Charles C.K. Cheng

Predicting Energy Saving and Life-Cycle Cost Analysis for Lighting and Daylighting Schemes

Energy-efficient lighting installations, together with dimming controls, can make a good contribution to building energy conservation. Energy-efficient lamp fittings provide high light-output values with less power consumption, and electronic circuitry is more efficient than conventional ballasts. Dimming controls can lower lamp output to save energy when illuminance from daylight and light fittings exceeds the target value. This article studies lighting energy consumption and cost analysis when such lighting schemes are used. The findings would be useful for planning green and sustainable energy schemes and applicable to other spaces with similar architectural layouts and lighting control systems.

CFD wind tunnel test: Field velocity patterns of wind on a building with a refuge floor

This paper reports a CFD wind tunnel study of wind patterns on a square-plan building with a refuge floor at its mid-height level. In this study, a technique of using calibrated power law equations of velocity and turbulent intensity applied as the boundary conditions in CFD wind tunnel test is being evaluated by the physical wind tunnel data obtained by the Principal Author with wind blowing perpendicularly on the building without a refuge floor. From the evaluated results, an optimised domain of flow required to produce qualitative agreement between the wind tunnel data and simulated results is proposed in this paper. Simulated results with the evaluated technique are validated by the wind tunnel data obtained by the Principal Author. The results contribute to an understanding of the fundamental behaviour of wind flow in a refuge floor when wind is blowing perpendicularly on the building. Moreover, the results reveal that the designed natural ventilation of a refuge floor may not perform desirably when the wind speed on the level is low. Under this situation, the refuge floor may become unsafe if smoke was dispersed in the leeward side of the building at a level immediately below the refuge floor.

Wind Tunnel and CFD Studies on Wind Flow Around a High-Rise Building with a Refuge Floor

Under the Building Codes of Hong Kong Special Administration Region, the provision of refuge floors has been an indispensable element in their high-rise building design since 1996. A refuge floor is a designed temporary safe place to improve high-rise evacuation during fires. It is a fire-protected semi-permeable feature in buildings taller than 25 storeys. Direct cross natural ventilation by natural wind is an important design criterion of a refuge floor. It helps to prevent any smoke entering the refuge floor from logging and impairing the safe conditions of the floor. This paper reports a study of the wind flow patterns around a high-rise building with a refuge floor at wind incident angle perpendicular to the building. The study is based on CFD simulations which are qualified by wind tunnel data. The results revealed a smoke hazard potential if smoke is dispersed from the rear face of the building at a level closely below the refuge floor, Smoke may be logged inside the refuge floor area behind the internal blockage.

An analysis of wind energy potential for micro wind turbine in Hong Kong

Renewable energy can play an important role in meeting the ultimate goal of replacing parts of fossil fuels to generate sustainable, inexhaustible, clean and safe energy. One of the promising applications of renewable energy technology is the installation of wind turbine that has been identified as having potential for wide-scale application in Hong Kong. Locally, wind turbines are seldom installed in building developments. The barriers include limited installation space available, the heavily obstructed external environments and noise and vibration problems. The apposite places for the installation would be on the roof/rooftop of low-rise buildings located in low-density zones. Relevant wind data and output power generated on-site, which may be quite site-dependent, are essential for modelling and evaluating the wind energy conversion system. Long-term measured wind data are crucial to the study of wind energy potential. This work studies the wind data and micro-wind turbine used in dense urban terrain and low-density area. Technical data including wind speed and output power were analyzed and reported. To achieve 1% of total building energy consumption generated from wind power, 17 micro-wind turbines are required to be installed in this institutional building located in low-density zone. Practical application: Wind turbine is one of the typical applications of renewable energy technology. However, micro-turbines are not popularly installed in building developments. This work analyses the measured wind data and the energy performance of micro-wind turbines installed in an institutional building. The findings provide the on-site measured data for design and assessment of micro-wind turbines installed in building blocks.

A CFD Study of Hong Kong Refuge Floor Design: Floor Height Effect

Abstract Since 1996, the provision of a refuge floor has been a mandatory feature for all new tall buildings in Hong Kong. These floors are designed to provide for the building occupants a fire safe environment that is also free from smoke. However, the desired cross ventilation on these floors to achieve the removal of smoke, assumed by the Building Codes of Hong Kong, is still being questioned so that a further scientific study of the wind-induced ventilation of a refuge floor is needed. This paper presents an investigation into this issue. The developed computational technique used in this paper was adopted to study the wind-induced natural ventilation on a refuge floor. The aim of the investigation was to establish whether a refuge floor with a central core and having cross ventilation produced by only two open opposite external side walls on the refuge floor would provide the required protection in all situations taking into account behaviour of wind due to different floor heights, wall boundary conditions and turbulence intensity profiles. The results revealed that natural ventilation can be increased by increasing the floor height provided the wind angle to the building is less than 90°. The effectiveness of the solution was greatly reduced when the wind was blowing at 90° to the refuge floor opening.

A Reduced Scale-Modeling Study on Wind and Smoke Interaction at a Refuge Floor in a High-Rise Building

Refuge floor is considered as a temporary safe place for evacuees in super high-rise buildings and is a prescriptive requirement in Hong Kong’s Building Codes. The degree of safety of refuge floors under fire situations may be impaired if the floor is affected by smoke from other floors. In the circumstance, Hong Kong’s code prescribes that cross-ventilation should be provided in refuge floor so as to prevent smoke logging. This article reports studies on wind and smoke interaction at a refuge floor by using reduced-scale experiments in wind tunnel and computational fluid dynamics models. Results have indicated that cross-ventilation induced by permanent opening to the external may not guarantee that smoke logging will not happen in refuge floor.