Lecture 4 Energy Sources

Energy Sources

Core Case Study: Conventional Oil Supplies

• Oil is a major energy supplier.
• Key questions:
  • How much oil is left?
  • When will we run out of oil?
• Three options for addressing oil depletion:
  • Look for more oil.
  • Reduce oil use.
  • Use other energy sources.

Predictions of Oil Depletion

• Past predictions of the world running out of oil:
  • 1914: U.S. Bureau of Mines predicted depletion in 10 years.
  • 1939 & 1950: U.S. Department of the Interior predicted depletion in 13 years.
  • 1973: Paul Erlich, Limits to Growth, predicted depletion of oil and other fossil fuels by 1990.
  • 2002: Paul Erlich, Beyond the Limit, predicted depletion of oil by 2030 and other fossil fuels by 2050.
• International Energy Outlook (2021) forecasts oil supply meeting global demand until at least 2050.

Major Sources of Energy

• Non-Renewable Energy (82%)
  • Fossil Fuels
    • Oil: 33%
    • Coal: 22%
    • Natural Gas: 21%
  • Nuclear Power: 6%
• Renewable Energy (18%)
  • Biomass: 11%
  • Hydropower: 4.5%
  • Geothermal, Solar, Wind: 2.5%
• Fossil fuels supply three-quarters of the world's commercial energy.
• Non-renewable nuclear fuel and renewable sources make up one-quarter.
• Renewable sources include direct solar energy and indirect solar energy (wind, hydropower, biomass).
• Net Energy:
  • Amount of high-quality usable energy available from a resource after subtracting the energy needed to make it available.

Conventional vs. Non-Conventional Energy Sources

• Non-Conventional Energy Sources:
  • Under development in recent years.
  • Examples: Solar, Wind, Tidal, Biogas, Biomass, Geothermal.
• Conventional Energy Sources:
  • In use for a long time.
  • Examples: Coal, Petroleum, Natural Gas, Nuclear, Hydropower.

Conventional vs. Non-Conventional Energy: Comparative Analysis

Important Nonrenewable Energy Resources

• Removed from the earth’s crust:
  • Coal
  • Oil
  • Natural gas
  • Some forms of geothermal energy
  • Nonrenewable uranium ore

Global Energy Systems Transition

• Historical shifts in market share:
  • 1850: Wood dominates
  • 1900: Coal gains prominence
  • 1950: Oil increases
  • 2000: Natural gas rises
• Future projections:
  • 2050/2100/2150: Potential for hydrogen to become a significant energy source.

Advantages and Disadvantages of Oil

• Conventional Oil:
  • Advantages:
    • Currently abundant
    • High net energy yield
    • Relatively inexpensive
  • Disadvantages:
    • Air and water pollution
    • Greenhouse gas emissions
• Heavy Oils (Oil Sand and Oil Shale):
  • Advantages:
    • Potentially large supplies
  • Disadvantages:
    • Low net energy yields
    • Higher environmental impacts than conventional oil

Dependence on Oil

• Crude oil and natural gas are found deep within the earth’s crust on land or under the seafloor.
• Dispersed in pores and cracks in underground rock formations
• Oil Extraction and Refining
  • Wells are drilled vertically or horizontally into the deposit.
  • Oil is drawn by gravity (pressure difference) out of the rock pores.
  • Flows into the bottom of the well and is pumped.
  • It takes energy and money to find, drill and pump.
• Petrochemicals
  • Products of oil distillation
  • Raw materials

Oil Extraction and Recovery

• Primary Recovery:
  • Underground pressure in the oil reservoir forces oil and gas to the surface.
• Secondary Recovery:
  • Pressure falls over the lifetime of a well.
  • External energy is supplied by injecting fluids (water and gas) to increase reservoir pressure.
• Enhanced Recovery:
  • Steam is injected to increase the mobility of thicker, heavier crude oil.

Types of Oil

• Light Oil:
  • Petroleum or crude oil.
  • Conventional oil
  • 30% of the world’s estimated supply.
• Heavy Oil:
  • Unconventional heavy oil
  • Thick.
  • 70% of the world’s estimated supply oil.
  • Some remains in wells.
  • Extracted from tar sands and oil shale rock.
  • Extraction requires considerable energy and money, reducing net energy yield.

Refining Crude Oil

• Fractional Distillation:
  • Oil refineries separate crude oil into different, more useful hydrocarbon products.
  • Separation is based on differences in molecular weight.
  • Different molecular weights correspond to different boiling points.
  • Lighter components boil at lower temperatures.
  • Heavier compounds are separated later in the process.

Trade-Offs: Conventional Oil

Heavy Oil from Sand

• Oil sand/tar sand: Mixture of sand, clay, water, and bitumen
• Bitumen: Thick, sticky, tar-like heavy oil with high sulfur content.
• Extraction process has serious environmental impacts: air, water, wildlife, and climate.
• Low net energy yield: Is it cost-effective?
• Oil sand is mixed with hot water and steam to extract the bitumen.

