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Passive downdraught evaporative cooling wind-towers: A case study using simulation with field-corroborated results
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Passive downdraught evaporative cooling wind-towers (cool-towers) have received special interests for their energy saving potential. Improving their performance and broadening their use will therefore be environmentally and economically beneficial. This paper presents a case study where cool-towers are designed and constructed to provide cool air to the semi-open courtyards of the Princess Nora University campus located in the hot, arid region of Riyadh, KSA. Each courtyard is served by two cool-towers, each of 30 m2 cross-sectional area, 32.8 m height. A brief on the system design is provided. The cool-towers performance is investigated through computational fluid dynamics simulation. Temperature and velocity profiles indicate an induced, cooler air breeze in the courtyard; outside air is cooled from 46℃ to 34–38℃, while the induced space velocity ranges from 1.5 to 3.5 m/s. A 560 kW cooling capacity is attained per tower. A substantial energy saving of around 3.30E+05 kW-h per courtyard per season is achieved. The expended energy associated with the used water is only 1% of the saved cooling energy. The normalized water consumption is around 0.04 kg/s per 100 kW cooling. The effect of distance between the towers on their performance is examined. The predicted performance is corroborated through field measurements.
http://bse.sagepub.com/content/early/2015/09/04/0143624415603281?papetoc
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... Whereas studies published in countries such as the UK [11], Iran [12], and Malaysia [13] prove that the high-level passive ventilation method such as wind catchers, towers, or scoops are one of the ways to circulate the high level less polluted air to inside. The ventilation method has been demonstrated in existing commercial buildings in Ahmedabad India, Tucson, Arizona, Seville, Spain [14] Riyadh, KSA [15,16]. ...
Wind Catcher is prominently known as a passive cooling device in buildings, especially in hot humid, and hot dry regions. In metropolitan cities of Pakistan, the wind catcher is seen as a lost heritage of the past. Campaigns to revive the wind catcher as a cooling and air displacement device are surfacing amongst the global communities. The chapter aims to address the social paradigm of wind catchers in the past and present and discusses its prospects for the highly polluted cities of Lahore and Karachi with a focus on the landscape. Using digital ethnography, the responses toward wind catchers in non-residential buildings were observed via blogs and videos. A total of 1386 nodes were coded from 54 sources in Nvivo for thematic classification based on a deductive approach of Past, Present, and Future. The chapter suggests the implication of wind catcher revival in the buildings of Lahore and Karachi as an effective wind ventilation solution for indoor air pollution, infiltration, thermal comfort, and cultural identity.
... Flow of air through the wind tower(Kassir, 2015) ...
Wind tower is zero energy natural ventilation device. Energy and energy conservation is common area of interest, now a days. In summer or hotter months of the year, Cooling tower provides comfort to occupants and also being a passive system, it saves electrical energy. Wind tower is also effective system which helps in pollution reduction and it also improves indoor air quality of the building. Wind tower passive cooling system is used in residential, commercial and other small and large buildings, in hot and arid or hot and humid regions. In hot and arid climate regions, two new types of wind tower called 'Wind tower with wetted columns' and 'Wind tower with wetted surface' are effectively used. In this work, it is explained the effectiveness of wind tower in the location where pollution is main concern. Although the Wind tower is effective in pollution reduction but how the polluted environment affects the wind effectiveness, that situation is evaluated, in this work. A general comparation between the wind tower effectiveness in polluted and non-polluted environment is made.
... Traditional wind catchers consist of several components, including openings, a roof, a head, a channel, and internal partitions (Ionescu et al. 2015). These are combined to form a hollow square tower that catches wind from any direction, creating an air stream that helps ventilate the occupied interior space (Kassir 2016). ...
