DEPARTMENT OF TECHNOLOGY AND BUILT ENVIRONMENT

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DEPARTMENT OF TECHNOLOGY AND BUILT ENVIRONMENT

TITLE:

The Study and Practical Application of Sustainable and Energy Efficient Design and Technology for HVAC and Centralised Solar Hot Water Systems in the Al Zeina Development, Abu Dhabi, United Arab Emirates

By: Farshid Salehi

September 2012

Master’s Thesis in Energy Systems

Master Programme in Energy Systems Examiner: Taghi Karimipanah

Supervisor: Ulf Larsson

Opponent: Saeed Heravi

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ABSTRACT

The Al Raha Beach Development entail a major new city situated at Al Raha Beach on the outskirts of Abu Dhabi- United Arab Emirates. The Development is currently in the early stages of construction and will involve the creation of a new landmass to accommodate the development of several precincts along a canal frontage with an integrated mix of uses including residential, commercial, retail, tourism, recreation and public spaces.

The aim is to create a land area for hotels, resorts, shopping arcades, waterside promenades, apartments and offices to ultimately develop a new waterfront city. This 11km long complex has an area of 6,800,000m2, a total built up area of 12,000,000m2 and comprises 9 subdevelopments, including the highly prestigious Al Zeina development.

The Al Zeina precinct is considered as ‘the strategic gateway to Al Raha’ and was constructed at a cost of $510M in 127,190 m2of land. It provides 1,200 premium Apartments, Townhouses and Villas facing the golden beaches of Abu Dhabi. A large range of facilities within the development, such as swimming pools, private gardens, retail facilities, gymnasiums and libraries are also provided for residents.

Pell Frischmann was appointed to provide a full multidisciplinary design service including:

architecture, structural engineering, geotechnical and M&E engineering design, fire, vertical transportation, traffic and transportation, construction supervision and the authority approvals.

The developer, a joint venture between ALDAR and Laing O’Rourke, appointed Pell Frischmann to design the entire complex based on a previous concept. At the time Pell Frischmann was commissioned, there were no standards or regulations relating to sustainability in place in the UAE.

As a consequence, the developer, in recognition of global concerns, specified that it needed to achieve a minimum Leadership in Environmental and Energy Design (LEED) “Silver” rating. Achieving this rating would require design and construction techniques that were very different to the traditional methods of constructing buildings in the UAE.

The Al Zeina scheme was procured as a fast-track project with a demanding programme. This was to ensure the scheme would tie in with ALDAR’s Yas Island leisure development. The short programme that was specified meant that design and construction had to go hand-in-hand.

The strict program, the client’s sustainable aspirations, and the lack of standard regulations in the UAE led to the key challenges on this project – where the conflicting requirements of our client and the authorities led to considerable design changes.

Pell Frischmann acted as arbiter during these discussions to achieve a solution that pleased both the client and the authorities. However, further challenges occurred with the collapse of the global economy, where Abu Dhabi was particularly badly affected, and how we worked with our client through these new and unforeseen pressures.

From April 2008 to present, I have been working for Pell Frischmann Consultants, as a senior Mechanical Engineer in building services. Pell Frischmann is a UK based consultant with major

operations throughout Europe, the Middle East and Asia.

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The Al Raha Site is located on a strip of land situated between the sea and the main highway leading into Abu Dhabi from Dubai. The site is on the fringe of the urban area and approximately 16 km south east of central Abu Dhabi. On the opposite side of the highway to the development is the newly developed Khalifa Residential Area. Figure 1 and 2 provide master plan and a general overview of the Development Area and the Al Zeina Precinct.

Figure 1

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Figure 2 Al Zeina – Al Raha Beach- Abu Dhabi

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1.2 AL ZEINA PROJECT STATISTICS AND LAND-USE

• Seven precincts accommodating 1,200 Premium Apartments, Townhouses and Villas

• Each building has its own recreation amenities such as outdoor swimming pools, gymnasiums and childcare

• 2,800 Underground Car Parking Spaces

• 500m of Beachfront

• Sustainable Transport: LRT, Water Taxis (via canal network).Mi

• Retail High Street with local supermarket and daily needs shops;

• Waterside restaurants and cafes;

Figure 3-Al Zeina site wide plan

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Figure 4-Al Zeina- Precinct A toE

Figure 5- Al Zeina- Precinct C to F

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Figure 6

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Figure 7- Precinct A- 3D Model

Figure 8-Precinct B- 3D Model

Figure 9-Precinct C- 3D Model

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Figure 10-Precinct D- 3D Model

Figure 11-Precinct E- 3D Model

Figure 12-Precinct F- 3D Model

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1.3 CONCEPT DESIGN

Al Zeina promotes traditional passive cooling strategies such as tree covered courtyards, shading devices such as pergolas, colonnades and decorative screens. All apartments have balcony spaces that may be open or screened, sky villas and townhouses have private terraces and pool enclosures, whilst the podium, garden, and beach villas have their own private courtyards, swimming pools and reflection pools.

1.4 ADJACENT LAND USE

The Al Zeina Precinct is located at the eastern end of the Airport Channel, on the former Ladies Beach Site. On the far side of the channel lies Yas Island. The southern tip of this island is currently being dredged for the Al Raha Beach Development. The remainder of the Island is being developed by ALDAR as a leisure destination, with mixed-use tourist attractions including beaches,

entertainment, shopping, hotels, residences, golfing, equestrian facilities and motor racing. Yas Island also hosts the world's first 'Ferrari World’. A highway and bridge crossing to access Yas Island is proposed close to the eastern boundary of the Al Zeina Precinct.

To the east of the Al Zeina Site is a small access road and an extensive area of plantation believed to be associated with Al Raha Palace. The Palace itself is situated approximately 1km to the northeast of the site and appears to be largely unused. The site is bounded to the south by the access road for the Al Raha Beach Development, a strip of rough ground and the main Abu Dhabi-Dubai Highway.

Abu Dhabi Airport is situated approximately 1.2 km to the southeast of the Al Zeina Precinct. This international airport is currently undergoing a phased expansion programme.

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2 Sustainable Design at Al Zeina

2.1 Overview

It is a requirement of the project briefing document that each site is to incorporate sustainable technologies within their design in order to reduce energy consumption in line with global measures to reduce carbon dioxide emissions.

As a measure of applying appropriate sustainable measures it was a requirement that Al Zeina could achieve a minimum silver rating under the Leadership in Environmental and Energy Design (LEED) system. The aim was to deliver a showcase development and example of best practice in Abu Dhabi which would set the standards for future development in the city.

