Urban WINd Towers - Aditya Ambare Master Dissertation

Urban WIN d Towers Passive Cooling system in Urban Heat Islands

MAA 02 Thesis dissertation Author : Thesis Advisors :

Program :

Aditya Ambare Marco Cruz Kunaljit Chadha MAA 02 // 2019-21

Urban WINd Towers Passive Cooling system in Urban Heat Islands Student Thesis Advisors Program

Aditya Ambare Marco Cruz Kunaljit Chadha Masters in Advanced Architecture Barcelona, Institute for Advanced Architecture of Catalonia IAAC

Thesis presented to obtain the qualification of master degree from the Institute of Advanced Architecture of Catalonia

Abstract Majority of the future population is expected to be living in urban areas which makes high-density housing (existing and future) a critical building typology. These typologies are most difficult for future interventions and even demolition due to presence of multiple shareholders. Due to urban-heat-island-effect cooling loads within the urban buildings have been rising and reliance on H.V.A.C. systems have risen. Adapting existing and future buildings through incorporation of passive cooling systems can reduce the energy demand. Case-study of Residential apartment building in La Rambla, Barcelona was conducted to study how incorporating wind towers into shafts existing within these building typologies can improve wind circulation. CFD analysis was done using Simscale (browser-based CFD platform) to study air flow patterns of proposed interventions and modifications were analyzed to improve wind distribution, speed and reduce turbulence. Natural phenomena including stack effect and venturi effect were used to streamline the wind flow. Smoke simulations of Houdini software were used to design the elements of Wind catcher inlet to increase the catchment capacity.

Using the results a passive cooling system was proposed. Using this system, spatial distribution of buildings were analyzed and a proposal for redesign of apartments was suggested. Future studies are required to analyze how existing buildings typology can be retrofitted through studying their existing spatial distribution and shaft location to propose wind tower incorporation. Through Energy analysis and using Adaptive comfort calculators, parameters of passive cooling systems can be optimized to provide required air-circulation rates within modern urban buildings.

Keywords: Passive cooling systems, Computational Fluid Dynamics Analysis, Environmental and Regenerative Design, Urban Building typology, Sustainability

Preface Urban Wind towers is a research

present and future urban inhabitants,

investigation for sustainable passive cooling system for present and future

Through the development of this

urban buildings derived from traditional

research I got an opportunity to work

Bio-climatic processes. The project

and learn from many distinguished

results into development of building

individuals who spared their time to

typology based on organization

help me with my thesis. Exploration

of spaces with optimization of

into Thermal comfort simulation,

performance of the designed Wind

computation fluid analysis, 3d printing

Towers. It has been written to fulfill the

and computational exploration have

graduation requirements of MAA02

further stimulated my interest in

Program at the Institute for advanced

sustainable building design and it

architecture of Catalonia. I was

would not have been possible without

engaged in researching and writing this

support of my advisors and constant

dissetation from October 2020 to June

support provided from IAAC Team.

2021.

My friends and colleagues have helped The project was undertaken due to

me enormously in so many situations

curiosity towards form exploration for

and their generosity have contributed

thermal comfort and development

immensely in the development the this

of sustainable building typologies for

work

Acknowledgement First of all I would like to express my gratitude to my thesis advisors Marcos Cruz and Kunaljit Chadha, who have supported me throughout all the year and whose expertise has enriched my grasp on the topic of my studies and research. I sincerely thank them for all their patience and time dedicated during the development of the research.

I would also like to thank Angelos Chronis, whose guidance towards development of my computational and analysis work flow enriched my understanding of environmental analysis This work would not have reached this level without his insights.

Next, I would like to extend my gratitude to the experts from the Institute for Advanced Architecture of Catalonia who have shared their knowledge and support during the thesis development stage. I would especially like to thank Ashkan Foroughi Dehnavi for constant computational support and patience. Special thanks to Ricardo Mayor for his constant fabrication support and introduction to robotic fabrication. This experience enriched my knowledge immensely

I would also like to thank Mümün Kesar and Ardeshir Talaei for taking time for providing support for the development of my thesis.

I I would like to specially thank Cristian Rizzuti for his support, encouragement and generosity in sharing knowledge and taking time to help me with my explorations.

This research would be possible to maintain a steady pace throughout the year without the constant encouragement and faith of my academic coordinator, the only Nikol Kirova.

Last but not least, I would like to thank my family and friends for their support and encouragement through the time spent in Barcelona.

Table of Contents 01 Abstract 02 Preface 03 Acknowledgment 04

Table of Contents

05 Introduction

5.1 Context

5.2

Problem Statement

5.3

Framework

06

Scientific interest

6.1

Passive cooling techniques.

6.2

Case- Study – 31, La Rambla Del Caputxins, Barcelona, Spain

07

State of the Art

7.1

Masdar City Wind Tower –

7.2

Torrent Research Center, Ahmedabad –

08

Aim and Objectives

8.1

Analyzing Wind Towers

8.2

Designing Adaptive Wind Towers

8.3

Building Design Proposal for Optimizing the cooling system

09

Methodology

10

Experiments and Developments

10.1 Shaft design –

Case 1.

Existing shaft configured with a wind catcher inlet.

Case 2.

Shaft cross-section area increases with floor levels.

Case 3.

Shaft cross-section increases with levels and hot air exhaust.

Case 4.

Three-sided shaft with cross-section area increasing with

levels and hot air exhaust.