Vernacular design has historical and cultural value that represents a local identity. It emerges from the surrounding environment, is inspired by nature, utilizes local materials and traditional construction methods, and considers the geographical and climate features of the region. Therefore, most vernacular designs offer sustainable solutions. Despite the abundance of research on sustainable design, few studies have addressed the relationship between vernacular and contemporary sustainable interior design solutions. Hence, the objective of this research is to examine whether sustainable vernacular design solutions can be revived and how they can inspire modern concepts of sustainability. The present article offers a review of literature on sustainable applications of heritage design, including a selection of architectural and interiors examples showcasing the revival of vernacular design. A survey was conducted to determine the potential of extending and implementing traditional concepts into contemporary design. This research reveals that sustainable solutions are integral part of vernacular design, which may bolster the effectiveness of contemporary sustainability.
... Traditional wind catchers consist of several components, including openings, a roof, a head, a channel, and internal partitions (Ionescu et al, 2015). These are combined to form a hollow square tower that catches wind from any direction, creating an air stream that helps ventilate the occupied interior space (Kassir, 2016). Samples of contemporary applications of wind catchers are shown in Figure 2. ...
Vernacular design has historical and cultural value that represents a local identity. It emerges from the surrounding environment, is inspired by nature, utilises local materials and traditional construction methods, and considers the geographical and climate features of the region. Therefore, most vernacular designs offer sustainable solutions. Despite the abundance of research on sustainable design, few studies have addressed the relationship between vernacular and contemporary sustainable interior design solutions. Hence, the objective of this research is to examine whether sustainable vernacular design solutions can be revived and how they can inspire modern concepts of sustainability. The present article offers a review of literature on sustainable applications of heritage design, including a selection of architectural and interiors, examples showcasing the revival of vernacular design. A survey was conducted to determine the potential of extending and implementing traditional concepts into contemporary design. This research reveals that sustainable solutions are an integral part of vernacular design, which may bolster the effectiveness of contemporary sustainability.
... Traditional wind towers consist of several components, including openings, a roof, a head, a channel, and internal partitions [23]. These are combined to form a hollow square tower that catches the wind from any direction, creating an air stream into the tower's shaft that helps ventilate the occupied building space [24]. They come in various designs: unidirectional, bi-directional, and multi-directional [25]. ...
Vernacular interior design consists of spaces that affirm a unique material, have affinity with the local region, and carries the potential to create a sustainable, harmonious relationship between humans, nature, and the built environment. In the United Arab Emirates (UAE), sustainable interior design concepts were inherited from vernacular to modern spaces. Despite the abundance of research on sustainable design, few studies have addressed the relationship between vernacular and modern sustainable interior design solutions. Studies on heritage-based interior design solutions indicate the potential to extend and implement traditional concepts into contemporary design. Hence, the objective of this research is to identify the major elements of vernacular sustainable design in the UAE and measure its applicability to contemporary interior design solutions. This paper explores some examples that reflect the impact of the country’s heritage on contemporary sustainable interior design, concluding that sustainable concepts in heritage design may inspire contemporary interior designers to reflect on the effectiveness of traditional design solutions.
With more people now living in urban areas than outside of them, urbanism is becoming an increasingly important socioeconomic and ecological arena for our species in the twenty-first century. Understanding historical and regional variation in urban trajectories and land use has the potential to provide long-term perspectives on pressing contemporary challenges. Here we review how novel methods and approaches are enabling archeology to shed new light on the past 5,500 years of urban life. From exploring urban variability in ‘extreme’ environments to studying the interaction of urbanism and the Earth system, we argue that the past provides a critical, growing reservoir of knowledge for contemporary urban scientists and planners.
The main theme is “materiality”, as an umbrella concept that
embraces all the fragments of the whole materialization
process starting from architectural imagination,
conceptualization, and design to the act of construction.
In this respect, discussing materiality under three
main themes as “architectural design”, “research” and
“technology” is aimed. Within this scope, the potential
discussions could be around but not limited to architectural
practice, architectural design education, heritage, and
conservation, vernacularity, urban context, theory, R&D in
architectural materiality, tectonics, computation, media and
immersive visualization, materiality as a process, methods
of computational design and materiality. The collected
papers addressed a wide range of disciplinary fields that are
somewhat related to architecture, from robotics to theory
and criticism, from professional practice to educational
practices, from urban scale to the product/material scale.
