical Services Department (EMSD) of HKSAR. Experiences in installing and calibrating those external sensors that make the whole system non-disturbing to normal lift operation, as well as the procedures in computing the BEPI, are discussed in greater details. It has been shown that the BEPI is traffic dependent but the weekly average of it is relatively stable, confirming it may be robust enough for benchmarking purpose. The solution described in this paper may help roll out the monitoring of BEPI for all lifts inside and outside Hong Kong. [ABSTRACT FROM AUTHOR]

The causal relationship between energy consumption and gross domestic product in Hong Kong from 1992 to 2015 is investigated in this study. Different from the previous studies focusing on the causal relationship between total energy consumption and total gross domestic product per capita, this study further investigates the causal relationship from sectoral perspective, including residential, commercial, industrial and transportation sectors. For each sector, the time series data of sectoral energy consumption and sectoral per capita value added are collected. To conduct the Granger causality test, the unit root test is first applied to analyse the stationarity of time series. The cointegration test is then employed to examine whether causal relationship exists in long-term. Finally, based on the aforementioned tests, both vector error correction model and vector autoregression model can be selected to determine the Granger causality between time series. It is interesting to find that the sectoral energy consumption and corresponding sectoral per capita value-added exhibit quite different causal relationships. For both residential sector and commercial sectors, a unidirectional causal relationship is found running from the sectoral per capita value added to sectoral energy consumption. Oppositely, for industrial sector and transportation sector, a unidirectional causal relationship is found running from sectoral energy consumption to sectoral per capita value added. Regarding the Granger causality test results, the indicative suggestions on energy conservation policies, energy efficiency policies and greenhouse gas emission reduction policies are discussed based on the background of Hong Kong's economic structure and fuel types. [ABSTRACT FROM AUTHOR]

Purpose – This study aims to develop a prototype for measuring the carbon emissions arising from the utilization of electrical appliances in a typical Hong Kong family in Kowloon District. Design/methodology/approach – To estimate carbon emission coefficients of energy consumption, the US building energy database books are referred to, which include home appliances’ energy end-use expenditure splits and energy end-use carbon splits. Due to differences in climate, geography and culture, the estimation equations are refined with assumptions and constraints based on the context of Hong Kong. Findings – By calculating the amount of carbon emissions from different electrical appliances, including space cooling, water heating, lighting, refrigeration, wet cleaning and cooking, it is estimated that the carbon emissions from major home electrical appliances in Hong Kong’s residential building sector is 1,805,397 metric tons. According to the findings of this study, by adopting the energy-saving guidelines for space coolers, refrigerators, water heaters and washing machines, carbon emissions in Hong Kong’s residential building sector can be reduced by 155,443 metric tons, or by 8.6 per cent of the current emission. Research limitations/implications – Due to limited resources, the case study does not cover residential units in other districts of Hong Kong, including the Hong Kong Island and the New Territories. In addition, relevant institutional and financing costs of implementing the proposed practices such as increasing the air-conditioning temperature and upgrading the lighting system should be further considered. Future research will be extended to the wider territory of Hong Kong and to obtain more cases for analysis. Originality/value – This paper provides a microscopic perspective on investigating the carbon emissions associated with energy consumption from major home electrical appliances in Hong Kong’s residential buildings. By unveiling the interaction between energy consumption and carbon emission, we formulate measures and strategies for implementing a cost reduction and carbon saving scheme of Hong Kong’s residential buildings, which is in line with government’s guidelines on green buildings. [ABSTRACT FROM AUTHOR]

Vibration characterization in moving franchised buses has been performed. Considering the frequency spectrum of vertical acceleration, two distinct vibration peaks at 2.2 and 14 Hz were observed. The root-mean-square acceleration peak values were 5.59×10−6and 1.95×10−6g2/Hz, where g is the acceleration due to gravity. Based on the experimental results of vibration frequency characteristics, a conventional piezoelectric cantilever energy harvester with natural frequency tuned at 14 Hz was constructed. This paper presents the application of piezoelectric energy harvester to obtain the low-grade waste vibration energy from Hong Kong franchised buses. Ten different bus routes were selected for the energy harvesting. On average, statistical data showed that for buses traveling from one terminus to another, by using the cantilever piezoelectric energy harvesting technique, the feasible power generated from bus vibration was around 90 μW. [ABSTRACT FROM AUTHOR]

This study is to assess developers' market readiness to green construction including their ideas on green construction, their understanding of current green building policies, their awareness and familiarity with green building and related industries, and the barriers they are facing for implementing green building projects. By eleven face-to-face semi-structured interviews with locally-based developers, the study finds that the Green Building Market in Hong Kong is basically ready in technology level. However, the motivation for green development is confined to commercial buildings for lease. Legislation is agreed by developers as an effective motivator to green building development. An effective mechanism to provide incentives for market players to adopt green voluntarily is explored in this paper. Expedited permits and density bonus are thought to be major incentives. [ABSTRACT FROM AUTHOR]

