Chilled Water System Optimization
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Transcript of Chilled Water System Optimization
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POWERFUL BUSINESSPOWERFUL BUSINESS““Facing a Dynamic Energy Future Facing a Dynamic Energy Future ””
CHILLED WATER SYSTEM CHILLED WATER SYSTEM OPTIMIZATONOPTIMIZATON
Presented by
David A. Rogers, P.EHarold A. Hougham, P.E.
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
ENGINEERING APPLIED TO OPERATIONS
(Retro Commissioning)
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THE CONCEPT
SYSTEM FUNDAMENTALS
THE PROCESS
THE RESULTS
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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THE CONCEPT
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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SYSTEM FUNDAMENTALS
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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THE THREE RULES FOR HYDRONIC SYSTEMS OPTIMIZATION
PUMP LESS WATER
PUMP LESS WATER
PUMP LESS WATER
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“Distribution System DELTA T
Drives the Plant (s)”
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SyllabusSystems ConceptsSimple FormulasRules of Thumb
System ConfigurationsHydraulic Profile
System ComponentsDelta T
Flow Limited PlantHow your System works – Now/Optimized
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Systems Concepts
A system is a group of components that when connected and operating
provide a desired result.
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Systems Concepts
ProductionProduction DistributionDistribution LoadLoad
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Systems Concepts
Chillers
LoadPumps
Pumps
Cooling Tower
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Systems ConceptsChilled Water System
Dec
oupl
er
Secondary Pumps
Load
Distribution System
Production System
Primary Pumps
Chillers
Data & Controls
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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Simple FormulasChilled Water Delta T = T return water - T supply water
GPM/TON = 24/Delta T
Pump Affinity Laws = Q1/Q2=N1/N2H1/H2=(Q1/Q2)2BHP1/BHP2=(Q1/Q2)3
Q = Flow, N = rpm, H = Head
BHP = Brake Horsepower
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Simple Formulas
Chilled Water Delta T = T return water – T supply waterChilled Water Delta T = 60 – 42 = 18 degrees.
CHWR T = 60oF
CHWS T = 42oF
Cooling Coil
Control ValveChilled Water Delta T
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Simple Formulas
How many tons of cooling are served by a 6,000 gpm/12 degree delta T distribution system?
GPM = 6,000
Delta T = 12 degrees
24/Delta T = 24/12 = 2 GPM/Ton
Tons Cooling = GPM/(24/Delta T) = 6,000/2 = 3,000 tons
HOW MANY CHILLERS DO I HAVE ON LINE TO SERVE THIS 3000 TON LOAD?
GPM/Ton = 24/Delta T
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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Simple Formulas
What is the approximate required pumping horsepower if I cut system flow in half while still serving the same cooling load?
10,000 GPM requires 240 BHP
5,000 GPM requires ? BHP.
Q1 = 10,000 GPM, Q2 = 5,000 GPM, BHP1 = 240
BHP2 = BHP1(Q2/Q1)3 or BHP2 = 240(5,000/10,000)3 = 240/8 ≈ 30 BHP
Pump Affinity LawsPump Affinity Laws can be used to estimate system performance
but should be modified to reflect system performance.
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Rules of Thumb•Water Always Flows from a Higher Pressure to a Lower Pressure.
•Minimum Delta P for a control valve = 5 psig
•Minimum Delta P for a Bldg Interface = 20 psig
•Distribution System Delta T should always be ≥ Production System Delta T
•Production System Delta T should always be < Chiller Delta T
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Rules of ThumbMinimum Delta P Across a Control Valve is 5 psig
WHAT HAPPENS IF DELTA P IS ZERO?
Delta P = 18 – 11 = 7 psig
Cooling Coil
Control Valve
P3= 11 psig P1= 18 psig
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Rules of ThumbMinimum Delta P Across a Building Interface is 20 psig
WHAT HAPPENS IF DELTA P IS 10 PSIG?
