energy paths in the ecosphere
DESCRIPTION
ENERGY PATHS in the ECOSPHERE. TREN 1F90 Sustainability, Environment and Tourism. ENERGY. What is it?. ENERGY. Defined as: THE CAPACITY TO DO WORK. What is it? BASIC DEFINITIONS AND LAWS. ENERGY. POTENTIAL ENERGY: Stored energy in all its forms When released, it can do work - PowerPoint PPT PresentationTRANSCRIPT
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ENERGY PATHS in the ECOSPHERE
TREN 1F90Sustainability,
Environment and Tourism
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ENERGY
• What is it?
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What is it?
BASIC DEFINITIONS AND LAWS
ENERGY
• Defined as:
THE CAPACITY TO DO WORK
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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
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ENERGY
KINETIC ENERGY:• Energy in motion
• Energy possessed by moving objects
Examples:• Falling leaf
• Diving kingfisher• Waterfall
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• POTENTIAL ENERGY
ENERGY
• KINETIC ENERGY
↕ INTERCONVERTIBLE ↕
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Laws of Thermodynamics
All energy follows basic laws of thermodynamics, central to the
understanding of ecological processes and environmental issues.
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Laws of Thermodynamics
FIRST LAW:Energy can be neither created nor destroyed – it can only change form.
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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.
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Laws of Thermodynamics
HEATis the inevitable
byproductof energy
transformations
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Laws of Thermodynamics
HEATCOAL
↓Burned to generate electricity
↓Transmission of electricity
through wires↓
Lighting of bulb filament↓
Light energy
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Laws of Thermodynamics
HEAT• May be defined
as the kinetic energy associated with the random motion of atoms and molecules
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Laws of Thermodynamics
HEAT• Useful in
concentrated form (e.g., internal combustion engine), but generally dissipated to the environment in a dilute form
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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)
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ENERGY CONCEPTS
ENERGY QUALITY:
All energy sources are degraded in quality with use, to a less useful form (heat)
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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
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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
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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
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ENERGY EFFICIENCY
• The ratio of useful energy output to the total energy input.
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ENERGY EFFICIENCY
Internal combustion engine in car
Energy in 1 litre of gas: 6500 kcal
Energy output from engineconsuming 1 litre of gas 1300 kcal
Energy efficiency: 1300 = 0.20 = 20% 6500
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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!
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NET ENERGY
Total energy available in a given source
minus
the energy used to find, concentrate, and deliver energy to the user
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NET ENERGYTar 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
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NET ENERGY
Food productionin 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 20th century
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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
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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:
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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
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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/ )
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Hope or hype? MSNBC On The Money, 23 May 2006 (http://www.msnbc.msn.com/id/12934470/ )
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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)
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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