WindWise Education
Transforming the Energy of Wind into Powerful Minds
A Curriculum for Grades 6 -12
www.WindWiseEducation.org
Notice: Except for educational use by an individual teacher in a class-
room setting this work may not be reproduced or distributed by me-
chanical or electronic means without written permission from KidWind
or Pandion. For permission to copy portions or all of this material for
other purposes, such as for inclusion in other documents please contact
Michael Arquin at the KidWind Project at [email protected].
WindWise Education was developed with
funding from the New York State Energy
Research & Development Authority.
V1.0
HOW IS ENERGY
CONVERTED TO ELECTRICITY?
LESSON
1
TIME REQUIRED
2 – 3 class periods
GRADES
6 – 8
9 – 12
SUBJECTS
Physical Science
Mathematics
BACKGROUND
Energy exists in many forms and can be transformed from one form to another
in a process called energy conversion. Energy is "lost" as heat during each energy
conversion. Generally, fewer energy conversions mean less energy is "lost" and
thus energy efficiency is increased.
OBJECTIVES
At the end of the lesson, students will
n Understand that energy can be converted from one form to another.
n Understand that when energy converts, some energy is "lost" as waste heat.
n Understand that the more conversions and transfers there are in the
generation of electricity, the more opportunities there are for energy to be
"lost" as waste heat
METHOD
Students will explore the important natural process of energy conversion through
a combination of a demonstration and an activity involving cards. They will
determine how many energy conversions are involved in making electricity from a
variety of fuels and how they compare to each other in terms of efficiency.
KEY CONCEPT
Students will learn that
energy conversion and
transfer is an important
part of electricity
generation.
MATERIALS
❑ 2 lamps, one with an incandescent bulb and the other with a compact
fluorescent bulb (of equal brightness, measured in lumens)
❑ Calculator
❑ 1 card with image of a car *
❑ 1 card with image of gasoline *
❑ Cards with images of energy sources: coal, oil, natural gas, nuclear, solar,
wind, wood, water (each student pair will need 2 energy source cards. Copy
and cut the cards you need from the masters provided) *
❑ Cards with images of cell phones (2 cards per pair of students) *
❑ Blank 3x5 index cards (10 per student)
❑ Cards marked with the words “Waste Heat” (10 cards per student. Copy and
cut the cards you need from the masters provided).*
❑ Marker pens (1 per student)
❑ Beans, pennies or other manipulatives
❑ Student Worksheets *
*included with this activity
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1
ENERGY
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HOW IS ENERGY CONVERTED TO
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Lesson 1
GETTING READY
n Read about energy conversions and become familiar with the principles
and the terms used.
n Have some examples of devices discussed and ready for illustration.
n Copy and cut out enough sets of energy source and cell phone cards for
your class. Plan on each pair of students needing two energy source cards
and two cell phone cards. Make a few extra in case they are needed.
n To represent waste heat you will need some manipulatives like beans,
pennies, etc.
n This lesson has a number of building blocks that will be used in lessons 2,
6, 7 and 8. Allow enough time for this lesson and make sure that students
understand the concepts before moving on.
ACTIVITY
Beginning Questions for Students:
n How many of you use at least five things that are powered by electricity
each day? What are they?
n Where does energy come from? Can energy be created from nothing?
PART 1: TYPES OF ENERGY
Ask students to name some familiar forms of energy and record their answers
on the board. Next, ask students to read the activity reading passage that
introduces different forms of energy. Have the class (as a group) try to
categorize the list on the board based upon the table of energy types in the
reading passage. Talk with the class while categorizing in order to establish a
common understanding of types of energy.
PART 2: ENERGY CONVERSION DEMONSTRATION
Step 1
Plug in two lamps, one with an incandescent bulb (IB) and the other with a
compact fluorescent lamp (CFL). Make sure the bulbs have the same rating for
brightness.
Ask why the bulbs glow and produce light.
Answer: Electricity supplying an IB heats up a thin metal wire, which glows and
produces light. In a CFL the electricity heats up mercury gas, which also glows
to produce light.
Step 2
Ask some or all of the students to come up and place their hands near (no
touching!) each lamp and state what differences they can feel in temperature.
Ask why the IB is hotter than the CFL?
Answer: Electricity supplying an IB heats up a thin metal wire, which converts
the electricity into two types of radiant energy: visible light (the one we want)
ENERGY LOSSES
Every conversion or
transfer results in a "loss"
of energy, but the amount
loast varies with the specific
conversion or transfer.