There is usually a cost implication associated with sustainable technology and this needs to be recognized at the onset of any project by both the Client and the Contractor. However, through careful design and selection of equipment, payback periods can be reduced and the systems then provide financial as well as environmental benefits.

2.2 Design Approach

During the concept stage various ways were considered in which the building fabric and the building services could be designed to minimize energy and water use and still provide a comfortable environment for the user.

The following key principles were considered essential in order to achieve an energy efficient design and meet the requirements of the project brief:

 reduce energy demand and use effective energy management systems

 Centralized hot water generation

 reduce water demand

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2.2.1 Reduce Energy Demand

The key challenge in delivering a highly sustainable development in Abu Dhabi is the arid climate of the region which has previously reached to temperatures of 48°C. Therefore, reducing the cooling load within Al Zeina was paramount and it was vital that the buildings’ mechanical cooling systems were efficient and integrated within the structure.

Computer modeling was undertaken to obtain an accurate assessment of cooling loads under dynamic conditions. The original façade proposed by the contractor was a very light weight construction, and whilst the U-value was within accepted limits, the thermal mass very light and consequently the time taken for heat transfer from outside to inside (decrement factor) was very low.

The façade was discussed to be revised to provide a high thermal mass structure having a high decrement factor together with shading to offset solar heat gains. Fabric U-values were further modified to reduce the heat gain from 180w/m²calculated using the original proposed façade to between 80 and 110 w/m² depending on location within the building.

As part of the passive design daylight factors were also looked with the contractor to modify the ratio of glazing to structure of the building envelope to provide the optimum balance between heat gain and natural daylight.

It is essential that the building envelope is well constructed to eliminate thermal bridging and to minimize air permeability. This was discussed in some detail with the design team and practical solutions developed.

By introducing Enthalpy wheel, energy would be recovered from the extract air of the toilets/ kitchens and put into the fresh air stream at the rooftop Fresh Air AHU’s.

As part of good engineering practice and design strategy, additional ways were considered in which energy demand could be reduced using available technologies such as:

 Variable speed drives for fan and pump motors

 Low energy lighting

 High efficiency equipment

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2.2.2 Hot Water Generation

Hot water accounts for approximately one quarter of the average households’ energy, with

conventional electric systems leading to circa 7T/year of CO2 emissions per residence. This is also a very expensive and inefficient (in terms of energy used) way to generate hot water.

Centralized Solar Hot Water System was developed with back-up gas-fired boilers. The system reduced the electrical load for the site by approximately 7MW when compared to the traditional way of using individual water heaters and CO2 emissions is estimated to be reduced by 7,200 T/year

compared to conventional electrical systems.

2.2.3 Reduce Water Demand

Grey water recovery system was proposed to collect and recycle waste water from showers and washbasins and then re-use this for toilet flushing and irrigation. . Greywater makes up 70-90% of residential water and in arid areas such as Abu Dhabi it had the potential to provide a vital part of the sustainability profile – where it could be used for irrigating the extensive landscaped areas of the scheme as well as more conventional uses, such as toilet flushing.

Water efficient fittings were intorduced to minimize water usage. These would include:

 Dual low flush wc’s

 Spray taps

 Water efficient appliances

 Low flow showers

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3 Mechanical System Design

3.1 Preamble

Mechanical services for Al Zeina comprise the following systems. The HVAC (Heating Ventilation and Air Conditioning) system and Hot water generation system are more fully described in this

dissertation.

 Air conditioning system

 Fresh air supply

 Bathroom and WC extract

 Garbage room extract

 Stair/lobby pressurisation

 Chilled water distribution

 Car park ventilation

 Hot water generation

 cold water supply

 Fire fighting system

 Foul and grey water drainage

 Storm water drainage

 Gas supply

 Irrigation system

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3.2 Design Standards

At the time, there was no one specific set of design standards for projects in Abu Dhabi.

Designs were generally in accordance with the provisions of the relevant ASHRAE

documents, BS EN ISO 9000 series specifications, UK Building Regulations, CIBSE design guidance and good engineering practice.

The following specific documents and standards were used for designing the MEP services:

 ASHRAE standard 90.1 – 2004 ‘Energy standard for buildings except low rise residential buildings’.

 Guide to the Water Supply Regulations (2003) Issued by the Regulation and Supervision Bureau

 Design Standards Manual (Jan 2004) Issued by the Sewerage Projects Committee of Abu Dhabi Municipality

 Customer Metering Regulations (July 2005) Issued by the Regulation and Supervision Bureau

 General Guidelines issued by the Water Distribution Division of ADDC

 ADNOC Distribution Design Guide (June 2006)

 ADNOC Natural Gas Network Adoption Package (July 2006)

 BS EN 81-1:1998 Safety rules for the construction and installation of lifts: electric lifts

 Tabreed ETS connection technical guide Revision 1 Jan. 2007

 NFPA 10 Standard for portable fire extinguishers

 NFPA 13 Installation of sprinkler systems

 NFPA 14 Standard for the installation of standpipe, private hydrants and hose systems

 NFPA 92A Recommended practice for smoke control systems

 NFPA 101 Life safety code

 NFPA 110 Standard for emergency and standby power systems

 NFPA 5000 Building construction and safety code

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3.3 External Environmental Conditions

External environmental conditions for design purposes have been taken to be the values tabulated as follows:

Parameter Data or Description Source

Mean annual rainfall 80mm

Abu-Dhabi weather data

Maximum 24 hour rainfall 51mm

Max design rainfall 37.5mm/h

Maximum ambient temperature 47°C

Maximum and Month Max Min

Abu Dhabi Weather data

Minimum daily Jan 32 6

ambient Feb 36 5

temperature Mar 40 8

(dry bulb) Apr 42 12

May 46 17

Jun 47 21

Jul 47 23

Aug 46 23

Sep 45 18

Oct 42 16

Nov 37 13

Dec 32 7

Maximum and Mth Max Min

Abu Dhabi Weather data

Minimum mean daily Jan 22 13

temperatures Feb 24 14

Mar 27 17

Apr 32 20

May 37 23

Jun 38 26

Jul 41 28

Aug 40 29

Sep 39 26

Oct 35 22

Nov 30 18

Dec 25 15

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Parameter Data or Description Source Maximum temp on metal

surfaces in direct sunlight 80ºC

Relative Humidity

75% max annual

average Abu-Dhabi

weather data

Average Dew Point 17 ºC

Dust concentration in air 1.0-2.0 mg/m3

Abu-Dhabi weather data Average Number of Days with

Blowing Dust/Sand 136/year

Seismic Classifications Zone 2A

Uniform Building Code (UBC) Design Conditions -summer 46 ºC (db) 29 ºC (wb) ASHRAE Design Conditions -winter 10 ºC, 90% RH ASHRAE Average Number of Days with

