PP

Chapter 15: Nonrenewable Energy

What is Net Energy and Why Is It Important?

The Laws That Govern Energy

  • The first law of thermodynamics: It takes high-quality energy to get high-quality points. Pumping oil from the ground, refining it, transporting it.
  • The second law of thermodynamics: Some high-quality energy is wasted at every step

Basic Science: Net Energy Is the Only Energy That Really Counts

  • Net Energy: Total amount of useful energy available from a resource minus the energy needed to make the energy available to consumers
    • Business net profit: Total money taken in minus all expenses
  • New energy ratio: ratio of energy produced to energy used to produce it
  • Conventional oil
    • high net energy ratio

Energy Resources With Low/Negative Net Energy Yields need Marketplace Help

  • Cannot compete in open markets with alternatives that have higher net energy yields
  • Need subsidies from taxpayers
    • Ex. Nuclear power

Reducing Energy Waste Improves Net Energy Yields and Can Save Money

  • 84% of all commercial energy used in the U.S. is wasted
    • 43% after accounting for the second law of thermodynamics
  • Make buildings energy efficient, drive efficient cars, not gas guzzlers

What Are the Advantages and Disadvantages of Oil?

How Does Oil and Natural Gas Form?

  • Fracking: High-pressure pumps shoot a mixture of water, sand, and chemicals into the well; the pressure builds up and creates cracks so that the oil/natural gas can flow up to the surface

  • Ocean

    • Tiny sea plants and animals died and were buried on the ocean floor. Over time, they were covered by layers of slit and sand
    • Over millions of years, the remains were buried deeper and deeper. The enormous heat and pressure turned them into oil and gas.
    • Today, we drill down through layers of sand, silt, and rock to reach the rock formations that contain oil and gas deposits

Oil Dependence

  • Petroleum, or crude oil
    • conventional, or light oil
  • 1/3 of the commercial world’s energy
  • 40% of that used in the USA
  • Peak production: the time after which production from a good declines
    • Global peak production for all world oil

Refining Crude Oil

  • Refining: Heating crude oil to separate it into various fuels and other components with different boiling points in a complex process
  • Photochemical: Products of oil distillation, raw materials for industrial organic chemicals
    • Pesticides
    • Paints
    • Plastics
  • Petrochemicals: the 2% of the products of refining; used for raw materials to make industrial organic chemicals, cleaning fluids, pesticides, plastics, synthetic fibers, paints, medicines, cosmetics, ice cream, and many other productT

Oil Reserves

  • Proven oil reserves: Identified deposits that can be extracted profitably with current technology
  • Unproven reserves
    • Probable reserves: 50% chance of recovery
    • Possible reserves: 10-40% chance of recovery

Conventional Oil

  • Advantages
    • Ample supply for several decades
    • High net energy yield but decreasing
    • Low land disruption
    • Efficient distribution system
  • Disadvantages
    • Water pollution from oil spills and leaks
    • Environmental costs not included in market price
    • Releases CO2 and other air pollutants when burned
    • Vulnerable to international supply interruptions

Heavy Oils from Oil Shale and Tar Sand

  • Advantages
    • Large potential supplies
    • Easily transported within and between countries
    • The efficient distribution system in place
  • Disadvantages
    • Low net energy yield
    • Releases CO2 and other air pollutants when produced and burned
    • Severe land disruption and high water use

What Are the Advantages and Disadvantages of Using Natural Gas?

Natural Gas Is a Useful and Clean-Burning Fossil Fuel

  • Natural gas
    • a mixture of gases
    • 50-90% is methane -- CH4
  • Conventional natural gas
    • Pipelines
    • Liquefied petroleum gas (LPG): When propane and butane gases are liquefied under high pressure
    • Liquefied natural gas (LNG): Low net energy yield and makes the U.S. dependent upon unstable countries like Russia and Iran

Is Unconventional Natural Gas the Answer?

  • Coal bed methane gas
    • In coal beds near the earth’s surface
    • In shale beds
    • High environmental impacts or extraction
  • Methane hydrate
    • Trapped in icy water
    • In permafrost environments
    • On ocean floor
    • Costs of extraction are currently too high

Conventional Natural Gas

  • Advantages
    • Ample supplies
    • High net energy yield
    • Emits less CO2 and other pollutants than other fossil fuels
  • Disadvantages
    • Low net energy yield for LNG
    • Releases CO2 and other air pollutants when burned
    • Difficult and costly to transport from one country to another

What Are the Advantages and Disadvantages of Coal?