Abstract: Environmental sustainability is a topic of increasing concern among scholars, city planners, engineers and policymakers. Electricity consumption constitutes about two-thirds of a city''s carbon emissions. In high-density Hong Kong, the building sector accounts for 89% of total electricity consumption, with commercial buildings alone accounting for 67% of the total. This paper reports the results of an in-depth case study examining how Langham Place Hotel Mongkok Hong Kong (LPHKG) has successfully reduced its CO2 emissions by implementing a range of sustainability design strategies. LPHKG is a five-star hotel situated in Mongkok – one of the most densely populated districts in the world, with an estimated 130,000 people per square kilometre. In particular, the paper discusses how the hotel, in its efforts to achieve net zero-energy, has made wise use of technologies to maximise energy consumption efficiency in its existing lighting and air-conditioning systems and in the mechanical devices of the building itself. The overall implication of LPHKG''s efforts is that, although the initial investment required for such technologies is usually large, the resulting long-term cost savings can be significant. [Copyright &y& Elsevier]

Climate change may seriously affect the energy consumption of buildings by influencing their air conditioning loads, especially the ventilation loads which vary directly with the local weather conditions. Research on how the ventilation load responds to climate change is of great significance, especially in coastline subtropical regions like Hong Kong. This paper investigated the impacts of climate change on buildings' ventilation load and building energy use in Hong Kong with the hourly meteorological data from 1950 to 2007. Results have been well validated by the simulation of a typical local hotel building during this period. The results show that climate warming increases both sensible and latent parts of the cooling ventilation load. The latent part, which occupies ∼80% of the total ventilation load, increases at a higher rate, about twice of that of the sensible one. Furthermore, it is found that the urban heat island (UHI) effect causes a much higher growth rate of the ventilation load at night, which is about three times compared with that in the daytime. The latent part of the cooling ventilation load at night, which is found to be the most sensitive component to the climate change, plays a most significant role in the energy consumption increase. The possible measures were thus suggested to avoid negative changes of the ventilation load. Besides, reducing the UHI effect by better urban planning also significantly benefits the local buildings with a long air-conditioning operation time. [ABSTRACT FROM AUTHOR]

Abstract: The intermittent property of a photovoltaic (PV) system requires supplementary energy such as the utility grid or batteries to meet load demand. However, when large scale PV systems are connected to the utility grid, they might affect the grid stability if the overall system is not properly designed. Hence, an accurate model for forecasting the PV system output would be useful in enhancing the system stability and reliability. The dynamic modelling of PV systems is thus crucial to the rapidly developing technologies and integrated sources in the smart grid application. This paper presents different approaches to model PV systems and identifies their pros and cons in modelling. The paper then explains the importance of a dynamic model, followed by the methodology in building up such a dynamic model. A three-vertex representation of a nearby building casting a shadow onto the PV array is also proposed as a novel approach in shadow analysis. The implementation of the dynamic model for PV systems was demonstrated in a case study in Hong Kong. [Copyright &y& Elsevier]

Abstract: The construction of buildings has a very important impact on the environment, and the process of manufacturing and transporting of building materials, and installing and constructing of buildings consumes great energy and emits large quantity of greenhouse gas (GHG). The present paper defines four sources of GHG emissions in building construction, which are: manufacture and transportation of building materials; energy consumption of construction equipment; energy consumption for processing resources; and disposal of construction waste, and then establishes the calculation method of GHG emissions. This paper presents a case study of GHG emissions in building construction in Hong Kong. The results show that 82–87% of the total GHG emissions are from the embodied GHG emissions of building materials, 6–8% are from the transportation of building materials, and 6–9% are due to the energy consumption of construction equipment. The results also indicate that embodied GHG emissions of concrete and reinforced steel account for 94–95% of those of all building materials, and thus the use of recycled building materials, especially reinforced steel, would decrease the GHG emissions by a considerable amount. [Copyright &y& Elsevier]

Building occupants can enjoy a healthy and comfortable indoor environment and use less cooling energy if sufficient natural ventilation is available in their dwellings. Assessing the natural ventilation performance of building designs requires modelling of the external wind environment, the natural ventilation rate and the thermal environment in individual rooms, and reduction in the use of air-conditioning equipment. These are complicated processes. A practical approach for assessing the natural ventilation performance of residential building designs is presented in this paper. The method includes prediction of wind pressures upon window openings in the building façade by computational fluid dynamics simulation, natural ventilation rate prediction using a flow network simulation model, and indoor free-float temperature and air-conditioning energy-use predictions using a building heat transfer and an airconditioner performance simulation programme. Additionally, the method includes a simplified statistical approach to deal with the random variations in the speed and direction of the wind. This method has been applied to assess the natural ventilation performance of a standard public housing block design widely used in Hong Kong, taking into account when the wind wing walls were incorporated into the building façade and when the separation distances among the building blocks were widened by 25% and 50%. [ABSTRACT FROM AUTHOR]

