airport ac feasability study final - 29 aug 2011 v1.3

8/4/2019 Airport AC Feasability Study FINAL - 29 Aug 2011 v1.3

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Feasibility StudyFor Cape Town International Airport

Consultants:

Munya Matose

MTSMUN003Luke Cox CXXLUK002Margret Hansen HNSMAR009Tumelo Gabaraane GBRTUM001Sachin Chetty CHTSAC001Ruben Aldum ALDRUB001

Previn Subban

SBBPRE001


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Table of Content

1. Executive Summary

2. Problem and Requirement Statement3. General Assumptions3.1Cape Town Weather3.2Population Distribution3.3Physical layout4. Feasibility Assessment4.1Option 1Evaporation Water Cooling System4.1.1 Description4.1.2 Assessment & Issues4.1.3 Assumptions4.2Option 2Ground Source Heat Pump

4.2.1 Description4.2.2 Assessment & Issues4.2.3 Assumptions4.3Option 3Vapour-Compression Air-Conditioning Units4.3.1 Description4.3.2 Assessment & Issues4.3.3 Assumptions4.4Option 4Solar & Wind Assisted Absorptive Chilling Heat Pump System4.4.1 Description4.4.2 Assessment & Issues4.4.3 Assumptions

5. Feasibility Ranking5.1Ranking Criteria5.2Ranking Scores6. Feasibility Results7. References8. Bibliography9. Plagiarism Declaration


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1. Executive SummaryThe purpose of this study is to ascertain the best method of heating, ventilation and air

conditioning (HVAC) for the new departure hall at Cape Town International Airport.

A list of requirements was used as the terms of reference when investigating eachproposal.

A total of four proposals were made, each outlining a combination of different

methods to satisfy the requirements. The salient points of each method were:

Option 1 uses an evaporative water cooling system powered by Eskom electricity,roof-top extractors, LED lighting, sensors in rotating doors and Polyisocyanurate

insulation.

Option 2 uses a ground source heat pump running on the Eskom power grid,fluorescent lighting and sensors in rotating doors and Vermiculite and Perlite

insulation.

Option 3 uses vapour-compression air conditioning units running on Eskomspower grid, ducting for air distribution, additional power generated by

piezoelectric flooring, high intensity discharge lights and Polyisocyanurate

insulation.

Option 4 uses an absorptive heat pump chilling system running on solar and windenergy as well as the Eskom power grid, narrow duct outlets for distribution and

cellular glass insulation.

Each of the four proposals outlines a description, assessment and issues and

assumptions.

The proposals were then ranked on the basis of: Power Usage; Water Usage;

Temperature and Humidity Control; Installation and Maintenance Costs; Space

Requirements; Pollution and Noise Generation; Risk of Vandalism; Aesthetics

Once this was complete it was found that option 4 was ranked the highest as it best

met the requirements and was thus the proposal put forth as the official

recommendation.

2. Problem Statement and Requirements[1]Cape Town International Airport must expand in the future if the airport is to

accommodate the Airbus A380. A feasibility study is required of the airportexpansion, in terms of the performance parameters for the air conditioning and

circulation units in the departure hall.

Four different proposals are required for the feasibility study.

The temperature must be maintained at 23C with 60% relative humidity.

The departure hall will host about 500 passengers at peak times (not including staff

and other employees) at any given time.

The hall must be spacious so that people will not feel too confined.

The footprint of the departure hall is known and fixed.

The airport aims to be recognized as a green airport which means that energy and

water consumption are to be at a minimum.


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3. General Assumptions3.1Cape Town Weather

Temperature ranges from about 6C during winter nights to approximately 35C

during summer days.[2]

Summer is more windy than winter.

Water is scarcer during summer than winter.

Humidity ranges from about 55% to about 92% [3]

3.2Population Distribution

For passengers we assume world averages[4]

26% for under 14 year olds

66% for 15 to 64 year olds

8% for 65 year olds and above

3.3Physical Layout

The entrance to the hall will be located on the north side of the departure hall. The

restaurants and lounging area will be located along the East wall and the duty free

stores (for example curios& gift stores) along the west wall. The gates will then be

along the South wall: facing the aircrafts. This will provide a big general roaming area

in the centre of the hall so that people can move from one section to the other with

ease. No windows will be placed on the North wall. This is done in order to decrease

the amount of direct sunlight in the departure hall which in turn will reduce solar

heating. Large windows will be placed along the eastern wall to provide sunlight in

mornings and to serve as a lookout area.

