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What is Energy?
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One way to define energy is by observation.
If you see something that doesn't happen on its own, then there must be
some energy being expended. For example, cars don't go up hill on their
own, so there must be some energy getting used. Coming downhill, however,
we could see that happening without any energy being used. |
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Like the car going up hill, anything that gets
lifted against gravity requires some energy.
Fortunately, this energy has the potential to be used again. For example,
the energy to raise the skiers up the mountain will be used to propel the
skiers down the slopes. |
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We can think of just two
types of energy, one doing work, and
the other waiting to do work.
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Freedom Train at Houston Union Station, February
1976 - photo © Gary Morris (Used with Permission) |
| When it's doing work, we see it pushing
or pulling, glowing, or changing the temperature. This train is using
energy in three ways because it's pulling cars,
heating up the surrounding air, and giving
off light. |
Energy that is waiting to do work (has to the
potential for work) is called potential energy
and is recognized in 3 ways:
1) It sits above ground level |
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| On the left is a pile
driver. A weight (the driver) is lifted
up to the top of the rig. The weight now has potential
energy. As it falls the potential energy becomes kinetic
energy (moving energy). When it strikes the post (pile/piling)
at the bottom, the energy is used to drive the post farther into the ground.
It's a smart way to deliver a lot of force. Wrestlers use the pile
driver maneuver by lifting the opponent and letting gravity
do the work as the opponent falls to the mat head first. |
On the right is Hoover dam. Lake
Mead is held back by the dam. Lake Mead sits higher
than the ground below the dam. This means the water in the lake has
a lot of potential energy. This energy is tapped
when water is allowed to flow downhill (kinetic energy) and spin turbines. |
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Energy is potential energy if: 2) Something
is compressed in someway
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| A set mousetrap has a spring that has been
compressed (or stretched), and it's sitting
there ready to convert this potential energy to kinetic
energy as the wire trap flips over to the other side. |
A tank of compressed
air also possesses potential energy. If an air tool is attached that
potential energy is used to push
a piston that makes the air tool mechanism spin or vibrate. |
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Chemical energy
is a type of potential energy. It's similar
to raising objects against gravity (like the pile driver) except instead
of moving objects against the attraction of gravity, it is moving objects
against the attraction of plus and minus charges. To illustrate this,
let's look at the simplest of elements, hydrogen....
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The hydrogen atom consists of
one proton (+)
and one electron (-). The proton sits
in the center (nucleus) of the atom.
The proton is 2,000 times heavier than the electron. The electron is lightweight
and very mobile. The diagram shows the electron as a sphere orbiting the
nucleus. This is a simplistic view of an electron. Electrons are more cloud-like
than ball-like. If an electron is moved farther away
from the proton it takes
energy because they are attracted to each other (like gravity). The
farther away the electron has been moved away from the proton, the more
energy it takes, and the more potential energy stored
in the electron. When the electron drops back
closer to the proton, it will convert that
potential energy to light energy. The light
energy can be in the form of infrared, visible, ultraviolet, or even xray
light. |
| Chemical energy
is stored in fuels like methane (natural gas) and gasoline. Let's see how
methane combining with oxygen (combustion) gives up this type of potential
energy. |
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When methane collides with oxygen
at high speeds (caused by flame or spark), there's a rearrangement of the
atoms. Two of the oxygen atoms will combine with the four hydrogen (H) atoms
to form two water molecules (H2O). The other two oxygen
atoms will combine with methane's carbon atom to form carbon dioxide. Why
does this give off energy? |
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Below is the same diagram as above, except all
of the protons and electrons
that hydrogen, carbon, and oxygen have are shown. Hydrogen has one proton
and one electron. Carbon has six protons and six electrons. Oxygen has
8 protons and 8 electrons. Remember the electrons are all being pulled
on by the protons (kind of like Earth pulling on objects on the Earth).
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| The reason energy is released during rearrangement
is that overall, the electrons
are closer to the protons
than they were originally. Remember when the
electron on the hydrogen atom goes from farther
away to closer, energy
is released? Same thing is happening here except
several electrons are involved. This "moving" closer to the nucleus
means that some of the potential energy gets converted to light. The light
is the visible light you see in the picture plus a great deal of infrared
light, which is the heat you feel radiating from the flame. |
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Where
do we get energy?