Precipitation Year 24

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3.4 Internal Design Conditions

Parameter Data or Description

1 Inside Condition DBT- 240 C

RH - 50%( Design

2 Transmission coefficient

U Value

2.1 External Wall 0.44 W/m2 0C

2.2 Service Wall 0.43 W/m2 0C

2.3 Flat Separation Walls 0.54 W/m2 oC

2.4 Typical Celling / Floor betweem 1.359 W/m2 oC

2.5 Floor at Ground floor 0.48 W/m2 oC

2.6 Roof 0.20 W/m2 oC

2.7 Glazing U Value Shading

2.8 Double glazed 1.4 W/m2 0C 0.21

2.9 Doors 2.7 W/m2 0C

3 Building Data

3.1 Building Type Dwelling

3.2 Occupancy (days / Week) 7

3.3 Cooling Plant Operation 1- 24 hrs.

3.4 Atmospheric Clarity Clear to light dusty

3.5 Correction factor

Direct solar 0.85

Diffuse solar 1.2

3.6 Wind Speed

Summer 5 m/s

Winter 7 m/s

3.7 Azimuth angle 216

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Parameter Data or Description

4 Light Load

Dwelling 10 w / m2

retail shop

50 w/m2

5 Equipment Gain

Bed Room 20 w / m2

Bath Room 10 w / m2

Living/Dining 15 w / m2

Lobby 10 w / m2

Corridor 10 w / m2

Retail shop

50 w/m2

6 Fresh air supply

0.35 A/C per Hour Or 7.5

L/s per person which ever greater ( Data From ASHRAE 62.1 2004)

Refer to note

7 Ventilation Requirement

Master bed bathroom 30 L/S

Small bed bathroom 10 L/S

Maid bed bath room 10 L/S

Kitchen 12 L/S

8 No of Occupancy

Master Bed Room 2 Person

Bed Room 1 Person

Maid room 1 Person

Retail 15 Person /100 m2

Note: LEED fresh air requirement 30% extra of ASHRAE standard fresh air requirement indicated in ( 6) (or) 10% more than ventilated air on dwelling indicated in (7), which ever is higher.

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4 Air Conditioning and Ventilation Systems

4.1 Scope and Design Method

Air conditioning was provided to all dwelling units (apartments, town houses and villas) and to the following common areas:

 Lift lobbies

 Plant rooms

 Leisure and amenity areas (some for fit out by tenant)

 Offices, concierge rooms, control rooms, corridors.

Generally, air cooling was provided by fan coil units supplied with chilled water from a site wide reticulation.

Fresh air, where required, is supplied from central air handling units incorporating heat recovery. In some areas (typically corridors) cooling is provided by the supply of tempered air from the fresh air unit.

The ASHRAE 62.1-2004 Standard is used to establish fresh air requirements which align with LEED guidelines to obtain points.

In calculating Fresh Air quantities the following has been adopted highlighting the need to:

1. Obtain LEED points for indoor air quality.

2. Obtain LEED points for reduction of energy.

3. Maintain high quality of life for tenant.

4. Remove objectionable odours.

5. Optimize expenditure by controlling costs.

6. Remove unnecessary ductwork.

7. Comply with the most advantageous international Standard/Code for ventilation design.

Detailed Load calculation, air flow requirements, pipe and duct sizing of Al Zeina were carried out using Hevacomp software.

Hevacomp software is a product of Bently Company. Hevacomp software offer highly productive building energy design, simulation and energy performance certification tools using the emerging industry-standard EnergyPlus analysis engine.

Hevacomp provides accurate simulation and analysis for building load, plant energy, passive design, and dynamic thermal simulations. It supports ISO, CIBSE, and ASHRAE standards, and can be used to provide required compliance checking and documentation, such as that mandated by U.K. part L2, Australia part J, and the U.S. Green Building Council’s LEED program.

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4.2 Chilled water system

Site wide chilled water reticulation has been provided by district cooling center at vicinity called Tabreed. An energy transfer station (ETS) is located in the basement of building D of the project which accommodates heat exchangers provided and installed by Tabreed and secondary chilled water pumps supplied and installed by the MEP contractor.

Secondary pumps deliver chilled water to individual buildings via external buried mains. Secondary flow would be constant temperature, variable flow with pump sets controlled by variable frequency drive. Chilled water supply to each dwelling and retail unit would be metered.

Pressure independent control valves have been designed and placed at all AHUs and FCUs to ensure correct system balance and controllability at part load conditions.

System temperatures are as follows:

Primary system flow temperature 4.44°C Primary systems returns temperature 13.33°C

Secondary system flow temperature 5.58°C Secondary systems return temperature 14.42°C

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20 4.3 Air conditioning and Ventilation- Dwellings

Two alternatives systems are used, single vertical fan coil units and multiple horizontal fan coil units as described below.

4.3.1 Single vertical fan coil unit (FCU)

A single vertical fan coil unit has been designed to be located in the service cupboard adjacent to the apartment. Duct work distributes conditioned air to all rooms via variable air volume (VAV) control units and discharge louvres. A sample layout is shown in figure 4

Figure 13-Example of single vertical FCU in Al Zeina

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21 Room temperature controllers signal VAV units to vary the volume of air supplied to control room

temperature within the range specified. In some instances a single VAV unit serves more than one room due to the site restrictions.

The false ceiling serves as a return air plenum. Where internal walls extend to the underside of the slab within the return air path suitable wall openings were requested to be provided.

Tempered fresh air from a central system is supplied into the return air stream.

The fan coil units were selected to be a vertical free standing unit complete with cooling coil, condensate tray with drain connection, fans, double insulated skin, chilled water connections, top duct outlet with flexible connection, filter (removable from the front sliding out horizontally), bottom air entry, controls, connection box and all power and control wiring.

The units have either an induction motor or electronically commutated motor. The motors are variable speed able to maintain constant pressure with varying air flow.

The unit should be installed in a Service Cupboard, which is part of the owners dwelling and accessible via double doors from the adjacent corridor, mounted on a galvanised steel angle frame, 300mm high, to permit bottom air entry.

The condensate drain connections are piped to waste using uPVC pipework incorporating a water seal trap.

The FCU delivers cooled air via a ducted distribution system to VAV’s metering cold air to each room. A constant delivery temperature is controlled by a 2 way chilled water valve.