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Lesson 1
and infrared waves (heat, the one we don’t want). The infrared waves (heat)
are waste heat because we do not want the heat, just the light. Some people
have joked that incandescent bulbs are great heaters that accidentally give off
some light.
In a CFL bulb, the electricity is used to vaporize a mercury gas, which causes it
to emit radiant energy (UV Waves). This energy reacts with a coating on the
inside of the bulb, transforming the UV waves to visible light waves.
Even though the CFL has more energy conversions, an IB uses 3-5 times more
energy than a CFL to create the same amount of light. All that extra energy
was wasted—creating heat, a byproduct we do not need.
How well you convert one energy form into another is called conversion
efficiency. The more efficient the conversion, the less energy is lost to waste.
The Extension Activities in Lesson 1 and Lesson 2 explore these ideas in more
detail.
Reiterate the two important points learned from this demonstration:
First, energy is converted from its original form of electricity to a new form
light. Energy has this capacity and regularly changes from one form to another
to cause “work” to occur, in this case the production of light.
Second, when energy converts from one form to another, there is always
some energy lost. Usually the loss is to heat and in many energy conversions,
the amount of heat produced is substantial. Have the students consider that
a car gets very hot when it runs. This is waste heat from the chemical energy
stored in gasoline as it is converted to the kinetic energy of motion of the car.
PART 3: ENERGY TRANSFER & ENERGY
CONVERSION CHAINS
Step 1
Make sure students understand the differences between energy transfer and
energy conversion.
Use examples from the Reading Passage.
Energy Transfer Example—The energy of the main crankshaft of a car
transfers to the tires, which make it move = Mechanical Energy to Mechanical
Energy.
Energy Conversion Example—Coal is burned to heat water in a power station
= Chemical energy (within the coal) to Thermal Energy (Infrared or Heat).
Step 2: Demonstrate a series of conversions
Feel the temperature difference
between the incandescent and
fluorescent bulbs.
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Lesson 1
Help students understand that energy goes through a series of conversions
before it can power a common item such as a cell phone or MP3 player. They
will do this by demonstrating energy transfers and conversions using the
gasoline and car cards. Place the gasoline card in the center of the table and
the car card on the right. You can also do this on the board as an example.
Gas to Car Moving
To show the conversions involved between gasoline and the car, write the
energy conversions needed on blank cards and add them to the chain.
n Chemical Energy ➔ Mechanical Energy
Chemical energy in the gasoline (fuel) is converted to mechanical
energy as the piston is moved by combustion/explosion.
n Mechanical Energy ➔ Mechanical Energy (Energy Transfer)
Mechanical energy of the engine crankshaft is transferred to the axles
and wheels through a variety of physical connections.
Production of Gasoline
Ask the students where the energy in the oil comes from. Since it is a type of
fossil fuel (like coal and natural gas), the starting point is plants and animals
buried millions of years ago and changed by heat and pressure.
A possible chain for some fossil fuels may be Sun ➔ Gasoline
n Nuclear Energy ➔ Radiant Energy
Nuclear fusion on the sun being transformed to visible light waves
n Radiant Energy ➔ Chemical Energy
Visible light waves driving photosynthesis, which allows plants to
produce sugar energy and grow larger
n Chemical Energy ➔ Chemical Energy (Energy Transfer)
Dead plants being compressed at high pressure and temperature for
millions of years and turning into oil
n Chemical Energy ➔ Chemical Energy (Energy Transfer)
Oil being refined into gasoline
In addition to the conversions and transfers, a lot of energy is used to refine
oil to gasoline and still more is used to transport the gasoline from refineries
to gas stations.
Gasoline
Gasoline
Car
Chemical to
Mechanical (C)
Radiant to
Chemical (C)
Chemical to
Chemical (T)
Chemical to
Chemical (T)
Mechanical to
Mechanical (T)
Solar
Nuclear to
Radiant (C)
Gasoline
Gasoline
Car
Chemical to
Mechanical (C)
Radiant to
Chemical (C)
Chemical to
Chemical (T)
Chemical to
Chemical (T)
Mechanical to
Mechanical (T)
Solar
Nuclear to
Radiant (C)
LEARNING
ENERGY
CHAINS
Learning to make energy
chains is confusing for
the first few times. We
recommend that you do
many practice examples on
page 15, so the students
build a library.