Purpose ? The purpose of this paper is to address the issue of electrical energy consumption through case studies of a small sample of buildings on a university campus in Hong Kong. Design/methodology/approach ? Data were used to produce deterministic time-series models and so aid analysis of the climatic effects on energy consumption. Semi-structured interviews were employed to supplement the data. Both technical factors impacting on energy consumption and behavioural considerations are addressed. Findings ? Conclusions demonstrate the impact of functions housed in the buildings, their intensity of occupation, and that the increased consumption to combat high temperatures and relative humidity during the summer can be mitigated by improved control systems and increased awareness of users to induce less energy consuming behaviour. Research limitations/implications ? Limitations of the empirical study are due to the rather short run of data which were available for the case study buildings and the particular functions of the buildings studied. More detailed data of energy consumption is desirable. Complimentary studies should concern different building functional types and other locations, involving varying climatic conditions. Practical implications ? The findings demonstrate the value of time series models of, and the impacts of the main variables on energy consumption and so, should inform design decisions regarding life cycle costing of buildings and foster energy conservation. Originality/value ? This paper has provided empirical modelling of energy uses in the case study buildings and thereby demonstrated the impacts on energy uses of certain major variables to inform design for energy conservation. [ABSTRACT FROM AUTHOR]

The feasibility of using thermal performance lines to assess the efficiency of using energy in air-conditioned commercial buildings in Hong Kong is being explored. The paper describes a regression study aimed at identifying a suitable climatic variable that would yield linear thermal performance lines for commercial buildings in Hong Kong. The study was based on the monthly electricity consumption of 26 existing office/commercial buildings obtained from a recent survey. Candidate weather parameters considered include monthly mean outdoor temperature, outdoor air moisture content and global solar radiation, and their square and product terms. The regression analysis shows that the square of monthly mean outdoor temperature would be the most appropriate climatic variable. Explanations are also given as to why moisture content and global solar radiation were considered less appropriate, notwithstanding that in Hong Kong, the humidity is high for most of the time in the year and the cooling load due to solar heat gain is a significant component of the design cooling load of air-conditioned buildings. [ABSTRACT FROM AUTHOR]

In the Hong Kong Building Environmental Assessment Method (HK-BEAM) for air-conditioned office premises, energy use for air-conditioning constitutes one major item of assessment. The current assessment method for existing offices is based on computer simulation predictions. Following a recent review of the HK-BEAM scheme, simplified models have been developed for use in the assessment as an alternative to the detailed simulation method. These models are multiple linear regression models relating the annual electricity use for air-conditioning, and the maximum electricity demand, in an office building to the key characteristics of the building envelope and the air-conditioning system. Use of these models can reduce the effort required for data collection and input, and will allow the assessors to more quickly complete an assessment. In addition, additional parametric studies can be performed within much less time, which will help assessors in formulating advice to developers/designers on measures that will lead to improved energy performance and thus higher credits. This paper summarizes the review findings and describes the approach taken in the establishment of the regression models. Comparison of predictions by the detailed computer simulation method and the alternative method showed that the latter could provide estimates close enough to the simulation predictions for the purpose of assessing the credits to be awarded to a building for its energy performance. [ABSTRACT FROM AUTHOR]

Heating, ventilation, and air conditioning (HVAC) systems are the second largest energy consumers on cruise ships after the propulsion system. As a kind of HVAC system, active chilled beam (ACB) systems have been widely used for cabin service due to their performance of energy efficiency and good thermal comfort. However, conventional control strategies for ships' ACB systems are not intelligent enough and cannot balance energy consumption and cabin comfort during the voyages of ships. This study developed an optimal control strategy for cabins' ACB systems. First, a simulation environment considering dynamic conditions is established in TRNSYS. Second, an artificial neural network model is utilized to predict the energy consumption of the ACB system, while the predicted percentage dissatisfied is adopted to represent cabins' thermal discomfort. Third, an improved multi-objective salp swarm algorithm is proposed to dynamically minimize both energy consumption and thermal discomfort. A TRNSYS–MATLAB co-simulation testbed is established to simulate the cabins served by an ACB system on a small cruise ship navigating from Hong Kong to Shanghai for validation tests and a comparison study. Compared to the conventional strategies, the proposed strategy can achieve a maximum energy savings of 12% while maintaining a predicted mean vote index less than 0.5, meeting the comfort requirements set by ASHRAE. [ABSTRACT FROM AUTHOR]

Despite an increased awareness about energy conservation in the past decade, the energy consumed for water heating has increased by 7% from 2008 (17%) to 2018 (24%) in Hong Kong. A literature review on existing energy-saving technologies during showering showed that occupants' behavior significantly impacted energy consumption. However, the exact relationship between them was not yet fully understood. Therefore, this study developed a mathematical energy consumption model to investigate the relationship between occupants' behavior and energy consumption during showering. This relationship identified an effective energy-saving strategy in the shower without scarifying occupants' thermal comfort. The main variables that influence energy consumption and thermal comfort in bathrooms namely air temperature, water temperature, ventilation rate, and water flow rate, were considered. It was found that among them, water flow rate and ventilation rate are the most and least influential variables, respectively, in energy saving. Therefore, the ventilation rate was suggested to be at least 0.03 kg·s−1, and the water flow rate was meant to be lower than 0.15 kg·s−1 (based on related requirements). These findings could help residential occupants and facility managers determine the optimal showering settings for thermal comfort, energy consumption, and environmental effects. [ABSTRACT FROM AUTHOR]

