Energy
Energy Matters:
10-15% of the questions on the AP
Exam are about energy!
 Life depends on a constant flow of energy
 We have already studied the flow of energy through an
ecosystem
 Some societies have become dependent on
tremendous amounts of matter and energy to
maintain a comfortable lifestyle.
First a little review…
 Energy: is defined as the capacity to do work.
 2 Types:
Potential Energy: stored energy-energy at rest
Kinetic Energy: energy of motion
 Terms that describe the movement of energy:
Convection: transfer of heat by the movement of
heated matter in a fluid
Conduction: transfer of energy by direct contact
Radiation: energy from the sun
Units of Energy and Power
 Energy: Joule (J), Calorie (cal),
British Thermal Unit (BTU, and
kilowatt hour (kWh)
 Power units: Watt (W),kilowatt, and
(1000 watts), megawatt (million
watts), horsepower (hp)
It’s the Law
 Energy is the ability to do work
 Work is the movement of matter
 Law of conservation of energy (First Law of
Thermodynamics)-energy cannot be created or
destroyed, it can only change from one form to
another
 Types of energy: light energy, chemical energy, heat
energy, potential energy, mechanical energy
It’s the law
 The second law of thermodynamics- states that the
entropy (disorder ) of the universe is increasing.
When energy is changed from one form to another, a
portion of the energy is lost to the universe as heat.
Energy transfer…3 methods
 Convection-heat transfer by the movement of fluids
(gas or liquid)
 Conduction-heat transfer by direct contact
 Radiation-heat energy from the sun
Energy Efficiency
 Energy efficiency of an invention is a measure of the
amount of energy that can be turned into useful work.
 Models with higher energy efficiency require less fuel
to do work.
Net energy efficiencies of some
common inventions:
 Steam locomotive
 Diesel locomotive
 Internal combustion engine
 Oil furnace
 Natural gas furnace
 Electric heat from coal-fired plant
 Incandescent lamp
 Fluorescent lamp
8%
35%
10%
53%
70%
25%
5%
22%
Production of Electricity…
 One of our biggest uses of energy is in the production
of electricity-another form of energy!
 In general, electricity is produced the following way:
1. An energy source provides the power that heats up
water, transforming it to steam.
2. The steam turns a turbine
3. As the turbine spins, it causes a generator to produce
the electrical current.
4. In lieu of steam, flowing water or wind can also
provide the power to turn the turbine.
Where does our electricity come
from??
 Three main sources of global electricity production:
Fossil Fuels: provides 64 percent of the worlds
electricity
Nuclear Energy: provides 17 percent of the world’s
electricity
Renewable energy sources: provides 19 percent of the
world’s energy sources
Fossil fuels-energy for a nation
 Renewable resource-is a
resource that is produced
at least at the same rate
that it is used.
 Non-renewable
resource- a resource that
is not replaced by natural
cycles at least at the same
rate it is used up.
 Today most of the fuel that
we use is derived from non
renewable resources!! (oil,
natural gas, and coal)
Fossil Fuels
 35 percent of global
energy production is
from oil
 Oil, coal, and natural gas
make up 80% of the
world’s energy
production
 Formed from the
fossilized remains of
once living organisms.
Oil
 Consumption of oil in the US has increased
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dramatically over the last few decades.
Our production of oil has decreased making us
dependent on imports for much of our fuel
Two thirds of the world’s proven oil reserves is found
in the area surrounding the Persian Gulf.
In 1990, when Iraq invaded Kuwait, US forces were
sent to the area in part to protect the free flow of
oil.(The first Gulf War)
Political disputes and hurricanes sometimes slow the
flow of oil and affect prices.
It began a long time ago…
 Coal is formed from the remains of giant ferns and trees
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that died and fell into the water turning into a partially
decayed material called Peat.
Peat is then covered with layers of sediment and water
forcing it deeper into the earth
It is then affected by heat and pressure and turns into coal.
Coal refers to any black or brown rock that contains
hydrocarbons formed from decayed plants.
