K.L. Cheung

Evaluation of a Simple Method for Determining the Vertical Daylight Factor against Full-Scale Measured Data

Hong Kong is one of the most densely populated cities in the world. Its buildings are largely high-rise blocks constructed close to each other and, hence outdoor obstructions play significant roles in daylighting designs. The light reflected from the ground and surrounding buildings can be important sources of interior lighting and detailed computations are required. We currently propose a calculation procedure in terms of a number of regression equations to determine the daylight illuminance on vertical surfaces. This paper presents the work to assess this approach via full-scale measurements under real sky conditions. The mean surface reflectance for external obstructions was estimated using lighting simulation techniques. It was shown that daylight illuminance obtained by the proposed method were in reasonably good agreement with measured readings. The simple nature of the proposed approach offers building professionals and students a reliable and convenient alternative to predict daylight illuminance particularly when different daylighting schemes and concepts are being considered.

Evaluation of simplified procedure for indoor daylight illuminance determination against data in scale model measurements

An accurate estimation of the amount of daylight entering a building is the key step in evaluating daylighting designs. The concept of the daylight coefficient (DC), which considers changes in the luminance of the sky elements, offers an effective way of computing indoor daylight illuminances under various sky conditions and solar positions. We currently propose a numerical procedure in the form of nomograph to compute the interior daylight illuminance using the DC concept. This paper presents the work to validate this method via scale model measurements under different actual sky patterns. It was shown that daylight illuminances calculated by the proposed method were in reasonably good agreement with measured results. The findings will hopefully provide building professionals and students with a reliable and simple alternative to current practices that incorporate sky luminance variations to predict the indoor daylight illuminance and assess visual performance under various real sky conditions.

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.

Evaluating an Indoor Daylight Illuminance Calculation Tool Against Full-Scale Measured Data

Abstract The determination of daylight illuminance in internal spaces is a key issue in daylighting analysis. The recently introduced concept of the daylight coefficient (DC), which considers changes in the luminance of sky patches, provides an accurate way for calculating indoor daylight illuminance under various sky patterns and sun positions. This paper proposes a simplified numerical procedure to estimate interior daylight illuminance using the DC concept. The paper presents an evaluation of the new method via full-scale field measurements under different sky conditions. The findings indicate that the daylight illuminances obtained by the proposed approach were in agreement with measured readings. The simple nature of the proposed method offers building professionals and students a reliable and convenient alternative to extensive calculations that incorporates sky luminance variations to predict the daylight illuminance and assess visual performance under various sky conditions.