Clean Air through Evaporation in Athens Greece by msc.exhibition2019

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

THESIS

PROJECT

University of Westminster Faculty of Architecture and Environmental Design Department of Architecture Course: MSc Architecture and Environmental Design 2018-2019 Module: THESIS PROJECT, Semester 2&3 Module code: 7AEVD005W Student: Alexandra Vlazaki Student number: w1710712 Date: 02 Sep 2019 Thesis title: Clean air through evaporation in Athens, Greece Location: Athens, Greece Word count: 17,194

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Acknowledgments

Phan for introducing me to new concepts which allowed me to explore more areas in terms of passive design. Special thanks, also to Jon Goodbun for offering this thesis topic and for the documents and information he provided to me. Finally, I would like to thank Mehrdad Borna for his advices and suggestions for this specific thesis topic.

I am grateful and I would like to especially thank Juan Vallejo for his guiding for this research project. Knowing and working under his guidance has been the most enriching experience of my life. His patience, constructive criticism has provided a strong and very organized base for this study. I am deeply obliged for Rosa Schiano

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Table of Contents 1. 7

Abstract

2. Literature review

-2.A General Information -2.B Air pollution in Athens -2.C Climate Analysis of Athens -2.D Evaporating Cooling

8 8 12 14

3. Research Questions and Methodology

-3.1 Scope -3.2 Methodology -3.2.1 Literature review -3.2.2 Fieldwork -3.2.3 Phase I: Finalizing the shape, height, and dimensions of the tower device -3.2.4 Phase II: Performance of air distribution -3.2.5 Phase III: Operative hours of the tower device -3.2.6 Phase IV: Performance of the tower device on the selected areas -3.2.7 Phase V: Performance of more than one tower devices -3.3 Research questions -3.4 Hypothesis -3.4 Outcomes

4. Fieldwork

15 15 15 15 16 16 16 16 16 16 17 17

-4.1 Context -4.2 Fieldwork on a sunny day -4.3 Fieldwork on a cloudy, windy day

19 20 21

5. Case study project

-5.1 Introduction -5.2 Phase I: Finalize the shape, height and dimensions of the tower device -5.3 Phase II: Performance of air distribution -5.3 Phase III: Operative hours of the tower device -5.3 Phase IV: Performance of the tower on the selected areas -5.3 Phase V: Performance of more than one tower devices

24 26 33 44 53 60

6. Conclusion

7. References

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Table of Figures Figure 1: World map of Köppen, http://hanschen.org/koppen/ 12 Figure 2: Climate of Athens, data obtained from meteonorm 13 Figure 3: Wind rose and Total radiation data obtained from ladybug plug-in and meteonorm 14 Figure 4: Two selected areas in Athens 20 Figure 5: First selected area: Syntagma square 20 Figure 6: Second selected area: Ampelokipoi roundabout 20 Figure 7: Spot measurements of sunny day 21 Figure 8: Problems and limits of Syntagma square 22 Figure 9: Spot measurements of cloudy, windy day 23 Figure 10: Chosen project 25 Figure 11: First idea of the project 25 Figure 12: Procedure of evaporative cooling and tasks 26 Figure 13: First scenario: Ain=30.20m2, Aout=100.00m2, H=10m 27 Figure 14: Second scenario: Ain=30.20m2, Aout=100.00m2, H=25m 28 Figure 15: Third scenario: Ain= Aout =30.20m2, H=10m 29 Figure 16: Forth scenario: Ain= Aout =30.20m2, H=25m 30 Figure 17: Fifth scenario: Ain=30.20 m2, Aout =100.00m2, H=10m 31 Figure 18: Sixth scenario: Ain=30.20 m2, Aout =100.00m2, H=25m 32 Figure 19: First hypothesis: air velocity 1m/s 34 Figure 20: Air movement 35 Figure 21: Second hypothesis: air velocity 1.5m/s 35 Figure 22: Air movement 36 Figure 23: Third hypothesis: air velocity 2m/s 37 Figure 24: Air movement 37 Figure 25: Forth hypothesis: air velocity 2.5m/s 38 Figure 26: Air movement 38 Figure 27: Fifth hypothesis: air velocity 3m/s 39 Figure 28: Air movement 40 Figure 29: Sixth hypothesis: air velocity 3.5m/s 40 Figure 30: Air movement 41 Figure 31: Sixth hypothesis: air velocity 4m/s 42 Figure 32: Air movement 42 Figure 33: Seventh hypothesis: air velocity 4.5m/s 43 Figure 34: Air movement 44 Figure 35: Conclusions of Phase II 44 Figure 36: Final part of equations 45 Figure 37: Annual results of operative hours for the whole year 46 Figure 38: Annual results of ΔΤ for the whole year (1st graph) and for the operative hours (2nd graph) 47 Figure 39: Annual results of Relative Humidity for the whole year (1st graph) and for the operative hours (2nd graph) 48 Figure 40: Annual results of Relative Humidity for the whole year (1st graph), annual results of 5

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Precipitation (2nd graph) and annual results of Cloud Cover Fraction (3rd graph) 49 Figure 41: Climate analysis, cumulative rainfall 50 Figure 42: Annual results of fresh air that the tower can produce during the whole year 50 Figure 43: Annual results of persons that the tower device can cover with fresh air during the whole year 51 Figure 44: Annual results of Water consumption for the operative hours 51 Figure 45: Annual results of ΔΤ for the operative hours 51 Figure 46: Water consumption of each month for the operative hours 52 Figure 47: Annual results of the air velocity on the outlet area of the tower device 53 Figure 48: Statistics of the most frequent air velocity 54 Figure 49: Syntagma square 54 Figure 50: Separated parts of CFD simulation 55 Figure 51: Sections of the first selected area 56 Figure 52: Optimization of air distribution in Syntagma square 1m from the ground level 56 Figure 53: Optimization of air distribution in Syntagma square 10m from the ground level 57 Figure 54: Roundabout in Ampelokipoys, comparing to the whole capital 58 Figure 55: Optimization of air distribution in roundabout in Ampelokipoys 1m from the ground level 59 Figure 56: Updated selected area in Syntagma square 61 Figure 57: Optimization of air distribution in Syntagma square 1m from the ground level 62 Figure 58: Optimization of air distribution in Syntagma square 10m from the ground level 62 Figure 59: Updated selected area in Syntagma square 63 Figure 60: Optimization of air distribution in roundabout in Ampelokipoys 1m from the ground level 64 Figure 61: Optimization of air distribution in both selected areas with four activated towers devices 65

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

1. Abstract

The thesis aims to study the impact on improving the air quality and microclimate in Athens, by providing fresh air from the sky (above the urban canopy layer) to the ground level, by inducing a natural downdraught air movement through evaporation. At the same time, it can offer to users the possibility of lower temperature especially at summer, while providing a cooler air temperature at the same period. This collaborative topic lies in the need of Greece to solve pollution and overheating issues. Based on that, this project study a structure that goes up to 25m and it’s able to deliver fresh air. In the collaboration with Jon, his team in Athens and the University of Westminster, the thesis would like to focus research and develop this subject from many aspects. Such as the aspect of evaporating cooling strategy how it works, the effectiveness that this device can provide, the aspect of dimensions and the height of the structure, etc.

The conducted analytic work allowed the estimation of the amount of fresh air provided by a tower, its area of influence and water consumption on an hourly basis by Psychrometrics. According to all these, it was found that a tower with aperture areas of 100m2 at the top and 30.20m2 at the bottom can provide in average 36 litres of fresh air per hour over 4,212 hours of operation per year. It is important to mention that the area of influence was found to be 800m, thus 3 towers could cover an area of 6,031.860km2 of the city of Athens. This project can improve the well-being and the health of Greek people who suffers from diseases because of the pollution. The thesis proved that there is an environmental way to solve this problem with less effort, less money and most important, less consequences for the environment.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Air pollution is the appearance of pollutants in the atmosphere, that is, of any kind of substance, noise or radiation in quantity, concentration or duration such as to cause adverse effects on human health, living organisms and ecosystems. "Pollutant" means any substance that is directly or indirectly fed by humans to ambient air and may have harmful effects on human health and / or the environment as a whole, according to European Union.

2. Literature review 2. A General Information Greece, or Hellas as it is known historically, is located at 39oN 22oE, in Southern and Southeast Europe, with approximately 11 million people. The nation capital city of Greece is Athens and the second largest city, is named Thessaloniki. Greece is a country situated at the crossroads of Europe, Asia, and Africa. Located on the southern tip of the Balkan Peninsula, it has the same land borders with Albania to the northwest, Fyrom and Bulgaria to the north, and Turkey to the northeast. It is surrounded by the Aegean Sea lies to the east of the mainland, the Ionian Sea to the west, the Cretan Sea and the Mediterranean Sea to the south.

Athens is facing extremely high and dangerous air pollution levels. According to figures from the three year European programme Aphekom, Athens is the third worst affected city by air pollution for atmospheric impacts of atmospheric pollutants, in a total of 25 European cities. Prior to the analytical research for the causes and consequences of air pollution, it is essential to focus on knowing some generic information. Ambient air pollution in urban and industrial areas in Greece was and remains a serious environmental problem which was caused by the rapid urbanization of cities, the anarchic housing development without basic infrastructures, the huge emissions of the industries and the increases of cars and motorbikes in urban regions. But, by saying that air pollution causes serious problem to Greek people, what exactly does it mean? Which are the emissions of all these actions that cause the problem and what issue each of these gases boost every time to increase the air pollution level?

Greece and especially Athens, was the centre of civilisation and not only. Athens is the birthplace of democracy, Western philosophy, Western literature, historiography, political science, major scientific and mathematical principles, Western drama and notably the Olympic Games. But unfortunately the things didn’t work on the same way the next centuries. The results are disastrous for the humans. Many factors have led to these results like political, social, economic etc factors. Nowadays, Greece and especially Athens is suffering from some of the most serious issues in the world. For instance, Greece is experiencing financial crisis, the youth unemployment is extremely high. It is really difficult for someone to be financial independent if he hasn’t followed the some carrier as his parents. This is the main reason for the migration of the majority of young people to another country for a better life.

