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2/6/2015
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Nonrenewable Energy Resources
February 6, 2015
Mr. Alvarez
Nonrenewable Energy
Nonrenewable Energy- fossil fuels (coal, oil, natural gas) and nuclear fuels.
Energy Use
Commercial energy sources- those that are bought and sold, such as coal, oil and natural gas.
Subsistence energy sources- those gathered by individuals for their own use such as wood, charcoal and animal waste.
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Processes of Energy Use
Generating Electricity
• The burning fuel from coal transfers energy to water, which becomes steam.
• The kinetic energy contained within the steam is transferred to the blades of a turbine, a large device that resembles a fan.
• As the energy in the steam turns the turbine, the shaft in the center of the turbine turns the generator.
• This mechanical motion generates energy.
• Most coal burning power plants are about 35% efficient.
Energy Efficiency
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Cogeneration
• Cogeneration- using a fuel to generate electricity and to produce heat.
– Ex: If steam is used for industrial purposes or to heat buildings it is diverted to turn a turbine first.
• This improves the efficiency to as high as 90%.
Overall Fuel Efficiency of Automobiles
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Energy Flowchart for the United States
Fossil Fuel Formation
Same 4 steps for all fossil fuel formation:
1. Accumulation of organic remains underwater (with no decomposition of the biomass!)
2. This biomass is buried under sediment layers.
3. Heat and pressure increase as burial occurs.
4. Biomass is “cooked” into fossil fuels.
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Coal Formation
Coal- forms from the remains of land plants – Most was formed from huge forests ~300m yrs ago – Most abundant fossil fuel in the world (200 yr supply)
• As it is buried and heated it passes through
several stages: 1. Peat (not a coal) 2. Brown coal (lignite) 3. Bituminous Coal 4. Anthracite
Fig. 16-12, p. 368
Increasing heat and carbon content
Increasing moisture content
Peat (not a coal)
Lignite (brown coal)
Bituminous (soft coal)
Anthracite (hard coal)
Heat Heat Heat
Pressure Pressure Pressure
Partially decayed plant matter in swamps and bogs; low heat content
Low heat content; low sulfur content; limited supplies in most areas
Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content
Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas
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• Coal is mined in 2 ways:
1. Subsurface mine shafts
2. Strip mining
• Subsurface mining: low surface impact, but dangerous to miners:
– Mineshafts can collapse.
– Methane gas in shafts can explode
– Coal dust long-term lung problems (“black lung”)
• Thousands of miners die every year while mining coal in subsurface mineshafts
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•Subsurface Coal Seam Fires in mineshafts can burn for decades! (~10,000 burning right now)
2. Strip Mining
• Habitat destruction (low rate of successful restoration despite 1977 SMCRA law)
• Erosion & Landslides
• Airborne dust hazards
• Tailings can pollute waterways
19_14.JPG
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Environmental Hazards of Coal
• Coal contains sulfur, and when water comes in contact with coal, it produces sulfuric acid (H2SO4) and leads to acid rain or acid drainage.
• Sulfuric acid drainage from coal mines pollutes surrounding waters long after mines are closed.
• West Virginia, Kentucky & Pennsylvania have worst problems (states w/ most coal mining)
Sulfuric Acid Drainage
Flooded Coal Mine
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Coal Combustion
• When burned, coal produces the most CO2 of all FF & significant amounts of air pollution (esp. SO2 and NOx and Hg), causing acid rain.
19_SBS01-02.JPG
Only ~35% efficiency!
Clean Coal?
• Some technologies exist to make “clean coal”.
– Capturing CO2 & other pollutants after burning
– Gassifying raw coal in to Syngas before burning
– Fluidized Bed Combustion combines coal w/ limestone to reduce Sulfur emissions
• Many of these are already in use, but it’s very costly to install these on old power plants.
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http://www.grantowngrammar.highland.sch.uk/subjects/Peak%20Oil%20web%20site/Formation%20of%20Fossil%20Fuels.html
Advantages Disadvantages
Energy-dense Contains impurities
Plentiful Release impurities into air when burned
Easy to exploit by surface mining Trace metals like mercury, lead, and arsenic are found in coal
Technological demands are small Combustion leads to increased levels of sulfur dioxide and other air pollutants into the atmosphere.
Economic costs are low Ash is left behind
Easy to handle and transport Carbon is released into the atmosphere which contributes to climate change
Needs little refining
Advantages and Disadvantages of Coal
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Oil/Gas Formation
• Oil & Natural Gas form from trillions of algae, phytoplankton and bacteria.
Oil/Gas Deposit Structure:
Hydrocarbons:
• The longer the chain, the more stable the molecule is
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•Crude oil (a.k.a. petroleum) is boiled during fractionating to separate different compounds.
• The longer the hydrocarbon chain, the higher the boiling point.