10.2 Wind tower inlet -

10.3 Spatial Distribution - Configurations

11

Proposed Re-Design

11.1 Spatial Organization

11.2 Wind Tower Positions

11.3 Hot-Air Exhaust Positions

11.4 Responsive Facade System

12

Results and Discussion -

13

References

5 Introduction 5.1 Context By 2050 the world’s population is expected to increase up to 9.7 billion people, 68% of which will be living in urban areas in comparison to 56% in 2020 (Urban population (% of total population) | Data, no date)⁠ (Figure 1). Projected influx of people due to projected urbanization needs to be accommodated within future housing projects in already densely-packed urban areas with urban density of 112 people per square km within European Union and 58 people per square km in all countries combined (Roser, 2013)⁠. Future construction has potential of increasing the global C02 emissions from construction industry to more than the current 40% contribution(‘The World’s Cities in 2018’, no date)⁠. Apart from the environmental impact from the projected developments during and before construction phrase, these future buildings along with existing building will also contribute to the rise in global energy demand in the households.

Carbon emissions have been increasing at an annual rate of 2% between 1971 and 2004. This is particularly significant in the developing countries. One reason is the increasing energy demand in buildings due to the continuous growth of urban population. However, one of the growing trends in architecture to reduce the negative impacts of building construction and cope with the increase demand for new buildings is the multi-story buildings, in which developers increase the envelop height to satisfy the need for dense developments. This type of building could create a built environment that would be considered as sustainable, green or ecological. Thus, the ecological design of multi-story buildings is crucial and much more effective in those aspects than a small green building (Vasilakopoulou, Kolokotsa and Santamouris, 2014)⁠.

Cooling in buildings accounts for 10% of energy consumption worldwide, a number which is subject to increase with rise in global warming. As of 2016, residential sectors across various countries have been more reliant on Air- conditioning in comparison to commercial buildings ( Table 1)(- International Energy Agency n.d.).

Table 1: Air-conditioning units and cooling capacity by country/region, 2016 Installed stock Million units

United States European

Union Japan Korea Mexico China India Indonesia

Brazil South Africa Middle East World

Annual sales

Gigawatt output capacity

Gigawatt output

Res

Com

Total

Res

Com

Total

Million units ToRes Com tal

241

132

374

2295

2430

4726

16

8

24

314

129

443

43 116 30 7 432 14

53 33 28 9 138 13

97 148 59 16 569 27

192 407 129 40 2092 77

654 352 220 65 807 72

847 759 348 105 2899 149

9 9 2 1 41 3

3 2 2 1 12 2

12 11 4 2 53 4

34 47 19 5 305 14

41 14 15 6 81 12

75 61 34 10 386 25

7 14

5 14

12 27

32 59

27 68

59 127

1 1

1 0.3

2 1

5 5

4 1.4

9 6

1

1

3

6

15

22

0.1

0.1

0.3

0.9

1.1

2.1

30 1093

18 529

47 1622

147 6181

153 5491

299 11673

4 94

2 40

6 135

29 848

16 359

45 1207

Figure No. 1: World population growth, 1700-2100

capacity

Res

Com

Total

5.2 Problem Statement Existing Urban housing typologies lacks

Thermal

the flexibility of design and structural

as

intervention once construction is done,

and physiologically to perform to its

which makes users constantly reliant

capacity comfortably. Factors including

on H.V.A.C. (Heating, Ventilation and Air

metabolic rate, clothing insulation, air

conditioning) systems. These residential

temperature, mean radiant temperature,

buildings are most difficult to renovate

air speed and relative humidity influences

or

multiple

the thermal comfort (Standard 55 –

makes

Thermal Environmental Conditions for

these constructions more inert to urban

Human Occupancy, no date). U.T.C.I. -

changes and a constant contributor to

Universal thermal comfort index which

Urban Heat Island Effect. Present and

is an equivalent temperature (°C), it is

Future occupants are mostly necessitated

a measure of the human physiological

to rely on active cooling system without

response to the thermal environment,

an option for opting for a passive, cost-

was used to do micro-climate analysis of

efficient and sustainable system because

La Rambla area by using U.T.C.I. calculator

of the building typologies. Apart from being

of Ladybug tools to understand the

a constant strain on the environment

increase of ambient temperature due

because of constant energy demand, it

to Heat Island Effect. Average dry bulb

is also a constant economic constraint

temperature for selected period being

on inhabitants. Economically weakened

approximately 25 °C (Figure 2)( Mostapha

sectors suffer considerably because they

Sadeghipour Roudsari 2020).

demolish

shareholders

because involved,

of which

occupy the most densely-packed, space deficient living spaces in urban residential sector. Urban Heat Island effect due to replacement of natural land cover with pavements, buildings and other surfaces which absorb and retain heat for longer duration have led to increased energy cost for air conditioning, heat related illness and higher mortality rates (US EPA, n.d.).

Comfort

comfortable

which

is

conditions

defined mentally

Figure No. 2:

Micro-Climate Analysis - La Rambla, Barcelona using UTCI Calculator of HoneyBee Tools

5.3 Framework International institutions including United Nations and European Union along with numerous country’s government have set out policies to target reduction in green house gas emissions and invest in renewable energy. European Climate Target Plan proposal sets a target of cutting greenhouse gas emissions by at least 55% by 2030.

Intended target being to set Europe on the responsible path to be climate neutral by 2050 (2030 Climate Target Plan | Climate Action, no date)⁠. Countries including India have devised Climate change policy with target of producing 175 Gigawatt of renewable energy by year 2030 (India’s Climate Change Policy: Towards a Better Future, no date)⁠. United Nations Environmental Program – Sustainable Buildings and Climate Initiative is a partnership between main public and private actors in building and construction sectors with purpose of promotion of universal adoption of resource and energy efficient practices in buildings (Sustainable Buildings and Climate Initiative (UNEP-SBCI) - ENERGIES 2050, no date)⁠. United Nations Sustainable Development Goals specifically 7. Affordable and Clean Energy, 9. Industry, Innovation and Infrastructure and 11. Sustainable cities and communities(Sustainable Buildings and Climate Initiative (UNEP-SBCI) - ENERGIES 2050, no date)⁠ also emphasizes the need to change and adapt the existing urban and architectural practices.

