Chilled Water Loop Optimization. Kazimir Gasljevic Richard Dewey Sandro Sanchez

Transcription

1 Chilled Water Loop Optimization Kazimir Gasljevic Richard Dewey Sandro Sanchez

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4 WHAT WE STARTED WITH: LOOP OUTLINE:

5 WHAT WE STARTED WITH: LOOP OUTLINE: - Justification for the loop

6 WHAT WE STARTED WITH: LOOP OUTLINE: - Justification for the loop Value of the loop piping, $10 Million Vs. Value of the chillers on the loop, $5 Million

7 WHAT WE STARTED WITH: LOOP OUTLINE: - The game changed after the introduction of variable speed chillers

8 WHAT WE STARTED WITH: LOOP OUTLINE: - The game changed after the introduction of variable speed chillers There will probably be no further expansion of the loop.

9 WHAT WE STARTED WITH: LOOP OUTLINE: - The game changed after the introduction of variable speed chillers There will probably be no further expansion of the loop. Modular variable speed chillers are the better way to go in our climate.

10 WHAT WE STARTED WITH: ORIGINAL CONTROLS CONCEPT:

11 WHAT WE STARTED WITH: ORIGINAL CONTROLS CONCEPT: Focused mostly on functionality with not much concern given to efficiency issues.

12 WHAT WE STARTED WITH: OVERALL LOOP ENERGY EFFICIENCY:

13 WHAT WE STARTED WITH: OVERALL LOOP ENERGY EFFICIENCY: 0.85 kw/ton, 0.8 kw/ton after installation of the variable speed chiller.

14 SCOPE OF THE MBCx PROJECT:

15 SCOPE OF THE MBCx PROJECT: An MBCx project focused on improving existing hardware with better usage and controls (no capital costs).

16 SCOPE OF THE MBCx PROJECT: FUNCTIONALITY:

17 SCOPE OF THE MBCx PROJECT: FUNCTIONALITY: To automatically maintain a constant Differential Pressure, as well as staging the chillers off and on smoothly.

18 SCOPE OF THE MBCx PROJECT: ENERGY EFFICIENCY:

19 SCOPE OF THE MBCx PROJECT: ENERGY EFFICIENCY: Improve the efficiency of all chiller plants.

20 SCOPE OF THE MBCx PROJECT: EXTRAS:

21 SCOPE OF THE MBCx PROJECT: EXTRAS: Critical cooling Use loop thermal capacity for load shedding Leak detection and leak location.

22 STRATEGY:

23 STRATEGY: Hiring Consultants vs. Doing the work in House:

24 STRATEGY: Hiring Consultants vs. Doing the work in House: "Fits all" algorithm vs. "algorithm for a given situation Intimate Knowledge of the plant

25 STRATEGY: OTIMIZATION METHODOLOGY:

26 STRATEGY: OTIMIZATION METHODOLOGY: Sacrifice slightly on the ideal mathematical optimum for a robust sustainable system. Take in to account temporal changes in the performance of the system components.

27 OPTIMIZATION ALGORITHM :

28 OPTIMIZATION ALGORITHM : Optimization of the Loop

29 OPTIMIZATION ALGORITHM : Optimization of the Loop Decide which chillers to run based on the capacity and efficiency of individual chillers.

30 OPTIMIZATION ALGORITHM : Optimization of the Loop Decide which chillers to run based on the capacity and efficiency of individual chillers. Decide the Condenser Water temperature set point.

31 OPTIMIZATION ALGORITHM : Optimization of the Loop Decide which chillers to run based on the capacity and efficiency of individual chillers. Decide the Condenser Water temperature set point. Decide the Differential Pressure set point (constant for now).

32 OPTIMIZATION ALGORITHM : Optimization of the Loop Decide which chillers to run based on the capacity and efficiency of individual chillers. Decide the Condenser Water temperature set point. Decide the Differential Pressure set point (constant for now). Consider a needed cooling capacity of the loop in the immediate future (few hours), based on the time of day and the weather forecast.

33 Efficiency [kw/ton] 1.2 Chiller Efficiencies at 74 F Condenser Temp and 42 F Supply Temp 1 ESB 0.8 CNSI Bren 0.6 Library Chemistry, Broida 0.4 ENG 1 BIO Load [tons]

34 Efficiency [kw/ton] 1.6 Plant efficiencies at WB 60 F ESB CNSI 1 Bren Library Chemistry ENG BIO Broida Load [tons}

35 OPTIMIZATION ALGORITHM : Optimization of individual chillers

36 OPTIMIZATION ALGORITHM : Optimization of individual chillers Balancing power for compressor, cooling tower fan, condenser pump. Use performance curves updated for the momentary changes (maintenance issues etc.)

