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

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