Best Practices in System Optimization and
Efficiency at UT Austin
Juan Ontiveros, P.E.
Executive Director of Utilities and Energy
Management
Introduction
•
•
•
Describe the Chilling Station System
Describe Chilling Station Performance
Explain the Relevance of Chilling Station
Performance In Austin, Texas to Doha
•
Compare a Hypothetical 100,000 Ton
Plant in Doha vs Austin
•
•
Use of VFD’s and Optimum Energy
Use of 7T and Termis for Chilled Water
Loop Management
2
UT's Chilled Water System
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•
•
45,000 tons of capacity
4 chilled water plants
11 electrical centrifugal chillers ranging from 3,000 tons to
5,000 tons
•
•
12 miles of chilled water loop piping
4 million gallon, 36,000 ton hour capacity thermal storage
tank (On-line 12/2010)
•
•
•
•
nearly 200 connected loads
over 200 loop valves
20 primary chilled water pumps
variable primary system
Chilled Water Distribution System
4
Operations at a Glance
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•
•
•
•
•
•
•
Peak Cooling Load – 35,000 Tons
Peak Chilled Water Flow – 70,000 gpm
Average Supply Temperature - 39°F
Average Return Temperature - 49°F
Average Supply Pressure at Plants – 100 psig
Peak Supply Pressure at Plants – 125 psig
Total Annual Cooling Produced 145,000,000 Ton-Hours
Total Annual Power Consumed by Chilling Plants – 108,000,000 kWh
5
Efficiency Gain
• 30 to 50% of total electric load is cooling
• Must pay attention to chilled water production efficiency
Chilled Water System Energy Requirements
1.5
1.4
1.3
KW/Ton
1.2
1.1
1
0.9
0.8
0.7
0.6
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
6
7
Chiller Details
VFD
5,000 Ton York OM Titan
8
4,160 Volt, Toshiba VFD
8
0.900
University of Texas at Austin - 5000 Ton Centrifugal Chiller
Performance with Varying ECWT
0.800
0.700
kW/Ton
85 F
0.600
75 F
0.500
65 F
0.400
55 F
0.300
0.200
2000
2500
3000
3500
4000
4500
5000
5500
Capacity (Tons)
9
0.900
University of Texas at Austin - 5000 Ton Centrifugal Chiller
VARIABLE Speed Performance with Varying ECWT
0.800
VARIABLE SPEED
0.700
kW/Ton
85 F
0.600
75 F
0.500
65 F
0.400
55 F
0.300
0.200
2000
2500
3000
3500
4000
4500
5000
5500
Capacity (Tons)
10
UT
Austin
JCI
Design
Approach
To Maximize
Optimum
Energy
Energy Savings
Tegron
11
Design Concept
•
•
All rotating equipment would have VSDs
No control valves to modulate flow through the
chiller evaporator or condenser
•
Control valves used only to modulate the three
(3) cooling tower cells
o
Balance the total flow evenly over all three cells
12
Control Strategy
Automatic Mode of Operation
• System determines component running order based on
runtime
• Operator determines flow & number of components to
run
• PLC balances flow across active tower cells
Manual Mode of Operation
• Operator determines component running order
• Operator determines flow & number of components to
run
Optimum Energy
• Determines optimal flows and needed components
13
Before Optimization
• Performance - 10 to 15% better than existing
stations
• At 85°F ECWT - 0.785 kW/Ton
• Chiller only - between 0.57 and 0.59 kW/Ton
14
Optimum Energy
System
Chilled water
temperature
reset
17% less
Chemical
Costs & 14%
less Water
Sustain key
loop
minimum
pressures
Operate
at the
lowest
kW/ton
Stay within
equipment
constraints
Reduce tower
water usage
and chemical
usage
15
Optimum Energy Nov 17, 2009
16
Jan, 2010 – 0.329 kW per Ton
17
LOAD IN TONS
35,000
Annual Chilled Water Profile
32,500
30,000
27,500
25,000
22,500
20,000
17,500
15,000
24%
12,500
10,000
7,500
36%
40%
5,000
2,500
0
500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000 9500