Inter-building effect (IBE), which refers to the shading effect from surrounding buildings, plays an important role in building energy use in high-density cities. However, it is customary to neglect the IBE during energy simulation. Four issues are observed on previous research: 1) it has been controversial whether the IBE significantly affects energy consumption, 2) most studies used low-rise or medium-rise residential buildings as references, 3) most studies were conducted with hypothesised buildings, 4) most studies did not consider window blinds effect on IBE. These issues inhibit the theoretical understanding of high-rise building energy performance in cities and jeopardise the achievement of accurate simulation. This paper thus aims to investigate the IBE on the energy use of high-rise office buildings in Hong Kong as a typical high-density city. The IBE of ten selected real-life office buildings in their real-life communities was analysed. Four scenarios were compared, namely, simulation of building with both IBE and window blinds (base case), simulation of building with IBE but no window blinds, simulation of isolated building with window blinds, and simulation of isolated building without window blinds. The results show that the IBE influences the total energy use by up to 13.1%. Compared with the base case, heating, ventilation, air-conditioning (HVAC) and the lighting consumption deviation with different scenarios fluctuated largely, ranging from −11.8% to 18.8% in HVAC consumption, and from 0.1% to −27.6% in lighting consumption. An offset effect was found between the decreased lighting consumption and the increased HVAC consumption. From the floor-level analysis, with real communities, lighting energy use decreased with height among all the buildings generally. A multi-variant regression model was established to evaluate the relationship between IBE variables and building energy deviation caused by IBE. In addition, the results conclude that shading blinds cannot be overlooked when examining IBE on building energy use. These findings reveal the importance of considering IBE on building energy consumption in high-density contexts on a case-by-case basis. [ABSTRACT FROM AUTHOR]

Climate change has always been an enormous threat to our living environments. In Hong Kong, energy consumed in buildings is a significant contributor to greenhouse gas (GHG) emissions. It is estimated that energy use in residential and commercial buildings alone accounts for more than 60 per cent of GHG emitted citywide. Hence, the building sector presents a strong opportunity to make substantial progress in reducing Hong Kong's energy demand and carbon emissions. For the past few years, the HKSAR Government has been spearheading the promotion of green buildings in Hong Kong and has continuously strived to place their efforts on various initiatives to achieve higher energy efficiency and to promote low carbon living. The government provides continuous support and works together with the Hong Kong Green Building Council (HKGBC) and various stakeholders to improve the energy efficiency in the building industry through numerous initiatives. The contributions of government and the private sector are equally important in combating climate change. The government and HKGBC have conducted strategic schemes with clear objectives and achievable targets. A practical support programme, 'ACT-Shop', is therefore available to promote knowledge-based practice on energy saving. Professionals are invited to help investigate the data of each case, develop improvement options and verity the savings. This paper aims to further discuss the concerted effort of the government and the HKGBC in combating climate change. [ABSTRACT FROM AUTHOR]

• A POE-integrated simulation method is proposed to address energy occupant behavior. • Opening windows and operating AC were found to co-exist which affects simulation accuracy. • The new method improves energy simulation accuracy by 14% for domestic areas. • The method improves energy simulation accuracy by 16% for total building areas. Occupant behavior plays a critical role in building energy consumption, particularly in residential buildings. However, occupant behavior is complicated and varies significantly from case to case. Also, energy modeling of high-rise buildings is far less explored than that of low- or medium-rise buildings. This paper aims to improve accuracy in building energy simulation by utilizing Post Occupancy Evaluation (POE) data to calibrate energy model. Drawing on a review of the literature of occupant behavior and building energy modeling, the paper provides a calibration method of integrating POE data into an energy model, which is demonstrated using a real-life typical 40-storey residential building in Hong Kong. The developed method addresses seven updated input parameters, namely, schedule, devices, air-conditioners, windows, lights, domestic hot water, and cooking. By comparing the two energy modeling processes, i.e. with and without POE input, and their resultant estimated energy consumption, the paper quantifies the impact of occupant behavior on building energy consumption. Annual metered data together with energy bills obtained from the POE were utilized to validate the models. The results show that the use of the developed POE-integrated method helped to improve accuracy in energy consumption prediction by 14% for the total building floor area and by 16% for the total residential area. From examining the impacts of the seven input parameters, the paper reveals the key energy use sensitive occupant behaviors within high-rise residential buildings in Hong Kong. These include: the number of residents in each unit; adoption of window type and split type of air-conditioners; window and air condition operation modes; cooking time on weekdays and weekends; and time spent on hot water showering. The developed method can assist building designers and services engineers to estimate building energy use more accurately and provides a scenario analysis tool for clients and facility managers to develop effective energy conservation strategies. [ABSTRACT FROM AUTHOR]

