Review of Windcatcher Technologies_Omidreza

Renewable and Sustainable Energy Reviews 16 (2012) 1477 1495

Contents lists available at SciVerse ScienceDirect

Renewable and Sustainable Energy Reviews

j ourna l h o mepage: www.elsev ier .co

Review

OmidrezSolar Energy Re

a r t i c l

Article history:Received 22 NAccepted 26 N

Keywords:Windcatcher tWindcatcher aWindcatcher cEfciency

Contents

1. Introd2. Wind

2.1. 2.2. 2.3. 2.4. 2.5. 2.6.

3. Wind3.1. 3.2. Heat source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14853.3. Use of evaporative cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14853.4. Hybrid commercial windcatcher system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14863.5. Windcatcher for outdoor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14873.6.

4. Wind4.1. 4.2. 4.3. 4.4. 4.5.

5. Summ6. Recom

Refer

1. Introdu

Depletiofossil-fuel p

CorresponE-mail add

1364-0321/$ doi:10.1016/j.Down draft windcatcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1487catcher conguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1488Inclination angle and meteorological parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1488Louver conguration in commercial windcatcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1489Windows conguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1491Combination of windcatcher and solar chimney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1492Combination of windcatcher and inverted airfoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1493ary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1493mendation for further studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1494

ences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1494

ction

n of natural resources, global warming and increase ofrice is a real concern of human beings [1]. Moreover,

ding author.ress: [email protected] (O. Saadatian).

the population growth has caused more than 200% increase of CO2emission from 1995 to 2011 (see Fig. 1). Buildings sector accountfor more than 40% of the total worlds energy consumption [2].The fact is that energy used in our buildings, including ventilation,heating, and cooling systems accounts for more than 60% of totalbuildings energy consumption [3]. Therefore, natural ventilationincreasingly gained the attention of building stakeholders to reduce

see front matter 2011 Elsevier Ltd. All rights reserved.rser.2011.11.037 of windcatcher technologies

a Saadatian , Lim Chin Haw, K. Sopian, M.Y. Sulaimansearch Institute (SERI). Level 3, Perpustakaan Tun Sri Lanang, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

e i n f o

ovember 2011ovember 2011

echnologiesttributesongurations

a b s t r a c t

Mechanical cooling systems in buildings are the main producers of carbon dioxide emissions, whichhave negative impacts on environment and amplify global warming, particularly in hot climate. Due tothe lack of energy supply, windcatchers can be utilized as a sustainable attempt for cooling and ven-tilation purposes. The objective of this paper is to review and provide a comprehensive literature onwindcatcher system for space cooling and ventilation. The concepts were discussed according to therelevant parameters of windcatcher, i.e. windcatcher attributes, windcatcher congurations and wind-catcher technologies. The pros and cons of this green architectural feature have also been highlightedand the future research need in this realm of study is proposed.

2011 Elsevier Ltd. All rights reserved.

uction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1477catcher attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478Vernacular windcatcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478Modern windcatcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478Super modern windcatcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1479Windcatcher with different opening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1479Shape of windcatcher . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482Windcatcher with damper and egg crate grille . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1482

catcher technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1484Wind and buoyancy effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1484m/locate / rser

1478 O. Saadatian et al. / Renewable and Sustainable Energy Reviews 16 (2012) 1477 1495

energy conslow energy

Wind asable energyenvironmenhygiene indi.e. windcatential in inc[3,79].

One of building inconcept of Britain for tof the passrent challendesigning nars and acathe extremthey believwindcatche

That steresearch onclimate. Duhumid climinclude meand humid

2. Windca

Windcata building woutside [14groups namwindcatchethese threethe advancland, and chbeen madethe present

Windcatticularly in other Arab Algeria, Egy[12]. This pregions for building he

The funBased on th

tche, andre aspite rguehat ionspa fevf winst ze

arearentnt ty

rnac

nacuBaudhiteced asArabned w

is a w Din le ofd-Ge

formnd ally raf autchecity o

of th, rics, ane these trFig. 1. CO2 emission from 1997 to 2025 [10].

umption and has opened a new area of study known as architecture [4,5].

a free driving force is one of the important renew- [6]. This green energy, not only provides a good indoortal quality but also provides a comfortable, healthy andoor climate. Wind related green architectural features,cher, solar chimney, light well as well as atria are inu-reasing the stack effect as a ventilation driving forces

the natural ventilation devices, neglected in currentdustry, is the windcatcher or wind tower system. Thewindcatcher has been commercially applied in thehe past 30 years [11]. Despite the fact that utilizationive system is very important for combating the cur-ges of the world, windcatcher is drastically ignored inew modern buildings [7,12,13]. Moreover, many schol-demicians did not propose employing windcatcher ine hot and humid climate such as tropical climate sinceed that the buoyancy effect is the main driving force ofr which in tropical climate is not signicant.reotype motion has resulted not to conduct enough

utilization of windcatcher in extreme hot and humide to the lack of windcatcher research done in hot andatic conditions, this paper takes an opportunity toasurement results of a windcatcher research under hotclimatic conditions by the authors.

tcher attributes

cher is an architectural feature mounted on the roof ofhich looks like a tower and brings in the fresh air from]. Windcatchers can be categorized in three followingely: vernacular windcatchers, modern or commercialrs and super modern windcatchers. The foundation of

windcasectionstructu

Deshave aplace tmore cMalariness ois almofor theof diffediffere

2.1. Ve

Vercalled bic arcregardtop of combiwhichMuhibexamp

Baudiversemers anormastudy owindcain the designdignityBesidecaptur

The types of windcatchers is almost the same. However, forement of technology, increase the price of energy andange in the expectation of people some changes have

to the vernacular windcatchers to make it useable for situation.cher has been utilized in the hot and arid regions, par-the Persian Gulf region, i.e. Iran, Iraq, Dubai, Qatar, andcountries in one hand and north of Africa region, i.e.pt and other north African countries in another handassive tool has been the main cooling system of thesethe past three thousand years, functioning to reduce theat load [7,12,1520].ction of this technology is not very complicated.e observation of authors, there are various forms of

quadrants. wind changwindcatche

2.2. Moder

There hwindcatchewindcatcheThis awarenmercial wiincorporatecompletely(see Fig. 4).Fig. 2. Arabic windcatcher or Malqaf [27].

rs in terms of height of tower, windcatcher cross- the number of openings, which is related to building

well as the architect who has designed it.all the advantages of windcatcher, some academiciansd on the utilization of windcatcher, because it is ansects and dust may enter easily [21]. This problem isicuous in South-East Asia and Africa where Dengue ander kill thousands of people each year. Another weak-dcatcher is that the control of the volumetric ow ratero [21]. Likewise, the windcatcher is not very efcients with low wind speed [21]. In this part, the importance

factors that contribute in windcatcher operation andpe of windcatcher will be highlighted.

ular windcatcher

lar windcatcher is a type of green technology, which is-Geer in the Persian Gulf area and Malqaf in the Ara-ture such as Egyptian architecture [2224]. Malqaf is

a bidirectional windcatcher which is mounted on thes covered court yard [25] (Fig. 2). Malqaf is normallyith another architectural element known as Salasabilavy marble plate that is linked to a source of water [25].Al Muwaqqi house in Cairo can be regarded as a popular

this kind of windcatcher [26].er, on the other hand, is not only bidirectional and hass, and various shapes and they are used during sum-

re closed during winters [28]. This element height isnged between 5 and 34 m [29]. Based on an archivalthors and their eld observation, the tallest vernacularr of the world is 33.80 m located in Dolatabad gardenf Yazd. In the Persian Gulf vernacular architecture, thee form and shape of this technology depended on thehness and social position of the building owners [30].

increase of the height in a windcatcher enables it to faster winds with less dust [7,21,30].aditional windcatchers are normally divided into fourThis makes the windcatcher system safer to periodices [16]. There are also various architectural forms ofr with diverse efciency (see Fig. 3).n windcatcher

as been an increasing awareness of the application ofr in the world which triggered to use the concept ofr, including modern technology and current concerns.ess led to the invention of many new modern and com-

ndcatchers. For instance, University of Qatar in Dohad a brand new type of simple windcatcher, which was

different with the existing vernacular windcatchers

O. Saadatian et al. / Renewable and Sustainable Energy Reviews 16 (2012) 1477 1495 1479

Fig. 4. N

Advanceholder mordifferent buwindcatcheadjustable introduced normally auhumidity, aupon the ncial windcalighting and

2.3. Super m

Combinitech instruto transcenFig. 3. Different forms of vernacular windc

ew type of windcatcher used in University of Qatar Doha [25].

