Energy Resources & Consumption (Unit 9)

Overview of Energy Resources and Consumption

  • Definition of Nonrenewable Energy Resources: An energy source that has a finite supply, consisting primarily of fossil fuels and nuclear fuels.

  • Fossil Fuel: A fuel derived from biological material that underwent fossilization millions of years ago.

  • Nuclear Fuel: Fuel derived from radioactive materials that emit energy.

  • Categories of Energy Use (Unit 9 Topics):     * 1. Nonrenewable Energy Resources: Patterns of energy use, fossil fuel resources, and nuclear energy resources.     * 2. Achieving Energy Sustainability: Conservation, efficiency, renewable energy, biomass, water, solar, wind, geothermal, hydrogen, and future planning.

Common Energy Units

  • joule (J): The quantity of energy consumed when a 1-watt electrical device is operated for 1 second.

  • British thermal unit (Btu): The energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

  • calorie: The energy required to raise the temperature of 1 gram of water by 1 degree Celsius (Note: 1 food Calorie = 10001000 calories).

  • kilowatt-hour (kWh): The amount of energy expended by utilizing 1 kilowatt of electricity for a duration of 1 hour.

Worldwide Patterns of Energy Use

  • Distribution Disparity: Energy use is not distributed evenly across the globe. Only 20%20\% of the world's population resides in developed nations, yet they consume 50%50\% of the global energy annually.

  • National Consumption Stats:     * China: Holds the highest total energy consumption of any country.     * United States: Holds the highest per capita energy consumption.

  • Industrialization Correlation: Shifts in energy demand typically mirror the level of industrialization in a specific region or country.

  • Types of Energy Sources:     * Commercial Energy Sources: Bought and sold (e.g., fossil fuels); standard in developed nations.     * Subsistence Energy Sources: Gathered by individuals for immediate personal needs (e.g., sticks, straw, animal waste); common in less developed countries.

Patterns of Energy Use in the United States

  • Historical Transitions: The US transitioned from wood to coal, and then to petroleum.

  • Recent Trends: Natural gas use has seen a recent increase attributed to the practice of fracking.

  • Energy Mix: 80%80\% of US energy is derived from fossil fuels.

  • Self-Sufficiency: The US produces approximately 85%85\% of its energy needs; the remaining 15%15\% matches petroleum imports.

  • Sector Consumption: Industry ranks #1 and transportation ranks #2 for the highest energy use in the United States.

  • Variability: Energy usage fluctuates based on regional and seasonal factors.

Selection and Efficiency of Energy Forms

  • Application-Specific Suitability: Different forms of energy are better for specific tasks.

  • Key Considerations:     * Energy-to-mass ratio: Crucial for transportation; liquid fuel allows for longer travel per volume.     * Energy efficiency: Includes both the efficiency of obtaining the fuel and the process of converting that fuel into work.

  • Energy Return on Energy Investment (EROEI): A formula used to quantify efficiency.     * EROEI=Energy obtained from fuelEnergy invested to obtain fuel\text{EROEI} = \frac{\text{Energy obtained from fuel}}{\text{Energy invested to obtain fuel}}     * Example: If 100 J100\,J of coal is obtained from a surface mine requiring 5 J5\,J of energy expended:     * EROEI=100 J5 J=20\text{EROEI} = \frac{100\,J}{5\,J} = 20     * A higher EROEI value indicates a more efficient and desirable process.

Energy and Efficiency in Transportation

  • Public vs. Private: Public transportation is significantly more efficient than solo car travel.

  • EPA Standards (December 2021): Newest emission standards equate to approximately a 40 mpg40\,mpg average for vehicle fleets. This is projected to prevent more than 3.1 billion tons3.1\text{ billion tons} of CO2CO_2 emissions from passenger vehicles.

Electricity Generation and Distribution

  • Electricity as a Secondary Source: It is an energy carrier obtained from the conversion of primary sources like fossil fuels. It delivers energy in a usable form to end users.

