Solar cooling in the UAE The study takes into account a modular solar field with 4 PTM-24

Purely indicative information. Soltigua does not guarantee its accuracy

•

parabolic collectors. More modules can be combined into a bigger solar field to meet requirements in terms of capacity, load profile and according to available space.

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Location: Dubai

•

Coordinates: 27°38’N; 38°16’ S

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Solar field: 40 PTM-24 collectors

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Net collecting surface = 2160 sqm

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Required surface = approx 4.800 sqm

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Peak thermal capacity installed = 1.165 kWth (ref. Conditions: DNI = 900 W/sqm; Tfluid = 185°C; Tamb =30°C)

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Chiller COP = 1.4

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Peak air conditioning capacity = 26 RT (92 kW) © Soltigua 2011 – All rights reserved

• High temperature parabolic collectors make it possible to use double effect absorption chillers, whose performance is twice the one of single effect chillers which are driven by low temperature collectors (1.42 vs 0.7)

For a given cooling requirement: • A smaller collector field is required • Water consumption in the cooling tower is reduced by 27% © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

High temperature solar cooling

Low Temperature

High Temperature

Evacuated tube collectors+ single effect absorption chiller

Parabolic troughs + double effect absorption chiller

Collectors Efficiency

0.6

0.5

Chiller Efficiency (COP)

0.75

1.42

Total System Performance

0.45

0.71

Peak performance per net sqm installed

+57%

Up to 57% increase in Cooling Yield per square meter of collecting surface installed © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

Solar Cooling Ratio

Water Consumption Heat Provided (solar) = 1/COP =1/0.75 = 1.33 kW

Heat Rejected (cooling tower) = Heat Provided + Heat Extracted = 1+1/COP =

1-effect Chiller

Heat Provided (solar) = 1/COP =1/1.42 = 0.70 kW

2-effect Chiller

High Temperature

Heat Rejected ( cooling tower) = Heat Provided + Heat Extracted = 1+1/COP =

1.7 kW/kWcooling

2.33 kW/kWcooling Heat Extracted (cooling) = 1 kW

Heat Extracted (cooling) = 1 kW

27% water savings in the cooling tower (+lower electricity consumption) © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

Low Temperature

Solar circuit (thermal oil) Secondary circuit (pressurized water)

Cooling Tower

Chiller (Back up option 2)

Air conditioning distribution system

Hot Storage

Integrated auxiliary energy source (Back up option 1)

Solar field

Double effect absorption chiller

Can be integrated with traditional systems © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

System layout

Daily sum of DNI [kWh/mq]

10 8 6 4 2 0 0

50

100

150 200 n. of day in the year

250

300

350

Autumn / Winter − higher variation (sunny days vs. non sunny days); − drier atmosphere make solar radiation more intense during sunny days; Summer − less variation (almost all sunny days); −More haze in atmosphere. © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

Solar data analysis

Solar data analysis- cont’d Purely indicative information. Soltigua does not guarantee its accuracy

• A detailed analysis of the solar radiation trhoughout the year highlights great variation due to many different aspects (solar position in the sky, haze, sand storm, clouds,…) • Considering Dubai specific conditions, it is advisable to size the system according to its “typical” sunny day conditions (design conditions), with an incoming direct radiation of 650 W/sqm • Design Conditions: – – – – – – – – –

ANI=Incident Radiation =650 W/sqm (North-South alignment) Collector efficiency (Tinlet = 175°C; Toutlet =195°C) = 55% Collector output = 358 W/sqm Solar field net collecting surface = 2’160 sqm Solar field output = 777 kW Solar field thermal losses (estimated) =5% Solar field net thermal input to chiller = 738 kW Chiller COP = 1.4 Chiller output = 1’033 kWcold =295 RT (≥90%*320RT = 288 RT)

© Soltigua 2011 – All rights reserved

1200 1000

kW

800 600 400 200 0 Auxiliary 1 Source 3 [kW] 5

7

9

11

13

15

17

19

21

23

• In the simulation, solar energy can deliver all load from 9 to 15 • In order to cover the 24 hrs load a bigger solar field would be required with a big thermal storage © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

Sunny day

1400 1200 1000 800 600 400 200 0 1

4

Cooling Load [kW]

7

10 Auxiliary Source [kW]

13

16 Solar cooling [kW]

19

22 Solar cooling [kW]

• in a less sunny day some contribution is obtained as well, however the back-up is required to maintain the desired conditions in the building © Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

kW

Less sunny day

• Highly efficiency double effect solar cooling will provide highest output per sqm of solar collectors and lowest water consumption per RT • The system could work up more than 3000 hrs/yr at an average output of 160 RT • This will generate great savings on the electricity bill, reducing grid load especially during daytime hours.

© Soltigua 2011 – All rights reserved

Purely indicative information. Soltigua does not guarantee its accuracy

Conclusion