Coal Is a Plentiful but Dirty Fuel

  • Coal: solid fossil fuel

  • Burned-in power plants; generates 42% of the world’s electricity

    • Inefficient

  • Three largest coal-burning countries: China, the United States, and Canada

  • World’s most abundant fossil fuel

    • The U.S. has 28% of proven reserves

  • Environmental costs of burning coal

    • Severe air pollution
    • Sulfur released as SO2
    • A large amount of soot
    • CO2
    • Trace amounts of Hg and radioactive materials

    Stages in Coal Formation over Millions of Years

Coal

  • Advantages
    • Ample supplies in many countries
    • High net energy yield
    • Low cost when environmental costs are not included
  • Disadvantages
    • Severe land disturbance and water pollution
    • Fine particles and toxic mercury emissions threaten human health
    • Emits large amounts of CO2 and other air pollutants when produced and burned

We Can Convert Coal into Gaseous and Liquid Fuels

  • Conversion of solid coal to
    • Synthetic natural gas (SNG) by coal gasification
    • Methanol or synthetic gasoline by coal liquefaction
    • Synfuels

Synthetic Fuels

  • Advantages
    • Large potential supply in many countries
    • Vehicle fuel
    • Lower air pollution than coal
  • Disadvantages
    • Low to moderate net energy yield
    • Requires mining 50% more coal with increased land disturbance, water pollution, and water use
    • Higher CO2 emissions than coal

What Are the Advantages and Disadvantages of Nuclear Energy?

How Does a Nuclear Fission Reactor Work?

  • Controlled nuclear fission reaction in a reactor
    • Light-water reactors
    • Very inefficient
  • Fueled by uranium ore and packed as pellets in fuel rods and fuel assemblies
  • Control rods absorb neutrons
  • Water is the usual coolant
  • Containment shell around the core for protection
  • Water-filled pools or dry casks for storage of radioactive spent fuel rod assemblies

What Is the Nuclear Fuel Cycle?

  1. Mine the uranium
  2. Process the uranium to make the fuel
  3. Use it in the reactor
  4. Safely store the radioactive waste
  5. Decommission the reactor

Conventional Nuclear Fuel Cycle

  • Advantages
    • Low environmental impact (without accidents)
    • It emits 1/6 as much CO2 as coal
    • Low risk of accidents in modern plants
  • Disadvantages
    • Very low net energy yield and high overall cost
    • Produces long-lived, harmful radioactive wastes
    • Promotes the spread of nuclear weapons

Coal vs. Nuclear

  • Coal
    • High net energy yield
    • Very high emissions of CO2 and other air pollutants
    • High land disruption from surface mining
    • Low cost when environmental costs are not included
  • Nuclear
    • Very low net energy yield
    • Low emissions of CO2 and other air pollutants
    • Much lower land disruption from surface mining
    • The high cost (even with huge subsidies)

Dealing with Radioactive Wastes Produced by Nuclear Power Is a Difficult Problem

  • High-level radioactive wastes
    • Must be stored safely for 10,000–240,000 years
  • Where to store it
    • Deep burial→safest and cheapest option
    • Would any method of burial last long enough?
    • There is still no facility
    • Shooting it into space is too dangerous

Can Nuclear Power Lessen Dependence on Imported Oil & Reduce Global Warming?

  • Nuclear power plants: no CO2 emission
  • Nuclear fuel cycle: emits CO2
  • Opposing views on nuclear power
    • Nuclear power advocates
    • 2007: Oxford Research Group
  • Need a high rate of building new plants, plus a storage facility for radioactive wastes

Are New Generation Nuclear Reactors the Answer?

  • Advanced light water reactors (ALWR): Built-in passive safety features
  • Thorium-based reactors: Cheaper and safer but research and development are needed

Solutions: New Generation Nuclear Reactors

  • Reactors must be built so that a runaway chain reaction is impossible
  • The reactor fuel and methods of fuel enrichment and fuel reprocessing must be such that they cannot be used to make nuclear weapons
  • Spent fuel and dismantled structures must be easy to dispose of without burdening future generations with harmful radioactive waste
  • Taking its entire fuel cycle into account it must generate a net energy yield high enough so that it does not need government subsidies, tax breaks, or loan guarantees to compete in the open marketplace
  • Its entire fuel cycle must generate fewer greenhouse gas emissions than other energy alternatives

Will Nuclear Fusion Save Us?

  • Nuclear fusion: Fuse lighter elements into heavier elements, No risk of meltdown or large radioactivity release

    Nuclear fission diagram