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22 Vertical FCU’s were selected as follows:

Supply Fan

 Forward Curved Centrifugal Fan

 Direct drive

 40 to150 Pa external pressure

Filter Section

 Panel Filter G4 pleated synthetic type

Cooling Section

 Copper tube aluminium fin heat exchanger with corrosion resistant coating

 Air flow varies

 Air Temp In 25°C DB

 Air Temp out 12.5°C DB

 Fluid water

 Temp fluid in 5.58°C

 Temp fluid out 14.42°C

 Cooling Nom 12 to 29 kWr

 Connections 25 to 40 mm (Max)

 Stainless steel condensate collection pan with drain

Access Section

 Inspection door

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23 Supply Fan Motor (Variable Frequency Drive, VFD)

 Soft start by VFD, PLC controlled

 Induction Motor

 Pressure sensed/ PLC speed control

 Thermistor protection

 Fan & motor sit on common base frame fully vibration isolated from casing using isolation mounts type Spring/Neoprene

 External VFD

 Motor suitable for VFD.

 Noise to comply with specified criteria.

Supply Fan Motor (Electronically Commutated Motor)

 Soft start by ECM

 Special EC Motor

 Pressure sensed speed control

 Fan & motor sit on common base frame fully vibration isolated from casing using isolation mounts type Spring/Neoprene

 Integral speed controls

 Noise to comply with specified criteria

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24 Acoustic control

Units with operating at full speed should comply with the following noise criteria:

Bedroom < 30 LAeq*

Living room < 35 LAeq*

Dining room <35 LAeq*

Kitchen 45 dB(A) Laundry 50 dB(A)

The following measures were requested to be incorporated as part of acoustic control practice:

 All duct connections shall be effectively sealed to prevent leakage.

 The first 3 to 5 meters of supply duct, including the bend, shall be internally lined with either 25mm or 50mm of mineral wool insulation with facing material to prevent fiber shedding at air velocities up to 20m/s.

 All gaps between the service cupboard (housing the fan coil unit) and the dwelling shall be effectively caulked

 Soft joint shall be maintained across flexible connections.

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25 Control of vertical FCU

Start/Stop:

Start is initiated by room controller in lounge/dining room including temperature control. The other rooms have individual temperature control. Automatic air volume control would be by VAV unit.

Temperature Control:

The room temperature is controlled in each room by a temperature sensor which modulates the airflow through a duct mounted VAV serving each room. Each room has a temperature controller connected to the VAV supplying that space. Low limit airflow has been designed equal the minimum fresh air required for the space. The cooling coil off temperature is designed to be maintained at approximately 12.5^oC to ensure room design temperature is maintained (24^oC). This is achieved by temp sensor in the supply air duct signalling a PLC which in turn modulates the coil 2-port valves controlling CHW flow.

Figure 14_ Control Schematic of Vertical FCU’s

An Electronically Commutated fan motor(s) are installed in the FCU or a VFD and are connected to the FCU, controlling the fan motor RPM. The FCU in this design type shall provide constant pressure in the supply air duct. A supply air pressure sensor located within the fan assembly of the EC motor or in the output duct would measure the supply air duct pressure. The sensor will signal the integral fan control unit in the EC motor or the VFD to control the fan RPM.

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26 Upon low limit setting of the room temperature controller the room may be overcooled. If the room

temperature is too cold with the VAV closed to its minimum setting a “low temp” signal would be sent to the PLC which will raise the coil air off temperature by varying the CHW flow. Progressively the air off temp will rise in 0.5^oC steps from 12.5ºC to a max of 18ºC.

Variable air volume units (VAV)

These units were designed to be pressure independent variable air volume terminal units comprising galvanized sheet steel casing with mineral wool lining, control damper, differential pressure sensor and transducer, electric actuator and controller, spigot connections and room temperature sensor for wall mounting within the room to be served.

Figure 15_ Typical VAV box installed in Al Zeina Project.

Spigot connection on high pressure side is asked to be circular, discharge side rectangular.Acoustic lining in the attenuator section should be mineral wool with facing material to prevent fibre shedding at air velocities up to 20m/s. A differential multipoint pressure sensor is designed to be located in the inlet section

Controller/transducer and actuator are to be attached to the outside of the casing and are to be factory wired, calibrated and tested.

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27 VAV mode of operation

Air flow through the unit generates a pressure at the differential pressure sensor that is passed to the transducer high and low pressure connections via control tubing. The transducer converts the effective pressure into an electronic signal which is transmitted to the controller and compared with the set point from the room temperature controller. If there is any variance a signal from the controller shall adjust the damper actuator accordingly.

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28 4.3.2 Multiple horizontal Fan coil units

In single bedroom apartments and where space limitations precluded the use of a single vertical FCU, multiple units were considered to be mounted horizontally within ceiling spaces and controlled directly by room thermostats to maintain room conditions within the specified range. Tempered fresh air discharges into return air path.

Figure 16_ Typical horizontal FCU installation

Fan coil units were specified to be horizontal double skinned complete with cooling coil, fan, chilled water connections, valves, flexible connection, horizontal duct outlet, filter removable from below, sliding out vertically, condensate tray with drain connection, controls, connection box and all power and control wiring.

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29 FCU's should have a 3 speed motor suitable for direct on line starting.

The condensate drain connection should be piped to waste using uPVC pipework incorporating a water seal trap.

Temperature control is by room sensor controlling a 2 way chilled water valve (Pressure Independent Control Valves).

Acoustic control

Units with operating at medium speed should comply with the following noise criteria:

Bedroom < 30 LAeq*

Living room < 35 LAeq*

Dining room <35 LAeq*

Kitchen 45 dB(A) Laundry 50 dB(A)

Horizontal FCU’s were selected as follows:

Supply Fan Motor (3 speed)

 Direct On Line starting

 Capacitor start Motor

 Wall speed switch

 Fan & motor sit on common base frame fully vibration isolated from casing

 Direct drive

Filter

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30 Cooling

 Copper tube aluminium fin heat exchanger with corrosion resistant coating

 Air flow varies

 Air Temp in 25°C DB

 Air Temp out 12.5°C to 24°C DB

 Fluid water

 Temp water in 5.58°C

 Temp water out 14.42°C

 Stainless steel condensate collection pan with drain

Control of horizontal FCU Start/Stop:

Start is initiated by any room controller controlling only the unit serving that room.

Temperature Control:

Each Dwelling with multiple FCU’s ducted to individual rooms should have a dedicated thermostat for each room connected to the single FCU for that room. Each controller would have temperature selection, a choice of 3 speeds and on/off control. The thermostat in each room modulates the flow of chilled water to each FCU coil.

Figure 17- Control Schematic of Horizontall FCU’s

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31 The thermostatic wall controller near each room outlet controls room temperature by increasing or

decreasing the amount of chilled water entering the cooling coil.

