Destrict Cooling Presentation

8/3/2019 Destrict Cooling Presentation

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Objectives:The attendees may be able to gain a better understanding of fundamental of humanthermal comfort, Thermal heat gains in buildings, Climate and design conditions, Heatgains from solar and other sources, ventilation principles, fan coil units, Air handlers,BMS, Refrigeration Plants and applications, benefits of District cooling and DCS systemdetails.

Speaker: Fabian Jayasuriya

MSc. (Eng.), C Eng., MCIBSE, MIET, MASHRAE

Technical DirectorEmirates District Cooling L.L.C

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The body core temperature associated with a healthy human body is37C (98.6 F) and in order to remain comfortable the body attemptsto maintain thermal equilibrium with the surroundings.

Thermal balance between the body and its surroundings occurs bymeans of:

i. Evaporation

ii. Radiation

iii. Convection

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The environmental factors that influence the modes of heat transferand hence, thermal comfort are:

i. Dry bulb temperature

ii. Relative humidity

iii. Air movement rateiv. Mean radiant temperature

Two other personal factors are also influential, namely:

i. Activity level

ii. Clothing

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Degree ofActivity Total Rate ofHeat Emissionfor Adult Male(Watt)

Average Valueof Male &Female (Watt)Sensible (Watt) Latent (Watt)

Seated 115 95 65 30

Walking 160 130 75 55

Dancing 265 230 90 160

Sedentary Work 160 130 75 55

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Air Velocity

(m/s)0.1 0.2 0.25 0.3 0.35

Dry bulb

Temp. C

25 26.8 26.9 27.1 27.2

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It is essential that the buildings be adjusted to serve people. Itshould not be the people who are required to be adopt to thebuildings.

Summer design temperature of 22C - 24C is a suitable choice forlong term sedentary occupancy in the U.A.E with humidity allowed

to swing between 50% -60% having air movement of 0.1 m/sec.

Benchmark optimum energy usage in summer satisfying thermalcomfort criteria with room temperature of 24C at 55% humidity.

Higher energy penalty in lowering of room temperature from thebenchmark level. Example, room temperature thermostat set at23C will increase 9% more energy consumption. At 22C, 18%energy penalty.

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i. Solar gain through glazingii. Transmission gains arising because of temperature differences

between the room and the outdoor air temperature.

iii. Transmission gains due to outside surface temperature rise withthe impact of solar radiation.

iv. Infiltration of warm humid airv. Room occupants

vi. Electric lighting

vii. Electrical equipment such as computing equipment andphotocopied.

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ConductionHeat Transfer by molecular motion in a material in direct contact

ConvectionContact Between fluid in motion and a solid

RadiationNo contact required. Heat transfer by electromagnetic waves

Units & MeasurementsThermal conductivity (k or ) = W/m/0K

Thermal Resistance (R) = d/ k in m2 0K/W ( d = Thickness )Heat Transfer coefficient or Thermal Transmittance (U )

U = 1/R Watts / m2/ 0KSteady state Heat Transfer Equation (One dimensional Heat flow ) Q =U A

T WattsA = Area in m2 , T = Temperature difference in 0K

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Ventilation Heat Gain CalculationHeat gain due to ventilation (Qv ) = q m (h ao - h ai) Wattsq m = mass flow rate ( kg/sec.)h ao = Enthalpy of outdoor airh ai = Enthalpy of indoor air

Simplified equation without considering moisture in airQv = q m Cp (t ao - t ai ) WattsVolume flow rate in Litres /Sec. ( q v )Qv = 1.2 q v (t ao - t ai ) ------------- 1Simplified Heat flow equation with number of air changesQv = NV/3 Watts ------------- 2Where N = number of air changes , V = Room Volume in m3

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The Sun radiates energy as a black body having a surfacetemperature of 6000 0 C over a spectrum of wave length 300 470nm in ultra violet region.