ment of new technology has given the building stake-e opportunities to access to controlling options onilding components. For instance, a newborn type ofr which posses dampers, various types of sensors andceiling ventilator known as Monodraught has beento building industry. Monodraught windcatchers aretomatic and the mechanism allows the temperature,ir ow, noise level, and CO2 to be adjustable dependingeed of the space [17,25]. Some of this new commer-tchers incorporates both natural ventilation and natural

in an integrated, energy-free system (see Fig. 5) [31].

odern windcatcher

ng the concept of green life and accessibility to high-ments enabled the architects of the new millenniumd the conventional boarders. The Wind Catcher Tower

concept, a is an exampin an aerodto produce rotating plaright positioactivate thrventilation

Anotheral-Taqa or tower is eqpartially cathe needs ohydrogen fu

The ideaned to onwindcatcheCouncil Ho80% of ener

The techwhere ve wbuilding, cotanks are freeze at 15of coolers t

2.4. Windca

The numing a windcgroups of uthe wind fratchers.

suggested 125 oors tower which is designed for futurele of above statement. The form of this tower designedynamic form and can absorb the wind power and use it

electricity [33]. The proposed design foundation is on ate which enable the tower to orbit and move into then, where can catch wind and lead the wind to the top toee wind-generators and produce electricity for cooling,and other consumptions (see Fig. 6) [33].

example of super modern windcatcher is Dubais Burjthe Zero-Energy Tower in the Desert. This 322 m talluipped with a 60 m turbine installed on its roof which,ters for the needs of tower electricity [34]. The rests off this tower are provided using solar energy as well asel, which is supplied by catalyzing the sea water [34].

of utilizing windcatcher in building has not been con-ly the Middle East. There are numerous super modernrs installed in various buildings internationally such asuse 2 (CH2) in Melbourne Australia, which saves up togy needs [35] (see Fig. 7).nology behind this windcatchers is more sophisticatedindcatchers are installed in the southern facade of this

nnecting to three large tanks in the basement [35]. Largelled up with 10,000 phase change material balls, which C. This frozen balls can cool down the circulating waterhrough convection [35].

tcher with different opening

ber of opening is an important parameter in design-atcher. Generally, windcatchers are categorized in twonidirectional and bidirectional [36]. The former takesom the top inside and then the air is allowed to exit


Fig. 5. Sample of Modern commercial Monodraught [32].

from anothits top, let ithe lee side

The bidivertical axifour types directional,windcatche

Fig. Fig. 6. Wind Catcher Tower is a proposed design

er part of building, and the latter takes the wind fromt travel across the building and then up again through

of windcatcher [36].rectional windcatchers are normally divided into theirs. Ghaemmaghami and his colleague have reportedof windcatcher based on their opening namely: one

two directional, four directional and eight directionalrs (see Fig. 8).

7. Windcatchers used in Council House 2 in Australia [35].

Montazeof windcatcopening of sented thatas the numcatcher eftunnel andexamine thopening. for future [33].

ri and his colleagues based in Yazd city, known as cityhers, conducted a study to investigate the number ofwindcatcher and its efciency [29,37]. The study pre-

height, cross section and place of windcatchers as wellbers of opening are the rubrics that contribute in wind-ciency [37]. They further, utilized experimental wind

smoke visualization test as well as CFD simulation toe efciently of windcatchers with various numbers of

Fig. 8. Cross sectional of vernacular windcatchers [18].


ent opening [29].

The objebehavior ofmade ve ftwelve-sidenel and smopening nerate by eachstatic tubesdifferent ch

The winin the unifovelocities o2.5 increme

Becausecirculation entrance opcauses a nonpitot and stformula wa

Q =n

i=1Ai v

In this formis called Q aof portion istatic tubesof Montaze

Referrinof opening

ship of windcatcher with different opening and airow.

atcherType Wind angleDegree Rate of net air ow (m3/s)

Experiment CFD

pening 0 0.029 0.031pening 15 0.028 0.029pening 30 0.17 0.019pening 45 0.022 0.023pening 60 0.014 0.016pening 75 0.015 0.017pening 90 0.015 0.017opening 0 0.026 0.030opening 15 0.026 0.029opening 30 0.025 0.026opening 45 0.017 0.018opening 60 0.016 0.019pening 0 0.024 0.029pening 15 0.018 0.026pening 30 0.018 0.028pening 45 0.027 0.029ening 0 0.021 0.024

Table 1Details of angl

Windcatche

Two openingThree openinFour openinSix openingTwelve openFig. 9. Windcatcher models with differ

ctive of their study was to observe the hydrodynamic multi and single opening windcatchers. Therefore, theyollowing cylindrical models: two, three, four, six andd windcatcher (see Fig. 9). In conducting the wind tun-oke visualization test, the air ow rate through eacheded to be measured to gauge the net induced air ow

of the windcatchers. Accordingly, some stainless steel and sensitive tiny pitot were employed to measure theannels air ow rate [29].d tunnel and smoke visualization tests were conductedrm ow wind tunnel in the following three various windf 10, 15 and 20 m/s at different wind angles of 045 innts [29].

of separated ow phenomenon, and existence of azone of the incoming air stream which occurs at theenings and near the lower edge of the model, which-uniform ow inside of the windward openings severalatic tubes needed to be employed. Hence, the following

Table 2Relation

Windc

Two oTwo oTwo oTwo oTwo oTwo oTwo oThree Three Three Three Three Four oFour oFour oFour oSix ops used:

i (1)

ula, the ow rate passing the channel of the windcatchernd Ai is the area of the portion i and vi are the velocity

respectively. Table 1 presents the details of pitot and used at the upper and lower surfaces and wind anglesri study.g to Table 2, the result shows that adding the numberin windcatcher decreases the efciency [37]. There is

Six opening Six opening Twelve openTwelve open

a relationshinside the wthe highestthe effect oincrease [37a higher ind

e and Pitot tube used in the study of Montazeri.

r model Pitot tubeUp

Pitot tubeDown

Static tuUp

28 28 8 g 22 22 6

g 14 14 4 11 11 3

ing 7 7 2 15 0.027 0.02930 0.028 0.029

ing 0 0.025 0.026ing 15 0.027 0.027

ip between the wind angle and the induced air owindcatcher. For instance, a two-sided windcatcher has

air ow at zero wind angle [37]. Despite the above fact,f wind angle will decrease if the numbers of opening]. The study also showed that a rectangular device catchuced air ow for both one and two-sided systems [37].

be Static tubeDown

Wind directionDegree

8 0906 0604 0453 0302 015


l wind

The studopenings rethe windcatIn other wodirection, it

2.5. Shape o

In vernagular and ois reported catcher is ishafts [18]. ondary partthe groundthe latter reThe role of pshafts and ito satisfy th

Mahmooof windcatc(see Fig. 11

Even thonamic and his colleagutational uidifferent [3square winreason is thbig region a higher prefcient. Thing for a zerinduces air sided circul

wisee efndin16].

outurvedeprees thutionthere-shtion nditf sec

forcimed

with1]. Fowithls, 3ee Fiir sts thFig. 10. Different components of a norma

Fig. 11. Various plan cross sectional windcatcher [38].

y also concluded that although increasing the number ofduces the rate of induced wind and ventilation, it makescher less sensitive over different inclination angel [37].rds for the places which there are no prevailing wind

might be considered more suitable.

f windcatcher

Likegate thTheir Awbi [carriedwith cstudy rincreasdistrib

Anoventursimulaow coest roodrivingalso, aeratedroof [4set: 1-intervaroof (s

Theperformcular architecture, windcatchers had the square, rectan-ctagonal cross-section where the most prevalent shapeto be the square type [18]. One component of a wind-ts partition, which divides the main tower to variousThere are two types of partition namely; main and sec-itions where the former, starts from 1.5 to 2.5 m above

oor level, continue to the top of the windcatcher andmain as wide as the external wall, about 2025 cm wide.artition is not only to divide the windcatcher to smallerncrease the air motion cause of buoyancy effect but alsoe structural needs of windcatcher (see Fig. 10).di and her colleagues have reported three main formshers, which have 28 various cross sectional plan [38]).ugh circular windcatchers looks to be more aerody-

therefore, to be more efcient, based on Elmualim andes experimental investigations as well as his compu-d dynamics (CFD) simulations the result turns out to be9]. They found out that the performance of four-sideddcatcher is much higher than the circular one [39]. Theat sharp edges of the square windcatcher produce aof ow separation [39]. This ow separation imposesessure difference across the device and makes it moree above statement is in agreement with Montazeri nd-o angle wind direction, where a one-sided windcatcherinto the building almost four times more than the two-ar windcatcher [37].

the magnitThis phenoincreases thpart of the alate, whicheffect causeworse than

2.6. Windca

Damperin some wirate to repversity of testing in (0.50 m 0effects of eers efciennominal wicombining could be fo

In doingthe total prpressure tathe windwa

The stucrate grillecatcher [38].

