Unit 6: Energy Resources and Consumption 38-41

Nuclear power

-Electricity generated from the nuclear energy contained in nuclear fuel

-Uses almost the same processes as electricity from fossil fuels --> main difference is that nuclear power uses a radioactive isotope, uranium-235, as its fuel.

-The isotopes of nuclear fuel are unstable and are radioactive, emitting ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei.

Fission reaction

-Where a neutron strikes a large atomic nucleus and then splits into two or more parts, releasing more neutrons and heat energy.

Nuclear reactor

-Works similarly to a fossil fuel power plant --> The difference is in the start of the reaction with fuel rods, which starts the fission reaction and generates steam.

-In order to make sure the reaction doesn’t go too fast and get out of control, control rods are inserted to absorb excess neutrons to slow or stop the fission reaction.

Advantages of nuclear power

-No air pollution produced

-Allows for energy independence if fossil fuels are scarce for countries

-Little to no greenhouse gases produced by power plant

Disadvantages of nuclear power

-Expense to build plant is v high

-Uncertainty of nuclear waste and storage of waste

-Security concerns of having nuclear waste

-Greenhouse gases produced by mining and construction

-Possibility of dangerous nuclear accidents

Radioactive decay

-The spontaneous release of material from the nucleus, when a parent radioactive isotope emits alpha particles, beta particles, or gamma rays.

Half life

-The time it takes for half of the original radioactive parent atoms to decay --> states and measures radioactive decay

-^Using the half-life measurement allows us to determine the safety of radioactive nuclear waste.

-^Calculations of half-lives can be done to determine how many half-lives occur, and how much radioactivity is remaining after that time.

-Measured in becquerel (Bq), or curies

Nuclear waste.

-Nuclear waste is fuel that can no longer produce enough heat to be useful, but continues to emit radioactivity.

-This radioactivity puts out short-wave electromagnetic waves that can damage organs, cause radiation sickness, and death in the short term.

-Long term, those waves can damage DNA, leading to cancer or tumors.

-Fetuses, children, and adolescents are most vulnerable to the harmful effects of radiation and radioactive waste.

3 major nuclear accidents of note:

-Three Mile Island, Pennsylvania, USA - 1979 (water pump failed, reaction melted partially)

-Chernobyl, Ukraine - 1986 (backup generator failed, control rods didn't stop: led to explosion, worst accident)

-Fukushima, Japan - 2011 (earthquake and tsunami, 3 reactors melted down due to flood)

Yucca mountain

Only candidate for permanent underground storage site for 70,000 tons of high-level radioactive wastes from commercially operated power plants

Biomass

-Biological material that has mass, commonly referencing wood, charcoal, and animal manure.

-Liquid biomass fuels are ethanol and biodiesel.

-Solid biomass can be wood or charcoal (woody material heated without oxygen so that water and other compounds are driven off.)

-These resources are renewable if given enough time to replenish and regrow.

Air pollutants of wood and charcoal:

-Particulates/particulate matter

-Carbon monoxide

-Nitrogen oxides

-Volatile organic compounds

-Carbon dioxide

Particulates/particulate matter

Solid/liquid particles suspended in the air (soot)

Carbon monoxide

Colorless, odorless gas that is formed during complete submission of most materials

Nitrogen oxides

A by product of combustion of any fuel in the atmosphere

Volatile organic compounds

Organic compound that evaporate easily

Carbon dioxide

Byproduct of all combustion, modern carbon from woody material

manure

-Can be used as a fuel for indoor heating and cooking.

-Manure is a cost-effective and accessible resource, but can release particulate matter, carbon monoxide, and other pollutants.

Biofuels

-Liquid fuels created from processed or refined biomass

-Biodiesel and Ethanol

Biodiesel

-A diesel substitute produce by extracting and chemically altering oil from plants

-Serve as a direct substitute for petroleum-based diesel.

-Soybean oil, processed vegetable oil, and algae can be used to produce biodiesel.

-Biodiesel can emit carbon monoxide and takes more land to grow soybeans than corn.

-It can be carbon neutral, since it doesn't use fossil fuels, and is easy to get from spent cooking oil in restaurants.

Ethanol

-Alcohol made by converting starches and sugars from plant material into alcohol and CO

-The US is the leading producer of ethanol.

-Considered more environmentally friendly since it does not release fossil carbon.

-When used as a fuel gasohol's efficiency is reduced, and needs to refuel more often.

-When ethanol is made from corn, harvesting and growing the corn also produces a large amount of fossil fuel energy.

-^It can also cause food shortages through diverting crops that could be used for food, such as corn or sugarcane.

Passive solar heating

-The use of energy from the Sun that takes advantage of solar radiation without active technology.

-Can't be stored.

-Positioning buildings and covering buildings to absorb as much solar heat as possible is considered passive.

-It can also be used to cook food through solar ovens/cookers.

Thermal mass

A property of a building material that allows it to maintain heat or cold

Active solar energy

-Uses technology that captures and stores solar energy of sunlight with electrical equipment and devices.