Buildings play an important role in the dynamics of the cities and majorly dictates the nature of the urban fiber. Advancement and enhancement of building design in existing and future developments have potential to reduce the impact of construction industry towards global warming. Reducing energy consumption in buildings through energy efficient processes can reduce the overall target demand of energy and reduce the strain on development of efficient renewable energy processes. This aspiration to make present and future buildings less reliant of energy intensive systems for thermal comfort drives the scientific interest of this work.

“

How incorporation of passive cooling systems in

building design of present and future urban housing projects drive the form development and performance of the living spaces to reduce the energy consumption for cooling purposes?

”

6

Scientific Interest

6.1 Passive cooling techniques Passive cooling systems have been part of

Middle East and China ((PDF) Towards

traditional architecture of ancient Egypt

Sustainable

and subsequently spread to the Middle

Parameters of Courtyard Design, no

East, to North India, to North Africa and to

date)⁠. Size, proportion and orientation

Southern Spain. Recently these traditions

of courtyards depend on the climate as

have been revived in works of Hasan

to allow the desired amount sunlight

Fathy and other architects (Ford and

to enter within the spaces to create

Ford, 2002). Techniques like Mashrabiya,

comfort condition. The latitude of the site

Yakhchal, Courtyard design, Malqaf and

determines size of the courtyard as site

Wind towers (Figure 3) have been used

situated closer to equator should have

for centuries for providing thermally

smaller width due to higher solar angle.

comfortable living spaces in hot and dry

Conversely the width should increase

climate through passive means.

for locations near the poles of earth

Historically these spaces have driven

to allow more daylight within the living

building design and orientation of spaces,

spaces. The courtyards are very effective

subsequently these characteristics have

solution in hot and arid climatic zones

became associated with the period and

to create comfort conditions. During the

architectural style of the place. These

day time, hot outside air become lighter

processes have been developed through

but the temperature inside the courtyard

iterations done over periods of centuries

remain less, so air become denser and

and have performed in energy efficient

cooler comparatively. The cooler air

way to provide thermally comfortable

flows through rooms through courtyard

living spaces for the inhabitants.

and warm air flows outside. During night

Courtyards has been a climate responsive

time, the outside air become cooler due

solution

over

to lower temperature and denser. As

and may act as an

the building is still warm so courtyard air

efficient solution for future buildings.

becomes lighter. The outside air flows

They are an effective solution in all

inside through rooms and get exhausted

types of climate especially hot arid and

from the courtyard, so due the significant

hot humid. The use of courtyard have

diurnal temperature in hot and arid zones,

became architectural identity in India,

movement of air creates comfortable

throughout

various topology

centuries

Future:

Typologies

and

living condition. In hot and humid climate,

on the top of the pads and collected at

this movement of air is very effective for

the bottom in a sump and re-circulated

human comfort conditions because it

through a pump. The towers are equipped

reduces moisture content of the air.

with evaporative cooling devices at the

The working principle of a Wind tower

top to provide cool air by gravity flow.

is that hot ambient air enters the tower

According

through the openings in the tower which

Fathy “The mashrabiya interstices both

gets cooled, and after becoming heavier

intercept the direct solar radiation and

and sinks down. The cool air movement is

soften the uncomfortable glare. Besides,

induced through inlet and outlet of rooms.

considering that the mashrabiya is made

As an inlet is provided to the rooms with

of out wood, it helps regulate the humidity

an outlet designed on the outer walls, a

inside the space. It is known that wood

draft of cool air is created. Because of

absorbs, retains and releases water.

the high diurnal variations in hot and dry

When air passes through the interstices

climates this system are efficient (Katiyar

of the porous wooden mashrabiya, it

and Agarwal, 2012)⁠.

vaporizes some of the moisture gathered

The working principle of Evaporative

in the wood and carries it towards the

cooling lies in the fact that the heat of air

interior” (Bagasi, Calautit and Karban,

is used to evaporate water, thus cooling

2021)⁠.

the air before entering spaces, which

The principle governing the function of

in turn cools the interior space in the

Yakhchal ( ice-houses ) is to capitalize

building. However it can also be indirect

the below-zero winter temperatures of

in case when the roof is cooled with a

deserts by constructing tall wall to cast

pond, wet pads or spray, and thus ceiling

shadow on ground and thus preparing

is transformed into a cooling element

freezing condition. During night time

that cools the space below by convection

especially when the sky is clear, the

and radiation without raising the indoor

ground temperature drops quickly due to

humidity. Passive downdraft evaporative

radiation and at points where the earth

cooling systems consists of a downdraft

is cooler, the temperature drops more

tower with wet cellulose pads at the top

quickly and reaches the zero degrees

of the tower. Water is then distributed

(Medi, no date)⁠.

to

the

architect

Hassan

Modern Urban Building forms are mostly designed from the stand point of space efficiency which have progressively over last few centuries faded out these passive cooling systems from the design. These systems are now considered as redundant spaces but they did serve one of the key functions of any shelter that being of providing thermally comfortable living spaces. Though this function is now being served through the incorporation of H.V.A.C. systems but they are very energy extensive and have negative environmental implications.

Figure No. 3:

Passive Cooling Systems Catalog

Courtyard

Yakhchal

Mashrabiya

Wind Tower

Malqaf

6

Scientific Interest

6.2 Case-Study - 31 La Rambla Del Caputxins, Barcelona, Spain This research is developed through conducting a case study of a residential apartment buildings located in Raval neighbourhold of Barcelona area precisely situated at 31, La Rambla del Caputxins. The building is located at La Rambla and is typical highly dense, row housing apartment building, which common in El Raval, Gotico as well as Born neighborhoods. The particular apartment building was selected because El Raval neighborhood has high number of residential apartments (Figure 4) as well as higher numbers of resident population in Barcelona (Figure 3) (“Addresses According to the Population Register” n.d.).

Figure No. 7:

La Rambla Area, Barcelona, Spain. Blue Areas show the shafts of the building in the area.