, Liu and Mak used CFD modeling simulation to investi-ciency of a 500 mm square cross-sectional windcatcher.g also conrmed the mentioned result of Elmualim andWith regard of the form of windcatcher, Asfour et al.

a CFD simulation test on an integrated windcatcher roof to compare the result with the normal roof. Theirsented that the integrated windcatcher with curved roofe air ow distribution and improves the internal air

[40]. study conducted at Eindhoven university on theaped roof employing wind tunnel experiments and CFDusing steady RANS and the RNG k-3 model to analyze theions, focusing on the under pressure force in the narrow-tion [41]. This under pressure force is one of the maines of passive ventilation in buildings [42]. The study,

to assess the magnitude of the under pressures gen- different design congurations of the venture-shapedur following venture-shaped roof congurations wereout guiding vanes, 2- with guiding vanes at every 90-with guiding vanes at every 10 intervals and 4-normalg. 12).udy revealed that style of without guiding vanes out-e other styles [41]. This outperforming is in terms of

ude of the under pressure force in the roof contraction.menon stems from the fact that adding guiding vanese ow resistance. This ow resistance makes a largerpproaching wind ow not to pass through it and circu-

is called wind-blocking effect [41]. The wind-blockings the venture-shaped roof with guiding vanes performs

the conguration without venture shaped roof.

tcher with damper and egg crate grille

s and egg crate grilles are some devices that are usedndcatchers that assist the movement of large air owlenish of fresh air. Elmualim a scholar of the Uni-Reading in the UK employed a smoke visualizationwind tunnel on a four-square sections windcatcher

.50 m 1.5 m) and CFD simulation to examine thegg crate grill, damper and heat source on windcatch-cy (see Fig. 13). Three alternatives were studied undernd speeds of 0, 0.5, 1, 2, 3, 4, 5 and 6 m/s at one directionthe heat source and damper egg crate which its detailsund in Table 3.

this study, a pitot-static tube was employed to measureessures. The study team also xed internal and externalps to the windcatcher model both in the leeward andrd side to measure static and stagnation pressures.dy result revealed that use of the damper and egg

with the damper in fully open position decrease the


Fig. 12. Differno venturi-sha

ventilation.which reach20% when w

Likewisethe induce

Table 3Details of vario

Case numbe

12 3ent congurations and the reference conguration: (a and b) no guiding vanes (c and d) ped roof [41].

Fig. 13. Experimental device of Elmualim

The reduction of ventilation depends on the wind speedes to approximately 50% when wind blows 1 m/s andind blows 3 m/s respectively., damper and egg crate grille installation decreasesd wind ow to 71% of normal conguration at an

external wtion at aninstallationmetric air [15].

us setting.

r Wind direction Wind speed (m/s)

= 0 06 = 0 06 = 0 06 guiding vanes every 90; (e and f) guiding vanes every 10; (g and h)

[15].

ind speed of 3 m/s and 67% of normal congura- external wind speed of 1 m/s [15]. Finally, the

of the above device decreases the windcatcher volu-ow with an average pressure loss coefcient of 0.10

Damper egg crate Heat source

Does not exist Does not existDamper is completely open Does not existDamper is completely open 3 kW heater


ds of 1

Anothering an inteside, indicaand streama damper oareas which

3. Windca

In spite modern arcnegligent pof many moInland ReveDemon fortsystem to rdepends onation, i.e. dawindcatche

There areffects mainture [44]. Thinto the buiand evaporaremoving thet al. carriedinuential that windcspeed, chanand numbe

3.1. Wind a

WindcatHowever, wor need fastFor answeria study on twind speedall of those ptemperaturteam foundthermal comcirculation

andge rildind th46].ensivll scaes oratio

the re diersere hwo fmerther

ordany of amain

anwhse twcted ant ing een th]. Thel veFig. 14. Temperature effects and wind spee

study which was conducted in Hong Kong, simulat-grated building and a window positioned in lee wardted that in order to combat particle concentrationsing the distribution of airow, which is not uniform,r egg crated grill should be installed, particularly for the

have strong wind [7].

tcher technology

of that the utilization of windcatchers is ignored inhitecture, advancement of technology has affected thisositively in recent years. A prove of this claim is the usedern windcatcher elements in the UK itself, where thenue building in Nottingham, the Queens building at

University and many other buildings employed thiseduce their energy [15]. Operation of a windcatcher

some climatologic parameters such as the time of oper-y or night time, the availability of wind, and the type ofr system, i.e. hybrid or normal [43].e two main forces of wind and buoyancy, which itstain natural ventilation in this green architectural fea-is technology captures the external wind and induces itlding. This induced wind increases the both convectivetive inside heat [44]. It cools the inner part indirectly bye stored heat inside the building structure. Kolokotroni

out a study aiming to determine the driving forces andparameters behind this system. Their results showed

Kirkexchanous burevealewind [

Extand fuent typits opewhereperatuan imm

Thethese tthe forsome ofrom Jdensitas the [48].

Meof thecondusignicand Mbetwe[22,44internaatcher efciency is altered by changing outdoor windging temperature difference and changing the locationr of openings, like windows [45].

nd buoyancy effects

chers are generally dependent on wind to operate.hether windcatchers are functional under slow wind

wind to operate has always been a matter of question.ng this question Yaghubi and his colleagues carried outhree naturally ventilated public buildings with different

in Yazd. They learnt that windcatchers are functional inlaces even in low speed wind locations [23]. Measuringe, relative humidity and airow velocity, the research

out even in a calm weather, windcatcher can bringfort for dwellings by inducing certain volume of air

[23].

realized thaexternal ind

Their stuvide additioby 47% in cforce [44]. once there source to am

Anotheron a commlizing the bblower fan The result ocan easily abedroom h

The resudirection is and 3 m/s [15].

Kolokotroni conducted an experimental test using airate tests and tracer-gas decay method in three vari-gs, all of which equipped with windcatcher. Their studyat air exchange rates are directly related to speed of the

e investigations and several researches using the CFDle experimental tests have been conducted on differ-f windcatchers to determine the driving forces behindn. In fact, windcatchers need a driving force to operaterst force is buoyancy effect, which is due to the tem-fference [44]. This force is an upward force exerted ond particle [47]. The second force is external wind [44].as been a dispute between scholars on signicance oforces whereby some researchers were emphasizing on

force as the main medium of passive ventilation, ands on latter one. For instance, Bardan, an academician, has proposed buoyancy effect and the difference inir between the inside and outside of the windcatcher

force of passives ventilation in windcatcher structures

ile Kirk and Kolokotroni have proposed the effecto forces as equal [46]. However, Johns and Kriblyanother study resulted to the fact that buoyancy isonly at relatively slow wind [11]. Likewise, Hughesmployed CFD simulation to examine the relationshipe above two forces and the indoor ventilation ratey found out that the external wind provides 76% morentilation than buoyancy force [44]. In addition, they

t the effect of buoyancy is negligible once there is nouced airow.dy proposed that installing a window which could pro-nal external wind could increase the indoor ventilationomparison to the time of relying solely on buoyancyTheir study proved that the optimum velocity occursis a window to amplify wind effect and there is a heatplify buoyancy effect (see Fig. 14).

study conducted in University of Nottingham in the UKercial windcatcher known as Monodraught ABS550 uti-oth measurement system uses a cone ow meter and aas well as CFD simulation to investigate its efciency.f this study showed that such a modern windcatcherchieve an extract ow rate of 30 l/s to ventilate a three-ouse if there is an outdoor wind speed of 2 m/s [17].lt of the said study also indicated that the effect of wind

less than 20%. Likewise, a temperature difference of


Fig. 15. Use o

10 C amplithe wind spligible whestory for a cthe positiveby the nega

There alrelated to bing the air dinternal andto exit thromum and leinvestigatiolated low-plow-inducefunctions p

3.2. Heat so

Installattates the mstudy carrieresidents ofrelationshipsource such

Howeveshowed thawindcatchethat installawindcatche

incrf 1 mtallatnd sped eat so

wo [15]

e of

he P techan u

parte are effh the

[51,5e thepaces tecchiteir ogs. 1ectlynicalf evaporative technique in Iranian Vernacular Architecture [53].

es to air movement for the effect of buoyancy wheneed is less than 2 m/s, nonetheless, it is considered neg-n wind blows slower than 3 m/s [17]. There is a sameommercial wind vent whereby the fresh air is driven by

air pressure on windward side, exhausting air is driventive pressure on the leeward side [44,49].so exist a secondary force namely stack effect, which isuoyancy [22]. This stack effect is the result of decreas-ensity for increasing the temperature [16]. Hence, the

external temperature difference will force the airowugh the ventilator. Hughes and Ghani studied the mini-gislative requirement of wind, employing a numericaln in standard passive stack device geometry and a simu-owered axial fan. The study revealed that a minimum ofd pressure of 20 Pa is required to enable the windcatcherroperly [50].

urce

ion of one heat source inside any windcatcher facili-ovement of air ow due to buoyancy effect. Based on ad out by a group of scholars on the thermal comfort of

three buildings, it was revealed that there is a negative between thermal comfort and having a too strong heat

as strong solar radiation [23,43].r, the result of smoke visualization and CFD simulation

Thewind othe insat a wiextractwith hif thereof 8 C

3.3. Us

In tcoolinguse of gratedold-timthat ththrougmentsproducliving s

Thiular arinlet a(see Fiair dirmechat installation of a heat source affects the performance ofr in a positive way [15]. Likewise, the result indicatedtion of the heat source improves the performance ofr, particularly at lower wind speeds [15].