9% - ultra violet region

91% - 380 to 780 visible and infrared region

Solar constant : 1416 watt/m2 maximum What reaches the earth is 1025 watt/m2 at no clouds Direct solar radiation - 945 watt/m2 Heat enters a building through direct and scattered radiation

Boltzman Equation for radiant heat:

Q = A T4 wattsWhere = 5.663 x 10 - 8 J//m2s K4A = area in m2 ,T = temperature in 0K

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The impact of solar radiation varies upon the building location andorientation

Building walls: Colour of the surface Surface roughness Building material Sunlit area

Building Roof Slope of the roof Roof material Colour of the roof Surface reflectance

Building Windows : Sunlit area Glass type , thickness and colour Reflectance factor Shading coefficient ( a property of glass )

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Conductive

(55 W/ SQ.Mt.)

43%

Convective( 40 W/SQ.Mt.)

34%

Radiation(20 W/SQ.Mt.)

18%

Occupancy +Electrical

(5W/SQ.Mt )5%

HEAT LOAD IN A BUILDING(Total Load 120 W/SQ.Mt. )


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Degree hours or Degree days concept provides a measure to assesscooling energy demand hours based on the temperature differencebetween inside and outside of a building as related to period of timeunder consideration.

Example:

i. At external outdoor temperature 28C and indoor temperaturesetting at 24C in a particular hour cooling demand is consideredas 4 degree hours.

ii. As the outdoor temperature changes hourly, If the total degreehours within a 24 hours period is added up to a value of 60degree hours, then the average cooling demand is considered as

2.5 degree days.

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As base temperature of 24C calculated degree hours for the year 2010 &2009 in Dubai is indicated below.

It was reported that the year 2010 matches for world hottest year (see GulfNews article on 21st January 2011). The attached degree hour calculationsheet indicate the influence of temperature variation for space cooling.Based on calculations summary of degree hours for each month is as follows:

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Year: 2010

Month January February March April May June July August September October November December Annual Total

Total Degreehours

110 680.0 1687.6 3659.1 6339.9 8422.9 9934.5 9615.9 7446.8 5437.9 2171.8 469.5 55975.9

Year: 2009

Month January February March April May June July August September October November December Annual Total

Total Degreehours

27.3 696.2 1433.3 2979.2 6735.5 7544.3 8283.4 8873.8 6936.9 4871.6 2065.2 265.6 50712.3

The number of Degree hours excess in year 2010 compared with 2009 is 5,263.6

Percentage increase: 10.4%

Summer months (April - November increase) 9.8%


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The need for ventilation :

Fresh air required for breathing

(0.2 litres/sec.) directly proportional to metabolic rate

Dilution of the orders present to a socially acceptable level (7.5litres/sec. )

Minimize the rise in air temperature in the presence of excessivesensible heat gains

Dealing with high humidity or condensation

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Natural Ventilation is the air flow through a building resulting fromthe provision of specified routes such as:

Operable windows

Doors

Shafts

Ducts

Towers

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Avoid noise and traffic fumes from busy roads Consider Security

Consider Insects

Draw cooler air from a shaded side of a building to maximise thecooling

Cross ventilation Buoyancy driven ventilation

Atrium ventilation

Chimney ventilation

Wind tower ventilation

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Air Water systems:

Fan coil systems

Induction unit systems

Chilled beam and displacement ventilation systems.

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District Cooling is a system in which chilled water is distributed inpipes from a central cooling plant to buildings for space cooling andprocess cooling.

It contain three major elements: the cooling source, distributionsystem and customer installations.

Cooling sources: Vapor, compression chillers, absorption chillers.

Distribution system: Chilled water pumps and buried pipingnetwork

Customer installation: Tie-in connection Energy Transfer Station(ETS) ie. Heat Exchanger connected with secondary pumps fordistribution of chilled water to fan coil units & AHUs.

Conventional chilled water supply temperature: Between 4C - 5C(in the U.A.E).

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Other advantages are as follows:- Environment-friendly

The plant design and equipment selection utilize an innovativetechnology with minimal impact on the environment.

Lower carbon foot print

Promotes healthier living

The system helps to create a working environment that is safer and

healthier for people.

Uses energy more efficiently

It maximizes efficiency and minimizes wastage.