Emission sources of air pollutants can be separated into two categories, the anthropogenic sources and the natural sources. The anthropogenic sources are mainly associated with the combustion of various types of fuel. These sources include power generation, industry, building heating, wheeled vehicles, and the movement of ships and planes. The natural sources are mainly

2. B Air pollution in Athens

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

emissions of dust from wind erosion and the dust which is transferred from Africa to Greece, emissions of particulate matter and gases from forest fires, which have increased in Greece over the past 10 years by 80%. Greece possesses the 10% of all fires among all the countries of Europe.

concentrations in urban centers are in the order of 100 μg / m3, with limit values of 350 μg / m3 (average hourly value not exceeding 24 hours in one calendar year) and 125 μg / m3 (mean daily which should not exceed more than three times in a calendar year). Impacts: Sulfuric aerosols are considered to be harmful to human health. Inhalation of sulfated aerosols exacerbates the symptoms and consequences in connection with those we would have had from inhalation e.g. inorganic sulfate-free powder. Sulfur aerosols in the atmosphere reduce visibility because their magnitude is comparable to the visible light wavelengths. Also, sulfur dioxide proves devastating to many plant organisms. The main characteristic of dissolving sulfur dioxide in water droplets in the atmosphere and its oxidation is the formation of sulfuric acid, which is a strong acid. This acidity production is the main cause of acid rain formation. The Parthenon, one of man's most ancient and wonderful works, suffered dramatic damage from it.

European Union, US and also other countries have take the following strategies against pollutants: i) standard sampling methods and their concentration have been developed and applied by specialized machinery, both at source and air emissions points,, ii) emission limits have been established and applied by sources and limits in ambient air iii) national networks are operating, especially in large urban centres. Τhe most common pollutants are: i) the sulfur dioxide (SO2), ii) the nitrogen dioxide (NO2) and also nitrogen monoxide (NO), iii) the carbon monoxide (CO), iv) the lead (Pd), v) the benzene, vi) the trioxide (O3), vii) Volatile Organic Compounds (VOC), viii) the particulate matters (PM2.5 and PM10). But the real question is how do these emissions release in the air and which are the consequences of each emission on the environment and on the human health.

Nitrogen dioxide NO2 and nitrogen monoxide NO Sources: Nitrogen oxides found in traces in ambient air are seven: NO, NO2, NO3, N2 O, N2 O3, N2 O4 and N2 O5. Oxides of greatest interest in atmospheric pollution, and in particular the creation of photochemical cloud, are the nitrogen monoxide (NO) and the nitrogen dioxide (NO2). The main source of nitrogen oxides in the atmosphere is the combustion of fossil fuels. Average annual concentrations of nitrogen oxides in urban areas range from 20-90 μg / m3. The limit values are 200 μg / m3 (average hourly not to be exceeded more than 18 times per calendar year) and an average of 40 μg / m3 per calendar year. Nitrogen oxides are also responsible for high levels of ozone (O3).

Sulfur dioxide SO2 Sources: A colorless and water-soluble gas is emitted into the atmosphere due to the combustion of sulfur-containing fossil fuels. These emissions are due to combustion which becomes industrial units. A very small proportion of sulfur dioxide emissions are due to the different vehicles. The largest proportion is emitted by electricity generating units, with significant percentages being emitted by the distilleries and the cement industry. Average annual 9

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Impacts: Nitrogen monoxide, although it can bind to hemoglobin in the blood because it is found in the atmosphere at much lower concentrations than carbon monoxide, does not cause any health problems. Nitrogen dioxide is responsible for irritation of the respiratory system. When atmospheric concentrations of nitrogen oxides are elevated and the intensity of sunlight is sufficient to form a photochemical cloud, symptoms and health impacts come mainly from ozone (O3). Ozone is the photochemical pollutant encountered in greater abundance at the onset of the phenomenon. Nitrogen oxides and ozone have significant effects on plant organisms. They cause stigma in the leaves and scorch of plant tissues. Nitrogen oxides also cause faster wear and aging in materials in the structured environment, such as discoloration in coatings and corrosion on metal surfaces. Finally, they still contribute to the creation of acid rain.

Impacts: Carbon monoxide is characterized as an atmospheric pollutant due to its effects on human health. Carbon monoxide affects the ability to transport oxygen to the blood. If it is in the air even in small quantities, it can significantly reduce the oxygen transferred from the blood. This will have effects on mental functions and increased heart rate in the body's effort to neutralize oxygen deficiency. At 2.5%, weaknesses in the perception of the duration of an audio signal are observed. At 10%, there are ailments and headaches. Percentages above 50% are considered deadly. In urban areas, carbon monoxide concentrations are often between 5 and 10 ppm, while vehicle drivers are often exposed to concentrations up to 100 ppm. Lead Pb Sources: Lead belongs to heavy and toxic metals. The lead level is the lowest of all pollutants, 0.5 μg / m3. The presence of lead is due to cars, although in recent years lead emissions from wheeled vehicles have declined worldwide by 98%. Another major source of lead in the atmosphere comes from metallurgical processes. Higher concentrations of lead in the atmosphere are currently found near furnace installations and battery industries.

Carbon Monoxide CO Sources: Carbon monoxide is a colorless, odorless and tasteless gas and is the one that is more abundant in the atmosphere than other atmospheric pollutants. The limit value for the protection of human health is 10 mg / m3 (maximum eight-hour average daily). Carbon monoxide is produced by the incomplete combustion of hydrocarboncontaining fuels, that is to say all fossil fuels, but also the combustion of wood. When combustion is incomplete, carbon monoxide is produced, while carbon dioxide is produced when complete. Since plant installations are strictly controlled for these emissions, the most important source of carbon monoxide emission is the different wheeled vehicles. About 70% of these emissions are due to them. Hourly atmospheric concentrations of carbon monoxide in an urban area often reflect peak traffic periods.

Impacts: The primary goal of lead is the central nervous system, especially for children and adults. It also affects every organ and body system. Concentration problems for adults, motor problems, anemia, nephropathies, blood pressure increase, pregnancy problems, and fertility problems have been identified in populations where elevated lead concentrations have been observed. Benzene Sources: Benzene is a colorless aromatic liquid which evaporates under ordinary atmospheric conditions and belongs to the 10

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

class of Volatile Organic Compounds (VOC). Benzene is toxic and carcinogenic. For these reasons, its limit value in the atmosphere is very low at 5 μg / m3. Benzene is produced by the petrochemical and chemical industry. It is also used as a solvent in the production of plastics, resins, paints, varnishes, etc. In the urban environment, a source of benzene is the circulation of wheeled vehicles, petrol stations as well as small-scale industries such as printing shops.

combustion by industrial installations, heating and wheeled vehicles. Another important source of Volatile Organic Compounds (VOC) release into the atmosphere is their use as solvents for the production of various engineered articles. Impacts: Most Volatile Organic Compounds (VOC) has a serious health impact as their increased acidity causes various forms of cancer. Other main impacts of the Volatile Organic Compounds (VOC) on the environment are their contribution to the greenhouse effect and photochemical ozone production in the troposphere.

Impacts: Long-term exposure to benzene has been associated with the development of blood cancers. It can also cause various forms of leukemia, myelodysplastic syndrome, lymphoma, etc.

Particulate Matters PM2.5 and PM10 Sources: Sources of particulate matters vary, may originate from the ocean surface where droplets containing various salts, such as sodium chloride, are generated by the effect of wind on the surface of the sea. Another type of source is volcanic eruptions, combustion, especially fossil fuels, and aerosol production that are products of anthropogenic emissions. The main source of particulate matter is the dust emissions from wind erosion. New research by Greek and foreign scientists has identified a whole list of dangerous heavy metals contained in African dust, which has invaded Greece more and more frequently in recent years due to the main desertification phenomenon recorded in the Sahara. According to measurements made in 2013 in Athens, dust traveling from Africa carries in our country poisonous substances such as lead (Pb), zinc (Zn), chromium (Cr) vanadium (V), arsenic (Ar) and nickel (Ni), dioxins and polyaromatic hydrocarbons but also residues of industrial pollutants and exhaust gases at fairly high levels. The issue is of great concern to the scientific community for the impact of the transfer of "toxic" African dust to human health and the environment, as African powder appears now in all lengths and

Trioxide O3 Sources: Ozone is the main pollutant produced in the atmosphere by photolytic reactions of nitrogen oxides and Volatile Organic Compounds (VOC). For the protection of human health, the target value is 120 μg / m3 (maximum 8 hours per day, not to be exceeded more than 25 days per calendar year on average over 3 years). Impacts: Ozone is a very powerful oxidant and therefore it affects the tissues of the lungs, reduces their performance, sensitizes them to other irritants, reduces their resistance and, more generally, the resistance of the body and can accelerate the aging of the tissues. It is irritating to eyes and mucous membranes. As mentioned above, it destroys the tissues of plant species and speeds up the pollination and deterioration of the building materials. Volatile Organic Compounds VOC Sources: The petrochemical industry and in particular the refineries are the main stable source of the Volatile Organic Compounds (VOC). Significant sources of Volatile Organic Compounds (VOC) are also considered 11

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

widths of Greece, and is expected to grow even further more in the future.

(CAFE program) estimates that PM2.5 levels are responsible for the loss of approximately 3,000,000 years of life in Europe and 288,000 premature deaths per year, mainly due to respiratory and cardiac problems. Airborne particles are susceptible to increased susceptibility to infections due to impaired body defence, respiratory tract inflammation, leading to impaired and difficult gas exchange. They are also responsible for causing inflammation in the lungs of the lungs and accelerating heart failure in patients with chronic heart disease.

Impacts: The particulate matters in the atmosphere have different sizes and shapes. That’s the reason they are characterized by their aerodynamic diameter. The magnitudes of the particulate matters range is from 0.0002 μm to 500 μm. The particulate matters enter, depending on their size, through the nasal cavity into the respiratory system. The smaller the diameter, the more they penetrate the human body. The most harmful dimensions for the atmosphere are those with a diameter of 2.5 μm and 10 μm. Particulate matters are extremely harmful atmospheric pollutants and are responsible for a number of respiratory diseases and a burden of heart disease. The European Union 2. C CLIMATE ANALYSIS OF ATHENS

The climate in Athens is mild, warm and temperate. According to Köppen and Geiger, this climate is classified as Csa.

Figure 1: World map of Köppen, http://hanschen.org/koppen/ 12

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

That explains the fact that winters are rainier than the summers in Athens. Also, the annual average temperature is 18.1 ° C. By taking a quick glance at the climate of Athens in Greece, one can observe that during the summer seasons, it will be easy to reach the comfort zone. From May to September the Dry Bulb Temperature is between 22oC to 26oC, which means that at the hottest months of the year the temperature is achieving the adaptive comfort according to ASHARAE-55. Also during the winter seasons, the amount of Global Horizontal Radiation

remains in a mid level, which means that the absorbed heat during the day will be released in the night when the temperatures will fall down, which can provide some passive heating strategies. Most important aspect for this research project is the air flow. According to the graph at figure 2 the wind velocity is between 2 to 4m/s. That means that the outdoor air flow is extremely low. And probably this can be one answer to the overheating issue but also to the concentration of polluted air in specific areas.