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Lesson 1
Step 3: Waste Heat
When energy is converted from the sun into the motion of a car via the
creation of gasoline, energy is lost at each step as waste heat in the same way
as with the light bulb demonstration earlier. You can symbolize this by simply
adding the words “Waste Heat” at each point in the chain where a conversion
or transfer occurs.
Using the cards: Add waste heat cards above each conversion.
On your illustration on the blackboard, write in “Waste Heat” above each
conversion.
Additional Practice
There are many other examples you can do with students on the handout
sheets (page 15). Some of these are energy transfers and others are energy
conversions. It is a good idea to walk students through a few examples so they
understand a conversion versus transfer, as this is an important distinction.
After you have completed some transformations and conversions as a class,
select a few from the sheet and write them on the board. The students can
then attempt to complete these on their worksheets.
PART 4: POWERING A CELL PHONE
Step 1
Hand out two different energy source cards (coal, oil, natural gas, nuclear,
solar, wind, wood or water) to each pair of students and two cards with an
image of a cell phone. In addition, provide each pair of students with the
following:
n Blank index cards to fill in the energy conversions and transfers
n The list of energy conversions they should use for this activity (on page 15)
n Beans (or other manipulatives) to act as waste heat
Using only their energy source cards, students should determine the chain of
energy conversions and transfers needed to provide energy to the cell phones.
Students will create chains showing how each energy source is used to create
electricity and then how that electricity is used to run the cell phone. Since
students are starting with different sources, these chains will be different.
Have students begin by placing the energy source card in the center of their
desk and the cell phone card on the right. Students will then write the energy
conversions and transfers needed on index cards and place them in line to
show each conversion between the energy source and the cell phone.
They can use the list of energy conversions that were discussed previously to
choose the appropriate conversions for each step. They may come up with
other ideas.
RENEWABLE
ENERGY
One common classification
system for energy is to label
energy either Renewable
or Non-Renewable. These
terms relate to how
energy is used by human
society rather than being
fundamental to energy itself.
Non-renewable energy
is generally extracted
from natural resources
such as fossil fuels (coal,
oil and natural gas), while
renewable energy is taken
from natural processes
as they occur (solar
energy, wind energy and
hydroelectric power).
When energy is released
from coal to create
electricity, the stock of
coal is reduced; hence it is
non-renewable. However,
energy used from the wind
to turn a turbine is not
consumed in the same way.
Wind energy production
does not make the future
less windy!
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Lesson 1
Have students add five waste heat manipulatives at each conversion point
where heat may be generated.
Make sure students save these as they will use them in the next step.
Step 2: Recording & Discussion
Once students have built a chain, have them transcribe their chains onto their
worksheets.
Have students present their chain to the class.
Class discussion
n How easy or hard was this activity? What parts were confusing or
challenging?
n Do you think your chains capture all the conversions or transfers? Could
there be some you missed?
n Do your energy chains show all the conversions required to create the
fuel source?
n Which chains are the longest? Why?
n What do you think is more efficient, a long chain of conversions or a short
chain? Why?
n Which forms of energy produce the least amount of waste in order to
power the cell phone?
n Are there other factors involved besides the number of conversions
that we need to consider as we decide which power sources are used to
generate electricity?
PART 5: THERMODYNAMICS AND ENERGY MATH
Step 1: 1
st
& 2
nd
Laws of Thermodynamics – Energy Math
The First Law of Thermodynamics says that energy cannot be created or
destroyed. You can change it to different forms through conversion or transfer.
The Second Law of Thermodynamics—or the Law of Increased Entropy— says
that while quantity of energy remains the same (see First Law), the quality
of energy deteriorates. As we convert or transform one form of energy to
another, some of the usable energy is converted into unusable energy, which is
“lost” to our use. This is the "waste heat."
For the purpose of this activity, assume that all energy conversions are 50%
efficient (in reality, the amount of energy lost in conversions varies widely). In
other words, only 50% of the usable energy in the original form is converted
to the new form and 50% of the energy is lost as unusable heat.
Step 2
Demonstrate this energy “loss” by doing a simple demonstration.
