Comprehensive Notes on 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:
  • Look for more oil.
  • Reduce oil use.
  • Use other energy sources.

Predictions vs. Reality

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

Major Sources of Energy

• Non-Renewable Energy (82%):
  • Fossil Fuel Oil: 33%
  • Coal: 22%
  • Natural Gas: 21%
  • Nuclear Power: 6%
• Renewable Energy (18%):
  • Biomass: 11%
  • Hydropower: 4.5%
  • Geothermal, Solar, Wind: 2.5%

Definitions:

• Fossil Fuels: Supply most of our commercial energy (three-quarters).
• Renewable Sources: One-quarter of our commercial energy (includes direct and indirect solar energy).
• Net Energy: Amount of high-quality usable energy from a resource after subtracting the energy needed to make it available.

Conventional vs. Non-Conventional Energy Sources

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

Conventional vs. Non-Conventional Sources of Energy

| | Conventional Sources | Non-Conventional Sources |
| :-------------------------- | :------------------------------------------------ | :-------------------------------- |----------|
| Sources | Coal, Petroleum, Natural Gas, Water Power | Solar, Wind, Tidal, Biogas, Biomass, Geothermal |
| Exhaustibility | Exhaustible except water | NOT exhaustible |
| Pollution | Environment pollution (smoke, ash, chemicals…) | Pollution free |
| Power Transmission | Expensive | Local power generation and use |
| Waste Disposal | Problems | Environment friendly waste |
| Planet Heat | Imbalance | Balanced Heat |
| Energy Source | Non-Renewable | Renewable Energy |

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 energy source usage:
  • Wood -> Coal -> Oil -> Natural Gas
• Potential future:
  • Hydrogen

Advantages and Disadvantages of Oil

Conventional Oil

• Advantages:
  • Currently abundant
  • High net energy yield
  • Relatively inexpensive
• Disadvantages:
  • Air and water pollution
  • Releases greenhouse gases

Heavy Oils (Oil Sand and Oil Shale)

• Advantages:
  • Potentially large supplies
• Disadvantages:
  • Low net energy yields
  • Higher environmental impacts

Dependence on Oil

• Fossil fuels (crude oil and natural gas):
  • 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

• Drill a well vertically or horizontally.
• Oil flows out of rock pores due to pressure difference.
• Pumped out (requires energy and money).

Petrochemicals

• Products of oil distillation.
• Raw materials.

Oil Extraction and Recovery

• Primary recovery:
  • Underground pressure forces oil and gas to the surface.
• Secondary recovery:
  • Pressure falls over time.
  • Fluids injected to increase reservoir pressure (water and gas injection).
• Enhanced recovery:
  • Steam injected to increase mobility of thick, heavy oil.

Types of Oil

• Light Oil (Conventional):
  • Petroleum or crude oil.
  • 30% of the world’s estimated supply.
• Heavy Oil (Unconventional):
  • Thick.
  • 70% of the world’s estimated supply.
  • Some left behind in wells.
  • Some extracted from tar sands and oil shale rock (expensive).
  • Reduces net energy yield.

Refining Crude Oil

• Fractional distillation:
  • Separates crude oil into different hydrocarbon products.
  • Based on differences in molecular weight and boiling points.
  • Lighter components boil at lower temperatures.

Trade-Offs: Conventional Oil

Heavy Oil from Sand

• Oil sand/tar sand:
  • Mixture of sand, clay, water, and bitumen.
  • Bitumen: thick, sticky, tarlike heavy oil (high sulfur content).
• Extraction:
  • Serious environmental impact: air, water, wildlife, climate.
  • Low net energy yield.
  • Is it cost-effective?
  • Mixed with hot water and steam.

Oil Shales

• Oily rocks containing kerogen:
  • Solid combustible mixture of hydrocarbons.
  • Must be heated 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.
• Mixture of gases (50-90% $CH_4$).
• Liquefied petroleum gas (LPG): propane and butane liquefied under high pressure.
• Liquefied natural gas (LNG):
  • Low net energy yield.
  • Cooled to -162°C for storage/transport.
  • Refrigerated tanker ships.

