Energy Sources and the Environment Chapter 8 Energy Sources and the Environment

Section 1 – Fossil Fuels Energy Resources Energy is used all the time in nature Thermal energy – furnaces, stoves Mechanical energy – cars, vehicles

Energy Transformation The Laws of Conservation of Energy State: Energy cannot be created or destroyed To use energy, energy must be transformed into another form to perform a function Energy can be transformed to forms that are not useful Example: Electricity flowing through power lines 10% is lost to thermal energy

Energy Use in the United States The US uses more energy than any other country in the world. The US is an industrialized country Example: graphs from 2008 show energy uses in the United States

Fossil Fuel Formation What are fossil fuels? Coal Natural gas Petroleum (Crude oil) How are fossil fuels formed? Formed from the dead and buried remains of once living organisms over the course of many years

Combustion Reactions How do we use fossil fuels? Fossil fuels contain energy in the form of chemical potential energy that is stored in fossil fuels Fossil fuels’ stored energy is far higher than other organic substances Example: burning 1kg of coal releases two to three times as much energy as burning 1kg of wood

Combustion Reactions

Formation and Obtaining Fossil Fuels How do fossil fuels form and how do we get them? Because they are formed from once living organisms, fossil fuels are stored naturally underground Fossil fuels must be mined

Petroleum Petroleum: a highly flammable liquid formed from the decay of organisms, such as plankton and algae Humans pump millions of liters of petroleum every day A mixture of many different unique chemical compounds Most are hydrocarbons Contain hydrogen and carbon High energy bonds Bonds are broken when burned

Fractional Distillation Because petroleum contains many different types of hydrocarbons, they must be separated Uses the process of fractional distillation

Fractional Distillation This separation occurs in distillation towers at oil- refineries. First, petroleum is pumped into the bottom of the tower and heated. The chemical compounds in the petroleum boil at different temperatures. Materials with the lowest boiling points rise to the top of the tower as vapor are collected. Hydrocarbons with high boiling points, such as asphalt and some types of waxes, remain liquid and are drained off through the bottom of the tower.

Petroleum Use About 15 percent of the petroleum-based materials that are used in the United States are not used for fuel In addition to fuels, plastics and synthetic fabrics are made from the hydrocarbons petroleum. Lubricants, such as grease and motor oil, as well as the asphalt used in surfacing roads, are made from petroleum.

Natural Gas Natural gas: a fossil fuel composed mostly of methan, CH4, but it also contains other gases hydrocarbon such as propane, C3H8, and butane, C4H10. ¼ of energy consumed in the US comes from using natural gas Contains more chemical potential energy per kg than petroleum or coal The cleanest burning fossil fuel

Coal Coal: a solid fossil fuel that is found in mines Forms from ancient swamps Forms as plant material is buried beneath sediments, decays, and compacts Before the 1900’s more than 90% of homes were heated by burning coal Today, less than 25% Coal is often burned in power plants to generate electricity

Origin of Coal Coal is a mixture of hydrocarbons and other chemical compounds. Compared to petroleum and natural gas, coal contains more impurities, such as sulfur and nitrogen-based compounds. As a result, more pollutants, including sulfur dioxide and nitrogen oxides, are produced when coal is burned.

Electricity Graph shows the percentages of energy that comes from different sources in the US

Electricity

Electricity

https://www.youtube.com/watch?v=rEJKiUYjW1E

Power Plant Efficiency Not all the chemical potential energy in the fuel is converted to electrical energy. No stage is 100 percent efficient. Thermal energy is released into the environment. The overall efficiency of a fossil fuel-burning power plant is about 35 percent.