Start with the Car Example
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Lesson 1
Sun to Car Moving
n 100 Beans 1. Nuclear Energy ➔ Radiant Energy
Nuclear fusion in the sun creating solar energy
100 x 0.50 = 50 (50% = 0.50)
n 50 Beans 2. Radiant Energy ➔ Chemical Energy
Photosynthesis allowing plants to make sugar and grow
n 25 Beans 3. Chemical Energy ➔ Chemical Energy (Energy Transfer)
Plants being compressed for millions of years and turning into oil
n 12 Beans 4. Chemical Energy ➔ Chemical Energy (Energy Transfer)
Oil being refined into gasoline (Rounded down to create an even number)
n 6 Beans 5. Chemical Energy ➔ Mechanical Energy
Gas combustion moving piston
n 3 Beans 6. Mechanical Energy ➔ Mechanical Energy (Energy Transfer)
Piston moving crankshaft and axle and tires
Using this example, only 3% of the energy (3 beans of 100) coming from the
sun is what is left to make the car move.
Step 2
Using the chains that they just completed in Part 4, have students calculate the
amount of energy that is used to perform useful work in the cell phone. Start
with 100 beans at the original energy source as in the car example. This could
provide an estimate of the efficiency of the series of energy conversions that
have to occur to make the cell phone work.
EXTENSIONS
Extension Activity 1: Conversion Efficiency
The efficiency of energy conversions can vary widely depending on the
conversion. For example, electric heaters and hair dryers are around 100%
efficient because they are designed so that the waste heat is the desired result
of the conversion.
It is important to keep in mind that it is not always the number of conversions
or transfers that can lead to energy being wasted or lost, it is also the
efficiency of the conversion or transfer.
Looking at the efficiency chart (page 20), notice that some conversions that
are very short (for example, Sun to Electricity) are also very inefficient. How
would this compare to a long series of conversions from Coal (or other fossil
fuel) to Electricity. Which one chain is most efficient? Try this for other energy
sources: Wind to Electricity, Natural Gas to Electricity.
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Lesson 1
Extension Activity 2: Bulb Temperatures
Take two thermometers and use a clamp stand to hold it three inches away
from each type of light bulb, being careful to make it as close to the same
distance from each bulb as possible. Measure the difference in temperature
between the two, as accurately as you can.
This difference will be proportional to the difference between the energy
output of each bulb and represents the difference in efficiency between the
two. Make sure you also measure the ambient temperature in the room while
you are conducting the experiment.
See if this function is roughly correct.
Temp IB – Ambient Temperature
=
Watts IB
______________________________ __________
Temp CFL – Ambient Temperature Watts CFL
Extension Activity 3: Campus Applicances
Assign students to research various appliances on campus to assess how
efficient they are at converting energy. They can assess lighting, heating,
cooling, and computer systems and perform an analysis of transportation,
including school district vehicles and commuting vehicles.
VOCABULARY
Energy – The capacity for doing work; usable power (as heat or electricity);
the resources for producing such power.
Energy Conversion or Transformation – The conversion of energy from
one form to another. For example, when coal (chemical energy) is burned,
it produces heat (thermal energy) that is then captured and used to turn a
generator (mechanical energy), which transforms the energy into electricity
(electrical energy).
Non-Renewable Energy – An energy source which is present in a limited
quantity. At some point this energy resource will become scarce.
Renewable Energy – An energy source that is naturally replenished. Examples
include biomass, wind, geothermal, hydro, and solar energy. See sidebar.
Thermodynamics – The study of the conversion of energy into work and heat
and its relationship to variables such as temperature, volume and pressure.
Waste Heat – As energy is converted from one form to another, some energy
is converted to heat and “lost” from the resulting form.
Work – In physics, mechanical work is the amount of energy transferred by
a force acting through a distance. For example, the amount of an electric
current travelling down a wire to a light bulb lighting the bulb is work.
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Lesson 1
NY STATE STANDARDS
Intermediate Level Science–Standard 1: Analysis, Inquiry, and
Design
Students will use mathematical analysis, scientific inquiry, and engineering
design, as appropriate, to pose questions, seek answers, and develop solutions.
Scientific Inquiry
Key Idea 1:
The central purpose of scientific inquiry is to develop explanations of natural
phenomena in a continuing, creative process.
Major Understandings:
S1.3: Represent, present, and defend their proposed explanations of everyday
observations so that they can be understood and assessed by others.