Figure 2: Climate of Athens, data obtained from meteonorm Based on the prevailing wind analysis, the results show that west and north-west wind is coming through the city. The diagram concludes that Athens isn’t a windy town. Wind rose analysis is as high as 7 m/s from south-west and west-north. Also according to the radiation analysis, the amount of radiation that the city receives,

especially at summer is extremely high, up to 1029 kWh/m2. These results reveal that Athens definitely has overheating issues and combined with the low amount of air flow, deteriorate the levels of air pollution. There is no wind speed to clear the polluted air as a result the pollutants are increasing and also sustained in the same area.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Figure 3: Wind and total radiation rose data obtained from ladybug plug-in and meteonorm 2. D Evaporative cooling system via towers

temperature to occupied floors of the building) will be 80% of the dry bulb – wet bulb depression (Tdb-Twb). The pressure has to be 50Pa to achieve an average droplet size below 30 microns.

The first step for the evaporative cooling strategy is to specify the location of the project and start an analysis for the site and the climate. Second step, as with any other cooling system, is to estimate the cooling loads, so the ‘size’ or capacity of the system can be determined. The cooling load arises from internal and external heat gains, which must be analyzed and then removed in order to avoid the risk of overheating. The first objective after this is to minimise this load.

The size of openings based on the air volume flow rate required to remove external heat gains. Temperature depression: Tt = Tdb - 0.8 × [Tdb - Twb] Tt: tower delivery temperature Tdb: ambient dry bulb temperature Twb: ambient wet bulb temperature (External temperature)

External heat gains arise from climate and micro-climate and are derived mainly from solar radiation and infiltration. To avoid the overheating risk, it is more useful to make an estimate of the possible ‘worst scenario’ external heat gains. This scenario, in a temperate climate, is usually a warm summer day under clear sky conditions. It has to be mentioned that, the external heat gains vary significantly depending on the time of the day and the orientation. According to this information, the total heat gains are known.

Convective cooling is based on the removal of heat by the movement of air. The equivalent sensible cooling achieved is given from the following equation: Qs = VHC × q × [Ti - Tt] Qs= sensible cooling (W) VHC= volumetric heat capacity of the air (≈1200J/m3K) q=air volume flow rate (m3/s) external temperature Ti: Tt: tower delivery temperature

For direct evaporative cooling via a tower, the air temperature drops in the tower (determining the effective supply air 14

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

The finalization of the number of nozzles required based on the calculation of the amount of water required (H2O) to reduce ambient air from the maximum dry bulb temperature anticipated to 1-2 oC below the design internal air temperature. There is a way to determine this, by establishing the difference in the absolute humidity of the external ambient air and the absolute humidity of the air in the tower, multiplied by the air volume flow rate. The equation is the follow: H2O=ΔMR x q x

ρair ρH2O

With higher air flow rate, the polluted air will be replaced with fresh air from the upper sky levels. This research is orientated in a way to determine the following objectives. a) To use field data to compare the emissions of the polluted air at the selected area to the emissions from the Air Pollution Stations. b) To determine the area that the new structure will be placed and will be tested. c) To search and determined the height of the structure according to the proper simulations. d) To understand, completely the evaporating cooling methods and formulas for towers and then, apply them on the new structure based on the weather data, the simulations and their results. e) To finalize the shape, height, volume and number of the structure. f) To use CFD to determine the air flow and direction of the produced fresh air. g) To understand in which range this structure can distribute the air flow rate. h) To use CFD to test how, more than one structure will react between them on the selected area.

x [3,600]

H2O= the water required (l/h) ΔMR is the increment in air moisture content (gH2O/kgair) q is the airflow rate (m3/s) ρair is the air density (≈ 1.2kg/m3) ρH2O the water density (1000kg/m3) These are the basic steps to estimate and create an evaporative cooling system via tower.

3. Research methodology

Questions

and

3.1 Scope The scope of this thesis is to analyze the climate of Athens, to investigate all the aspects and the reasons that cause the major problem of air pollution, to understand the serious and dangerous impacts of the pollutants on the human health and finally through the evaporating cooling for towers strategies find a solution to provide fresh air. The research will be based on a new structure, which is created to go above the levels of air pollution and based on the temperature difference, between the temperature on the ground level and the temperature on the highest level of the structure, above the pollutants, through the evaporating cooling, air flow will be created.

3.2 Methodology The methodology is divided into seven major portions, a) Literature review. b) Fieldwork. c) Phase I: Finalizing the shape, height and dimensions of the tower d) Phase II: Performance of air distribution

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

e) Phase III: Operative hours of the tower device f) Phase IV: Performance of the tower on the selected areas g) Phase V: Performance of more than one tower devices

The first Phase will be based on the temperature difference, which will be found from Tt = Tdb - 0.8 × [Tdb - Twb] formula, and according to other formulas is going to test the tower’s performance. They will follow a range of different testes, with different shapes, heights and volumes. The performance of the tower, based on the size, height and shape of the tower, which will show the best performance, will be the base study for the next Phases. In other words, this is the Phase, which will determine the shape, height and dimensions of the tower by using all the necessary data.

The results from the simulations will be based on the literature review, on the measurements from the fieldworks and on the annual weather data. By using much software such as meteonorm, Rhinoceros, the plug-in of Grasshopper, Ladybug and Honeybee, by using CFD for the wind analysis this study will be able to provide accurate and valid numbers and documents for the new structure.

3.2.4 Phase distribution

II:

Performance

air

By adopting the final shape, height and dimensions of the tower at this stage of the project will be tested the performance of the air distribution. These tests will be use different velocities as an inlet air velocity of the tower device and they will present the mutual dependence of air velocity and air distribution. Also, on Phase II it will be determined the lowest acceptable air velocity that the tower can achieve with only one purpose, to keep the device active only when it’s effective and beneficial.

3.2.1 Literature review An understanding of the emissions which exist in the polluted air, which are their sources, the hazardous impacts on human health, the climate of Athens and the help that evaporative cooling strategy can provide a more reliable theoretical fundamental basis. 3.2.2 Fieldwork

3.2.5 Phase III: Operative hours of the tower device

The study is primarily limited by lack of ability to travel in Athens very often to measure the amount of the basic emissions that are included in polluted air In order to fulfil the aforementioned objectives. For this study, have been selected two different areas to take the necessary measurements. The fieldwork trips took placed on May, because it's still spring and the temperature isn't on the highest levels and is a neutral season. That means that all the citizens are in town (they don’t leave the place for vacations) and the tourism period is on.

The third Phase is based on all the above results and condition, and by adding some more it will finalize the operative hours of the tower device during the whole year. At this stage of the thesis project will be optimized all the important information for this project, such as the temperature difference for each hour of the year, the air velocity that goes out of the bottom of the tower device for each hour of the year, the annual amount of fresh air that the tower device can produce and the exact amount of people whom the tower device can provide with fresh air. Also, Phase II presents the annual water

3.2.3 Phase I: Finalizing the shape, height and dimensions of the tower 16

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

consumption that the tower needs to proceed on the procedure of the evaporation. And finally, the operative hours during the whole year that the tower should be open, so it can be effective and beneficial.

Which are the formulas that can estimate precisely all the necessary data? Fieldwork Which are the worst polluted areas in Athens according to the Pollution Station? Are these areas responding on this decision according to the spot measurements? What these numbers, from most of the types of pollutants mean for the human health in each selected area? Case study project Which size, height, dimensions and volume are the proper for the tower device to performance the best version of it? From which amount of air velocity that the tower relieves is enough to distribute the fresh air? What is the exact range and performance of the air distribution? Is it proper for the tower to be open for each hour of the year? How is it going to fluctuate all the annual data according to the previous questions? Which would be the image of the tower performance if it would be placed in a realistic area? How more than one tower will affect the area and how two or more towers will react to each other?

3.2.6 Phase IV: Performance of the tower on the selected areas The next Phase will be based on all the previous results and conclusions to test the performance of the air distribution of the tower device on the selected areas. But this time, it will be based on the precise annual results, which will be optimized on the previous Phase. 3.2.7 Phase V: Performance of more than one tower devices The next and final test it will examine the performance of the air distribution on the selected areas and the effect when at the same area more than one tower will be active. This is crucial, because in the case that the previous Phases will present beneficial results, then the major subject will be to make sure that by adding towers in a row, on the proper distance, it will be created a network of tower devices that can provide fresh air for all the citizens at the same time.

3.2.4 Hypothesis 1. Thesis expects to fully understand the evaporative cooling of a tower device and also to give a solution on the air pollution that infest the citizens of Athens. 2. This project will be cover as many aspects it can, to estimate precisely all the necessary data and to ensure that the procedure will truly effective, feasible, helpful and most important friendly to the environment.

3.3 Research questions This thesis is using a range of questions as they lead force for each part of this project as follow. Literature Review: What are the factors that cause the air pollution? How these factors are influence the environment and the well-being? Which is the worst pollutant for the human health? What are the consequences of the worst pollutant for the human health and the longevity? How, through evaporation, this condition can be improved? What exactly is the evaporative cooling and especially for towers?

3.2.4 Outcomes This is a research based study with an expected outcome of achievement of more effectiveness of the evaporative cooling in the tower. Because, on this way the levels of polluted air can move to another place and even better to guide in a place which can absorve the pollutants and reduce them. 17

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Another possibility is that the tower except the fact that it cans more the polluted air in a different place, it can also replace it with fresh air. Also by achieving this, through the evaporative cooling, it is possible to reduce also the extremely high temperature on ground level by providing temperature closest to the one on comfort zone. This will be extremely helpful as in Greece the summer lasts for at least 6 months per year. But the most important result of all is going to be the reduction of deaths, the respiratory problems and in other words, the improvement of human health and air quality.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

4. Fieldwork 4.1 Context 4.2 Fieldwork on sunny day 4.3 Fieldwork on cloudy, windy day

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

4.1 Context According to the air pollution station in Athens, the first two areas with the highest amount of pollution are Syntagma square, the biggest and most important square in the capital and the second one in Ampelokipoys. Ampelokipoi, is a huge area in Athens, but the spot with the worst polluted situation is a roundabout 2km far from Syntagma that connects four of the most

important, big and multipurpose streets in Athens. Based on this information from the national air pollution station in Athens these were the areas selected for the fieldwork of this project.