[55,56].Accordin

leagues, diclimate co

Fig. 16. Inducing air inside the water canal as a medium of eFig. 17. Use of pond in cooling the building.

ease of air velocity inside the windcatcher was 54% for a/s and 7% for a wind of 3 m/s respectively [15]. Moreover,ion of heat source increased the extract ow rate by 38%eed of 1 m/s [15]. In contrast, the heat source reducedow by 2% for wind speed of 3 m/s [15]. The windcatcherurce was found to be able to reduce temperature by 6 Culd be an external and internal temperature difference.

evaporative cooling

ersian Gulf architecture, use of water and evaporativenology has been employed for centuries. For instance,nderground water canal known as Qanat was an inte-

of the windcatcher design (see Figs. 15 and 16). Thosechitects were cooling down the buildings, knowingect of evaporative cooling occurs once the air passes

wet surface of the groundwater seeped inside base-2]. In those designs, natural downdraft is utilized to

necessary airow from the outside to the inside of the.hnique was not only used in the Persian Gulf vernac-cture, but also in Jordan and Egypt [12], where thews were passing along a water pond or canal to cool517). This technique employs water vapor to cool the

or indirectly and prevent installation of conventional cooling system which are both noisy and unsightlyg to a study conducted by Heidarinejad and his col-rect evaporative cooling is very conducive for multiuntries such as Iran. Based on their computation

vaporative technique [54].


simulation and long term meteorological measurements, this tech-nique provides comfort conditions for more than half of the Iranianpeople [13]. An Egyptian scholar claims, based on an experimentconducted, evaporative cooling is the most efcient method amongthe entire passive cooling methods in the world [57].

This technique can also reduce the temperature up to 10 C inarid areas [58]. Evaporative cooling has attracted many researcherssuch as Jiang. He and his colleague from Tokyo institute of Tech-nology invented a type of ceramic that has a capillary force to soakwater to more than one meter when the lower end of the ceramic isput inside a water pond [59]. Although, the evaporating techniqueis the very useful means to improve the efciency of windcatchers,it might not be very feasible for extreme humid climate once theissues of cost and benet are taken into the account [60].

Numerous studies have been conducted on utilization of evap-orative cooling in different segment of a windcatcher. For instance,altering the height of wetted column and size of the mass exchangeslocated at the middle of air and windcatcher walls was suggestedas a practicthe cooling revealed ththe top 2 moutlet temptemperatur

Althougthe fact is tsuch as Qanthis reasoncatcher deswithout eva

Their decatcher witwindcatchenumber onthe top. Thwere as higThe researctheir top. Oevaporativewetted by s

Doing thputer simuone and ththe convenconguratiowhereas cospeeds.

Kalantarmodeling uthat if the operates m

e of sus t

climptio

ybrid

advdcatchis cf thes kn(EB

[65]se arl sysntilahybrng mcorpplicag (se

buile winationratur

fromS operates the system under ve phases: phase 1: underg, raining, and wet fog circumstances or either the averageal dry bulb temperatures are outside of the range of 1425.8 C

system [66].al and efcient solution [12]. Likewise, in investigatingeffects of a fan-assisted evaporative windcatcher, it wasat more than (4/5) of the cooling effects is achieved at

of the windcatcher [12]. Besides, they realized that theerature is just 3 C higher than the ambient wet bulbe [12].h, evaporative cooling drastically cools down a building,hat the above traditional evaporative cooling methodsat and pond cannot t in the modern building easily. For

Bahadori and his colleagues proposed two new wind-igns, which can be incorporated in existing windcatcherporative cooling as well as modern building [61].sign had three following conguration: (A) the wind-h wetted column (B) traditional windcatcher and (C) ther with wetted surfaces (see Fig. 18). The conguratione was equipped with fabric curtains suspended frome space between fabric curtains was 10 cm, and theyh as windcatcher height exclusive windcatcher head.h team had the curtains wetted by spraying water onn the other hand, conguration number two was used

cooling pads made from leaves of plants, which werepraying water on top of them.e full experiment in two different sites as well as com-lation revealed that: both the conguration numbere conguration number two are more efcient thantional one [61]. The study result also indicated that then number 1 performs better with high wind speedsnguration number two is more efcient in low wind

conducted another study by doing the computationsing C++ program and experimental test, which revealedwalls of the wind tower is insulated, the windcatcherore efciently and less water will be consumed [43].

In spitconsenhumidconsum

3.4. H

Theof wintems. Tsome osystemsystem(IBMS)

Thecontroing, vethese shoppimall intive apbuildin

TheoperatInformtempemitted

IBMsnowinextern

Fig. 19. Inside and outside of hybridFig. 18. The new design of windcatcher [61].

that, all the above advantage, there has always been ahat the evaporative cooling is not very efcient for veryate without dehumidication, which bears more energyn [3,62,63].

commercial windcatcher system

ancement of technology triggered a change in the usehers in combination of active heating and cooling sys-ombination is called hybrid windcatcher system whichm requires installation of complex electrical controllingown as Energy management and building automationAS) [64] and integrated building management system.e electrical systems, which are literally computer-basedtems that monitor and control different cooling, heat-tion and other energy-related devices. An example ofid windcatcher is a shopping mall called Blue-waterall located near Kent city in the UK [66]. The shoppingorates 39 rotating modern windcatchers, as an innova-tion for passive ventilation in the UK, to ventilate thee Fig. 19).ding employs IBMS connected to a weather station todcatchers in conjunction with mechanical ventilation.

about occurrence of rain, speed and wind direction,e and relative humidity and snow or wet fog is trans-

weather station to IBMS.


or average the IBMS wlation will b1 m/s for a cventilation.all 39 windexternal wiof the windthe thermathen an alacal ventilatisummer anindoor air qrange [66].

3.5. Windca

Conventand semi-euse of windare expertsbased on Mby Europeacatcher for summer cli

They inscreate an acfort (see FigFig. 20. Details of the project [67]

external wind speed is outside of the range of 17 m/s,ill deactivate the windcatchers and mechanical venti-e employed. Likewise, if average wind speed is belowouple of consecutive 20 min, IBMS will run mechanical

Phase two: wind speed is between the range of 13 m/s,catchers will be utilized. Phase three: If the averagend speed is between 3 and 7 m/s, IBMS uses only 19catchers; and nally phase four: the sensors show thatl comfort indices exceeds the desired set point range,rm noties the relevant authority to use the mechani-on. This system has shown an acceptable result both ind winter whereby based on the study of Elmualim theuality parameters were recorded within the desired

tcher for outdoor

ional windcatchers is normally designed for enclosednclosed area, nonetheless, the idea of expanding thecatcher to outdoor has attracted some researchers who

in this realm of study. For instance, a group of scholarsadrid, Spain, started a project, and nancially supportedn commission, to examine the use of evaporative wind-outdoor urban space, i.e. a boulevard with hot and drymate.talled sixteen windcatchers in a circular arrangement totivity zone for pedestrians to gauge their thermal com-. 20). During their data collection, the research team

measured tity. They utthe therma

The studhumidity, iperate on avout that thefrom the graverage satstudy also pof evaporatand interesthe evapora

Anotherinstalled in due to buoywith some ent winds, In spite of tperformancducted by tcomfortabl

3.6. Down d

As far asnew techniqment of wi.

he solar radiation, temperature, wind speed and humid-ilized two indices of Heat index and TS index to forecastl comfort.y result, based on sensors of wind, temperature and

ndicated that the windcatchers has decreased the tem-erage 3.5 C in some places [67]. However, it was found

comfort level could have only been achieved in +1 mound in the pedestrian zone [67]. In that position, theurated cooling efciency is approximately 32% [67]. Theroved that windcatcher not only cools down becauseive effect but also for the windcatchers shading effectstingly the effect of shading is more than the action oftive systems [67].

