Conservation
of Energy
Your parent may tell you to conserve energy.
''Turn out the lights,” they say. But, to
scientists, conservation of energy means something quite
different. The law of conservation of energy says energy
is neither created nor destroyed. When we use energy, we
do not use it up--we just change its forms. That’s
really what we mean when we say we are using energy. We
change one form of energy into another.
A car engine burns gasoline, converting the chemical
energy in the gasoline into mechanical energy that makes
the car move. Old-fashioned wind mills changed the
kinetic energy of the wind into mechanical energy to
grind grain. Solar cells change radieant energy into
electrical energy.
Energy can change form, but the total quantity of energy
is the universe remains the same. The only exception to
this law is when a small amount of matter is converted
into energy during nuclear fusion and fission.
Energy
Efficiency
Energy efficiency in how much useful energy you can get
out of a system. In theory, a 100 percent
energy-efficient machine would change all of the energy
put in it into useful work. Converting one form of energy
into another form always involves a loss of usuable
energy, usually in the form of heat. In fact, most energy
transformations are not very efficient. The human body is
no exception.Your body is like a maching, and the fuel
for your machine is food. Food gives us the energy to
move, breathe, and think. But your body isn’t very
efficient most of the time, and rarely better than 15
percent efficient. The rest of the energy is lost as
heat. You can really feel the heat when you exercise!
An incandescent ligh bulb isn’t efficient either. A
light bulb converts ten percent of the electrical energy
into light and the rest (90 percent) is converted into
thermal energy (heat). That’s why a light bulb is so
hot to the touch. Most electric power plants are about 35
percent efficient. It take three units of fuel to make
one unit of electricity. Most of the other energy is lost
as waste heat. The heat dissipates into the environment
where we can no longer use it as a practical source of
energy.
Sources of
Energy
People have always used energy to do work for them.
Thousands of years ago, cave men burned wood to heat
their homes. Later people used the wind to sail ships. A
hundred years ago, people used falling water to make
electricity. Today people are using more energy than ever
before and our lives are undoubtedly better for it. We
live longer, healthier lives. We can travel the world, or
at least see it on television.
Before the 1970’s, Americans didn’t think about
energy very much. It was just there. Things changed in
1973. The Organization for Pertroleum Exporting
Countries, better known as OPEC, placed an embargo on the
United States and other countries. The embargo meant they
would not sell their oil to those countries. Suddenly,
our supply of oil from the Middle East disappeared. The
price of oil in the U.S. rose very quickly. Long lines
formed at gas stations as people waited to fill their
tanks with that precious, hard-to-get liquid that they
had taken for granted for so many years. Petroleum is
just on the many different sources of energy we use to do
work for us.
Energy Sources
Comsumption in 1998
| Natural
Resource: |
Percent
Consumption: |
| Petroleum |
38.1% |
| Natural Gas |
22.8% |
| Coal |
22.4% |
| Uranium |
7.6% |
| Hydropower |
3.7% |
| Biomass |
1.8% |
| Geothermal, Solar
and Wind |
.1% each |
| Other Energy
Sources |
.1% total |
The ten major energy
sources we use today are classified into two broad
groups--renewable and non-renewable.
Nonrenewable energy sources are the kind we use most in
the United States. Coal, petroleum, natural gas, propane,
and nuclear energy are nonrenewable energy sources. They
are used to make electricity, to heat our homes, to move
our cars, and to manufacture all sorts of products from
candy bars to CD’s. These energy sources are called
nonrenewable because they cannot be replaced. Petroleum,
for example, was formed millions of years ago from the
remains of ancient sea life, so we can’t replace our
supplies. We could run out of nonrenewable sources some
day.
Renewable energy souces include biomass, geothermal,
hydropower, solar, and wind. They are called renewable
energy sources because their cupplies are replentished.
Day after day, the sun shines, the wind blows, and the
rivers flow. We use renewable energy sources mainly to
make electricity.
Speaking of electricity, is it a renewable or
nonrenewable energy source? The answer is neither.
Electricity is different from the other energy sources
because it is a secondary source of energy. That means we
have to use another energy source to make it. In the
United States, coal is the number one fuel for generating
electricity.
Energy Use
Imagine how much energy you use every day. You wake up to
an electric alarm clock. You take a shower with water
warmed by a hot water heater. You listen to music on the
radio as you dress. You catch the bus to school. And
that’s just some of the energy you use to get you
through the first part of your day! Every day, the
average American uses about as much energy as is stored
in seven gallons of gasoline. That’s every person,
every day. Over a course of one year, the sum of this
every is roughly equal to 2,500 gallons of oil. Energy
use is sometimes called energy consumption.
|
Some people are beginning to
once again see the efficiency of using windmills to
conserve energy. See the discussion of conservation of
energy across.
Incandescent light bulbs are not always the best way to
light a room. They only use about 10% of the available
current to burn the light and the rest is given off as
heat!
This working oil refinery takes raw petroleum and
converts it into energy that we can use. As you can see
from the table (across) petroleum is the #1 consumed
energy source in America. |
