Transcript Document

Ch 12 Energy
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Energy Sources and Uses
Coal - Oil - Natural Gas
Nuclear Power
Conservation
Solar Energy
– Photovoltaic Cells
• Fuel Cells
• Energy From Biomass
• Energy From Earth’s Forces
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Fossil Fuels
• Fossil fuels - organic chemicals that
were created by living organisms
millions of years ago, buried in
sediments, and transformed into
energy- rich compounds
• Because fossil fuels take so long to
form, they are essentially
nonrenewable resources.
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Coal Extraction and Use
• Mining - dangerous to
humans and the
environment
• Coal burning releases
large amounts of air
pollution, and is the
largest single source of
acid rain in many areas.
• Economic damages billions of dollars
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Oil Extraction and Use
• The largest supply of proven-in-place oil is in
Saudi Arabia.
• The countries of the Middle East control twothirds of all known oil reserves.
• The U.S. has already used up about 40% of its
original recoverable petroleum resource.
• Problems:
– Combustion - substantial air pollution
– Drilling - soil and water pollution
– Controversies – Arctic National Wildlife Refuge,
California coast
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Crude Oil Prices
Today
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Natural Gas Consumption
• Natural gas
produces only half
as much CO2 as an
equivalent amount
of coal.
• Problems:
– difficult to ship
across oceans or to
store in large
quantities
– Flaring off - wasted
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Nuclear Power
• “Atoms for Peace” in 1953 by Eisenhower (produce
enough power ‘to cheap to monitor’)
• Nuclear power now produces only about 7% of the
U.S. energy supply.
• Problems have made nuclear power much less
attractive than was originally expected :
– construction costs and
– safety concerns and….
– waste disposal.
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Nuclear Energy
Two types of nuclear power & both involve
rearranging the structure of the atom.
– Fission - splitting of a radioactive isotope of a heavy
element into daughter products (smaller atoms) with the
release of energy
– Fusion - joining of isotopes of a light element into a
heavier element with the release of energy.
• All commercial energy generation is run by fission.
• The Sun generates heat and light by fusion.
• Some nuclear weapons use fusion reactions but
controlled fusion is still in the developmental stage.
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Accidents????
Chernobyl - 1986
Three Mile Island
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- 1979
Nuclear Wastes
• One of the most difficult problems associated with
nuclear power is the disposal of wastes produced
during mining, fuel production, reactor operation,
and decommissioning of reactors.
• Ocean dumping – until 1970?
• Radioactive mine wastes, mill tailings
• Dry cask storage
• High-level waste repository - Yucca Mountain, NV
• Monitored, retrievable storage?
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1965+ - former Soviet
Union disposed of 18
nuclear reactors (7 w/ fuel
in the Kara Sea)
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• Hanford buried radioactive waste which
began leaking.
Plant roots absorbed the radioactive
material and transported it to the ground
surface.
• Nuclear testing peaks in 1950-60s. Trees
absorb cesium and accumulates in wood.
Wood ash can be radioactive – 100X higher
cesium than other environmental samples.
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ENERGY CONSERVATION
• Utilization Efficiencies
– Most potential energy in fuel is lost as
waste heat.
– In response to 1970’s oil prices,
average US automobile gas-mileage
increased from 13 mpg in 1975 to 28.8
mpg in 1988.
–Falling fuel prices of the 1980’s discouraged
further conservation.
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Find more
nonrenewable
oil?
Eg, Arctic
National
Wildlife
Refuge
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Hybrid
gaselectric
engines
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Energy Conversion Efficiencies
• Energy Efficiency is a measure of energy
produced compared to energy consumed.
– Household energy losses can be reduced by
one-half to three-fourths by using better
insulation, glass, protective covers, and
general sealing procedures.
(Indoor Pollution?)
• Orient homes to gain advantage of passive solar
gain in the winter.
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Mesa Verde NP (SW USA) – many energy efficient features
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Domestic Energy Efficiency
Earth-sheltered house in Taos, New Mexico
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Buying energy-efficient appliances can cut
your energy consumption considerably.
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Renewable Energies:
SOLAR ENERGY
• Average amount of solar energy arriving
on top of the atmosphere is 1,330 watts
per square meter.
– Amount reaching the earth’s surface is
10,000 times more than all commercial
energy used annually.
• Until recently, this energy source has been too
diffuse and low intensity to capitalize for
electricity.
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Solar Energy
• Passive Solar Heat - Using absorptive
structures with no moving parts to
gather and hold heat.
– Greenhouse Design
• Active Solar Heat - Generally pump
heat- absorbing medium through a
collector, rather than passively
collecting heat in a stationary object.