Oil Shales

• Oily rocks containing kerogen.
• Requires heating to increase flow rate.
• Processed to remove sulfur, nitrogen, and other impurities.
• Low net energy yield.

Trade-Offs: Heavy Oils from Oil Shale and Tar Sand

Natural Gas

• Conventional Natural Gas
  • More plentiful than oil.
  • High net energy yield.
  • Fairly low cost.
  • Lowest environmental impact of all fossil fuels.
• Natural gas: Mixture of gases
  • More than half is $CH_4$ (50-90%).
• Liquefied Petroleum Gas (LPG)
  • Propane and butane gases are liquefied under high pressure
• Liquefied Natural Gas (LNG)
  • Low net energy yield
  • Natural gas cooled to liquid form for ease and safety of non-pressurized storage or transport.
  • Approximately $-162^\circ C$
  • Transported via refrigerated tanker ships
  • CH4 (methane - greenhouse gas)

Natural Gas Advantages

• Will natural gas be the bridge fuel helping us make the transition to a more sustainable energy future?

Trade-Offs: Conventional Natural Gas

Advantages and Disadvantages of Coal

• Conventional Coal
  • Very plentiful
  • High net energy yield
  • Low cost
  • Very high environmental impact
    • Severely degrades land and pollutes water and air
    • When burned, severely pollutes the air

Stages in Coal Formation

• Process over millions of years with increasing heat and pressure:

  • Peat (not a coal) to Lignite (brown coal) to Bituminous (soft coal) to Anthracite (hard coal)

• Characteristics:

  • Peat: Partially decayed plant matter in swamps and bogs; low heat content.
  • Lignite: Low heat content; low sulfur content; limited supplies.
  • Bituminous: Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content.
  • Anthracite: Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited.

Coal-Burning Power Plant

• Coal-fired plants produce electricity by burning coal in a boiler to produce steam.
• The steam, under tremendous pressure, flows into a turbine, which spins a generator to create electricity.
• The steam is then cooled, condensed back into water, and returned to the boiler to start the process over.

Environmental Impacts of Coal Mining

• Surface mining of coal:
  • Eliminates existing vegetation.
  • Destroys the genetic soil profile.
  • Displaces or destroys wildlife and habitat.
  • Degrades air quality.
  • Alters current land uses.
  • Creates scarred landscape with no scenic value.
  • Movement, storage, and redistribution of soil during mining disrupts the community of soil microorganisms.

Coal as a Dirty Fuel

• World’s most abundant fossil fuel.
• Environmental costs of burning coal:
  • Severe air pollution.
  • Sulfur released as $SO_2$.
  • Large amount of soot (black powdery substance consisting largely of amorphous carbon).
  • $CO_2$.
  • Trace amounts of mercury (Hg) and radioactive materials.

Trade-Offs: Coal

Top 3 Countries

• Coal:
  • China/USA
  • USA/Russia
  • India/Australia
• Natural Gas:
  • Russia/USA
  • Iran/Russia
  • Qatar/Iran
• Light Oil:
  • KSA/USA
  • Kuwait/KSA
  • USA/Russia
• Tar Sands:
  • Canada
  • Venezuela/Kazakhstan
  • USA/Russia
• Oil Shale:
  • KSA/US
  • US/Russia/Estonia
  • Russia/China/Brazil

Nuclear Energy

• Limited use due to:
  • Low environmental impact (under normal operations).
  • Very low accident risk.
  • High costs.
  • Low net energy yield.
  • Long-lived radioactive wastes.
  • Vulnerability to sabotage.
  • Potential for spreading nuclear weapons technology.

Nuclear Fission Reactor

• Controlled nuclear fission reaction in a reactor.
• Fueled by uranium ore, packed as pellets in fuel rods and fuel assemblies.
• 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.

Nuclear Waste

• After 3-4 years in a reactor, spent fuel rods are removed and stored in water.
• Radioactivity diminishes with time.
  • Waste must be isolated for sufficient time to reduce radioactivity below acceptable limits.
  • Days to years.
• Spent fuel rods from nuclear power plants:
  • 5 years of cooling (up to 10 years in some cases).
  • Wastes must be stored safely for thousands of years.
• A major environmental concern related to nuclear power is the creation of radioactive wastes such as spent (used) reactor fuel. These materials can remain radioactive and dangerous to human health for thousands of years.

Nuclear Waste Storage

• Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel after the spent rods have cooled.

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.