The thermostat mounted on the dwelling wall near the return air grille responds to a call for cooling by comparing the actual air temperature in the room with the set point selected by the occupant. If the room temp is higher then the CHW modulating valve would open to allow a greater volume of chilled water to flow to the cooling coil.

When the two temperatures match then the valve reduces the water flow.

4.3.3 Kitchen, bathroom and toilet extract

All bathrooms, toilets, kitchens and laundries in Al Zeina project are provided with an extract ventilation system, replacement air entering via door undercuts. Extract fan is located within the fresh air handling unit.

As the extract system forms part of the integrated a/c system within dwellings, it will operate 24 hours per day. The extract air is ducted back to the enthalpy wheel of the fresh air handling unit on each roof to recover cooling heat energy.

The Exhaust rate is to be:

Each bathroom and laundry exhaust at 10 L/sec plus each kitchen exhaust at 12 L/sec.

The airflow into the apartment must be 10% greater than the Exhaust from the apartment to maintain the positive pressure.

EXHAUST AIR:

Example calculation for apartment type 7 with 5 bedrooms 5 bathrooms plus a laundry at 10 L/sec each

6 x 10 = 60 L/sec

Then the kitchen exhaust at 12 L/sec (continuous) 60 + 12 = 72 L/sec total exhaust for the apartment.

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32 4.3.4 Ductwork

Distribution ductwork within dwellings are considered to be a pre-insulated ductwork system comprising a sandwich panel of fire resistant expanded, rigid, phenolic resin foam sheathed both sides with aluminium foil.

The duct material is selected to have the following properties:

 Suitable for maximum duct velocity of 15 m/s and maximum total pressure of 1kPa.

 Maximum density of 55 kg/m³

 Maximum thermal conductivity of 0.025 W/mK

 Comply with Class 'O' based on BS 474 parts 6 and 7 for fire propagation and flame spread.

 Duct air leakage to be within the limits of DW144 class C.

4.3.5 Grilles and diffusers

Air terminal devices were selected to be single deflection linear bar grilles with horizontal fixed front louvre blades adjustable rear blades and opposed blade damper. Frame and front blades should be finished in white powder coat and rear blades should be finished matt black.

Exhaust grille in kitchen and laundry were selected to be square core 4 way discharge diffusers white powder coat finish.

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33 4.4 Air conditioning and ventilation - common areas.

Common areas of the building (corridors, lobbies, plant rooms, management offices, workshops, stores etc.) are designed to be cooled and/or ventilated in one of two ways:

 Cooling by chilled water fan coil unit

 Cooling by conditioned fresh air supply only

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34 4.5 Central fresh air supply

Heat recovery air handling units have been designed and sized to supply cooled and de-humidified fresh air to dwellings and other areas and recover cooling heat energy from exhaust air.

Units incorporate fresh and exhaust air filtration, enthalpy recovery wheel (sensible and latent), heat pipe run around coils, chilled water cooling coil and centrifugal fans with variable speed drive.

Roof mounted units were asked to be of totally weather proof construction, suitable for use in an exposed marine environment.

Fresh air then is distributed by rectangular ductwork, incorporating volume control dampers on all main branches and fire dampers where ductwork crosses fire compartment walls and floors. Sound attenuators were also designed to be located at both intake and discharge side of the fresh air handling units.

AHRAE Standard 62.1-2004 states that fresh air to living areas are to be 0.35 air changes /hr for the entire apartment interior volume or 7.5 L/sec / person using the greater value.

Head count to be:

First bed room 2 persons, all other bedrooms to be 1 person each.

To obtain LEED point 30% needs to be added, this will be the FA supply.

FRESH AIR:

Example calculation for apartment type 7 with 5 bedrooms and 634.4 m3 total volume 0.35 ach/hr x 634.4 m3 (total volume) /60 x 60 = 61.7 L/sec

OR Bedroom 1 = 2 persons Other bedrooms = 1 persons each

Total Bedrooms are 5 therefore 6 persons design occupancy 6 x 7.5 L/s = 45.0 L/sec.

The greater is 61.7 then adding 30% to satisfy LEED = 80.2 L/sec is the fresh air for this apartment.

It should be check that the FA is 10% greater than the exhaust to pressurize the apartment:

For Apartment Type 07

(80.2 – 72) / 80.2 = 0.102 or 10.2% = pressurized

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35 4.5.1 Fresh air handling units

Figure 18-FAHU in Al Zeina

Figure 19- FAHU with recovery wheel

Fresh air handling units were designed to have following properties:

General

The units maximum height were stipulated in order to comply with limits set by Abu Dhabi civil aviation authorities of 2.5 metres to top of unit from roof structural slab level .

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36 Access Sections

Inspection door

Outside air Entry Module

 Bird screen

 Sand trap louvre

 Panel Filters and Bag Filters before the Enthalpy Wheel

 Noise attenuator

Exhaust air Exit Module

 Bird screen

 Panel Filters to protect the Enthalpy Wheel

 Noise attenuator

Filter Section (Outside air)

 High efficiency bag filter

Filter Section (Return air)

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37 Enthalpy Wheel

Figure 20- Recovery Enthalpy Wheel

 To remove heat and moisture from the incoming airstreams.

 Outside Air on wheel 45.4^oC DB at 31^oC WB

 Outside Air off wheel 31^oC DB at 23^oC WB

 Recovered Air on wheel 30^oC DB at 23^oC WB

 Recovered Air off wheel 40^oC DB at 27.5^oC WB

Cooling Section

 Copper tube aluminium fin heat exchanger with corrosion resistant coating.

 Temp on coil 24.0^oC DB

 Temp off coil 15.5^oC DB 15.3^oC WB

 Fluid chilled water

 Temp fluid in 5.58^oC

 Temp fluid out 14.42^oC

 Pressure loss fluid 31 kPa (estimate)

 Fluid quantity varies

 Cooling Total varies

 Cooling Sensible varies

 Connections 65/80 mm

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38 Wrap Around Heat Pipe (approx)

 Air On A 30^oC D DB

 Air Off A 24^oC WB

 Air On B 15.5^oC DB

 Air Off B 22.5^oC WB

Supply Air

 Leaving the FA-AHU unit at 22.5^oC DB and 18.0^oC WB

Fan type

 Forward Curved Centrifugal

 Belt Drive

Fan motors

 Soft starting (VFD)

 Duty Motor

 Motor Rating Variable kW

 400V/3-phase/50 Hz supply

 Fan & motor sit on common base frame fully vibration isolated from casing using isolation mounts type Spring/Neoprene Mounts

 Motors suitable for VFD.