HOURS AT OR ABOVE LOAD
18
Doha-Austin Weather Data
WB ºF
110
100
90
DB-Doha
WB-Doha
DB-Austin
WB-Austin
80
70
60
50
40
30
19
UT Austin Chilling Station Performance
WB ºF
60
0.90
.73 kW/Ton Annual Average
55
0.80
50
0.70
45
0.60
40
0.50
35
0.40
30
WB-Austin
25
0.30
kW per Ton (Including Auxillaries)
20
Jan-09
Feb-09 Mar-09
Apr-09
May-09
Jun-09
Jul-09
Aug-09
Sep-09
Oct-09
Nov-09
0.20
Dec-09
20
UT Austin Chilling Station Performance
WB ºF
60
0.90
.73 kW/Ton Annual Average
55
0.80
50
0.70
45
0.60
40
0.50
35
0.40
30
WB-Austin
25
kW per Ton (Including Auxillaries)
0.30
kW per Ton (Prior Year)
20
Jan-09
Feb-09 Mar-09
Apr-09
May-09
Jun-09
Jul-09
Aug-09
Sep-09
Oct-09
Nov-09
0.20
Dec-09
21
Superimpose UT Austin’s kW/Ton
On Doha
Matched WB and corresponding kW/Ton
in Austin to our plant in being located in Doha
22
WB ºF
UT Austin kW/Ton Superimposed on Doha WB
90
80
0.90
.76 kW/Ton Average
0.80
70
0.70
60
0.60
50
0.50
40
0.40
30
0.30
WB-Doha
20
10
0
KW/Ton
0.20
0.10
-
23
Take our Plant Hourly Profile and Extrapolate
to a 100,000 ton plant
Compare this hypothetical plant performance in
Austin vs Doha assuming:
• No hydraulic constraints
• No Delta T issues
• Auxiliary plant equipment adequately sized
24
Hours per Year
1400
Austin – 100K Ton Plant
Total Plant Performance vs Wet Bulb
Hrs
kW/ton
1300
kW Per Ton
1.00
0.90
1200
0.80
1100
1000
900
0.60 kW/ton Weighted Average
0.70
0.60
800
700
0.50
600
0.40
500
400
0.30
300
0.20
200
0.10
100
0
0.00
79 77 75 73 71 69 67 65 63 61 59 57 55 53 51 49 47 45 43 41 39 37 35 33 31
Wet Bulb Temperature (ºF)
25
Hours per Year
1150
1100
1050
1000
950
900
850
800
750
700
650
600
550
500
450
400
350
300
250
200
150
100
50
0
89 87
Doha- 100K Ton Plant
Total Plant Performance vs Wet Bulb
kW Per Ton
1.20
Hrs
1.10
kW/ton
1.00
0.70 kW/ton Weighted Average
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
85
83
81
79
77
75
73
71
69
67
65
63
Wet Bulb Temperature (ºF)
61
59
57
55
53
51
49
Demonstrate Optimum Energy
27
Looking Ahead
Reduce
Chilled
Water Loop
Chilling Station
Energy Reduced
More than
Increased
Pumping Power in
Buildings
Pressure
Control Valves in
Buildings Cannot
Sustain High DP
Modulate Pump
Speed and Output
of New Chilling
Station to Maintain
Loop DP using
Optimum Energy
Decrease
Maintenance
Costs and
Frequency
Reduce Chilled
Water Rates
Improve Plant
Performance
and Reduce
Pumping Costs
28
Termis Screenshots
of Campus
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30
Supply Temps
Piping
31
Supply Temps
Consumer
32
Bottlenecks
Zoom
33
Valve Positions
34
Energy and CO2 Emissions Savings
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•
•
UT Consumes 145 million kWh for cooling for a 45,ooo Ton Plant
It would be about 322 million kWh if it were a 100,000 Ton Plant
If it were at .7 kW/Ton vs. 1 kW/Ton the savings are 97 million kWh
o
At 4 cents/kWh it would be $3.9 million/year savings
o
Also get Water, Chemical savings
o
Also get reduced wear and tear on equipment
o
Maintenance savings
35
Changing Utility Plant Mindset
Design the Plant for
Peak Conditions
#1
Same but Operate the Plant
for Average Load
#2
Install Digital Controls
& Metering
#2
Same but Install “Real Time”
Modeling & Monitoring
Feedback
#3
Train Operators to Keep
the “Car on the Road”
#3
Train Operators to See the
Whole System & Optimize
Conditions (savings culture)
#1
#4
Preventive & Reactive
Maintenance
#4
Use Whole System “Real Time”
Knowledge to Perform
Maintenance
#5
Calibration & Engineering
Oversight Minimal
#5
Calibration Mandatory
Engineering Oversight
Essential
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