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| Above, you saw pictures of Lake Mead, a locomotive,
and a weight lifter. But where did the energy come from that gave the water
in Lake Mead the potential energy to generate electricity at the dam? Where
did the locomotive get the diesel to power its engines? Where did the weight
lifter get his food and the calories to lift the barbell? |
| Our Sun is the ultimate
source of energy that we use here on Earth. The rain that filled Lake Mead
came from solar energy evaporating water from the oceans. The diesel for
the train came from plants that grew with the Sun's energy and eventually
became petroleum. The weight lifter got his calories from meat and plants.
The plants got the energy from the Sun, and the meat came from animals that
ate plants that got energy from the Sun. |
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The below picture shows the Sun and Earth and the distance
between them to proper scale. If a viewer is far enough back to see the
Sun and Earth together, the Sun on the left is visible, but the Earth appears
as another dot against the stars in the background. The temperature of space
is colder than 400 degrees Fahrenheit below zero. Without the Sun, not only
would the Earth's oceans freeze solid, the air in the atmosphere would freeze
solid as well. |
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Considering
the distance and relative small size of Earth, it's surprising that we
get so much energy from the sun. Fortunately...
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The Sun radiates huge amounts of energy
in the form of visible light, infrared light (heat light), ultraviolet,
and X-rays. Earth intercepts less than one trillionth of this energy.
In other words, the Sun puts out enough energy to satisfy 2,000,000,000,000
(2 trillion) Earths.
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The picture on the left was taken
from the surface of Mars. Earth is seen as a small dot. Mars is about 1
and a half times the distance Earth is from the Sun, which means Mars get
less than half the energy from the Sun than Earth does. The polar ice caps
of Mars are made from "dry ice" (frozen carbon dioxide) not water
ice.
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Even though the Sun is the original source
of energy, we use different forms of energy that was made possible by
the Sun. They are the following:
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| FOSSIL FUELS: Fossil fuels get their name because
they formed from microscopic plants millions of years ago (see pic below).
Fossil fuels include natural gas, coal, and the fractions of petroleum such
as gasoline, oil, diesel fuel, propane, butane, and tar. Nature has taken
60 to 300 million years to make these fuels, but we might use them up in
17 to 70 years from now, depending on future consumption. |
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Wind power
is a growing source of renewable energy. Fossil fuels are not renewable
(unless we can wait 100 million years). But wind power renews itself every
day as the Sun energy creates uneven heating and wind is produced. California
has been using wind power for quite awhile. Arizona will start its first
wind farm this year near the northeastern town of St. Johns. I have a trailer
near there, and will vouch for the high winds that come through there. Many
of my neighbors use wind generators. |
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NUCLEAR POWER makes
up a small fraction of the power in the US; however, the Palo Verde nuclear
plant near Phoenix, is responsible for a large percent of Phoenix's electrical
power.
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SOLAR
ENERGY captured with photovoltaic
cells (solar cells). Photovoltaic gets its name because the energy
of light (photo) is used to create voltage
(voltaic). Photovoltaic cells offer a simple
way to get electricity, at least DC (direct current) electricity used in
charging batteries. The problem with photovoltaic cells is that they are
expensive. It would take three $150 photovoltaic panels to operate the light
bulb in your refrigerator. I remember 25 years ago when engineers were promising
a big drop in solar cell prices was "just around the corner."
Well, I'm still waiting. Photovoltaic cells also only convert about 15%
of the sunlight to electricity. |
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Another approach
of using the Sun's energy is to focus the heat from the Sun (infrared light)
onto a tube filled with oil. The heated oil is then pumped to an adjacent
generating plant that uses the heat to make steam, which then pushes on
turbines hooked to electric generators. The polished metal reflectors are
cheaper than photovoltaic cells. Even though these panels are fairly simple,
you must have steam-powered turbines and electrical generators attached
to these collectors. |
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When done on a large
scale, thousands or millions of watts of electricity can be generated from
the free energy of the Sun. Even though the energy is free from the Sun,
it takes about 20 to 30 years to recover the cost of setting up a solar
power station. But one good thing about solar is that in hot climates it
produces the most energy at the time it is needed the most, like for air
conditioning. |
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Passive Solar
Heating. We should also include passive solar heating.
The panels are not photovoltaic cells; they are just black metal behind
panes of glass. Air or water passes over the dark metal backing that gets
hot from the Sun. The hot air or hot water is used to heat the home or to
assist the hot water heater. They are relatively cheap to purchase and install.
The downside, is that they are just for the home they are attached to. This
heat energy can't be distributed to other places. |
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Animal Power:
Lest we forget, for the majority of mankind's history, the source of power
for the chores we had to do was our own body's power plus maybe that of
an animal. This was pretty much the limit of our energy consumption. Cooking
was done with wood or animal dung. |
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PonyPower vs.
