energy lecture 7

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Enger & Smith

Environmental ScienceA Study of Interrelationships

Thirteenth Edition

Chapter 9

Non-Renewable Energy Sources

Non-Renewable Energy Sources

9.1 Major Energy Sources Nonrenewable energy sources

• resources are being used faster than can be replenished.

– Coal, oil, and natural gas

Renewable energy sources • replenish themselves • feature of the environment.

– Solar, geothermal, tidal, etc.

– 12% of the energy used worldwide

– hydroelectricity and firewood

9.3 Fossil-Fuel Formation

Coal• 300 million years ago, • plant material—underwater--decay • forming a spongy mass of organic material.

• Due to geological changes – deposits were covered by seas– covered with sediment.

• Pressure and heat over time – transformed the organic matter into coal.


Recoverable coal reserves of the world 2004


Oil and natural gas • microscopic marine organisms • accumulated on the ocean floor • covered by sediments.

• Muddy sediment formed shale – contained dispersed oil.

• Natural gas often forms on top of oil– Due to higher temps


Crude oil and natural gas pool

9.4 Issues Related to the Use of Fossil Fuels

Fossil fuels supply 80% of world’s commercial energy.

Coal is most abundant fossil fuel.• Only 30% of world energy is from coal• Primarily used for generating electricity.


Extraction methods:• Surface mining (strip mining),

– removing material on top of a vein

– efficient but destructive

• Underground mining– Minimizes surface disturbance, but is costly and

dangerous.


Underground mining


• Health and Safety Issues– 2000-2010, 60 deaths per year

– Many miners suffer from black lung disease– a respiratory condition – results from the accumulation of fine coal-dust particles

in the miners’ lungs.


Transportation Issues• Coal is bulky• Use railroad

Landscape Disturbance• Mountain top removal• Minimize disturbance

– Reclaiming area – Mining companies do little to lower their costs


Surface-mine reclamation

Underground MiningSubsidence-sinking of land

Subsidence


Environmental Issues• Burning coal releases pollutants

– (carbon and sulfur).– Released into atmosphere annually.

• Sulfur leads to acid mine drainage and acid deposition.


Acid mine drainage

• Air Pollution– Mining creates dust pollution– Mercury is released into the air when coal is burned.

• Increased amounts of atmospheric carbon dioxide are implicated in global warming.



Oil (35% world energy)

• more concentrated than coal• burns cleaner• transported through pipelines

• Ideal for automobile use.• Difficult to find.• Causes less environmental damage than coal mining.


Source of oil--located extracted and transported to the surface

Primary Recovery methods• Water/gas pressure is great (with oil)

– oil is forced to the surface---when well is drilled

• Water/gas pressure is low– oil pumped to the surface

• 5–30% (primary)


Offshore drilling


Secondary Recovery• Water or gas is pumped into a well • drive the oil out of the pores in the rock

• 40% of the oil---extracted.


Processing • From the ground, oil is not in a form suitable for use

– must be refined.

– Separate components by – Heat oil in distillation tower

• Multiple products can be produced from a single barrel of crude oil.

– Plastics, rubber, etc


Processing crude oil


Oil Spills• Accidental spills

– about 1/3 of oil pollution resulting from shipping.

2010 Deepwater Horizon: 10,000 tons of oil largest spill

Discussion http://www.tv.com/shows/pbs-newshour/watch/environment-economy-at-he

art-of-keystone-xl-pipeline-debate-1980889/

Eminent Domain• The power to take private property for public use by a state,

municipality, or private person or corporation (authorized to exercise functions of public character)

• following the payment of just compensation to the owner of that property

http://www.tv.com/shows/pbs-newshour/watch/environment-economy-at-heart-of-keystone-xl-pipeline-debate-1980889/



Keystone XL pipeline route


Natural gas • Drilling operations similar to oil.

Hard to transport • burned off at oil fields (waste product)

• New transportation methods – Liquefaction at -126o F

– Tankers transport liquefied natural gas

• Unloading/loading facilities – located off shore (explosions)


Least disruptive

to environment

Air Pollution

minimal

Fracking

9.5 Nuclear Power

Nuclear power • Not a fossil fuel• fueled by uranium

– obtained from mining and is non-renewable.

– 5th most important energy

Does not produce CO2

Less costly than oil/natural gas• For electricity (developing nations)

As of 2011 • 440 nuclear power reactors in operation and • 61 plants under construction in 13 countries.

9.5 Nuclear Power

104 Nuclear Power Plants in U.S.

9.6 The Nature of Nuclear Energy

The nuclei of certain atoms • unstable and spontaneously decompose• isotopes are radioactive.

Neutrons, electrons, protons, other particles• released during nuclear disintegration• great deal of energy

Atomic Structure

Isotopes of hydrogen

9.6 The Nature of Nuclear Energy

Nuclear disintegration (releases energy)• from the nucleus as radiation• three major types

– Differ by size and how fast it travels

Radioactive half-life • time it takes for half the radioactive material to

spontaneously decompose.