The edited volume explores Oman 21st Century issues and challenges aims to explore key issues and challenges Oman Economy and society is facing in modern times.
The performance of oscillating water column (OWC) wave energy converters (WEC) is highly affected by airflow rate. In this paper, a novel system is proposed that increases airflow rate and, therefore, output power through the integration of a mechanical structure known as a windcatcher with a conventional OWC. To investigate the hydrodynamic behaviour of the proposed system, a non-linear two-dimensional computational fluid dynamics (CFD) model is employed, along with the Reynolds Averaged Navier-Stokes (RANS) approach. The results of a comparison of the proposed OWC to a conventional type reveal a significant increase in airflow rate through the turbine blades, realizing an increase in converter output power. Moreover, the results show a power generation consistency in the proposed hybrid system, as the amplitude of the oscillatory part of the turbine airflow rate is diminished. Therefore, the proposed OWC converter not only generates significantly more power than a conventional type, it also has smoother power generation performance.
Passive Evaporative Cooling is one of the most efficient and long recognized ways of inducing thermal comfort in predominantly hot and arid climates. In order to extend the use of evaporative cooling, a downdraft evaporative 'cool tower' was integrated at the Solar Lab at the School of Architecture and Landscape Architecture, Arizona State University. The model explains how elevated temperature and pressure differences can increase the efficiency of a cooling tower, and how adding a Solar Chimney can create that elevated pressure difference. The synergy created by the cooler incoming air through the cool tower (positive pressure) and the hot air exiting through the solar chimney (negative pressure) will definitely alter the air movement and therefore the fluid dynamics. Our objective is to analyze the indoor air velocity increment and the indoor air movement, as well as the possible heat gains through convection and conduction due to increased air circulation. To accomplish our research, a scaled model has been built at the Solar Laboratory of the College of Architecture and Environmental Design where we will be executing, monitoring and collecting data for a period from 25 th April to 5 th June, 2005. The time for data under consideration for the paper is 24 hours from 9:17 AM, 31 st May to 9:17 AM, 1 st June. Conference Topic: 4 Innovative Low Energy Technologies.
In a conventional down-draft evaporative cool tower (DECT), dry ambient air is drawn in at the top and cooler moist air is delivered at the bottom. Most of the cooling occurs near the inlet, where water is introduced and air temperature approaches the wet bulb. A novel DECT was developed which incorporates a secondary air inlet and complex longitudinal section that comprises two partly overlapping cones. The complex section and the addition of a secondary air intake near the middle required a sophisticated water spraying system. In addition to maximizing the cooling potential, the spraying system was designed to limit spray drift beyond the base of the tower, to reduce maintenance costs (especially due to clogging of the sprayers) and to minimize pumping energy. Analysis shows that maximum cooling may be obtained either by employing a very fine spray, requiring the introduction of a relatively small volume of water, or by spraying a larger volume of coarser drops. However, spraying fine drops requires more pumping power, finer nozzles are more likely to clog and small drops of water aggravate the problem of drift near the tower base. If full evaporation of the water spray is not required and excess water is collected for reuse, the second option is thus preferable. In addition to the theoretical analysis, the paper presents experimental findings on temperature reduction, water consumption and cooling output of an 8-meter high prototype tower constructed at Sde Boqer, Israel.
A multi-stage down-draft evaporative cool tower (DECT) was developed as an improvement to a previously developed single-stage design. The new tower incorporates a secondary air inlet, added to reduce the water consumption required to produce a desired cooling output in a tower of given maximum cross-section and primary inlet geometry. The secondary air, which may be drawn from the interior space being chilled, is cooled by evaporation in the lower section of the tower. This paper reports on the results of experiments conducted to establish the aerodynamic performance of the design prior to installation of a water spraying system. Design of the water spraying system and experiments on cooling performance are discussed in a companion paper.
