An ideal window ratio for energy saving with integration of daylighting, electric lighting and air-conditioning

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An ideal window ratio for energy saving with integration of daylighting, electric lighting and air-conditioning

 

Author: Wang, Xin
Title: An ideal window ratio for energy saving with integration of daylighting, electric lighting and air-conditioning
Degree: M.Eng.
Year: 2016
Subject: Windows -- Design and construction.
Buildings -- Energy conservation.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: xii, 76 pages : illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2917152
URI: http://theses.lib.polyu.edu.hk/handle/200/8664
Abstract: Nowadays, energy saving and air pollution have been hot topics in many countries. For all kinds of energy consumption, the energy consumption for commercial buildings has a share about 66% of the total energy use in Hong Kong. There have been many methods to improve building energy performance in recent decades. Among all energy saving strategies, window design has not been ranked at high priority. Many windows of new buildings are not designed with due consideration of the impacts on artificial lighting systems, air conditioning systems and total building energy efficiency. Architects only pay attention to the aesthetics of the building facades and the visual comfort of the occupancy. The effect of the window to wall ratio on the total energy consumption of a building have not been fully evaluated. With proper arrangement, design of windows and proper window to wall ratios, it does not only reduce the electricity consumption of the artificial lighting system, but can also decrease total cooling load of the air conditioning system. This paper will suggest an ideal window to wall ratio in order to decrease the energy consumption of the artificial lighting system and air conditioning system as far as possible. The key step is to use DIALux to simulate the daylight conditions in a room. According to the daylight conditions, the layout of the lighting system can be derived. The power density of the lighting system on the working surface can also be obtained. A basic requirement of DIALux is that the illuminance on the working surface must reach 500lux. The power density is one of the inputs to EnergyPlus. The software is to calculate the cooling load of the room with different configurations, operation schedule, building envelope and many others. The results from the simulations of these two software can be used to analyse the energy performance of the rooms with different window to wall ratios. The ideal window ratios with different room configurations will be suggested at the end of this project. The results indicate that the energy consumption of lighting system and air-conditioning system keeps constant when the window to wall ratio is less than 40% and the energy consumption increases when the ratio is larger than 40%. It can be concluded that when the window to wall ratio is less than the critical value, the energy saved from the lighting system can offset the increased energy consumption of the air-conditioning system, and beyond that value, the energy saved from lighting system cannot offset the increased part. From the simulation results and the analysis, it can be predicted that the ideal window is larger when the room area is larger.

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