Advantages of Natural Gas

• Will natural gas be the bridge fuel 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.
• Disadvantages:
  • Very high environmental impact.
  • Degrades land and pollutes water and air.
  • Burning it severely pollutes the air.

Stages in Coal Formation

• Peat (not a coal) -> Lignite (brown coal) -> Bituminous (soft coal) -> Anthracite (hard coal).
• Increasing heat and carbon content, decreasing moisture content.

Science: Coal-Burning Power Plant

• Burns coal to produce steam.
• Steam spins a turbine, which spins a generator to create electricity.
• Steam is cooled, condensed, and returned to the boiler.

Environmental Impacts of Coal Mining

• Surface mining:
  • Eliminates vegetation.
  • Destroys soil profile.
  • Destroys wildlife habitat.
  • Degrades air quality.
  • Alters land uses.
  • Movement, storage, and redistribution of soil disrupts soil microorganisms.

Coal: Plentiful but Dirty Fuel

• World’s most abundant fossil fuel.
• Environmental costs of burning coal:
  • Severe air pollution.
  • Sulfur released as $SO_2$.
  • Soot.
  • $CO_2$
  • Trace amounts of mercury (Hg) and radioactive materials.

Trade-Offs: Coal

Top 3 Countries (Fall 2024 est.)

Nuclear Energy

• Advantages:
  • Low environmental impact.
  • Very low accident risk.
• Disadvantages:
  • High costs.
  • Low net energy yield.
  • Long-lived radioactive wastes.
  • Vulnerability to sabotage.
  • Potential for spreading nuclear weapons technology.

How Nuclear Fission Reactor Works

• Controlled nuclear fission reaction.
• Fueled by uranium ore (pellets in fuel rods and assemblies).
• Water is the usual coolant.
• Containment shell for protection.
• Water-filled pools or dry casks for spent fuel rod storage.

After Use

• After 3-4 years, spent fuel rods are removed and stored in water.

Radioactivity of Nuclear Waste

• Diminishes with time.
• Must be isolated for sufficient time to reduce radioactivity.
  • Days to years.
• Spent fuel rods:
  • 5 years of cooling.
  • Must be stored safely for thousands of years.

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.

What Happened to Nuclear Power?

• Slowest-growing energy source (expected to decline).
• Reasons:
  • Economics.
  • Poor management.
  • Low net energy yield.
  • Safety concerns.
  • Need for government subsidies.
  • Concerns of transporting uranium.

Case Studies: Nuclear Accidents

Three Mile Island (U.S., 1979)

• Nuclear reactor lost coolant.
• Partial melting of radioactive core.
• Radioactivity escaped.
• Increased public concerns and safety regulations.

Chernobyl (Ukraine, 1986)

• Explosions caused roof of reactor building to blow off.
• Partial meltdown and fire for 10 days.
• Radioactive cloud spread over many countries.
• 350,000 people evacuated.
• Effects on human health, water supply, and agriculture.

Trade-Offs: Conventional Nuclear Fuel Cycle

Trade-Offs: Coal vs. Nuclear

Radioactive Wastes

• Difficult problem.
• High-level radioactive wastes:
  • Must be stored safely for 10,000–240,000 years.
• Deep burial: safest and cheapest option?
• No facility exists.

Nuclear Fusion

• Power of the future?
• Still in the laboratory phase.
• Large-scale experimental reactor planned by 2040.

Top 3 Countries (Fall 2024 est.)

• Nuclear Energy:
  • US
  • China - France
  • Russia
• Site Locations:
  • Cordova (50 miles from commercial areas).
  • International distance approximately 26 km.

Renewable Energy

• From sources that:
  • Do not deplete.
  • Can be replenished within a human’s lifetime.
• Examples:
  • Wind.
  • Solar.
  • Geothermal.
  • Biomass.
  • Hydropower.