Figure No. 4

Population in different area

Figure No. 5

Occupancy per Apartment

Figure No. 6

No. of residential Apartments

Based on the existing building typology which is densely populated row housing with presence of shafts, out of the various passive cooling techniques, Wind Towers and Mashrabiya were selected to be most suitable for designing a possible intervention in existing buildings and being possible design driver for future urban buildings.

Figure No. 8: Computational Fluid Dynamics Analysis, La Rambla, Barcelona, Spain..

Figure No. 9: Computational Fluid Dynamics Analysis Frames La Rambla, Barcelona, Spain..

Incorporation of Wind Towers is a macro level intervention which performs by reenvisioning the form of the building. In contrary to whereas modern day mashrabiya like Cool Spot (Figure 12)(“Cold Spot: Evaporative Cooling through Ceramics - Climate CoLab” n.d.) and Cool brick Figure 11 (“Cool Brick | Emerging Objects” n.d.) are micro level intervention focused on Facade design.

Passive Cooling Systems Catalogue

Figure No. 10: Computational Fluid Dynamics Analysis, La Rambla, Barcelona, Spain..

MASHRABIYA

YAKHCHAL

Micro-level intervention

Urban Wind Towers // C Biom A // 20-21 // Aditya Ambare

COURTYARD

MALQAF

WIND TOWER Macro -level intervention

17

Figure No. 11:

Cool Brick - Evaporative cooling airflow diagram

Figure No. 12:

Cold Spot - Evaporative Cooling through ceramics

7

State of the Art

7.1 Inspiration This work explores the Macro level intervention of incorporation of wind towers within building design. For these typology wind towers were selected as a passive cooling systems which could facilitate passive cooling phenomenons use of energy dependent cooling systems can be reduced.

These interventions can be long

enduring phenomenons due to them being form driven and less cost-efficient in terms of maintenance.

Modern iterations of wind towers have been developed by exploring the shortcomings of the traditional form and giving the flexibility and form made possible due to advanced construction technology and research. Addition of responsive element including directional control and mechanical support along with integration of different phenomenons have given new class of wind towers.

Figure No. 13:

Wind Towers - Yazd, Iran

Figure No. 14:

Working Principle - Wind Tower

7

State of the Art

7.2 Masdar City Wind Tower The Masdar City Wind Tower, developed by Foster + Partners is a contemporary interpretation of the traditional Arabic wind tower (Figure 15). From the height of 45 meters, the tower captures cooler winds and directs them towards the public square at ground level. Sensors situated at the top of the steel structure detect the direction of prevailing winds and operate louvers to open in so as to divert wind down the tower (Sustainability - Sustainable Urban Development - Masdar City, no date). Also the tower is capable of evoking a convection current in opposite direction as hot air rises simply through passage through the cross-section (Masdar City’s Wind Tower: Literally Cool, no date).

Figure No. 15:

Masdar City Wind Tower

Figure No. 16

Working Principle - Masdar City Wind Tower

7

State of the Art

7.3 Torrent Research Center, Ahmedabad Built on the principle of Passive Downdraught Evaporative Cooling, this research center was designed by Abhikram Architects in 1998 (Figure 17). Measurements of air temperature and relative humidity in different parts of the building in April 1998 revealed that very significant cooling and high air change rates were achieved. Peak temperatures of 27°C in the ground floor laboratory, and 29°C at first floor, were achieved when the external maximum reached 38°C. Over the same period, air change rates of 9 per hour on the ground floor and 6 per hour at first floor were recorded.

The staff reported that during the summer (February – June) the laboratories are comfortable without fans and are not stuffy or smelly, as most chemistry labs are, even when air conditioned. During the monsoon (July – September), the evaporative cooling system is not operated, of course, so ceiling fans are used to enhance comfort for these two to three months. In the first year since its occupation, the Torrent Research Center was reported to have used approximately 64% less electrical energy than the equivalent conventionally air-conditioned building. Expenditure on M&E plant was reduced by 36%, which also provides further savings in maintenance costs (Ford and Ford, 2002).

Figure No. 17:

Torrent Research Center, Ahmedabad

Figure No. 18

Working Principle - Torrent Research Center, Ahmedabad

8

Aim and Objectives

The aim of the thesis was formulated to be achieved through completion of following objectives 1. Analyzing the wind towers 2. Designing adaptive wind towers 3. Building Design Proposal for Optimizing the cooling system

8.1 Analyzing Wind Towers Performing parameters of wind towers were analyzed to understand the relationship between the form of the elements and the performance of the wind tower. Following relations were analyzed.

1. Cross-section area relation with the wind speed at different levels and distribution patterns inside the shaft 2. Wind catcher inlet cross-section relation to the wind speed within the shaft 3. Different geometry forms of the shaft and wind catcher inlet with wind speed and distribution performance.

8.2 Designing Adaptive Wind Towers Spatial organization around the developed cooling system to be analyzed to provide feedback to designing an Adaptive wind tower system.

1. Spatial characteristics of spaces with excess to Wind towers.

2. Spatial characteristics of spaces designed for facilitating a streamline distribution.

3. Program Organization driven by the designed cooling system organized around designed wind tower and supporting spatial forms.

8.3 Building Design Proposal for Optimizing the cooling system Redesign of the selected building for case-study to compare the difference between existing building typology and typologies driven through the incorporation for the designed system.

1. Planning of the building with similar functionality and occupancy 2. Analyzing the performance of new design in terms of Day-lighting and Ventilation.

“ The aim of this thesis project is to develop a passive cooling system for high-density residential buildings in which could be retrofitted into existing buildings and also become a design driving force for future buildings. ”

9 Methodology

The shafts been identified as potential building elements which can be configured for passive cooling. An existing building located at 31, Rambla del Caputxins was selected and shaft sizes were taken to analyze the performance of the interventions (Figure 10). Blue colored zones are indicating the different sizes of shafts typically found in these typologies.