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Underground massive
heat storage unit
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Parabolic mirrors
High-Temperature Solar Energy
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Fresh and salt water
ponds to trap solar
radiation/heat
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Average
Daily
Solar
Radiation
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Photovoltaic Cells
• During the past 25 years, efficiency of
energy capture by photovoltaic cells
has increased from less than 1% of
incident light to more than 10% in field
conditions, and 75% in laboratory
conditions.
– Invention of amorphous silicon collectors
has allowed production of lightweight,
cheaper cells.
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Costs for
alternative
and
renewable
energy
sources
have
dropped in
recent
years.
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Storing Electrical Energy
• Electrical energy storage is difficult
and expensive.
– Lead-acid batteries are heavy and have
low energy density.
• Typical lead-acid battery sufficient to store
electricity for an average home would cost
$5,000 and weigh 3-4 tons.
– Pumped-Hydro Storage
– Flywheels
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Promoting Renewable Energy
• Distributional Surcharges
– Small charge levied on all utility customers to help
finance research and development.
• Renewable Portfolio
– Mandate minimum percentage of energy from
renewable sources.
• Green Pricing
– Allow utilities to profit from conservation programs and
charge premium prices for energy from renewable
sources.
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Fuel Cells
• Fuel cells - use
ongoing
electrochemical
reactions to produce
an electrical current
• Oxygen, hydrogen
• Reformers
• Efficiency- 70%
theoretically but
practically around
40-45%?
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Fuel Cell
Electric
Car
Typical fuel
cell efficiency
is 40-45%.
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Hydrogen fueling stations
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BIOMASS
• Wood provides less than 1% of US
energy, but provides up to 90% in poorer
countries.
– 1,500 million cubic meters of fuelwood
collected in the world annually.
• Inefficient burning of wood produces smoke
laden with fine ash and soot and hazardous
amounts of carbon monoxide (CO) and
hydrocarbons.
– Produces few sulfur gases, and burns at lower
temperature than coal.
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Fuel wood Crisis in LessDeveloped Countries
• About 40% of the
world’s population
depends on firewood and
charcoal as their primary
energy source.
• Supplies diminishing
• Half of all wood
harvested worldwide is
used as fuel.
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Using Dung as Fuel
• Using dung as fuel
deprives fields of
nutrients and
reduces crop
production.
• When cow dung is
burned in open fires,
90% of the potential
heat and most of the
nutrients are lost.
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Swedish workers harvesting marsh reeds for biomass energy
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Using Methane as Fuel
Anaerobic Fermentation
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Alcohol from Biomass
• Ethanol - grain alcohol
• Methanol - wood alcohol
• Gasohol - a mixture of gasoline and
alcohol - reduced CO emissions
• Ethanol production could be a solution
to grain surpluses.
• Both methanol and ethanol make good
fuel for fuel cells.
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Forest thinnings to methanol to fuel cells for
electricity
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Energy from the Earth’s Forces
Hydropower
• Water power
produces 25% of the
world’s electricity.
•?Clean, renewable
energy
• Dams - social and
ecological damage
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Dam Drawbacks
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Human Displacement
Ecosystem Destruction
Wildlife Losses
Large-Scale Flooding Due to Dam
Failures
Sedimentation
Herbicide Contamination
Evaporative Losses
Nutrient Flow Retardation
CO2 emissions
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Wind Energy
• Wind power - advantages and disadvantages
• Wind farms - potential: Great Plains, seacoasts
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Wind Energy
• Wind Farms - Large concentrations of
wind generators producing commercial
electricity.
– Negative Impacts:
• Interrupt view in remote places
• Destroy sense of isolation
• Potential bird kills
• Cannot place w/i 70 km of military airbases, etc
• Sources vary geographically
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Geothermal Energy
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• Have long life
span,
• no mining
needs, and
• little waste
disposal.
• Potential danger
of noxious gases
and
• noise problems
from steam valves.
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Tidal
Energy
• Requires a high
tide/low-tide
differential of
several meters
• Saltwater
flooding behind
the dam and
heavy siltation
• Locations w/
large waves?
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Wave Power!!
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Ocean Thermal Electric Conversion (OTEC) Plant
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An
Alternative
Energy
Future?
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Green Buildings to conserve energy
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Summary:
•
•
•
•
•
Energy Sources and Uses
Coal - Oil - Natural Gas
Nuclear Power
Conservation
Solar Energy
– Photovoltaic Cells
• Fuel Cells
• Energy From Biomass
• Energy From Earth’s Forces
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