There a 4 different types of coal that contain different
percentages of carbon.
Coal is found in long, continuous deposits called Seams.
Four types of coal:
 Lignite: softest coal, is very soft and crumbles easily.
25-35% carbon content.
 Subbituminous-produces higher heat than lignite,
contains slightly more carbon (35-45%)
 Bituminous-also called soft coal. Takes more than
100 million years to form. 45-86% carbon content.
 Anthracite-hard coal. Highest percentage of
carbon.(86-98%). It has the highest heating value.
Nearly all the anthracite in the US is in Pennsylvania.
Supply and demand
Seams of coal on a hillside.
Coal
 Coal is our most abundant
fossil fuel. Nearly 75% of all
known coal reserves are in the
United States, China, and
countries of the former Soviet
Union.
 The US has 25% of the world
coal reserves
 Coal is our only source energy
for which our exports exceed
our imports.
Coal
Uses:
Mining:
 Coal is used mainly for the
 Most coal is produced in one
generation of electricity by
power plants.
 Some coal is used by industry
as a source of heat for various
industrial processes.
of two types of mines:
 Strip mining or surface
mining
 Or
 Underground mining
Strip mining
Strip mine
 Strip mines remove all of the
soil and rock lying over a coal
deposit (overburden) with
huge earth-moving machines.
In the past , strip mining
often left huge open pits that
were ugly and useless.
 A law passed in 1977 requires
coal companies to restore all
of the land that is strip
mined.
Reclamation
 The process of restoring the land to the condition that
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existed before mining is called reclamation.
Before mining begins, scientists study the soil, plants,
wildlife and water resources of the area.
During the mining the topsoil that has been removed
is stored in giant piles and planted to prevent erosion
After the mining is complete the soil and rock is
returned and planted. If necessary the land is
irrigated.
Reclaimed land can be used for lakes or reservoirs, or
for recreation.
Underground coal mining:
 The most common type of
underground mining uses
the room and pillar
system.
 As miners dig large rooms,
they leave pillars of coal to
support the roof
 Only 50-60% of the coal
can be removed using this
method.
 Useful when coal is buried
very deep.
More coal facts…
 Coal is used to generate electricity at more than 50% of the
power plants in the United States.
 Disadvantages of using coal include:
-burning of coal produces nitrogen oxides, mercury, and
sulfur dioxide-all of which contribute to air pollution
-burning of coal also produces fly ash and boiler residue
-coal often contains a significant amount of sulfur
-Some of the sulfur in coal can be removed by scrubbers,
which contain alkaline substances that precipitate out
much of the sulfur dioxide before it leaves the flue gases.
More coal facts
 Coal-fired power plants are the major source of
Mercury pollution in the environment
 Mercury is harmful to children and a developing fetus.
 An EPA study found that 1 in 6 women of childbearing
age might have levels of mercury in their bodies that
can be harmful to a fetus.
 Mercury can travel hundreds of miles through the air
and find its way into runoff and bodies of water and
eventually into the fish that we eat.
Environment and Health:
 Since 1900, more than
 Automatic detectors must
100,000 workers have been
killed in coal mine
accidents
 The federal government
passed the Coal Mine
Health and Safety Act in
1969, greatly reducing the
number of deaths
 Most deaths involve
accidents with machinery
now be used to detect
methane, a potentially
explosive gas often found
in coal seams.
 Blasting can produce
dangerous levels of carbon
monoxide if the mine is
not properly ventilated
Environment and Health
 Black lung is a
potentially fatal
condition developed by
thousands of miners.
 Black lung is caused by
inhaling coal dust
 Walls of mines must now
be sprayed with water to
decrease the amount of
dust.
Healthy lung tissue vs
Black Lung disease
Water pollution
 Water pollution occurs when water pumped from
underground mines or water from open pit mines
enters a stream without first being treated
 In the past, thousands of fish and aquatic organisms
have been killed by acid water from mine waste.
 Today, mines are required to treat the water and
remove the sediment before allowing the water to
enter a waterway.
