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VFD’s Energy Savings VFD’s Energy Savings A Case Study on A Case Study on BoilersBoilers

National Grid Solutions & Opportunities National Grid Solutions & Opportunities Upstate New York Energy Efficiency Upstate New York Energy Efficiency

Conference & ExpoConference & ExpoApril 7, 2011April 7, 2011

Dean Williamswww.emainc.netVice President of Technical Services800-607-3322

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How Do We Pay For Electricity?How Do We Pay For Electricity?

As Commercial & Industrial users, we pay many charges. The two we will talk about reducing are:

The quantity of energy (kW= 1,000watts) used over a period of time, measured in kilowatt hours (kWh). Trivia, 100HP = 74.6 Kilowatts.

Peak Demand, the highest “draw” of energy, measured in kilowatts over a recycling 15 minute window each month. © copyright 2009

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Variable Frequency Drive (VFD)Variable Frequency Drive (VFD)Device used to vary the speed of an electric motor. Device used to vary the speed of an electric motor. For building For building

HVAC, VFDs are purchased to achieve energy savings by taking HVAC, VFDs are purchased to achieve energy savings by taking advantage of the Affinity Laws.advantage of the Affinity Laws. To achieve energy savings we To achieve energy savings we will look at loads, such as pumps, blowers, and cooling towers. will look at loads, such as pumps, blowers, and cooling towers.

Includes built-in motor protection Includes built-in motor protection

Adjustable to the motor specifications. Adjustable to the motor specifications.

Adjusts both the frequency Adjusts both the frequency & voltage to the motor& voltage to the motor

Reduces the inrush current to Reduces the inrush current to 115% (pumps and fans) of the 115% (pumps and fans) of the motor rated current, possibly motor rated current, possibly

reducing Peak Demand Charges.reducing Peak Demand Charges.

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The VFD starts the motor by applying a low The VFD starts the motor by applying a low frequency AC waveform to the motor and slowly frequency AC waveform to the motor and slowly ramping it up to the desired frequency. ramping it up to the desired frequency. Remember, AC Frequency=Motor Speed.Remember, AC Frequency=Motor Speed.Therefore, a major benefit of VFD’s is controlled Therefore, a major benefit of VFD’s is controlled acceleration acceleration and and decelerationdeceleration. This can help in a . This can help in a variety of ways.variety of ways.Instead of attempting to immediately jump to full Instead of attempting to immediately jump to full

speed, the motor can now smoothly come up to speed, the motor can now smoothly come up to speed in an user adjustable time period. This speed in an user adjustable time period. This can eliminate the shocks which are often can eliminate the shocks which are often associated with starting motors. Extended belt, associated with starting motors. Extended belt, coupling and motor life is the benefit gained.coupling and motor life is the benefit gained.

Variable Frequency Drive Start

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“Types of Loads”Loads can be grouped into two basic categories:

Constant Torque Loads Load does not change with speedIndustrial loads like presses, conveyors, extruders, compressors, mills, etc.

We buy VFD’s for these applications to control the process,We buy VFD’s for these applications to control the process,

Not to save energy.Not to save energy.

Variable Torque Loads (Energy Savings Potential!)

Load changes with speedHVAC, pumps and fans on industrial processes

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Drives (VFDs) & Energy SavingsDrives (VFDs) & Energy Savings

Heating Ventilation & Air Conditioning (HVAC) Fans & Pumps are some of the largest electrical loads in commercial buildings. Pumps and Fans are also used in many industrial manufacturing processes.

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How did we control FLOW before How did we control FLOW before Variable Frequency Drives?Variable Frequency Drives?

Dampers & Valves (very inefficient)Dampers & Valves (very inefficient)Air Dampers & Valves limit flow by placing a Air Dampers & Valves limit flow by placing a

restriction in the system. Most HVAC pumps and restriction in the system. Most HVAC pumps and fans do not shut down when the system is satisfied.fans do not shut down when the system is satisfied.

Imagine pressing the accelerator of your car to the Imagine pressing the accelerator of your car to the floor and trying to slow the car down by pressing the floor and trying to slow the car down by pressing the brakes at the same time…wasteful!brakes at the same time…wasteful!

