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Environmental Biology Final exam
Lecture 13 & 15
29
Biology
Undergraduate 4
04/23/2012

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Term
Nonrenewable: Nuclear Energy
Definition
Energy that holds together protons & neutrons within the nucleus of an atom
o We harness this energy by converting it to thermal energy, which can be used to generate electricity
Term
Biomass
Definition
“Burning” recent photosynthesis for energy returns carbon to the atmosphere that would have cycled back to the atmosphere in a relatively short while anyway.
o Using biomass energy can be carbon-neutral with respect to carbon concentrations in atmosphere
o Can be burned, like coal, to generate electricity
o Can be converted to fuels used in transportation
Term
Biofuel
Definition
Ethanol: produced by fermentation of biomass, generally from carbohydrate-rich crops (corn)
• Biodiesel: diesel fuel produced by mixing vegetable oil used cooking grease, or animal fat with small amounts of methanol or ethanol and a chemical catalyst. (Less polluting than Diesel)
o Nontoxic
o Biodegradable
o Nonflammable
o Renewable
o Net energy balance (NEB) = (Energy value of Biofuel) – (energy required to produce Biofuel)
o NEB ratio= Biofuel output/ fossil fuel input
• Biodiesel has much smaller environmental impacts than ethanol in its production and when used as a fuel
Term
Renewable: Hydropower
Definition
o Water flowing through a dam =>spins turbines that turn generators to create electricity
o 98% of suitable rivers in the U.S. are dammed
Term
Hydropower pros and Cons
Definition
Pros
•Renewable as long as water is not overdrawn from the river system
•Clean: no greenhouse gas emissions
Cons
•Damns cause numerous disruptive ecological effects to rives and adjacent terrestrial systems
• Damns thus bring a mix of impacts for people
Term
Solar
Definition
o Enormous potential
o Sunlight striking earth the for 40 minutes is equal to global energy consumption for one year
o Currently only 0.06% of primary energy supply in the U.S
o Growing at 33% per year
o More expensive technologies are growing more slowly in developed countries
• Photovoltaic Cell: is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect.
• Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material.
• Concentrated solar
Term
Solar: Concentrated solar
Definition
metallic parabolic mirrors focus sunlight on pipe, heating fluid in pipe
Term
Solar: Photovoltaic power
Definition
generation employs solar panels composed of a number of solar cells containing a photovoltaic material.
Term
Solar Power key limitations
Definition
• Transmission lines
• Currently 500 miles DC transmission lines
• Need 100,000-500,000 miles
• Energy storage
• No electricity generated at night; little when cloudy
•Need to store excess power produced in daytime for use at might
o Compressed air storage
• Cost
Term
Renewable: WInd
Definition
Wind
o Takes kinetic energy of wing and converts it to electrical energy
o Fastest growing power source today
o Technology= Wind turbines, machines with turning blades that convert energy of motion into electrical energy by spinning a generator
Term
Wind Pros and Cons
Definition
• Pros
•Renewable as long as wind blows
•No emission after equipment made, installed
•Call allow local decentralized control over power, and local profit from electricity sales
• Costs lower after initial investments; costs dropping
• Cons
• Not everywhere is windy enough
• Windy sites can be far from population centers
• Some people object to aesthetics
• Blades kill birds, bats
• High start-up costs
Geothermal
Term
Geothermal
Definition
• Geothermal energy is thermal energy generated and stored in the Earth.
• Thermal energy is the energy that determines the temperature of matter.
• Earth's geothermal energy originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%).[27]
Term
Hydrogen
Definition
o Simplest and most abundant element in universe
o Could potentially serve as basis for clean, safe efficient energy system
o How it would work:
o Electricity generated from intermittent renewable sources like wind or solar can be used to produce hydrogen
o Fuel cells can then use hydrogen to produce electrical energy for power.
Term
Hydrogen:
pros and cons
Definition
Pros
• We will never run out of hydrogen
• Can be clean and nontoxic, with no greenhouse gas emissions
• Fuel cells potentially convenient, safe, and efficient
Cons
• Depending on way hydrogen is produced, it may not be environmentally clean
• Emission of hydrogen to atmosphere might have unforeseen impacts
Term
Land & ecosystem disturbances from mining
Definition
Coal
• Exclusive, on surface or underground
Nuclear
• Less extensive
Term
Green house gas emissions
Definition
Coal
• Sulfur dioxide, nitrogen oxide, particulate matter, and other pollutants
Nuclear
-Pollutant emissions
Term
Other air Pollutants
Definition
Coal
• Considerable emissions
Nuclear
• None from plant operation; much less then coal over the entire life cycle.
Term
Radioactive emissions
Definition
Coal
• No appreciable emissions
Nuclear
• No appreciable emissions during operation; possibility of emissions during severe accident
Term
Occupational health amongst workers
Definition
o Coal
• More unknown health problems & fatalities
o Nuclear
• Fewer known health problems & fatalities
Term
Health impact on near by residents
Definition
o Coal
• Air pollution impairs health
o Nuclear
• No appreciable know health impacts under normal operation
Term
Effects on accidents or sabotage
Definition
Coal
• No widespread effects
Nuclear
•Potentially catastrophic widespread effects
Term
Soil waste
Definition
Coal
• More generated
Nuclear
• Less generated
Term
Radioactive waste
Definition
Coal
• None
Nuclear
• Radioactive waste generated
Term
Fuel supply remaining
Definition
Coal
• Should last several 100 more years
Nuclear
• Uncertain; could last longer or shorter then coal supply
Term
Identify the two fastest growing renewable sources of energy;
Definition
1. Wind
2. Solar Thermal
Term
Identify the main reasons that some people object to wind energy systems;
Definition
• Not everywhere is windy enough
• Windy sites can be far from population centers
• Some people object to aesthetics
• Blades kill birds, bats
• High start-up costs
Term
Explain how the use of hydrogen as a “renewable” source of energy can be clean (no greenhouse gas emissions) or not completely clean;
Definition
• Electrolysis is the cleanest way:
o Use electrical energy to split water into hydrogen and oxygen.
• 2 H2O=> 2 H2 + O2
o This can potentially be very clean, releasing no greenhouse gas emissions.
However, cleanliness of hydrogen production depends...
o If the source of electricity need for electrolysis is not clean (e.g., From coal), then greenhouse emissions will still occur
• Besides electrolysis, hydrogen can also be produced from organic molecules like fossil fuels, thus results in greenhouse emissions.
o CH4 + 2H20 => 4H2 + CO2
• Also, it is possible that hydrogen production could have environmental impacts of its own.
Term
Explain why hydrogen is considered to be a renewable source of energy;
Definition
• It is considered to be a renewable source of energy because it is Electricity generated from intermittent renewable sources like wind or solar can be used to produce hydrogen
Term
Describe how biomass and fossil fuel energy sources are similar, and how they differ;
Similarities
Definition
• Can be burned, like coal, to generate electricity
• Can be converted to fuels used in transportation
Differences
• Nontoxic
• Biodegradable
• Nonflammable
• Renewable
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