Tubman African American Museum. Christopher Champagne Mechanical Option 2003 Senior Thesis

Transcription

1 Tubman African American Museum 2003 Senior Thesis

2 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

3 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

4 Presentation Goals Investigation of the air-cooled water chillers: Museums have low load profiles during the evenings when only the exhibit spaces or anywhere artwork is stored needs to be cooled. A smaller chiller for off-hours cooling and a larger one for occupied mode. Staging of the chillers to see if an energy savings could be realized. Investigation of switching from constant speed pumping to variable speed pumping: Advantages of primary-only, variable speed pumping. Possibility of switching the chilled water pumps in this case. Should the switch be made? Investigation of current lighting system in gallery space

5 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

6 Existing Conditions Location: Atlanta, GA Use: Museum Size: 45,000 ft 2 Two stories Construction Started: October 2001 Planned Completion: Spring 2004 Construction Cost: $15.5 million

7 Design Team Architect CM/GC M/E/P Structural Exhibit Designer E. Verner Johnson and Associates, Inc. Harmon-Piedmont Construction, LLC Vanderweil Engineers Souza, True and Partners, Inc. The PRD Group, Ltd

8 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

9 Existing Mechanical System (2) ton HCFC-22 air-cooled water chillers (3) 290 GPM chilled water pumps (2) 25,000 CFM constant volume and (1) 18,000 CFM variable volume custom air handling unit.

10 Chilled Water Equipment (2) Trane Air-Cooled Water Chillers tons 290 GPM EWT = 55 F LWT = 45 F HCFC-22 Refrigerant Screw compressor (3) Bell & Gossett ½ BB Pumps 290 GPM 65 ft. head 1750 RPM 10.0 motor HP (1) Pump Standby

11 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

12 Chiller Optimization Technique The maximum cooling load is tons on July 15th at 2 pm using Atlanta Bin Data and Carrier s Hourly Analysis Program (HAP). Engineering Equation Solver (EES) was used to simulate two equal size air-cooled chillers 1. Trane Air-Cooled Series R Rotary Liquid Chillers Model RTAA 125 (Design Capacity = ton) 2. Trane RTAA 110 (Design Capacity = ton) 3. Trane RTAA 100 (Design Capacity = ton). Upper capacity that one chiller would run before the second chiller was run was varied from 85% to 100% of capacity to see which is the most efficient. The lower capacity at which the second chiller would turn off was set to 40%.

13 Chiller Optimization Equations The optimization equations used in the EES simulation are from the California Energy Commission s 2001 Non-Residential Alternative Calculation Methods (ACMs) document, specifically Chapter 2 entitled Reference Method and Required Modeling Capabilities for Alternative Calculation Methods (ACMs). The following three terms are functions of chilled water supply temperature (T chws ) and the outdoor dry-bulb temperature (T oa ). They are used to establish the efficiency of the chiller operation. CAP_FT is the full load capacity as a fraction of rated capacity. It is a capacity correction that is a function of those terms. EIR_FT is the full load efficiency (kw/ton) as fraction of rated capacity. It is an efficiency correction factor. EIR_FPLR is the fraction of full load power as a function of fraction of full load output.

14 EES Model Cases Case Model Ton kw Lower Upper Cap. (%) Cap. (%) A B C D E F G H I J K L

15 Electrical Utility Rates The electricity would be provided by Georgia Power (a subsidiary of Southern Company). PLM-3 rate which is for small to medium building size. Not less than 30 kw but less than 500 kw. Base Charge (includes first 25 kwh or less $14.00 All consumption (kwh) not greater than 200 hours 200 hours times the billing demand. First 3,000 kwh Next 7,000 kwh Next 190,000 kwh per kwh per kwh per kwh

16 Annual Operating Cost and Time Case AEC Operating Cost Operating Time Cost Operating Time (kwh) ($) (hrs) Rankings Rankings A 1,033,188 88,572 13, B 1,043,601 89,291 14, C 1,038,866 88,964 15, D 1,096,997 92,981 14, E 1,108,762 93,794 14, F 1,104,441 93,495 15, G 977,400 84,717 13, H 985,828 85,299 13, I 1,038,866 88,964 14, J 927,718 81,284 12, K 934,654 81,763 13, L 929,304 81,393 14,

17 Annual Operating Cost Annual Energy Cost 95,000 90,000 Cost ($) 85,000 80,000 75,000 A B C D E 1F G H I J K L

18 Life Cycle Cost of Chillers The following formula from CoolTools was used in the calculation of the LCC. Where: FC = first cost of plant UCj = plant utility cost for year j MCj = relative maintenance cost for year j d = discount rate N = number of years of analysis MCj = $500 d = 12 % N = 20 LCC = FC + N ( UC j + MC j ) ( 1+ d ) j= 1 Case A B C j ( ) Model Ton First Cost (FC) $96,000 $84,000 $75,000

19 Life Cycle Cost of Chillers LCC of Different Size Chillers Trane Model Number RTAA 100 RTAA 110 RTAA 125 $686, $698, $706, , , , , , , Cost ($)

20 Chiller Optimization Recommendation The RTAA 100 has the smallest life cycle cost based on the assumptions stated above. However given its tonnage being only slightly above the design cooling load, this might not be a wise selection. The RTAA 110 would still provide cost savings over the RTAA 125 (LCC savings = $10,422.14), along with some added safety to the designer. The staging should be set to 100% of capacity of the first chiller before the second chiller is turned on.