Intermediate Level Science–Standard 4: The Physical Setting
Students will understand and apply scientific concepts, principles, and theories
pertaining to the physical setting and living environment and recognize the
historical development of ideas in science.
Key Idea 4:
Energy exists in many forms, and when these forms change, energy is
conserved.
Major Understandings:
4.1: Describe the sources and identify the transformations of energy observed
in everyday life.
4.1a: The Sun is a major source of energy for Earth. Other sources of energy
include nuclear and geothermal energy.
4.1b: Fossil fuels contain stored solar energy and are considered nonrenewable
resources. They are a major source of energy in the United States. Solar
energy, wind, moving water, and biomass are some examples of renewable
energy resources.
4.1c: Most activities in everyday life involve one form of energy being
transformed into another. For example, the chemical energy in gasoline
is transformed into mechanical energy in an automobile engine. Energy,
in the form of heat, is almost always one of the products of energy
transformations.
4.1d: Different forms of energy include heat, light, electrical, mechanical,
sound, nuclear, and chemical. Energy is transformed in many ways.
4.1e: Energy can be considered to be either kinetic energy, which is the energy
of motion, or potential energy, which depends on relative position.
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Lesson 1
4.5: Describe situations that support the principle of conservation of energy.
4.5a: Energy cannot be created or destroyed, but only changed from one form
into another.
4.5b: Energy can change from one form to another, although in the process
some energy is always converted to heat. Some systems transform energy
with less loss of heat than others.
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Waste HeatWaste HeatWaste Heat
How is Energy Converted to Electricity?
Lesson 1
Student sheets
Waste Heat Waste Heat Waste Heat
Waste Heat
Waste HeatWaste Heat
Waste HeatWaste Heat
Waste Heat
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
Car
Cell Phone
Coal
Natural Gas
Nuclear
Solar
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
Water
Wind
Wood Oil
Gasoline Electricity
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
Electromagnetic Waves
Radio
Microwave
Infrared
Visible light
Ultraviolet
X-ray
Gamma
Stored
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
EXAMPLE ENERGY TRANSFERS AND CONVERSIONS
As students do these on the worksheets, they will be part of an energy chain library that students can use
to complete their cell phone energy diagrams.
Fuel in a power plant creating moving steam
Chemical Energy (coal) ➔ Radiant Energy (infrared waves) ➔ Thermal Energy (water heating making
steam) ➔ Mechanical Energy (steam moving)
Moving steam creating electricity
Mechanical Energy (steam moving) ➔ Mechanical Energy (generator shaft spinning) ➔ Electricity Energy
(magnets and wires—induction)
That electrical part sounds magical—see Lesson 7 for more on how a generator actually works!
Sun heating the ground then heating the air, making wind
Nuclear Energy (fusion) ➔ Radiant Energy (infrared waves) ➔ Thermal (ground getting warm) ➔ Radiant
Energy (ground releasing infrared waves to air) ➔ Thermal Energy (air heating) ➔ Mechanical Energy (air
rising and moving around the planet)
Sun to being warm
Nuclear Energy (fusion) ➔ Radiant Energy (infrared waves) ➔ Thermal Energy (skin warming)
Sun to you walking down the street
Nuclear Energy (fusion) ➔ Radiant Energy (visible light waves) ➔ Chemical Energy (photosynthesis in
plants) ➔ Chemical Energy (transform plant food to energy) ➔ Mechanical Energy (muscles moving and
you walking)
Sun to electricity (photovoltaic)
Nuclear Energy (fusion) ➔ Radiant Energy (visible and UV waves) ➔ Electrical Energy (via solar panel
magic)
Is there another way to get electricity from the sun? Sure!
Sun to electricity (biomass)
Nuclear Energy (fusion) ➔ Radiant Energy (visible light waves) ➔ Chemical Energy (photosynthesis in
plants) ➔ Chemical Energy (plant matter being burned) ➔ Radiant Energy (water heating making steam)
➔ Mechanical Energy (steam moving) ➔ Mechanical Energy (generator spinning) ➔ Electrical Energy
Sun to plants growing
Nuclear Energy (fusion) ➔ Radiant Energy (visible light waves) ➔ Chemical Energy (photosynthesis—light
waves to sugar)
Rechargeable battery being charged and then running a portable game system
Electrical Energy (from the wall socket) ➔ Chemical Energy (chemistry of the battery stores electricity)
➔ Electrical Energy (Chemical reaction converted to electricity)
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
Electricity making a speaker in a phone work
Chemical Energy (phone battery) ➔ Electrical Energy ➔ Sound Energy
Electricity lighting the phone screen
Chemical Energy (battery) ➔ Electrical Energy ➔ Radiant Energy (light on phone screen)
Fire keeping you warm
Chemical Energy (stored in wood) ➔ Radiant Energy (infrared waves) ➔ Thermal Energy (skin warming)
There are many, many more. Once you get the hang of it you can see the transfers and conversions taking
place all around you. See if your students can come with their own.