Figure No. 19

31, La Rambla Del Captuxins, Barcelona

1. Simulation of the case when Wind catcher inlet to be attached to the existing shaft to be analyzed through conducting Computation fluid dynamics analysis to determine the performance change in terms of wind speed and temperature at different floor levels.

2. Modifications to the shaft geometry to achieve desired parameters to establish favorable thermal-environmental-conditions-for-human-occupancy at every levels to analyzed and relation to be established between subsequent cases.

3. Wind tower inlet to be modified to improve the performance with respect the traditional forms using smoke simulations and C.F.D. simulations.

4. Adaptive features to be designed for strategic elements to modify according to changing environmental conditions. Subsequent analysis to be conducted to test the performance.

5. Iterating the spatial arrangement of passive cooling system to improve the day lighting performance of the spaces around the shafts and comparing it to the existing day lighting condition experienced at present.

6. Iterating the spatial arrangement of living spaces in the site of the case study to optimize the minimum account of design elements for similar occupancy and spatial requirements 7. Redesign the existing residential building with developed passive cooling system and spatial arrangement required for optimum performance.

10 Experiments and Developments The proposed passive cooling system consists of designing of three elements namely, Outside Air Inlet, Shaft and Inside Air Outlet. These elements were designed through conducting Computational Fluid Dynamics (C.F.D.) analysis on the form through Simscale – a browser based C.F.D. simulation platform (SimScale GmbH, Munich, 2021) .

10.1 Shaft Design Existing shaft of dimensions 3m by 7m was selected and following interventions to shaft cross-section areas were made. Introduction of additional shafts and removal of spaces from the configurations were analyzed to achieve at an optimized configurations.

Figure No. 8:

Performing Elements of Urban Wind Towers.

10.1 Shaft design Case 1

Shaft cross-section area increases with floor levels..

C.F.D. analysis was performed on two scenarios with a building model with wind catcher designed at the shaft opening (Figure 12).

1.A. Window sizes were kept the same on all floor levels.

1.B. Window sizes were decreasing with increasing floor levels.

Conclusion In the case 1.A wind distribution is more consistent in upper floors than lower floors.

In the case 1.B with larger window dimensions at lower levels and smaller window sizes at higher levels, better wind distribution was observed at lower levels. Due to smaller window cross-section at higher levels more volume of air were allowed to flow to lower levels increasing the ventilation rate in the spaces adjacent to the shaft.

Figure No. 8:

Case 1.A configuration

Figure No. 9:

Case 1.A

Computational Fluid Dynamics Analysis Frames

Figure No. 10:

Case 1.B

Computational Fluid Dynamics Analysis Frames

10.1 Shaft design Case 2

Shaft cross-section area increases with floor levels.

Cross sectional area of the shaft at floor levels was reconfigured to increase with height of the shaft to capitalize the Venturi effect (Reader-Harris 2015) to speed up the air velocity within the shaft as its directed downwards (Figure 10).

CFD analysis was done with a cross-sectional area of the wind tower configured in two scenarios. Case 2.A with the window sizes kept uniform throughout all the floors and Case 2.B with window sizes decreases with increase in floor level.

Figure No. 10:

Shaft cross-section modification incorporating venturi effect

Conclusion In the Case 2.A, in comparison to the previous Case 1.A where the shaft cross-sectional area was not altered, wind distribution was found to be more streamlined and less dead zones were observed.. In the Case 2.B, with window sizes decreasing as level is increasing, better wind distribution was observed for lower levels.

Figure No. 11:

Case 2.A configuration

Figure No. 12:

Case 2.A

Computational Fluid Dynamics Analysis Frames

Figure No. 12:

Case 2.B

Computational Fluid Dynamics Analysis Frames

10.1 Shaft design Case 3

Shaft cross-section increases with levels and hot air

Case 2.A and Case 2.B was modified with the addition of a hot air exhaust shaft with an opening designed on the wall opposite to the wind tower shaft wall. Stack effect in the living spaces lead the hot air generated within the space to escape to the hot air shaft (Figure 13). The system created an improved streamline distribution and reduced the mixing of hot air within the living spaces with the air from the wind tower shaft. It also reduced the turbulence within the space, created a cross-ventilation system which led to improved wind speeds and steady flow.

CFD analysis was done in two scenarios with this system. Case 3.A with window sizes kept same through all floor levels. Case 3.B with window sizes decreasing with increasing floor levels.

Figure No. 13:

Shaft cross-section modification incorporating venturi effect

Conclusion In Case 3.A wind flow was found to be more streamlined and consistent with less turbulence than the previous system without the hot air exhaust shaft. Wind flow was observed to pass through habitable elevations within the living spaces due the presence of the exhaust at a high level of the wall of hot- air shaft.

In Case 3.B, as in previous cases, wind flow in the lower levels was observed to improve than the Case 2.A and Case 2.B. Wind speed through the spaces was also observed to be increased.

Figure No. 14:

Case 3.A configuration

Figure No. 15:

Case 3.A

Computational Fluid Dynamics Analysis Frames

Figure No. 16:

Case 3.B

Computational Fluid Dynamics Analysis Frames

10.1 Shaft design Case 4

Three-sided shaft with cross-section area increasing

with levels and hot air exhaust.

In this system living spaces were removed from one side of the shaft in case to allow sunlight enter these shafts using a transparent material to allow the daylight into the shaft cross-section. The system was analyzed in two scenarios. The Case 4.A with window sizes remaining the same through all floor levels and Case 4.B with window sizes decreasing with increasing floor levels (Figure 18).

In comparison of Case 4.A and Case 4.B, in the Case 4.B wind distribution in lower levels was observed to greatly improve in comparison with the Case 4.A. Less dead zones were also observed in the case 4.B in comparison with the Case 4.A.