Mine reclamation process in Telluride ,Colorado
Acid mine drainage at a mine near Longview, Texas
Natural Gas
 Natural gas is mostly Methane (CH4)
 Used for home heating and cooking
 Also burned to generate electricity (many of the
plants in the Dallas area burn natural gas-we have
a lot of it located nearby)
 Cars and trucks can be modified to burn natural
gas instead of gasoline.
 Cleaner than coal-Produces only carbon dioxide and
water when it burns (no oxides of sulfur or nitrogen)
Natural Gas-Barnett Shale
 The Barnett Shale is a geologic formation that contains
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large quantities of natural gas.
Located near Fort Worth
In order to make removal of the natural gas costeffective companies use a method of removal called
Hydraulic Fracturing (commonly called fracing)
Hydraulic fracturing is the process of creating fissures
(cracks) in the underground formations to allow gas to
more easily flow from a well.
A water mixture (called fracing fluid) is injected into
the well to create fractures in the rock
Hydraulic fracturing…
 Essential for the production of natural gas and oil from
shale formations
 Deep shale and natural gas formations occur many
thousands of feet below the surface
 The Barnett Shale is found from 6500 to 8500 feet
underground
 State laws require the installation of steel and cement
well casings to protect groundwater
Potential Environmental Issues
from Fracking
 Use LARGE quantities of water (70-140 billion gallons of water
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to fracture 35,000 wells in the US each year)
Mining impacts caused by the collection of sands for proppants
(hold the fractures open)
Toxic chemicals found in the fracing fluids
Health concerns caused by ingestion of or exposure to fracing
fluids
Surface water and soil contamination
Groundwater contamination
Degradation of air quality in areas with a lot of drilling(high
levels of benzene, a cancer-causing agent, have been found near
the Barnett Shale
Waste disposal
How long will our fossil fuels last?
 According to the Society of Petroleum Engineers:
 The oil will last about 44 years
 The natural gas will last about 66 years
 The coal will last 147 years
Nuclear power
 The fuel used in a nuclear power plant is mainly
uranium. (U-238 which is enriched with 3% U-235)
 When uranium atoms fission, or split apart, they
release huge amounts of energy
 Radioactive materials have half-lives, which is the
time it takes for half of the radioactive sample to
degrade.
 This energy heats water and creates steam that turns
turbines to produce electricity
Nuclear power
 Does not produce air pollution
 The normal operation of a nuclear power plant
releases less radiation than a coal burning power plant.
 The mining of both coal and uranium has destroyed
ecosystems
 Although it is non-renewable, the planet has a large
enough supply of uranium to last many years
Nuclear power
 Very expensive to build and operate
 Safety is a major concern.
 Accident at Three Mile Island Nuclear plant in 1979.
 Chernobyl Nuclear Plant in the Ukraine
 Storage of spent fuel is a problem. Many nuclear
plants around the world have been decommissionedprimarily because of problems with disposal of spent
fuel
The problem of radioactive waste…
 In the US, spent fuel from
nuclear power plants is
currently being housed at the
plants themselves. This is
only temporary.
 The proposed final
destination for much of our
nuclear waste is a storage site
at Yucca Mountain (in
Nevada) within the
boundaries of a former
nuclear weapons testing site
 This storage facility will not
be in use until 2017 at the
earliest.
Boiling water nuclear reactor
Renewable Energy
 Biomass
 Hydroelectric
 Solar
 Wind
 Geothermal
 Tidal energy
 Hydrogen cells
Biomass
 One of the most widely used forms of renewable
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energy
Includes wood, charcoal and animal waste products
Only renewable when used at a pace that allows it to
replace itself
Ethanol (which is made from corn)and biodiesel
(which is made from waste vegetable oil) are examples
of biomass energy sources.
There are also groups experimenting with creating fuel
from algae
Hydroelectric power
 Hydroelectric power is produced when the energy of
falling water turns a water turbine.
