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Pump/Motor Control Cost Versus Control

Pump/Motor Control Cost Versus Control. Pump/Motor Control Cost vs. Control. In the beginning… Technology vs. improvement Utility costs – Rate structures Costs associated with control Design process, Control Elements Decision making process Effects on other parts of the system. Genesis.

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Pump/Motor Control Cost Versus Control

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  1. Pump/Motor ControlCost Versus Control

  2. Pump/Motor ControlCost vs. Control • In the beginning… • Technology vs. improvement • Utility costs – Rate structures • Costs associated with control • Design process, Control Elements • Decision making process • Effects on other parts of the system

  3. Genesis • “I don’t see why we need all this computer stuff.”

  4. Old Technology • Very inefficient • Unreliable • Weak link in the overall system • Safety hazard • Limited knowledge base

  5. Technology vs. Improvement • Does the new technology really help? • Bang for buck • Has your system really improved?

  6. Penny Wise – Dollar Foolish

  7. Moral of the story • Think through decisions – What is required? • Isolation transformer or line/load reactor • The right tool for the job • Isolation transformer

  8. Simple Energy Costs • The 100 Watt light bulb • Incandescent, $0.50, lasts 1000 hours, cost $0.01 per hour - $5 (for 10 bulbs) + $100 • = $105 to operate for 10,000 hours • Fluorescent, $10, lasts 10,000 hours, cost ¼ cent per hour • $10 + $25 = $35 to operate for 10,000 hours • Not to mention other factors such as heat loss

  9. Utility Costs • Billing rate structures • Time of day billing • Energy charges • Demand charges • Power factor penalty • Hatchet and ratchet clauses • Interruptible service • Incremental cost

  10. Typical Time-Of-Date Rate Structure • Demand Charge • Period 1 $6/kW • Period 1 $6/kW • Period 1 $6/kW • Period 1 $6/kW • Energy Charge • Period 1 $0.60/kWh • Period 1 $0.54/KW • Period 1 $0.60/KW • Period 1 $0.45/KW

  11. Periods Defined • Period #1 - 1 p.m. to 7 p.m. Monday through Friday, June 1 through September 30 • Period #2 - 8 a.m. to 1 p.m. and 7 p.m. to 11 p.m. Monday through Friday , June 1 through September 30 • Period #3 - 8 a.m. to 11 p.m. Monday through Friday, October 1 through May 31 • Period #4 - 11 p.m. to 8 a.m. Monday through Friday all weekend hours all months

  12. Alternative Fuels • Electricity • Residential $0.09 / kWh $26.37 / 1M BTU • Commercial $0.072 / kWh $21.10 / 1M BTU • Industrial $0.616 / kWh $18.05 / 1M BTU • Natural Gas • Residential $0.60 / CF $6 / 1M BTU • Comm/Ind $0.45 / CF $4.5 / 1M BTU

  13. Design Process – Control Elements • Design/Engineering stage – understand your goals AND the costs associated with decisions - SCP • Controllers • Type • SCADA • Control valve • Variable frequency drives

  14. Specifying Control Valves • Type of valve • Valve trim & inherent characteristics • Type of actuator • Material of construction for wetted parts • Accessories • Location • Benefits – Positive shut off

  15. Specifying VFD’s • Usually easier than valves • Type of motor and load • Type of VFD • Benefits – status feedback, etc.

  16. Costs Associated with Control • Initial costs, installation • Operating and maintenance • Training • Other costs associated with other systems • Which is most important?

  17. Installed Comparison • Purchase price of VFD (less than 10 HP) typically higher than 1” – 2” Carbon steel control valve • After installation costs, equal or even less expensive • Bypass valves • Air piping • Conduit • Cable • Labor

  18. Decision making • Control Valves • Using across the line starters • Type of control is flow restriction – car/brake • Backup/Redundant control • Environmental and location • VFD’s • Bypass starters, backup control • Type of control is flow – car/accelerator • Environmental and location – distance (reflective waveform results in voltage doubling)

  19. Quantify Results

  20. Quantify Results VFD’s – Cost

  21. Effects On System • Motor bearing life • Impeller wear • Generator sizing • System piping/lower pressures/water hammer • Mean time between failure

  22. Effects On Other Systems • HVAC system • Indoor/Outdoor structures • Noise • Size of enclosures • Precision control

  23. Affinity Laws • Flow is directly proportional to Speed • Pressure is proportional to the Square of Flow(Speed) • Power is proportional to the Cube of Flow(Speed) • i.e. Pump operated @ 90% @ nominal speed • Capacity will be 90% • Head will be (.9) squared or 81% • BHP will be (0.9) cubed or 72.9% • Therefore – a 10% reduction in speed = a 27.1% reduction in BHP

  24. Why Use VFD’s over ATLS’s • Energy savings • Reduced mechanical stress • Eliminate power surges/in-rush current • Better process control • Installed bypass for backup • Instantaneous over-current protection • Over-voltage protection

  25. Why Use VFD’s • Better Motor Protection • Brown out or under voltage protection. If you have a brown out the motor will burn up unless you have this built in somewhere else in the system. • Power factor correction!! You are looking at .97 or better power factor. Standard motor is in the .85 to .9 area at full load. • Output phase protection • Input phase protection • Short Circuit protection • Ground Fault protection. • Phase Rotation

  26. Pumping Systems • Dual-Simplex Systems - Two Drives, Two Motors Logic AFD AFD M M

  27. Pumping Systems • Duplex System – One Drive w/ Multiple Motors Logic AFD M M

  28. Power Consumption Comparison

  29. Results $$$ • A pump operating 30% below the free system flow rate consumes 61% less power (13.53 kW) than by throttling it to the same flow rate. If the pump operates at this level only 25% of the time in a 24-hr. shift for 250 days per year when power cost is 6 cents per kW-hr, the savings would be about $1,217 per year. If the pump also had to overcome 60 ft. of static head (47% of the total head), the savings would be $941 per year .

  30. Big Picture • Ultimate goal • Think in terms of sustained operation • Many different kinds of systems • How Does this fit into the entire system?

  31. SUPPLY AIR BOILER CHILLER RETURN AIR OVERVIEW OF BUILDING SYSTEMS Cooling Tower Hot Water Pump CW Pump Condenser Water Pump

  32. Typical Lift Station

  33. Chemical Stripper System

  34. Pump/Motor ControlCost Versus Control • Wrap up • Existing systems • Removing old equipment – Retrofit • Space, existing power systems, etc. • New construction • Include energy saving systems • Include instrumentation to prove it • Report it

  35. Pump/Motor ControlCost Versus Control • Utilize multiple resources for decision making • Engineering firms • Reference Books from ISA • Variable Speed Drives: Principles and Applications for Energy Cost Savings • VFD manufacturers, valve manufacturers

  36. Pump/Motor ControlCost Versus Control • Sell the project to the right people • Present your case well • Have a master plan laid out • Leave a legacy

  37. Pump/Motor ControlCost Versus Control • Thanks for your valuable time! Questions or Comments to share

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