example of windcatcher for outdoor is a windcatcherMasdar city in Abu Dhabi to induce a convection currentancy effect (see Fig. 21). This windcatcher is equippedadjustable louver that can be changed based on differ-and it aimed to be able to cool the area up to 5 C [68].hat, no scientic report was found with regard to thee of this windcatcher. According to the interview con-he users of that zone, the users were feeling thermallye in 4 months of the year in the mentioned area.

raft windcatcher

the technology gets more high-tech in general terms,ues and initiatives are also being introduced in employ-

ndcatcher as a cooling and ventilation medium. Down


asdar City [68].

draft windctives whichsemi disclo[36,58,60,6

This typprincipals: the windcawindcatche(3) there ismove the a

The advthe air all theffect creatcatcher migsupplying wair inside thair exits at t

Pearlmuthe down dstage to imondary air idraft windcTherefore, tthe device ewater sprayof the towe

The studblown throLikewise thof conservinsemi enclosis achieved

4. Windca

Conguris one of ththat particuparameter conguratio

4.1. Inclina

The relaalways beeFig. 21. Windcatcher for outdoor -M

atcher, an innovative design, is one of these new initia- utilizes the evaporative cooling phenomenon for vast orsed areas such as courtyards, particularly in arid regions9].e of windcatcher, operates based on three following(1) there is a positive wind presser at the entrance oftcher or inlet; (2) the spray of the water at the top ofr causes the air to descend since it became denser; and

a momentum transferred from the sprayed water toir downward [58].antage of this kind of windcatchers is that it circulatese time even in the absence of wind due to the buoyancyed by evaporative cooling [58]. A down draft wind-ht have a different shape as well as uses various type ofater for evaporation but generally draws dry ambientrough a single inlet located at the top and cooler moisthe bottom part (see Figs. 22 and 23).tter and his colleagues invented a new prototype ofraft evaporative windcatcher which functions in multiprove the single stage design by incorporating a sec-nlet [58]. They aimed to make the conventional dawnatchers more efciently in terms of water consumption.hey incorporated a secondary air intake at the middle ofquipped with a high-tech water spraying system. Thising system had a very low spray drift beyond the baser, to reduce maintenance costs.y result revealed that the proportion of second airugh the secondary inlet is drastically substantial [58].is system was recognized to be highly efcient in terms

g water and suggested as a practical passive solution fored spaces [58]. The maximum efciency of this system

if a very ne spray is being employed. [58].

tcher conguration

ation of the different components of a windcatcherse important parameter determining the efciency oflar windcatcher. Inclination angle and meteorologicaland louver conguration are some examples of thesens which are going to be discussed in this section.

tion angle and meteorological parameters

tionship of meteorological factors and ventilation hasn the focus of various researchers. Geometry and

Fig. 22. S

inclination instance, Cscholars frochimney in

The resfor a 1.5 mfari and hian experimto examine[29].

For thatinduced voentation ofchematic design of multi stage down draft windcatcher [36,58].

angle is the main rubrics of this realm of study. Forhen from Australia in collaboration with some otherm Denmark and Hong Kong carried out a study on solarclinations to determine the optimum inclination [70].ult showed that the most efcient inclination angle

high device is around 45 [70]. Likewise, Moza-s colleagues conducted a CFD simulation as well asental wind tunnel utilizing smoke visualization test

the inclination of windcatcher and its efciency

a windcatcher model was examined to measure thelumetric airow and the pressure coefcients. The ori-

the constructed model was changed in wind tunnel


Fig. 23. the multi stage windcatcher prototype [36,58].

and CFD simcoefcientsof windcatcand air inci

Measurinomenon kmulti openexhausts frafrmed thrate of shorhaving the

4.2. Louver conguration in commercial windcatcher

A louver in a windcatcher induces external wind into the build-ing and safeguards the building from penetration of the rainwater.The louver is considered functional once the ow separation hap-pens over the top surface of the louver airfoil. Based on aerodynamictheory when the angle of the airfoil of a louver namely attack angle,reaches to a certain point ow separation occurs [72].

The parameters that are determinant in efciency of louvers areits geometry, louver angle, surface roughness, the void between twolouvers, and the sharpness of the edges as well as Reynolds num-ber [73]. Reynolds number is a dimensionless number that gives ameasure of inertial force and for the realm of the study of buildingis calculated as follows: Re = UL/v, U = wind speed, L = length scaleof louver and v = kinematic viscosity of air [74].

There has always been a question that how much the wind-catcher louver quality contributes the performance of windcatcher.For answering this question, Hughs and his colleague from ShefeldHallam University in the UK explored the efciency of the windvent, a kind of commercial windcatcher, and the external angle oflouver.

Despite the fact that a normal windcatcher louver has a 45

angled louver, no one had conducted any research on suitability ofthese louvers (see Fig. 25). Therefore, the research team made eightCFD models using FLUENT version, including various windcatchersaltered in 5 increments for a range of 1045 louver [73]. They con-secutively measured the air velocity and pressure to investigate theoptimum angle of the louvers.

The result showed that a louver angle of 35 has the maximumcy [73]. Moreover, in terms of comfort level of occupants, andcatcher louver produces 45% more comfort in comparisoner witall panwhUniv

and R invelouved purulation and the volumetric airow, and the pressure were measured. The study found out that the efciencyhers is related to the pressure coefcients of its openingdent angle [71].ng these pressure coefcients revealed a new phe-nown as short-circuiting. This phenomenon occurs oning windcatchers once wind enters from one side andom the other side without circulation [71]. The studyat the worst inclination angle for having the highestt-circuiting is 60 whereas the most efcient angle forhighest ventilation rate is 90 [71] (see Fig. 24).

efcien35 wiof louvedge s

Menique modeltion toof the the saiFig. 24. Efciency and incantation angleth angle of 45, and the former one reduces 42% trailing-ressure produced.ile, another group of scholars at Hong Kong Poly Tech-ersity focused on louver effects. They employed kNG k model, wind tunnel and eventually CFD simula-stigate the effects of the number of layers and the lengthrs and its relevancy to windcatcher efciency [7]. Forpose, a square cross-section windcatcher was mounted

[71].


Fig. 25. Standard 45 louver [73].

on a typical room. For having a fair comparison the researchers usedthe dimensions of the windcatcher and the room of the Hughs study[73], nevertheless the length and number of layers were altered [7].

In order to make the experiment feasible, the external windvelocity and wind incidence angle were hypothesized 3 m/s, and( = 0) respectively [7]. Moreover, to avoid any bias cause ofchange of louver angle, as a signicant parameter in efciency of

windcatcher, the uniform louver external angle (45 C) wasemployed. For studying the effects of layers of louvers, seven vari-ous models with the same louver length and external angle, namelylouver 2, 3, 4, 6, 8, 10, 12, were analyzed.

In spite of that various models had diverse layers; the heightand gap of two adjacent layers were considered exactly the same.A length ratio l L/Lref to evaluate the effect of the louver lengthwas also applied where L is the nominal length of louver, whileLref is the louver length when the dimension of louver projectionequates L gap. The length ratios of 0.5, 1, 2, 3, 4, 5, 6, were simulatedusing CFD modeling in their study.

The study revealed that increasing the number of louver layerscontributes to more efciency (see Fig. 26). For instance, the airowrates of three layers were shown 12.7% more than two louver layers[7]. In spite of that adding louver layers, increases the air ow rate,the study result ascertained that surpassing 6 louver layers, theincrease of the airow would be less than 1.5% [7].

Increase of the airow rate which leads to higher pressure resis-tance; prevent the wind to enter the windcatcher with six louversand above. Moreover, the existence of a short circuit at the top lay-ers of the windcatchers prevents the wind to enter the windcatcherwith six louvers and above either [7]. This phenomenon could beeasily observed in the airow pattern in, and around the wind-catcher with 12 layers, where the wind enters the 12-layer louversthrough the lower louvers and exit from other louvers [7].Fig. 26. The efciency of windcatcher and number of louver layers [7].


The studrate passession of louvof two adjac[7]. Howevecatcher is rLref [7].

4.3. Window

An engipotential rements. Engenvelope nFor investigwindcatcheHong Kong ventilation

They aimposition, leetions of thelights and foTable 4).

