Coal
• Fossil fuel
• Carbon-rich material left over from decomposed prehistoric vegetation
• 37% of the electricity generated worldwide is produced from coal
• Readily combustible black or brownishblack sedimentary rock

Advantages
· One of the most abundant energy sources
· Versatile
· Comparatively inexpensive
· Can be used to produce ultra-clean fuel
· Can lower overall amount of greenhouse gases
· Leading source of electricity today
· Reduces dependence on foreign oil
· Current supplies may last
200 years
Disadvantages
· Source of pollution: emits waste, SO , Nitrogen
Oxide, ash
2
· Coal mining mars the landscape
· Physical transport is difficult
· Technology to process to liquid or gas is not fully developed
· Solid is more difficult to burn than liquid or gases
· Not renewable in this millennium
· High water content reduces heating value
· Dirty industry—leads to health problems

3.8 days

Natural Gas
• Fossil Fuel
• Found alongside other fossil fuels
• Must be thoroughly refined to derive Methane

Advantages
· Burns clean compared to coal, oil (less polluting)
· 70% less carbon dioxide compared to other fossil fuels
· helps improve quality of air and water (not a pollutant)
· does not produce ashes after energy release
· has high heating value of 24,000 Btu per pound
· inexpensive compared to coal
· no odor until added
Disadvantages
· not a renewable source
· finite resource trapped in the earth (some experts disagree)
· inability to recover all in-place gas from a producible deposit because of unfavorable economics and lack of technology (It costs more to recover the remaining natural gas because of flow, access, etc.)

6.4 days

Petroleum
• Fossil fuel
• Naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons
• Found in geologic formations beneath the earth's surface.

Advantages
· Oil is one of the most abundant energy resources
· Liquid form of oil makes it easy to transport and use
· Oil has high heating value
· Relatively inexpensive
· No new technology needed to use
Disadvantages
· Oil burning leads to carbon emissions
· Finite resources (some disagree)
· Oil recovery processes not efficient enough— technology needs to be developed to provide better yields
· Oil drilling endangers the environment and ecosystem

4.8 days

Wind
• Renewable energy
• The conversion of wind energy into a useful form of energy
• Can be done through turbines, mills, pumps, etc.

Advantages
· Continuous sources of energy
· Clean source of energy
· No emissions into the atmosphere
· Does not add to thermal burden of the earth
· Produces no healthdamaging air pollution or acid rain
· Land can be used to produce energy and grow crops simultaneously
· Economically viable
Disadvantages
· For most locations, wind power density is low
· Wind velocity must be greater than 7 mph to be usable in most areas
· Problem exists in variation of power density and duration
(not reliable)
· Need better ways to store energy
· Land consumption

Solar
• The generation of electricity from sunlight.
• Photovoltaic cells convert sunlight into electricity.
These are made from semiconductors like crystalline silicon, etc.

Advantages
· Solar panels give off no pollution after manufacturing.
· Produces electricity very quietly.
· Able to harness electricity in remote locations that are not linked to a national grid
Disadvantages
• Prices of highly efficient solar cells can be above
$1000, and some households may need more than one.
This makes the initial installation of solar panels very costly.
· Solar energy is only able to generate electricity during daylight hours.

Hydroelectric
• Renewable
• The production of electrical power through the use of the gravitational force of falling or flowing water

Advantages
· Expands irrigation
· Provides drinking water
· Supplies hydroelectric energy (falling water used to run turbines)
· Easier for third world countries to generate power (if water source is available)
Disadvantages
· Destabilizes marine ecosystems
· Dam building is very costly
· People have to relocate
· Some dams have to be torn down (Some older ones are not stable.)
· Restricted to areas with flowing water
· Pollution affects water power

Geothermal
• Renewable
• Power extracted from heat stored in the earth.
• From the Greek roots geo, meaning earth, and thermos, meaning heat

Advantages
• Sustainable
• Nearly emission free
• Very low cost
• Safe
Disadvantages o Can only occur where heated rocks are near the surface of the earth.
o May cause small aftershock earthquakes o Minor damage may take 1000 years to recover.
Possible Future Fuels
0 The production of geothermal energy can occur only in areas where hot rocks lie near Earth's surface

Biomass
• Renewable energy source
• Biological material that can act as fuel
• The most common example: lumber

Advantages
• Theoretically inexhaustible fuel source
• When direct combustion of plant mass is not used to generate energy (i.e. fermentation, pyrolysis, etc. are used instead), there is minimal environmental impact
• Alcohols and other fuels produced by biomass are efficient, viable, and relatively clean-burning
• Available throughout the world
Disadvantages
• Could contribute a great deal to global warming and particulate pollution if directly burned
• Still an expensive source, both in terms of producing the biomass and converting it to alcohols
• On a small scale there is most likely a net loss of energy--energy must be put in to grow the plant mass

1.2 days

Fission
• Certain substances called nuclear fuels undergo fission when struck by free neutrons and in turn generate neutrons when they break apart
• This makes possible a self-sustaining chain reaction that releases energy at a controlled rate in a nuclear reactor

Advantages
• Relatively little fuel is needed and the fuel is relatively inexpensive and available in trace amounts around the world.
• Fission is not believed to contribute to global warming or other pollution effects associated with fossil fuel combustion
Disadvantages
• Possibility of nuclear meltdown from uncontrolled reaction--leads to nuclear fallout with potentially harmful effects on civilians
• Waste products can be used to manufacture weapons
• High initial cost because plant requires containment safeguards

Fusion
• Fusion has occurred naturally for billions of years in stars
• Molecules are made to combine, and then separate, releasing great amounts of energy
• Often called “the future of energy”

Advantages
• The fuel for fusion reactions are readily available.
Deuterium and Tritium are virtually inexhaustible.
• Fusion produces only helium, a gas that is already in abundance in the atmosphere and will not contribute to global warming.
• Fusion has no problems with dangerous by-products.
Disadvantages
Scientists have not yet been able to contain a fusion reaction long enough for there to be a net energy gain.
Many countries are phasing out fusion research because of the failure to reach a breakthrough