21 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

22 Chilled Water Pumping One method of saving energy used by a building is changing the primary pumps of a primary-only, chilled water system from constant speed to variable speed. Important Considerations: Does the chilled water system meets the requirements for being switched from constant speed to variable speed pumps? What is the overall economic benefit along with benefits that are not quantifiable?

23 Advantages of Variable Speed Pumps Improved efficiency (motor and pump) and consequently energy savings. Reduced system noise. Improved control of system flow to respond to flow and pressure requirements of the system. Extended motor life due to soft stops & starts which puts less wear and tear on the parts of the pump. Lower installation cost. The control valve in the bypass ensures that neither of the chillers would become starved during a low load situation, as flow is diverted directly from the supply back to the chillers.

24 Possibility of Switching Pumps Trane mentions four situations where variable primary flow should not be used (Trane, 1999). They are for system where: System chilled-water temperature is critical. Examples are a clean room or computer chip making plants. Although there are specific temperature and humidity guidelines for a museum, they are not critical. Slight temporary fluctuations will not cause permanent damage to the artifacts. The system flow rate, and consequently the load, does not vary. The load does vary in the Tubman Museum, between the occupied hours and the unoccupied hours. Also, due to the large transient load of occupants, the location of the load varies frequently within the inside of the building during the occupied hours. It is unlikely that the owner/operator will run the plant as designed. This is a slight area of concern, but something that doesn t eliminate the use of variable speed pumps for the system. Existing chiller controls are old and inaccurate. This is a new construction project, so this also is not a concern.

25 Current Piping Schematic BEFORE CHILLER: EWT = 55 F 290 GPM BEFORE CHILLER: EWT = 55 F 290 GPM CHILLER 1 (CH-1): CAPACITY = TONS HCFC-22 REFRIGERANT (2) SCREW COMPRESSORS (10) CONDENSER FANS 1.0 HP EACH 850 RPM AMBIENT MAX = 95 F AMBIENT MIN = 23 F CHILLER 2 (CH-2): CAPACITY = TONS HCFC-22 REFRIGERANT (2) SCREW COMPRESSORS (10) CONDENSER FANS 1.0 HP EACH 850 RPM AMBIENT MAX = 95 F AMBIENT MIN = 23 F AFTER CHILLER: LWT = 45 F 290 GPM CHWR AFTER CHILLER: LWT = 45 F 290 GPM CHWS AHU-1A&1B (LOAD) CHWS AHU-2 (LOAD) FOR ALL PUMPS: 290 GPM WATER TEMP. = 55 F NPSHR = 8.4 FT HEAD = 65 FT PUMP RPM = 1750 BHP = 7.25 MOTOR HP = 10 SHOT CHEMICAL FEEDER AIR SEPARATOR PRESSURE RELIEF VALVE CHWR CSPUMP (P-6): (STAND BY) CS PUMP (P-3): EXPANSION TANK LEGEND: BALL VALVE BUTTERFLY VALVE BUTTERFLY VALVE WITH MEMORY STOP (BALANCING VALVE) CHECK VALVE STRAINER W/BALL VALVE, HOSE BIBB & CAP AUTOMATIC CONTROL VALVE, MODULATING ACTUATOR COMBINATION FLOWMETER/SHUT OFF/BALANCING VALVE (CIRCUIT SETTER) CS PUMP (P-4): UNION OR FLANGE

26 Proposed Piping Schematic BEFORE CHILLER: EWT = 55 F 290 GPM BEFORE CHILLER: EWT = 55 F 290 GPM CHILLER 2 (CH-2): CAPACITY = TONS HCFC-22 REFRIGERANT (2) SCREW COMPRESSORS (10) CONDENSER FANS 1.0 HP EACH 850 RPM AMBIENT MAX = 95 F AMBIENT MIN = 23 F CHILLER 2 (CH-2): CAPACITY = TONS HCFC-22 REFRIGERANT (2) SCREW COMPRESSORS (10) CONDENSER FANS 1.0 HP EACH 850 RPM AMBIENT MAX = 95 F AMBIENT MIN = 23 F AFTER CHILLER: LWT = 45 F 290 GPM CHWR AFTER CHILLER: LWT = 45 F 290 GPM CHWS AHU-1A&1B (LOAD) CHWS AHU-2 (LOAD) FOR ALL PUMPS: 290 GPM WATER TEMP. = 55 F NPSHR = 8.4 FT HEAD = 65 FT SHOT CHEMICAL FEEDER AIR SEPARATOR PRESSURE RELIEF VALVE CHWR VSPUMP (P-6): (STAND BY) VS PUMP (P-3): EXPANSION TANK LEGEND: BALL VALVE BUTTERFLY VALVE BUTTERFLY VALVE WITH MEMORY STOP (BALANCING VALVE) CHECK VALVE STRAINER W/BALL VALVE, HOSE BIBB & CAP AUTOMATIC CONTROL VALVE, MODULATING ACTUATOR COMBINATION FLOWMETER/SHUT OFF/BALANCING VALVE (CIRCUIT SETTER) VS PUMP (P-4): UNION OR FLANGE

27 Chilled Water Bypass Control Normally closed control valve. Permits the operation of a single chiller below its low flow limit. Programmed to maintain only the minimum flow for each chiller that is on as opposed to constant flow, which would waste energy. Located near to the chillers so that the pressure drop throughout the system can drop as the coil loads drop.