To achieve a more comfortable indoor environment while still retaining low energy consumption level is an exciting challenge for designers and owners of buildings. In this paper, a silica-aerogel filled super-insulating glazing system was proposed. A numerical study was conducted to analyze the energy performance and visual performance of the proposed glazing system. Two popular building simulation programs namely EnergyPlus and Radiance were applied in the numerical study. In the study of the energy performance, three control strategies (space temperature control, operative temperature control and PMV control) were applied to simulate the occupant’s control behavior toward the air-conditioning system in reality. The result indicated that compared with conventional single clear glazing, the silica aerogel glazing could retain a 4% longer thermally comfort period, while the energy consumption of HVAC system was reduced by 4–7%. The performance of the silica aerogel glazing was almost equal to that of the state-of-art low-e glazing. It is also concluded that as the occupant’s request on thermal comfort got stricter, the performance of the silica aerogel glazing would became better. In the visual comfort point of view, it can be concluded that the glare effect and near-window bright zone could be reduced significantly while indoor illumination level still met the requirement. [ABSTRACT FROM AUTHOR]

This study applied cognitive diagnostic models to assess students’ learning progressions in energy. A Q-matrix (i.e., an item attribute alignment table) was proposed based on existing literature about learning progressions of energy in the physical science domain and the Trends in International Mathematics and Science Study (TIMSS) assessment framework. The Q-matrix was validated by expert review and real data analysis. Then, the deterministic inputs, noisy ‘and’ gate (DINA) model with hierarchical relations was applied to data from three jurisdictions that had stable, defined science curricula (i.e., Australia, Hong Kong, and Ontario). The results suggested that the hypothesized learning progression was consistent with the observed progression in understanding the energy concept. We also found similarities in students’ attribute mastery across the three jurisdictions. In addition, we examined the instructional sensitivity of the selected item. We discuss several curriculum-related issues and student misconceptions that may affect students’ learning progressions and mastery patterns in different regions of the world. [ABSTRACT FROM AUTHOR]

Improving the energy performance of existing building refurbishment has been identified as one of the key measures to reduce greenhouse gases (GHGs) emissions and combat climate change. However, little has been done to uncover how human behaviours would affect the selection of refurbishment solutions selection. The problem is particularly obvious for high-rise residential buildings as they are owned and/or occupied by different peoples with idiosyncratic behaviour and preference. In this research, 46 potential methods commonly used for major sustainable building refurbishment in high-rise residential buildings located in cities with sub-tropical climate like Hong Kong were identified through literature review. These sustainable building refurbishment methods are classified under five groups namely energy user pattern, domestic, high-rise building, climate feature and other building characteristics. A questionnaire survey was conducted to examine the feasibility of the identified refurbishment methods based on the perception of owners and occupants. The results show that those methods classified under building services category such as lighting, appliance, ventilation and lift received greater support from owners and occupants. It is interesting to note that owners and occupants did not favour those sustainable refurbishment options which are related to the building envelop when it comes to major building refurbishment. As for the renewable energy refurbishment methods, their acceptability was moderate indicating that there is huge potential for being incorporated into the major building refurbishment. This paper should help improve our understanding on what factors contribute to the satisfaction of owners and occupants of high-rise residential building in a major sustainable refurbishment scheme. [ABSTRACT FROM AUTHOR]

LDAC (liquid desiccant air-conditioning system) is promising for reducing the energy consumption, and improving the indoor air quality. In this paper, the operation performance of LDAC with internally cooled/heated dehumidifier/regenerator was simulated and optimized. The cooling tower and solar collectors were employed as the cooling/heating source. Four nested iteration loops were developed and solved for system modeling. A typical commercial building in Hong Kong was selected as a case study, which air-conditioning load was obtained by Energy-plus. Results show that with the increase of solar collector area, the electricity consumption of AC (air-conditioning systems) system reduced by 11-35% in original system, but only a part of dehumidification demand was handled with liquid desiccant ventilation, which led to a low chiller COP (coefficient of performance). By adding a cooling coil for the solution entering dehumidifier, the electricity saving effectively increased to 22-47%, while the heat demand for regeneration also increased by 17%. So, a heat exchanger between water leaving regenerator and solution leaving dehumidifier was introduced. With the lower thermal requirement (reduced by 20%) and higher solar fraction (increased from 30 to 40%), the saving further increased to 29-49%, and the required collector area obviously reduced by 50-60% for the similar energy saving purpose. [ABSTRACT FROM AUTHOR]