HorsePower: Before the days of machine power, mines
used ponies to pull carts of coal or ores or to turn pulleys to lift the
coal or ore to the surface. Ponies could lift 220 lbs 100 feet in about
a minute. Energy can be defined as force times distance. So here the force
to overcome is 220 lbs, and the distance is 100 feet. So the energy is 220lbs
x 100 ft = 22,000 ft-lbs. Power is energy consumption within a set amount
of time. Here it would be 22,000 ft-lbs per minute. James Watt, the inventor
of the new steam engine wanted his engines compared to power of horses,
which people were accustomed to. |
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James Watt knew the power of ponies
was about 22,000 ft-lbs per minute. He figured a full-size horse would
be about 50% stronger meaning it could lift 330 lbs 100 feet per minute
(33,000 ft-lbs. per min). So that became the definition of one horsepower.
A ten horsepower steam engine could do the lifting of 10 horses (or 15 ponies). |
| Human Power:
A friend of mine, Paul Walters, was hired to be a bicyclist at the Mountain
Dew Amp drink event at SuperBowl 42. They had forty-two bicyclists
pedal for 12 hours per day for total of four days. |
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Human Power:
Each bike had their rear tire in contact with a generator.
So as the bicyclist pedaled they produced electricity. |
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AMP Drink Power:
The purpose of the event is to show all these bicyclist getting energy
from guzzling the high sugar, high caffeine, high herbal stimulant liquid.
All this to provide power for the pregame show. What a great idea...
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Human to Electrical Power: Large
banks of batteries captured all of this energy from the 42 bicyclists
pedaling 12 hours a day for 4 days.
Cash in the Power: At
the end of 4 days and hundreds of Amp drinks, a meter had kept track of
the total amount of energy generated. Remember, it amounted to 42 athletic
bicyclists pedally 12 hours a day for four days. That multiplies out to
be equivalent to 2,016 hours of one bicyclist pedalling.
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The electric meter reads 38 kilowatt-hours, which can
be interpreted as 38 kilowatts for one hour (like an air conditioner running
for one hour) or 1 kilowatt (like a toaster) running for 38 hours. At
a cost of about 8 cents per kilowatt-hour, all of this effort produced
only 3 dollars of electricity! Yes, only
3 dollars of electricity. This either means that electricity is terribly
cheap or that we humans are very
weak power sources.
What scares me is if we had to depend on our own legs
to create electricity, we are in big trouble. Look at how many watts we
can maintain. 38 kilowatt-hours = 38,000 watt-hours. Divide this by 2,016
hours of bicycling, we get about 19 watts. In other words, if we had a
athletic bicyclist pedalling away all day, we could only operate electronic
devices with 19 watts or less. We would have to have 5 bicyclists just
to turn on one 100 watt bulb. So without alternative power, our society
would quickly revert back to the days of horse drawn carriages and horse
powered everything.
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What
are the consequences of using energy?
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The positive consequence is that we have the energy to
make the products we want, travel to where we want, keep ourselves warm
or cool, and to power all of the appliances and devices we like in our
lives.
The negative consequences can be categorized as inescapable
consequences and unfortunate consequences.
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INESCAPABLE CONSEQUENCES:
The laws of physics cannot be broken. One such law states the impossibility
of ever making a perpetual motion machine, which is a machine that does
work without any extra energy going into it. In the beginning of the industrial
revolution, attentioned focused on the efficiency of machines. Factory
owners wanted machines that could either provide work without added energy
or at least do work with 100% efficiency. The result of the research was
that neither was possible.
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INESCAPABLE CONSEQUENCES:
The picture on the left is a perpetual motion design. The
water in the upper trough pours out on the water wheel on the right. The
water wheel turns and the craftsman uses the left wheel for grinding.
The tilted corkscrew apparatus is called the Archimedes screw which has
the ability to raise water if the screw turns. The water wheel is suppose
to provide power for the grinding wheel and the Archimedes screw that
will replenish the water to the upper trough. Like all Perpetual Motion
Designs, the flaw is that energy gets wasted as heat and there's never
enough energy to keep the machine moving. In this example, the falling
water will not have enough energy to turn wheels and gears and also pump
the same amount of water back into the trough. The friction of the gears,
water stirring, and water flowing will turn the potential energy of the
raise water into heat.
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INESCAPABLE CONSEQUENCES:
Energy lost to heat is the final outcome of most anything we do with energy.
