ASHRAE Rocky Mountain Chapter. RickPhillips Phillips, P.E., PE LEED AP Senior Mechanical Engineer The RMH Group, Inc.

Transcription

1 ASHRAE Rocky Mountain Chapter Evaporative Cooling RickPhillips Phillips, P.E., PE LEED AP Senior Mechanical Engineer The RMH Group, Inc. April 19,

2 Fundamentals Dry Bulb Temperature Wet Bulb Temperature Evaporation Wet Bulb Depression = DB WB Design Day in Denver 93 DB, 59 WB 2

3 Direct Evaporative Cooler 3

4 Media 4

5 Performance Cooling Effectiveness = (%) EDB LDB EDB EWB 5

6 Indirect Evaporative Cooling 6

7 Hybrid Indirect Evaporative Cooler with Energy Recovery (Could be DEC) (Used as IEC) 7

8 Psychrometrics DIRECT INDIRECT INDIRECT / DIRECT 8

9 Direct Evaporative Cooling Pad Performance OA DB HOURS/ 4" PAD 8" PAD 12" PAD FINAL RM COND (74 DB) RANGE MCWB YEAR LAT (DB) LAT (DB) LAT (DB) (WB) (%RH) Binweather data, Denver, CO Doesn t include fan temperature rise 9

10 Indirect/Direct Evaporative Cooling System Performance OA DB HOURS/ INDIRECT INDIRECT 4" PAD 8" PAD 12" PAD FINAL RM COND (74 DB) RANGE MCWB YEAR LAT (DB) LAT (WB) LAT (DB) LAT (DB) LAT (DB) (WB) (%RH) Binweather data, Denver, CO Doesn t include fan temperature rise 10

11 Typical Meteorological Weather Data (TMY2) Hourly weather data for a typical year (not averaged) Includes typical extreme weather conditions Database includes conditions i like this: 78 F DB, 66 F WB Under these conditions, direct evaporative cooling does not perform well. 12 PAD (LAT) Final Room Conditions 67 F DB 74 F DB, 76% RH 11

12 Typical Meteorological Weather Data (TMY2) Number of hours/year with high WB > 60 F 378 hours > 63 F 146 hours 65 F 33 h > 65 F 33 hours Using a 63 F DAT requires 67% more airflowthan using 55 F DAT. 12

13 Systems that Can Use Higher SAT Displacement Ventilation 63 F 68 F UFAD Data Centers (hot aisle/cold aisle) 60 F 64 F 64 F 80 F 13

14 For Conventional VAV Applications Combine chilled water with direct evaporative cooling Advantages Can reduce chiller ton hours/year by 2/3 ($$). Can deliver 55 F DAT at any time. Don t have to oversize fans and ducts. Can limit humidity levels in the building. Note: still requires a full sized chiller 14

15 CHW/DEC Component Arrangement for Optimal Performance * Fan Upstream 35% less CC energy 15

16 For which types of buildings does evaporative cooling work? Direct evaporative cooling alone Warehouses Vehicle repair facilities Any type of building with low internal cooling loads Makeup air for commercial kitchens Gymnasiums Spaces that are open to the outdoors 16

17 For which types of buildings does evaporative cooling work? Indirect evaporative cooling combined with ihdirect evaporative cooling Commercial office buildings Retail spaces Recreation center Any type of building with moderate to low internal cooling loads Direct and/or indirect evaporative cooling combined with CHW or DX cooling Any type of building 17

18 Pros Saves energy Works well in the Denver climate Low tech and easy to maintain with unskilled labor Lower cost than a chilled water cooling plant Can also be used to cheaply humidify air Direct evaporative cooling is inexpensive 18

19 Cons Ifnot maintained properly, can produce odors If wrong materials are used, can have corrosion problems Poor construction can result in leaks and water carryover, resulting in flooding of the space below the unit People don t understand how to maintain it or fix problems 19

20 Maintenance and Operation Dry the pad out daily. Drain the sump weekly. Run the pad wild. Don t recirculate air. Pads last approx years. Pipe for maintenance (strainers, PRV, flowmeters, etc.). 20

21 Direct Evaporative Cooler Piping 21

22 Water Treatment Scale buildup prevention Continuous bleed or automatic control Biocides 22

23 Control Sequence Economizer (OA) Direct evap first Indirect/direct (if used) Direct with chilled water High humidity lockout 100% outside air whenever direct evap is active 23

24 Myths Legionella disease Over humidification Smell High maintenance High water usage 24

25 Typical HVAC Systems Estimated Total Water Consumption Air Cooled Chiller 2.8 COP = 10 Lb. H 2 O Ton Hr DX Air Conditioner 2.8 COP = 10 Lb. H 2 O Ton Hr Water Cooled Chiller 5.55 COP = 25 Lb. H 2 O (150 ton 300 ton) Ton Hr Evaporative Cooler 80 o F O.A. = 21 Lb. H 2 O (Direct/Indirect) Ton Hr Assumptions Power plant overall efficiency of 35% Average O.A. temperature of 80 o F Cooling tower bleed rates of 20% to 33% 25

26 Case Study Golden Hill Office Center 212,000 sf office building constructed in 1983 Designed in conjunction with SERI (NREL) Model project for energy conscious design National ASHRAE First Place Energy Award for New Construction,

27 Case Study Golden Hill Office Center Features 100% indirect/direct evaporative cooling system Solar hot water heating Three 10 kw roof mounted photovoltaic arrays Passive solar design with east west axis Six high efficiency, condensing boilers Natural ventilation for parking garage Heat and light reclaimed fromatriums to offices South side window overhangs 38 kbtu/sk/year measured without atrium; DOE 1995 energy evaluation of comparative buildings is 90 kbtu/sf/year 43 kbtu/sf/year measured with atrium 28 kbtu/sf/year with light shelves (not installed) 27

28 Case Study Golden Hill Office Center Indirect/direct evaporative cooling process 28

29 Case Study CU Boulder ATLAS Center 66,000 sf of classroom, performance, and study space Opened for classes in August 2006 Features direct evap + CHW cooling, carbon dioxide monitoring, and VAV systems Certified LEED NC Gold 4 points for optimizing energy performance 30% reduction 29

30 Case Study CU Boulder Wolf Law Building Five story story, 184,000 sf Opened for classes in August 2006 Features direct/indirect evap + CHW cooling, carbon dioxide monitoring for demand ventilation, and VAV systems Certified LEED NC Gold 30

31 Case Study CSM Student Recrea on Center 110, sf facility Direct/indirect evaporative cooling only $500,000 deferred cost for chiller plant Natatorium IEC Outside air for humidity control Competition gymnasium DEC/IEC 31

32 Case Study Colorado Springs U li es Laboratory Project Description 45,000 sf (2/3 laboratory space, 1/3 office space) Direct evaporative cooling with ih chilled water, energy recovery Designed with the Labs 21/LEED Guidelines Certified LEED NC Silver 50% energy savings compared to base case USGBC CO Bldg. of the Year Award 32

33 Case Study Colorado Springs U li es Laboratory 2 AHUs 62,000 cfm for labs, 25,000 cfm for offices Annual chiller operating costs with chilled water cooling only $17,900 Annual chiller operating costs with combined chilled water/ evaporative cooling $5,900 33

34 Case Study Colorado Springs U li es Laboratory Cost of adding direct evaporative cooling modules Lab AHU Office AHU Equip. Cost $9,500 $6,000 Hookup/Controls $2,500 $2,000 Total $12,000 $8,000 Payback with addition of evaporative cooling = First Cost/ Yearly Savings = $20,000/ $12,000 = 1.67 years (20 months) 34