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39 Control of fresh air handling unit

The fresh air handling unit should be PLC controlled to deliver constant volume, constant temperature air flow.

Figure 21- Fresh Air Handling Unit Control Schematic

Inputs to the PLC:

1. Duct pressure from the FA delivery duct to the building dwellings.

2. Temperature from the FA delivery duct to the building dwellings.

3. Smoke detector at the return air duct from the dwellings.

4. Pressure from the return air duct.

5. Pressure differential across the enthalpy recovery wheel.

6. Pressure differential across the Incoming filtration set.

Outputs from the PLC:

1. VFD speed settings for both return and supply air fans 2. Fault and status monitoring data to BMS

3. Modulating CHW valve settings.

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40 4.5.2 Ductwork

Supply and return air ductwork from fresh air handling units were designed to be either rectangular sheet metal ductwork or pre-insulated ductwork.

Sheet metal duct should be used:

 On roofs

 Within riser shafts

 Within car parking areas

 Within plant rooms

 In all other areas where pre-insulated duct was not practical

Pre-insulated duct should be used:

 Within all dwelling units

 Within corridor ceilings where ductwork supplies dwelling units, corridors and lobbies

All sheet metal supply and extract ductwork within the building are insulated with 50mm thick mineral wool rigid batts, enclosed in GRP reinforced aluminium foil. Externally, ductwork are insulated with 50mm thick mineral wool rigid batts enclosed with 6 oz cotton canvas coated with proprietary sealant which form a vapour seal and durable weatherproof finish.

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41 4.6 Chilled Water

4.6.1 Chilled Water Pumps

Nine chilled water pumps were designed to be placed in the ETS Room and connected to the chilled water reticulation system. The pumps are centrifugal end entry top discharge, close coupled to a TEFC motor suitable for variable frequency drive (VFD) control with adequate cooling at low RPM.

Installed pumps comply with the following standards:

o BS EN 60335-2-51:2003.

o BS 4082:1969 Parts 1 and 2 o BS 5257:1975.

Figure 22¬Chilled water pump room-Al Zeina

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42 4.6.2 Chilled Water Pump Control

The pumps speed is controlled by individual VFD’s at each motor control centre. The pumps switch in and out as controlled by a PLC in the adjacent Control Room. The pumps hold constant pressure as

measured at several extremities of the pump network. If pressure at these points drop below the design pressure then the pumps will increase in RPM until the design minimum pressure is exceeded. As the demand for a greater volume increases then the pumps in duty will increase in RPM until the efficiency of the group drops. At that point another pump will be called to increase the flow. These pumps will drop in flow to a more efficient point on the pump curve. Conversely if less water is required then the pumps on line will drop in RPM until the pumping becomes inefficient. At this point a pump will drop out of service and the remaining shall increase in RPM to hold efficient running. The system will continually modify the number of pumps at optimum efficiency. The PLC will hold the RPM of the pump to within 10% of its optimum efficiency. The pumps are selected to have pumping efficiency greater than 0.82.

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43

Figure 23- Chilled Water Control Schematic

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44 4.6.3 Chilled water control valves

Pressure independent control valves are designed to be fitted to all chilled water system terminal units i.e.

fan coil units and chilled water coils of fresh air handling units, in order to limit differential pressure and maintain valve authority.

For fan coil units, control valves are 2 port with compatible 0 -10 volt fully modulating actuator, in-built differential pressure control valve and tappings for flow measurement. Valves are suitable for a maximum differential pressure of 16 bar (pressure class PN 25).

Figure 24-FCU valve arrangement

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45 For Fresh air handling units control valves are 3 port with compatible 0 - 10 volt fully modulating actuator and separate self acting differential pressure controller. Valves are suitable for a maximum system and differential pressure of 16 bar (pressure class PN 25).

Figure 25-FAHU valve arrangement

Pressure independent control valves and differential pressure controllers are requested to be factory set for the design flow and be capable of adjustment on site using manufacturer’s calibration charts.

Additional measurement devices for flow verification, comprising stainless steel fixed orifice plates with flow measurement test points are also designed for the chilled water system. These are specified to be installed in straight uninterrupted lengths of pipe leaving 10 pipe diameters to the unit and 5 pipe diameters from the outlet.

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46 4.6.4 Chilled water system pressurization

The chilled water system is pressurized by a sealed diaphragm vessel system comprising:

 pressurisation unit with run and stand-by pumps

 expansion vessels,

 break tank and fill connection,

 deaeration unit,

 self contained control system with BMS connectivity

 water meter

The integral control panel comprises:

o Automatic changeover of duty/standby pump o Hand/off/auto switch for each pump

o Run/trip lamp for each pump o Power ‘on’ lamp

o Pressure gauge

o High/low pressure indication and protection with warning lamp o Low water cut-out with warning lamp.

o Hours run meter for each pump.

o Volt free contacts for remote monitoring of run and alarm status via a BMS.

The water make-up system includes a cumulative type water meter to monitor water make-up rates.

System pressures:

 Low fault 5.90 bar

 Cold fill 5.50 bar

 System 6.20 bar

 High fault 6.50 bar

 Safety valve 7.13 baR

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47 4.6.5 Chilled water pipework

Within the ETS room, secondary chilled water pipework is selected to be steel. Secondary distribution pipes from the ETS room, via underground mains to individual building entry points are ABS. All chilled water distribution within buildings are in ABS pipework. All pipework, valves and fittings have a minimum pressure rating of PN16.

Thermal insulation is applied to all chilled water pipework and vapour sealed. Within corridor ceilings and riser shafts this is to comprise 25mm thick phenolic foam sections with bonded aluminium foil facing.

Externally and In plant rooms and where exposed to view within the buildings, insulation comprises 50mm thick mineral wool rigid sections enclosed with 6oz cotton canvas coated with proprietary sealant to form a vapor barrier and durable weatherproof finish.

Figure 26-Chilled water insulation

External buried pipework are factory pre-insulated ABS with CFC free polyurethane foam insulation - 50mm thick - and ABS outer casing.

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48 4.6.6 Chemical dosing system

Packaged automatic dosing system sized to suit the total water capacity of the system.

The dosing pot is fitted with the followings:

Air cock

Conical filling funnel No-return valve

Isolating valves on the flow and return connections Drain valve

The dosing pot is located in the plant room and it positioned to allow proper access for maintenance and operation without spillage. System is filled with softened water having a total hardness less than 5mg/litre as CaCo₃.

