Track and Minimize Pump Energy Consumption Using Variable Frequency Drives, Flow Meters, & Telemetry

By
Jim Mimlitz
Navionics Research, Inc.
Illinois Rural Water Association
Training Course
Effingham, Illinois
16 February 2016
Track and Minimize
Pump Energy Consumption
Using Variable Frequency Drives,
Flow Meters, & Telemetry
© 1995-2016 COPYRIGHT
NAVIONICS RESEARCH INC.
ALL RIGHTS RESERVED.
RIRIwireless-telemetry.com IRWA Training

Pump Station Energy Efficiency…
A topic of continual concern for today’s water utility is Pumping Station Energy Efficiency.
And to put this subject in laymen’s terms, how better than to relate it to fuel efficiency for the familiar
automobile?

Measurement of Energy Efficiency…
“You can’t manage what you don’t measure.”
-Fred Smith, Founder Federal Express
Work Measurement — With a car, the unit of work is expressed
as a driven “Mile”; whereas in a pumping station, the unit of
worked is expressed as a pumped “Gallon” of water.
Energy Source Measurement — The unit of energy for a car is a
“gallon of gasoline”, whereas the energy unit for an electric pump
is a “Kilowatt-Hour (KWH)”. At the time of this writing, a gallon of
gasoline is around $2.00, and a Kilowatt-Hour is around $0.12.

Energy Efficiency: Work-to-Energy Ratio
When shopping for a car, one seeks the vehicle that offers the highest
work/energy ratio — expressed in the familiar MPG, or miles per
gallon of gasoline. After purchase, the driver can control the speed of
the vehicle so as to maximize the MPG. We know that a car achieves
its highest MPG at moderate speeds, and worst MPG at high and low
speeds. And as drivers, don’t we balance our desire to complete our
trip in a short time against our desire to achieve the highest possible
MPG?
These principles apply to pumping stations, as well. Here, we also
wish to complete the work quickly — for example: fill a water tower —
but we also wish to minimize energy costs. As with a car, we often
discover that moderating the pump speeds can lead to lower energy
costs.

Energy Efficiency Calculation…
Before energy optimization can be attempted, we first need a
method of quantifying the energy efficiency of our pumping
system.
In the automobile example, we use the work/energy ratio —
MPG. In our pumping system, we propose to use the
work/energy ratio of gallons of pumped water per kilowatt-
hour — I propose we call it “GPK”.
For a car, it’s often just called “mileage” for short… So for our
pump station, let’s just call it “gallonage”.

Realtime Energy Efficiency Display…
To help the driver monitor and maximize fuel efficiency, certain
automobiles even display the current MPG on the console. To provide this
reading, an internal computer divides the speed (miles per hour) by the
metered fuel consumption rate (gallons of gasoline per hour) to provide
“miles per gallon”.
Example: If a car is traveling 60 miles per hour, and its fuel consumption
rate is 3 gallons per hour, then its computer calculates the “mileage” to
be 60/3 or 20 miles per gallon.
Automobile Trip Computer:
Fuel Efficiency Display.

Efficiency Calc Translates to Dollars Calc…
Knowing the cost of a gallon of gasoline, we can put this in terms of
dollars — 20 (miles per gallon) / 2.00 (dollars per gal) = 10 miles per
dollar.
In a pumping system, the “gallonage” (gallons/kilowatt-hour) is
calculated by dividing the pump flow rate (gallons per hour) by the
energy consumption rate (kilowatt-hours/hour—same as kilowatts). For
example, if a pump’s flow rate is 30,000 gallons per hour, and the energy
consumption is 20 Kilowatts, then the “gallonage” is 30,000/20 or 1500
GPK.
Knowing the cost of a Kilowatt-Hour, we can also put this in terms of
dollars — 1500 GPK / 0.12 (dollars per KWH) = 12,500 pumped gallons
per dollar.