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
READING PASSAGE
Work done by animals and machines requires a quantity of energy. Energy is around us all the time in
many forms. Energy is the ability to perform work. Work is a force than can cause an object to move.
For an animal or machine to do something that requires energy, the energy must be changed from one
form to another during the process of work. This happens all the time and is called an energy conversion
or energy transfer. When energy is changed from one form to another, it is called energy conversion (eg.
potential energy to kinetic energy—water behind a dam to flowing water) but when it changes to the
same form it is called an energy transfer (eg. chemical energy to chemical energy —energy stored in fat is
transferred to energy in sugar so it can be used).
Your body is capable of converting energy from one form to another. For example, if you eat a hamburger
and then play Frisbee, all the movements that it takes to catch and throw a Frisbee require you to convert
the energy in the hamburger into the energy to make your muscles move. After a while, you will get tired
because you have converted all the energy that was made available to you by the hamburger. You need to
refuel by eating more food or burning some of the energy stored in your body as fat.
The energy of the hamburger can only be converted once from its original form. Once the body has
transformed the energy in the hamburger, the rest is excreted as waste. You constantly need a source of
energy in a form that your body can use.
The First Law of Thermodynamics, loosely interpreted, states that energy can neither be created nor
destroyed; it changes from one form to another. During a conversion or transfer, some of the available
energy is used to cause work to happen, and in the process the energy changes to a different form.
Table 1. Forms of energy
POTENTIAL ENERGY KINETIC ENERGY
Stored Energy or Energy of Position Energy of Motion
Chemical – Energy stored in chemical bonds.
Some examples are coal, natural gas, petroleum.
Radiant – Energy that travels in electromagnetic
waves such as x-rays, UV waves, visible light waves,
radio waves, infrared (heat) waves.
Nuclear – Energy in the nucleus of an atom.
Extraction through fission (splitting atoms) or
through fusion (fusing atoms).
Mechanical – Movement of things or objects
from one place to another. Wind is a movement of
air molecules.
Stored – Energy in a mechanical item such as a
spring that is compressed or rubber band that has
been stretched.
Electrical – Movement of electrons such as in
lightening or electrons in electrical wires.
Energy of Position or Gravitational Energy
Things that have mass and have height above the
surface of the Earth have stored energy due to
gravity. Water above a dam or a rock held above
your head has stored gravitational energy.
Thermal – Internal energy of vibrating molecules.
Temperature is a measure of this internal energy.
The faster molecules within a substance vibrate,
the higher the temperature
Sound – Movement of energy through objects.
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How is Energy Converted to Electricity?
Lesson 1
Student sheets
Wind blowing through the blades of a wind turbine causes the blades to rotate due to the orientation and
shape of the blade. The blades are attached to a driveshaft, which will also rotate. The energy transfer
from the wind to the turbine is kinetic energy.
The spinning driveshaft causes magnets to rotate in the generator, which are situated near copper coils.
This arrangement converts the kinetic energy of the shaft into electrical energy that then travels along
power lines to your home or school.
If you toast a piece of bread in your toaster, you have converted the energy one more time from electrical
energy to thermal energy, which, after you have eaten the toast, will be converted to mechanical energy
when you throw a Frisbee.
The energy conversions and transfers involved are shown in the chain below.
Mechanical Energy (wind blowing) ➔ Mechanical Energy (blades rotating) ➔ Mechanical Energy (driveshaft
rotating) ➔ Electrical Energy (magnets and wires in generator) ➔ travels down wires ➔ Thermal
Energy (heating toaster element) ➔ Chemical Energy (converting toast to sugar for the body to use) ➔
Mechanical Energy (body converting sugar to muscles moving)
When energy changes form, not all the energy present at the beginning of the process is converted into
the product at the end of the process. What happens to it? Some energy is “lost.”