They setCase 1: NoFig. 27. Contaminant concentration modeling in

y also revealed that when L = Lref the highest air ow through the windcatcher [7]. Moreover, if the dimen-er projection is equivalent as the dimension of the gapent louvers, the windcatcher will work more efcientlyr, the airow rate goes down and the efciency of wind-educed once the length coefcient become double the

s conguration

neering positioning of windows is proposed as themedy to cool the buildings in dense urban environ-ineering designed windows are used in the buildingot only to draw wind but also to expel the air [75].ating the effects of windows positioning in relation tor efciency such as buoyancy, a group of scholars inconducted a study by selecting four cases with differentstrategies in a full-scale ofce [7].ed to investigate the effects of buoyancy and windowward sides and windward side, on the thermal condi-

ofce. Heat sources in a format of two computers, fourur persons, were provided to foster the stack effect (see

four combination forms with following specications: buoyancy and no windows; Case 2: With buoyancy

Table 4Heat sources d

Heat source

First personSecond persFirst compuSecond comBulb1Bulb 2 Bulb 3 Bulb 4

effect but nare installewindows ar

Meanwhers of louveupheld thatthere is a siing to other

In contrshort circuthrough thefrom the wifore, the wo Cases 14 [7].

etails [7].

Dimension (m) Heat input (W)

0.4 0.35 1.1 75on 0.4 0.35 1.1 75ter 0.35 0.34 0.4 173puter 0.35 0.34 0.4 108

0.2 0.15 1.2 340.2 0.15 1.2 340.2 0.15 1.2 340.2 0.15 1.2 34

o windows; Case 3: with buoyancy effect and windowsd in wind ward; and Case 4: with buoyancy effect ande installed at lee ward side.ile, an 80 cm 80 cm 150 cm windcatcher with 6 lay-rs is installed at the center of the ofce roof. The result

when the window is positioned on the windward side,gnicant positive difference in airow pattern compar-

cases (see Fig. 27).ast, positioning the windows in windward amplify theit phenomenon, since the wind enters the building

windward windows and immediately leaves the roomndcatcher which functions only as an out let [7]. There-rse conguration between Cases 3 and 4 which is not


Table 5Airow rate fo

Case numbe

1 2 3 4

propitious fside in an inthe best conside windowlee ward sidoutside (see

Referrinforms almoeffect of buparison to wtime more tFig. 28. Airow pattern (a) Case 1, (b) Case 2, (c) Cas

r various congurations.

r Air ow rate (m3/h)

1560156555702310

or ventilation is to position windows in the windwardtegrated windcatcher and windows building. However,guration in a above building is appeared to be leewards (Case 4), in which negative pressure generated on thee causes induction of extra wind into the room from the

Table 5).g to Table 5, the study represent that Cases 1 and 2 per-st the same and have the equal airow rate since theoyancy, not to say is negligible, is much lower in com-ind effect and the airow rate of Case 4 is almost 1.5han both Cases 1 and 2 [44].

This stuinant dispeas dp = 1 concentratisimulator aalso revealeconcentrati

Investigtioned on tfound in Caare almost ing an intecontributesforms the b

4.4. Combin

Solar apadvantageslong life spae 3, (d) Case 4 [7].

dy also investigated the particle diffusion and contam-rsion in the simulated building. Using particle as bigm, 2.5 m, 5 m and 10 m showed that the particleon (kg/m3) in the center position between the humannd computer for Case 1 is more than Case 2 [7]. The studyd that the windcatcher managed to reduce contaminanton of the central region drastically [7].ating Case 3 showed that when the window is posi-he windward side, less contaminant concentration isse 3 compared to Case 1 and the air of windows areaas clean as outside (see Fig. 28). Case 4 shows that hav-grated windcatcher with leeward positioned windows

a lot in removing the contamination and therefore, per-est [7].

ation of windcatcher and solar chimney

plications are attracting many people to use for their such as their economic benets, low maintenance andn in one hand and their systems modularity, low noise


Fig. 29. A combined windcatcher and solar chimney [43].

level in anothose benemethod andof air heateIn simple wtemperaturchimney an

The parachimney artransmittanfor integratto form thebined with tresearcherswindcatcherate [43,58]

The usemight be thtesting thisexperimentand solar ch

The resubined withtemperaturunder the wsectional arthan 100 kW

Fig. 30. Average extraction air ow rate based on external wind speed [80].

said system can easily do the air-conditioning of 700 m2 buildingin an arid area [43].

There are also another study, which emphasizes on the ef-ciency of integrated solar chimney and windcatcher. Based on the

condt fores a himn

of tdy ar opepeed

mbin

authcatchcal d

genee Fi

rood aice los expr capte sunts.

ma

ougry hather hand [76]. Solar chimney is also not exempted fromts. Solar chimney or thermal chimney is a ventilation

a thermo-siphoning air channel that uses convectiond by solar energy through thermal buoyancy [77,78].ords, this channel uses solar radiation to enhance thee leads to density drop and rise of air within the solard eventually to expel the air outside [78].meters that are involved the performance of a solare solar absorptance, solar chimney height, and solarce and air gap width [78]. It is argued that the best roofing solar chimney is a gable roof which can be designed

roof solar collectors [77]. Studies on windcatcher com-he solar chimney which has been carried out by various

indicates that the combination of solar chimney andr works more efciently since it increases the mass ow.

of solar chimney in combination with windcatchere solution when there is not a suitable wind [28,79]. For

hypothesis Kalantar conducted a simulation study andal measurement on the combination of a windcatcherimney to examine the efciency (see Fig. 29).lt of this study revealed that this solar chimney com-

the windcatcher cooling system can alter the aire up to 15 C cooler [43]. The study also afrmed thatind velocity of 3 m/s, a 10 m windcatcher with a cross-ea of 2 m2 could produce a peak cooling output of more, whilst it consumes only 0.025 kg/s water [43]. The

study out thaproducsolar cair owThe stucatchewind s

4.5. Co

Thea windempiriable to[80] (s

Theinverteto indu

Thicatchegeneraoccupa

5. Sum

AlthindustFig. 31. Experimental house with an inverted airplane wucted in Indian Institute of Technology, it was found an ambient wind of 1.0 m/s, an individual windcatchermass ow rate of 0.75 kg/s, nonetheless, the integratedey and windcatcher produce approximately a doublehe former one amounting to 1.4 kg/s at 700 W/m2 [79].lso revealed that a combined solar chimney and wind-rate more efciently in lower wind speeds than higher

[79].

ation of windcatcher and inverted airfoil

ors of this paper conducted an empirical research ofer under hot and humid climatic conditions. Based onata, at external wind speed of 2 m/s, the wind tower iserate average extraction air ow rate of 47,634.6 m3/hg. 30).f prole of the windcatcher is designed based on anrplane wing shaped roof which uses Bernoullis effectw pressure at the top of the wind tower (see Fig. 31).erimental research revealed the potential of wind-ability under hot and humid climatic conditions tofcient air ow rate for indoor thermal comfort for its

ry

h incorporation of windcatcher in modern buildings been neglected, windcatcher is still considered as oneing windcatcher [80].


of the most important passive techniques. Windcatchers can becategorized into three groups of vernacular windcatchers, modernwindcatcher and eventually super modern windcatchers.

There are two main driving forces behind the mechanism ofwindcatchelatter is theeffect is a ptence of inopening in much as thHowever, inis multi ope

Form of to its efcieweaker thaangle of a wwind is anoinclination the worst ithe highest

Louver cof a windcmore efciever angel iswind directalso suggesing equippebut also red

Damperto 71%, depmovement a heat sourair ow dueto 1.5 timesas well as pwind towereither.

Evaporaof the variocan alter thits applicabter of a quas Qanat anwater and face in motechnique.

Down dwhich utilizenclosed aroperates baitive wind (2) the sprair to descetum transfeThis kind oabsence of tive coolingThe maximbeing empl

The ideaenvironmencountries suciency of inis being incstill be cons34 C for s

Hybrid windcatchers are the one which are working in combina-tion of mechanical cooling and ventilation systems. This initiativeis very useful and innovative, which conserves a lot of energy butrequires a very high-tech electrical controlling system to operate.

mbinindcaned sratur

invee forerma

omm

dyingidiic oflor oired dy ogs, fmenhybrt of inomreses th

in s

nces

hlia TMnomylaysiasoso O. Enern H-Yogies.