Figure No. 17:

Distribution according to Continuity equation

Conclusion The system when optimized with window sizes in relation to cross-sectional area, allows for better air distribution for spaces located at lower levels (Figure 19). Thus increasing the wind velocity through venturi effect towards the lower level with reduced window cross-section at higher levels allows more air volume to flow towards the lower levels (Continuity Equation, no date).

Figure No. 18:

Case 4.A configuration

Figure No. 19:

Case 4.A

Computational Fluid Dynamics Analysis Frames

Figure No. 20:

Case 4.B

Computational Fluid Dynamics Analysis Frames

10.2 Wind tower inlet Case 1

Shaft cross-section area increases with floor levels..

Design of the Wind catcher Inlet was designed to be hexagonal which improves the air catching capacity of the system in comparison to a rectangular shape one.

Hexagonal form allowed the wind catcher to direct wind towards the shaft from multiple directions irrespective of the prevailing wind direction which was a drawback in the traditional wind catcher- their inability of regulating orientation according to prevailing winds (Figure 21).

As observed in the traditional wind tower design the connection between the wind catcher inlet and shaft was streamlined using a quarter sphere cross-section from all the inlet directions. Horizontal Louvers were designed at the inlet so to control the wind velocity (Figure 22). Larger cross-section can be used during days with lower wind speed and more humid days and smaller cross-section can be used during windy days (Figure 24).

Figure No. 21

Wind Tower Inlet- Elements

Vertical Blades : to divert air coming at an angle towards the openings

Skin : To Divert the incident wind towards the inlet crosssection

Horizontal Louvers : To control the inlet cross-section

Vertical Fins : to facilitate wind intake from prominent direction

Figure No. 22

Wind Tower Plan

Vertical Blades : to divert air coming at an angle towards the openings

Skin : To Divert the incident wind towards the inlet cross-section

Horizontal Louvers : To control the inlet cross-section

Vertical Fins : to facilitate wind intake from prominent direction

Towards the Shaft : to streamline the flow of wind

51

Figure No. 23

Wind Tower Inlet- Elevation

Vertical Blades : to divert air coming at an angle towards the openings

Skin : To Divert the incident wind towards the inlet cross-section

Horizontal Louvers : To control the inlet crosssection

Vertical Fins : to facilitate wind intake from prominent direction

Towards the Shaft : to streamline the flow of wind

Figure No. 24

Wind Tower Perspective

10.2 Wind tower inlet Vertical Louvers were designed in front of the horizontal louvers to adjust accordingly to the prevailing wind direction. Angled skin detail was added to direct the wind towards the inlet cross-section through the louvers. Vertical Blades which are radially protruding outside which directs the wind towards the angled skin detail when the wind direction is not perpendicular to the inlet. This increased the wind catching ability of the system.

The proposed design increases the wind catching ability of the wind towers in comparison to its traditional counterparts. Hexagonal shape provided multi-directional catchment surfaces along with enough vertical surface from all directions (Figure 25).

Directional details like vertical blades, vertical louvers and angled skin detail increases the performance of the system and the quarter sphere section of the inlet provides a streamlined wind flow towards the shaft (Figure 24). The 3d modeling was done in Rhinoceros and Grasshopper software and Smoke simulations were performed using Houdini software.

Figure No. 25

Inlet Cross-section important to control the velocity of the air

Streamlined Geometry to direct the wind towards the shaft

Towards the Shaft

Wind Tower Design - Cross-section

Figure No. 26:

Wind Tower Inlet Computational Fluid Dynamics Analysis

Figure No. 27:

Wind Tower Perspective Smoke Analysis

Figure No. 28:

Wind Tower Section

Smoke Analysis

10.3 Spatial Distribution - Configurations Configuration of proposed system with

the sides of the wind tower increased

wind towers and exhaust shafts designed

the number of spaces which could be

around the living spaces was analyzed to

cooled down by the system. It also gives

propose a spatial distribution of functions.

the possibility to remove living spaces

Three distributions were analyzed in

from one direction and use transparent

highly dense row housing typology with

material to allow sunlight to enter the

lack of facades with access to fresh air.

shaft areas. Though this configuration increased the number of spaces which

SD1 was designed for a scenario with

could be cooled passively and by giving

rectangular shafts with narrow front and

the flexibility of space design by moving

back facades. Multiple wind towers were

away from rigid rectangular spaces to

proposed within the space and living

distorted spaces also made possible but

spaces were designed around the wind

due to radial distribution of the spaces

tower shaft. Due the rectangular shape of

hot air exhausts cannot be utilized for

the shaft, number of living spaces around

more than three spaces in most cases.

the tower was found to be a limiting

The number of hot air exhausts to be

factor. The living spaces were designed to

provided was found to be excessive in

be rectangular as the prevalent observed

this case.

spaces within residential apartments.

This was also found to be a limiting factor

In the SD3 a hybrid of the SD1 and SD2

because of the lack of flexibility within

was designed. Spaces were designed

spaces. Hot air exhausts were designed

organically

across the living spaces. Due to the

towers and exhaust shafts. Flexible spatial

rectangular configuration of spaces hot-

forms of living spaces were iterated so as

air exhaust could not be connected to

to increase the number of connections

more than three spaces connected to

between spaces and towers with keeping

wind towers which made them space

the no. of wind towers and no. of hot air

deficient features

exhausts to minimum.

SD2 was designed with a multiple- sided

In conclusion the SD3 with its flexible

wind tower and radial distribution of the

spatial forms and multi-sided wind towers

spaces around the tower. Increasing

reduced the number of both towers and

around

multi-sided

wind

exhaust shafts while maximizing the number of the living spaces which could be cooled (Figure 26). Flexible space configurations like in SD3 can be modified depending upon the site limitations. The form of the building can be driven by optimizing the functionality of the system.