Nuclear Power Trends

• Slowest-growing energy source.
• Expected to decline more.
• Why?
  • Economics
  • Poor management
  • Low net yield of energy of the nuclear fuel cycle
  • Safety concerns
  • Need for greater government subsidies
  • Concerns of transporting uranium

Case Studies: Nuclear Power Plant Accidents

• Three Mile Island (USA, 1979):
  • Nuclear reactor lost its coolant.
  • Led to a partial uncovering and melting of the radioactive core.
  • Unknown amounts of radioactivity escaped.
  • People fled the area.
  • Increased public concerns for safety.
  • Led to improved safety regulations in the U.S.
• Chernobyl (Ukraine, 1986):
  • Series of explosions caused the roof of a reactor building to blow off.
  • Partial meltdown and fire for 10 days.
  • Huge radioactive cloud spread over many countries and eventually the world.
  • 350,000 people left their homes.
  • Effects on human health, water supply, and agriculture.

Trade-Offs: Conventional Nuclear Fuel Cycle

Trade-Offs: Coal vs. Nuclear

Dealing with Radioactive Wastes

• Difficult Problem.
• High-level radioactive wastes:
  • Must be stored safely for 10,000–240,000 years.
    • Deep burial: safest and cheapest option.
    • Would any method of burial last long enough?
  • There is still no facility.

Nuclear Fusion

• Power of the future?
• Still in the laboratory phase.
• After 50 years of research and 34 billion dollars.
• 2006: U.S., China, Russia, Japan, South Korea, and European Union.
• Will build a large-scale experimental nuclear fusion reactor by 2040.

Top 3 Countries

• Nuclear Energy
  • US
  • China - France
  • Russia
• International distance approximately 26 km

Renewable Energy

• Energy produced from sources that
  • do not deplete
  • or can be replenished within a human’s lifetime
• Most common examples
  • Wind
  • Solar
  • Geothermal
  • Biomass
  • Hydropower

Efficiency as an Energy Resource

• Comparison Chart of Bulbs
  • Incandescent
    • 60 watts
    • 1,500hrs
    • $1 Bulb Cost
    • $393 25 year cost
  • CFL
    • 15 watts
    • 8,000hrs
    • $5 Bulb Cost
    • $125 25 year cost
  • LED
    • 7 watts
    • 50,000hrs
    • $8 Bulb Cost
    • $42 25 year cost

Reducing Energy Waste

• Advantages of reducing energy waste:
  • Quick and clean.
  • Cheapest way to provide more energy.
  • Reduce pollution and degradation.
  • Slow global warming.
  • Increase economic and national security.

More Energy-Efficient Vehicles

• Superefficient and ultralight cars
• Gasoline-electric hybrid car
• Plug-in hybrid electric vehicle
• Energy-efficient diesel car
• Electric vehicle with a fuel cell (Hydrogen Power)

Saving Energy and Money in Existing Buildings

• Insulate and plug leaks:
  • One-third of heated air in typical homes escapes through air leaks and poor sealing.
• Use energy-efficient windows:
  • Highly efficient super-windows have the insulating effect of a window with 3 to 20 panes.
  • Cut expensive heat losses.
• Stop other heating and cooling losses:
  • Leaky heating and cooling ducts
  • White or light-colored roofing or living roofs
• Heat houses more efficiently:
  • superinsulation
• Heat water more efficiently
• Solar heaters
• Use energy-efficient appliances
• Refrigerators
• Electric stoves
• Use energy-efficient lighting

Renewable Energy

• Using Renewable Energy in Place of Nonrenewable Energy Sources
  • Solar energy
  • Geothermal energy
• Benefits of shifting toward a variety of locally available renewable energy resources

Solar Energy

• "Solar" is the Latin word for sun, and solar power is the energy from the sun.
• Solar energy technology comprises of two different categories, thermal conversion and photo-conversion.
  • Photovoltaic: Sunlight directly converts into electrical energy.
  • Thermal Energy: Sunlight focuses to thermal receptors and converts water to steam, then turbines rotary power produces electricity.

Solar Techniques

• Solar water heating
• Solar air conditioning
• Solar drying
• Solar green-house
• Solar desalination
• Solar refrigeration
• Solar cooking
• Solar furnace
• Solar electricity (Photovoltaic)
• Solar electricity (Thermal)

Advantages of Solar Energy

• Solar energy is free
• Solar energy does not cause pollution
• It can be used in remote areas where it is too expensive to extend electricity power grid.
• Calculators and other low power consuming devices can be powered by solar energy effectively.

Solar Energy - Heat and Light

• Traps heat
  • Hot Water
  • Plumber
• Uses light
  • Electricity
  • Electrician

Advantages and Disadvantages of Solar Energy?

• Passive and active solar heating systems effectively heat water and buildings.
• Costs of using direct sunlight to produce high-temperature heat and electricity are coming down.
• Solar thermal systems
  • Central receiver systems for widespread use.
  • High cost.
  • Low net energy yields.
  • Limited suitable sites.
  • Sunny, desert sites.

Trade-Offs: Solar Energy for High-Temperature Heat and Electricity