Y-C, parisural-vldingsava P,s. Solayent-Fl of thctice a

S, Mation s1;46:, Coo

in a7;42:n N, S

Buildka Cent de7;14:es BMon Wichahm

use odarins kind8;40:adorin Jourualimon pe, Mak puta

Y, Riffae of a Maemmian trrgy Cr, namely buoyancy effect and external wind, where the main contributor of windcatcher operation. Buoyancyhysical phenomenon that is promoted due to the exis-ternal and external different temperature. Number ofa windcatchers affects its efciency in a way that ase number of opening increases its efciency decreases.

places that there is no prevailing wind the best optionning windcatchers.the windcatcher is also another attributes contributingncy where performances of octagonal windcatchers aren square and rectangular cross-section ones. Inclinationindcatcher orientation in relationship to the prevailingther important parameter of efciency where the 60

angle for having the highest rate of short-circuiting isnclination whereas the most efcient angle for having

ventilation rate is 90.onguration is another rubric that alters the efciencyatcher, i.e. as much as the layer of louvers increasesncy would be achieved. Likewise, the optimum, lou-

proposed 35 for the places which have a prevailingion. The optimum location for positioning windows isted the leeward side. Positioning a window in a build-d with a windcatcher not only foster the ventilation rateuce contaminant concentration inside a building.s and egg crate grilles generally reduce the efciency upending to the speed of wind. However, they assist theof large air ow rate to replenish of fresh air. Installationce inside the windcatcher facilitates the movement of

to buoyancy effect and increases the air movement up. Preventing the air from leaving from other openingsreventing dust and birds from entering the inlet of the

can be achieved by using a dampers and egg crate grills

tive cooling technique, either direct or in-direct, is oneus techniques, which is utilized in windcatcher ande temperature 10 cooler in the arid areas. However,ility for extreme hot and humid climate is a mat-estion. Use of the underground water canal knownd water pond in traditional architecture and spry ofutilizing new material, that can maintain wet sur-dern architecture are some of the examples of this

raft windcatcher is an innovative type of windcatcher,es the evaporative cooling phenomenon for vast or semieas such as courtyards, particularly in arid regions andsed on three following principals: (1) there is a pos-pressure at the entrance of the windcatcher or inlet;ay of the water at the top of windcatcher causes thend since it became denser; and (3) there is a momen-rred from the sprayed water to move the air downward.f windcatcher is unique which can operate even in thewind due to the buoyancy effect created by evapora-

and is highly efcient in terms of conserving water.um efciency of this system is achieved if a ne spray isoyed.

of using the windcatcher for semi-closed and outdoort has been practiced by some researchers in variousch as Spain. However, it has not shown the same ef-door. Despite its low efciency, if evaporative coolingorporated and considering its shading efciency, it canidered an option which can reduce the temperature byemi-enclosed zones.

The coand wcombitempetion ofclimatand th

6. Rec

Studehumdynamand cois requet stubuildingovernrating a resulthe ecofuture towardgauged

Refere

[1] MaecoMa

[2] Mause

[3] Chanol

[4] WucomnatBui

[5] Karysi

[6] JuntroPra

[7] Liutila201

[8] Ji Ytion200

[9] Khaand

[10] Canrec200

[11] Jonlati

[12] Bouthe

[13] Heiiou200

[14] Bahica

[15] Elmlati

[16] Li Lcom

[17] Su rat

[18] GhIranEneation of different passive tools such as solar chimneytcher is also recommended for its efciency where aolar chimney and windcatcher can serve to reduce thee up to 15 and double the internal air ow. A combina-rted air foil and a windcatcher is suggested for tropical

its efciency in improving the internal air movementl comfort.

endation for further studies

on the height, various materials, employment ofcation and evaporative cooling for humid climates, aero-

windcatchers, use of phase change material, structuref windcatcher are among the engineering topics, whichto be covered in future studies. Moreover, cost and ben-f windcatchers in newly built and existing renovationeasibility study of introducing windcatchers to existingtal and private buildings, analyzing the cost of incorpo-id windcatcher and the revenue which can be gained asts energy saving for a specic period of time are amongic subjects which should be studied thoroughly in thearches. Finally, the public attitude and their preferenceis passive technology for different countries should beocial science.

I, Saidur R, Memon LA, Zulkii NWM, Masjuki HH. A review on fuel standard for motor vehicles with the implementation possibilities in. Renewable and Sustainable Energy Reviews 2010;14:30929.T, Grobler LJ. The dark side of occupants behavior on building energygy and Buildings 2010;42:1737., Riffat SB, Zhu J. Review of passive solar heating and cooling tech-

Renewable and Sustainable Energy Reviews 2010;14:7819.Yang A-S, Tseng L-Y, Liu C-L. Myth of ecological architecture designs:on between design concept and computational analysis results ofentilation for Tjibaou Cultural Center in New Caledonia. Energy and

2011;43:278897. Stathopoulos T, Athienitis AK. Wind-induced natural ventilation anal-r Energy 2007;81:2030.erre Gomis-Bellmunt O, Sumper A, Sala M, Mata M. Modeling and con-

e doubly fed induction generator wind turbine. Simulation Modellingnd Theory 2010;18:136581.k CM, Niu J. Numerical evaluation of louver conguration and ven-trategies for the windcatcher system. Building and Environment160016.k MJ, Hanby V. CFD modelling of natural displacement ventila-n enclosure connected to an atrium. Building and Environment115872.u Y, Riffat SB. A review on wind driven ventilation techniques. Energyings 2008;40:1586604.ilik F, Durmus K. Energy production, consumption, policies andvelopments in Turkey. Renewable and Sustainable Energy Reviews117286., Kirby R. Quantifying the performance of a topdown natural venti-ndcatcher. Building and Environment 2009;44:192534.

Y, Bourbia F, Belhamri A. Performance analysis and improvement off wind tower in hot dry climate. Renewable Energy 2010;36:898906.ejad G, Heidarinejad M, Delfani S, Esmaeelian J. Feasibility of using var-s of cooling systems in a multi-climates country. Energy and Buildings194653.

MM. Passive cooling systems in Iranian architecture. Scientic Amer-nal 1978;2:14454.

AA. Effect of damper and heat source on wind catcher natural venti-rformance. Energy and Buildings 2006;38:93948.CM. The assessment of the performance of a windcatcher system usingtional uid dynamics. Building and Environment 2007;42:113541.t SB, Lin Y-L, Khan N. Experimental and CFD study of ventilation owonodraughtat windcatcher. Energy and Buildings 2008;40:11106.

aghami PS, Mahmoudi M. Wind tower a natural cooling system inaditional architecture. In: International Conference of Passive and Lowooling for the Built Environment, (palenc). 2005. p. 716.


[19] Mazidi M, Dehghani A, Aghanaja C. The Study of the airow in wind towers forthe old buildings air conditioning. In: The 4th WSEAS International Conferenceon Fluid Mechanics. 2007.

[20] Sharples S, Bensalem R. Airow in courtyard and atrium buildings in the urbanenvironment: a wind tunnel study. Solar Energy 2001;70:23744.

[21] Karakatsanis C, Bahadori MN, Vickery BJ. Evaluation of pressure coefcients andestimation of air ow rates in buildings employing wind towers. Solar Energy1986;37:36374.

[22] Hughes BR, Chaudhry HN, Ghani SA. A review of sustainable coolingtechnologies in buildings. Renewable and Sustainable Energy Reviews2011;15:311220.

[23] Yaghoubi MA, Sabzevari A, Golneshan AA. Wind towers: measurement andperformance. Solar Energy 1991;47:97106.

[24] Battle McCarthy Consulting E. Wind towers: Academy Editions; 1999.[25] El-Shorbagy A-M. Design with nature: windcatcher as a paradigm of natural

ventilation device in buildings. International Journal of Civil & EnvironmentalEngineeri

[26] Ford B. PaArchitect

[27] Gadi MB.cept). App

[28] Nouanegesystems f

[29] Montazerof one-sid

[30] Bahadoriarid regio

[31] Oakley G2000;69:

[32] Monodra[33] EVOLO. W[34] Oxford-B[35] Council-H[36] Erell E, P

tower fo2008;82:

[37] Montazerformance2010;46:

[38] Mahmoowindcatc

[39] Elmualimmance of2002;1:5

[40] Asfour, Ocurved roEngineeri

[41] van Hoofwind-indation of d1797807

[42] Givoni B. [43] Vali K. Nu

in hot and[44] Hughes B

commerc[45] Kolokotro

ventilatioEnergy Co

[46] Kirk S, Kostudy. Int

[47] Sparrow ow and1962;5:5

[48] Badran AAand Build

[49] PapanikoHySafe Srally vent2010;35:

[50] Hughes Bassisted nEnergy 20

[51] Oliver P. principle

[52] Ghiaus C, Allard F. Natural ventilation in the urban environment: assessmentand design: Earthscan; 2005.

[53] Motiee H, McBean E, Semsar A, Gharabaghi B, Ghomashchi V. Assessment ofthe contributions of traditional Qanats in sustainable water resources manage-ment. International Journal of Water Resources Development 2006;22:57588.

[54] Mostafaeipour A. Historical background, productivity and technical issues ofqanats. Water History 2010;2:6180.