Comparison of Automobile and Pumping System Work and Energy Metrics
Automobile: Pumping System:
Work Unit: Driven Mile Pumped Gallon of Water
Fuel Unit:
Gallon of Gasoline Kilowatt-Hour (KWH)
Efficiency Measure:
Miles per Gallon —
MPG or “Mileage”
Pumped Gallons per KWH —
GPK or “Gallonage”
Display: Automobile Trip Computer Telemetry/SCADA System
Efficiency Calculation Matrix…

Application Success…
Work Summary…
• Retrofit Booster Station Starters: ACL to VFD’s
• VFD and Telemetry Energy Analytics Applied
• Telemetry Setpoint Tuning
Result Summary…
• Increased Work/Energy Ratio by Factor of 3.03
• Equivalent to increasing auto mileage from 20 GPM to
over 60 GPM
• Reduction of Average Monthly Cost of Pump Energy
From $345/month to less than $114/month
• Annual Savings of over $2776 per year in electricity

• Key: Reduction of Friction Losses.
• Automobile Analogy: Why does an automobile achieve better gas
mileage at moderate speeds than high speeds? The reason is
rooted in friction or "drag".
• Drag Force increases as speed squared (2x – Factor of 4).
• Drag Power increases as speed cubed (2x – Factor of 8).
• Reducing speed by half, for example, decreases friction force by a
factor of four (and decreases friction power by a factor of 8).
• Keep in mind, though, that cutting the speed in half would require
the auto to run twice as long — so the friction losses decrease
overall by a factor-of-4.
The Source of Increased Efficiency?…

Total Friction Losses Increase as the Square of the Velocity.

Distribution Pipeline Friction Losses…
• Water Distribution System: Drag losses mainly occur
between the flowing water and the inner pipeline
surfaces, but the same principle applies: drag force
increases as the flow velocity squared.
• It is here — the reduction of friction losses — where
substantial energy savings may be hiding within a
water utility — and waiting to be discovered.

• In order to control the pump flow velocity, the pump speed
must be controlled with a VFD — a Variable Frequency
Drive.
• VFD: A type of motor controller that varies the frequency
and voltage supplied to the electric motor. Other names for
a VFD are variable speed drive, adjustable speed drive,
adjustable frequency drive, AC drive, microdrive, and
inverter.
• In pump station applications, VFDs can be used to provide
variable-speed pumping operation, as well as to provide
slow ramp-up starts and slow ramp-down stops.
Controlling Pipeline Friction Losses…

• Eliminate Pump-Induced Water Hammers.
• Achieve Discharge-Pressure-Limiting Pump Speed Control.
• Achieve Suction-Pressure-Sustaining Pump Speed Control.
• Implement Water-Tower-less (Demand-Based) Pumping
Systems.
• Implement Emergency-Supply Pumping Systems Capable
Of Automatically Sensing Fire-Flows And Increasing The
Pump Speeds To Satisfy The Temporary Emergency
Demand.
Telemetry Integrated with VFDs & Flow
Meters – the Past

• Leverage most sophisticated VFD networking technologies available.
• Modbus® Industrial Communication Protocol – Non Proprietary.
• Rich Information Sharing Between Telemetry and VFD Algorithms.
Telemetry Networked with VFDs & Flow
Meters – the Future

• Water Utility: Long-Time Client Williamsville, Illinois
• SCADA System Installed Year 2000: Two Water Towers, Two
Pumping Stations, One Ground Tank, One SCADA Server.
• All Pumps: Solid-State Soft Starters Before Upgrade. Despite
presence of soft starters, distribution system still suffered from
significant water pressure hammers, which can weaken and/or
rupture distribution mains.
• Soft starters in the booster pumping station were replaced with
25HP Allen Bradley PowerFlex 400 VFD’s and Reactors.
• Validation of Telemetry VFD & Energy Optimization Techniques.
Application Success…

Pump Station Photos…

• Telemetry VFD & Energy Analytics utilizes digital, two-way network
communication with the VFD.
• Client Provided With Detailed Monitoring and Control Capabilities:
• Ability to Visualize Pump “Gallonage” In Realtime (GPK)
• Speed Control (%)
• Acceleration Rate Control (%/sec)
• Deceleration Rate Control (%/sec)
• Speed Monitoring (%)
• Bus Voltage Monitoring (VDC)
• Output Voltage Monitoring (VAC)
• Output Current Monitoring (Amps)
• Output Power Monitoring (KiloWatts)
• Accumulated Energy Consumption Monitoring (Kilowatt-Hours)
• VFD Internal Temperature (Heat Sink) Monitoring (deg F)
• Pump Efficiency Monitoring (%)
Automated Telemetry Data & Analysis…