Building
Pressure Compensating Control Valve
Delta P = 40 – 18 = 22 psig
Pout= 18 psig
Pin= 40 psig
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Rules of Thumb
Distribution Delta T = 58 – 42 = 16 degrees
Production Delta T = 56 – 42 = 14 degrees
Distribution System Delta T should always be ≥ Production System Delta T
Secondary Pumps
Load
Distribution System
Production System
Primary Pumps
ChillersTPS=42oF TDS=42oF
TDR=58oFTPR=56oF
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Rules of ThumbProduction System Delta T < Distribution System Delta T
58
58
58
58
Distribution CHWR
6.4
12.8
14.4
16
Production Delta T
1648.440800
1654.8801600
1656.4901800
16581002000
Delta T
Production CHWR
Chiller % Load
Load in
Tons
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Rules of Thumb
0.5
0.55
0.6
0.65
0.7
0.75
1009080706050403020
% Full Load
KW
/Ton
CHILLER 3
CHILLER 4&5
CHILLER 6&7
Production System Delta T should always be < Chiller Delta T
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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System Configurations
• Primary/Secondary – Constant Flow/Variable Flow• Primary Only – Constant Flow• Variable Primary Flow (VPF) – Variable Flow• Multiple Plants/Common Distribution Loop
–Plant 1 – Primary/Secondary–Plant 2 – Primary Only–Plant 3 –Primary/Secondary
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Primary/SecondaryConstant Flow/Variable Flow
Secondary Pumps
Load
Distribution System
Production System
Primary Pumps
Chillers
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Primary OnlyConstant Flow
Load
Distribution SystemProduction
System
ChillersSecondary Pumps
Primary Pumps
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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Variable Primary FlowVariable Flow
Load
Production/Distribution System
Chillers
Production/Distribution Pumps
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Multiple Plants on a Common Distribution Loop
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Hydraulic ProfileA graphical representation of the
dissipation of system head.
Ft o
f H
ead
Distance
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Hydraulic ProfilePrimary/Secondary System
Ft o
f Hea
d
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Hydraulic ProfileTwo Plants Common Distribution Loop
Ft o
f Hea
d
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Hydraulic ProfileThe Hydraulically Most Remote Point
Hydraulically most remote point & location of VFD DP sensor
Physically most remote point
Distance
Ft o
f H
ead
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Hydraulic ProfileBuilding System/Hydraulically Most Remote Point
Ft o
f Hea
d
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System Components
• Chillers• Cooling Towers• Pumps•Control Valves/Cooling Coils
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Chillers/Cooling Towers
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Chiller Performance
P-1
Pressure
Enthalpy
CompressorWork
Point 4
Point 3 Point 2
Point 1
LIFT
Pressure = CTemperature = C
Pressure = C
Q2-3 = m(h2 – h3)
Q4-1 = m(h4 – h1)W1-2 = m(h2 – h1)
h3 = h4
COP = Output/InputCOP = Q4-1/W1-2
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Cooling Tower PerformanceEntering Condenser Water 95
degrees
Leaving Condenser Water 85 degrees
Outside Air Wet Bulb Temperature 76 degrees
Range 95 – 85 = 10 degrees
Approach 85 – 76 = 9 degrees
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Cooling Tower Performance
0.5
2.5
2.0
1.5
1.0
Tow
er S
ize
Fact
or
Approach30252015105
ConstantsHeat LoadRangeWet Bulb
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Pumps
How They Work
Arrangements
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Pumps – How They Work
CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
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Pumps – How They Work
Velocity
PressureA
BC
A
B C
Flow Path
Suction
Centrifugal Pump
Outlet Tip of Impeller Vane
Discharge
Inlet Tip of Impeller Vane
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NPSH = Net Positive Suction HeadPumps – How They Work
Velocity
PressureA
BC
A
B C
Flow Path
Suction
Centrifugal Pump
Outlet Tip of Impeller Vane
Discharge
xxxx
Vapor Bubbles
Collapsing Bubbles
Pump Impeller Blade
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Pumps – How They WorkTypical Pump Curve
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Pumps – How They WorkVariable Frequency Drives
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Pumps – How They WorkVariable Speed Pump Curves
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Pumping Arrangements
Hea
d Ft
.
Hea
d Ft
.
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Cooling Coil/Control Valve
ConfigurationsHow They Work
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Cooling Coil/Control ValveConfigurations
Entering Air 70 degreesLeaving Air 55 degrees
CHWS 42 degrees
CHWR 56+ degrees
CONTROL VALVE
COOLING COILDelta T: 56 – 42 = 14 degrees
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How They Work“Control Valves Waste Energy”
Cooling Coil/Control ValveFt
of H
ead
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Cooling Coil/Control ValveHow They Work
Valve Seat Fixed
Valve Disc Not FixedValve Shaft
Actuator Arm Connected to the Valve Shaft
FLOW
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Cooling Coil/Control ValveHow They Work
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Delta T• Difference between CHW Return & CHW Supply
and Chilled Water Supply TemperaturesDelta T = TCHWR Delta T = TCHWR -- TCHWSTCHWSQ = C x Q = C x GPMGPM x x Delta TDelta T
• For the same Q if delta T is low then GPM is high & if delta T is high then GPM is low!