[55] Spanaki A, Tsoutsos T, Kolokotsa D. On the selection and design of the properroof pond variant for passive cooling purposes. Renewable and SustainableEnergy Reviews 2011;15:352333.

[56] Giabaklou Z, Ballinger JA. A passive evaporative cooling system by natural ven-tilation. Building and Environment 1996;31:5037.

[57] Emad HA. Passive options for solar cooling of buildings in arid areas. Energy2006;31:133244.

[58] Pearlmutter D, Erell E, Etzion Y, Meir IA, Di H. Rening the use of evaporation inan experimental down-draft cool tower. Energy and Buildings 1996;23:1917.

J, Hoyling wlding a ACSh dire6;12:adoriigns orides Gling te2;6:5u K, We and stfall ss; 20

M, We energearchualimd catc

2006tullo door sment er N. Idit; 2ion Y,-enerctionn ZD,erime. Builntazerance

ewabghtonterwoghes Bver exironmtamochida

airormal 5;93:Karaghtovoli XQ, ldings

KH, Srmal csal Ner sy4;29:

CH, Sind is. 9thelopmss.ng 2009:10.ssive downdraught evaporative cooling: principles and practice. ARQural Research Quarterly 2001;5:27180.

Design and simulation of a new energy conscious system (basic con-lied Energy 2000;65:34953.ue HF, Alandji LR, Bilgen E. Numerical study of solar-wind toweror ventilation of dwellings. Renewable Energy 2008;33:43443.i H, Azizian R. Experimental study on natural ventilation performanceed wind catcher. Building and Environment 2008;43:2193202.

MN. Viability of wind towers in achieving summer comfort in the hotns of the middle east. Renewable Energy 1994;5:87992., Riffat SB, Shao L. Daylight performance of light pipes. Solar Energy8998.ught. Monodraught San Francisco; 2010.ind Catcher Tower. evolo-Architecture Magazine; 2008.

usiness-Group. The Report: Dubai Oxford Business Group; 2008.ouse-2. CH2 building Melbourne City of Melbourne; 2010.earlmutter D, Etzion Y. A multi-stage down-draft evaporative coolr semi-enclosed spaces: aerodynamic performance. Solar Energy4209.i H. Experimental and numerical study on natural ventilation per-

of various multi-opening wind catchers. Building and Environment3708.di M, Modi S. An analytical approach on architecture typology of Yazdher. Journal of Fine Art Tehran University 2008;3:2736.

AA, Awbi A. Wind tunnel and CFD investigation of the perfor- windcatcher ventilation systems. International Journal of Ventilation364.mar S, Gadi, Mohamed B. Effect of integrating wind catchers withofs on natural ventilation performance in buildings. Architecturalng and Design Management 2006;2:289304.f T, Blocken B, Aanen L, Bronsema B. A venturi-shaped roof foruced natural ventilation of buildings: wind tunnel and CFD evalu-ifferent design congurations. Building and Environment 2011;46:.Passive and low energy cooling of buildings. John Wiley & Sons; 1994.merical simulation of cooling performance of wind tower (Baud-Geer)

arid region. Renewable Energy 2009;34:24654.R, Cheuk-Ming M. A study of wind and buoyancy driven ows throughial wind towers. Energy and Buildings 2011;43:178491.ni M, Ayimomitis A, Ge YT. The suitability of wind driven naturaln towers for modern ofces in the UK: a case study. World Renewablengress; 2002.lokotroni M. Windcatchers in modern UK buildings: experimentalernational Journal of Ventilation 2004;3:6778.EM, Minkowycz WJ. Buoyancy effects on horizontal boundary-layer

heat transfer. International Journal of Heat and Mass Transfer0511.. Performance of cool towers under various climates in Jordan. Energyings 2003;35:10315.laou EA, Venetsanos AG, Heitsch M, Baraldi D, Huser A, Pujol J, et al.BEP-V20: numerical studies of release experiments inside a natu-ilated residential garage. International Journal of Hydrogen Energy474757.R, Ghani SA. A numerical investigation into the feasibility of a passive-atural ventilation stack device. International Journal of Sustainable11;30:193211.Encyclopedia of vernacular architecture of the world: Theories ands. Cambridge University Press; 1997.

[59] He cooBui

[60] Silvwit200

[61] Bahdes

[62] Flocoo200

[63] Daoabl

[64] WePre

[65] HuingRes

[66] Elmwinties

[67] Sououtron

[68] AstPun

[69] Etzlowstru

[70] Cheexpux

[71] MoformRen

[72] HouBut

[73] HulouEnv

[74] San[75] Mo

lingthe200

[76] Al-pho

[77] Zhabui

[78] Leethe

[79] Bantow199

[80] Limof wtiondevpreano A. Experimental study of cooling effects of a passive evaporativeall constructed of porous ceramics with high water soaking-up ability.and Environment 2010;45:46172.BD, Neto JABDC, Lamberts R. Building thermal performance simulationct evaporative cooling by water spray vaporization. HVAC&R Research66992.

MN, Mazidi M, Dehghani AR. Experimental investigation of newf wind towers. Renewable Energy 2008;33:227381.A, Tassou SA, Kalogirou SA, Wrobel LC. Review of solar and low energychnologies for buildings. Renewable and Sustainable Energy Reviews5772.ang RZ, Xia ZZ. Desiccant cooling air conditioning: a review. Renew-

Sustainable Energy Reviews 2006;10:5577.L. The Certied Software Quality Engineer Handbook. ASQ Quality08.ir JD, Wu T. Decentralized operation strategies for an integrated build-y system using a memetic algorithm. European Journal of Operational

2011;217:18597. AA. Failure of a control strategy for a hybrid air-conditioning andhers/towers system at Blue water shopping malls in Kent, UK. Facili-;24:399411.S, Olmedo R, Sanchez MN, Heras MR. Thermal conditioning for urbanpaces through the use of evaporative wind towers. Building and Envi-2011;46:25208.n: Boynton, editor. Masdar Citys Wind Tower: Literally Cool. Triple011.

Pearlmutter D, Erell E, Meir IA. Adaptive architecture: integratinggy technologies for climate control in the desert. Automation in Con-

1997;6:41725. Bandopadhayay P, Halldorsson J, Byrjalsen C, Heiselberg P, Li Y. Anntal investigation of a solar chimney model with uniform wall heatding and Environment 2003;38:893906.i H, Montazeri F, Azizian R, Mostafavi S. Two-sided wind catcher per-

evaluation using experimental, numerical and analytical modeling.le Energy 2010;35:142435.

EL, Carpenter PW. Aerodynamics for engineering students.rth-Heinemann; 2003.R, Ghani SAAA. A numerical investigation into the effect of Wind ventternal angle on passive stack ventilation performance. Building andent 2010;45:102536.

uris M. Advances in passive cooling. Earth scan 2007.A, Yoshino H, Takeda T, Kakegawa T, Miyauchi S. Methods for control-w in and around a building under cross-ventilation to improve indoorcomfort. Journal of Wind Engineering and Industrial Aerodynamics43749.ouli A, Renne D, Kazmerski LL. Technical and economic assessment of

taic-driven desalination systems. Renewable Energy 2011;35:3238.Song ZP, Wang RZ. A review for the applications of solar chimneys in. Renewable and Sustainable Energy Reviews 2011;15:375767.trand RK. Enhancement of natural ventilation in buildings using ahimney. Energy and Buildings 2009;41:61521.K, Mathur R, Bhandari MS. A study of solar chimney assisted windstem for natural ventilation in buildings. Building and Environment495500.aadatian O, Sulaiman MY, Sohif M, Kamaruzzaman S. Performancenduced natural ventilation tower in hot and humid climatic condi-

WSEAS international conference on environment, ecosystems andent (EED11). Montreux Switzerland: WSEAS, 31 December 2011; in

Review of windcatcher technologies1 Introduction2 Windcatcher attributes2.1 Vernacular windcatcher2.2 Modern windcatcher2.3 Super modern windcatcher2.4 Windcatcher with different opening2.5 Shape of windcatcher2.6 Windcatcher with damper and egg crate grille

3 Windcatcher technology3.1 Wind and buoyancy effects3.2 Heat source3.3 Use of evaporative cooling3.4 Hybrid commercial windcatcher system3.5 Windcatcher for outdoor3.6 Down draft windcatcher

4 Windcatcher configuration4.1 Inclination angle and meteorological parameters4.2 Louver configuration in commercial windcatcher4.3 Windows configuration4.4 Combination of windcatcher and solar chimney4.5 Combination of windcatcher and inverted airfoil

5 Summary6 Recommendation for further studiesReferences

Documents

Review of Windcatcher Technologies_Omidreza