Student Pages - Global Climate Change
Using Electricity Affects Global Climate Change
What can you do to help?
Background Information:
Electricity is made in big factories called power plants. Power plants cause a lot of air pollution.
One of the main pollutants produced by power plants is carbon dioxide, especially in power
plants that use coal or natural gas as fuel! Carbon dioxide leaves the smoke stacks at the power
plants and goes into the air and stays there. The carbon dioxide acts like a blanket over the
Earth, which prevents some of the heat absorbed from the Sun during the day from escaping.
This is called the Greenhouse Effect because that is how a
greenhouse works – the glass (instead of carbon dioxide) traps the
heat energy from the Sun making the greenhouse warm so the plants
can grow. You may have experienced the same phenomenon if you
have ever sat in a car with the windows closed during the summer – it
gets very warm!
Most scientists believe that over a long time, the increasing amount of carbon dioxide is causing
changes in climate around the world - changes in average temperatures, precipitation and
weather. This whole issue is called Global Climate Change.
Did you know?
Cell phone chargers
use energy even when
they are plugged in to
the wall but not
charging a phone.
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Student Pages - Global Climate Change
Different Kinds of Power Plants in the USA
Viewing the illustration:
All power plants produce electricity. Which fuel is used most often in power plants in the USA?
A discussion question:
If the climate changes, what impacts may that have on humans? (For example, perhaps the
increased warmth causes glaciers to melt, and the ocean level to rise.)
Good news: Anything that reduces electricity use will decrease carbon dioxide in the air! Even
little things can make a big difference.
Light bulbs require electricity to work. You can make a difference. Just replace one regular
incandescent light bulb with a compact florescent bulb! Just switching one bulb will help
reduce carbon dioxide in the air as much as planting 34 trees! (Trees use carbon dioxide to
make food.)
A math application: If you replace three light bulbs at home with CF bulbs, it has the
same affect on carbon dioxide removal as planting how many trees? ________ trees
(Hint: 1 bulb replacement removes as much carbon dioxide as 34 trees,
so 3 bulbs would remove as much carbon dioxide as _____ trees.
Formula: 1/34 = 3/x and solve for x!)
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Student Pages - Global Climate Change
How much do we use? How much can we save?
New Units: Watt’s a Watt?
Watt (W): This is the unit of power used all over the world. It was named for James
Watt (1736 – 1810). He was important because he helped develop the steam engine –
an engine that runs on steam. (Example: A 60Watt bulbs draws 60W of power.)
Kilowatt (kW) = 1000 watts of energy (kilo means 1000)
Kilowatt hours (kWh)= the number of kilowatts (kW) x the number of hours (h) the
device is used (i.e. To get kilowatt-hours, you multiply the numbers of kilowatts times
the hours you used the device.)
When your mom or dad looks at their monthly electric bill, it may tell them how many kilowatthours(kWh) they used. How many kWh were used by Jane this month? _______kWh
Let’s look at an example:
Gabriella has a lamp that uses a 60 watt bulb (60W).
She uses that lamp for 5 hours (h) a day.
Gabriella does this for 30 days.
Problem:
How many kilowatt-hours does Gabriella’s lamp use in 30 days?
Solution:
60 watts x (5 hours x 30 days) = 9,000 watt-hours
But we need to know the answer in kilowatts, so we must divide by 1,000. The answer is 9.000
kWh (9 kilowatt-hours).
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Student Pages - Global Climate Change
Computers, Printers, and Energy, Oh My!
So, how can schools help reduce electricity use and help stop global climate change? Schools
use lots of electricity, and some of it is used to provide power for computers and printers in
classrooms, computer labs, media center, offices, etc. An average computer uses 81W (watts),
while an average printer draws 115 W.
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One of our tasks is to see how much energy (in kWh) is used on computer technology in
our school after school hours.