-Solar heating systems, photovoltaic solar cells, and large-scale concentrating solar thermal systems

-Solar heating systems can provide domestic hot water, as well as heat swimming pools and homes

Photovoltaic systems

-Capture the energy from the Sun as light, not heat, and convert it to electricity.

-Use semiconductors, such as silicon, to generate a low-voltage electrical current when exposed to direct sunlight.

-Effectiveness is limited by location and season, e.g., hot seasons produce less electricity from PV solar cells.

Photoelectric effect

The emission of electrons from a material when light of certain frequencies shines on the surface of the material

Concentrating solar thermal systems

-Large-scale application of solar energy to electricity generation.

-Uses lenses or mirrors and tracking systems to focus sunlight from a large area into a small beam.

-Heat generated boils water and produces steam to use similarly as in thermal power plants.

Hydroelectricity

-Electricity generated by the kinetic energy of moving water.

-Renewable form of energy in many countries.

Water impoundment systems (dams)

-The storage of water in a reservoir behind a dam

-Require minimal fossil fuels to operate.

-Creates recreational areas, as well as downstream flood-control

-EX of hydroelectricity

Negatives of dams

-Flooding areas upstream of the dam, and displacing people.

-Many fish species cannot travel across dams without use of fish ladders.

-Expensive to build

-Cement production for dams also generates a large amount of carbon dioxide.

-Accumulation of sediments at the bottom of the reservoir results in siltation, reducing the amount of water held.

Three Gorges Dam:

Location: Yichang, Hubei, China

Cost of Project: 37 billion

Benefits of the Project: flood control, power generation, improved navigation, water resource management

Negative Impacts of the Project: displacement, environmental degradation

Tucurui Dam:

Location: Para, Brazil

Cost of Project: 5.5 billion

Benefits of the Project: power generation, industrial energy, navigation

Negative Impacts of the Project: displacement, environmental degradation

Aswan High Dam:

Location: Aswan, Egypt

Cost of Project: 1 billion

Benefits of the Project: flood control, drought prevention, energy production, agriculture

Negative Impacts of the Project: displacement, loss of fertile sediment, environmental degradation, archaeological loss

Itaipu Dam:

Location: between brazil and paraguay

Cost of Project: 19.6 billion

Benefits of the Project: renewable energy generation, energy supply, economic development

Negative Impacts of the Project: displacement, environmental destruction, political and financial strain

Run-of-the-river systems

-Hydroelectricity generation in which water is retained behind a low, small dam, or no dam

-EX of hydroelectricity

Tidal energy

-Energy that comes from the movement of water driven by the gravitational pull of the Moon

-EX of hydroelectricity

Geothermal energy

-Heat energy that comes from the natural radioactive decay of elements deep within the Earth.

-Can be used as a direct source of heat: hot groundwater can be piped into radiators to heat homes, or heat exchangers can collect heat.

-Can also be used in the same manner as a thermal powerplant, by using steam from water evaporated by the Earth's heat.

Large geothermal energy producers:

-The US, Indonesia, Philippines, and Turkey

-US: Yellowstone

Ground source heat pumps

-Technology that transfers heat from the ground into a building.

-Hot water heat pumps also extract heat from the area in a garage or basement and transfer it to water in a domestic water tank, to be used in household activities

Fuel cell

-An electrical-chemical device that converts fuel, such as hydrogen, into an electrical current.

-Fuel cells operate like a battery, but the electricity is generated by a reaction between two chemicals.

2H2 + O2 --> energy + 2H2O

Disadvantages of fuel cells:

-Energy is required for electrolysis

-Hydrogen is dangerous to transport

-In order to make a large impact, vehicles would need to be redesigned

Electrolysis

-Way to gather hydrogen

-An electric current is applied to water to split it into hydrogen and oxygen.

Wind energy

-Generated from the kinetic energy of moving air.

-Fastest-growing major source of electricity in the world.

-^Countries that have the largest wind energy capacity are: China, United States, Germany, India, Spain

Wind turbines

-Convert the kinetic energy of moving air into electricity in the same way that hydroelectric turbine harness the kinetic energy of moving water.

-Wind turbine towers are 100 m (330 feet) high and have blades 40 to 75 m (130-250 feet) long.

-Installed in rural areas near electrical transmission lines.

-Wind farms are increasing in number globally, but can also be built in offshore areas near water.

Advantages of wind energy

-Nondepletable

-No pollutants from energy generation

-Once manufactured and installed, no/low cost

-Land can be shared with other uses

Disadvantages of wind energy

-Batteries needed if turbines are off-grid

-Birds and bats killed by collisions w/ turbines

-Visually objectionable

-Sounds from turbines bothersome

Phantom loads:

-Electrical demand that draws electrical current even when it is turned off, e.g., gaming systems and cable boxes

Smart grid

-An efficient, self-regulating electricity distribution network that accepts any source of electricity and distributes it automatically to end users