Figure 1. Terminal Layout


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4. Feasibility Assessment4.1Option 1Evaporation Water Cooling System

4.1.1 Description

This system will focus on being eco friendly and only relying on Eskom power wherealternatives are not found. The core of the system revolves around an evaporating

water system which functions differently to refrigerant cooling in that, instead of

compressing and expanding some coolant liquid, which is usually hazardous,

evaporative coolers make use of the fact that warm air may be cooled as it becomes

moister. By drawing in hot and dry air and passing it through a damp layer, the

evaporative cooler simultaneously cools and moistens the air it ultimately sends to the

room that requires cooling.

The air-conditioning will also feature extractor fans on the roof of the hall to remove

hot air from inside the hall. The extractor fans will rely on centrifugal force from the

hot air rising to power them and hence is independent of electricity.

LED lights will be used inside the hall as an artificial lighting source. This will

provide light at a more cost effective level and are safer than fluorescent light bulbs

should they break as they contain no hazardous substances. This also means that they

are easier to dispose of.

Sensors in the rotating door will be used to count the number of people entering and

leaving the hall. This will also provide added security by only allowing a certain

number of people in or out at a time and also limiting the speed at which they enter

and exit.

Polyisocyanurate Insulation will be used to insulate the hall in combination with UV

protected glass to reduce external solar heating.

4.1.2 Assessment & Issues

The downside for an evaporation system is that it needs a continuous supply of water

to moisten the incoming air, and that it is not as effective in already humid

environments.

Because it uses only water, there are no hazardous refrigerants but the high moisture

content of the air may result in dangerous mould growth. The temperature control of

this type of system is also not accurate.

The extractor fans continuously remove hot air and this could increase heating

requirements during winter months.

The LED lighting provides a good alternative due to very low heat generation, but

because they do not completely provide light in the green frequency range, the colour

quality of light is not ideal.

Another problem is that the evaporation system increases humidity yet in Cape Town

humidity is already in the range of 55% - 92%.


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Polyisocyanurate insulation has very high insulating properties for relatively low

thickness. The R-value (resistance to thermal transfer) of the insulation decreases as

the HCFC escapes and air replaces it and hence would need maintenance. HCFC

could also provide to be a health risk.

4.1.3 Assumptions

Efficiency of the system is taken to be ideal with no external losses or loss due to

wear and deterioration.

4.2Option 2Ground Source Heat Pump

4.2.1 DescriptionA ground source heat pump uses the earth (which has a more constant temperature

than the air) as a source to either absorb heat from or reject heat to. The temperatureof the earth is cooler than the ambient temperature during summer and warmer than

the ambient temperature during winter which makes it an ideal medium for a heat

exchanger.

Water (or refrigerant, or water with antifreeze) is circulated through a series of pipes

that are buried underground. The length of the pipe is determined by the temperature

of the ground, thermal conductivity of the ground, moisture content and system

design.

These pipelines need to follow the International Ground Source Heat Pump

Association prescriptions.

Vertical loops are used when the space requirement are a problem such as in the

airport, here holes are drilled 6090m deep.

Because a heat pump is a device that is used to transport heat instead of creating heat

it can have a very high efficiency (higher than 100%).

Vermiculite and Perlite Insulation will be used.

A rotating door sensor identical to that in option1 is used.Fluorescent tubes are used as they provide cheap and efficient low-power lighting.

The system will be powered by the municipal power grid.

4.2.2 Assessment & IssuesThe insulation contains asbestos but this compound is not intrinsic to vermiculite. It is

essential to consult an insulation contractor trained and certified in handling asbestos

due to health risks. Its free flowing properties make installation very simple,

especially for retrofitting.


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Ground source heat pumps have very high initial costs and installation is very

complex but the system has very low maintenance costs and is also very efficient (400

500%)

Ground source heat pumps are good for climates that require both heating and

cooling.

The fact that water is used to transport heat means that the system is compact and uses

up much less space than air ducts. It also eliminates the need for roof top units,

chimney towers etc., which reduces the chance for vandalism.

Rain water or grey water can be used to replenish water that is lost in the system or is

no longer usable.

Ground source heat is considered a renewable energy source therefore this is

considered to be a green option.

There are few moving parts which means it needs little maintenance and it can beretrofitted to a building quite easily. It is a quiet system because it has few moving

parts.

It works best in buildings that have large floors for surface area.

A disadvantage of the system is that polluted surface water washed down and can mix

with deep unpolluted ground water. Additives can be added to the water to increase its

heat capacity but this also increases the systems potential for pollution. A

disadvantage is that the system becomes less efficient as the difference in outside

temperature and the desired temperature becomes too great.

4.2.3 AssumptionsIt is assumed that suitable highly trained technicians can be readily found to install the

system otherwise the repair costs become very expensive.

