BASIC DEFINITIONS AND LAWS ENERGY Defined as: THE CAPACITY TO DO WORK
ENERGY POTENTIAL ENERGY: Stored energy in all its forms When released, it can do work Examples: Coal, oil, gas Foodstuffs Rivers and streams above sea level
ENERGY KINETIC ENERGY: Energy in motion Energy possessed by moving objects Examples: Falling leaf Diving kingfisher Waterfall
POTENTIAL ENERGY ENERGY KINETIC ENERGY ↕ INTERCONVERTIBLE ↕
Laws of Thermodynamics All energy follows basic laws of thermodynamics, central to the understanding of ecological processes and environmental issues.
Laws of Thermodynamics FIRST LAW: Energy can be neither created nor destroyed – it can only change form.
Laws of Thermodynamics SECOND LAW: During transformations, energy goes from a concentrated form to a less concentrated form. Less concentrated energy is dissipated in the form of heat.
Laws of Thermodynamics HEAT is the inevitable byproduct of energy transformations
Laws of Thermodynamics HEAT COAL ↓ Burned to generate electricity ↓ Transmission of electricity through wires ↓ Lighting of bulb filament ↓ Light energy
Laws of Thermodynamics HEAT May be defined as the kinetic energy associated with the random motion of atoms and molecules
Laws of Thermodynamics HEAT Useful in concentrated form (e.g., internal combustion engine), but generally dissipated to the environment in a dilute form
ENERGY CONCEPTS ENERGY QUALITY The ability of a given form of energy to perform useful work Also called energy density High quality energy sources are concentrated (large energy content per unit of measure)
ENERGY CONCEPTS ENERGY QUALITY: All energy sources are degraded in quality with use, to a less useful form (heat)
ENERGY CONCEPTS ENERGY QUALITY: All energy sources are degraded in quality with use, to a less useful form (heat) ↓ Wise energy use requires careful matching of energy source with needs
ENERGY CONCEPTS Matching of energy source with needs: Use low quality energy for low-grade needs E.g., passive solar radiation for heating living spaces Use high quality energy for high-grade needs E.g., electricity to weld steel in industrial arc-welding
ENERGY DENSITY / QUALITY VERY HIGH HIGH MODERATE LOW Electricity, nuclear fission Natural gas, gasoline, coal, concentrated sunlight Geothermal, biomass, tar sands, oil shale Wind, ambient heat
ENERGY EFFICIENCY The ratio of useful energy output to the total energy input.
ENERGY EFFICIENCY Internal combustion engine in car Energy in 1 litre of gas: 6500 kcal Energy output from engine consuming 1 litre of gas 1300 kcal Energy efficiency: 1300 = 0.20 = 20% 6500
ENERGY EFFICIENCY Incandescent light bulb Every light bulb consuming 100 w of electricity radiates 5 w of visible light energy and 95 w of heat ↓ Incandescent light bulbs are about 95% efficient as heaters, but only 5% efficient as light sources!
NET ENERGY Total energy available in a given source minus the energy used to find, concentrate, and deliver energy to the user
NET ENERGY Tar sand oil extraction process Tar sands mined in open pits; Hot water and steam used to liberate oil ↓ Energy costs of extraction may be up to 80-90% of energy recovered ↓ Net value of extracted oil is only 10-20% of the oil’s true energy content
NET ENERGY Food production in industrial nations High yield agriculture requires large energy subsidy (fossil fuels for machinery and fertilizer production) ↓ Though total crop yields per hectare increased, the ratio of food energy produced to fuel energy used actually decreased through the mid- to late 20 th century
Ethanol fuel production Ethanol (a renewable alternative fuel) is produced primarily from corn Corn ethanol requires fossil fuel inputs for production (industrial agriculture) Net efficiency of ethanol was quite low prior to 1990s -> research shows it takes more fossil fuel energy to produce than the energy it yields Artificially high price of corn due to fuel use causes increased global food costs and contributes to famine and food shortages
Ethanol fuel production nitrogen fertilizers irrigation pumps gas + diesel fuels machinery (including energy costs of manufacture) drying of harvested corn seeds (includes all inputs required to produce the seeds) phosphorus fertilizers herbicides -Pimental et al. (1990) in Carrol et al: Agroecology Main fossil fuel inputs in US corn production are :
Ethanol fuel production Efficiency may have improved in past 20 years: 1991: 24% 1998: 36% 2001: 67% Shapouri (2004): attributed to technological advances in farming and manufacturing Source: Shapouri, Hosein. 2004. The 2001 net energy balance of corn-ethanol. www.usda.gov/oce/reports/energy/net_energy_balance.pdf www.usda.gov/oce/reports/energy/net_energy_balance.pdf
Ethanol fuel production Results vigorously disputed by some authorities “About 30 percent more fossil energy is required to produce a gallon of ethanol than you actually get out in ethanol” – David Pimental, 2006, cited in Ratigan, Dylan: Ethanol as gas replacement: Hope or hype? MSNBC On The Money, 23 May 2006 (http://www.msnbc.msn.com/id/12934470/ )http://www.msnbc.msn.com/id/12934470/
Hope or hype? MSNBC On The Money, 23 May 2006 (http://www.msnbc.msn.com/id/12934470/ )http://www.msnbc.msn.com/id/12934470/
Ethanol fuel production Ethanol subsidies called ‘catastrophically idiotic’ (Drum, 2012) Corn ethanol “worse than gasoline" for environment Corporate handout gave $0.45/gallon to ethanol producers and fuel blenders; cost taxpayers $6 billion in 2011 Subsidy expired at end of 2011 Replaced by revised 2007 Renewable Fuel Standard legislation, under the Energy Independence and Security Act (EISA)
Ethanol fuel production RFS program: U.S. govt. mandates that >37% of the 2011-12 corn crop be converted to fuel ethanol and blended with the gasoline that powers U.S. cars Profits go to agribusiness (corn production) and big oil (fuel blenders). 10% of farms (largest) collected 74 per cent of all subsidies between 1995 and 2010. upshot: ethanol subsidies didn't go away after all; they are just hidden a bit better! - Drum, Kevin. 2012. Ethanol Subsidies: Not Gone, Just Hidden a Little Better. Mother Jones
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