Energy

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Energy
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Definitions

• Work application of force through a distance,
  measured in newtons (kg/m/s)
• Energy capacity to do work measured in joules
  (newtons/meter)
• Power rate of flow of energy, measured in watts
  (joules/s)

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Current energy sources

• Fossil fuels account for 70 of all energy use
  globally (see piechart)
• Average p/c energy use in the US is more than 300
  GJ/year (60 barrels of oil) less than 1 GJ in
  poor countries
• Japan, W European countries have standards of
  living comparable or higher than the US, but use
  much lower amounts of energy

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Energy use

• 36.5 of US energy use consumed by industry
  (mining, chemical, plastics, construction
  materials, foods, etc.)
• Remainder utilized by residential and commercial
  buildings and transportation (see figure)

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Efficiency and waste

• Natural gas is most efficient fuel (10 lost in
  shipping and processing) and combustion
  generates least amount of CO2
• 2/3 of energy in coal lost in conversion to
  electricity and enormous amounts of air
  pollution are generated
• 75 of energy in crude oil lost during refining,
  transportation, storage, marketing, and combustion

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Fossil fuels

• Fossilized remains of living organisms, buried in
  sediments millions of years ago
• Concentrated and transformed by high pressures
  and temperatures into coal, oil, and gas
• Since they take so long to form, considered
  non-renewable resources

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Coal

• Ten times more extensive all other fossil fuels
  combined
• Can be 100 m thick, extend across tens of
  thousands of square kilometers that were once
  vast swampy forests
• Enormous reserves in N America, Europe, and Asia
  very little in Africa and Latin America
• Surface (strip) mining is safest for workers, but
  ecologically devastating
• Coal accounts 83 of electric power production in
  the US
• Coal burning releases half of the industrial CO2
  in the US each year and large amounts of other
  pollutants

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Oil

• 2/3 of all known oil reserves in Middle East
• Oil is used primarily for transportation and
  heating
• Oil drilling is less hazardous to environment
  than coal mining, but source of significant ocean
  pollution
• Around 3-6 million metric tons of oil are
  discharged into worlds oceans each year about
  half from tankers and half from deliberate
  dumping of used motor oil

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Tar sands

• Mixture of sand and bitumen (tar) excavated and
  extracted using steam
• Largest deposits in Canada and Venezuela
• Deep deposits can be heated and pumped out using
  superheated steam
• Excavation and refining of tar sands produces
  enormous amounts of toxic sludge, greenhouse
  gases, and contaminated surface water as well as
  extensive forest destruction

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Oil shales

• Oil shales are sedimentary rock mixed with
  kerogen (a solid hydrocarbon)
• Abundant deposits in Colorado, Utah, and Wyoming
• Like tar sands, oil shales can be heated,
  liquefied, and pumped out
• Also generates extensive waste products
• Abandoned after oil prices dropped

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Natural gas

• 23 of global energy production
• Produces half as much CO2 as coal
• Abundant supplies in Middle East, former Soviet
  Union
• Difficult to ship and store expensive
  infrastructure necessary to deliver it to markets

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Nuclear Power

• Uranium235 is bombarded by neutrons causing
  nuclear fission and release of energy
• Failure of coolant pumps can result in meltdown
  and release of deadly radioactive material
• Production of uranium fuel and spent fuel rods
  generates enormous amounts of radioactive wastes
• Monitored, retrievable storage is believed to be
  the best solution to radioactive wastes

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Energy conservation

• Gas mileage (13 mpg in 1975) has doubled in
  response to federal regulations and rising oil
  prices
• Additional improvements may yield even better
  mileages (up to 72 mpg)
• Household energy losses can be reduced by better
  insulation, energy efficient appliances, passive
  solar heating, and other measures (see table p.
  285)

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Solar energy

• Passive heat absorption (thick walls of
  stone/adobe) is simplest and oldest use of solar
  energy
• Active solar systems pump a heat absorbing fluid
  medium through a small collector heat can be
  stored in rocks or water
• Parabolic mirrors can be used to concentrate
  solar energy to generate high temperatures
• Photovoltaic cells use thin silicon sheets to
  convert solar energy directly into electrical
  current

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Energy storage methods

• Alternative energy sources must be able to store
  large amounts of energy produced during peak
  periods for off-peak use
• Traditional lead-acid batteries have limited
  energy storage ability and are toxic to
  manufacturing workers
• One solution is to use energy to pump water to an
  elevated reservoir downhill movement converted
  to electricity as needed by turbine generators

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Fuel cells

• Use hydrogen (which can easily be stripped of an
  electron) to generate electrical charge
• Storage of hydrogen is difficult and dangerous
• Alternatively, hydrogen can be stripped from
  fuels or biomass
• Can potentially have quiet, clean operation with
  minimal waste products (water)
• Could possibly be an important fuel source for
  vehicles and electronic appliances

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Biomass

• Primary source of heating and cooking for
  thousands of years
• 95 of energy use in many poorer countries
• Use complicated by inefficient burning, and smoke
  and carcinogen emissions
• Firewood collection has led to extensive
  deforestation in some areas

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Dung and methane

• Animal manure can be used as a fuel, but most the
  the potential heat and nutrients are wasted using
  open air burning
• Manure can be converted more efficiently into
  methane gas (a highly efficient fuel) residual
  sludge can be used as fertilizer

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Alcohol

• Plants can be converted to alcohol in form of
  ethanol (grain alcohol) or methanol (wood
  alcohol)
• Can be used as an automobile fuel directly or in
  combination with gasoline (gasohol)
• Methanol (wood alcohol) burns at a lower
  temperature than gasoline or diesel eliminating
  the necessity of a radiator for cars

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Hydropower

• Energy source since ancient times, ¼ of all
  energy generation today
• 99 of electricity production in Norway
• Much of hydropower energy produced in enormous
  dams, but has significant social and
  environmental impact displacement, reduced
  sediment, disease

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Wind energy

• Expensive storage during peak production times to
  offset nonwindy periods
• More blades best in low winds, but more
  vulnerable to breakage during storms
• Too far from residential areas to cause much
  noise or sight impact

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Other energy sources

• Geothermal sources can produce steam or hot
  water limited to areas with volcanic activity
• Pumping through deeply buried pipes can extract
  enough heat even in the absence of active vents
• Tides can also be used for energy, but
  complicated by variable tidal periods, saltwater
  inundation of aquifers, destruction of habitat
  for aquatic species and migrating shorebirds, and
  heavy siltation
• Experiments are also underway to utilize wave
  energy

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