4.3Option 3Vapour-Compression Air-Conditioning Units

4.3.1 DescriptionNormal vapour-compression air conditioning units (which are the most widely used

method for air-conditioning of large public buildings)

Simple air ducts will be used for the different sections of the airport terminal. The

restaurant, lounge, shopping and the check-in sections will contain air ducts with

thermal sensors. These areas will have varying numbers of people at certain times sosensing the temperature is essential.

The free-roaming area will have fewer air ducts, without sensors, to maintain a fixed

temperature.

Piezoelectric flooring will be used for sensing the amount of people in the terminal.

This is a technology with a wide range of applications that is slowly being adopted in

the race to develop alternative energy sources. Piezoelectric flooring will be using

stone tiles for improved energy generation.


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Polyisocyanurate Insulation (Polyiso) is a closed cell foam insulation containing a low

conductivity gas. This gas is made up of hydro chlorofluorocarbons (HCFC) which

has very good insulation properties. This insulation can be either sprayed foam or

rigid foam board. However, the sprayed foam method has been proven to work betterthan foam board since the liquid moulds itself into all surfaces and corners.

High-intensity discharge lights are normally used for outdoor lighting but it will be

used for the terminal due to its high efficiency.

4.3.2 Assessment & IssuesHaving temperature regulation in sections of the terminal will ensure that only

sections that require a temperature change will receive hot or cool air. This is efficient

as it conserves power. However, this method takes up an excessive amount of space.

The piezoelectric flooring system will harvest the kinetic energy generated by crowds

and could power ticket gates and display systems. Another advantage is that it is a

renewable energy source. This method will, however, not provide enough power for

the whole terminal. Therefore Eskom will be the primary power provider.

The Polyiso insulation assessment and issues are the same as in option 1.

The high intensity discharge lights would be useful in that they offer high efficiency

and long life (5000 hours24 000 hours).[5]

This would be equivalent to between half

a year and two and three quarter years if the lighting runs continually. Unfortunately,

this type of lighting contains mercury, which is an environmental hazard.Furthermore, it incurs high initial and replacement costs.

4.3.3 AssumptionsEfficient control systems are used for temperature regulation (air conditioning) that

responds promptly to changing temperatures and humidity.

4.4Option 4Solar & Wind Assisted Absorptive Chilling Heat Pump System

4.4.1 DescriptionThis method combines solar and wind energy into a single power generation scheme

which would be very beneficial, as a total of 8% on electricity usage can be saved.[6]

The technology available to combine wind and solar has been specifically designed to

power high voltage air conditioning units. These systems can also be adapted to

supply other areas which need electricity, such as the terminal lighting, inside and

outside, the communications tower and other shops /restaurants within the terminal.

The system is easily integrated into our local grid supply and will only make use of it

(Eskom) when wind or solar energy cannot be supplied. Solar and wind energy is

most efficiently collected in the warmer months of the year. The energy collected

supplements energy used in air cooling in the summer so that usage of mains

electricity is significantly reduced.


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For absorptive chilling/cooling, the heat from sunlight is used to drive the main

cooling process. A water based refrigerant (ammonia or lithium-bromide)[7]

with a

low boiling point is driven from a solution by the addition of heat in a generator,

resulting in evaporative cooling; the heat is sourced from a solar collector, through

which the refrigerant solution is pumped.

Water pumped adjacent to the evaporating refrigerant is chilled and pumped through

cooling coils.[8]

Warm air extracted from the airport departure hall (restaurants, gate

areas, shops and lounges included) is cooled directly by the cooling coils and pumped

back through the ducts.

For heating, a heat pump system is used. This is a system where cold air from the

departure hall/outside is heated through the vapour-compression refrigeration cycle

operated in reverse. Solar and wind energies augment the heat pump system which is

driven by Eskom. Here, heated water/solution is pumped to the heating coils that heatthe cold air.

To counter reduced humidity caused by cooling warm dry air in summer, spray jets

are used to humidify the conditioned air accordingly. Grey water (recycled water from

rain and bathroom water) is used in the refrigerant-solutions.

This option uses an extensive air duct system. Duct-outlet distribution points will be

placed throughout the hall with a greater number placed in the areas where heat build-

up is expected. These include restaurants, shops, lounges and departure gates where

ideal conditions are necessary. Here the staff is able to alter the temperature of the

rooms through local thermostats that directly control the heating and cooling coilsassociated with their specific air ducts.

Cellular glass insulation is used in the air duct systems. This insulation had been used

for chilled water applications in airports successfully in the past. It is 100% glass, a

non-combustible material; it will not absorb moisture in either liquid or vapour form.

This means that it is impermeable to water. This is an essential property given Cape

Towns wet climate.