  • Consumption: 40%40\% of US energy is used to generate electricity, but only 13%13\% of that is available to end users after domestic consumption/loss.

  • Generation Process Steps:     * 1. Coal is burned in a boiler.     * 2. Water is converted into steam.     * 3. Kinetic energy in the steam spins a turbine.     * 4. The turbine turns a generator.     * 5. Electricity is generated.     * 6. Electricity is transported to the electrical grid.

  • Definitions:     * Turbine: A device turned by steam, water, or wind to produce power.     * Electrical Grid: A network of interconnected transmission lines linking power plants with end users.

  • Generation Efficiencies:     * Natural Gas: Approximately 40%40\% efficient.     * Coal: Approximately 35%35\% efficient.     * Combined Cycle Plants: Can reach 60%60\% efficiency by using both exhaust gases and steam turbines.     * Cogeneration (Combined Heat and Power/CHP): Using fuel to generate electricity and produce heat simultaneously. Efficiencies can reach up to 90%90\%.

Power Plant Capacity

  • Capacity: The maximum electrical output of a plant. A typical US plant capacity is 500 MW500\,MW.

  • Production Calculations (for a 500 MW500\,MW plant):     * In 1 day: 500 MW×24 hours=12,000 MWh=12,000,000 kWh500\,MW \times 24\text{ hours} = 12,000\,MWh = 12,000,000\,kWh.     * In 1 year: 365×12,000,000 kWh=4,380,000,000 kWh365 \times 12,000,000\,kWh = 4,380,000,000\,kWh.

  • Capacity Factor: The fraction of time a plant operates in a year. Most thermal plants (nuclear/fossil fuel) have a capacity factor of approximately 0.90.9.

Fossil Fuel Resources: Coal

  • Definition: A solid fuel formed from plant materials (trees, ferns) preserved 280 to 360 million280\text{ to }360\text{ million} years ago.

  • Advantages:     * Energy-dense and plentiful.     * Inexpensive and easy to exploit via surface mining.     * Requires minimal refining and is easy to transport.

  • Disadvantages:     * Subsurface mining becomes necessary once surface resources are depleted.     * Combustion releases sulfur, CO2CO_2, lead, mercury, and arsenic.     * Residual Ash: Remains after combustion. In 2014, a Tennessee home was buried in coal ash when a holding pond failed.

Fossil Fuel Resources: Petroleum

  • Definition: A liquid mixture of hydrocarbons (oil, gasoline, kerosene), water, and sulfur found in underground deposits. The US Department of Energy treats oil, crude oil, and petroleum as synonymous.

  • Refining: Crude oil is refined into tar, asphalt, gasoline, diesel, and kerosene using boiling point temperatures to distinguish compounds.

  • Advantages:     * Energy-dense and easy to transport.     * Cleaner burning than coal.     * High energy-to-mass ratio makes it ideal for mobile combustion engines.

  • Disadvantages:     * Releases sulfur, mercury, lead, arsenic, and CO2CO_2 during combustion.     * Leaks/spills during extraction and transport can lead to explosions.     * Pipelines interfere with wildlife.     * Quebec Incident (2013): A train carrying oil derailed and exploded, killing 4747 people and destroying half of the downtown buildings.

  • ANWR (Arctic National Wildlife Refuge): A 19 million acre19\text{ million acre} refuge in NE Alaska. Proponents suggest it contains up to 378 billion gallons378\text{ billion gallons} of oil; opponents argue exploration will harm pristine habitats.

Fossil Fuel Resources: Natural Gas

  • Composition: 80–95%80\text{--}95\% methane; 5–20%5\text{--}20\% ethane, propane, and butane.

  • Usage: Primarily for industrial processes and electricity generation.

  • Advantages:     * Existing infrastructure for home heating.     * Fewer impurities; emits almost no sulfur dioxide.     * Emits only 60%60\% as much CO2CO_2 as coal when burned.