Optimal WT (wind turbine) layout patterns relate in detail to the specific conditions of OWF (offshore wind farm) environments and therefore each is different. This paper presents an investigation into optimal WT layout patterns for three OWF configurations (aligned, staggered, scattered) in HK (Hong Kong) waters. A hypothetical OWF (6930 m × 9072 m) are analysed based on twenty years of wind data (1992-2011). For the aligned and staggered WFs, different WT layout separations are studied. The separations varied between 5.0D and 15.0D along the PWD (prevailing wind direction) and 5.0D to 12.0D in the CWD (crosswind direction), where D is the WT rotor diameter. A range of 25 and 45 WTs are placed in the scattered WF, with their layout optimized using the Multi-Population Genetic Algorithm. WF performance is reported for the best ten layout patterns following studies of many different layouts. Results show for this hypothetical OWF, that the optimal WT separation is 14.5D in the PWD and 11.0D in the CWD for the aligned and staggered cases. Thirty WTs are recommended as the optimum number for the scattered WF. The LCOE (levelized costs of energy) were calculated in HK$ terms 1.474/kWh (aligned), 1.467/kWh (staggered), and 1.290/kWh (scattered). APG (annual energy generation) is determined to be 40.80 × 108 kWh (aligned), 40.42 × 108 kWh (staggered), and 33.98 × 108 kWh (scattered), representing 9.48% (aligned), 9.39% (staggered), and 7.89% (scattered) of the annual electricity consumption for HK in 2012. The approach presented can be regarded as a generic method for WT layout optimization. [ABSTRACT FROM AUTHOR]

Abstract: A city's reliance on energy increases when it is developed. Moreover, the combustion of fossil fuels inevitably generates air pollutants including carbon dioxide, nitrogen oxides, sulfur dioxide, particulate matter, and others. Combining with other anthropogenic air pollutants, visibility in many Asian cities including Hong Kong have deteriorated rapidly in the past decades. This paper explores the relationships between energy use, meteorological factors, and change in visibility in Hong Kong using long-term time-series data. The total use of primary energy increased from 146,700 TJ in 1971 to 1,270,865 TJ in 2011 while the number of hours of reduced visibility increased from 184 h to 1398 h during the same period of time. Bivariate correlations show that poor visibility was significantly associated with energy use and annual mean air temperature. Multiple regression analysis indicates that the burning of aviation gasoline significantly, adversely affect visibility. Results illustrate that the number of clear days in Hong Kong will decrease, in particular due to the increase in air traffic. [Copyright &y& Elsevier]

Abstract: Currently one of the most promising power solutions for remote rural areas and isolated islands which are far away from utility grid is the stand-alone solar photovoltaic (PV) renewable energy system or hybrid solar–wind power system. This paper presents the investigation results of a real remote solar PV project on an island in Hong Kong. The stand-alone PV system, rated at 19.8kWp, is established on a remote island for power generation to local residents. Power on this island was originally supplied by diesel generators and this new solar energy system has significantly reduced fuel costs and alleviated environmental pollution. The on-site entire system’s operating data was collected for one whole year in 2011, and the energy performance of the PV array, inverters, battery bank and the entire PV system were analyzed in terms of daily energy balance, normalized performance parameters and overall system energy utilization ratio. The results from this long term system monitoring and its evaluation enables a detailed inspection of system operating performance with respect to the technical issues, which provides a useful reference for future applications of solar photovoltaics in remote islands. [Copyright &y& Elsevier]

This paper presents a Pareto optimization framework for routing and scheduling dynamic rail transit network services. We first develop an event-based dynamic transit network model that can capture the evolution of passenger demand and service operations with incorporation of passengers' transfers and recirculation of limited number of train vehicles over different service lines. A multi-objective optimizer is then built upon the transit model which seeks jointly the settings of service lines and schedules that could minimize passengers' journey times, transfer rates, and operator's cost. The problem is solved by a cross-entropy method (CEM) which samples potential solutions from statistically tractable distribution models with iterative updates via maximum likelihood. The operational constraints are explicitly incorporated in the solution process which enhances the feasibility of the sampled solutions and hence effectiveness of the computational process compared with other metaheuristics used in the literature. A CEM-based ranking algorithm is further developed for deriving the Pareto-frontiers for the multi-objective transit network routing and scheduling. The proposed framework is applied and tested on the Hong Kong Light Rail Transit (LRT) network using real world scenario data. The results reveal new insights on how the existing operational settings could be improved. The present study contributes to urban transit network service planning with advanced computational techniques. • A dynamic transit network model with passengers' transfer and vehicles' circulation. • A novel cross-entropy solution framework incorporating operational constraints. • A novel solution framework that can derive generic Pareto frontiers with multiple conflicting objectives. • A case study demonstrating the efficiency and practicality from both passengers' and operators' perspectives. [ABSTRACT FROM AUTHOR]

