What is an energy portfolio? Throughout history, people have generated and
used energy to live. This energy often comes from multiple sources that may include
wind, water, fossil fuels, or the sun. These energy options, and how we choose to
use them, make up a person’s or a region’s energy portfolio. Over time, the world’s
portfolio changes based upon the availability of resources and our technological
ability to use them.
Think of all the ways in which you use energy in your daily life to make things
work for you. Just today, chemical energy from gasoline may have powered a car or
bus to take you to school. You probably used electrical energy to turn on a light
or charge a cell phone. Later, thermal energy may be used to cook your dinner. In
almost everything we do, we rely upon energy. Can you imagine what life would be
like if you did not have gasoline to get around or electricity to power a light?
There was a time when people had fewer energy options than we have today. In fact,
several hundred years ago, people would burn wood and other forms of plant material
in order to meet most of their daily energy needs.
The Discovery of Fuel
People have always obtained energy from their food, but fire gave them the ability
to harness energy in new ways. Evidence suggests that as many as 1.5 million years
ago, early humans may have used fire to cook food, keep warm, and frighten animals
away.
These fires used wood and plant materials for fuel. A
fuel is a substance
that is consumed to produce energy. Remember that plants transform electromagnetic
energy from the sun into chemical energy that is stored within plant tissue. When
plant material is burned, the molecules react with oxygen. During this chemical
change, bonds are rearranged and potential energy is released in the forms of heat
(thermal energy) and light (electromagnetic energy). This process of burning a substance
to release stored energy is called
combustion.
Humans have always been innovative, discovering different ways of harnessing energy
from nature. For instance, over 5,000 years ago, ancient Sumerians and Egyptians
exploited the power of wind with sailboats. Evidence shows that horses were domesticated
up to 5,600 years ago, tapping into their energy for travel and work. The first
clear evidence of a water wheel points to the ancient Greeks, who used it to grind
grain over 2,000 years ago. All of these energy sources continue to be used in some
form today. However, as technology has evolved, new and more powerful forms have
emerged. Will you be able to help in the discovery of the next major energy innovation?
The discovery and use of fossil fuels set the stage for the industrialization of
the world. Fossil fuels are carbon-based fuels, such as coal, oil, or natural
gas, that are formed by the compression of plant and animal remains.
Coal burns hotter and longer than wood and soon became a preferred energy source.
People started using coal regularly to heat their homes. During the colonial days,
farmers in England and other parts of Europe would dig coal up from outcrops exposed
at Earth’s surface.
In the early 1700s, however, England faced an energy crisis. Most of the surface
coal had been consumed. Geologists knew that much more coal lay far beneath the
surface, but it was dangerous and difficult to mine. Mines dug deep in the earth
would easily fill up with water, putting miners in danger and making extraction
of coal difficult. People had to come up with something new in order to obtain the
energy they needed.
The Steam Engine
In 1769, a Scottish inventor named James Watt patented a steam engine that pumped
the water out of mines and enabled the large-scale mining of coal.
How did Watt’s steam engine work? First, coal was used to boil water. The resulting
steam expanded and exerted pressure to move a piston upward.
Once that piston reached a certain height, a valve opened and cold water was released
to cool the steam. Cooling the steam caused it to condense, take up less space,
and therefore released the pressure it was exerting on the piston. This caused the
piston to come back down again. Alternately creating and cooling steam produced
an up-and-down piston motion—the mechanical energy of the early steam engine. Connecting
the piston to a pump allowed water to be removed from mines, where far more coal
could be obtained than what was needed to power the engine.
With access to a huge amount of energy-rich coal from deep within the earth and
with a powerful new steam engine, an explosion of technology followed.
Once Watt and others could use steam pressure to move a piston, they were soon able
to add other mechanical devices to enable new forms of transportation. For instance,
crankshafts converted the piston’s up-and-down motion into a rotational motion that
could turn a wheel. This technology was used to power steam engines and steam boats.
The Internal Combustion Engine
The discovery of another fossil fuel—oil—enabled other, more advanced modes of transportation.
Oil is a form of petroleum, or “rock oil,” which includes natural gas and
tar. Like coal, petroleum is a fossil fuel, but it is formed by the compression
of plants and animals that once lived in a marine environment.
The first documented steam engine was developed in the first century A.D. by a Greek
mathematician named Hero of Alexandria. Hero’s “aeolipile” consisted of an air-tight
chamber that could rotate on a bearing, with curved nozzles sticking out of its
sides. Water was heated either in the chamber or in a separate basin to produce
steam that was piped into the chamber. The force of the steam through the pipes
caused the chamber to spin around.
As early as 3000 B.C., early Mesopotamians used petroleum to make things, such as
medicine and roads. In the mid-1800s, oil began to be used more and more for heat
and light in the United States. But the U.S. petroleum industry really began in
1859, when a Pennsylvania railroad conductor named “Colonel” Edwin L. Drake struck
oil with a homemade rig that drilled down 21.3 m (70.0 ft) into the earth.
The ability to refine petroleum greatly enhanced the development of modern automobiles.
When crude oil is refined, petroleum products like gasoline, diesel, and propane
are separated for use. Though the earliest automobiles were steam powered, the development
of gasoline-powered cars began by the end of the 1800s. By 1908, Henry Ford’s assembly
lines were mass-producing automobiles that relied on gasoline.
Typical of many early cars, today’s automobiles also use an
internal combustion engine. In many ways, the internal combustion engine and Watt’s steam engine
are similar. In each case, the burning of a fuel causes a gas to expand and move
a piston. However, in the case of the internal combustion engine, the fuel is gasoline,
which is combusted inside the chamber, causing the pistons to move.
The Turbine Engine
In addition to engines that use pistons, inventors found a way to produce engines
that used turbines. A
turbine engine consists of a series of blades arranged
in a circle, like a wheel. A fluid, such as water, steam, air, or a combustible
gas, pushes against these blades, going in one side and coming out the other. In
this way, the wheel is made to turn around. A windmill is an example of a turbine.
At the end of the 19th century, many types of steam turbines began to emerge for
a variety of purposes. As technology advanced, turbines were adapted to utilize
various energy sources. Today, gas-powered turbines are used to power jet airplanes.
Other turbines are used in various ways, such as in manufacturing, on helicopters,
and even in space shuttles. Steam-powered turbines are still one of the main ways
we generate electricity today.
In the early 1800s, engineers proposed a design that directed steam straight onto
the blades of a turbine. Unfortunately, steel was not yet strong enough to hold
up to the stress of such rapid rotation. In 1884, a British engineer named Charles
Algernon Parsons used new steel technology that allowed a turbine to spin significantly
faster than ever before. As a result, in the early 1890s his steam turbine was used
in an actual power station to generate electricity.