Telemetry Historical Trends…
Pump Running
VFD Speed (0-100%)
Flow (GPM)
Energy (KW)
Pump Efficiency
(Note: Not Overall Energy Efficiency)
Gallonage (GPK)
VFD Temperature (deg F)
Suction Pressure (PSIG)
Discharge Pressure (PSIG)
VFD Bus Voltage (DC Volts)

Telemetry Historical Trends…
VFD Output/Motor Voltage (AC Volts)
Flow Meter Totalization (Gallons)
VFD Energy Totalization (KWh)
VFD Fault CodeVFD Output/Motor Current (AC Amps)

Telemetry Components…
• Most important energy information produced by
Telemetry VFD & Energy Analytics is “Pump Gallonage”
metric, which tracks a running Gallons/KWH (GPK) figure.
The pump station RTU re-calculates this figure every few
seconds as follows:
"Gallonage"(GPK)
= FlowRate(gal/hour) / MotorPower(kw)

• Utilizing power measurement equipment combined with a
SCADAmetrics EM-100 EtherMeter Flow Meter Gateway, a
baseline energy and flow assessment was performed before
installation of the VFD’s:
• Average Rate-of-Flow: 352.3 GPM
• Average Power Consumption: 15.918 KW
• Average Pump Gallonage: 1328 GPK
Baseline Efficiency Measurement…
Fluke Energy Meter SCADAmetrics EtherMeter®

Post-Upgrade Architecture…

• VFD’s Installed.
• Adjustment of Key Telemetry Setpoints, Related to Pressure
Limits, Flow Rates, and Pump Speed Limits.
• Selected Setpoints Delivered an Optimal Balance Between
Pump Speed and Energy Efficiency (GPK).
• Automatic Recognition of Need For Higher Speeds (Lower
Energy Efficiency) to Meet Varied Water Demands.
• New Average VFD Speed: 60%
• New Average Rate-of-Flow: 169.34 GPM
• New Average Power Consumption: 2.519 KW
• New Average Pump Gallonage: 4033 (GPK)
Efficiency Optimizations…

• By plugging in the cost of a KWH (approximately $0.12 in 2015
Illinois), the energy cost and savings were easily calculated:
• 100% Speed (No VFDs): 1328 (GPK) / 0.12 (Dollars/KWH)
= 11,067 Gallons/Dollar
• 60% Speed (With VFDs): 4033 (GPK) / 0.12 (Dollars/KWH)
= 33,608 Gallons/Dollar
Efficiency Translated to $...

• Since the booster station averages about 3.82 MGal/Month, the
energy costs and savings were also easily calculated:
• 100% Speed (No VFDs): 3,820,000 (Gal/Month) / 11,067
(Gal/$) = $345/Month
• 60% Speed (With VFDs): 3,820,000 (Gal/Month) / 33,608
(Gal/$) = $114/Month
• Energy Savings: $231/Month or $2772/Year — (67%)
• Bottom Line: Client realized an energy consumption decrease of
67%.
• Please note that your savings may be more or less, as every
application is unique!
Monthly and Annual Savings…

• VFD Fault Alarming and Remote Reset
• Water Hammer Elimination
• VFD Temperature Monitoring and Alarming
• VFD Health Monitoring and Alarming
• VFD Network Communications
• VFD Terminal Block (Backup) Controls
• Faster-than-100% Pump Speed
• Utility Rebates
• Power Factor Correction
• 3-Phase Power Generation From Single-Phase Power
VFDs with Benefits…

VFD’s have additional internal protections that go above-and-beyond those in a typical across-the-line
motor starter.
For example, when a momentary overvoltage is detected, the VFD will shut down and report a fault
code on its LCD display. The VFD will not allow a restart until the operator acknowledges the alarm by
pressing the RESET button on the VFD keypad.
A common problem faced by VFD users is the occasional nuisance fault, which requires travel to the
remote site to press the VFD RESET button. This can be particularly bothersome for water utilities who
suffer from poor electric power quality.
However, these problems can be alleviated — Telemetry VFD & Energy Analytics provides the operator
with instant alarm notifications via the SCADA system when a VFD fault is tripped. The operator is also
notified of the nature of the fault (the actual fault code).
Operator is able to acknowledge and reset the fault remotely at his discretion, even using a smart
phone, such as an iPhone or Android.
VFD Faults May Be
Remotely Viewed
And Reset
VFD Fault Alarming and Remote Reset…
Any VFD Faults That Occur are Viewable
within the Telemetry via the Network