But wait—energy cannot be lost! Recall that energy can neither be created nor destroyed, so how can
energy be lost? The only way, according to the First Law, is that some must be converted to another form.
When the blades of a wind turbine rotate in the wind, only about 40-50% of the available kinetic energy in
the wind is converted to rotation of the blades due the following factors:
n Wind must flow through the device for it to work properly. All the wind's energy cannot be used by
the turbine. A famous physicist named Alfred Betz determined that the most perfect turbine in the
world could only convert 59% of the energy in the wind to usable energy.
n Imperfection in the design of the blades.
n Friction caused by the moving parts of the wind turbine as they spin and rub against each other.
Friction creates heat, which is a form of thermal energy. Heat energy is the most common form of energy
loss during an energy conversion. You have felt waste heat before. Playing Frisbee makes you hot and
sweaty—that is the heat energy wasted when your body converts calories from your food to motion of
your body. Other examples include car engines heat up when they are running and light bulbs give off heat
when they are emitting light.
Energy being lost or wasted during energy conversions is so universal that it is described in the Second
Law of Thermodynamics. This law is complicated, but can be simply stated like this: while the quantity of
energy remains the same, the quality of energy deteriorates over time. Another way to think of it, is that
as we convert or transform one form of energy to another some of the usable energy is converted into
unusable energy that is “lost” to our use.
This Second Law has frustrated human engineers throughout history. The word “efficiency”—how much
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of the energy available to a machine can be converted to useful work—is tied to this frustration.
Many of the machines that you use every day are less than 20% efficient (i.e., they convert less than 20%
of the energy available to them into useful work).
One of the biggest challenges facing engineers of energy conversion devices is to try to overcome the
Second Law and come up with more efficient machines.
Will you be the person to solve this challenge?
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Name Date Class
PART 1: TYPES OF ENERGY
1. Write down some forms of energy.
2. Classify the forms of energy you have written down into one of the categories discussed in the reading
passage. If you are not sure how to classify them, take a guess.
PART 2: ENERGY CONVERSION DEMONSTRATION
For this part of the lesson you will need your Forms of Energy Table in the reading passage.
1. Which lamp is the hottest?
2. Which lamp is more efficient at converting electricity to light? What is your evidence?
3. What is waste heat? Provide some examples.
4. Calculate the improvement in efficiency for a CFL over an IB by dividing the watts for the IB by the
watts for the CFL.
IB
=
_________ times more efficient
CFL
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PART 3: ENERGY TRANSFER & ENERGY CONVERSION CHAINS
For this part of the lesson you will need your Forms of Energy Table in the reading passage.
1. Write down the Energy Chain that converts the energy in gasoline to a car moving.
2. Write down the Energy Chain that converts the energy from the sun to gasoline.
3. Your teacher has written a few common energy conversions on the board. Complete Energy Chains
for at least three of them. If you have more time you can do more!
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PART 4: POWERING A CELL PHONE
Your teacher has provided two energy sources and a cell phone. Using the index cards, create energy
chains from each source to power the cell phone.
After you have used the index cards to create your energy chains, draw them here. Be sure to include the
energy chain used to power the phone and the chain that shows where the fuel originated.
Answer the following questions:
1. How many conversions or transfers did each chain have? How many forms?
2. Which one created more waste heat?
3. Do you have all the conversions or transfers accounted for? Are there any additional "hidden" ones?
Name Date Class
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4. Do you think that all conversions/transfers have the same efficiency? What factors might cause them
to be different? Can you list one or two?
PART 5: ENERGY MATH
1. If you started with 100 units for each of your energy chains, how many did you have left at the end
once your phone was powered?
2. What percentage of energy was left to power the phone?
3. Which of your chains seems most efficient?
For more realistic conversion percentages see the table for Extension 1.
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EXTENSION 1
Table 1. Efficiencies of some common energy conversion devices
ENERGY CONVERSION DEVICE TYPICAL EFFICIENCY %
Electric heater 100
Hair dryer 100
Electricity to heat (Kitchen Range) 80
Electric generator 95
Wind generator 30
Hydroelectric generator 21
Electric motor (large) 90
Battery 90
Steam boiler (power plant) 85
Steam turbine 45
Home gas furnace 85
Home oil furnace 65
Electric motor (small) 65
Automobile engine 25
Incandescent bulb 5
Natural gas to electricity 33
Natural gas to heat 40
Natural gas to hot water 60
Natural gas to electricity (fuel cell) 90
Steam boiler (power plant) 85
Gasoline to mechanical energy (car) 22
Diesel to mechanical energy (car) 35
Hydrogen to electricity (fuel cell) 50
Sun to electricity 15
Sun to heat 40
1. What are some very efficient conversions?
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2. What are some very inefficient conversions?