The Cost of Fossil Fuels Using fossil fuels has some negative side effects When petroleum products and coal are burned, smoke is given off the pollutes the atmosphere with small particles Releases carbon dioxide Global warming can occur as a result

The Cost of Fossil Fuels Most abundant fossil fuel is coal Coal contains more impurities than oil or natural gas Burning coal can release these impurities into air that is then breathed by organisms Coal mining can also be dangerous Inhalation Risk of death or injury while mining

Nonrenewable Resources Fossil fuels are nonrenewable resources They are not regenerated in the earth as quickly as they are used As human population increases, production of fossil fuel based products will continue to increase, reserves of fossil fuels will decrease Fossil fuels will become more difficult to obtain To meet demands, some are looking for alternatives such as shale deposits

Nonrenewable Resources

Section 2 – Nuclear Energy Nuclear Fusion Fusion: when atomic nuclei combine at very high temperatures The Sun is a giant nuclear reactor This process takes a small amount of mass and converts it into huge amounts of thermal energy Fusion is the most concentrated energy source known Fusion-based power plants are not practical because the reaction occurs at millions of degrees Celsius

Fission Fission: energy released when the nucleus of an atom splits apart Extremely small amounts of mass are converted to huge amounts of energy 9% of US electricity is made using fission Nuclear power plants use thermal energy to generate electricity

Nuclear Reactors Nuclear reactor: uses the energy from controlled nuclear reaction to generate electricity All reactors share common parts They will contain: Fuel for fission Control rods Cooling system

Nuclear Reactors The core of a reactor is the small part where fission occurs The core contains fuel rods and control rods Control rods absorb neutrons from radioactive decay Water acts as a coolant to remove heat

Nuclear Fuel Only certain elements have nuclei that can undergo fission. Naturally occurring uranium contains an isotope, U-235, whose nucleus can be split apart. As a result, the fuel that is used in a nuclear reactor is usually uranium dioxide.

Fuel Rods The core of a reactor contains about 100,000 kg of uranium in hundreds of fuel rods Cores contain pellets of uranium dioxide Tubes of fuel rods are bundled and covered in alloys For every kg of uranium that undergoes fission, 1g of matter is converted to energy 1g of matter converted to energy = energy generated by burning 3 million kg of coal

Fuel Rods

The Nuclear Chain Reaction Uranium atoms split to release neutrons which causes other atoms to split apart. This causes a chain reaction When an atom of Uranium-235 (U-235) is hit by a neutron it splits into two smaller nuclei This causes two or three more neutrons to be emitted Causes a large chain reaction

The Nuclear Chain Reaction

A Constant Rate As the nuclear chain reaction occurs heat is produced Sometimes this can occur too fast creating too much heat In this case, cooling rods are used to absorb some of the neutrons and prevent them from striking other U- 235 atoms By raising or lowering the cooling rods, the reaction can be sped up or slowed This can allow for a constant rate to be found

Benefits and Risks of Nuclear Power Nuclear power is used to generate electricity in a similar way to burning fossil fuels Nuclear power plants to do not produce the same pollutants as fossil fuels and are cleaner

Benefits and Risks of Nuclear Power Mining uranium can cause environmental damage They do risk a nuclear meltdown Coolant from the core must be cooled before returned to streams or rivers

The Release of Radioactivity One of the most serious risks of nuclear power is the release of harmful radiation from power plants. The fuel rods contain radioactive elements with various half-lives. Some of these elements could harm living organisms if they were released from the reactor core of a nuclear power plant

The Disposal of Nuclear Waste Nuclear waste: any radioactive material that results when radioactive materials are used. After about three years, not enough fissionable U- 235 is left in the fuel pellets in the reactor core to sustain the chain reaction. The spent fuel contains radioactive fission products in addition to the remaining uranium.

Low-Level Waste Contain small amounts of radioactive material Have short half lives By product of electricity generation, medical research and treatments, pharmaceutical industry, and food preparation Low-level wastes are usually buried in trenches about 30m deep in special locations If dilute, some waste is released into air or water where it will dissipate

High-Level Waste Generated by nuclear power plants and nuclear weapons programs After a fuel rod is spent, it is stored in a deep pool of water Many high-level wastes have long half-lives High-level wastes remain radioactive for tens of thousands of years Must be stored in extremely stable containers

High-Level Waste One method of long-term waste storage incases radioactive wastes in glass and ceramic then placed in protective metal containers Containers are then buried hundreds of meters below ground in stable rock formations or salt deposits

Section 3 – Renewable Energy Resources Energy Options Renewable Resources: an energy source that is replaced by natural processes faster than humans can consume the resource Demand for energy increases as Earth’s population increases Other sources must be used to meet the demand Some alternatives are renewable