The featured Williamsville booster pump station was equipped with soft starters before the installation of
the VFD upgrade. Their soft starters provided a 30-second ramp-up and ramp-down of the pumps, but
Williamsville still saw significant water hammers right at start-up and shut-down.
The VFD upgrade was programmed to provide a 300-second ramp-up and ramp-down, which completely
eliminated all pump-induced pressure spikes, as illustrated in the following before and after Telemetry
history charts:
Water Hammer Reduction…
Discharge Pressure
Suction Pressure
Discharge Pressure
Suction Pressure
Before After

Eventually, all cooling fans fail. As a moving part subject to wear — It’s simply a fact of life — And
every VFD is equipped with active cooling fans for protection against current-generated heat buildup.
The VFD Analytics Module, though, is capable of monitoring and alarming the VFD Heat Sink for extreme
temperatures, allowing the owner to detect and repair a broken fan before the entire VFD fails due to
overheating.
Also, VFD’s are occasionally installed outdoors — for example within a NEMA-3R outdoor package — and
these units can be subject to both hot and cold extreme temperatures. To protect the drive electronics,
the enclosure is typically outfitted with additional thermostat-controlled cooling fans and heaters. The
fans, heaters, and thermostats, though, are also subject to failure. The VFD Analytics Module can
detect and alarm any over-temperatures or under-temperatures — thereby allowing the owner to detect
and repair the temperature controls before the entire VFD fails.
VFD Heat Sink Temperature May Be Viewed and Alarmed — Particularly Useful for the Detection of
Enclosure Fan or Heater Failures.
VFD Temperature Monitoring…
VFD Temperature (deg F)

• If a VFD suffers a non-resettable failure, one of the first on-site
troubleshooting steps is to verify that the drive is holding the correct DC bus
voltage: 1.41 x Station Voltage. The PowerFlex drive has multimeter
hookup terminals dedicated to helping the technician perform this function.
• Telemetry VFD & Energy Analytics provides functionality to extract the DC
Bus Voltage, display the value on the Telemetry screen, and generate alarms
when the Bus Voltage falls outside of specifications.
• A Healthy VFD Has A Bus Voltage of Approximately 1.41 x Station Voltage.
• For instance, in a 230VAC Station, the DC Bus Voltage Should Be
Approximately 325VDC.
VFD Health Monitoring and Alarming…
VFD DC Bus Voltage (Volts DC)

• The Analytics software can also extract and present important
electric power output data —namely speed, voltage, current,
kilowatts , and kilowatt-hour information:
VFD Electrical Monitoring…
VFD Speed (0-100%)
VFD Output/Motor Voltage (AC Volts)
VFD Output/Motor Current (AC Amps)
VFD Output Power (KW)
VFD Output Energy Totalization (KWh)

• Pump Efficiency: Ratio of Pump Work to Pump Electric Power
Consumption.
• Using the new tools at our disposal, this performance measure may
be calculated and tracked in realtime:
• Pump Power Consumption (KW) — From VFD Analytics
• Flow Rate (GPM) — From EtherMeter & Flow Meter
• Pump Head Differential (PSI) — from Pressure Transducers
• Efficiency = PumpWork(kw) / VfdPowerOutput(kw)
• Efficiency = [FlowRate(gpm)x[Discharge(psi)-Suction(psi)]/2302] / VfdPower(kw)
Pump Efficiency Monitoring…

• Imperative that our VFD offer integral networking capability.
• Imperative that VFD offer that networking in the form of a non-proprietary
communication protocol — such as Modbus, EtherNet/IP, or DF1.
• A non-proprietary protocol — such as Modbus — is one that adheres to an
international communication standard and ensures that equipment from multiple
vendors can co-exist on the same network within a pump station.
• Modbus has become a de facto standard of industrial communication protocols.
Gathering momentum and support since 1979 when it was first introduced by
Modicon (now a division of Schneider Electric), it is the most common means of
connecting industrial electronic devices. It is openly published, royalty-free, and
forms a relatively easy-to-deploy industrial network.
VFD Network Communications…