Abstract: The generation of significant amount of emissions from building construction process has led the promotion of controlling emissions as an important strategy for implementing sustainable development principles in the built environment. The emissions incurred during various stages include carbon dioxide, methane, nitrous oxide, sulphur dioxide, carbon monoxide, nitrogen oxide, non methane volatile organic compounds and particulate matter. This paper conducts the life cycle assessment of the air emissions by using a particular case to examine emissions during construction stage. This study examines the emissions sources in each of the six stages and presents an inventory analysis method to measure air emissions to quantify the air emissions during the six life cycle stages for buildings. This method can help evaluating the impacts of implementing a building on the air quality, thus actions can be taken in early stages to reduce the environmental impacts during building life cycle. A case study is presented to demonstrate the practical application of the method with reference to the building practices for all life cycle stages in Hong Kong. [Copyright &y& Elsevier]

Abstract: In Hong Kong, conventional air-conditioning (AC) systems cause a high energy consumption and poor indoor thermal comfort. This paper investigated the AC load profiles of three typical local commercial buildings, i.e. office, hotel and retail, and examined the energy consumption of liquid desiccant cooling system (LDCS) for these buildings. Simulation results showed that the cooling load contributed to more than 98% of total annual load, with high latent load proportion from March to September. The high reheating ratio, i.e. from 60% to 90%, is found to be the main reason for the poor thermal comfort. Therefore, the LDCS which could handle sensible and latent loads separately was proposed. However, the electricity-driven LDCS was found not suitable for local commercial buildings. significant energy saving could be achieved by the solar-assisted LDCS system with thermal storage, when the installation area for solar collectors is larger than the minimum required one, i.e. 9.7m2/(kWm−2) for office and 12.7m2/(kWm−2) for hotel buildings. Energy saving of different system types with different installation areas was also studied. The solar-assisted LDCS shows more energy saving in winter but less in summer. Results and conclusions can be useful for researchers and local engineers. [Copyright &y& Elsevier]

Abstract: Energy consumption by passenger transport in Hong Kong increased rapidly in the past decades and in 2008 it accounted for 19.7% of total energy use. Improving energy efficiency has been widely regarded as an effective way for reducing energy use in the transport sector. However, the expected energy savings from energy efficiency improvement are likely to be discounted due to the existence of rebound effect. This paper employs econometric models to estimate the direct rebound effect for private passenger transport in Hong Kong. We find that the magnitudes of the direct rebound effect are respectively 45% and 35% for 1993–2009 and 2002–2009, which indicates that there was a declining trend in the direct rebound effect for passenger transport over time. It also indicates that the direct rebound effect needs to be taken into consideration in assessing the impact of energy efficiency measures on reducing energy use in Hong Kong. [Copyright &y& Elsevier]

Abstract: The shading-type BIPV claddings can act as power generators as well as external shading devices and insulation panels. There is little available information about the impacts of orientations and inclinations on the combined energy effects of the shading-type BIPV claddings, including the power output of PV modules, the cooling load reduction of windows and concrete walls. It is worth studying the effects of different shading-type BIPV cladding designs on the total energy saving in order to maximize the system’s energy performance. By considering the meteorological conditions in Hong Kong, the energy effect of the shading-type BIPV claddings with different surface azimuth angles, in terms of electricity generation and cooling energy consumption reduction is analyzed in this paper. Based on the investigations, the optimum design of the shading-type BIPV claddings for different orientations can be achieved. [Copyright &y& Elsevier]

Abstract: In metropolitan cities like Hong Kong where land value is high, highrise commercial and residential buildings with “central core” design are developed. The lift lobbies in the buildings are usually located in the centre of the building to free up peripheral areas to provide valuable exterior view. The lift lobbies have no window provisions and electric lighting is switched on for 24h continuously consuming non-renewable energy. Different types of light guides/light pipes have been proven to be capable to transfer daylight into deep floor plan during both clear sky and overcast periods. However, the thickness of light guide requires 3m headroom clearance for installation whilst the headroom of the highrise buildings is usually limited to 2.8m in order to build more storeys. In this research, a remote source lighting system (RSL) is introduced to illuminate the enclosed lift lobbies. The system composed of prismatic light pipe and optic fiber to address the problem of limited headroom. Simulation of the system was carried out and reported in the paper, indicating that this lighting system can solve the energy consumption problem in the lift lobby in terms of renewable energy use and natural lighting application. This research concentrates on highrise residential buildings. [Copyright &y& Elsevier]

Abstract: Greening is a useful mitigation strategy for planners mainly from a visual perspective. For high-density urban living environment such as Hong Kong, urban greening helps cooling the air and providing shade; it also helps lowering building energy consumption by providing a better outdoor boundary condition. Many researchers have also suggested that greening may be employed as a strategy for combating the ill effects of urban Heat Island (UHI). Working towards a set of better greening guidelines for urban planners, the current paper first provides a comprehensive review of planning with urban greening. It then describes parametric studies that have been conducted to investigate the preferred location, amount, and types of vegetation for urban planning. The parametric studies employed the numerical model ENVI-met, verified using field measurements, to simulate 33 cases with different combinations of factors. For benefiting urban activities, ambient air temperatures at the pedestrian level are compared among different greening strategies and building heights. For a city such as Hong Kong, which has a high building-height-to-street-width (H/W) ratio, the present study reveals that roof greening is ineffective for human thermal comfort near the ground. Trees are also suggested to be more effective than grass surfaces in cooling pedestrian areas. The amount of tree planting needed to lower pedestrians level air temperature by around 1°C is approximately 33% of the urban area. The present study allows urban planners to identify more precisely the greening principles, amount and policies necessary for better urban living environment in high-density cities. [Copyright &y& Elsevier]