28 Additional Costs Savings: The three-way valves are replaced with two-way valves at the AHU s. Less piping needs to be around the load with the elimination of the three-way valves. Steel schedule 40 piping, which costs $97 per linear foot for 6 piping for 100 feet of piping, meaning a savings of $9,700. Costs: A control valve in the bypass has to be added in the bypass line, which would typically cost $1950. Three variable frequency drives must be purchased each costing $5,800. Additional cost = $9,650.

29 Cost Savings Energy There are several different techniques available for calculating the energy savings (kwh) for variable speed pumps. Carrier s Hourly Analysis Program (HAP) Bell & Gossett ESP-Plus Online Program Engineering Equation Solver (EES) The results from EES will be presented further.

30 Engineering Equations Solver (EES) The following terms were created using lookup tables: Flow Rate vs. Head Flow Rate vs. Pump Efficiency Percent of Nameplate Load vs. Motor Efficiency Percent of Design Speed vs. Drive Efficiency (for the Variable speed pumps only) Individual functions were created for: Total Power Pump Efficiency Pump Model Curve Percent of Nameplate Load Deciding Number of Pumps Operating Based on the Load Speed the Variable Speed Pumps Operate At

31 Engineering Equations Solver (EES)

32 Engineering Equations Solver (EES)

33 Life Cycle Cost of Pumps The following formula from CoolTools was used in the calculation of the LCC. LCC = FC + j ( ) N ( UC j + MC j ) ( 1+ d ) j= 1 Where: FC = first cost of equipment UCj = utility cost for year j MCj = relative maintenance cost for year j d = discount rate N = number of years of analysis In this example: FCconstant = $0 FCvariable = $9,650 MCj = $500 d = 12% N = 20 years UCj constant speed = $4,092 UCj variable speed = $2,369

34 Payback Period of Pumps Initial Additional Cost for Variable Speed Pumps = $9,650 Yearly Savings = $1, Payback Period = $9,650 / $1, = 5.6 years

35 Chilled Water Pumping Conclusion Based solely on cost, it makes sense to switch from constant speed pumps to variable-speed pumps. The LLC is $3, less for variable speed. The payback period is slightly lengthy, but realistic.

36 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

37 Lighting of Gallery Space The lighting system for a gallery space in the museum (Collection Gallery 255) was designed using industry guidelines. The IESNA Lighting Handbook Ninth Edition (2000)

38 Placement of Luminaries X = (Ceiling height eye level) * = ( ) * = 66 = 5-6

39 Lightscape Renderings Southeast corner of room from above South of the room from above

40 Target Illuminance The IESNA Lighting Handbook target illuminance for: Flat displays and 3-dimensional objects is 300 lx (30 fc) Lobbies, general gallery areas and corridors is 100 lx (10 fc).

41 Photometric Data Southeast corner of room from above

42 Photometric Data South of the room from above

43 Lighting of Gallery Space Conclusion The new lighting design is compliant with the lighting requirements stated in the IESNA Lighting Handbook for illuminance. Artwork and artifacts are accentuated.

44 Presentation Outline Presentation Goals Existing Conditions Existing Mechanical System Chiller Optimization Chilled Water Pumping Lighting of Gallery Space Conclusions and Recommendations

45 Conclusions and Recommendations The RTAA 110 would still provide cost savings (LCC savings = $10,422.14) over the RTAA 125, along with some added safety to the designer and should be selected. The staging should be set to 100% of capacity of the first chiller before the second chiller is turned on. The primary-only, chilled water pumps should be switched from constant speed pumps to variable-speed pumps. The LCC is $3, less for variable speed. Variable speed control also has some advantages that are not quantifiable in economic terms. The new lighting design is compliant with the lighting requirements stated in the IESNA Lighting Handbook.

46 Acknowledgements I would like to thank the following people who have made my thesis possible: The Pennsylvania State University Department of Architectural Engineering faculty including: My advisor, Dr. James Freihaut Dr. William Bahnfleth and Dr. Stanley Mumma Jonathan Dougherty, Moses Ling, M. Kevin Parfitt and Kenneth Davidson Vanderweil Engineers, especially Heather Tsatsarones and Ron Edwards Fellow architectural engineering students who have lent their knowledge and expertise Mom, Dad and Jen who are always there for me My friends who have been understanding and helpful

47 Questions Thank you for your time Any questions???