37 Temperature [F] Delivered Chiller Loading ESB Chiller Temperatures Evaporator Condenser Pump Condenser Refrigerant Cooling Tower Condenser Water Supply Air Wet Bulb 50 Condenser Water Return Condenser Evaporator Water Return Evaporator Water Supply Evaporator Refrigerant Time [Minutes]

38 Approach = Tsat -T chw [F] ESB Condenser Problem, 8/26/ Before Cleaning 6 5 After First Cleaning After Second Cleaning 1 Ideal Tons

39 Approach Temp [F] F WB, 100% load 55 WB, 75% Load 70 F WB, 100% Load Broida Cooling Tower Performance (BAC model) 100% Load = 8.2 kw/f 50% Load = 4.2 kw / F 1 HP = 0.84 kw (0.9 motor efficiency) 20 70F WB, 75% Load 55 F WB, 50% Load F WB, 50% Load % speed 70% speed 80% speed 90% speed 100% speed Fan power (both) [HP] 100% 4.3 F 3.33 F 3 F 2.4 F 1.8 F 1.2 F 0.6 F 75% 6.45 F 5 F 4.5 F 3.6 F 2.7 F 1.8 F 0.9 F 50% 8.6 F 6.66 F 6 F 4.8 F 3.6 F 2.5 F 1.2 F How many F App T can be increased at any fan power saving before compressor power increase becomes larger than fan power reduction.

40 Approach Tem [F] Broida; Cooling Tower Approach Set Point , , WB 55 F y = -0.04x , WB 70 F 15 Linear (WB 55 F) Linear (WB 70 F) 50, , y = -0.03x , For a given % load: AT = (AT55WB - AT70WB) * (70 - WB) / 15 Add few F for a degraded cooling tower performance (determine experimentally) Chiller Load %

41 MEASUREMENTS:

42 MEASUREMENTS: Typically electrical power OK, tons not OK.

43 MEASUREMENTS: Typically electrical power OK, tons not OK. Uncertainty in a typical Btu measurement is in the range of improvements one is trying to achieve.

44 MEASUREMENTS: Typically electrical power OK, tons not OK. Uncertainty in a typical Btu measurement is in the range of improvements one is trying to achieve. Temperature measurements

45 MEASUREMENTS: Typically electrical power OK, tons not OK. Uncertainty in a typical Btu measurement is in the range of improvements one is trying to achieve. Temperature measurements Flow rate measurements.

46 MEASUREMENTS: Typically electrical power OK, tons not OK. Uncertainty in a typical Btu measurement is in the range of improvements one is trying to achieve. Temperature measurements Flow rate measurements. Improving measurements may amount to a third of the total effort.

47 CONCLUSIONS:

48 CONCLUSIONS: 0.63 kw/ton a yearly average compared with 0.8 kw/ton baseline.

49 CONCLUSIONS: 0.63 kw/ton a yearly average compared with 0.8 kw/ton baseline. With 11 bill tons annual cooling load, we used 8.8 mil kwh before and 6.93 kwh after.

50 CONCLUSIONS: 0.63 kw/ton a yearly average compared with 0.8 kw/ton baseline. With 11 bill tons annual cooling load, we used 8.8 mil kwh before and 6.93 kwh after. Annual savings 1.87 mill kwh = $225,000

51 CONCLUSIONS: 0.63 kw/ton a yearly average compared with 0.8 kw/ton baseline. With 11 bill tons annual cooling load, we used 8.8 mil kwh before and 6.93 kwh after. Annual savings 1.87 mill kwh = $225,000 Additional energy savings thanks to the improved functionality (maintaining a desired chilled water temperature and pressure differential).

52 Efficiency [kw/ton] Loop Efficiency September Measured: Average 0.64 kw/ton Baseline: 0.8 kw/ton Linear (Measured: Average 0.64 kw/ton) Time [h]

53 Efficiency [kw/ton] 1 Loop Efficiency June Measured: Average kw/ton 0.1 Baseline: 0.8 kw/ton Linear (Measured: Average kw/ton) Time [h]

54 CONCLUSIONS:

55 CONCLUSIONS: REMAINS TO BE DONE:

56 CONCLUSIONS: REMAINS TO BE DONE: What we have achieved is a near optimum and further improvements are to be done in both areas of control (optimize the loop and optimize individual chillers).

57 CONCLUSIONS: REMAINS TO BE DONE: What we have achieved is a near optimum and further improvements are to be done in both areas of control (optimize the loop and optimize individual chillers). About 70% of the expected total improvement in efficiency achieved, 30% remains to be done.

58 THANK YOU!