Figure 4: Two selected areas in Athens

Figure 5: First Syntagma square

selected

area: 20

Figure 6: Second selected area: Ampelokipoi roundabout

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

The measurements took place in two different days. The first day was a sunny day and the second one was cloudy and windy day. As it was expected the measurements showed differences on the pollution levels.

4.2 Fieldwork on sunny day As the results show, on the sunny day, in Syntagma the pollution is worst than it is in Ampelokipoys. Especially the PM2.5 and PM10 emissions, which are the most harmful pollutants for human’s health, are increased in that area.

Figure 7: Spot measurements of sunny day.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

The explanation for that is simple. First of all Syntagma is achieving more than 100.000 visitors per day comparing to Ampelokipoys which has as visitors only means of transport. There is a metro station which is used from 3 different metro lines and also more than 5 bus stations around the square. Another possible reason is that Syntagma square is located 9 meters lower than the main

road and it’s surrounded by big walls, so it is possible that all the polluted air remains trapped there. It is important to be mentioned that the square also is surrounded by a big main street, which is very busy during the day and night as the square is located in the centre of the city.

Figure 8: Problems and limits of Syntagma square 4.3 Fieldwork on cloudy, windy day The results on the cloudy day are even more interesting from two different aspects. Comparing the two selected areas between them but also comparing the sunny day to the cloudy day.

Comparing the sunny day to cloudy day it is obvious that in Syntagma square all the emissions decreased except PM2.5 and PM10. On the other hand, most of the emissions in Ampelokipoys are increased. It is important to be mentioned that when the measurements have been taken, there was African dust that specific day. That fact explains why the amounts of particulate matters that cloudy and windy day were extremely high comparing to the amounts of the previous sunny day. As it was mentioned before African dust is the cause of the 70% increasing of particulate matters in Greece. Another fact is that in Syntagma square the

Comparing the two selected areas between them on a cloudy day all the pollutants in Ampelokipoys are higher than Syntagma square except PM2.5 and PM10, just like the sunny day. This is common because most of them are caused by the means of transport. Also, again the emissions of CO and CO2 are higher in Ampelokipoys again because of the daily traffic on that roundabout.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

temperature difference is 4.7 oC and the wind velocity difference is 1.8 m/s. On the other hand in Ampelokipoys the temperature difference is 2 oC and the wind velocity difference is 0 m/s. That explains the fact that in the second selected area the amount of the emissions increased when on the first selected are was decreased.

Figure 9: Spot measurements of cloudy, windy day

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

5. Case study project 5.1 Introduction 5.2 Phase I: Finalizing the shape, height and dimensions of the tower 5.3 Phase II: Performance of air distribution 5.4 Phase III: Operative hours of the tower 5.5 Phase IV: Performance of the tower on the selected areas 5.6 Phase V: Performance of more than one tower devices

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

5.1 Introduction As it was mentioned before, this is a collaborative thesis project. There was the option to select between two different scales, the urban and the domestic scale. And its option had another three options, which was a thesis project by its own. This specific thesis is going to focus on the first option of unban scale’s selections which is the modelling behaviour of different sizes and geometries (Figure 10).

The unban scale as a theme, is about a tower with unclear yet height, size and shape and it’s going to provide fresh air from the sky (above the urban canopy layer) to the ground level, by inducing a natural downdraught air movement through evaporation (Figure 11 & 12). At the same time, it can offer to users the possibility of less temperature especially at summer, while providing a cooler air temperature in that period.

Figure 10: Chosen project

Figure 11: First idea of the project 25

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 12: Procedure of evaporative cooling and tasks Typical evaporative cooling tower lowers temperature through evaporation of water vapour into the air.

information based on the height and the dimensions of the tower. It is known, that all the above results that are needed for the process of this thesis depend on the shape, the aperture on the top and bottom and of course the height of the tower.

An evaporative cooling tower is a structure optimized for cooling water and fluids. It operates on the evaporative cooling principle where absorption of energy needed to form water vapour leads to a drop in temperature. The evaporating water absorbs heat from the remaining water thus lowering its temperature. This temperature difference will create the movement of the air, in other words it will create air flow rate on the bottom of the device, as the cooler air goes down and the hotter one goes up. According to researches based on that specific topic, there is a series of steps to estimate precisely the decreased temperature, the temperature difference, the air flow rate that is created on the top and bottom of the tower, the pressure inside and outside the tower, the humidity inside the tower and all the necessary 26

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

5.2 Phase I:

maybe the most important, the air velocities of the inlet and the ground level. The radius of the inlet area on the top and outlet area on the bottom is 3.10m and 5.65m, respectively. The area of the inlet is 30.20m2 and the outlet area 100m2. It is known that ρ=1.2 kg/m3, g=9.81kg/m2 and Cd=0.8. Based on these information and the equations that will follow, it is precise to estimate the performance of its type of tower.

Finalize the shape, height and dimensions of the tower To be finalized the height, shape and volume of the tower, in this thesis were tested six different scenarios. These scenarios have different heights, dimensions and shapes. Also, they have different inlet and outlet areas on the top and bottom respectively, which is maybe the most important factor for the tower’s performance. For the first scenario the tower is 10m high, and is 5m above

Figure 13: First scenario: Ain=30.20m2, Aout=100.00m2, H=10m These equations were used to estimate the temperature difference, the density of the outside, the density difference, the pressure difference across openings, the airflow rates of the inlet and outlet tower’s areas and

outlet area of its hour of the whole year. According to the yearly results, the tower’s air velocity (on the outlet area on the bottom) is higher during spring with maximum amount on 0.36m/s on March, 27

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

which isn’t the best performance that the tower can provide. So, it is

realistic and applicable, this is 25m. All the other information is the same.

necessary to move forward to the second scenario of the Phase I. On this scenario the only change is the height of the tower. It is given the highest height that can be

Figure 14: Second scenario: Ain=30.20m2, Aout=100.00m2, H=25m According to the yearly results, the air So, on the third scenario, the radius on both, velocity (of the outlet area on the bottom) is inlet and outlet will be 3.10m, the both areas increasing when the height is increasing too. will be 30.20m2 and also it will be valid that But again, the performance of the tower with ρ=1.2kg/m3, g=9.81 kg/m2 and Cd=0.8, these specific dimensions isn’t so effective. which are standard numbers. After the area That conclusion leads to the next step. The of the inlet and outlet areas, the second main third scenario is changing the radius and factor is the height of the tower and now for areas of the inlet and outlet areas of the this scenario it will be 10m. tower. On the first and second scenario it was valid that Ain<Aout, now on the third and fourth scenario it will be valid as Ain=Aout (when these areas are equal the results will be the same, regardless the exact amount). 28

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 15: Third scenario: Ain= Aout =30.20m2, H=10m According to the annual results, when Ain=Aout, even if the height is decreased, the performance is better than before. Based on the graph, again the tower appears the highest air velocity on March with 0.88m/s and the lowest on September with amount to 0.53m/s. So, the conclusions until now are a) that the highest height gives better performance and b) that when is valid that Ain=Aout it is way better than Ain<Aout.

Fourth scenario is about a tower with radius 3.10m on the inlet and outlet areas on the bottom and top, respectively. For the area of the inlet and outlet areas, is valid that they are equal to 30.20m2 (Ain=Aout). The only change comparing to third scenario is the height, which is going to be this time 25m. All the other information is the same as before, because they are standard numbers.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 16: Forth scenario: Ain= Aout =30.20m2, H=25m Based on the annual results for the fourth scenario, when the area of the inlet is equal to the area of the outlet and also the height is bigger the performance is even better than before. The air velocity on the outlet (on the bottom of the tower) is increased a lot and now on March the highest amount is 1.40m/s, while the lowest air velocity is again on September and is around to 0.83m/s. The conclusion again, is that the height of the tower is probably the main factor for the good performance of the tower.

But what is going to happen if the inlet area is bigger now than the outlet area? This is the next and last test and it leads to the fifth and sixth scenarios. The fifth scenario is about a tower with radius 5.65m on the inlet area (on the top of the tower) and area as 100.00 m2 and as radius and area for the outlet area (on the bottom of the tower) 3.10m and 30.20m2 respectively. The height for this test is going to be again 10m, which is the minimum height that the device can have and also all the other information remains the same as they are standard numbers.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 17: Fifth scenario: Ain=30.20 m2, Aout =100.00m2, H=10m According to the annual results from the graph, it is obvious that with the lowest amount of height the performance is really improved when the inlet area (on the top of the tower) is bigger than the outlet area (on the bottom of the tower). March again is achieving the highest amount of air velocity with 1.20m/s and September is achieving the lowest with 0.71m/s. Even though the results are worse than the fourth scenario the performance is improved a lot according to the height which was set. To sum up, the results are even better when is valid that Ain>Aout.

Based on these conclusions, the final step for Phase I is to test the best range between the inlet and outlet areas and the maximum height that the tower can reach. The sixth scenario is about a tower device with radius 5.65m on the inlet area (on the top of the tower) and area as 100.00 m2 and as radius and area for the outlet area (on the bottom of the tower) 3.10m and 30.20m2 respectively. The height for the final test is going to be 25m, which is the maximum height that the device can reach and also all the other information remains the same as they are standard numbers.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 18: Sixth scenario: Ain=30.20 m2, Aout =100.00m2, H=25m This image illustrates the best performance that the tower device can reach. On this height (25m) the air velocity of the outlet area (on the bottom of the tower) is close to 2 m/s on March, when on September is reaching the amount of 1.13m/s as minimum number. This scenario is a really strong proof that maybe the tower device could be effective and active even on the winter. To sum up, two are the main points of Phase I: a) when the inlet area (on the top of the tower) is bigger that the outlet area (on the bottom of the tower) the performance of the device is improving dramatically. And b) the higher height the tower reach the better results are going to show.

Based to all these results, the best performance of the tower is when the device has the following characteristics: a) radius inlet is 5.65m, area of inlet area (on the top of the tower) is 100.00m2, c) radius outlet is 3.10m, d) area of the outlet area (on the bottom of the tower) is 30.20m2 and final e) the height is 25m.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Figure 18: Final shape: Ain=30.20 m2, Aout =100.00m2, H=10m

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

5.3 Phase II Performance of air distribution The Phase I is completed, the shape, dimensions and the height of the tower are finalized and the thesis can now proceed to the Phase II, which is about the performance of air distribution. For the precise understanding of the distribution of the air through the tower device, it is needed to simulate that on the Computational Fluid Dynamics by using a variety of different air velocities.

