Environmental Science Chapter 13: Energy

Key Concepts Energy use in the U.S. and around world Tradeoffs of different fossil fuels Tradeoffs of nuclear energy Improving energy efficiency Energy saving options for cars

Commercial Energy for the World and US Fig. 13-3, p. 287

Commercial Energy Use in US Since 1800 100 Wood Coal 80 Natural gas 60 Contribution to total energy consumption (percent) Oil 40 Hydrogen Solar 20 Nuclear 1800 1875 1950 2025 2100 Year Fig. 13-4, p. 288

Net Energy Ratios Space Heating Passive solar 5.8 Natural gas 4.9 Oil 4.5 Active solar 1.9 Coal gasification 1.5 Electric resistance heating (coal-fired plant) 0.4 Electric resistance heating (natural-gas -fired plant) 0.4 Electric resistance heating (nuclear plant) 0.3 Fig. 13-5a, p. 289

Major Oil, Natural Gas, and Coal Deposits in North America Fig. 13-7, p. 292

Tradeoffs of Conventional Oil Use Advantages Disadvantages Ample supply for 42-93 years Low cost (with huge subsidies) High net energy yield Easily transported within and between countries Low land use Technology is well developed Efficient distribution system Need to find substitute within 50 years Artifically low price encourages waste and discourages search for alternative Air pollution when burned Releases CO2 when burned Moderate water pollution Fig. 13-9, p. 293

Carbon Dioxide Emissions Per Unit Energy of Different Fuels 286% Coal-fired electricity Synthetic oil and gas produced from coal 150% 100% Coal 92% Oil sand 86% Oil 58% Natural gas 17% Nuclear power Fig. 13-10, p. 294

Tradeoffs of Natural Gas Conventional Natural Gas Advantages Disadvantages Ample supplies (125 years) Nonrenewable resource High net energy yield Releases CO2 when burned Low cost (with huge subsidies) Methane (a greenhouse gas) can leak from pipelines Less air pollution than other fossil fuels Difficult to transfer from one country to another Lower CO2 emissions than other fossil fuels Shipped across ocean as highly explosive LNG Moderate environmental impact Sometimes burned off and wasted at wells because of low price Low land use Easily transported by pipeline Requires pipelines Good fuel for fuel cells and gas turbines Fig. 13-13, p. 296

Increasing heat and carbon content Increasing moisture content Coal Increasing heat and carbon content Increasing moisture content Peat (not a coal) Lignite (brown coal) Bituminous Coal (soft coal) Anthracite (hard coal) Heat Heat Heat Pressure Pressure Pressure Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas Fig. 13-14, p. 296

Tradeoffs of Coal Fig. 13-15, p. 297 Trade-Offs Advantages Disadvantages Ample supplies (225–900 years) Very high environmental impact Severe land disturbance, air pollution, and water pollution High net energy yield Low cost (with huge subsidies) High land use (including mining) Mining and combustion technology well-developed Severe threat to human health High CO2 emissions when burned Air pollution can be reduced with improved technology (but adds to cost) Releases radioactive particles and mercury into air Fig. 13-15, p. 297

Tradeoffs of Nuclear Power Conventional Nuclear Fuel Cycle Advantages Disadvantages Large fuel supply High cost (even with large subsidies) Low environmental impact (without accidents) Low net energy yield High environmental impact (with major accidents) Emits 1/6 as much CO2 as coal Moderate land disruption and water pollution (without accidents) Catastrophic accidents can happen (Chernobyl) No widely acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants Moderate land use Low risk of accidents because of multiple safety systems (except in 35 poorly designed and run reactors in former Soviet Union and Eastern Europe) Subject to terrorist attacks Spreads knowledge and technology for building nuclear weapons Fig. 13-19, p. 301

Chernobyl fallout – April 26, 1986

Improving Energy Efficiency Big four energy-wasting devices Incandescent light bulb – wastes 95% of its energy input Nuclear power plants – 86% wasted Internal combustion engine (e.g., car) – 75-80% wasted Coal-burning power plants – 67% wasted

Saving Energy: Cars Fuel-efficient cars account for <1% of all car sales in U.S. Relatively low cost of fuel Preference of SUVs and trucks Government’s failure to increase fuel economy standards

Hybrid Gas-Electric Car Regulator Fuel Tank Trans- mission Battery bank Combustion engine Electric motor Fuel Electricity Fig. 13-24, p. 309

Hydrogen Fuel-Cell Car Universal docking connection Connects the chassis with the Drive-by-wire system in the body Body attachments Mechanical locks that secure the body to the chassis Rear crush zone absorbs crash energy Fuel-cell stack Converts hydrogen fuel into electricity Air system management Drive-by-wire system controls Cabin heating unit Side mounted radiators Release heat generated by the fuel cell, vehicle electronics, and wheel motors Front crush zone Absorbs crash energy Hydrogen fuel tanks © 2006 Brooks/Cole - Thomson Electric wheel motors Provide four-wheel drive Have built-in brakes Fig. 13-25a, p. 310

Hydrogen Fuel-Cell Car Fig. 13-25b, p. 310

What is E-85? Flex-fuel vehicles can run on gas or any ethanol-gas mixture Currently produced by Ford, Chrysler and GM E-85 85% ethanol / 15% gasoline Florida only has 2 stations and neither are accessible to the public

Other Alternative Fuels Biodiesel P-series http://www.eere.energy.gov/afdc/altfuel/altfuels.html Compare different fuels Find fueling stations More information

Number of E85 stations

Any Questions? News Story… Algal Fuel