Fractioning Column
Unconventional Oil • Bitumen (tar or pitch)- a degraded type of
petroleum that forms when a petroleum migrates close to the surface, where bacteria metabolize some of the light hydrocarbons and others evaporate.
• Oil sands- slow-flowing, viscous deposits of bitumen mixed with sand, water, and clay.
• Despite the gulf oil spill, deepwater drilling has been relatively safe over many years.
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Environmental Impacts of Oil Drilling
• Construction of drilling rigs causes Surface disturbance & disruption of ecosystems.
• Spills and leaks from rigs or pipelines/tankers that are transporting oil.
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Advantages and Disadvantages of Petroleum
Advantages Disadvantages
Convenient to transport and use Releases carbon dioxide into atmosphere
Relatively energy-dense Possibility of leaks when extracted and transported
Cleaner-burning than coal
Releases sulfur, mercury, lead, and arsenic into the atmosphere when burned
Natural Gas • Natural gas- exists as a component of
petroleum in the ground as well as in gaseous deposits separate from petroleum.
• Contains 80 to 95 percent methane and 5 to 20 percent ethane, propane, and butane.
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Advantages/Disadvantages of Natural Gas
Advantages Disadvantages
Contains fewer impurities and therefore emits almost no sulfur dioxide or particulates
When unburned, methane escapes into the atmosphere
Emits only 60% as much carbon dioxide as coal
Exploration of natural gas has the potential of contaminating groundwater
The Hubbert Curve
Hubbert curve- a graph that shows the point at which world oil production would reach a maximum and the point at which we would run out of oil.
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The Future of Fossil Fuels
• If current global use continues, we will run out of conventional oil in less than 40 years.
• Coal supplies will last for at least 200 years, and probably much longer.
• Fission- a nuclear reaction in which a neutron strikes a relatively large atomic nucleus, which then splits into two or more parts.
Nuclear Energy
48
How Do Nuclear Reactors Work
• Most commonly used fuel is U235, a naturally occurring radioactive isotope of uranium. – Occurs naturally at 0.7% of uranium, but must be
enriched to about of 3% to create a fuel pellet.
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Nuclear Reactors
• Nuclear power plants work by using heat from nuclear fission to heat water. This water produces the steam to turn the turbine, which turns a generator.
• Fuel rods- the cylindrical tubes that house the nuclear fuel used in a nuclear power plant.
• Control rods- cylindrical devices that can be inserted between the fuel rods to absorb excess neutrons, thus slowing or stopping the fission reaction.
Nuclear Reactors
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Controlling the Chain Reaction
Control rods
Fuel
Assemblies
Withdraw control rods,
reaction increases
Insert control rods,
reaction decreases
“Heavy
Water” as
mediator
53
Pressurized Water Reactors (PWR)
• Seventy percent of nuclear power plants are pressurized water reactors.
• Water is circulated in a separate line through the core to absorb heat from fuel rods.
• Pumped to steam generator where it heats a secondary loop.
• Steam from secondary loop drives high-speed turbine producing electricity.
Summary: How Nuclear Energy Works
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• Each atom of U-235 produces 3 neutrons
–one starts next reaction
–two can convert U-238 to Pu-239
–More energy can be created than used (breeding)
• Breeder reactors can greatly extend the lifetime of resource availability but increase the damage in case of disaster
BREEDER REACTORS
Radioactive Waste Management • Low-Level Radioactive Waste
– Waste materials that contain sufficiently low concentrations or quantities of radioactivity so as not to present a significant environment hazard if properly handled
– Contaminated clothing rags, tools, etc.
• High-Level Radioactive Waste – Extremely toxic nuclear waste, such as spent fuel
elements from commercial reactors.
– How do we dispose of this waste material?
Dealing with Nuclear Waste: Options
• Undergound burial
• Disposal in space
• Burial in ice sheets
• Dumping into subduction zones
• Burial in ocean mud
• Conversion into harmless materials
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20_13c.JPG
• Warm water is returned to the environment (thermal pollution)
• Fish get ground up in entry pipes
• Manatees love to stay over-winter in the warm water!
COOLENT WATER
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Comparing Coal & Nuclear: IMPACTS
Nuclear Power Plant Accidents • Three Mile Island (1979)
– Pennsylvania
– The most serious US accident
• Chernobyl (1986) – Worst accident in the history of
commercial nuclear power
– Because of this, it is theorized that in the next 20 to 30 years, there will be an increase in cancer in northern Europe.
• Fukushima (2010) – Earthquake Tsunami
Damage to reactor cooling system leaking radioactive water
– Unknown effects on humans & ecosystems
Advantages Disadvantages
No air pollution is produced Possibility of accidents
Countries can limit their need for imported oil
Disposal of the radioactive waste
Advantages and Disadvantages of Nuclear Energy
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