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Fan & Pump Loads

Flow is directly proportional to speed.90% speed =90% flow

No need for valves & dampers

Horsepower is directly proportional to the cube of the speed.

1 HP = 746 watts (How do we pay for power?)

The basic Affinity laws can be converted for use with centrifugal fans and pumps. On pumps,

watch out for high static head systems

FLOW = RPM’sFLOW = RPM’s

HP= (RPM’s)HP= (RPM’s)³³

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0%

20%

40%

60%

80%

100%

0% 50% 100%

Speed (%)

“Variable Torque Loads”With a variable torque load, torque loading is a function of the speed. The torque will change with the square of the speed and the Horsepower will change with the cube of the speed.

FLOW=SPEED

Torque

Horsepower

SpringFall

WinterSummer

A 10% reduction in speed = 27% reduction in power!

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Central Utilities PlantOperating since 1924

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Steam Turbine Cogeneration

Hot Water

ElectricitySteam

Boiler

Turbine Generator

Buildings

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Cogeneration Project Schematic

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New Boiler Installed 2006New Boiler Installed 2006

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Forced Draft Blower 500 HPForced Draft Blower 500 HP

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Original Inlet Damper ControlOriginal Inlet Damper Control

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Problems with Existing ApplicationProblems with Existing Application Inability to maximize the capabilities of the

FD-fan motor & full boiler capacity& full boiler capacity Damper control prevented the boiler from

performing as designed and operating efficiently during the shoulder months of spring and fall.

Vibration and noise was created in the vicinity of the FD fan because of poor air-path conditions & & high speedhigh speed

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Installed 500HP VFD 2009Installed 500HP VFD 2009Total Project Cost $52,000.00Total Project Cost $52,000.00

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The Proof is in the FiguresThe Proof is in the FiguresBEFORE AFTER

Cogeneration-plant 50-day electricity consumption 383,087 kwh 217,000 kwhCogeneration-plant 50-day steam production 141,093,563 lb 139,988,998 lbVibration in vicinity of forced-draft (FD) fan High Low Ambient noise in vicinity of FD fan High Low Maintenance requirements of FD-fan system High Low Electrical Power Factor Poor Excellent

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Benefits of the VFD installation Precise and efficient control of the No. 9 boiler through

the full span of its production rating. Finally achieve Finally achieve full capacity rating.full capacity rating.

The motor’s average speed is about 45 Hz, which has reduced maintenance, vibration, and ambient noise. Damper was removed!

Motor runs cooler, its lifespan, along with the operating life of the FD fan and associated equipment, will be increased

Power factor improvementPower factor improvement Reduction in Peak Demand LoadReduction in Peak Demand Load

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Other benefits of the VFD installation

The new FD fan and its upgraded controls allowed the university to change the way it operates the plant by increasing the steam load on the No. 9 boiler (the most efficient boiler on campus) and reducing the steam load on the No. 6 boiler. Additionally, No. 9 boiler now can run very efficiently throughout the year, regardless of ambient temperature or demand.

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Central Utilities #9 Boiler Cogeneration UpgradeCentral Utilities #9 Boiler Cogeneration Upgrade

The Savings 500hp Forced Draft fan) The Cogeneration building has run continuously since the shutdown without issue The energy savings realized for the first year will be approximately $85,000.00!! By taking advantage of the current rebates for installing the variable frequency drive….

Final Project ROI was less than 6 months!Depending on boiler utilization, annual operational savings could be as

much as $200,000.

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How does this Green Technology Really How does this Green Technology Really make you make you $GREEN$?$GREEN$? VFDs save money due to the application of VFDs save money due to the application of

pumps, and fans following the Affinity Laws. pumps, and fans following the Affinity Laws. HP=Speed cubedHP=Speed cubed

The cost of electricity has, and will increaseThe cost of electricity has, and will increase The cost of VFD’ has decreased due to matured The cost of VFD’ has decreased due to matured

technologytechnology VFDs reduce Maintenance costs, & extend VFDs reduce Maintenance costs, & extend

equipment life spanequipment life span Using VFDs greatly reduces energy consumption, Using VFDs greatly reduces energy consumption,

hence it is called environmentally hence it is called environmentally GREEN GREEN technology…I like to say it puts $GREEN$ in your technology…I like to say it puts $GREEN$ in your pockets!pockets!