optimizing pump systems for energy efficiency gunnar hovstadius,ph.d., director of technology don...

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

THANK YOU

Gunnar Hovstadius

email: gunnar_hovstadius@fluids.ittind.com