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49 4.7 Car park ventilation

4.7.1 General

Car parking areas are mechanically ventilated to limit the build up of carbon monoxide from vehicle exhaust and to clear smoke in the event of fire. The system comprises

 Supply air fans,

 Exhaust fans,

 Fire rated duct work

 Control system (incorporating logic controller (PLC)),

 Addressable CO sensors,

 Addressable smoke detectors,

 Interconnecting wiring and cable containment.

All fans are set to three-speed; low speed for normal operation, medium speed in CO mode and high speed for smoke exhaust. Fans are controlled by CO sensors and smoke detectors with manual override from the buildings fire alarm control panel. Supply and exhaust fans serve more than one car park level and motorized dampers are provided to direct air flow to the fire/ CO affected floor.

4.7.2 Computerized fluid dynamic analysis

Prior to design of car park ventilation system, a specialist was appointed to carry out CFD modeling to demonstrate correct air movement and compliance with minimum CO levels and to confirm the number and location air intakes/ outlets.

Criteria for CFD were:

 Minimum air velocity across the car park to be greater than 0.1m/s.

 There shall be no dead spots.

 Due consideration to be given to openings such as ramps etc which are open to atmosphere or other car park levels.

 The CFD to be run with fans operating at low speed for pollution control at 3 air changes per hour for each floor.

 The CFD to be run with fans operating at medium speed for CO control at 6 air changes per hour for each floor.

 The CFD to be run with fans operating at high speed for fire control at 10 air changes per hour for each floor.

 All simulations in both fire mode and CO dilution mode to be carried out at 1.5m and 2.6m above finished floor level.

Final positioning and sizing of sensors and equipment were done after this analysis.

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50 4.7.3 Supply and exhaust fans

Supply and exhaust fans are fire rafted, axial flow, variable speed and complete with starter, local isolator and wiring from the motor control centre.

Supply and exhaust fan rooms and plenum chambers incorporate sand trap louvres, motorised dampers, discharge louvres and sound attenuators.

All fans are designed to be equipped with a flow measuring device. The flow measuring device enable the measuring of flow by the provision of pressure tappings and connecting tubes. A pressure tapping at a predetermined position on the inlet cone is provided, by the manufacturer, whereby the differential pressure in relation to the static pressure can be measured in front of the inlet cone in static atmosphere.

This differential pressure indicates a direct relationship to the flow rate. In order to calculate the flow rate a calibrating factor was required to be established by the manufacturer produced from test rig results carried out in accordance with DIN 24-163-2.

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51 4.7.4 System operation and control

The system will be fully automatic and does not require any human intervention, either in the vehicle emission mode or the fire mode.

The zones have continues normal ventilation and will function individually for motor vehicle emission control (carbon monoxide dilution) and smoke management. The system is the same for all modes; only the operation will be different.

Carbon Monoxide Control

CO concentrations will be sensed via strategically located addressable CO sensors, and the position identified by the PLC.

The CO signal will be identified by the PLC which is programmed to start the fans in proportion to the CO level recorded.

The car park CO sensors will signal the PLC and progressively move the high concentrations of CO to the exhaust opening. Motorized damper sets installed between all levels will isolate the car park level not requiring CO control.

Approximate settings:

 At 30 PPM the PLC will start the fan(s) in low mode or one exhaust and one supply fan into operation. Only the level requiring CO dilution will be selected using motorized damper sets.



 At 100 PPM 60% of the supply/exhaust fans will operate.

 At approximately 250 PPM all fans will be at high speed.

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52 Fire Mode

In the Fire Mode it is assumed that only one fire incident will occur at any one time.

Upon a signal from any of the strategically positioned addressable smoke detectors, all fans in the fire affected zone will stop. The PLC controlling the system will identify the location of the fire (by the respective smoke detector) and will isolate the fire affected zone by immediately closing motorized dampers.

The system will then wait for a signal from the fire alarm system - initiated by operation of a sprinkler head or smoke detector connected to the fire alarm system

A brief time (adjustable) will be allowed before any fan will be called to operate. In this time an orderly evacuation is called for in which all persons will leave the fire affected area.

Any smoke generated by the fire will then remain at the fire point rising to the ceiling and not block any evacuation routes.

At the end of the evacuation period the PLC will now call for the fans to operate to deliver the pre selected air quantity for the fire selected Fire Zone. This is a high air flow of at least 10 air changes per hour.

The same procedure, including the time delay period, will be initiated by the fire alarm system in the absence of a signal from the car park ventilation smoke detectors.

The system will be linked to the Fire Indicator Panel which will incorporate means for authorized Fire Dept Personnel to override the system controls.

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53 4.8 Stair/Lobby pressurization

Systems have been designed in accordance with NFPA 92A to provide positive pressure differential between stairs well and lobby and a positive pressure differential between lobby and corridor.

4.8.1 Stairwell pressurization

Pressurization systems for the stairwells generally comprise run and standby axial flow fans at roof level, serving a vertical riser shaft within the stairwell having supply louvres at alternate levels. A barometric pressure relief damper is provided at the top of the stair well to limit over pressure that may hinder opening of doors.

Fans are variable speed, fully weatherproof construction and fitted with anti back draught shutters. Fan isolators and connection boxes are weatherproof IP54. Control panels incorporates differential pressure switch for monitoring of air flow status (with appropriate connections), link to fire alarm system to start the fans, contacts for BMS monitoring of fan and airflow status, changeover contacts to start the stand-by fan in the event of failure of the lead fan.

Where systems serve four levels or less a simpler system of wall mounted/ roof mounted axial fans, run and stand-by, without distribution ductwork are designed. Fans incorporate weatherproof cowls, integral flashing/soaker plates, bird guard and anti back draught shutters.

4.8.2 Control of stair pressurization system

Fans will be started on a signal from the fire alarm control panel. In the event that the lead fan fails to start (sensed by differential pressure across the fan) the stand-by fan shall automatically start.

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54

Figure 27-Pressurization schematic

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55 4.8.3 Lift lobby pressurization

Pressurization systems for lift lobbies comprise run and stand-by axial flow fans at roof level serving a vertical riser shaft within the lift core.

Fans are variable speed, fully weatherproof construction and fitted with anti back draught shutters.

Control panel incorporate differential pressure switch for monitoring of air flow status (with appropriate connections), link to fire alarm system to start the fans, contacts for BMS monitoring of fan and airflow status, changeover contacts to start the stand-by fan in the event of failure of the lead fan, variable speed drive for system commissioning.

Fan isolators and connection boxes are weatherproof IP54.

Air will discharge at each level served via a branch duct incorporating a constant air flow damper A duct pressure sensor is provided within the supply duct for control of the fan.

