Environmental Engineering Reference
In-Depth Information
Chapter 5: Energy Resources and
Consumption
A variety of sources provide the energy necessary to power developing and industrialized societies. Fossil
fuels, which included coal, oil, and natural gas, are the result of millions of years of decay of organic material
deep within the Earth. Humans now extract these resources in order to harness the stored energy through com-
bustion processes. Alternative fuel sources, such as hydroelectric power and nuclear power, have been used for
many generations. New advancements in energy production have led to new types of energy sources, such as
solar, wind, biomass, hydrogen, geothermal, tidal, and wave energy. Now more than ever, the importance of
addressing both energy production and consumption on a global scale is at the forefront of modern society.
Conservation initiatives and sustainable sources are becoming the focus of the energy industry and societies as
a whole.
Energy Concepts
Energy comes in many forms, both natural and man-made. Forms of energy include mechanical, thermal,
chemical, nuclear, electrical, and electromagnetic. Energy measures the ability of an object to perform work
and to move objects. Energy can be transferred or converted from one form to another. There are two forms of
mechanical energy: potential energy and kinetic energy. Energy possessed by a moving object is called
kinetic
energy.
A stationary object has
potential energy
if its position can be converted into movement. If you sus-
pend a coin from your fingers as if you are going to drop it, but you don't let it fall, the coin has potential en-
ergy, or energy stored in a system or an object. If you drop the coin, as it falls through the air it has kinetic en-
ergy, or energy due to its motion.
Forms of Potential and Kinetic Energy
Potential Energy
Kinetic Energy
Chemical energy
is the most practical form of energy. It is
a chemical reaction between bonds of atoms to form molec-
ules. Chemical energy is converted to thermal energy when
we burn wood in a fireplace.
There are two types of chemical reactions: endothermic and
exothermic. Endothermic reactions take in heat energy;
thus, providing no usable energy. Exothermic reactions re-
lease energy during the reaction. For example, when we
burn coal in the presence of oxygen, we get carbon dioxide,
water, pollutants, and energy. The chemical reaction is
Thermal energy,
or heat energy, is the energy
created by the movement of molecules within a
substance. As a substance gets warmer, the vi-
brations of the molecules within that substance
increase. When boiling water, for example,
thermal energy is added to the bottom of a pot.
This thermal energy is transferred across the
pot, into the water, and the water molecules
move faster. Eventually, enough heat is added
to boil the water, and as the water boils, it
quickly turns to steam.
Mechanical potential energy
is energy stored in objects by
tension or position. A stretched rubber band is an example
of stored mechanical energy, as are objects held above the
ground. Gravitational energy is also classified as a type of
mechanical energy.
Kinetic (electromagnetic) energy
is energy of
motion, which can be transformed into electrical
energy. One way to generate electrical energy is
to turn a generator, which consists of coiled cop-
per wire and magnets. As the wire coil spins, it