5,000,000 5,000,000 BtuhBtuh = C x = C x 1000 1000 gpmgpm x x 10 F10 F= C x = C x 500 500 gpmgpm x x 20 F20 F
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Low Delta T / Flow Limited Plant
Chiller
Decoupler
Load Typical
Pressure Compensating Valve Typical
2,000 Ton Chillers, 14 degree delta T, 3,429 gpm each Secondary Pump P-2,
Variable Flow 42 degree CHWS
DistributionLoop
ProductionLoop
Chiller
Chiller
38.3
50
50
100
Percent Loaded
50
50
54
56
Distribution CHWR
8
8
12
14
Dist.Delta T
6900
6000
4000
3429
Distribution Gpm
(3)6000102872300
(2)400068582000
(2)400068582000
(1)200034292000
On Line Tonnage
Production Gpm
Load in Tons
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Delta T Flow Limited PlantCENTRIFUGAL CHILLER EFFICIENCIES
0.5
0.55
0.6
0.65
0.7
0.75
1009080706050403020
% Full Load
KW
/Ton
CHILLER 3
CHILLER 4&5
CHILLER 6&7
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Delta T Flow Limited Plant
Estimated Annual Part Load Chiller Savings due to Increased Efficiency for non Flow
Limited Operations
• Flow limited average kw/ton = 0.55• Non flow limited average kw/ton = 0.523• Annual average part load = 2000 tons• Annual part load hours of operation = 8,000• Cost of electricity including demand = $0.14• Estimated annual part load chiller
savings due to increased efficiency of operation =
(0.55-0.523)(2000)(8000)(0.14) = $60,480
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High Delta T / Full Load Plant
Chiller
Decoupler
Load Typical
Pressure Compensating Valve Typical
2,000 Ton Chiller, 14 degree delta T, 3,429 gpm Secondary Pump P-2,
Variable Flow 42 degree CHWS
DistributionLoop
ProductionLoop
100
100
100
Percent Loaded
60
58
56
Distrib. CHWR
18
16
14
Dist.Delta T
2667
3000
3429
Distribution Gpm
5634292000
5634292000
5634292000
Production CHWR
Production Gpm
Load in Tons
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High Delta T / Part Load Plant
80
90
90
100
Percent Loaded
62
60
58
56
Distrib.Gpm
1920
2400
2700
3429
Distribution Gpm
2053.234291600
1854.634291800
1654.634291800
145634292000
Dist.Delta T
Production CHWR
Production Gpm
Load in Tons
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Chilled Water Cost VariablesVariables Constants
Average Annual Cooling Load 4,500 Tons Flow 500Electric Chiller/Tower/Condenser & Production Pumps 0.9 Kw/Ton Ton 12000 BtuhAbsorption Chiller/Tower/Condenser & Production Pumps 0.3 Kw/Ton Power 0.746 Kw/HpDistribution System Delta T 11 Degrees F Max Speed 60 HzCost of CHP Electrical Power $0.065 $/Kwh GPM/Ton 24Power Factor 0.9 System Curve Constant 0.8Pump Efficiency 0.87 MM 1,000,000Pump Design Flow 15000 GPMPump Design Head 155 FtPump Hp 750 Hp AssumptionsElectric Chiller Capacity 2000 TonsAbsorption Chiller Capacity 1385 Tons Absorption Chillers are always lead chillersNumber of Electric Chillers 1 Electrical Cost includes all byproduct burdensNumber of Absorption Chillers 2 Building Pumping is not considered a CHP operatioElectric Chillers 12 Delta TAbsorption Chillers 16 Delta T
Costs not IncludedCalculations
Capital FundingDistribution Flow 9818 GPM Sinking FundsDistribution Pump Hp each 210 Hp Load Flow AdministrativeDistribution Pumping Kw each 200 KwAbsorption Chillers Operating 2 2Electric Chillers Operating 1 2Number of Distribution Pumps Running 1Percent rpm each pump 65%Annual Average Cost of Cooling $5.57 $/MMBtuElectric Chillers Flow 4000 GPMAbsorption Chillers Flow 2078 GPM
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How does your System work Now ?
Existing Distribution System Maximum Delta T = ??degrees
Existing Distribution System Average Delta T = ?degrees
Chillers – Staging?System Pumping Energy – Optimized or not
Optimized? (Control Delta P)
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How should your System work when Optimized?
