LAST SECTION OF CHAPTER 12AND OF

THE ENTIRE ELECTRICITY UNIT

Reducing Our Electrical Energy Consumption

Answer Key – Quiz

Think – Pair – Share

THINK Think of how many times each day and in how many

different ways you use electricity. Jot these ideas down!!

PAIR Turn to the person(s) beside you and quietly discuss your

ideas from the THINK portion. Put a check mark beside the ones you both thought of, and

add the new ideas you didn’t think of.

SHARE Share your ideas with the class!!

The Cost of Electricity

Each time you plug in an appliance, turn on a switch, or use electricity in any way, you are using precious resources and spending money.

To make better choices about how you use electricity, you need to understand where, when, and how you use it!

The Cost of Electricity

Electricity Meters Tracks how much electricity is tapped from the energy

grid x

Older model – has a turning disk with a black band; the more electricity you use, the faster the disk turns; dials are read monthly

‘Smart’ model – records consumption hr by hr and send info wirelessly to the utility; costs are calculated according to time of use

The Cost of Electricity

Cost is higher during ‘peak’ hours

These are the busiest times of day

You can save $$$$$$$$$ by moving activities that take a lot of energy to off-peak hours

You can save resources by reducing your USE of electricity at all times of day

Electrical Energy Consumption

Electrical Energy Consumption – the amount of electrical energy a household uses Usually measured in kilowatt-hours

Kilowatt-hours – kW•h; equivalent to the use of one kilowatt in one hour Ex: If the energy, E, used by a microwave oven is 0.8kW

and the oven is turned on for ½ an hour, the electrical energy used is:

E = (0.8kW)(O.5h) = 0.4kW•h

One kilowatt equals 1000 watts One watt equals 1 joule per second

Electrical Energy Consumption

Calculating the cost of using an electrical device Multiply the energy consumed (in kW•h) by the cost

(PER kW•h) Ex: Using the microwave example, the consumption of

0.4kW•h at a cost of 8 cents per kW•h:Cost = (0.4 kW•h)(8cents/ kW•h) = 3.2 cents

*******this doesn’t sound like much, but it’s only ONE event at ONE time there is also an electricity delivery charge and taxes ON TOP of the actual energy charge *******

Learning Checkpoint

Copy and complete this chart on your paper. Calculate the cost of using each appliance over the course of a year. Use a utility charge of 8.5 cents per kW•h.

ApplianceAverage Use

(hrs/day)

Annual Energy

Consumption (kW•h)

Annual Cost ($ per year)

Vacuum cleaner

0.1 38

Hair dryer 0.25 100

Computer 4.0 520

Central Air conditioning

12 (60 days/year)

1500

$3.23/yr

$8.50/yr

$44.20/yr

$127.50/yr

Calculating Percent Efficiency

A regular incandescent light bulb uses only about 5% of its input energy to create light and converts over 95% of its input energy into heat

Compare that to compact fluorescent lights, which transform about 20% of their energy input into light

This means that compact fluorescent lights are more efficient than incandescent light bulbs

Calculating Percent Efficiency

The efficiency of a device is the ratio of the useful energy that comes out of the device to the total energy that went in The more input energy that a device converts into

usable output energy, the more efficient the device is

Efficiency is usually calculated as a percentage:

% efficiency = Eout x 100% Ein

Calculating Percent Efficiency

A car produces 27.5 kJ of useful output energy from 125 kJ of fuel. What is the car’s percent efficiency? Use the GRASP method. G – Given: Eout = 27.5kJ & Ein = 125 kJ R – Required: percent efficiency = ? A & S – Analysis and Conclusion:

Our formula is: % efficiency = Eout x 100% Ein

= [(27.5kJ)/(125kJ) ] x 100%

= 22% P – Paraphrase: The efficiency of the car is 22%.

Comparing Efficiency

To judge their energy cost and environmental impact

Ex: front-loading washing machine uses much less electricity, washes more clothes per load, and uses less water than a top-loading washing machine This reduces the energy needed to pump and heat water for

laundry

Ex: the energy used to run a mini-refrigerator in the 70s can run a full-size refrigerator today - woo efficiency increase by 300%!!

Read the Label

All large appliances have an EnerGuide label

http://oee.nrcan.gc.ca/energuide/home.cfm

1. The annual energy consumption of the appliance in kilowatt hours. The lower the number, the better.

2. The energy consumption indicator shows you how this model compares to others in its class. The bar below the indicator gives the energy efficiency range for this class of appliance. The further the indicator is to the left end of the scale, the better.

3. This bar shows you the energy consumption of the most and least efficient appliances in this class.

4. This tells you the type and capacity range of similar models compared.

How Off Is Off??

You may have noticed that even though you turn off your computer, your television, etc., there are little lights still glowing on them.

Many small appliances such as computers, stereos, televisions, DVD players, and answering machines, still use electrical energy even when they are turned off.

A way to counteract this is to use a power bar to hook up your appliances to, then turn the power bar off unless you need to use an appliance on it

Energy Conservation Begins at Home

Are lights being left on in rooms that are not being used?Is the clothes dryer being used for small loads like one

shirt?Is the hot water running continuously while the dishes

are being done?Is a lot of hot water being used for long showers?Are incandescent light bulbs being used instead of

compact fluorescent bulbs?Reusing and recycling materials, conserving energy, and

learning to live responsibly in harmony with our environment are key actions for living in a sustainable way