Abstract: The concern on climate change leads to growing demand for minimization of energy use. As building is one of the largest energy consuming sectors, it is essential to study the impact of climate change on building energy performance. In this regard, building energy simulation software is a useful tool. A set of appropriate typical weather files is one of the key factors towards successful building energy simulation. This paper reports the work of developing a set of weather data files for subtropical Hong Kong, taking into the effect of future climate change. Projected monthly mean climate changes from a selected General Circulation Model for three future periods under two emission scenarios were integrated into an existing typical meteorological year weather file by a morphing method. Through this work, six sets of future weather files for subtropical Hong Kong were produced. A typical office building and a residential flat were modeled using building simulation program EnergyPlus. Hourly building energy simulations were carried out. The simulated results indicate that there will be substantial increase in A/C energy consumption under the impact of future climate change, ranging from 2.6% to 14.3% and from 3.7% to 24% for office building and residential flat, respectively. [Copyright &y& Elsevier]

Abstract: It becomes popular to use computer simulation technique to evaluate the performance of energy utilizations in buildings. The hourly weather data as simulation input is a crucial factor for the successful energy system simulation, and obtaining an accurate set of weather data is necessary to represent the long-term typical weather conditions throughout a year. This paper introduces a stochastic approach, which is called the first order multivariate Markov chain model, to generate the annual weather data for better evaluating and sizing different energy systems. The process for generating the weather data time series from the multivariate Markov transition probability matrices is described using 15-years actual hourly weather data of Hong Kong. The ability of this new model for retaining the statistical properties of the generated weather data series is examined and compared with the current existing TMY and TRY data. The main statistical properties used for this purpose are mean value, standard deviation, maximum value, minimum value, frequency distribution probability and persistency probability of the weather data sequence. The comparison between the observed weather data and the synthetically generated ones shows that the statistical characteristics of the developed set of weather data are satisfactorily preserved and the developed set of weather data can predict and evaluate different energy systems more accurately. [Copyright &y& Elsevier]

Abstract: The shading-type building-integrated photovoltaic (BIPV) claddings can act as power generators as well as external shading devices of a building, which reduce the energy consumption of the building. However, there is little information about energy impacts of different tilt angles of the shading-type BIPV claddings. By considering the typical meteorological conditions of Hong Kong, the energy performance of the shading-type BIPV claddings, in terms of the electricity generation and the cooling load reduction, is analyzed in this paper. The optimum tilt angle of PV modules for maximum electricity generation is found to be 20° instead of local latitude. Combining electricity generation and cooling load reduction, it can be concluded that the optimum tilt angles for the first type of the shading-type BIPV claddings vary from 30° to 50°, while the optimum tilt angle for the second type is 0°. [Copyright &y& Elsevier]

Abstract: Hong Kong is located in a typical subtropical region. The buildings in Hong Kong are subjected to high cooling demands for their air-conditioning systems throughout most of the year, and their contribution toward the total energy consumption is about 40%. Therefore, energy efficiency in buildings is essential to reduce the global energy use and improve the local environmental sustainability. This paper provides an overall review of the building energy research and efforts in Hong Kong over the last decade. Various aspects and energy saving measures, including energy policy, energy audit, design, control, diagnosis, building performance evaluation and renewable energy systems, studied or used to enhance the energy efficiency in buildings are reviewed. A brief introduction of the Hong Kong Building Energy Codes (BEC) and Hong Kong Building Environmental Assessment Method (HK-BEAM) are also provided to present the efforts of the local government and community on energy efficiency in buildings. This review aims at providing building researchers and practitioners a better understanding of buildings energy saving opportunities and approaches in cities particularly in subtropical regions and taking further proper actions to promote buildings energy efficiency and conservation. [Copyright &y& Elsevier]

Abstract: A benchmark study of the energy efficiency of private office buildings in Hong Kong was conducted in 2002 because energy efficiency was declining. In the study, private office buildings were divided into five user groups. For each group, a multiple regression model was developed to find the relationship between Energy Use Intensities (EUIs) and other factors, such as operating hours, for normalization and benchmarking purposes. In this paper we make use of the regression results to study the energy efficiency of private office buildings by different grades. In Hong Kong, office buildings are divided into three grades (A, B, and C) based on the quality of the facility, which is reflected in rental values; a Grade A office building denotes expensive luxury. We found that the EUI of Grade A office buildings is the highest, consuming over 50% of the total energy used in office buildings. Recently, the annual EUI of office buildings has improved even though Grade A floor space is increasing. This may be due to the promotion of the energy efficiency program launched in the last decade. [Copyright &y& Elsevier]