How to Use Your Existing SCADA for Energy Management
Don Best, HDR Engineering, Inc.
Presentation Outline
• Energy Management• Connect a Power Meter to SCADA• Understand Your Electric Bill• Energy Benchmark Studies• SCADA for Energy Conservation
Energy Management
• Process of monitoring, controlling, and conserving energy:– Metering your energy use and collecting the data– Finding opportunities to save energy
• Energy Conservation Measures (ECM’s)• Perform an Energy Audit
– Taking action to target the opportunities• Start with the “energy hogs”
– Tracking your progress
Energy Management
• Benefits of using SCADA for Energy Management:– Tracking and trending– Baseline energy use calculations– Information accessible to operators
Energy Management
• Energy Costs are a large portion of the O&M costs of a typical WWTP facility:
• Staffing 46%• Energy 28%• Solids 12%• Others 07%• Chemicals 04%• Maintenance 03%
Power Monitoring
Digital Power Meter (Eaton IQ Analyzer)
Power Monitoring
• Digital Power Meter Parameters: Line CurrentsL-L and L-N VoltagesPower (Watts)Energy Use (Watt-hours)VA and VARsPower Factor Demand (Watts, VA, VARs, Currents)Frequency (Hz)Total Harmonic Distortion (%THD)
Power Monitoring
• Power Meter to PLC/SCADA:– Analog Signals (4-20ma)– Pulsed Output Signal (one pulse per kWh)– Digital Communications:
• Serial: Modbus, Profibus, DeviceNet• Ethernet: Modbus TCP/IP, Ethernet/IP
Power Monitoring
Power MonitoringkW
7-Day Period
Power Monitoring
• Calculate daily, weekly, monthly energy use• Calculate “Unit Energy Consumption”
kWh/MGEnergy used per million
gallons of wastewater treated.
Electric Costs
• Electric Utility Bill:– Energy Use Charges (kWh)– Demand Charges (kW)
• Transmission (monthly demand)• Distribution (monthly demand)• Distribution Facilities Capacity (facility demand)
Electric Costs
• Portland General Electric:– Monthly Demand:
• Is based on the highest power requirement, averaged over any half-hour period during the billing cycle, measured in kW.
– Facility Capacity:• The average of the two highest monthly demand kW for
the last 12 months.
Electric Costs
• City of Newberg, OR WWTP– Oxidation Ditch-Type, Activated Sludge (1987)– Capacity: 4 MGD dry / 20 MGD peak– April 2010 Data:
• Total kWh: 316,604• Total Flow: 131 MG• 2,417 kWh/MG
(Unit Energy Consumption)
Electric Costs
• City of Newberg, OR WWTP– April 2010 Portland General Electric Bill
Energy Use (kWh): $20,145Transmission Charge: $506Distribution Charge: $1,426Distribution Facility Charge: $1,580Others: $1,740Total Charges: $25,397
} Demand Charges(14%)
Energy Benchmark Studies
Compare your plant to energy benchmark studies:
Energy Benchmark Studies
• Each wastewater plant is different:– Plant flow/loading requirements– Treatment level requirements– Type of treatment
• Trickling Filter, Oxidation Ditch– Type of process equipment
• UV Disinfection, Hypochlorite Generators– Size of plant (economy of scale)
Energy Benchmark Studies
Treatment Type kWh/MG
Trickling Filter 950
Activated Sludge 1,300
Advanced Treatment 1,500
Advanced Treatment with
Nitrification1,900
Oxidation Ditch 2,900
National Average Energy Use by Treatment Type
Energy Benchmark Studies
PG&E Study of 13 WWTP’s in CA
Wastewater Treatment Plants
Ave
kW
h/M
G
Ave Energy Use:2,243 kWh/MG
45% of Energy Usefor Secondary TreatmentProcess
Energy Benchmark Studies
SCADA for Energy Conservation
• Automated DO Controls:
SCADA for Energy Conservation
• Automated Controls for VFD’s:– PID Loop Control: Flow, Level, Pressure
• Monitor Motor Currents:– or Power to motor
SCADA for Energy Conservation
• Motor Starter with “Smart Overloads”:
Provides Motor Current DataLocated in MCCNetworked (DeviceNet)Offers Better Diagnostic Information
SCADA for Energy Conservation
• Manage Motor Inrush Currents (Demand):– Large Motor Loads:
• Stagger Start– Pump Rotation:
• Stop a pump before starting another.
SCADA for Energy Conservation
• Monitor Lift Station Operations:– Daily Pump Start Counts– Daily Pump Run Times– Average Run Time per Start
Look for Signs of Clogging or Faulty Pumps
SCADA for Energy Conservation
• Fine Tune Pump Controls to Improve Efficiency:– Look for conditions where two pumps
are running together at low speeds.– Give priority to your most
energy efficient pumps.
SCADA for Energy Conservation
• Automate the Plant Water System:– Many systems are still manually controlled– Use local Booster Pumps where high pressure is needed– Use solenoid valves for chemical dilution water
• Monitor Mixing Air Flows:– Grit Chamber, Chlorine Contact Basins
• Anaerobic Digesters:– Mixing, Recirculation, and Sludge Heating
SCADA for Energy Conservation
• Power (kW) Alarm Setpoint
(ALARM)
SCADA for Energy Conservation
• Can Loads be Shifted to Off-Peak Hours?– WAS or Sludge Transfer Pumps– Hypochlorite Generators– Sludge Thickening / Dewatering
Summary
• Use Your SCADA System to Help Plant Staff:– Monitor Energy Use– See Results of Energy Conservation Measures– Look for Faulty/Abnormal Conditions– Optimize the Process Controls– Run a More Efficient Plant