4.4.2 Assessment & IssuesIn the winter months, which are less windy and sunny, solar energy cannot be

depended on and wind energy will only be utilised occasionally. This means that forcertain months during the year, the solar panels, heat collectors and the wind turbines

will be ineffective.

Extensive air duct systems are known to create a significant amount of noise,

especially in this case where minimal-diameter-duct tubes are used. The noise

generated from high velocity air is noticeable if not dealt with (noise dampers).

Cellular glass insulation manufactured only from crushed glass and carbon, is free

from fibres, CFC and HCFC thus it is environmentally sound. With its constant and

long-term energy efficiency, cellular glass insulation provides low, predictable energy

costs.


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Temperature and humidity sensing on such a large scale is seldom efficient and will

need expensive systems to operate with desired accuracy.

Installations of this option incur high initial costs, but these costs will eventually pay

for themselves due to the use of renewable energy.

4.4.3 AssumptionsIn order for this air conditioning system to be feasible, skilled technicians are required

to run and maintain the system. Alternatively a complex, but reliable automatic

controller can be used to run the system.

Efficient control systems are used for temperature regulation that responds speedily to

changing temperatures and humidity.

Reliable sensors are used to detect the important parameters (temperature and

humidity, number of people).

5. Feasibility Ranking

5.1Ranking CriteriaThe following requirements were used to rank the four options

Power usage (25) must be low to reduce the running costs and make the productenvironmentally friendly.

Water usage (15) must be low to reduce the running costs and make the productmore environmentally friendly.

Temperature control (30) is important so that the product meets the problemrequirements.

Humidity control (25) is important so that the product meets the problemrequirements.

Installation costs (10) need to be kept to a minimum unless running andmaintenance costs are so low as to justify a higher installation cost.

Maintenance costs (15) need to be kept to a minimum.

Space requirements (10) for the storage of the required machinery as well as theducts in the terminals.

Pollution generation (10) from running the system and the severity of their effects.

Noise generated (5) both in and outside the terminal.

Risk of vandalism (5) how easy is it for people to damage the machinery and

severity of its effect. Aesthetics (5) how pleasing is it to look at the system from both inside and outside

the building.


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5.2Ranking Scores

Criteria

Options

Option 1 Option 2 Option 3 Option 4

Power (25) 15 20 15 22

Water usage (15) 0 12 15 12

Temperature control (30) 10 16 30 30

Humidity control (25) 8 5 5 20

Installation cost (10) 8 0 0 0

Maintenance costs (15) 5 12 7 7

Space requirements (10) 7 7 4 5

Pollution generated (10) 1 6 2 9

Noise generated (5) 5 5 2 1

Risk of vandalism (5) 3 5 3 1

Aesthetics (5) 3 5 2 2Total (150) 65 93 87 109

6. Feasibility ResultsFrom the ranking table above, option 4 has been chosen as the best of the options

studied as it meets the requirements in the problem statement. It is sufficiently green

because it generates power from renewable sources and has the desired temperature

and humidity control. The air ducts are very well insulated and the lighting is both

efficient and of good quality.

Its disadvantages are that its aesthetics are not pleasing due to the presence of solarpanels on site and wind farm. The noise generated by high velocity air moving in the

narrow ducts is a form of pollution, but this will be relatively low compared to other

noise factors (airplanes, people talking).

7. References[1]From assignment page

[2]www.wunderground.com

[3]www.meoweather.com

[4]https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html

[5]http://fulltext.ausport.gov.au/fulltext/1998/wa/fo_outdoor_lighting.pdf - Page4

[6]http://www.solarserver.com/[7] Jan F,Kreider and Frank Kreith; Solar Heating and Cooling Engineering

Practical Designs and Economics pg161

[8]McQuiston, Parker, Spitler; Heating, Ventilatiing and Air Conditioning 6th

Edition Analysis and Design Fig 2-1, pg 23

8. Bibliography http://www.brighthub.com/engineering/mechanical/articles/

http://www.energysavers.gov

http://www.soundgt.com/earth.htm www.retscreen.net/download.php/ang/479/0/Textbook_GSHP.pd


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9. Plagiarism Declaration

We hereby declare that:

1) This project is our own work.2) We did not copy or duplicate any part of this project from any other person or

source.

3) All citations are included as needed.

Group Signatures: Date: 29 August 2011

Munya Matose MTSMUN003 ___________________

Luke Cox CXXLUK002 ___________________

Margret Hansen HNSMAR009 ___________________

Tumelo Gabaraane GBRTUM001 ___________________

Sachin Chetty CHTSAC001 ___________________

Ruben Aldum ALDRUB001 ___________________

Previn Subban SBBPRE001 ___________________

airport ac feasability study final - 29 aug 2011 v1.3

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