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91 terms

APES Ch 20 and 21

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How much of the world's energy comes from fossil fuels?
80%
What are the most developed conventional alternatives?
nuclear, biomass, hydropower
When was nuclear power first commercially developed?
1950s
How much of the US energy is generated by nuclear?
20%
nuclear energy
the energy that holds together protons and neutrons within the nucleus of an atom
What drives the release of nuclear energy in power plants?
nuclear fission
nuclear fission
the splitting apart of atomic nuclei
nuclear reactors
facilities contained within nuclear power plants
Why is nuclear energy defined as nonrenewable?
Because of the limited supply of uranium
What does 235 U decay into?
Lead-207
Most uranium occurs in nature as what?
238U
Breeder reactors
a nuclear reactor that creates more fissile material than it consumes, make better use of fuel, generate more power, and produce less waste than conventional reactors
What uranium do breeder reactors use
238U
Why are breeder reactors so dangerous
They use liquid sodium as a coolant
nuclear fusion
the process that drives the sun's energy output
How does nuclear fusion work?
force together small nuclei of lightweight elements under extremely high temperatures and pressures
How many emissions does nuclear prevent?
600 million metric tons (8% of global greenhouse gasses)
How many nuclear power plants are there?
436 plants in 30 nations
What were the two big nuclear events?
Three Mile Island and Chernobyl
What happened at Three Mile Island?
Combination of mechanical failure and human error lead to a meltdown
meltdown
the accidental melting of uranium fuel rods inside the core of a nuclear reactor, releasing radiation
What happened at Chernobyl
Explosion destroyed a reactor, sending explosions into the atmosphere
How much has nuclear power grown per year?
2.5%
How many nuclear plants are in the US
103
Biomass
the organic material that makes us living organisms
biomass energy
harnessed from trees, charcoal from burned wood, and matter from agricultural crops, as well as animal wastes.
In developing nations, how much energy is biomass?
35%
biopower
biomass burned in power plants to generate heat and electricity
biofuels
biomass sources converted into fuels, primarily to power cars
What are the two primary biofuels?
Ethanol and biodiesel
Ethanol
produced by fermenting biomass
biodiesel
fuel for diesel engines produced from vegetable oils
How is biopower harnessed?
combusting biomass to generate electricity
gasification
the process in which biomass is vaporized in the absence of oxygen that can generate electricity when used in power plants to turn a gas turbine to propel a generator.
What is a big benefit of biomass
It is carbon neutral, since carbon released by burning biomass is carbon that has been pulled out of the atmosphere by photosynthesis.
What are the economic benefits of biomass?
support rural economy, reduce dependence on imported fuels, least expensive fuels, improved efficiency reduces cost.
What are drawbacks of biomass?
indoor air pollution, unsustainable harvesting, monoculture, wouldn't stop fossil fuel reliance
What is the EROI of biomass?
1.5:1
hydropower
the generation of electricity using the kinetic energy of water
What are the two ways hydropower is harnessed?
1. storage impoundments
2. "run of river" approaches
Most hydropower comes from which method?
impounding dams
storage techniques
water is impounded in a reservoir behind a dam, then let through the dam. As water passes through the dam, turbines are spun, creating electricity
run of river approach
Any of several methods used to generate hydropower without greatly disrupting the flow of water.
What are some countries that use hydropower
Canada, Brazil, Norway, Austria, Switzerland
What was the age of the dam?
1930s
What are the advantages of hydropower?
1. It's renewable
2. It's clean
When did hydropower peak?
1960s
What are the negative impacts of hydropower?
1. damming rivers destroys habitats
2. natural flooding cycles disrupted
3. thermal pollution
4. fragment habitat
How many of US rivers are dammed?
98%
Other 2% protected
What are the new renewable energy sources?
Sun, wind, geothermal heat, movement of ocean water, and hydrogen.
Why are new renewables called new?
1. Not yet used on a wide scale in modern industrial society
2. Harnessed using developing technology
3. They will play a bigger role in the future
What are the benefits of new renewables?
1. Alleviate air pollution
2. inexhaustible
3. diversify economy with a mix of energy
4. employment opportunities
How much solar energy does one square meter of earth surface recieve?
1 kilowatt of solar energy
passive solar
buildings are designed and materials are chosen to maximize absorption of sunlight in winter
active solar
makes use of technological devices to focus, move or store solar energy
When was solar first harnessed, and by who?
1767 by Horace de Sanssurre
Thermal mass
heat-absorbing materials that store and release later
Solar cookers
portable ovens that use reflectors to focus sunlight onto food and cook it.
PV cells
convert sun into electrical energy by making use of the photoelectric effect
photoelectric effect
occurs when light strikes on pair of plates in a PV cell, causing a release of electrons, which are attracted to the opposite plate.
What are the two plates PV cells are made of?
n-type (electron rich)
p-type (electron poor)
When was the federal tax credit for solar energy passed?
2005
What are the benefits of solar power?
1. Inexhaustible
2. quite, safe, low maitenence
3. Allows for local control over decentralized power
net metering
Houses or businesses with PV metering sell their excess power to a local power utility
What are the two big disadvantages of solar power?
1. Not every region is sunny enough
2. Cost of investment
What causes wind to blow
the sun
Wind turbines
mechanical assemblies that convert wind's kinetic energy to electrical energy
When was the first wind turbine to generate electricity used?
late 1800s
How tall is a typical wind turbine?
131-328 ft tall
How long are the typical blades on a wind turbine?
138-162 ft across
Why does having a different speed in the turning of a wind turbine matter?
1. Energy content increases as the square of its velocity
2. Increase causes more air molecules to pass through the wind turbine per unit time
How much faster is windspeed over water than land?
20% faster
Benefits of wind power:
1. No emissions once built
2. prevents emissions
3. Efficient based on EROI
4. Produce 23 times more than consume
5. Requires little maitenence
What are the downsides of windpower?
1. Wind is unpredictable
2. Some places are windier than others.
3. Threat to birds and bats lol
Why is geothermal power only renewable in principle?
Groundwater can run out faster than it's replenished, and patterns in geothermal activity shift over time.
What does GSHP stand for?
Ground source heat pumps
How do GSHPs work?
transfer heat from the ground into buildings, cool by reverse
Who are the leaders in geothermal power?
China, Japan, and US
What are some benefits of geothermal?
1. Reduces emissions
What are some drawbacks to geothermal?
1. Releases gas dissolved in water
2. Not always sustainable
3. limited to where energy can be tapped
Tidal energy
dams across outlets of tidal basins
Wave energy
harness the motion of wind-driven waves at ocean's surface
Ocean Thermal Energy Conversion
A potential energy source that involves harnessing the solar radiation absorbed by tropical oceans
closed cycle
warm surface water is piped into a facility to evaporate chemicals that boil at low temps
open cycle
warm surface water evaporated in a vacuum
Hydrogen economy
the use of renewable electricity to produce hydrogen fuel
electolysis
Electricity input to split hydrogen
What is the chemical equation for electrolysis
2H₂O → 2H₂ + O₂
What is the chemical equation for getting hydrogen from fossil fuels?
CH₄ +2H₂O → 4H₂ + CO₂
How do fuel cells produce electricity?
By joining hydrogen and oxygen (reverse formula of electrolysis)
What are some benefits of hydrogen fuel?
1. Never run out
2. Clean and non-toxic
3. Pure water and heat may be only waste products
4. Efficient