Unit 6 study

• Potentially renewable vs. nondepletable:

  • Potentially renewable could run out if not managed properly
  • Nondepletable will never run out (e.g. sunlight)
• % of world energy use from fossil fuels: 80%
• Countries that use the most energy: China and the U.S.
• Most used energy source in the U.S.: oil
• Hubber curve: A bell-shaped curve representing oil use
• Least expensive and most environmentally sound options for maximizing energy resources:

  • Energy conservation
  • Energy efficiency
• EROEI concept:

  • Describes the amount of energy obtained from an energy source for every unit of energy expended on its production
  • Higher number indicates more net energy gained
• Important biofuels in the U.S.: Ethanol and biodiesel
• Types of coal from cleanest to dirtiest:

  • Lignite
  • Bituminous
  • Anthracite
• Main gas in natural gas: methane
• Products from oil and refining process:

  • Tar
  • Asphalt
  • Gasoline
  • Diesel
  • Kerosene
  • Obtained by heating crude oil to separate compounds at different temperatures
• Tar sands:

  • Slow flowing deposits of bitumen or asphalt
  • Mining is more energy-intensive than conventional oil drilling
  • Contaminates water and releases more carbon dioxide
• Importance of energy-efficient transportation and fuel choice:

  • Transportation accounts for 35% of energy use in the U.S.
• Vehicles under "light trucks" category:

  • Pickup trucks
  • SUVs
  • Crossover vehicles
  • 75% of vehicles sold in the U.S.
• Cogeneration: Using fuel to generate electricity and provide heat to a building or industrial process
• % of electricity generated from non-renewable resources in 2020: 79%
• Fracking: Hydraulic fracturing using high-pressure fluids to extract natural gas
• Negative consequences of fracking:

  • Large water usage
  • Groundwater contamination
  • Potential earthquakes
  • Release of VOCs and methane
• Grid: Network of interconnected transmission lines connecting electricity generation sources to end users
• Efficiency of burning coal for lighting:

  • 65% of coal burned is lost as heat
  • 10% of electricity lost in transmission
  • 95% of electricity wasted as heat from the light bulb
  • Results in 1.6% efficiency
• Fuel rods: Cylindrical tubes containing nuclear fuel for steam production
• Electricity generation from uranium: Uranium 235 fission chain reaction produces heat to make steam for turbines
• Control rods: Cylindrical devices in a nuclear reactor to absorb excess neutrons and control fission rate
• Half-life: Time for half of radioactive parent atoms to decay
• Storage of spent fuel rods and nuclear waste: At the plant itself
• Nuclear accidents: Three Mile Island, Chernobyl, Fukushima
• Organic materials for ethanol production: Corn, sugarcane, wood chips, crop waste, switchgrass
• 90% of U.S. ethanol from: corn
• Sources of biodiesel: Algae, soybeans, palm
• Common use of ethanol in the U.S.: Mixed into gasoline at around 10%
• Negative effects of mixing ethanol with gasoline:

  • Reduced efficiency
  • High fossil fuel and land usage
  • Potential food shortages
• Benefits of growing algae for biodiesel:

  • Produces more fuel per area
  • Can be grown in non-traditional agricultural spaces
• Passive solar energy: Using the sun's energy for heating buildings
• Maximizing passive solar energy in Northern Hemisphere: Positioning windows facing south
• Photovoltaic cells: Convert solar energy into electricity
• Methods of generating electricity from water power:

  • Water impoundment
  • Run of the river systems
  • Tidal
• Advantages and disadvantages of biomass, solar energies, and hydroelectric power
• Geothermal energy and its working principle: Using heat from magma to produce steam for turbines
• Geothermal energy for people far from magma: Ground source heat pumps for heating and cooling
• Fuel cell: Converts fuel like hydrogen into electrical current