VFDs Energy Savings A Case Study on Boilers National Grid Solutions & Opportunities Upstate New York Energy Efficiency Conference & Expo April 7, 2011 Dean Williams Vice President of Technical Services

How Do We Pay For Electricity? As Commercial & Industrial users, we pay many charges. The two we will talk about reducing are: n n The quantity of energy (kW= 1,000watts) used over a period of time, measured in kilowatt hours (kWh). Trivia, 100HP = 74.6 Kilowatts. n n Peak Demand, the highest draw of energy, measured in kilowatts over a recycling 15 minute window each month. © copyright 2009

Variable Frequency Drive (VFD) Device used to vary the speed of an electric motor. For building HVAC, VFDs are purchased to achieve energy savings by taking advantage of the Affinity Laws.To achieve energy savings we will look at loads, such as pumps, blowers, and cooling towers. Device used to vary the speed of an electric motor. For building HVAC, VFDs are purchased to achieve energy savings by taking advantage of the Affinity Laws. To achieve energy savings we will look at loads, such as pumps, blowers, and cooling towers. Includes built-in motor protection Adjustable to the motor specifications. Adjustable to the motor specifications. Adjusts both the frequency & voltage to the motor Reduces the inrush current to 115% (pumps and fans) of the motor rated current, possibly reducing Peak Demand Charges.

The VFD starts the motor by applying a low frequency AC waveform to the motor and slowly ramping it up to the desired frequency. Remember, AC Frequency=Motor Speed. The VFD starts the motor by applying a low frequency AC waveform to the motor and slowly ramping it up to the desired frequency. Remember, AC Frequency=Motor Speed. Therefore, a major benefit of VFDs is controlled acceleration and deceleration. This can help in a variety of ways. Instead of attempting to immediately jump to full speed, the motor can now smoothly come up to speed in an user adjustable time period. This can eliminate the shocks which are often associated with starting motors. Extended belt, coupling and motor life is the benefit gained. Variable Frequency Drive Start

Types of Loads Loads can be grouped into two basic categories: Constant Torque Loads s s Load does not change with speed s s Industrial loads like presses, conveyors, extruders, compressors, mills, etc. We buy VFDs for these applications to control the process, Not to save energy. Variable Torque Loads (Energy Savings Potential!) s s Load changes with speed s s HVAC, pumps and fans on industrial processes

Drives (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.

How did we control FLOW before Variable Frequency Drives? Dampers & Valves (very inefficient) Air Dampers & Valves limit flow by placing a restriction in the system. Most HVAC pumps and fans do not shut down when the system is satisfied. Imagine pressing the accelerator of your car to the floor and trying to slow the car down by pressing the brakes at the same time…wasteful!

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 = RPMs HP= (RPMs)³

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. n n FLOW=SPEED Torque Horsepower Spring Fall Winter Summer A 10% reduction in speed = 27% reduction in power!

Central Utilities Plant Operating since 1924

Steam Turbine Cogeneration

Cogeneration Project Schematic

New Boiler Installed 2006

Forced Draft Blower 500 HP

Original Inlet Damper Control

Problems with Existing Application n & full boiler capacity n Inability to maximize the capabilities of the FD-fan motor & full boiler capacity n n Damper control prevented the boiler from performing as designed and operating efficiently during the shoulder months of spring and fall. n & high speed n Vibration and noise was created in the vicinity of the FD fan because of poor air-path conditions & high speed

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

The Proof is in the Figures BEFOREAFTER Cogeneration-plant 50-day electricity consumption 383,087 kwh 217,000 kwh Cogeneration-plant 50-day steam production 141,093,563 lb 139,988,998 lb Vibration 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 FactorPoorExcellent

Benefits of the VFD installation n Finally achieve full capacity rating. n Precise and efficient control of the No. 9 boiler through the full span of its production rating. Finally achieve full capacity rating. n n The motors average speed is about 45 Hz, which has reduced maintenance, vibration, and ambient noise. Damper was removed! n n Motor runs cooler, its lifespan, along with the operating life of the FD fan and associated equipment, will be increased n Power factor improvement n Reduction in Peak Demand Load

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.

Central Utilities #9 Boiler Cogeneration Upgrade The Savings500hp 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.

How does this Green Technology Really make you $GREEN$? n VFDs save money due to the application of pumps, and fans following the Affinity Laws. HP=Speed cubed n The cost of electricity has, and will increase n The cost of VFD has decreased due to matured technology n VFDs reduce Maintenance costs, & extend equipment life span n Using VFDs greatly reduces energy consumption, hence it is called environmentally GREEN technology…I like to say it puts $GREEN$ in your pockets!