Efficiency as an Energy Resource

Reducing Energy Waste

• Advantages:
  • 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.
• Use energy-efficient windows.
• Stop other heating and cooling losses.
• Heat houses more efficiently (superinsulation)
• Heat water more efficiently (solar heaters).
• Use energy-efficient appliances (refrigerators, electric stoves).
• Use energy-efficient lighting.

Renewable Energy: A Solution?

• Use renewable energy in place of nonrenewable energy sources:
  • Solar energy.
  • Geothermal energy
• Benefits of shifting to locally available renewable energy resources.

Solar Energy

• Derived from the sun (Latin word for sun).
  • Thermal Conversion (Sunlight focuses to thermal receptors and converts water to steam then turbines rotary power produces electricity.)
  • Photo-conversion (Sunlight directly converts into electrical energy.)

Applications

• 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

• Free energy source.
• Does not cause pollution.
• Can be used in remote areas.
• Powers low-power consuming devices effectively.

Solar Energy: Advantages and Disadvantages

Passive and Active Solar Heating Systems

• Advantages:
  • Effectively heat water and buildings.
• Costs of using direct sunlight to produce high-temperature heat and electricity are decreasing.

Sunlight to Produce High-Temperature Heat and Electricity

• Solar thermal systems:
  • Central receiver system.
• Disadvantages:
  • High cost.
  • Low net energy yields.
  • Limited suitable sites.
  • Sunny, desert sites.

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

Using Solar Cells to Produce Electricity

• Photovoltaic (PV) cells (solar cells):
  • Convert solar energy to electric energy.
  • Thin wafers of silicon (Si) or with trace amounts of metals.
  • Free energy?
• Solar-cell power plants.
• Key problem: high cost.
• Will the cost drop with:
  • Mass production?
  • New designs?
  • Nanotechnology?

Photovoltaic

• Direct conversion of light into electricity at the atomic level.
• Materials absorb photons of light and release electrons.
• Free electrons create an electric current.

Trade-Offs: Solar Cells

Top 3 Countries (Fall 2024 est.)

• Solar Energy:
  • China
  • USA/India
  • Japan/Germany

Hydro-Electric Power

• Electricity generated by hydropower.
• Uses gravitational force of falling or flowing water.
• Most widely used form of renewable energy.
• Accounts for 16% of global electricity generation.

Electricity from the Water Cycle

• Generated by:
  • Overdams.
  • Tidal flows.
  • Ocean waves.
• Environmental concerns and limited suitable sites restrict use of these energy resources.
• World’s leading renewable energy source used to produce electricity.

Trade-Offs: Large-Scale Hydropower

Small Hydro Power (SHP)

• Clean, renewable, and relatively inexpensive energy.
• Does not necessitate a reservoir.
• Can be constructed where enough water flow and head exist.
• Minimal impact on nearby communities (no displacement).

Advantages of SHP

• Clean energy source (no water or air pollution).
• Renewable energy source (non-consumptive water use).
• Minimal impact on the environment.
• Long useful life and low running cost.

Disadvantages of SHP

• Energy consumers must be located near the scheme.
• Seasonal stream flow variation causes energy supply disturbances.
• Stream flow limits power generation.

Energy Derived from Oceans

• Marine energy: energy carried by ocean waves, tides, salinity, and temperature differences.
• Movement of water creates kinetic energy.
• Can be harnessed to generate electricity.

Tides and Waves

• Produce electricity from flowing water.
• Power systems are limited.
• Disadvantages:
  • Few suitable sites.
  • High costs.
  • Equipment damaged by storms and corrosion.

Top 3 Countries (Fall 2024 est.)

• Hydropower:
  • China
  • Brazil
  • Canada

Producing Electricity from Wind

• Wind: indirect form of solar energy.
• Captured by turbines.
• Converted into electrical energy.
• Wind farms: on land and offshore.
• Wind energy is the least expensive and least polluting way to produce electricity (if environmental costs included).