Our next job is to determine the cost! You need one more figure to determine the cost
– the cost of using one kilowatt hour (kWh) of energy! Let’s estimate it as .125 cents
($.125) (Can you guess what our next step will be?)
Here is a simple example: Jones Elementary School has 143 computers, each of which is on
from 8:00 until 6:00 p.m. Most students and staff leave the school by 4:00 p.m. How could this
school do better to conserve energy?
Step one: Calculate the energy saved by one computer being turned off 2 hours earlier:
1. 196W (energy usage by one computer system) x 2 hours (savings by ending at 4
p.m.) x 184 days (in an academic year) = 72,128 Watt hours/year.
2. Convert to kWh by dividing by 1,000 =72.128 kWh per year saved by one computer
Step two: Calculate the energy saved by all the schools computer turned off two hours earlier
72.128 kWh (from Step one) x 143 (# of computers in this school) = 10,314.3 kWh: This
the energy saved per year saved when 143 computers are used 2 hours/day less.
Step three: Now, let’s calculate the cost savings for this school
11,314.3 kWh saved (from Step 2) x $ .125 kWh (cost per kWh) = $1,289.29
What could your school do with an extra $1,300.00? Sometimes money talks!
How would the environment benefit?
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Student Pages - Global Climate Change
What is the energy used by our school’s computers and printers?
How many computers are in our school?
How many printers are in our school?
Does our school have a procedure for shutting
down computers and printers at the end of the
day?
What time do our computers shut down
automatically?
Are people shutting down the computers when
they leave the building?
Are people shutting down the printers when they
leave the building?
How much energy would be saved if all the
computers and printers in the school were turned
off two hours earlier than the automatic shut down
time?
Data to use for calculations:
Watts used by each computer
81 W
Watts used by each printer
115 W
Step one: Calculate energy saved by turning
off one computer and one printer two hours
early.
For one Computer : (81 W x ___ hours a day
beyond school x 184 number of days) divided
by 1,000 (convert W to kW) = ________kWh
For One Printer: (115 W x ___hours a day
beyond school day x 184 number of days)
divided by 1,000 (convert W to kW) =
________kWh
Step two: Calculate the energy saved by
turning off all the school computers and
printers.
Energy saved for one computer (answer
above) x total number of computers =_____kWh
Energy saved for one printer(answer above) x
total number of printers = _________kWh
How much energy would be saved by our school by
turning off all computers two hours early?
How much money could our school save in one year
by turning off all computers two hours early?
Step three: Add those last two numbers
together and you get the total amount of kWh
saved by turning off computers and printers
two hours early for a year! ______________
kWh
Energy saved:
Take the total amount of energy saved from
Step three and multiply it by $.125. The
answer is $_______, and that is the amount of
money saved by the school by conserving
energy!
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Student Pages - Global Climate Change
Let’s explore energy usage and cost with some items we have at home:
Review the list of energy-using items: Select one item that you use every day (or would like to
use every day).
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
How much energy is used by your item over a year?
Hint: (___ Watts x ___hours a day that you use it x 365 days in a year) divided by 1000
(converts W to kW) = ________kWh in a year.
How much will it cost to use your item over a year?
Hint: The answer above in kWh x $.125 (cost per kWh) = $______
Here is an energy calculator to help:
http://michaelbluejay.com/electricity/howmuch.html
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A device using 1 kWh of energy uses 2 pounds of coal. How many pounds of coal were
burned by your item? _______lbs_ ( You can do it!) The bigger the number, the more
carbon dioxide went into the air!
How much energy could be saved by using your item 50% less? (Half the number of
hours.) _______________kWh
How much money could be saved by using your item 50% less? ( Hint: the answer above
x $.125 = $________) What could you buy with that money? (Imagine that: good for
Action:
Using what you now know, brainstorm a message for fellow students about the need for
conserving energy/or ways to conserve energy. The message can be communicated by poster, a
cartoon, a comic strip, a poem, a song or rap. Have fun, but get the message across!
Create the message and bring it back to school!
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