The development of commercial wind towers for natural ventilation: A review

doi:10.1016/j.apenergy.2011.11.066

Applied Energy

Volume 92, April 2012, Pages 606-627

https://doi.org/10.1016/j.apenergy.2011.11.066 Get rights and content

Abstract

Wind towers have been in existence in various forms for centuries as a non mechanical means of providing indoor ventilation, energy prices and climate change agendas have refocused engineers and researchers on the low carbon credentials of modern equivalents. The purpose of this study is to evaluate the development of wind tower device and their integration into buildings, thus providing a comprehensive review of current and potential wind tower development. Previous works have investigated wind and buoyancy factors for induced natural ventilation to drive air flow through the wind tower. Numerous studies have investigated the effects of different configurations and components on the performance of wind towers. Studies include the use of evaporative cooling device inside the tower to improve its thermal performance, the use of solar chimneys, courtyards and curved roofs to enhance the air movement inside the structure, and the use of volume control dampers and ceiling diffuser to optimize the fresh air flow rate and indoor conditions. The review further highlights the different cooling techniques which can be integrated with wind tower systems to improve ventilation and thermal performance. The basic principles of each technique along with its corresponding capabilities are summarized along with their advantages, limitations, and applications.

Introduction

Increasing awareness of the need for energy efficient and environmentally friendly approach for building design has renewed emphasis on the integration of natural ventilation devices in buildings. Heating, Ventilation and Air Conditioning (HVAC) accounts for a substantial amount of the energy use in building and represents a significant opportunity for energy savings. Ventilative methods which do not use mechanical intervention and thus energy free are termed natural ventilation. Sustainable ventilation technologies have been proposed to reduce the buildings energy consumption and carbon footprint. An example of one such innovative ventilation device is the wind tower. Montazeri and Azizian [1] defined the wind tower as a device which facilitates the effective use of natural ventilation in a wide range of buildings in order to increase the ventilation rates. Wind towers have been used in the hot and arid regions of the Middle East for many centuries to provide passive cooling and achieve thermal comfort. Fathy [2] suggested that traditional solutions in vernacular architecture can be adopted or integrated with new technology to make them compatible with modern requirements. Conventional and modern wind towers are increasingly being used in modern buildings to minimize the consumption of non renewable energy. Modern design of wind towers combines the ventilation principles and passive stack in one design. Wind tower architecture can be integrated into the designs of new buildings, to replace or assist mechanical ventilation systems. However before adapting new technologies, it is necessary to research into the function and design parameters of traditional and modern wind catchers and to demonstrate how it can be applied and improved in order to provide a simple and effective means of natural ventilation.

Section snippets

Natural ventilation using a wind tower

Architectural design of buildings highlighted the potential advantage of natural ventilation systems for occupancy comfort. Natural ventilation has become an attractive solution for not only reducing the energy usage and cost but also for providing good indoor air environment while sustaining a comfortable, healthy, and productive internal climate. Natural ventilation systems use the natural pressure differences surrounding a structure, caused by wind and temperature driven forces to direct the

Micro climatic variation

Roaf [10] investigated different types and functions of wind towers which varied significantly from one region to another, depending on factors such as micro–macro climate conditions and occupant’s comfort expectations. Microclimate refers to the specific climatic condition in a relatively small area, such as a room or an enclosed space which can be controlled and modified. The atmospheric conditions in a microclimate; wind, temperature, humidity may differ from the conditions existing over the

Design of wind tower systems

The design of wind tower system has been traditionally based on the topography, climatic conditions, personal experience of architects, social position of the occupants and variation in height, cross-section of air channel, number of openings, size and positioning of openings, form, construction materials, and placement of the tower with respect to the building. Montazeri et al. [14] stated that the efficiency of wind towers is reliant upon creating the maximum pressure difference between the

Wind tower cooling techniques

Naturally ventilated buildings do not require additional energy to move the airflow within a structure. However, the cooling capabilities of conventional wind towers which depend on the structure design itself are limited. Therefore it is essential to cool the air in order to improve the thermal comfort of its occupants [24]. This section looks at cooling techniques which can be incorporated to a standard wind tower design to improve its ventilation and thermal performance.

Fig. 14 shows a

Traditional wind tower systems

The traditional architecture of Central Asia and the Middle East is the product of the land topography, the climatic conditions, social and culture. The vernacular architecture has brought many practical solutions and strategies to solve the human’s needs and local environmental problems such as the wind tower, which is a key element in the architectural design of traditional structures. The wind tower design is based on the natural cooling systems in Iranian traditional architecture [47].

Commercial wind towers

Modern architects and engineers integrated the principles of traditional wind tower with modern technology as helpful devices to increase the quality and efficiency of the supplied air. Modern wind towers provide natural ventilation and light to any space in a building. Hughes and Ghani [22] described a commercial wind tower as a top-down roof mounted, multi directional device used for naturally ventilating buildings. Modern wind towers are usually compact and smaller in size compared to the

Development potential of future systems

In recent years, there has been an increasing awareness of the need for energy efficient and environmentally friendly approach for future building design which has renewed emphasis on the application of wind tower devices. Experimental theoretical and numerical investigations studies have been conducted to investigate the performance of wind towers. The results proved that passive air movement inside the building improves the air quality and reduces the internal temperatures. This concept has

Results summary

From the reviewed wind tower systems and cooling methods, it is considered that each system has its own advantages and limitations. Table 1 summarizes an outline of the traditional and modern wind tower systems under review along with the features, application, limitations and typical flow rates obtained from previous related works. It is observed that the commercial wind vent device generated the highest air flow rates, supplying up to 650 l/s while the solar-wind tower which rely on buoyancy

Discussion

Experimental, theoretical and numerical investigations of the performance of different types of wind tower systems have been reported in the literature. However, the study of wind tower performance has generally been limited to controlled experiments. Hence, it is difficult to compare the performance of the wind tower systems. Montazeri [1] and Gage and Graham [16] used wind tunnel and smoke visualization analysis to analyze the ventilation performance of multi-directional wind towers. Elmualim

Conclusions

This paper reviewed wind tower designs with respect to traditional techniques such as the badgir wind tower and modern systems including the wind vent and wind scoop. This study emphasized the importance of wind towers and gives insight into the application of passive cooling systems as an alternative to the high-energy consuming mechanical ventilation systems. Traditional wind towers have been designed and built using old methodologies; therefore they have design limitations which can be

Acknowledgments

This publication was made possible by a NPRP Grant from the Qatar National Research Fund (A member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. NPRP 09-138-2-059.