Wind Energy

• Production of electricity from wind using wind turbines.
• Wind flows through turbine blades, rotating and spinning a rotor inside the generator.
• Multiple turbines work independently, combining energy and distributing it.

Advantages of Wind Energy

• Renewable resource.
• Little direct effect on the environment (no GHG problems).
• Modern turbines available up to 1MW; wind farms of 100-150 MW installed.
• Individual turbines are repairable (no farm shutdown).
• Farm land can be used for agriculture or farming activities.

Disadvantages of Wind Energy

• Covers large areas on ridges and hill tops.
• Noisy.
• Needs huge cabling and complex Electrical Engineering technology.
• Generates waste materials from damaged wind mills.
• Requires regular monitoring and recurring repair of electronics.

Trade-Offs: Wind Power

Top 3 Countries (Fall 2024 est.)

• Wind Energy:
  • China
  • US
  • Germany

Biomass

• Biomass fuels come from things that once lived.
• Examples: wood products, dried vegetation, crop residues, aquatic plants, garbage.
• Plants store the sun's energy to make food (photosynthesis ).
• Energy is trapped in the residue when plants die.

Biomass Process

• Energy transferred and stored in plants.
• Plants are cut or die; wood chips, straw, and other plant matter delivered to the bunker.
• Burned to heat water in a boiler to release steam.
• Steam directed to turbines with pipes.
• Steam turns turbine blades and generators.
• Charged magnetic fields produce electricity, which is sent to homes by cables.

Biomass Categories

• Traditional form:
  • Wood and agricultural residue burnt to produce energy.
• Non-traditional form:
  • Biomass converted to ethyl alcohol and methyl alcohol to be used as liquid fuels in the engine.
• Domestic use:
  • Organic waste decomposed anaerobically to produce a mixture of gases (Biogas) namely methane, Carbondioxide, Hydrogen Sulphide etc.
  • Biogas is a good biofuel used for cooking and lighting.

Methods to Convert Biomass to Energy

• Burning:
  • Direct burning of biomass is the simple method of energy production.
  • Wood and other forms of biomass burned for thousand years, to warm, to cook food, and other tools.
• Alcohol Fermentation:
  • In alcohol fermentation, the starch in organic matter is converted to sugar.
  • This sugar is then fermented by yeast.
  • The resulting ethanol is distilled and then blended with another fuel.
  • The end product “Gasohol” has been used successful in various countries as an alternative to regular gasoline.

Liquid Biofuels

• Biodiesel (From Vegetable oil).
• Bio-Ethanol (from agricultural and vegetable waste).
• Advantages over gasoline and diesel fuel produced from oil:
  • Biofuel crops can be grown almost anywhere.
  • No net increase in $CO_2$ emissions (if managed properly).
• Biggest producers of biofuel:
  • Brazil.
  • The United States.
  • The European Union.
  • China.

Methods to Convert Biomass to Energy

• Anaerobic Digestion:
  • Anaerobic digestion converts biomass, especially waste products, into methane and carbon dioxide.
  • The biomass is mixed with water and stored in an airtight tank.
• Pyrolysis:
  • Pyrolysis involves the heating of biomass in the absence of oxygen.
  • Biomass such as wood or agriculture waste is heated at or above 500oC and allowed to decompose into gas and charcoal.
  • The major advantage of pyrolysis is that carbon dioxide is not produced.
  • Produces ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood.

Biogas

• Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter such as garbage and sewage by anaerobic bacteria.
• Biogas is a fuel gas, consisting of 65% methane and about 30-35% $CO_2$ and 2% other gases.
• It is a renewable resource of energy resulting from biomass.

Biomass as an Energy Source

• Solid biomass:
  • A renewable resource.
  • Burning it faster than it is replenished net gain in atmospheric greenhouse gases.
  • Creating biomass plantations degrade soil biodiversity.
• Liquid biofuels (Example: Bio-Ethanol):
  • Derived from biomass.
  • Can be used in place of gasoline and diesel fuels.
  • Creating biofuel plantations could degrade soil and biodiversity and increase food prices and greenhouse gas emissions.

