SOLAR ASSISTED COOLING GSD 6205: ENVIRONMENTAL TECHNOLOGY DEREK CHAN. MIRIAM ELRASSI. LIAN EOYANG. STEVE HUANG. MO LEE. DOUG WU

Transcription

1

2

3

4

5

6

7

8

9

10

11 IDEAL GAS LAW PV = nrt INVERSE RELATIONSHIP BETWEEN PRESSURE AND VOLUME: P=nRT/V WHEN PRESSURE IS INCREASED, VOLUME DECREASES DIRECT RELATIONSHIP BETWEEN PRESSURE AND TEMPERATURE: T=PV/nR WHEN PRESSURE IS INCREASED, TEMPERATURE RISES DIRECT RELATIONSHIP BETWEEN VOLUME AND TEMPERATURE: T=PV/nR WHEN VOLUME IS INCREASED, TEMPERATURE RISES

12 ISOTHERMAL AND ADIABATIC PROCESS ISOTHERMAL PROCESS: THERMODYNAMIC PROCESS WHERE T=0 ADIABATIC PROCESS: NO HEAT IS TRANSFERRED Q=0 ENTROPY: S= Q/T

13 ISOTHERMAL AND ADIABATIC PROCESS ISOTHERMAL PROCESS: THERMODYNAMIC PROCESS WHERE T=0 ADIABATIC PROCESS: NO HEAT IS TRANSFERRED Q=0 ENTROPY: S= Q/T INCREASE IN ENTROPY

14 PSYCHROMETRIC CHART PSYCHROMETRIC CHART T-x DIAGRAM

15 PSYCHROMETRIC CHART SATURATION LINE RELATIVE HUMIDITY LINE ISOTHERMAL LINE (CONSTANT ADIABATIC LINE (CONSTANT ENTROPY)

16 DIRECT EVAPORATIVE HOT, DRY FAN FILTER FILTER HUMIDIFIER FAN HOT, COOL, WET DRY COOL, WET

17 INDIRECT EVAPORATIVE COOL, WET HOT FAN HUMIDIFIER FILTER HEAT EXCHANGE FILTER FAN HOT COOL

18 DIRECT/INDIRECT EVAPORATIVE COOL, WET COOL, WET FAN HUMIDIFIER FILTER HEAT EXCHANGE FILTER FAN HOT COOL COOLER, WET

19 EVAPORATIVE + DESICCANT COOLING WARM, WET WARM, WET HOT, DRIER HOT, DRY WARM, WET HOT, DRY HOT HOT, DRY COLD COLDER, WETTER COLDER, WETTER

20 DESICCANT SYSTEM SUPPLY AIR OUTSIDE SUPPLY AIR RETURN AIR INSIDE RETURN AIR ADD HEAT TO INCREASE EFFICIENCY

21 DESICCANT SYSTEM

22 DESICCANTS SILICA GEL USED AS DESSICANT MATERIAL DESICCANT: INDUCES DRYNESS THROUGH THE ADSORPTION OR ABSORPTION OF WATER

23 Solar Collectors Heat Production Sub-System PV Cells Source:

24 Solar Collectors Heat Production Sub-System PV Cells Man Pushing PV Cells Source:

25 Solar Collectors Heat Production Sub-System PV Cells Man Pushing PV Cells Source:

26 Solar Collectors Heat Production Sub-System Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

27 Solar Collectors Heat Production Sub-System Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

28 Solar Collectors Heat Production Sub-System 1. Flat Plate Collector 2. Evacuated Tube 3. Stationary CPC 4. Solar Air Collectors Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

29 Solar Collectors Heat Production Sub-System 1. Flat Plate Collector 2. Evacuated Tube NO ELECTRICITY 3. Stationary CPC 4. Solar Air Collectors Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

30 Solar Collectors Heat Production Sub-System 1. Flat Plate Collector Requires selective coating (high absorptance of visible solar spectrum but low emissivity in the infrared range) Available in sizes 1.8m2 to 10m2 Installed on a tilt to face sun Only high quality flat-plate collectors with selective coating can be used because of necessary heat to drive system Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

