Parameterization Studies of Solar Chimneys in the Tropics

Alex Tan,Nyuk Wong

doi:10.3390/en6010145

Abstract

The paper examines the effect of the solar chimney’s stack height, depth, width and inlet position on the interior performance (air temperature and speed at 1.20 m height above the ground) as well as proposes an optimal tropical solar chimney design. Simulations show that the output air temperature remains constant while the solar chimney’s width is the most significant factor influencing output air speed. The solar chimney’s inlet position has limited influence on the output air speed although regions near the solar chimney’s inlet show an increase in air speed. Furthermore, a regression model is developed based on the solar chimney’s stack height, depth and width to predict the interior air speed. To optimize solar chimney in the tropics, the recommendation is to first maximize its width as the interior’s width, while allowing its stack height to be the building’s height. Lastly, the solar chimney’s depth is determined from the regression model by allocating the required interior air speed.

Highlights

The employment of natural ventilation is almost as old as vernacular architecture
The principle of the solar chimney effect is a combination of solar stack-assisted and wind-driven ventilation
The stack pressure difference driving the air movement is a combination of the different densities between the interior and ambient environment as well as the stack height where the greater the stack height and temperature difference, the stronger the pressure difference

Summary

Introduction

The employment of natural ventilation is almost as old as vernacular architecture. Examples include the wind assisted badgir or wind tower commonly used in the Middle East since 900 AD and the stack assisted chimneys developed since the Roman period. The principle of the solar chimney effect is a combination of solar stack-assisted and wind-driven ventilation. Air in the chimney expands due to solar heating and being relatively lighter, rises out of the chimney outlets, drawing the cooler air into the interior through the fenestrations. This pull effect is further complemented by the push effect from the ambient wind. The stack pressure difference driving the air movement is a combination of the different densities between the interior and ambient environment as well as the stack height where the greater the stack height and temperature difference, the stronger the pressure difference. In solar assisted stack ventilation, the temperature difference is achieved from heat gained due to solar irradiance

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