  • Disadvantages:     * Unburned methane is a potent greenhouse gas (25×25\times more effective at absorbing infrared energy than CO2CO_2).     * Fracking/extraction requires significant land, chemicals, and water.

Alternative Fossil Fuels

  • Oil Sands: Viscous deposits of bitumen (degraded petroleum) mixed with sand, clay, and water. Extraction requires 3 L3\,L of water per 1 L1\,L of bitumen and involves extensive surface mining.

  • Liquid Coal (CTL): technology to convert solid coal to liquid fuel. While coal reserves have 1000×1000\times more energy than petroleum, the environmental impact of mining is severe.

Energy Intensity and Efficiency Trends

  • US Per Capita Use: Level between 1990 and 2005, dropping recently.

  • Energy Intensity: Defined as energy use per dollar of GDP; has been decreasing steadily since 1980.

  • Hubbert Curve: Developed by M. King Hubbert. A bell-shaped curve representing oil use, predicting that extraction increases until approximately half the supply is used (Peak Oil).

  • Future Projections:     * Conventional oil: < 50\text{ years}.     * Natural gas: Depends on fracking extent.     * Coal: Potential to last 200 years200\text{ years}.

Nuclear Energy Resources

  • Process: Similar to fossil fuels (water $\rightarrow$ steam $\rightarrow$ turbine $\rightarrow$ generator), but uses the radioactive isotope Uranium-235 (235U^{235}U).

  • Fission: A nuclear reaction where a neutron strikes a large atomic nucleus, splitting it into parts and releasing neutrons and heat energy.

  • Energy Density: 1 g1\,g of 235U^{235}U contains 2–3 million2\text{--}3\text{ million} times the energy of 1 g1\,g of coal.

  • Reactor Components:     * Fuel Rods: Contain nuclear fuel in the core.     * Control Rods: Absorb neutrons to slow or stop reactions; prevent meltdowns; used during emergencies or maintenance.

  • Extraction: 2000 lbs2000\text{ lbs} of uranium ore yields only 6.6 lbs6.6\text{ lbs} of fuel because most ore is 238U^{238}U, which does not fission easily.

  • Advantages:     * No CO2CO_2 emissions during operation.     * High efficiency (1 kg1\,kg uranium = 20,000×20,000\times the energy of 1 kg1\,kg coal).

  • Disadvantages:     * Radioactive waste disposal concerns (cannot be incinerated or dumped in oceans). Potential site: Yucca Mountain.     * Failure risks: Three Mile Island, Chernobyl, Fukushima.     * Long lead times: 20–30 years20\text{--}30\text{ years} to plan and build.     * Health effects: Cancer, burns, miscarriages.

Nuclear Fusion

  • Definition: Lighter nuclei forced together to produce heavier nuclei.

  • Status: Promising but currently requires temperatures 10×10\times hotter than the sun's core; the energy input currently exceeds the output.

Energy Conservation and Efficiency

  • Energy Conservation: Finding ways to use less energy.

  • Energy Efficiency: Getting the same work from less energy.

  • Individual Reductions: Insulating homes, lowering thermostats, taking shorter showers, using bikes, carpooling, Energy Star appliances, using laptops over desktops.

  • Government Actions: Improving public transit, taxing fuels, offering tax credits for retrofitting, tiered rate systems, reducing peak demand (the greatest quantity used at once).

  • Sustainable Design:     * Passive Solar Design: Construction utilizing solar radiation without active tech. Features include equator-facing windows, double-paned windows, and roof overhangs (blocking high summer sun, allowing low winter sun).     * Thermal Mass: Property of building materials (stone, concrete) to remain hot/cold.

Renewable Energy Resources

  • Potentially Renewable: Can be regenerated indefinitely if not overharvested (e.g., wood, biofuel).

  • Nondepletable: Cannot be used up (e.g., wind, solar, hydroelectric, geothermal).

  • Modern vs. Fossil Carbon:     * Modern Carbon: Carbon in biomass recently in the atmosphere (months/years ago).     * Fossil Carbon: Carbon buried for millions of years.     * Carbon Neutral: An activity that doesn't change atmospheric CO2CO_2 concentrations.