31 Solar Collectors Heat Production Sub-System 2. Evacuated Tube Collectors Consists of single glass tubes evacuated of gases and attached to a header pipe Fluid channel flows within glass tube attached to an absorber Reflective surface can be mounted behind tubes to increase efficiency Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

32 Solar Collectors Heat Production Sub-System 3. Stationary CPC Collectors CPC = Compound Parabolic Concentrator Reflector concentrates solar radiation onto relatively small absorber surfaces Usually acceptance angles no less than 30 degrees so that system does not have to track sun movement Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

33 Solar Collectors Heat Production Sub-System 4. Solar Air Collectors Operates like liquid solar collectors but a mechanical fan pushes air through absorber PROS: No Freezing in Winter No Overheating in Summer Simple Fabrication of System No Water Leakage CONS: No Way to Store Heat Fan Consumes Elecricity Lower Heat Transfer Efficiency Than Fluids Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

34 Solar Collectors Heat Production Sub-System Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

35 Solar AC vs. Conventional AC* Performance comparison * Reference system (R) is a conventional, electrically driven compression chiller. Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

36 Solar AC vs. Conventional AC Economic assessment Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

37 Environmental Benefits - Replacing fossil fuels reduces CO2 emission. - Solar cooling uses water instead of ozone-depleting refrigerant (R-134).

38 Economics - Solar cooling generally saves a third of the electricity bill for air-conditioning. - Fossil fuel is still inexpensive. - High initial investment makes the system not yet cost efficient. Source:

39 Cost Break-down Desiccant_IHK system in Frieburg 210,000 Combination_SARANTIS cosmetics factory, Greece 1,400,000 Chilled-water circuit water circuit_office building in Guadeloupe 97,759 Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

40 Cost Comparison Frieburg Guadaloupe Greece Cooling load 5,000 m² 570 m² 22,000 m² Collector area 1,000 m² 154 m² 2,700 m² Cooling power Total installation cost 210,000 97,759 1,400,000 Cost per collector area 210 per m² 635 per m² 519 per m² Cost per cooling power 3,962 per kw 2,794 per kw 2,000 per kw Desiccant Chilled-water circuit Combination Source: Henning (Ed.), Solar-Assisted Air-Conditioning in Buildings, Vienna, 2007.

41 IHK DESICCANT COOLING SYSTEM IN FREIBURG, GERMANY Seminar and Cafeteria Room needed air-conditioning unit A system that could cool the large volume and crowded room was needed Seminar Room: 27.5 kw Cafeteria: 7.3 kw Total: 34.8 kw Desiccant cooling system most efficient in cooling large volume room Allow use of low-temperature heat to drive cooling process Could use standard solar collectors instead of special ones

42 Direct, indirect, and combined evaporative cooling of the supply air stream can be implemented. Fans equipped with frequency controllers adapt ventilation rate Cooling Power: Q = m supply (h amb h supply) Solar air collector installed Two arrays of 50 sqm fixed directly on roof One points at East, other at West

43 WINTER OPERATION

44 SUMMER OPERATION

45 MODEL DEVELOPED TO ANALYZE PERFORMANCE Assumed full crowd, 24/7 Each single point represents indoor temp vs. indoor humidity ratio per hour

46 Actual performance analysis between July 2001 to Jan 2002 System would save about 30% primary energy compared to traditional system 18,162 kwh vs 25,922 kwh

47 Total initial cost: 210,000 Euros 20.6 Euros per m3/h 3,961 Euros per kw of installed cooling power

48 SARANTIS COSMETICS FACTORY Inofita Viotias, Greece 1999

49 Located in an industrial zone ~ 50 km NE of Athens Facility operates 5 days / week Total air-conditioned area: 22,000 m 2 / 130,000 m 3 Peak cooling load: ~ 1,750 kw Local weather conditions: Daily mean global Season Mean outdoor temp. Rel. humidity horiz. radiation Summer 26 C 55% 6.64 kwh/m 2 day Winter 8 C 77% 2.35 kwh/m 2 day Average 17.4 C 66% 4.39 kwh/m 2 day Dehumidification a concern

