optimizing pump systems for energy efficiency gunnar hovstadius,ph.d., director of technology don...
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Optimizing Pump Systems for Optimizing Pump Systems for Energy EfficiencyEnergy Efficiency
Gunnar Hovstadius,Ph.D., Director of TechnologyGunnar Hovstadius,Ph.D., Director of Technology
Don Casada, SR. Development Associate, Oak Ridge NLDon Casada, SR. Development Associate, Oak Ridge NL
Goulds Pumps Flygt A-C Custom Pump Goulds Pumps Flygt A-C Custom Pump
Bell & Gossett Jabsco Standard Vogel Bell & Gossett Jabsco Standard Vogel
Lowara Barton McDonnell & Miller Richter Pure Flow Lowara Barton McDonnell & Miller Richter Pure Flow
ITT Fluid TechnologyITT Fluid Technology
What Is A Pump System?
• A Pump System comprises of all piping, fittings and valves before and after a pump as well as the motor and motor driver.
• There can be multiple pumps, motors and drives, and they can be arranged to operate in parallel or in series.
• Pump Systems can have static head (pressure), or be circulating systems (friction only systems)
3
First, Let's Get A Big Picture PerspectiveOf Energy Flow in Pumping Systems
Electric utilityfeeder
Transformer
Motor breaker/starter
Motor
Adjustablespeed drive(electrical)
Coupling Pump Fluidsystem
Ultimategoal
At each interface, there are inefficiencies. The goal should be to maximize the overall cost effectiveness of the pumping, or how much flow is delivered per unit of input energy.
Specific Energy Es
= Motor efficiency
= Pump efficiency
m
Es = fHS
g
m
HS
= Fluid density
= Gravitational constant
= Static head
= Hydraulic System factor
fHS
HS
g
= Pel x Time
Pumped Volumep
p
6
Understand The Ultimate Goal
Electric utilityfeeder
Transformer
Motor breaker/starter
Motor
Adjustablespeed drive(electrical)
Coupling Pump Fluidsystem
Ultimategoal
Maximize the overall effectiveness.
7
It Is Essential To Understand TheUltimate Goal Of The Fluid System To Optimize It
• Understand why the system exists
• Have clearly defined criteria for what is really needed
• Understand what's negotiable and what's not
Requirements For Designing A System
• Duration Curve (Flow)• System Curve (Pressure vs. Flow)• Pump & Component selection
0
1000
2000
3000
0 2000 4000 6000 8000 10000
Time [hours]
Infl
ow
[G
PM
]Annualized Flow Duration Curve
10
Understand The Fluid System
Electric utilityfeeder
Transformer
Motor breaker/starter
Motor
Adjustablespeed drive(electrical)
Coupling Pump Fluidsystem
Ultimategoal
Maximize the overall effectiveness.
11
System Curves Are Made Up Of Two FundamentalComponents - The Static Head And The Frictional Head
120
80
40
0
Hea
d,
ft
500040003000200010000Flow rate, gpm
Static/Fixed
Friction
Total
Hydraulic System Factor
• The Hydraulic System factor is defined as “The ratio of a hydraulic system’s static head to total head”.
Head
Flow
Totalhead Loss Head
Static Head
SYSTEM CURVE
HSf
HSf
fHS
HS
HS + HF
=
13
What Are Some Sources OfFriction In Pumping Systems?
Pipe walls
Valves
Elbows
Tees
Reducers/expanders
Expansion joints
Tank inlets/outlets
(In other words, almost everything that the pumped fluid passes through, as well as the fluid itself)
Operational Costs Are Influenced By The Selection Of Components
And Their Size
Annual Frictional Cost Per 100 ft Of Pipe
Assumptions: 80% combined pump and motor efficiency, electricity cost = 10 ¢/kWh
5000
4000
3000
2000
1000
0
An
nu
al
cost
($
)
500040003000200010000flow rate (gpm)
12" 14" 16"
Frictional Losses Can BeTranslated Into Operating Costs
12-inch line, 100 ft length, 10¢/kWh, full open valves,80% combined pump & motor efficiency
Assumptions:
1000
800
600
400
200
0
An
nu
al
Co
st (
$)
25002000150010005000flow rate (gpm)
Check valve Butterfly valve Sch. 40 pipe (new)
17
Understanding The Pump
Electric utilityfeeder
Transformer
Motor breaker/starter
Motor
Adjustablespeed drive(electrical)
Coupling Pump Fluidsystem
Ultimategoal
Maximize the overall effectiveness
18
Nameplate Data Applies ToOne Particular Operating Point
200
150
100
50
0
Hea
d,
ft
500040003000200010000Flow rate, gpm
Rated:3190 gpm, 97 ft
Head-capacity curve
100
90
80
70
60
50
40
30
hea
d (
ft)
500040003000200010000flow rate (gpm)
How Do We Know Where We'll BeOperating On The Pump Curve?
Pump and systemcurve intersection(operating point)
System head curve
Pump head curve
Nameplate
Efficiency And Brake Horsepower Are
Commonly Plotted vs. Pump Flow100
90
80
70
60
50
40
30
20
10
0
hea
d (
ft),
po
wer
(b
hp
), e
ffic
ien
cy (
%)
500040003000200010000flow rate (gpm)
System Pump head brake hp efficiency
Operatingpoint
BEP
Using A Larger Pipe Changes TheFrictional Part Of The System Curve
100
90
80
70
60
50
40
30
hea
d (
ft)
500040003000200010000flow rate (gpm)
System head,12" pipe
System head,16" pipe
CENTRIFUGAL PUMP PERFORMANCE WITH VSD REGULATION
FLYGT C 3531
30-60 HZ (295-590 RPM)
Specific Energy in Three Different Single Pump Systems
Throttling
VSD Regulation
Speed / Flow
No static head85% static head50% static head
Speed / FlowSpeed / Flow
On-Off Regulation
24
Now Let's Look At The Electrical End Of The Shaft
Electric utilityfeeder
Transformer
Motor breaker/starter
Motor
Adjustablespeed drive(electrical)
Coupling Pump Fluidsystem
Maximize the overall effectiveness
Ultimategoal
Motor Efficiency CurvesAre Dependent Upon Size And Type
100
90
80
70
60
50
Eff
icie
ncy
(%)
1.21.00.80.60.40.20.0Power (fraction of rated)
Rated horsepower 3 5 7.5 10 25 50 100 125 200 fit 7.5 fit 100
26
Understanding Drive Performance
Electric utilityfeeder
Transformer
Motor breaker/starter
Motor
Adjustablespeed drive(electrical)
Coupling Pump Fluidsystem
Ultimategoal
Maximize the overall effectiveness
The Efficiency Of InvertersIs Affected By Operating Speed
100
90
80
70
60
effi
cien
cy(%
)
1251007550speed (% of rated)
Typical inverter efficiencies
as a function of motor speed
Evaluate System Design
• Is the system effectiveness acceptable?• If the system has static head, Compare with
frictionless performance!
Re-Evaluate System Choices Relative To Needs
• Number of pumps• Pump sizes• VFD operation?• Pipe diameters• Component selection
When the System is Commissioned the Theoretical Calculations Should be
Compared to Actual Operational Data to Ensure that it is Operating as Intended
Summary
• Most avoidable losses are in the pump and fluid system, not in the electrical front end
• However, the electrical front end can help reduce the fluid system losses
• Be careful with local optimization• Determine the specific energy and compare with the ideal