For this project, at this level of procedure and based on other similar case studies, it was decided that no less than 1m/s air velocity would be effective or worthy. So according to that, the first test is simulated with stable air velocity of 1m/s. It is important to be mentioned that the tower device is placed five meters up from the ground and also the inlet and outlet areas are 100.00m2 and 30.20m2 respectively.

60 m

80 m

Figure 19: First hypothesis: air velocity 1m/s The first image is about a plan-section that was taken 1m from the ground. Also it is significant to be mentioned that the all the

simulations in Phase II took place in an environment without context. According to CFD results, when the velocity is at 1m/s the air is distributing uniformly around to 60m on 34

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

the horizontal level and at least around to 25m on the vertical level. But the air flow rate is dramatically low up to 0.2-0.4m/s.

Figure 20: Air movement It is really interesting for someone to notice the direction of the air. From the second section on the last figure it is obvious that the air is moving like a turbine through all the orientations. Also, in humanâ&#x20AC;&#x2122;s level (up to 2 meters) the air velocity is 0.6m/s based on the section above.

These results lead to the next step, which is running the same simulation, but this time with higher velocity. Again the environment is without context, the plan-section is taken 1m from the ground and the velocity now is 1.5m/s.

Figure 21: Second hypothesis: air velocity 1.5m/s 35

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

From the CFD results, it is obvious that this time even with an environment without context the air isn’t distributing uniformly as it was expected to be. The range of the air distribution is almost the same as it was on the first hypothesis. In more detail, it is up to 65m on the horizontal level and more than 25m on the vertical level. Also, to be easier to compare the previous results with the new ones, in every plan-section it is marked the

area of the distributed air with air velocity to 0.6m/s. As the figure shows the results aren’t that much better. Even with higher velocity the air flow is still low. On the ground level, the velocity is up to 0.6-0.8m/s However, there is an increasing on the air velocity on the ground and human’s level (up to 2 meters), as it reaches now the velocity of 0.8m/s. The next section illustrates the orientation of the distributed air, which is again like a turbine, as it was expected to be.

Figure 22: Air movement The third hypothesis tests the same conditions as before with only change the velocity. The simulation now runs with air velocity at 2m/s. As a conclusion, based on the previous results, when the tested inlet velocity is getting higher, then the outlet velocity on the ground and on the human’s level (up to 2 meters) is getting higher too.

As the figure presents the results aren’t that much different. However, there is an increasing on the outlet air velocity. On the ground level, the velocity is up to 0.7-0.9m/s and on human’s level (up to 2 meters); it reaches the velocity of 0.8-1m/s, which is a noticeable and effective amount. The second section illustrates the orientation of the distributed air, which is again like a turbine, as it was expected to be. This air movement explains the shape of air distribution on the plan-section, which is not distributing uniformly.

According to the next section, again the air isn’t distributing uniformly as it was expected to be and the range of the air distribution is a bit bigger than the previous hypothesis. In more detail, it is up to 65m on the horizontal level and more than 25m on the vertical level, but with higher velocities.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

0.6 m/s on previous simulation

Figure 23: Third hypothesis: air velocity 2m/s

Figure 24: Air movement

The next hypothesis examines the same conditions with higher velocity, up to 2.5m/s.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

70m

0.6 m/s on previous simulation

Figure 25: Forth hypothesis: air velocity 2.5m/s level and more than 25m on the vertical level (up to 2 meters). On the ground level the velocity is up to 0.8-1m/s and on human’s level (up to 2 meters) it reaches the 1-1.2m/s of velocity, which is something, more than effective and noticeable.

Based on the results, the air isn’t distributing uniformly but the range of the air distribution a lot bigger than the third hypothesis. As the plan-section shows, the distributed area is twice bigger; it covers more than 70m on the horizontal

Figure 26: Air movement

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

The second section illustrates the orientation of the distributed air, which is again like a turbine, as it was expected to be. This air movement explains the shape of the air distribution on the plan-section, which is not distributing uniformly.

device covers. That leads to the next hypothesis, which is tested at the same conditions and velocity at 3m/s.

0.6 m/s on previous simulation

75m

Figure 27: Fifth hypothesis: air velocity 3m/s The second section presents the orientation of the distributed air, which is again like a turbine, as it was expected to be. This air movement explains the shape of the air distribution on the plan-section, which is not distributing uniformly. It’s concluded that the higher velocity is been set the higher velocity the tower device provides on the human’s level (up to 2 meters), which is really important, especially on the hottest months of summer. They are following two more hypotheses for the performance of the air

According to the results, the air isn’t distributing uniformly but the range of the air distribution is a bit bigger than the previous test. As the plan-section shows, the distributed area covers more than 75m on the horizontal level and more than 25m on the vertical level (up to 2 meters). On the ground level the velocity is up to 0.8-1m/s and on human’s level (up to 2 meters) it reaches the 1.4-1.6m/s of velocity, which is really effective and noticeable amount. It’s concluded that the higher velocity is been set the bigger area of distribution the tower 39

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

distribution, as the maximum velocity that the tower can achieve is up to 4.5m/s,

according on the weather data and the equations of Phase I.

Figure 28: Air movement The fifth test simulates the same conditions, with higher velocity, up to 3.5m/s.

78m 0.6m/s on previous simulation

Figure 29: Sixth hypothesis: air velocity 3.5m/s

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

According to the results, the air isn’t distributing uniformly but the range of the air distribution is much bigger than the fourth test. As the plan-section illustrates, the distributed area covers more than 75m on the horizontal level and more than 25m on the vertical level (up to 2 meters). On the ground level the velocity is up to 0.8-1.2m/s and on human’s level (up to 2 meters) it reaches the 1.2-1.6m/s of velocity, which is really effective and noticeable amount.

The second section presents the orientation of the distributed air, which is again like a turbine, as it was expected to be. This air movement explains the shape of the air distribution on the plan-section, which is not distributing uniformly. It’s concluded that the higher inlet velocity is been set the bigger area of distribution the tower device covers.

Figure 30: Air movement The next scenario examines the same conditions, with higher velocity up to 4m/s. Based on the simulation, the air isn’t distributing uniformly but the range of the air distribution is much bigger than the sixth test. As the plan-section illustrates, the distributed area covers more than 75m on the horizontal level and more than 25m on the vertical level (up to 2 meters). On the ground level the velocity is up to 1-1.2m/s and on human’s level (up to 2 meters) it reaches the 1.4-1.6m/s of velocity, which is really effective and noticeable amount.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

78 m

0.6m/s on previous simulation

Figure 31: Sixth hypothesis: air velocity 4m/s

Figure 32: Air movement

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

The seventh and last hypothesis tests the same conditions as before, with air velocity at 4.5m/s.

78 m

0.6m/s on previous simulation

Figure 33: Seventh hypothesis: air velocity 4.5m/s According to the results, the air isn’t distributing uniformly but the range of the air distribution is much bigger than the sixth test. As the plan-section illustrates, the distributed area covers more than 75m on the horizontal level and more than 25m on the vertical level (up to 2 meters). On the ground level the velocity is up to 1-1.2m/s and on human’s level (up to 2 meters) it reaches the 1.4-1.6m/s of velocity, which is really effective and noticeable amount.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 34: Air movement To sum up, based on all the sections that illustrate the air movement, it is obvious that when the air velocity is increasing turbines are created. That means that the air isnâ&#x20AC;&#x2122;t distributes uniformly. Also, as long as the air velocity, which is used on the inlet area of the tower is increasing, then the air velocity on the outlet and the distributed area are increasing too.

All the previous results, lead to some limits and conditions for the tower device and for its operation hours. As it was mentioned before, when the air velocity is below 1.5m/s, it is non-effective for the tower to be in operation. So, from the weather data analysis and with all the previous results, it is needed to create some conditions to estimate the operative hours of the whole year for the tower device.

Figure 35: Conclusions of Phase II

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

5.4 Phase III Operative hours of the tower On Phase I, it was gathered most of the most value information for the progress of this thesis. It is known the temperature difference between the tower and the outside, the density of the outside and the density between the outside and inside the tower, the neutral plane, the pressure difference across the openings, the airflow rate on the outlet and inlet area of the tower and also, the air velocity of the outlet and inlet area of the tower device. On Phase II, it was revealed the exact performance of the air distribution on the same conditions but on different velocities. According to the results of both Phases they were created some conditions that help on the procedure of finalization of operative hours of the tower devices.

of the operative hours. These factors it is needful to be analyzed and be estimated precisely. Only on that way, all the necessary data would be gathered for each hour of the whole year, and then it would be feasible to peak only the hours, which obey on the old and new conditions, among to the hours of the whole year. Based on these, as a followed step, it is extremely important to be estimated the relative humidity inside the tower, the water vapour saturation pressure, the vapour pressure, the absolute humidity, the absolute humidity difference between the outside and the inside of the tower device. Also it is attainable to calculate the evaporative water and of course the water consumption. To calculate all these, the thesis will be based on the following equations.

Even though there is a lot of information to move on to the Phase III, there are more factors that can influence the effectiveness

Figure 36: Final part of equations

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

By applying these formulas for each hour of the year and combine these results with those ones of the Phase I, it is now feasible to predict the operative hours of the tower device by adding one more condition. Except this, it is possible to predict also and optimize the ΔT, the fresh air that the tower device can produce, the amount of people that the tower can cover and also its water consumption. All the hours that they’re having as result negative numbers on the evaporative water, need to exclude. When the results are mines, means that the

evaporation is not happening when the weather conditions are not hot and dry. In other words, in these cases the tower device cannot moisture the environment more than it’s already moisture. By presenting the annual results of each hour of the year in graphs, based on the formulas it is easier to compare the data and based on the conclusions to decide which hours of the year the tower device needs to be open.

Figure 37: Annual results of operative hours for the whole year are having place rare. The lowest amount of operative hours are showed on December and January, which is totally correct as it is winter and the rainfalls are having place really often, so the environment is already evaporated, so the tower device cannot evaporated it more. Cumulatively, the tower device is operated for 4212 hours per year. Considering that the whole year contains 8760 hours, it seems that the tower device can be opened, effective and useful almost half of the year. Another benefit from these results, is that the device it is able to be operated during the whole year and producing fresh air for the citizens and also cooler air especially at summer season, which is necessary.