50 Largest solar-cooling installation in Europe Fully automated system via off-site management Absorption vs. absorption ABSORBTION : An imbibing or reception by molecular or chemical action; as, the absorption of light, heat, electricity, etc. ADSORPTION : The accumulation of gases, liquids, or solutes on the surface of a solid or liquid. General system diagram Two Part System System 1 System 2 Type conventional solar assisted cooling Components 3 compression chillers 2,700 m 2 flat-plate solar collectors 2 adsorption chillers Cooling power / unit 350 kw 350 kw Total cooling power 1,050 kw 700 kw % of total cooling load 60% 40% (22,000 m 2 )

51 Solar Collector Array During summer, supplies hot water to to adsorption 120 m 3 /h Covers ~45% of cooling load, April - October During winter, supplies hot water directly to heated 55ºC Components: flatplate selective-absorber solar collectors (Climasol 350) Climasol 350 Total absorber array area: 2,700 m 2 Average solar collector efficiency: 67% Medium: water with no additives Small solar buffer tank (6 m 3 ) Flat-plate solar collector array Delivered cooling energy: 780,000 kwh/year Delivered heating energy: 900,000 kwh/year (winter only) Delivered gross energy: 2,200,000 kwh/year Maintained by design/installation team (SOLE S.A.) under subcontract to owner

52 Adsorption chillers Main cooling system in summer 350 kw each Require a lower supply temperature than the solar system (~70 12 m 3 /h) Annual average electricity consumption: 6,500 kwh/year Annual water consumption: 2,500 m 3 (average m 3 /day) Supplies chilled water (7ºC - 12ºC depending on 240 m 3 /h) to AHU Adsorption chillers Air-handling Units (AHU) Have been over-dimensioned to facilitate relatively high chilledwater supply temp. Total air supply flowrate to building: 325,000 m 3 /h Supply air temperature: 22ºC - 50% relative humidity Chilled water storage: 60 m 3 Compression chillers Used as a back-up cooling system in summer 350 kw each Oil-fired boilers Used as a back-up heating system in winter 1,200 kw each Back-up heating system

53 Office Building Basse Terre, Guadeloupe

54 Was used as a model project Design focused on simplicity, reliability & safety Must be cooled throughout entire year Solar energy available throughout year Facility operates 5 days / week, 7am - 5pm Total floor area: 1000 m 2 Total air-conditioned area: 570 m 2 (36 office rooms) Local weather conditions:

55 Cold distribution network chilled water circuit 1. Solar collector tubes evacuate hot water from solar collectors to absorption chiller 2. Absorption chiller (30 kw) pre-cools the chilled water loop to 7ºC - 12ºC 3. On next collector evaporation, water from absorption chiller is driven into a waterbased open cooling tower Back-up system: Vapor compression chiller (55 kw) w/ air cooled condenser Provides additional chilled water to the cold distribution network If this system acted alone (without vapor chiller), it would need to be 90 kw

56 Heat supply specifications: Required temperature range: 85ºC - 95ºC Cooling output: 30 kw Average COP: 0.70 Input needed for generator: 42.8 kw Reference solar energy supply: 700 W/m 2 Solar collector area neede: 61.2 m 2 Heat distribution network 1. Solar collector tubes evacuate hot water from solar collectors to buffer tank (>100L) 2. Some water travels to absorption chiller (30 kw), the rest travels directly to compression chiller System is not equipped w/ full-size hot-water storage tank no possibility to store heat for long periods Instead, collectors work in w/ absorption chiller Cooling output (30 kw) designed to always be slightly less than cooling load during sunny periods absorbtion chiller can operate directly with sun, and cooling is provided by solar collectors. 3. When load is higher, the vapor compression chiller is used as back-up