This paper discusses the development of a new module in EnergyPlus that predicts the cooling performance of PDEC towers with sprays. It introduces an overview of PDEC towers and existing models. A simulation model is employed to design and evaluate PDEC towers, and its modelling algorithm in EnergyPlus is described. An analysis of the capability in different climates and the energy performance of PDEC towers has been performed by using the model implemented, and the main results from various case studies are presented. Overall, the model is capable of predicting air conditions as well as air flow rates from PDEC towers so that EnergyPlus can calculate appropriate indoor air conditions and thermal comfort in a zone.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
This is the first of a series of four papers that describe a 3-year EU-funded research project into the application of passive downdraught evaporative cooling to non- domestic buildings. In this paper various evaporative cooling techniques are reviewed. By spraying fine drop lets of water at the top of atria, a downdraught of air cooled by evaporation can be produced. Such direct eva porative cooling using an evaporation tower appears to be a suitable approach for partly displacing the need for air-conditioning in hot, dry climates. It can satisfy fresh air requirements and reduce or eliminate demand for mechanical cooling. Examples of this cooling technique in Southern Europe and the Middle East have already demonstrated its operation and potential energy sav ings. However, limitations, primarily due to control of the system, have been identified. This introductory paper presents the theoretical basis of evaporative cooling, reviews some historical precedents, and discusses their relative strengths and weaknesses. Three further papers in this series will disseminate the main findings of the project.
In the present study, an attempt is made to study the cooling performance of a wind tower in a hot and dry region, Yazd, in Iran. For the relevant experiments and numerical studies, at first, the temperature and wind velocity inside and outside of the wind tower measured. Based on four-day measurements during last summer, a computer program was designed with language C++ to solve the equations. Also in the study the effects of parameters including wind tower height, variety of the materials used in the wind tower walls, the amount of vaporized water, the temperature of input and output air, the wind velocity and the relative humidity were investigated.Furthermore, to develop, a natural flow of air, for days without blowing a wind the role of solar chimney was considered.Finally, to evaluate the method of integral view and take information about streamlines of airflow in wind tower (Baud-Geer), velocity, pressure, humidity, temperature and density profile of fluid, Fluent software is applied to analyze the air flow in the wind tower in differential view for three-dimensional and steady state conditions with water spraying at the top of wind tower.The results indicate that the evaporative cooling is very effective in a hot and dry region. The temperature decreases considerably, if the wind towers are equipped with the water vaporization system. This causes the air becomes heavier and a natural motion of air through downside of wind tower to be produced.
A multi-stage down-draft evaporative cool tower (DECT) was developed as an improve- ment to an existing single-stage design. The new tower incorporates a secondary air inlet, added to increase the cooling output and reduce the water consumption in a tower of given cross-section and primary inlet geometry. The secondary air, which may be drawn from the interior space being cooled, is cooled by evapo- ration in the lower section of the tower. This paper reports on the results of experi- ments conducted to establish the aerodynamic performance of the design prior to installation of a water spraying system. Design of the water spraying system and experiments on cooling performance are discussed in a companion paper. 1. BACKGROUND
The performance of a passive cooling system was evaluated as part of design works for the project of an auditorium. The passive cooling system uses the atmosphere as natural heat sink and incorporates a solar chimney together with an evaporative cooling tower. The natural venti- lation is enhanced with the help of the solar chimney and fresh air is cooled down by passive downdraught evaporative cooling. The applica- tion of this system to the acclimatization of an auditorium was evaluated. A model was devel- oped to this purpose, which allows to foresee the temperature and the relative humidity of the air in the auditorium. The evaluation of the per- formance of the passive cooling system was based on the number of cooling degree hours. The model was also used to evaluate the in- fluence of the main parameters characterizing the solar chimney and the evaporative cooling tower upon the thermal environment within the auditorium fully occupied. The period under study was June to September and it comprised the diurnal period, from 6h 30m to 17h 30m (so- lar time).
Air conditioning is now recognized as a significant factor in global
warming and climate change. In the search for alternatives, passive
downdraught evaporative cooling (PDEC) is proving to be both
technically and economically viable in different parts of the world.
Brian Ford describes the principles and current practice of this
innovative approach to cooling in the hot dry regions of the world.