Efficient Variable Speed Pumping: A Low Cost Approach to Green Energy

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Reginald Mathews
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1 Efficient Variable Speed Pumping: A Low Cost Approach to Green Energy MICHIGAN WEA 2017 Wastewater Administrators Conference (WWAdCon) Jan. 26 & Presented by Gary Patterson Technical Specialist: Pumps, Fans Compressors

2 Concern over climate change is driving some energy users to find ways to reduce or eliminate emissions of greenhouse gases, most notably CO2. Rob Atkins Getty Images, Time, Dec. 17, Warmest year on record

3 Energy Consumption in WWTP UIC.edu

4 Typical WWTP Power Sources Renewable, non-carbon sources have made progress

5 Reducing emissions need not be costly! Nearly 50% of electricity-related emissions from the global wastewater sector could be abated at negative cost by investing in readily available technologies. Powering the Wastewater Renaissance, published online by Xylem Inc.

6 Greenhouse Gas Equivalencies 1 kw-hr Electricity = 1.5 pounds of Carbon Dioxide Equivalent from coal-fired power plant 1.7 miles driven by average passenger car

7 Performance curves at various pump speeds

8 Benefits of variable speed pumping Finite control of flow as conditions vary Pump mechanical wear reduced (bowl, impeller) Bearing life increased Seal life increased Reduced noise Reduced vibration Omit throttling valve (or reduce wear) Eliminate water hammer Reduced cycling on/off Reduced energy consumption

9 Percent horsepower Pump Affinity Laws 100% 90% 80% Pump load HP a RPM 3 Pump brake horsepower varies approximately as the cube of speed. 70% 60% 50% 40% Normally speed reduction limited to 70% or higher 30% 20% 10% 0% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent Speed

10 Variable Speed eddy current drive vs. Throttled Discharge Life Cycle Cost Comparato Duty Cycle System Data Flow % Time Name Sacramento Example 10% 0% Type Pump Choose from drop down list 20% 0% Flow Control VFD w/ A/C Choose from drop down list 30% 0% Life Cycle Analysis 30 years [Default is 40] 40% 0% 50% 5% Motor Data Driven Load Data 60% 15% HP 500 BHP 475 Default is 95% of HP 70% 30% RPM 900 Max. RPM % 30% Efficiency 94.2% Min. speed 62 % [Default is 75%] 90% 15% Volts % 5% Flow, not rpm! 100% Presumed to be same for all methods Total must =100 35% 30% 25% 20% 15% 10% 5% 0% Percent Flow Drive and Installation Data Hours of Operation Incentive Drive Selection Dynamatic VFD VFD w/ A/C Hours per Day 12 Utility Rebate Drive Cost $ 175,000 $ 215,000 $ 265,000 Days per Week 7 One Time $ - Install Cost $ 40,000 $ 40,000 $ 40,000 Weeks per Yr. 52 Annual $ - Rebates $ - $ - $ - Net Cost $ 215,000 $ 255,000 $ 305,000 D Cost $ (40,000) $ - $ - Summary of Energy Results VFD, no Air Conditioning VFD with Air Conditioning Throttled Valve kwhr/yr Energy $/yr kwhr/yr Energy $/yr kwhr/yr Energy $/yr Dynamatic 1,345,935 $ 107,675 Dynamatic 1,345,935 $ 107,675 Dynamatic 1,345,935 $ 107,675 Without A/C 1,307,688 $ 104,615 VFD with A/C 1,442,482 $ 115,399 Valve Control 1,560,031 $ 124,802 Annual Saving (38,247) ($3,060) Annual Saving 96,547 $ 7,724 Annual Saving 214,096 $ 17,128 C

11 Results displayed graphically kwh per year Thousands 2,000 1,800 1,600 1,400 1,200 1, Dynamatic vs. VFD, no A/C VFD no A/C Dynamatic Percent Flow kwh per Year Thousands 2,200 2,000 1,800 1,600 1,400 1,200 1, Dynamatic vs. VFD with A/C VFD w A/C Dynamatic Percent Flow kwh per year Thousands 1,800 1,600 1,400 1,200 1, Dynamatic vs. Bypass Valve Bypass Dynamatic kwh per year Thousands 1,800 1,600 1,400 1,200 1, Dynamatic vs. Throttled Valve Throttled Valve Dynamatic Percent Flow Percent Flow