9.7 Nuclear Chain Reaction

Nuclei• Release radiation• And Neutrons

Nuclear fission occurs when neutrons impact and split the nuclei of certain other atoms.• Split (Fission)

Nuclear Chain Reaction

splitting nuclei release neutrons,

which themselves strike more nuclei,

in turn releasing even more neutrons.

9.8 Nuclear Fission Reactors

A nuclear reactor is a device that permits a controlled fission chain reaction.• Nucleus of Uranium-235 atom struck by a slowly

moving neutron • the nucleus splits into smaller particles• Causes rapidly-moving neutrons to be released

– which strike more atoms.

• continues to release energy – until the fuel is spent (Uranium-235)

– or the neutrons are prevented from striking other nuclei.

Nuclear chain reaction

Need• The fuel (uranium-235)• A moderator• Control Rods• Core coolant


Control rods • lowered into the reactor to absorb neutrons • and control the rate of fission.• When withdrawn, the rate of fission increases.

Moderator • substance that absorbs energy, • which slows neutrons, enabling them to • split the nuclei of other atoms more effectively.• Water

Coolant---usually water


Nuclear reactor• Produces heat• Water to steam• Turns turbine• Generate Electricity

Pressurized water-reactor

9.10 Issues Related to the Use of Nuclear Fuels

Concerns about the use of nuclear fuels • danger associated with radiation

• radiation interact with atoms, ions are formed– ionizing radiation– Ionizing radiation affects DNA and can cause mutations. – Cancer

– Large doses of radiation are clearly lethal.

The Biological Effects of Ionizing Radiation

Time, distance, and shielding are the basic principles of radiation protection.• Water, lead, and concrete are

common materials used for shielding

Three Mile Island Pennsylvania 1979

Partial core meltdown

Pump and valve malfunction

Radioactive steam into atmosphere

Reactor Safety

Chernobyl is a small city in Ukraine, north of Kiev. It is the site of the world’s largest nuclear accident,

which occurred April 26, 1986.• Experiments were being conducted on reactor.• Operators violated six important safety rules.

• Shut off all automatic warning systems, automatic shutdown systems, and the emergency core cooling system for the reactor.

Reactor Safety

In 4.5 seconds, the energy level of the reactor increased 2000 times.

The cooling water converted to steam and blew the 1102-ton concrete roof from the reactor.

The reactor core caught fire. It took 10 days to bring the burning reactor under

control.• There were 37 deaths; 500 people hospitalized (237

with acute radiation sickness); 116,000 people evacuated.

Reactor Safety

The accident at Chernobyl

Reactor Safety

The Fukushima nuclear power plant was damaged on March 11, 2011 following a magnitude 9 earthquake and tsunami.• Heat exchangers were damaged, power to the site

was cut off– diesel generators designed to provide power in an

emergency were flooded and stopped operating.

• Explosions, fires, and leaks in the cooling system released radiation into the atmosphere and sea water.

Other issues

Terrorism• radiological dispersal devices (RDDs), or dirty bombs.• They cause panic, not numerous deaths.

Waste• All of the processes involved in the nuclear fuel cycle

have the potential to generate waste.

Transport of radioactive materials.

Possibility of an accident or mishandling that could release radioactive material.

Decommissioning Nuclear Power Plants

The life expectancy of most electrical generating plants (fossil fuel or nuclear) is 30-40 years.

Nuclear plants are decommissioned, not demolished.

2-step process.• Stage 1 removing, properly disposing of, or storing

– fuel rods and water used in the reactor.

• Stage 2 Secure the plant to allow radioactive materials with a short half-life to disintegrate and then dismantle the plant.

– This should occur within 60 years.

Nuclear Plant

Nuclear plant in Nebraska (Fort Calhoun) 20 miles north of Omaha

• http://www.omaha.com/article/20131226/NEWS/131229264

http://www.omaha.com/article/20131226/NEWS/131229264

http://www.omaha.com/article/20131226/NEWS/131229264

Summary

Resources are naturally occurring substances of use to humans.

Reserves are known deposits from which materials can be extracted profitably with existing technology under present economic conditions.

Coal is the world’s most abundant fossil fuel. The supply of oil, like all fossil fuels, is limited. Natural gas is another major source of fossil-fuel

energy, but transport of natural gas to consumers is problematic.

Summary

Nuclear fission is the splitting of the nucleus of an atom.

All reactors contain a core with fuel, a moderator to control the rate of the reaction, and a cooling mechanism to prevent the reactor from overheating.

Summary

The nuclear fuel cycle involves mining and enriching the original uranium ore, fabricating it into fuel rods, using the fuel in reactors, and reprocessing or storing the spent fuel rods.

Fuel and wastes must also be transported. Each step in the process presents a danger of

exposure.

Summary

Although accidents at Three Mile Island and Chernobyl raised safety concerns for a time, rising energy prices have stimulated increased building of nuclear power plants in many countries.

Disposal of waste is expensive and controversial.• Long-term storage in geologically stable regions is

supported.• Russia, Japan, and the UK operate nuclear

reprocessing facilities to reduce future long-term storage needs.

energy lecture 7

Education

abundant fossil

fossil fuels

reactor safety

4 issues related

term storage

radioactive

natural gas

radiation