Optimized Maximum Delta T = ?? degreesOptimized Average Delta T = ?? degrees
Chillers – Staging ??System Pumping Energy – Optimized or not
Optimized ??
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THE PROCESS
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Step #1
Chilled Water Systems Questionnairefor Initial System Evaluation
SYSTEM DATAROI
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Step #2
Pre Project Staff Training
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Step #3
Pre Project Measurement & Verification (M&V)
BEFORE AFTER
Data Historian/Sensors Project ?Data Historian/Sensors Project ?
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATONStep #4
Chilled Water System Engineering Evaluation & Analysis
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0100200300400500600700800
8 10 12 14 16 18 20 22 24
System Delta T
Pum
ping
HP
750 HP; 14,000 GPM; 8o∆ T;
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Step #5
Report of Findings and Recommendations
ROI
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Step #6
Implement Chilled Water System Optimization Construction Project
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Step #7
Commission Chilled Water System Optimization Project
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Step #8
Post Project M&V for Rebate Verification
BEFORE AFTER
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Step #9
Post Project Staff Training
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THE RESULTS
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The University of California Davis Medical Center,
Sacramento
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
UCDMC1. 3,000,000 square feet Trauma
Center/Hospital/Clinic & Educational Buildings.
2. 26 MW CHP w/ Primary/Secondary 16 degree plant serving a 12 degree campus.
3. Each building was decoupled and pumped.
4. Average distribution system delta T was 8 degrees. Maximum delta T was 11 degrees.
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ResultsOperations
1. 18 degree distribution system delta T w/ 114 degrees outside air temperature.
2. Central plant spare distribution pump and chiller capacity.
3. Some buildings performing in excess of 20 degree delta T.
4. Average system delta T is 12 degrees.
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Results
Financial1. Financial data not available due to lack of system
instrumentation.
Energy2. Energy data not available due to lack of system
instrumentation.
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Lessons Learned1. Create a system optimization sensor project to
facilitate data acquisition for pre & post project M&V.
2. Provide pre project staff/management training to facilitate a coordinated effort for all parties.
3. Develop a detailed Site Acceptance Test for control valve commissioning.
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BIOTECHNICAL CORPORATION
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Biotechnical Corp1. 3,000,000 square feet of R&D, Office & Production
across 25 buildings.
2. Three Central Plants on common distribution loop, 14,100 ton installed capacity.
3. Delta T performance was 6 degrees part load and a maximum of 11 degrees at full load.
4. A 14 degree campus.
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ResultsOperations
1. Achieving distribution loop 20 degree Delta T @ full and part load.
2. Maximum flow distribution pumping requires 3 and not 4 operational pumps
3. Delayed major capital infrastructure expansion project for 3 years due to optimizing use of existing infrastructure.
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Results
Financial1. Financial data not available due to lack of
system instrumentation.
Energy1. Energy data not available due to lack of
system instrumentation.
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Lessons Learned1. Discovered other system issues that were masked
by poor system performance; Damper Failures, Sensor Calibration, etc.
2. Train installing controls contractor on Systems Optimization Concept and Process.
3. Verify AHU isolation valve arrangement and function prior to issuing contract requiring continued system operation during construction.
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The University of Iowa
Hospital and Clinics
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UIHC
1. 4,000,000 square feet of contiguous hospital/clinic space between five buildings.
2. Central Plant metered and billed for each building.
3. Each building is decoupled and pumped.
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ResultsOperations
1. Resolved low chilled water pressure & flow to Operating Room Air handlers.
2. Resolved condensation issue on cooling panel ceilings in patient rooms.
3. Removed tertiary building pumps and reduced operation of building pumps
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Results
Financial1. Savings $2,800,000 for the last 2 cooling seasons
primarily from penalty reduction.
2. Chilled Water billing based on building flow and an assumed Delta T of 16 Degrees.
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Results
Energy1. Original simple payback estimate 5 years.
2. System instrumentation was not adequate to measure actual energy reduction.
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
Lessons Learned1. Building system instrumentation not adequate
to provide M&V for energy consumption.
2. Building system energy savings and production/distribution billed savings are not the same number.
3. Production/distribution system billed savings represented a simple payback of less than 9 months.
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CHILLED WATER SYSTEM OPTIMIZATONCHILLED WATER SYSTEM OPTIMIZATON
[email protected]@ra-solutions.comwww.ra-solutions.com