Yu Fat Lun

Energy saving by utilizing natural ventilation in public housing in Hong Kong.

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 air-conditioner 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%.

Numerical simulation of flow over topographic features by revised k–ε models

The accurate prediction of the wind energy distribution over terrains is important for making an appropriate selection of a suitable site for installing wind power plant. In this study, two-dimensional numerical simulations of flow over two common types of topographic features, i.e. a cliff and a hill, are presented. Three types of turbulence models, namely standard k-e and its revised linear form (Durbin model) as well as a revised nonlinear form (Shih model) are employed in this work. The performance of these models in predicting flow over these features is investigated. The accuracy of the prediction by using a z 0 type wall function to reproduce the effect of surface roughness on flowfield from these turbulence models is also examined.

Influences of Indirect Lifestyle Aspects and Climate on Household Energy Consumption

Abstract This study investigated the interrelationships among household energy consumption and indirect lifestyle aspects (including life schedule and family pattern), with particular emphasis placed on energy consumption pattern changes according to climatic characteristics. Instead of the conventional questionnaire survey and on–site measurement methods, this study focused on estimating the lifestyle related household energy consumption using life schedule data, which, in contrast, is low cost and time efficient. This study found that household energy consumption increases according to family size, however the per person energy consumption rate is less in larger size families. Retirees and housewives generally consume more household energy than working and student groups. Among working groups, household energy consumption increases according to age. Employee groups tend to consume less household energy than businessmen/women groups, while female working groups consume more household energy than male working groups. Also, people engaged in the agriculture/forestry sector and the self–employed consume more household energy, while labor and management/technical sectors consume the least. This study also revealed that households in colder regions generally consume more household energy due to higher energy needs for heating and lighting.

Energy Savings Potential of the Summer Time Concept in Different Regions of Japan From the Perspective of Household Lighting

Abstract Summer Time is a convention in which clocks are uniformly set one hour or more ahead of standard time to provide more daylight in the evenings during late spring, summer, and early fall. The main purpose of Summer Time is to make better use of daylight so that it more closely corresponds to our normal daily activities and thus saves energy. Japan is currently not observing Summer Time. This study thus investigated the feasibility of the energy saving potential of Summer Time/Double Summer Time from the perspective of household lighting in Japan and the optimum implementation period. The study found that both the Summer Time and Double Summer Time could reduce household lighting energy consumption, while the magnitude of energy saving potential of Double Summer Time is higher compared to Summer Time. It was also indicated that April–September is the optimum implementation period of Summer Time/Double Summer Time in Japan, from the perspective of household lighting. In terms of geographical location, under Double Summer Time, the household lighting energy saving ratio of the northern Japan regions is higher compared to the southern region. However, under Summer Time, the energy saving ratio of the southern Japan region is significantly higher.

Establishment of City Level Carbon Dioxide Emission Baseline Database and Carbon Budgets for Developing Countries with Data Constraints

Abstract One of the major constraints of developing countries in controlling carbon dioxide emissions is the limited availability of an emission database. Since there is no city level emission database in Malaysia, the authors have made the first attempt in the country to establish city level carbon dioxide emission data for different sizes of city using the System Dynamics based FML Model. From the results, it was found that the carbon dioxide emission of a city has a positive correlation with population size and GDP value, and an increasing emission trend is taking place in Malaysia regardless of the size of city. Projections of emission trends up to 2050 showed that if no aggressive actions were taken to cap emissions from the cities, there would be an extreme increase of emissions by as much as more than seven times of the current level. Hence, the authors have proposed three alternative approaches to set a city level carbon budget, i.e. equal share, population and GDP approaches. The study also demonstrated the capability of the present model in estimating present and future city level carbon dioxide emissions. The model can be used for establishment of a city level carbon dioxide emission database for the whole of Malaysia and in future may be applied to other developing countries.

Numerical Prediction of Flow Over Hill by Linear and Nonlinear k-ε Models

The present work employed two different types of k-e models, linear and nonlinear, to simulate flow over a 2D single hill. The aims of the study are to compare the performance of these two models in predicting flow over a blunt body in terms of separation point and recirculation, and to investigate the feasibility of using a linear revised turbulence model to geometry with small curvature, when applying to environmental problems.Copyright