Based on the conditions from Phase I until now, it comes up that these are the hours of the year that the tower device can be open and most important effective and useful. As it is obvious from the graph, on July the tower device presents the best performance, as it can be opened for 507 hours. The operative hours start to count from 8:00 in the morning until 24:00 at midnight. The operation is extremely good on March, April, May, June and August as it’s spring and summer season during these months and the weather is hot and dry, so the evaporation system is working perfectly. Even on September, October and November the performance of the tower illustrates many hours of operation and the reason is that on these months the rainfalls evaporative water 46

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Figure 38: Annual results of ΔΤ for the whole year (1st graph) and for the operative hours (2nd graph). On the other hand, on October, November, December and January, the tower presents the worst performance. And the reason is that then, as it was mentioned before on the climate analysis, in Greece, as season, it’s autumn and winter, which means that the climate is really moisture cold, because of the daily rains. The results of December are the worst, as it contains the less operative hours. On this month the average number for the ΔT difference is about 2.4 oC. It is important to mention that the ΔT is totally related with the air flow rate, so the higher ΔT difference is the higher air flow rate the tower device will produce.

According to all the conditions from Phase I until now, these are the results of the ΔT for the operative hours of the tower device (all the hours which are not following the conditions are excluded). The second graph illustrates that on July the hours that the tower can be open are the most and also the average number of ΔT difference is 7oC. The evaporation on that month starts at 8:00 in the morning and it’s working almost every day until 24:00. Really effective performance it appears on February, March, April, May, March, June and a bit on August and September. These results are totally correct and understandable, as it is known that on these months in Greece the weather is extremely hot and dry. That means that the tower device it is logical to have more operative hours.

After the optimisation of the ΔT difference it follows the graph of the relative humidity.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 39: Annual results of Relative Humidity for the whole year (1st graph) and for the operative hours (2nd graph). Comparing the previous graphs with these ones, it is clear and totally acceptable that when the temperature difference is high then the relative humidity is low and when the temperature difference is low the relative humidity is high. So, based on that comparing the graphs on Figure 39, it is obvious that all the hours with extremely high humidity are excluded. This is happening because, as it was mentioned before when the environment is already moisture (usually when the humidity is more than 80%) the tower device cannot evaporate it more. The reason for this is that for direct evaporative

cooling via a tower, the air temperature drops in the tower will be 80% of the dry bulb â&#x20AC;&#x201C; wet bulb depression (Tdb-Twb). As it is obvious, all the data results until now, they seem to be complementary to each other. Another way to confirm that, it was to plot, except the relative humidity, the results of cloud cover fraction and precipitation. The following two graphs are immensely connected between them but also with the relative humidity.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Figure 40: Annual results of Relative Humidity for the whole year (1st graph), annual results of Precipitation (2nd graph) and annual results of Cloud Cover Fraction (3rd graph) Comparing these three graphs, it is more than visible that they look like a connected chain. When the relative humidity is extremely high (80% or more) then the precipitation is high too. It is obvious especially during the winter (January, February) that the rainfalls would be often, so the humidity will be higher, so the precipitation and the cloud cover fraction.

On the above graphs there are marked two different examples. The first one is on March, one of the worst months because of the rainfalls, even if it is the first month of spring. On this month the 1/3 of the days it’s raining. The marked days on the graphs show that when the humidity is extremely high, then the precipitation is high too and the sky is covered with clouds. The second example is taking place on July, which is one of the hottest months of summer. In that case, it’s not raining of course but it’s a lot humid. Also, the cloud cover fraction on this example 49

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

is receiving the highest amount of oktas (8 oktas). According to the climate analysis, this two months and December too, are achieving

the highest amount of water, which explains all the previous results

Figure 41: Climate analysis, cumulative rainfall. Another interesting founding from these formulas is the annual results of the fresh air that the tower device can produce during the operative hours.

Figure 42: Annual results of fresh air that the tower can produce during the whole year. It is known that one person needs 10l/s of fresh air. According to the results, the tower device can produce 10,070l/s per hour as minimum amount and as maximum 100,0707l/s per hour. It is remarkable that even with the lowest amount of production of fresh air; the change of the pollutant air can be improved rapidly.

As it was mentioned on the literature review, in Athens the citizens have to suffer from the diseases and the respiratory problems that the pollution is causing to them. The above chart is proving how much optimistic, helpful and promising that tower device can be for their health and wellbeing.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

In order to understand better the benefits of the previous graph, it is necessary to optimize the results of the exact people that the tower device can cover per hour with fresh air.

Figure 43: Annual results of persons that the tower device can cover with fresh air during the whole year. Based on the graph and also on the fact that each person needs 10l/s of fresh air, it is impressive that the tower device can produce fresh air for 1007 persons per hour, when it’s reaching the lowest performance of it. And it’s extremely remarkable that when the tower device produces the highest amount of fresh air, in one hour can cover 10,070 persons.

One of the most major conditions, of the finalization of the operative hours is the water consumption. It is crucial to estimate how many litres of water the tower device needs to proceed on the evaporation. As it was mentioned before, when the numbers are negatives, it means that the tower device is unable to complete the procedure.

Figure 44: Annual results of Water consumption for the operative hours.

Figure 45: Annual results of ΔΤ for the operative hours.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

It is well known that one person, in Europe, consumes 150-250 litres per day. In some countries the supply of water it can be unobtainable. In terms of environmental design, it is main duty to make sure that this project won’t burden the existed conditions of the environment. In Greece, the supply water never was a concern, because the supplies are many. At this stage of the thesis, it is crucial to estimate the exact amount of the needed water that towers has to use to proceed on the evaporation. It is important to be mentioned that with the appropriate equipment this device can operate with seawater, which is the best and most appropriate solution.

According to the results, the graph on Figure 44, illustrates the exact amounts of the needed water that the tower needs to consume for the evaporation procedure. The minimum amount of litres per hour is around to 25.84l and the maximum to 266.68l. To understand these results it is necessary to estimate how much water the citizens of Greece need per day. In Greece the population is around to 10,000,000 people. That means that the Greek population needs 1,500,000,000-2,500,000,000l per day. The annual amount of the water consumption of the tower for the operative hours is 139,990 litres, which very small amount comparing to the benefits and the daily consuming of the people.

Figure 46: Water consumption of each month for the operative hours. The above image, illustrates the needed water for each month of the year for the operative hours that the tower has to consume to proceed on the evaporation. The costs, according to the numbers, it’s very small, comparing to the benefits of this project. The advantages of this project could be even better if the tower device consumes seawater.

device needs to consume more water is because the temperature difference is higher too (Figure 45). As higher the temperature difference is the more water is needed to be consumed from the tower to evaporate the place. Another domain that this analysis can approach is the air velocity on the outlet of the tower. The air velocity on the outlet of the tower is a major field because it’s involved with the distribution of the air. It is clear that as much higher is the air velocity that the tower device releases, the biggest distribution can achieve at the area that the tower device will be placed. From Phase I, it is already known that the air velocity will be above the 1m/s.

Also, based on Figure 44 and 46, it is clear that on April, May, June and especially on July, the evaporative water reaches the highest amounts. This is perfectly reasonable, as on these specific months the tower device gets the most hours of operation. Another reason that on these months the tower

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Figure 47: Annual results of the air velocity on the outlet area of the tower device. highest degrees difference, the air velocity achieves to 3-3.33m/s, which is the highest amount that it can achieve. The same proportional is happening on the water consumption’s graph on the same month (Figure 45).

This annual graph, presents the air velocity of each hour of the year that the tower device will produce on the outlet area. According to the conditions and on the graph’s legend the boundaries of the outlet air velocity of the tower device will be 1-3.33m/s. As it was expected, from the formulas on Phase I, the air velocity is proportional to the temperature difference. In other words, when the temperature difference performs high results then the air velocity will reach high results too. Comparing Figure 45 with Figure 47 this is even more conceivable. For example on July, when the temperature difference reaches 8-9oC, which is almost the

The last graph is maybe the most crucial one, because as it was mentioned before the air velocity of the outlet area of the tower is in charge for the fresh air distribution. And this conclusion leads to the next step of this project, which is the performance of fresh air distribution on the selected areas.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

5.5 Phase IV

air during the whole year and not only at the summer that it was expected. And finally, the air velocity of the outlet area of the tower is the key for the performance of the air distribution and this time on the selected areas.

Performance of the tower on the selected areas From Phase III, comes as result some thoughtful conclusions. All the annual results are proportional to the temperature difference except the relative humidity that has the opposite effect. This conclusion was expected based on the formulas, the physics, and the maths. The tower device can produce as minimum 10,007l/s of fresh air, which is enough for 1007 people (one person needs 10l/s per day) The tower device needs, as maximum amount of litres, 266.68l when a European citizen consume 150-250l per day, which is a really small cost comparing to the benefits. Also, the tower device through the evaporation can be opened and provide fresh

The first thing that itâ&#x20AC;&#x2122;s needed to proceed on the Phase IV, is to predict the most frequent air velocity that it appears through each of the operative hours. From Phase II and Phase III, it is known that the air velocity is above 1.5m/s and below 3.5m/s. According to these, on that stage was estimated how many of the operative hours achieve air velocity from 1.5-2.5m/s and how many of the operative hours reach from 2.5-3.5m/s. On that way, the air velocity which will be used on the following simulations will be revealed.

Figure 48: Statistics of the most frequent air velocity. The first selected area is in Syntagma. It is about the biggest and most important square in the capital, in the middle of the city, between to the most multitask and busy streets. It is important to be mentioned that the square is placed 9 meters below the certain road, as it is clear on Figure 49.

According to Figure 48, the 74.44% of the operative hours, reach the air velocity of 1.52.5m/s, when the 25.56% of the operative hours reach the air velocity of 2.5-3.5m/s. It is clear that the constant velocity, which will be used on the following simulations to show the performance of the air distribution of the tower device, should be a number from 1.5m/s to 2.5m/s. As the 1.5m/s air velocity is the low boundary it is more useful to use as constant velocity the number of 2.5m/s. Now that the air velocity is predicted on 2.5m/s, the thesis can move on the performance of the air distribution, through the CFD software, of a realistic environment, with buildings, trees and streets. In other words, this is the stage, which through the simulation it will be predictable how far the produced fresh air can distribute.

Figure 49: Syntagma square.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

As it is in the centre of the city, the public transportation is very organized, and all the tube’s lines change on that specific place. Also, based on that square, which is the first square that was built in Athens, the market around it was took place. All the shops, restaurants, bars, offices, companies, grand hotels and anything that it’s related with the economy, are placed around this square. The perimeter of Syntagma square is 445.11 m and its area around to 13,311 m2, which explains in excellent way the reason that this square is the main vital cell of the city. This place is occupied for at least 18-20 hours per day.