3. Solar to electricity is only 15% efficient, but natural gas to electricity is 33% efficient, which one is
better? What does this type of comparison leave out?
EXTENSION 2
If you or your teacher measured the difference in temperature between the IB and CFL, calculate whether
the difference in temperature (caused by waste heat) is about the same as the efficiency difference you
just calculated.
See if this function is roughly correct:
Temp IB – Ambient Temperature
=
Watts IB
Temp CFL – Ambient Temperature Watts CFL
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PART 1: TYPES OF ENERGY
1. Write down some forms of energy.
Student Observations
2. Classify the forms of energy you have written down into one of the categories discussed in the reading
passage. If you are not sure how to classify them, take a guess.
Student Observations
PART 2: ENERGY CONVERSION DEMONSTRATION
For this part of the lesson you will need your Forms of Energy Table in the reading passage.
1. Which lamp is the hottest?
Student Observations
2. Which lamp is more efficient at converting electricity to light? What is your evidence?
The CFL is more efficient. It takes less energy to activate the mercury gas inside the bulb than it does to
heat the wire in an IB. The IB gets hotter because more of the energy is released as heat representing
waste.
3. What is waste heat? Provide some examples.
Waste heat represents energy that is released during an energy conversion or transfer and is energy that is
released that has not done any work.
4. Calculate the improvement in efficiency for a CFL over an IB by dividing the watts for the IB by the
watts for the CFL.
Answer depends upon the bulbs used.
PART 3: ENERGY TRANSFER & ENERGY CONVERSION CHAINS
For this part of the lesson you will need your Forms of Energy Table in the reading passage.
1. Write down the Energy Chain that converts the energy in gasoline to a car moving.
2. Write down the Energy Chain that converts the energy from the sun to gasoline.
3. Your teacher has written a few common energy conversions on the board. Complete Energy Chains
for at least three of them. If you have more time you can do more!
Student draw chains copied from the board here.
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PART 4: POWERING A CELL PHONE
Your teacher has provided two energy sources and a cell phone. Using the index card, create energy
chains from each source to power the cell phone.
After you have used the index cards to create your energy chains, draw them here. Be sure to include the
energy chain used to power the phone and the chain that shows where the fuel originated.
Students draw the chains they developed here.
Answer the following questions:
1. How many conversions or transfers did each chain have? How many forms?
Student Observations
2. Which one created more waste heat?
Student Observations
3. Do you have all the conversions or transfers accounted for? Are there any additional "hidden" ones?
Student Observations
4. Do you think that all conversions/transfers have the same efficiency? What factors might cause them
to be different? Can you list one or two?
Some examples of observations:
Appliances that generate heat have no “waste” in their conversion
Wherever friction is involved, it will reduce the efficiency of conversion
PART 5: ENERGY MATH
1. If you started with 100 units for each of your energy chains, how many did you have left at the end
once your phone was powered?
Student observations – 100 x (0.5)n where n = the number of conversions
2. What percentage of energy was left to power the phone?
Student observations – the number of beans at the end expressed directly as a percentage
3. Which of your chains seems most efficient?
Student observations – the one with the highest percentage of the original energy left = the one with the
fewest number of conversions
For more realistic conversion percentages see the table for Extension 1.
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EXTENSION 1
1. What are some very efficient conversions?
Student Observations
2. What are some very inefficient conversions?
Student Observations
3. Solar to electricity is only 15% efficient, but natural gas to electricity is 33% efficient, which one is
better? What does this type of comparison leave out?
Student observations.
EXTENSION 2
If you or your teacher measured the difference in temperature between the IB and CFL, calculate whether
the difference in temperature (caused by waste heat) is about the same as the efficiency difference you
just calculated.
See if this function is roughly correct:
Temp IB – Ambient Temperature
=
Watts IB
Temp CFL – Ambient Temperature Watts CFL
This ratio should be roughly equal. It will be unlikely to be exact given the limitations on inaccuracy of how
the temperature was measured.