 Hydroelectric power is usually cheaper than electricity
produced by coal-burning power plants
 Hydroelectric power plants do not produce the air
pollution or heat associated with fossil-fuel burning
plants
Hydroelectric power
 A disadvantage of hydroelectric power plants are that
they have a significant impact on the environment
 Produces thermal pollution
 The amount of electricity produced by hydroelectric
plants is not likely to increase because most of the
good locations already have dams.
 Dams on rivers have huge impacts on wildlife and
plant populations within the river.
The Dam Problem…
 Dams cause silting: As water builds up behind the dam,
the normal sediments that it carries build up behind the
dam. This puts an additional strain on the structure and
means that dams have to be built to hold back many tons
of sediment.
 This also means that the sediment does not travel down
river as it normally would. The sediment that used to
fertilize the flood plains beyond the dam is now trapped.
 Reservoirs usually have a greater surface area than the river
did before the dam. This results in a higher rate of
evaporation and less water overall.
More Dam Problems…
 Fish that spawn in the normally silty river now do not
have a place to do so.
 Salmon breed in the streams where they hatched as
eggs. The dam prevents them from swimming
upstream to their birthplace.
 Fish ladders in dams do allow some fish to return
upstream, but not in the numbers that they did before
the dam was built and the populations decline.
Fish Ladders
Solar Energy
 Two types of solar energy: Passive and Active
 Passive solar energy: The use of building materials,
building placement, and building design to passively
collect solar energy. (such as through windows)
 Active solar collection: is the use of devices, such as
solar panels, that collect , focus, transport, or store
solar energy.
 Solar Panels: absorb solar energy and pass the energy
on to tubes in which water is circulating. This heated
water can be stored for later use.
Solar Energy
 Photovoltaic Cells-
produce electricity which
is then stored in
batteries
Solar energy
 Produces no air
pollutants
 Photovoltaic cells have
no moving parts and
require little
maintenance
 Not every location
receives enough
sunshine to make solar
energy worthwhile.
 expensive
Wind Energy
 The modern wind
turbine works by the
wind turning the blades
of the turbine and this
turns the machinery at
the base of the turbine.
 Wind energy is the fastest growing form of
alternative energy
Wind energy
 Turbines are usually placed into large groups called
Wind Farms
 In the United States, wind farms are primarily in
California and Texas.
 Many other locations have enough wind to make
electrical generation feasible.
 Wind farms can also be placed offshore.
Wind Energy
 At present, wind energy is more expensive than fossil
fuels because the wind turbines are expensive to buy
and maintain.
 Alternative energy source must be available for times
when there is not enough wind.
 Wind energy is clean-it produces no harmful
emissions.
Geothermal Energy
 Geothermal energy is the natural heat or hot water
trapped beneath the earth’s surface
 Can be used to heat homes, produce electricity, and
power industries.
 Must be in a location where geothermal sources are
relatively close to the surface.
 Geothermal power plant must be at the location
because too much heat and pressure is lost if
transported too far.
Geothermal energy
 Corrosive minerals in steam can damage pipes and
turbines
 At some sites, harmful gasses such as radon or
hydrogen sulfide are vented at the surface
 There are currently 17 geothermal “district “ heating
systems in the US
 Hawaii and Iceland have the greatest amount of
geothermal energy sources that are in use.
Hydrogen Fuel Cells
 Hydrogen fuel cells are considered by many to be the
best, cleanest, and safest fuel source.
 Free hydrogen is not found on Earth, but can be
released by the process of electrolysis-the separation
of hydrogen and oxygen in water.
 Once the hydrogen is released, it can be stored and
used to generate electricity through the reverse
reaction of electrolysis.
Hydrogen fuel cells
 The only waste is steam-water vapor
 Fuel cells are expensive
 Lack of hydrogen fuel stations has limited the
technology to just a few test programs
 Technology has been used for decades in spacecrafts
 In order for hydrogen to become a realistic option as a
renewable energy source, an inexpensive and efficient
way to produce hydrogen without using fossil fuels
must be developed (such as using solar energy)