Figure No. 29:

Spatial Distribution - SD1 , SD2 and SD3

11 Proposed Re-Design Using the SD3 configuration, the future

south side were designed accordingly to

designs of the residential apartments

sun path and massing was developed

were explored. The form driven by the

by carving out spaces to allow sunlight

passive cooling systems can have a long

into the wind towers. Spaces were not

lasting benefits because of the passivity if

designed on the south side of the wind

the design. The building could reduce the

tower to allow penetration of the sunlight

dependence on the power grid to certain

into the shaft and thereby into living areas

degree and effect when multiplied with

adjacent to the tower. This arrangement

number of buildings can have significant

of improves not only the ventilation rate

benefits at large and make progress

within the spaces but also provides better

towards achieving sustainability targets.

day lighting conditions in comparison

In

to the spaces with access to shafts in

the

proposed

redesign

of

the

residential building at chosen site of the case- study, the Urban Wind Tower

existing building.

system was employed and possible

11.2 Wind Tower Positions

spatial distributions were analyzed.

The positions of wind towers were strategically iterated to allow maximum

11.1 Spatial Organization

penetration of sunlight into the shafts

Proximity analysis of living spaces with

and number of spaces to be designed

respect to wind tower initiated the

to allow access to the towers. The final

earlier iterations. Space requirements of

configuration of the towers was designed

living areas and other functional zones

diagonally to the site with facade of the

were taken with considerations to the

towers parallel to the east-west axis.

dimensions of similar areas in existing

The buildings can be understood through

apartments. The spaces recognized to

breaking the spaces into three parts.

be given preference to be designed in

Firstly, spaces located on the west side and

close proximity to the wind towers were

access to the west wind tower. Secondly,

primarily decided on the basis of degree

spaces located centrally and with the

of access to daylight and fresh air. The

access to the central wind tower. Lastly,

number of wind towers to be designed

spaces located on the east side with the

was decided to be 3 after the development

access to east wind tower. The spaces

of proximity chart. The spaces facing the

designed around the west wind tower

were designed to consist of lower number

with rising floor levels which give rise

of floors in comparison to the central part

to possible flexible spaces. The cross-

of the building. The intention was to allow

section area of hot-air exhaust follow the

more sunlight into the central wind tower

reserve pattern as they reduce in cross-

and reduce masses which would block

section area with increasing level. This

it. Thus the location of the central wind

relation between cross-section areas of

tower is more southwards than the west

wind towers and hot-air shafts to some

wind tower to avoid hindrance to the

degree compensates the area lost due to

sunlight from west tower. Subsequently,

increasing cross-sectional area of wind

similar interpretation of spatial logic was

tower.

extended to the relation of the location of east wind tower and spaces around

11.4 Responsive Facade System

it, with proximity relation to the central

The southern sides of wind towers were

wind tower. Massing on the eastern side

made of glass panels with responsive

is also more dense and with more levels

facade systems to allow the access of

in comparison to the central spaces and

sunlight into the shafts and reduce the

western spaces.

radiation levels respectively (Figure 28).

With the proposed responsive systems

11.3 Hot-Air Exhaust Positions

the spatial quality also improved in

Service

comparison

spaces

including

staircases,

to

the

existing

rooms

elevator shafts and lobbies which are used

adjacent to the shafts. Day lighting

for vertical connectivity are used as hot-

analysis was conducted on floor plates of

air exhaust shafts. The air draft is created

existing buildings and compared to the

due through convention phenomenon

results of the analysis done the proposed

like stack effect, which improves space

building design. Substantial improvement

quality these spaces which are usually

in day lighting level of all spaces also

lacking proper ventilation, have bad odor

with responsive system it is possible to

and are poorly lit.

control the radiation gain. Overall system

As the cross-section area of the wind

can also be converted to a greenhouse

towers increases with levels so the

system to provide passive heating during

spatial arrangement of rooms change

winter months if necessary.

Figure No. 30:

Re-Design Plan Development

Figure No. 31:

Daylighting Comparisons between existing and proposed Design at 3rd Floor Level

12 Results and Discussion Incorporation

of

passive

cooling

reduce dead zones within the shaft area.

techniques like wind towers into design

Different degrees of intervention are

of future urban buildings as well as

possible to be made into an existing

retrofitting them into existing buildings

building depending upon their typology.

can contribute to reduction of the cooling

Addition of the wind catcher improved

loads of the spaces which in turn can

the wind speed within the shaft in Case

contribute in reducing overall energy

1.A and 1.B and subsequently modifying

consumption of building. The built-form

the shaft sizes improved with the air

of the proposed Urban Wind Towers

distribution rates within all floor levels.

with its responsive features can provide

Incorporation of Hot- Air exhaust reduced

a passive alternative to active energy

the merging of cool incoming air and hot

extensive means.

inside air through stack effect. In case

Through use of Computational Fluid

4.A and 4.B it was found that one side

Dynamics simulations it was found that

of the shaft can be used for day-lighting

the cross-sectional profile of the shaft

purposes by removing living spaces from

influences the air distribution rates within

the subsequent side.

the adjacent living spaces. Modifying the

Multi-sided wind tower and proposed

cross-sectional area at different levels can

design of the wind catcher with elements

improve the air flow rate within the lower

including fins, skin and vertical blades

floors spaces which usually experience

improved the wind catching efficiency

lack of air ventilation leading to thermally

in

uncomfortable

counterparts.

conditions.

Also

by

comparison

to

its

Responsive

traditional elements

modifying the surface area of window at

including the directional control in the

different levels, air distribution rate can

vertical fins helps to orient the system

be modified to provide better ventilation

towards the prevailing wind direction

rate in lower floors.

making the system adaptive to changing

Urban Wind Tower system by capitalizing

environmental conditions and changing

natural

phenomenons

urban design elements. Modifications

including Stack effect and Venturi effect

to the vertical and horizontal fins can

was found through Computational Fluid

also modify the cross-sectional area of

Dynamics analysis to result in improved

the inlet which can increase and reduce

air flow rate within living spaces and

the wind speeds making the system

convection

adaptive. Immovable elements including vertical blades and skin assist in better air catchment performance. Using Smoke simulation of Houdini Software, wind tower inlet elements were designed to improve the wind catching capacity.