The previous analyses gathered all the necessary data to proceed in more details on this project. Until now, it is known the temperature difference, the air velocity of the outlet area, the produced fresh air, the exact amount of persons that covers with fresh air and the needed water to evaporate the tower device. The only missing thing now it’s the air distribution, in other words how far this fresh air can reach. To estimate that, is going to be used the CFD software, which can estimate and at the same time optimize exactly how many meters and with which velocity the fresh air is distributing. One step before the simulation on CFD, is to create a 3D model, in Rhinoceros software, as exact copy of the selected area’s environment. With constant air velocity to 2.5m/s, the next step is to import the 3D model on CFD software. The selected area was separated by two parts according to the ground level (Figure 50).

It is more than understandable that it is major issue to improve the polluted air of this place, which is the most common and frequently visited place for all the citizens of Athens and for all the tourists, especially at the summer season.

Figure 50: Separated parts of CFD simulation.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

To realize and understand more this unique area, it was inevitable to optimize and present some sections from the 3D model. From the following section it is more than noticeable that the Syntagma square is based on different level from the surrounded area. It is really interesting to examine if the fresh air can reach on the area of part 2. In other words, it is crucial to examine if the air can distribute on the part 2, which is 9m above the Syntagma square.

Figure 51: Sections of the first selected area.

500 m

Figure 52: Optimization of air distribution in Syntagma square 1m from the ground level. 56

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

On the first image on Figure 52 is illustrated a plan section 1m above the ground level. According to CFD simulation, the distributed air reaches the range of 500m, which is a really successful result. The air velocity will be up to 0.1-0.3m/s at 1meter from the ground, in a range of 50 to 100meters. The second image on Figure 51 presents the air distribution on the vertical axe. The fresh air reaches the height of 100m from the ground level. On humanâ&#x20AC;&#x2122;s level (up to 2 meters) the air velocity achieves the amount of 0.20.3m/s. So, according to these results, one tower device can produce fresh air for at least 1007 persons per hour, and also can

distribute the fresh air in a range of 500m around the tower. But what is going on with the air distribution of part 2, which is 9m above the square and also above of the installed tower device? It is noticeable even from the section on Figure 51, that the air is distributed more than 100m on the vertical axe. For this project, to be even more precise, it was taken a plan section on the part 2 (Figure49), 1m above the ground level (which means 10m above the Syntagma square).

Figure 53: Optimization of air distribution in Syntagma square 10m from the ground level. 57

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

As it was already predicted, the air distribution is continuing up to this level too. It’s surprising that on the horizontal axe, even 9m higher than the previous plan section, the air occupies again almost 500m around the tower device. The only difference is that the air velocity even up to 10 meters from the ground level (and 1 meter from the ground level above the square) will be around to 0.06 m/s. As a result of that, the air velocity probably won’t be noticeable and effective at that level, but the fresh air will be more than enough.

The second selected area is about a roundabout in Ampelokipoys, about 2km far from Syntagma square. This is one of the most important, multitask and busy roundabout in the capital of Athens. This is the spot that 4 of the most occupied streets of the whole capital connect to each other.

Figure 54: Roundabout in Ampelokipoys, comparing to the whole capital. it’s rush hour, like 9:00-12:00 the morning, 15:00- 18:00 in the middle of the day and 21:00-10:00 in the evening the traffic is unbearable and time consuming.

As it is illustrated in Figure 53, this roundabout is the only main way for all the suburbs and others cities and areas, around the centre, to reach the downtown. It is used for more than 20 different areas from any direction like Tavros, Kallithea, Nea Smyrni, Ilioypoli, Vyronas, Kaisariani, Zografoy, Papagoy, Cholargos, Psychiko, Galatsi, Agioi Anargyroi, Ilion, Peristeri Egaleo and these are only the areas in the range of 2-5km around the centre of the city. So it is expected to get high amounts of pollution basically from every kind of vehicles and means of transport, as the spot measurements showed. And especially when

So, again according to the previous analyses, all the necessary data are gathered to proceed in more details on this project. Based on these, the only missing thing now it’s the air distribution, in other words how far this fresh air can reach. To estimate that, it is necessary to used the CFD software, which can estimate and at the same time optimize exactly how many meters and with which velocity the fresh air is distributing. 58

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

One step before the simulation on CFD, is to create a 3D model, in Rhinoceros software, as exact copy of the selected area’s

environment. With constant air velocity to 2.5m/s, it is needed to import the 3D model on CFD software.

700 m

Figure 55: Optimization of air distribution in roundabout in Ampelokipoys 1m from the ground level. the air velocity achieves the amount of 0.50.7m/s. So, according to these results, one tower device can produce fresh air for at least 1007 persons per hour, and also can distribute the fresh air in a range of 700m around the tower.

The first image on Figure 54 presents a plan section 1m above the ground level. According to CFD simulation, the distributed air reaches the range of more than 700m, which is a really successful result. The air velocity will be up to 0.2-0.4m/s at 1meter from the ground, in a range of 50 to 100meters. The second image on Figure 54 illustrates the air distribution on the vertical axe. The fresh air reaches the height of 100m from the ground level. On human’s level (up to 2 meters)

As the simulations showed, from both selected areas, the tower device can distribute the fresh air 500 to 700 meters around it. Another benefit is the fact that the tower device can produce

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

fresh air for at least 1007 persons per hour, that the air velocity on the ground and humanâ&#x20AC;&#x2122;s level (up to 1 and 2 meters respectively) will be from 0.1-0.4 m/s, which is noticeable but not uncomfortable, especially at winter season. And also another advantage is that the tower device can cause lower temperature, especially at spring and summer seasons, when the temperature difference is higher (Figure 45). All the Phases and their results showed that the tower device can be productive and operative during the whole year under of specific conditions. It can also produce fresh air for more than sufficient number of people (1007 persons per hour) and it can distribute that fresh air in a really long range of distance (up to 500 to 700 meters). In other words, all the previous Phases proved that the tower device can offer a lot benefits to the selected areas and especially to the citizens, in order to improve their health issues, which are caused by the pollution of the atmosphere. So if one tower can offer so many opportunities for improvement in one area, what can more than one towers offer if they cooperate together? How much the distance should be between them, in order to cooperate in harmony? Can the one tower device effects the results or the range of distance distribution of the other one? All these questions, lead to the next and final Phase of this thesis, which is the performance of air distribution on the selected areas with more than one tower devices.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

5.6 Phase V Performance of air distribution of more than one tower on the selected areas At this stage of thesis, the next step is to create a new Rhino 3D model, but this time it is needed to extend the selected areas. To be more specific, to estimate how the air distribution of more than one tower devices on the selected areas, is going to be, the surroundings and in general the context of these areas should be created in the range of a bigger distance. To succeed that, the previous 3D model should be at least double on size, so it will be applicable to add one more tower in the right position and distance from the first one.

Based on the fact that the two selected areas are placed only 2km from each other, there was the thought to combine the two areas to one and add on them two more tower devices. Unfortunately, the CFD software couldn’t run the simulation of such a huge area, so again the simulation is going to be in two parts. Again the first selected area is in Syntagma square.

Figure 56: Updated selected area in Syntagma square. As the Figure 55 shows, now this is how the selected area in Syntagma looks like. And the distance between the two towers will be 500m, as according to Phase IV, this is the distance that the one tower device can cover with fresh air. After the creation of this new area in 3D model in Rhinoceros software, the next step is to import this file with the two tower devices in CFD software.

Again, with constant air velocity to 2.5m/s, the next step is to separate the selected area in two parts according to the ground level (Figure 50). The first part would be a plan section from 1 meter from Syntagma square and the second one 10m from the square. Especially now, it is crucial to present the simulations in two parts, because the second tower device is placed in a different level from the first one. 61

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 57: Optimization of air distribution in Syntagma square 1m from the ground level.

Figure 58: Optimization of air distribution in Syntagma square 10m from the ground level.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

On Figure 56, it is not possible to understand the effects of the second tower device. But it is clear that now the tower device distributes the fresh air even further (more than 600m) .On the second image on Figure 57 is illustrated a plan section 10m above the ground level. According to CFD simulation, the distributed air, from both tower devices, reaches the range of 1.2km to 1.5km, which is a really successful result. It is obvious that the one tower device influence to the other as a result to improve even more the performance of the air distribution. The air velocity will be up to 0.1-0.3m/s in both levels, in a range of 50 to 100meters. The third image on Figure 56 presents the air distribution on the vertical axe. The fresh air reaches the height of 100m from the ground

level. On humanâ&#x20AC;&#x2122;s level (up to 2 meters) the air velocity achieves the amount of 0.20.3m/s. So, according to these results, the two tower devices can produce fresh air for at least 2014 persons per hour, even when the towers produce the lowest amount of fresh air. As the Figure 58 shows, now this is how the second selected area in Ampelokipoys looks like. The distance between the two towers will be 700m, as according to Phase IV, this is the distance that the one tower device can cover with fresh air. After the creation of this new area in 3D model in Rhinoceros software, the next step is to import this file with the two tower devices in CFD software.

Figure 59: Updated selected area in Syntagma square.

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 60: Optimization of air distribution in roundabout in Ampelokipoys 1m from the ground level. To conclude, according to the results of Phase V, the performance of fresh air distribution it appears to be something more than successful. As it was mentioned before, the selected areas it was meant to be tested as one area. Now that it is thorough that each tower collaborates perfectly with another one. It is aftermath to conclude that the results will be the same successful or even more if a third or more tower devices will be added. That means that this route, of 2km distance, which starts from the Syntagma square and ends in Ampelokipoys will get four tower devices. According to that, the towers on this route, which is the most polluted route in the whole city, will produce fresh air for at least 4028 persons per hour on the worst performance of the production of fresh air.