• Good design practice dictates that an alternative control path be provided, in addition to the
Modbus network control.
• For example, should the Modbus network fail, then the Telemetry should still be able to run and
monitor the VFDs automatically.
• To accomplish this, we recommend an alternative backup control method — implemented via the
VFD’s terminal block.
• In case of Modbus network failure, the Operator may toggle the VFD Control to “Discrete Control”,
which will cause the Telemetry to run the pump(s) when required at a preset speed with soft-starts
and soft-stops.
VFD Terminal Block Backup Controls…
Telemetry Setpoint
to Activate Non-Network VFD Control
Non-Network VFD Control Wiring
(Orange Hookup Wires)

• If a pump motor has available, unused horsepower at 100% speed
(60 Hz), and the hydraulics will support increased flow and
pressure, then a VFD can make it is possible to run the pump at
speeds greater than 100%.
• For example, during a period of emergency high water demand, or
perhaps as a method of increasing the flow capacity of a pump
station without changing out the pump.
• When using network-based control, greater-than-100% speed is
easily achieved and generally does not require additional on-site
modifications.
Faster-than-100% Speed…

• Due to the energy-saving nature of VFD’s, along with their associated reduced motor starting currents,
many Power Utilities are offering monetary incentives to Water Utilities to upgrade across-the-line
starters in pump stations and water plants to VFD’s. Before embarking on a VFD project, it is certainly
worth investigating whether your Power Utility offers any sort of rebate or incentive plan.
• When available, the rebates in Illinois are typically around $92 per HP per pump. For example, for a 2
pump station where each pump is 50HP, the rebate might be $9200.00.
• http://smartenergy.illinois.edu/
• http://smartenergy.illinois.edu/pdf/TechNote_VFD.pdf
• http://www.illinois.gov/dceo/whyillinois/KeyIndustries/Energy/Pages/EnergyEfficiency.aspx
• Application PDF:
• http://www.illinois.gov/dceo/whyillinois/KeyIndustries/Energy/Documents/2014-
2015%20DCEO%20Public%20Sector%20Standard%20and%20Custom%20Program%20111714.pdf
Utility Rebates…

• A 3-Phase Motor with an across-the-line starter presents an inductive load to the Power grid — a less-
than-unity power factor — which in basic terms means that the current-voltage product exceeds the
stations wattage, thereby posing challenges for the Power Utility’s generation and distribution grid. A
VFD’s power factor, on the other hand, is very close to ideal (1.0) — and therefore corrects for the
motor’s inductive load.
Power Factor Correction…
Power (HP) Speed (RPM)
Power Factor
½ Load ¾ Load Full Load
0-5 1800 0.72 0.82 0.84
5-20 1800 0.74 0.84 0.86
20-100 1800 0.79 0.86 0.89
100-300 1800 0.81 0.88 0.91
Typical Motor Power Factors
(from Engineering Toolbox)
VFD Power Factor Correction, Illustrated
on the Power Meter at the Williamsville
Booster Station During a VFD-Driven Pump
Run Cycle: Power Factor=0.984

• Certain remote pump station locations are not served by 3-phase power, or the expense to bring 3-
phase power to the remote stations can be excessive. In the past, this problem was solved by
introducing add-a-phase machinery into the station to generate 3-phases from single-phase power.
With a VFD, though, the add-a-phase machinery is no longer needed, as a drive is capable of
generating 3-phases from single-phase power. Keep in mind that the VFD must be over-sized when
used in such an application.
3-Phase Generation from Single-Phase…
VFD's Can Produce 3-Phase Power from
Single-Phase, A Task Generally
Accomplished in the Past Using the
Add-a-Phase Rotating Machinery. A Single-Phase VFD Pump Application. Note
that the Power Input (Left) Has Two Wires
L1,L3 (Single-Phase), and the Motor Output
(Right) Has Three Wires L1, L2, L3 (3-Phase).

• When a networked VFD is provided and installed, it is imperative that
full documentation be provided, so that future service or
replacements can be handled easily:
• Make & Model w/ Full Part Number
• Personality Settings (Motor Nameplate Values, Terminal Block
Settings, IP Address, Comm Settings, etc.)
• User Manual
• Fault Code Table
• Wiring Diagrams
Importance of VFD Documentation…

Conclusion
Thank You!
Jim Mimlitz
Navionics Research Inc.
wireless-telemetry.com
Telemetry Educational Blog:
wireless-telemetry.com/blog
Telemetry Educational Newsletter:
wireless-telemetry.com/signup/signup.htm

Track and Minimize Pump Energy Consumption Using Variable Frequency Drives, Flow Meters, & Telemetry

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