4.8.4 Control of lobby pressurization system

Fans will be started on a signal from the fire alarm control panel. In the event that the lead fan fails to start (sensed by differential pressure across the fan) the stand-by fan shall automatically start.

Fan speed will be regulated in response to a signal from the duct pressure sensor to maintain the value set at commissioning.

4.8.5 Commissioning of pressurization systems

Stairwell and lobby pressurization systems have been commissioned in accordance with the procedures set out in Chapter 5 of NFPA 92A using the following criteria:

 Pressure difference across doorways with door closed: 12.5 Pa

 Maximum pressure difference across doors as Table 2.2.2 of NFPA 92A

 Doors assumed open for stairwell pressurization system: 3 (one to outside, two into lobby)

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56 5 Solar Hot Water System

5.1 Hot Water Supply

Central roof mounted hot water plants have been designed for Al Zeina project to supply water to outlets at 60°C. Water will be heated by flat plate solar collectors with 100% boiler back up. Boilers are fired by natural gas. The system is provided with pumped circulation to offset mains heat losses. Circulation will terminate outside of each dwelling. Hot water supply to each dwelling unit served by the central hot water system will be metered. Electric water heaters for beach villas shall be a single central unit for each villa located in the basement with pumped circulation. Hot water supply will not be metered.

5.2 Abu Dhabi Solar Radiation Data:

According to Abu Dhabi radiation data;

 Total radiation per year = 1947.5kWh/m2/year

 Average radiation per month = 135kWh/m2/month

 Average radiation per day = 5.6kWh/m2/day

 Total radiation for summer = 1223kWh/m2

 Total radiation for winter = 810kWh/m2

 Diffuse Radiation Percentage= 45.2%

5.3 System Description and Control

Domestic hot water is generated by roof mounted centralized solar plant for all buildings. Water from cold water tanks would be boosted to the hot water buffer tanks to get first heated by solar system/ gas boilers and then supplied to the dwellings.

The central plant comprises:

 Flat plate solar collectors

 Condensing gas boilers

 Primary circulation pumps

 Plate heat exchangers

 Secondary circulation pumps

 Buffer tanks

 Controls and ancillaries

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57 Solar plant rooms accommodate two sets of tank. Pre- Heat cylinders which are connected to the solar side and Stand-by cylinders that are connected to the boiler side water to the dwellings is supplied from the stand by cylinders. Water from Pre-Heat tanks gets transferred to the Stand-By tanks via anti- legionella set of pumps to maintain the temperature all the time.

In a normal day, the control unit monitors whether the Pre-Heat cylinders can be heated with solar energy from the solar panels. The control unit compares the solar panel temperature (SPS) and the Pre-Heat cylinders temperature (SPH). If there is adequate solar radiation i.e. the set temperature differential between SPS and SPH exceeded 10 K, the pump of solar side starts and the cylinders are heated.

If there is little solar radiation, the pump speed is reduced to maintain a constant temperature differential.

This allows the cylinders to be heated with low power consumption. The control unit does not switch the pump off until the temperature differential has dropped below 5 K.

After a long period of solar radiation and low domestic hot water consumption, high temperatures occur in the pre-heat cylinders. The control unit switches the pump off when the maximum cylinders temperature is reached during heating. The maximum preheat cylinders temperature can be adjusted up to 90°C.

With high levels of solar yield, the Pre heat cylinders can also achieve higher temperature than the stand by cylinders. To enable the use of the entire cylinders volume for solar heating, a pipe (using anti

legionella pump) will be routed from the hot water outlet of stand by cylinders to the cold water inlet of the pre heat cylinders.

When the water temperature in the stand by cylinders becomes below the design temperature, the control unit will check the temperature of the pre heat cylinders. If the temperature of the pre-heat cylinders is high enough to heat the stand by cylinder normal operation will keep on going to supply hot water from pre heat cylinders to the stand by cylinders. If the water temperature in the pre heat cylinders is not sufficient to raise the stand by tanks temperature the control unit will check the solar panel temperature to see if the temperature difference between SPH and SPS is more 5K to run the solar pump otherwise to run the boilers.

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58

Figure 28- Generic solar hot water schematic at Al Zeina

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59 5.4 Solar collectors

Panels are glazed flat plate solar collectors, roof mounted, oriented and inclined to optimize performance (minimum the annual gas consumption for back-up heating) over the yearly cycle and designed to ensure high absorption of solar radiation and low emission of thermal radiation. Panels are tilted at 40° in order to get maximum radiation in winter time.

Collectors are selected to be CE designated in accordance with EN12975 and certified to solar Key mark.

Figure 29- Solar panels at Al Zeina_ Make: Logasol SKN 3.0

Figure 30-Solar panels at Al Zeina

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60 5.5 Hot water pipework

Distribution pipework within the plant rooms and to solar panels would be copper pipe and elsewhere the distribution pipework above 110mm nominal size would be polybutylene (PB) or polyethylene and up to 110mm nominal size would be polypropylene (PPR). Pipework systems and materials comply with BS 6920 and BS 7291. All pipework, valves and fittings have a minimum pressure rating of PN10.

Automatic thermostatic control valves have been installed on each return branch of the secondary circulation system for flow balancing.

5.6 Hot water pressure booster pumps

Figure 31-Vertical multi stage booster set_ Make: Grundfos

Pressure booster pumps are selected to be vertical multi-stage supplied as packaged pump sets

complete with control panel, valves and interconnecting pipework. Motors are totally enclosed, fan cooled, IP54 and suitable for 400volt, 3 phase supply.

Pumps are automatically controlled to maintain a delivery pressure at the outlets served within the range 1.5 to 3.0 bar gauge.

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61 5.7 Condensing boilers

Figure 32- Boiler at Al Zeina_ Make: Buderus

Boilers are selected to be suitable for firing on natural gas and are to sized to meet the full domestic water load in the event that heat from solar collectors is unavailable.

Each boiler is fitted with the followings:

• Safety valve.

• ¼ turn isolating ball valves on the primary flow and return connections.

• Pressure gauge.

• Temperature gauge on flow and return connections.

• Drain cock(s) with removable key.

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62 5.8 Heat exchangers

Stainless steel plate heat exchangers are provided between the solar collectors and the buffer tanks to separate primary and secondary circuits.

5.9 Buffer tanks

Insulated, horizontal or vertical, cylindrical storage vessels with heating coil suitable for low temperature boiler primary heating. Vessels are selected to be suitable for minimum 7 bar working pressure.

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63 5.10 Hot water consumption

Chart below represents the hourly how water consumption (in liter) in winter for Al Zeina project which the solar systems have been sized/designed for each system.

DEPARTMENT OF TECHNOLOGY AND BUILT ENVIRONMENT