The first image on the right on Figure 59 presents a plan section 1m above the ground level. According to CFD simulation, the distributed air, now that two tower devices are activate, reaches the range of more than 1.2km to 1.5km, which is a really successful result. The air velocity will be up to 0.20.4m/s at 1meter from the ground, in a range of 50 to 100meters, around to each tower. The sections of the image on Figure 59 illustrate the air distribution on the vertical axe. The fresh air reaches the height of 100m from the ground level. On humanâ&#x20AC;&#x2122;s level (up to 2 meters) the air velocity achieves the amount of 0.5-0.7m/s. So, according to these results, the two tower devices react to each other by causing incredible results. Also, the both activated tower devices can now produce fresh air for at least 2014 persons per hour, on the worst performance of the production of fresh air. 64

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

Figure 61: Optimization of air distribution in both selected areas with four activated towers devices. As the Figure 60 illustrates, the effect of whole towers is more than noticeable. The fresh air is distributed around of the whole area and all the tower devices together cover the range of 2.4-3.0km.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

device for Athens it’s the one with height 25m, inlet area (on the top of the tower) as 100m2 and outlet area (on the bottom of the tower) as 30.20m2. This tower device should be activated only the hours of the year that it’s beneficial. To achieve this, the device should be open when the temperature difference (ΔT) is more or equal to 2.24oC, which means that the air velocity should be equal or more than 1.5m/s. Also according to this and to the annual weather data, it is known, that the outlet air velocity (on the bottom of the tower) will be from 1.5 to 3.5m/s. This amount of air velocity is acceptable and comfortable for the citizens. Another condition is that the hours of the whole year that the tower device can’t evaporate the area should be removed from the operative ones. To sum up the tower device will be activated for 4212 hours during the whole year. It can provide fresh air for at least 1007 persons at the worst hour of performance and the maximum water consumption per hour is 266.68l when a European citizen needs per day 150-250l. Furthermore, the tower device can distribute the fresh air in a range of at least 500-700m on the selected areas, with air velocity at 0.10.3m/s. Also, one tower device can collaborate with another one perfectly by doubling the benefits. The influences of this collaborative team is more than noticeable, as the two towers can distribute the fresh air in a range of 1.2 to 1.5km, and provide fresh air on the worst hour of performance for at least 2014 persons, by reaching the same air velocity, 0.1-0.3m/s.

6. Conclusions Through the literature review, the part of the fieldwork and the part of the main case study project, this thesis basically focuses on the procedure of the evaporative cooling in Athens via towers. And also, the thesis project examines this procedure from the beginning until the end and presents all the benefits that result. From every main part of this thesis project concludes some really interesting and beneficial results. Literature review: Based on the research of that part of the thesis, it’s concluded two main points. The first one is that the air pollution can cause extremely dangerous consequences on the human’s health. And the second one is that the evaporative cooling via tower devices it’s a system totally understandable, through the equations, maths and physics, feasible and effective. Fieldwork: The fieldwork, on both selected areas, proved that in Athens the level of air pollution not only exists but they are high too. Especially, the pollutants like VOC (Volatile Organic Compounds), NO2 (Nitrogen Dioxide), CO (Carbon Monoxide), O3 (Trioxide), SO2 (Sulfur Dioxide) PM2.5 and PM10 (Particulate Matters) and CO2 (Carbon Dioxide), which are the ones that they’ve been measured, constitute the most dangerous pollutants for human’s health. This part is the proof that Athens needs any kind of help to improve this situation.

It is important to be mentioned again, that this project examines the tower devices and their performance by using evaporative cooling. All the results of this thesis are based on yearly weather data, mathematics, physics and equations that prove the benefits of this project. Regardless, the material of the tower device, the results would be the same. Even if

Case study project: The solution to all these is going to give this unique project. According to all the formulas and physics, the best version on a tower 66

Thesis Project: â&#x20AC;&#x2DC;Clean air through evaporation in Athens, Greeceâ&#x20AC;&#x2122;

the positions of the tower devices on the selected areas were chose really carefully maybe this structure will change the culture of Athens. The spots are located in areas with huge spaces, like squares, really close to parks and the reason behind this was that these towers can be used like the new cells of the city. Based on them, underneath them it could be placed a market, or a music festival or a playground for children. They can be used as the link that can join all the people together again. It is really usual to use these towers for the benefit of each town. So, it is time for Greece and especially Athens to do the same thing. These towers can be the start for a new type of life, greater, healthier and improved. As it is obvious, there are many things on this project that needs farther investigation. Such as the material of the tower, or technological systems which can use sea water as main source, or high tech systems that can improve the image of the tower. For example, it can create a reflection of the environment, or it can change colors by the temperature, or the amount of fresh air. One domain that for sure needs farther investigation is the social part. It is really important to be created some questionnaires for the citizen. Are they willing to accept something like that? Do they believe that a structure like this could change the Greek culture? And many other questions that need to be answered before this project is implemented.

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

and PM2.5 Levels in Indoor and Outdoor Environments of Four European Cities. Environ Sci Technol 36(6):1191-197, 2002. 9) Chaloulakou A, Kassomenos P, Spyrellis N, Demokritou P, Koutrakis P. Measurements of PM10 and PM2.5 particle concentrations in Athens, Greece, Atmospherc Environ 37(5):649-660, 2003. 10) Thomaidis NS, Bakeas EB, Siskos PA. Characterization of lead, cadmium, arsenic and nickel in PM2.5 particles in the Athens atmosphere, Greece. Chemosphere 52(6):959-966, 2003. 11) Manalis N, Grivas G, Protonotarios V, Moutsatsou A, Samara C, Chaloulakou A.Toxic metal content of particulate matter (PM10), within the Greater Area of Athens. Chemosphere 60: 557�566, 2005 12) Valavanidis A, Fiotakis K, Vlachogianni Th, Bakeas EB,Triantafillaki S, Paraskevopoulou V, Dassenakis M. Characterization of atmospheric particulates, particle-bound transition metals and polycyclic aromatic hydrocarbons of urban air in the centre of Athens (Greece). Chemosphere 65(5):760768, 2006. 13) Katsouyanni, K; Touloumi G.; Samoli E., Gryparis A.; Le Tertre, A., et al. , Confounding and Effect Modification in the Short-Term Effects of Ambient Particles on Total Mortality: Results from 29 European Cities within the APHEA2 Project. Epidemiology 12(5): 521-531, 2001. 14) Samoli E, Kougea E, Kassomenos P, Analitis A, Katsouyanni K. Does the presence of desert dust modify the effect of PM10 on mortality in Athens, Greece? Sci Total Environ. 409(11):2049-2054, 2011. 15) Analitis A, Georgiadis I, Katsouyanni K. Forest fires are associated with elevated mortality in a dense urban setting. Occup Environ Med. 69(3): 158-162, 2012. 16) Kassomenos PA, Dimitriou K, Paschalidou AK. Human health damage caused by particulate matter PM10 and ozone in urban environments: the case of Athens, Greece. Environ Monit Assess.185 (8):6933-6942, 2013. 17) Liakakou E, Gerasopoulos E, Theodosi C, Mihalopoulos N. Long-term characterization of organic and elemental carbon in the PM2.5fraction: the case of Athens, Greece.

7. References 1) Valavanidis A, Vlachogianni Th. The most important and urgent environmental problems in Greece in the last decade (20002010). Website: Department of Chemistry, Univ. Athens www.chem.uoa.gr and research gate, Valavanidis Athanasios (18.3.2011) http://www.chem.uoa.gr/scinews/Reports/R ep_Env_problems2000-10.htm 2) OECD. 2000. OECD Environmental Performance Reviews: Greece.2000. OECD publications, Paris, ISBN: 9789264181137(PDF), 9789264171893(print), http://www.oecd.org/dataoecd/9/1/244863 2.pdf 3) European Environment Agency (EEA), Air pollution in Athens: existing status and abatement practises (Dec 2008). http://www.eea.europa.eu/publications/259 9XXX/page018.html 4) Valavanidis A, Vlachogianni Th. Environmental Crisis in Greece. The Consequences of Modernity and Economic Growth without Sustainability Goals. A Review of the Main Problems Related to Pollution, Environmental Protection and Management of Natural Resources in Greece. 24.9.2012. Website: www-chem-toxecotox.org http://chem-toxecotox.org/wp/?p=776- . 5) Valavanidis A, Loridas S, Vlachogianni Th, Fiotakis K. Influence of ozone on trafficrelated particulate matter on the generation of hydroxyl radicals through a heterogeneous effect. J Hazard Mater 162(2): 886-892, 2009. 6) Valavanidis A, Vlachogianni Th, Fiotakis K, Loridas S. Pulmonary oxidative stress, inflammation and cancer: respirable particulate matter, fibrous dust and ozone as major causes of lung carcinogenesis through reactive oxygen species mechanisms. Int J Environ Res Public Health 10:3886-3907, 2013. 7) Scheff PA, Valiozis C. Characterization and source identification of respirable particulate matter in Athens, Greece. Atmospher Environ, part A, General Topics. 24(1):203211, 1990. 8) Gotschi T, Oglesby L, Mathys P, Monn C, Manalis N, et al. Comparison of black smoke 68

Thesis Project: ‘Clean air through evaporation in Athens, Greece’

Atmosphere Chem Phys 14:13313-13325, 2014. 39. 18) ASHRAE (2013). ‘ASHRAE Handbook: Fundamentals 2013’. American Society of Heating, Refrigerating and Air-Conditioning Engineers. 18) CIBSE (2015). ‘Guide A: Environmental Design’. London: Chartered Institution of Building Services Engineers. 19) Cunningham, W. A. & Thompson, T. L. (1986). ‘Passive Cooling with Natural Draught Cooling Towers in Combination with Solar Chimneys’. Proc. 3rd PLEA International Conference. Pets, Hungary, The Hungarian Society of Sciences. 20) Ford, B. & Hewitt, M. (1998). ‘Cooling without Air Conditioning: The Torrent Research Centre, Ahmedabad, India’. Renewable Energy 15, 1-4: pp. 177-182. 21) Simplified Models for Assessing Heat and Mass Transfer in Evaporative Towers Alessandra De Angelis, Onorio Saro, Giulio Lorenzini, Stefano D’Elia, and Marco Medici 2013 22) Ford B., R. Schiano-Phan, E. Francis (ed. 2010), The Architecture and Engineering of Downdraught Cooling, A Design Source Book, PHDC Press, ISBN 978-0-9565790-0-3 23) https://climate.nasa.gov/evidence/ 24) https://www3.epa.gov/ttn/atw/hlthef/hapin dex.html 25) https://www.ipcc.ch/ 26) http://www.cres.gr/cres/index.html 27) http://www.desmie.gr/ 28) http://www.meteo.gr/Gmap.cfm 29) http://www.ypeka.gr/Default.aspx?tabid=48 9&language=el-GR 30) https://www.timeanddate.com/weather/gre ece/athens/climate 31) http://hanschen.org/koppen/ 32)https://www.weatheronline.gr/weather/ maps/city?FMM=1&FYY=2018&LYY=2019&W MO=16716&CONT=grgr&REGION=0005&LAN D=eusud&ART=PRD&R=160&NOREGION=1& LEVEL=162&LANG=gr&MOD=MOA 69