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Electrical Efficiency LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices. Electrical Efficiency Electrical Power: the rate at which electrical energy is produced or used. -measured in Watts (W)

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Presentation Transcript
slide1

Electrical Efficiency

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide2

Electrical Efficiency

Electrical Power: the rate at which electrical energy is produced or used.

-measured in Watts (W)

-one Watt is equal to one Joule of energy used per second

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide3

Electrical Efficiency

Electrical Power: the rate at which electrical energy is produced or used.

-measured in Watts (W)

-one Watt is equal to one joule of energy used per second

e.g. 100 W light bulb uses four times as much energy per second as a 25 W bulb.

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide4

Electrical Efficiency

kilowatt-hour (kWh): the SI unit for measuring electrical energy usage

-1 kWh is the use of one killowatt of energy for one hour

-3 600 000 times as much energy as 1 Joule

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide5

Electrical Efficiency

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide6

Electrical Efficiency

Efficiency: comparison of the energy output of a device with the energy supplied

e.g. Clothes dryers

-older clothes dryer uses 800 kWh per year

-new clothes dryer uses 300 kWh per year

-they both do the same job so the new dryer is more than twice as efficient

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide7

Electrical Efficiency

Calculating efficiency of a Device:

percent efficiency = energy out x 100%

energy in

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide8

Electrical Efficiency

Calculating efficiency of a Device:

percent efficiency = energy out x 100%

energy in

short form:

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide9

Electrical Efficiency

Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide10

Electrical Efficiency

Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.

Given: Eout = 35 J

Ein = 100 J

Unknown: % efficiency

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide11

Electrical Efficiency

Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.

Given: Eout = 35 J

Ein = 100 J

Unknown: % efficiency

Eout

Select: % efficiency = _____ x 100%

Ein

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide12

Electrical Efficiency

Example: A light bulb uses 100 J of energy and produces 35 J of light energy. Calculate the energy efficiency of the light bulb.

Eout

Select: % efficiency = _____ x 100%

Ein

Solve: % efficiency = 35 J_ x 100%

100 J

=35%

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide13

Electrical Efficiency

Try this: A toaster oven uses 1200 J of energy to produce 850 J of thermal energy. Calculate the efficiency of the toaster oven.

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide14

Electrical Efficiency

Try this: A toaster oven uses 1200 J of energy to produce 850 J of thermal energy. Calculate the efficiency of the toaster oven.

Given: Eout = 850 J Ein = 1200 J

Unknown: % efficiency

Select: Eout

% efficiency = _____ x 100%

Ein

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide15

Electrical Efficiency

Try this: A toaster oven uses 1200 J of energy to produce 850 J of thermal energy. Calculate the efficiency of the toaster oven.

Solve: % efficiency = 850 J x 100%

1200 J

= 71%

therefor the toaster oven is 71% efficient

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide16

Electrical Efficiency

Cost of Operating Electrical Devices:

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide17

Electrical Efficiency

Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide18

Electrical Efficiency

Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.

Given: power = 75 W

= 0.075 kW

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide19

Electrical Efficiency

Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.

Given: power = 75 W

= 0.075 kW

time = 24 hours per day for 365 days

= 8760 hours

cost = 5.6¢/kWh

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide20

Electrical Efficiency

Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.

Unknown: cost to operate

Select: cost to operate = power x time x cost of

used electricity

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide21

Electrical Efficiency

Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.

Unknown: cost to operate

Select: cost to operate = power x time x cost of

used electricity

Solve: cost to operate = 0.075 x 8760 x 5.6

= 3679¢ ($36.79)

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide22

Electrical Efficiency

Example: a laptop computer uses a 75 W adapter when it is plugged in. Electricity costs 5.6¢/kWh. Calculate how much it would cost to operate the laptop for 1 year for 24 hours per day.

Unknown: cost to operate

Select: cost to operate = power x time x cost of

used electricity

Solve: cost to operate = 0.075 x 8760 x 5.6

= 3679¢ ($36.79)

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide23

Electrical Efficiency

Try this: Calculate the cost of operating a 1500W hair dryer to dry your hair for 6 minutes per day for 3 days. The cost of electricity is 5.6¢/kWh

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide24

Electrical Efficiency

Try this: Calculate the cost of operating a 1500W hair dryer to dry your hair for 6 minutes per day for 3 days. The cost of electricity is 5.6¢/kWh

Given: power = 1500 W

= 1.500 kW

time = 6 minutes per day for 3 days

= 6 min x 3

= 18 min = 0.30 hours

cost = 5.6¢/kWh

Unknown: cost to operate

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices

slide25

Electrical Efficiency

Try this: Calculate the cost of operating a 1500W hair dryer to dry your hair for 6 minutes per day for 3 days. The cost of electricity is 5.6¢/kWh

Select: cost to operate = power x time x cost of

used electricity

Solve: cost to operate = 1.500 x 0.30 x 5.6

= 2.52¢

LG: to understand how energy efficiency is calculated & use it to determine energy efficiency of household electrical devices