12 Proposed Project Payback Spreadsheet Life Cycle and Payback This tool compares total cost of ownership for various flow control strategies. Line items are based on: Enter Customer Data in Green Cells Analysis for 30 years Pump Life Cycle Costs: A guide to LCC Analysis for Pumping Systems, published 2001 by Hydraulic Institute and Europump Calculated data appears Blue Cells Motor, Pump costs are presumed to be the same, and thus not compared in these calculations Analysis presumes a pre-existing valve-based flow con Dynamatic VFD VFD w/ A/C Throttled Valve Choose type Initial Capital Costs Lifetime Lifetime Lifetime Lifetime Including purchase price, aux. services Equipment Purchase $ 175,000 $ 215,000 $ 265,000 $ - Enter cost dat Installation, commissioning, training Installation Costs $ 40,000 $ 40,000 $ 40,000 $ - system is to b Brick/mortar mods to accommodate eqpt. Construction Costs $ - $ 60,000 $ 85,000 $ - Calculated as 10% of above costs Engineering $ 21,500 $ 31,500 $ 39,000 $ - Initial inventory of spares Spare Parts $ 10,000 $ 30,000 $ 30,000 $ - End of life disposal (15% of Initial Cost) Decommission Cost $ 26,250 $ 32,250 $ 39,750 $ - Total Initial Cost $ 272,750 $ 408,750 $ 498,750 $ - Annual Costs Per yr. Yrs Lifetime Per yr. Yrs Lifetime Per yr. Yrs Lifetime Per yr. Yrs Lifetime From System Info results x years of service Energy Costs $ 107, $ 3,230,245 $ 104, $ 3,138,451 $ 115, $ 3,461,957 $ 124, $ 3,744,074 Labor for normal operation & supervision Operating Costs $ 1, $ 45,000 $ 1, $ 45,000 $ 1, $ 45,000 $ 1, $ 45,000 Routine and predicted maintenance Mainenance $ 1, $ 45,000 $ $ 15,000 $ $ 15,000 $ 1, $ 36,000 Total Annual Costs $ 110,675 $ 3,320,245 $ 106,615 $ 3,198,451 $ 117,399 $ 3,521,957 $ 127,502 $ 3,825,074 Recurring Costs (not annual) Per event Events Lifetime Per event Events Lifetime Per event Events Lifetime Per event Events Lifetime Loss of production Down Time Cost $ 1 2 $ 2 $ 1 2 $ 2 $ 1 2 $ 2 $ 1 2 $ 2 Contamination from pumped liquid Environmental Cost $ 2 4 $ 8 $ 2 4 $ 8 $ 2 4 $ 8 $ 2 4 $ 8 Repairs in excess of routine maintenance Repair Cost $ 10,000 3 $ 30,000 $ 15,000 3 $ 45,000 $ 20,000 3 $ 60,000 $ 15,000 4 $ 60,000 Cost to replace failed, obsolete eqpt Eqpt Replacement $ 295,000 0 $ - $ 351,000 2 $ 702,000 $ 421,000 2 $ 842,000 $ 50,000 1 $ 50,000 Total Life Cycle Costs $ 3,623,005 $ 4,354,211 $ 4,922,717 $ 3,935,084 ROI/Payback Calcs Dynamatic VFD VFD with A/C Total Initial Cost (investment) $ 272,750 $ 408,750 $ 498,750 Initial Annual Savings (Energy, Operating, Maintenance) $ 16,828 $ 20,887 $ 10,104 Initial Simple payback (years) Initial Simple Return on Investment 6.17% 5.11% 2.03% Life Cycle Cost Savings $312,080 ($419,127) ($987,633) Annual Return on Investment over Life Cycle (dollars) $10,403 ($13,971) ($32,921) Annual Return on Investment over Life Cycle (percent) 3.81% -3.42% -6.60%

13 Available Motor Speeds AC Squirrel Cage Induction Motors Synchronous Speed = (120 x 60)/ no. of poles (pairs only) 2 Pole 3600 rpm 4 Pole 1800 rpm 6 Pole 1200 rpm 8 Pole 900 rpm 10 Pole 720 rpm 12 Pole 600 rpm 14 Pole 514 rpm minus about 1% slip

14 Variable Speed Options Variable frequency AC drives Eddy Current Drives Two-speed AC induction motors Wound Rotor AC Induction motors Fluid Couplings Rare earth permanent magnet drives Variable Pitch Sheaves

Variable Frequency AC Drives Fractional to Unlimited Horsepower Low and Medium Voltage Since 1970s Wide variety of configurations Improved over the years, but still

15 Variable Frequency AC Drives Fractional to Unlimited Horsepower Low and Medium Voltage Since 1970s Wide variety of configurations Improved over the years, but still occasionally problematic Converts AC line power to DC, and then reconstructs power to simulate sinusoidal AC power at adjustable frequency and voltage Probably the most common solution

16 Eddy Current Drives Fractional to 10,000 hp Suitable for low and medium voltage motors Since 1930s Horizontal, Vertical designs Air cooled, water cooled available Long-lived, very reliable Simple to diagnose and repair No conversion of electrical power Transmits adjustable torque from a constant speed AC motor

18 Two Speed Induction Motor Relatively Inexpensive Two connections required (essentially two starters) Limited to specific speeds and combinations Adjacent pole combinations can be very practical 2 Pole 3600 rpm 4 Pole 1800 rpm 6 Pole 1200 rpm 8 Pole 900 rpm 10 Pole 720 rpm 12 Pole 600 rpm 14 Pole 514 rpm

19 Wound Rotor Induction Motor Available to thousands of HP Available for low and medium voltage Common in 1950s to 1970s Generally expensive motor and control Special starting requirements Requires controlled resistance in rotor circuit, via slip rings and brushes Liquid Rheostat Step Resistor Banks Slip Power Recovery System (electronic frequency and voltage conversion)

20 Wound Rotor Induction Motor

Fluid Drives Available 100 to several thousand horsepower Hydrostatic unit interposed between motor and load Driven at constant speed by AC

21 Fluid Drives Available 100 to several thousand horsepower Hydrostatic unit interposed between motor and load Driven at constant speed by AC induction motor Slip loss characteristic proportional to percent speed Long lasting Can be high maintenance (oil leakage, oil contamination)

22 Rare Earth Magnet Technology Rare Earth Magnet ASD Introduced in 1999 Common trade name is MagnaDrive Received recognition as a competitor to Variable Frequency Drives due to reduced energy consumption Transfers torque across the air gap using magnetic force

23 Variable Pitch Belt Drive More adjustable than variable Limited to relatively small horsepower Often manually adjustable only Commonly called Reeves Drive

24 Thank you!

AR No. # - Install (Belt Type Here)

AR No. # - Install (Belt Type Here) Recommendation INSERT RECOMMENDED ACTIONS HERE. The use of notched v-belts will reduce motor energy use by 2.1% on average through improved transmission efficiency.