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1.0 TECHNICAL: Understanding the technology and different approaches

DC with all electric chillers or mixed

DC with chilled water TES or DC with Ice TES

Heat rejection based on

- Fresh water

- Sea water

- polished Treated Sewage Effluent (TSE)

- Desalinated water

- Direct TES water with chemical treatment

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Understanding the Project:- Plot areas

- Land use & building classification

- Population & growth

- Development phasing

- Building codes & permits- Environmental regulations

- Cooling demand estimates sq. mts per ton

- Utility plots & areas

- Piping network corridors

- Access to nearest Power, Water & Sewage source- Geological site investigations & site instructions

- Other utilities inter-phasing etc.

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2.0 FINANCIAL Understanding the different Business Models

- Design, Bid, Build

- Joint venture / SPV (special purpose vehicle )

- Build Own Operate (BOT)

- Build Own Operate Transfer (BOOT)

- Engineer, Procure, Construct (EPC)

- O & M

Project costs & Financial analysis including budgeting:

- CAPEX costs

- OPEX costs

- Tariff structures- Revenues streams, cash flows & expenditures

- Profit & loss

- ROI (rate of investment return )

- IRR ( internal rate of return )

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Business Plan- Business Growth

- Market analysis

- Sensitivity analysis

- Critical issues & strategic analysis

- Strengths, weakness, opportunities, threats (SWOT)- Risk analysis, risk management, and risk mitigation

- Major challenges

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Capital costs(Capex)

Impact on cost Redundancy

Thermal Storage

Capital Cost per ton

Distribution System Connection

Overall

Energy Usage

Water Consumption

Overall

Diversity Factor

Opex costs Maintenance


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CapexOpex

CapitalIntensive

Attractive toStrong PredictableCash Flows

Typical Returns

Attractive to

Project IRREquity IRR

10 15 %15 20 %

LendersInvestors

DebtEquity


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Time Assessment Availability of Bulk Electrical Power Supply to the development and

the time constrains to build H.V Power substations / Local AuthorityPower Supply.

Infrastructure piping network construction.

TES (Treated effluent sewage) Water supply to development

Local Authority Building Permit

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Risk Assessment Lower than projected load

Lower energy sales / revenue generation

Reduced building occupancies

Timely permits from Utility companies for Power and Water Weather variations

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A. Mechanical1. Centrifugal Chillers

2. Condenser water Pumps

3. Chilled Water Primary Pumps

4. Chilled Water Secondary Pumps

5. Cooling Towers

6. Make up water pumps for Cooling Towers

7. Chemical Dosing system for Cooling Towers

8. Chemical Dosing system for chilled water network

9. R.O Plant for blow down water re-claim

10. Water Storage Tank for Cooling Towers / Fire Pumps11. Blow Down Storage Tank

12. Thermal Storage Tanks

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B. Electrical1. 11 kV Switchgear (3.3 kV if applicable)

2. 11kV Capacitor banks

3. 11 kV / 400 Ton Transformers (11 kV / 3.3 kV Transformers if

applicable)4. H.V Cables and containment systems

5. UPS / Battery Charger for 11 kV vacuum circuit breakers

6. L.V Switchgear

7. Motor control centres

8. L.V capacitor banks

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C. Control Systems1. Building Management System (BMS) or CMS (Plant Control

Management System).

2. PLC System for data control

3. System Data server4. Operator work stations

5. Energy work station

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Types of BTU Meters:A. Electromechanical meters

B. Magnetic meters

C. Ultrasonic meters

Communication modes for data collection:1. Data bus cables

2. Fiber Optic Cable

3. Radio Receiver / GSM

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System Components:A. Electromechanical Meters

i. Concentrator (Collect readings from meters)

ii. Data converter port

iii. M-Bus

iv. Fiber Optic Cable

v. GSM unit

vi. Server (collects readings from GSM)

B. Wireless Meters

i. Concentrator

ii. Radio receiver (collect data from a group of building)

iii. GSMiv. Server

v. Work Station

vi. ERP System for billing (Enterprise resource planning system)

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Typical District Cooling Plant Building

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Cooling Tower Cooling Tower Fan & Motor

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Typical Thermal Storage Tank Thermal Storage Tank

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Air Cooled Chiller Water Cooled Chiller Module

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Fan Coil Unit AHU Unit

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Control System SCADA System Projector Screen

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Destrict Cooling Presentation

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