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Power Factor:Causes, Costs, Case Study

Michael Wrinch, P.Eng.(Canada)

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Power Factor Agenda

• Background on Electricity

• What is Power Factor?

• What it can cost you

• How it effects your buildings

• How to fix it

• Case Study

• Software Demo

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Electricity It’s Like Traffic on a long road

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Electricity BasicsRoad

Wire

Speed

Volts

V

Cars

Amps

A

Traffic

Watts

W

* on =

Traffic per hour

Watt-hour, Wh

An amp is a measurement of many electrons

per second!)

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Traffic and Toasters

V*A=W

• Drive too fast: Car Crash (sparks)

• Too many cars = A crash. We prevent it by: __________

EXAMPLE: Take a Toaster – 1000 W, Plug Voltage is 100 V, running for 1 hour.

How many Watt-hours (Wh) of Energy ? ______________

How many Amperes (A) of current ? ______________

Bigger Roads/

(Wires)

1000 Wh or 1 kWh

1000/100 = 10 A

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Unfortunately,

this is not completely true….

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Electricity Is MORE like traffic in a City !

Flow (Amps) is delayed from speed (Volts) by city traffic lights etc.(motors) the delay is a utilization of energy with no work – it is called “imaginary”, Reactive Power or VARs.

The total of Watts and VARS is called APPARENT POWER or VA. They are related by: 22 VARWVA

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Apparent PowerRoad

Wire

Speed

Volts

V

Cars

Amps

A

City Traffic

Apparent Power

VA

Traffic per hour

is still: Watt-hours (Wh)(We use expensive energy meters to figure this out)

* on =

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Traffic and Fans/Motors make VARs

• Most Common Sources of VARs: Motors (ie:Fans/HVAC), and Computer power supplies.

• VARs are BAD because they increase the amps but they produce no real work ! (i.e. cars are now stuck in traffic revving engines but not moving, (Do we need to make the road bigger? OR Fix the traffic lights?)

• So: V*A=W is now: V*A=VA –> Apparent Power

• EXAMPLE: Take a Fan – 1000 VA, 900 W, Plug Voltage is 100V, running for 1 hour.

• How many Watt-hours (Wh) of Energy ? ________ ??900 Wh

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Power Factor – making power Super easy!

• POWER FACTOR (PF) was created

so power engineers do not have to think much!

• Power factor is the ratio of Watts to Apparent Power or: PF=W/VA.

• EXAMPLE: If a Fan delivers 100 W

and uses 120 VA,

the Power Factor is: 100/120 = 0.833.

• SIMPLIFYING: Turn VA, VAR and

W into one number ! PF

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Why a Low Power Factor is a BAD Thing

Low Power Factor (PF) will force you and the Utility to upgrade power lines to bigger wires. The Utility charges their customers for low power factor. EXAMPLE:

W VAR VA pf V A% Inc.

of A

100 0 100 1 1 100 100%

60 117 0.86 1 116.6 117%

120 156 0.64 1 156.2 156%

180 206 0.49 1 205.9 206%

Wow!

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Why Would You Have a PF Issue?

• Competitive bidding: will commonly leave out power factor correction kits as it adds to the cost of construction (and your monthly power bill).

• Building Improvements: may not take into consideration the additional VARs. Examples include heat pumps and geothermal upgrades

• Old buildings: with malfunctioning, inappropriate or non existent power factor correction systems.

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How Do You Know if You Have a Problem?

• It will show up on your electricity bill as “Power Factor Charges”.

• Charge Examples:

– BC Hydro: penalty charge on monthly PF average. Penalty ranges from 2% to 80% of your kWh charge. Starting at PF less than 0.9.

– California PG&E: charges on monthly PF average. Ranging from +1% credit to a -2.1% penalty of your kWh charge. Penalty starts at PF less than 0.85.

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Case Study: Community Center

• New community center on British Columbia coast

• Yearly energy bill: $100,000

• Power Factor averaged: 0.70 resulting in 24% penalty charge (approximately $20,000/yr)

• Using Pulse Energy Management System to view the real time demands, a $10,000 power factor correction kit was specified and installed.

• Payback period of 6 months.

• NPR over 25 yrs of $390,000 !

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How You Can Identify and Correct for PF

1. Identify if you have a power factor issue by looking at your energy bills.

2. Power Factor charges greater than $100/month are worth addressing

3. In Pulse Software, Create a power factor and a kVAR chart.

4. Show this to an Electrical Contractor who will then work with you to select the right size of power factor correction kit.

– The kit size is typically 75% the maximum kVARs and ordered as a static or variable size. A static power factor correcting kit poses a risk of over correcting which can damage a building – use variable.

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Example - Software

MAX Power = 130 kW

MIN Power = 50 kW

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Example - Software

MAX Power = 130 kW

MIN Power = 50 kW

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Example - Software

MAX PF = 0.81

MIN PF = 0.6

Average PF = 0.71

Penalty Range:

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Example - Software

MAX kVAR = 90

MIN kVAR = 50

Solution: Variable PF correction

kit: 80,60,40,20 kVAR steps.

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Summary • Watt-hrs are the amount of watts used for one hour

and we pay for kWatt-hours (kWh = 1000 watt-hrs)

• VARs are caused by motors, HVAC, and computers and cause excessive current in power lines.

• Low PF: can result in costly penalties seen on your electricity bill. Caused by excessive VARs.

• PF: can be corrected with the right tools and can reduce energy bills typically around 24% !

• Pulse Energy Management Software is an effective tool for identifying VARs and managing your day to day energy.

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Thank you! Additional questions?

Contact Pulse Energy at: 1-877-331-0500 or at info@pulseenergy.com

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