Biomass Details

  • Wood: Used by 2–3 billion2\text{--}3\text{ billion} people for heating/cooking. Sustainability depends on growth keeping pace with removal (Net Removal results in CO2CO_2 increase).

  • Charcoal: Made by burning wood in low oxygen. Contains 2×2\times more energy by weight than wood; produces less smoke but releases CO2,CO,CO_2, CO, and PM.

  • Manure: Used when wood is scarce; removes microorganisms but causes respiratory issues via PM.

  • Ethanol: Alcohol from starches/sugars (mainly corn in US).     * Advantages: Higher oxygen content than gasoline, lowers some pollutants, positive EROEI (1:1.31:1.3).     * Disadvantages: Reduces gas mileage by 2–3%2\text{--}3\%, uses land needed for food, can increase CO2CO_2.

  • Biodiesel: Extracting/altering oil from plants (algae, soy, palm).     * Often mixed (80%80\% diesel / 20%20\% biodiesel).     * SVO (Straight Vegetable Oil): Can run modified diesel vehicles.

Hydroelectricity

  • Mechanism: Uses kinetic energy of moving water. 17%17\% of global electricity (China is leader). US gets 6.5%6.5\% from hydro.

  • Generation Methods:     * Run-of-the-River: Water flows through a channel; less flooding/intermittent.     * Water Impoundment: Storage in reservoirs behind dams. Largest in US: Grand Coulee. Largest in world: Three Gorges Dam.     * Tidal Systems: Driven by moon’s gravity. Limited potential due to required tide height differences.

  • Pros/Cons: No CO2CO_2, inexpensive electricity, recreational reservoirs. However, causes flooding, relocation (1.3 million1.3\text{ million} for Three Gorges), siltation (sediment accumulation requiring dredging), and disrupts aquatic life cycles.

Solar Energy

  • Passive Solar Heating: Use of thermal mass, equator-facing windows, and insulation.

  • Active Solar Energy:     * Solar Water Heating: Circulates non-freezing liquid through solar collectors to a heat exchanger.     * Photovoltaic (PV) Cells: Directly convert sunlight into electricity.     * Concentrating Solar Thermal (CST): Uses mirrors/lenses to focus sunlight onto a beam, evaporating water to turn a steam turbine. Best in deserts.

  • Pros/Cons: No emissions during operation, matches peak demand. However, PV manufacturing uses toxic metals and water, and battery storage/disposal involves environmental costs.

Wind and Geothermal Energy

  • Wind Energy: Fastest growing major electricity source. China leads in generation; Denmark leads in percentage. Blades turn a gear box connected to a generator.     * Pros/Cons: Nondepletable, no pollution. However, causes noise, bird deaths (40,000/year40,000/year in US), and bat deaths.

  • Geothermal Energy: Heat from radioactive decay deep in the earth. US, China, and Iceland are top producers.     * Ground Source Heat Pumps: Transfer ground heat (technically solar-derived) to buildings; 30–70%30\text{--}70\% energy savings.

Hydrogen Fuel Cells

  • Chemical Reaction: 2H2+O2→energy+2H2O2H_2 + O_2 \rightarrow \text{energy} + 2H_2O.

  • Mechanism: H2H_2 splits into protons (p+p^+) and electrons (e−e^-). Electrons generate electricity; protons combine with oxygen to form water.

  • Challenges: Rare in nature, explosive, requires energy to split from molecules like H2OH_2O or CH4CH_4, and storage/transportation issues.

The Energy Future

  • Best Approach: Minimize use via conservation/efficiency first, then choose renewable mixes wisely.

  • Smart Grid: An efficient, self-regulating network that distributes electricity from various sources automatically; reduces the impact of single-plant outages.

  • Cost: Renewable costs are falling; focus is shifting toward efficient energy storage solutions to reduce long-distance transport needs.