Flexible Spatial organization allows for maximizing the number of spaces which can be designed with an access to the wind tower. Modification to the orientation of the spaces, addition and subtraction of them can improve the day lighting levels within the previous sunlight – deficient areas. It reduces the energy consumption for day lighting purposes especially the consumption which is because of poorly lit spaces around shafts which need more hours of electricity than spaces which have access to natural daylight.

Traditional passive cooling systems have defined the building design for centuries and their incorporation into modern building can also lead to new building forms which can assist in reducing the energy demand of urban areas.

13 Conclusion High-density urban housing is one the

calculator. Such research can provide

major contributors to Urban Heat Island

optimum dimensions for shaft cross-

Effect and lack of flexibility in future

section area as well as Window sizing.

intervention due to presence of multiple

Further radiation analysis in conjecture

shareholders

existing

with C.F.D. analysis can help resolve day

reliance on Heating, Ventilation and Air

lighting issues within these shafts through

Conditioning systems for cooling the

use of transparent facades on one or

living spaces. Though the urban typology

more sides. Future spatial arrangement

differs in different cities around the world,

patterns could be defined around passive

incorporation of passive cooling systems

cooling systems. Existing building with

through building design can help reduce

shafts could be analyzed for optimum

energy

growing

retrofitting proposal and change in

urbanization

energy consumption could be compared.

these typologies are subjected to rise in

Future buildings can be designed through

numbers and their building design and

optimizing the parameters of the passive

form will have irreparable impact on the

cooling system – Urban Wind Towers like

future energy demand and quality of

window cross-section area or Wind tower

living spaces.

Inlet cross-section to optimize the wind

Building design centered around passive

speed necessary for achieving thermal-

cooling system and form developed for

environmental-conditions-for-human-

its performance can have lasting impact

occupancy.

creates

dependencies.

population

and

rapid

ever

With

on the economic and energy strain on the present and future inhabitants.

With design of responsive elements the building can be flexible and sustainable in the awake of climate change in a more green way.

Future application of this research involves conducting energy simulation of the building design using Energy Plus through Honeybee, to find necessary wind speed at different levels using Adaptive- comfort

14 References (PDF) Towards Sustainable Future: Typologies and Parameters of Courtyard Design (no date). Available at: https://www.researchgate.net/publication/304579145_Towards_ Sustainable_Future_Typologies_and_Parameters_of_Courtyard_Design (Accessed: 16 September 2021).

2030 Climate Target Plan | Climate Action (no date). Available at: https://ec.europa. eu/clima/policies/eu-climate-action/2030_ctp_en (Accessed: 15 September 2021).

Bagasi, A. A., Calautit, J. K. and Karban, A. S. (2021) ‘Evaluation of the Integration of the Traditional Architectural Element Mashrabiya into the Ventilation Strategy for Buildings in Hot Climates’, Energies 2021, Vol. 14, Page 530, 14(3), p. 530. doi: 10.3390/ EN14030530.

Continuity Equation (no date). Available at: https://www.princeton.edu/~asmits/ Bicycle_web/continuity.html (Accessed: 16 July 2021).

Ford, B. and Ford, B. (2002) ‘Passive downdraught evaporative cooling : principles and practice environmental design Passive downdraught evaporative cooling : principles and practice’, 5(January 2002), pp. 271–280.

India’s Climate Change Policy: Towards a Better Future (no date). Available at: https:// www.mea.gov.in/articles-in-indian-media.htm?dtl/32018/Indias_Climate_Change_ Policy_Towards_a_Better_Future (Accessed: 15 September 2021).

Katiyar, M. and Agarwal, S. (2012) ‘An Overview of Passive Cooling Techniques in Buildings: Design Concepts and Architectural Interventions’, Civil Engineering & Architecture, 55(1), pp. 84–97.

Masdar City’s Wind Tower: Literally Cool (no date). Available at: https://www. triplepundit.com/story/2011/masdar-citys-wind-tower-literally-cool/81091 (Accessed: 16 July 2021).

Medi, H. (no date) ‘Yakhchal- cooling deep domed construction’. Available at:

https://www.academia.edu/19829044/Yakhchal_cooling_deep_domed_construction (Accessed: 17 September 2021).

Roser, M. (2013) Future Population Growth, Our World in Data. Available at: https:// ourworldindata.org/future-population-growth (Accessed: 14 September 2021).

SimScale GmbH, Munich, G. (2021) ‘Simscale’. Munich, Germany.: SimScale GmbH. Available at: https://www.simscale.com/.

Standard 55 – Thermal Environmental Conditions for Human Occupancy (no date).

Available

at:

https://www.ashrae.org/technical-resources/bookstore/standard-55-

thermal-environmental-conditions-for-human-occupancy (Accessed: 15 July 2021).

Sustainability - Sustainable Urban Development - Masdar City (no date). Available at: https://masdar.ae/en/masdar-city/the-city/sustainability (Accessed: 16 July 2021).

Sustainable Buildings and Climate Initiative (UNEP-SBCI) - ENERGIES 2050 (no date).

Available at: https://energies2050.org/sustainable-buildings-and-climate-initiativeunep-sbci/?lang=en (Accessed: 15 September 2021).

‘The World’s Cities in 2018’ (no date). Available at: https://www.flickr.com/photos/ thisisin (Accessed: 17 July 2021).

Urban population (% of total population) | Data (no date). Available at: https://data. worldbank.org/indicator/SP.URB.TOTL.IN.ZS (Accessed: 14 September 2021).

Vasilakopoulou, K., Kolokotsa, D. and Santamouris, M. (2014) ‘Cities for Smart Environmental and Energy Futures: Urban Heat Island Mitigation Techniques for Sustainable Cities’, pp. 215–233. doi: 10.1007/978-3-642-37661-0_12.