Trade-Offs: Biodiesel

Ethanol

• Made from plants such as sugarcane, corn, and switchgrass, and from agricultural, forestry, and municipal wastes.
  • Converting plant starches into simple sugars.
  • Then sugars are processed to produce ethanol

Cooling Buildings Naturally

• Technologies available:
  • Superinsulation and high-efficiency windows.
  • Light-colored roof.
  • Reflective insulating foil in an attic.
  • Geothermal pumps.
  • Plastic earth tubes underground.

Geothermal Energy

• The term Geothermal originates from two Geek words 'GEO' and 'THERM'.
• The Greek word ‘geo’ means the earth and ‘thermal’ means heat.
• Hot water trapped below the surface acts as a geothermal reservoir.

Geothermal Electricity

• One way of producing electricity from geothermal energy is by drilling wells into the geothermal reservoirs.
• The hot water that rises emerges at the surface as steam.
• The steam is used to drive turbines producing electricity.
• If the water is not hot enough to produce steam, it can still be used to heat homes and businesses, saving gas/electricity.

Geothermal Energy

• Heat stored in soil, underground rocks, fluids in the earth’s mantle.
• Great potential for supplying many areas with heat and electricity.
• Low environmental impact.
• Locations are limited.
• High cost of tapping large-scale hydrothermal reservoirs.
• Geothermal reservoirs could be depleted.
• Another potential source of geothermal energy? Hot, dry rock.

Geothermal Energy Noise Levels

• Geothermal energy requires pumps to move the water that provides the heating and cooling which means that some noise pollution may be generated in nearby spaces (when used in a residence there is no noise pollution outside the residence.)

Fuel Cells

• A device that generates electricity by chemical reaction.
• Three segments:
  • Anode.
  • Cathode.
  • Electrolyte and catalyst.
• Two electrodes, one positive (Anode) and the other negative (Cathode).
  • Electrolyte, which carries electrically charged particles from electrode to the other, and Catalyst, which speeds the reactions at electrodes

Fuel Cell Process

• Hydrogen atoms enter at the anode, where a chemical reaction strips them of their electrons.
• Hydrogen atoms are now "ionized" and carry a positive electrical charge.
• Negatively charged electrons provide the current through wires to do work.
• If alternating current (AC) is needed, the DC output must be routed through an inverter.

Fuel Cell Process

• Oxygen enters at the cathode.
• In either case hydrogen and oxygen form water, which drains from the cell.
• As long as a fuel cell is supplied with hydrogen and oxygen, it will generate electricity.

Fuel Cells Over Heat Engines

• High Efficiency.
• Virtually silent.
• No Pollutant emissions.
• Power plants located near the consumer.
• Provides electric power and heat as by-product.
  • Heat Exchanger which provides hotwater supply or for desalination of sea water.
• Electric transmission lines are not required and hence reduces transmission loss.

Hydrogen Fuel

• Fuel cells: 2$H<em>2$ + $O</em>2$ -> 2$H_2$O
• Great promise for powering cars and generating electricity.
• Eliminate most air pollution problems.
• Reduce threats of global warming.
• Must be produced without the use of fossil fuels.
• Some challenges: $CO_2$ levels depend on method of hydrogen production.
• Hydrogen-powered vehicles: prototypes available.
• Larger fuel cells under development.

Solutions: Decentralized Power System

• Electricity is produced by a large number of dispersed, small-scale micropower systems.

Solutions: Sustainable Energy Future

Improve Energy Efficiency

• Increase fuel-efficiency standards.
• Provide tax credits for buying efficient cars, houses, and appliances.
• Reward utilities for reducing demand.
• Increase energy efficiency research and development.

More Renewable Energy

• Increase use of renewable energy.
• Provide subsidies and tax credits.
• Increase renewable energy research and development.

Reduce Pollution and Health Risk

• Phase out coal subsidies and tax breaks.
• Levy taxes on coal and oil use.
• Phase out nuclear power subsidies, tax breaks, and loan guarantees.