Let's examine the above collage. The locomotive's purpose is to pull railroad
cars from one place to another. However, nearly all of the energy it consumes
goes to creating heat rather than moving the cargo. The steam engine or
gas engine gets its power by heating a gas which expands and pushes on
pistons which turns the wheels. The hot gas is then released (exhausted)
so the pistons can return to their original position. The heat energy
in the gas is now lost to the environment and no longer available to produce
motion.
The weight lifter gets calories from food for energy to
lift weight and maintain the body's metabolisum. Only about 20% of the
calories gets used by the body, the rest is lost to heat that escapes
to the surrounding air. Even the energy in the raised weight will get
lost when it hits the floor and warms the spot on the floor where it hits.
Electricity turns a piston in the air compressor to compress
the air. The air gets quite hot as it has its molecules pushed closer.
This heat energy could provide additional potential energy and pressure.
However, the heat quickly dissipates through the metal walls of the compressor
and is lost.
The wind generators get energy from the wind. However
as the propellors turn, some energy is lost by friction of the bearings.
As it generates electricity the friction of electrons travelling through
the wires produces heat, which reduces the efficiency of the generator.
In other words, whenever we use energy, most, if not all,
will be lost as heat that will no longer be available for doing useful
work.
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| Losing so much energy to wasteful
heat is depressing, but another law of physics is even more depressing... |
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If your life seems more chaotic
as time goes by, don't feel alone. All of the universe is experiencing the
same problem. When energy is used, more disorder (chaos) is created. In
physics this is called "entropy," a measure of disorder often
resulting from heat. |
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For example, the atoms of carbon
and hydrogen in gasoline are lined up neatly in chains. After energy is
released, the atoms are scattered and randomized. In other words, car exhaust
has much higher entropy (disorder) than does gasoline and oxygen. In part
because exhaust is a gas, which is bouncing in all directions. The extra
heat causes even more random movements. |
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A warm homogenous
soup. Because
of this law which states all natural events lead to ever increasing disorder
and wasted heat, a prediction of how the universe will end has been made.
When the universe reaches uniform temperature and maximum randomness, we
can no longer extract energy to do work or to survive. Don't worry. If true,
it's still billions of years from now. |
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CONSERVATION OF
ENERGY: Another inescapable consequence of energy
is that energy is conserved. In other words, it doesn't go away, it just
changes form. The simplest change of form to see is the pendulum.
At the top of the pendulum swing, the ball
comes to rest momentarily. At that point it
has no kinetic energy, but it is at the maxium
height, so it has the maximum potential energy.
At the bottom of the swing, it is moving the
fastest (highest kinetic energy) but has the
lowest potential energy. So the energy transforms from one to the other
continually. |
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Friction convert Energies to Heat Energy:
In theory a pendulum should swing forever, but we all know that it will
slow down and stop. That's because the movement of the pendulum is knocking
against air molecules. The oxygen and nitrogen molecules in the air move
about 1,000 miles per hour; however, when they strike the pendulum ball
that's moving about 10 miles an hour, the air molecules get a boost of
speed increase to about 1,010 miles per hour. So some of the kinetic energy
of the pendulum is getting transferred to the air molecules. This extra
speed in the air molecules actually means the air is now a little hotter.
Also, there's little friction at the top where the wire is attached to
the hook at the top. If a pendulum was swinging in a vacuum and the top
hook was made with magnets that don't touch, then it would swing forever
(at least a long time since you can't isolate the pendulum completely
from the universe).
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UNFORTUNATE CONSEQUENCES
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Greenhouse Gases and Pollution:
Most of our energy comes from fossil fuels. The unfortunate consequences
of this as you learned is that at a minimum it produces the two global
warming (greenhouse) gases of water vapor
and carbon dioxide. Since burning of fuels
is done with air instead of just oxygen, we get nitrogen
oxides forming. These are toxic and contribute to pollution. If
the fossil fuels have impurities, such as sulfur, these impurities will
end up in the air we breathe.
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The energy in lightning splits oxygen molecules.
These atoms of oxygen are very reactive and will immediately combine with
other gases they encounter. If one bumps into nitrogen, it will form dinitrogen
oxide. If it hits an oxygen molecule, it forms ozone.
Both are toxic. Additionally, any sources of high
voltage or electric sparks can do the same thing. Copy machines,
laser printers, electric drills, spark plugs, bug zappers, vacuum cleaners,
TV sets, and other similar devices can produce these toxic products. High
energy can produce molecules of high energy, which are often dangerous.
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