Energy From the Sun Photovoltaic cells: convert radiant energy from the sun directly into electrical energy About 1 billionth of the suns energy strikes earth The suns energy should last for billions of years – it’s inexhaustible Solar energy is a renewable resource Many devices use photovoltaic cells Example: cars

How Solar Cells Work Two layers of semiconducting material between two layers of conducting metal One layer of semiconductor is rich in electrons; one is poor in electrons

How Solar Cells Work When sunlight strikes a solar cell, electrons are ejected from the electron-rich semiconductor. These electrons can travel in a closed circuit back to the electron-poor semiconductor

Parabolic Troughs Focuses sunlight on a tube containing heat- absorbing fluid such as synthetic oil or liquid salt Used in remote areas where electricity is hard to get Best forms focus solar power into a receiver Heated fluid is circulated through a boiler to make steam Used in turbines

Energy from Water Steam can move a turbine Running water can be used the same way GPE of water is increased if a dam is used GPE is released when water flows through tunnels at the base

Energy from Water Rushing water spins a turbine, which rotates the shaft of an electric generator to produce electricity

Hydroelectricity Electricity produced from moving water 8% of electrical energy in the US made by hydroelectric power plants Very efficient with little pollution Reservoirs created by dams for hydroelectric power can be used for drinking water and crops Electricity is cheap after initial setup costs

Energy from Oceans Every day ocean levels rise and fall These tides can be used for hydroelectric power Water is trapped behind a dam At low tide, water flows back out to sea using turbines to generate electricity Tide differences are limiting, only a few places on earth have large enough tidal differences Waves and ocean currents can also be used

Wind Energy Windmills convert wind energy into electrical energy Wind spins a propeller connected to a generator Disadvantages are that few places on earth have enough wind to meet needs Renewable resource

Energy from Inside Earth The thermal energy that is contained in hot magma is called geothermal energy. Heat is generated within Earth by the decay of radioactive elements. This heat is called geothermal heat. Geothermal heat causes the rock beneath Earth’s crust to melt. This hot molten rock beneath Earth’s surface is called magma

Alternative Fuels The use of fossil fuels would be greatly reduced if cars could run on other fuels or sources of energy. Cars have been developed that use electrical energy supplied by batteries as a power source. Hydrogen gas is another possible alternative fuel. It produces only water vapor when it burns and creates no pollution

Biomass Fuels Biomass is renewable organic matter, such as wood, sugarcane fibers, rice hulls, and animal manure. Biomass can be burned in the presence of oxygen to convert the stored chemical energy to thermal energy. Converting biomass is probably the oldest use of natural resources for meeting human energy needs.

Section 4 – Population and Carrying Capacity Population: all the individuals of one species living in a particular area Carrying Capacity: the largest number of individuals of a particular species that the environment can support Since the mid-1800s human population has increased at a rapid rate Causes: advances in medicine, better nutrition, and availability of clean water

Population and Carrying Capacity If natural resources are used too quickly, the environment is threatened and populations suffer Irresponsible usage of earth’s resources could result in us reaching our carrying capacity

People and the Environment Pollutants: any substance that contaminates the environment You have an impact Electricity you use comes from fossil fuels. This can affect the air you breath Water you use must be treated

Impact on Land Land is affected when fossil fuels are extracted from earth Land: used for agriculture, forests, urban development, and waste management Deforestation: the clearing of forest land for agriculture, urban development, or logging Increases the amount of carbon dioxide in the atmosphere Can cause increases in atmospheric temperatures

Urban Development Over time as population grows, urban development increases Highways, office buildings, parking lots Some communities, states, countries, and private businesses try to preserve natural areas by designating them as historic sites or national parks

Waste Hazardous Wastes: wastes that are poisonous, causes cancer, or can catch fire Garbage affects the amount of hazardous waste About 55% of garbage is disposed of in sanitary landfills The rest is recycled or burned

National and State Parks National and state parks are areas of land protected and preserved by the government. The forests, wetlands and grasslands, and parks in the United States are safe from urban development, waste disposal, and extensive deforestation

Impact on Water Life on Earth would not be possible without water. Plants need water to convert radiant energy into food energy. Some animals make water their homes. Sixty percent of the human body is composed of water

Sources of Water Pollution Polluted water contains chemicals and organisms that cause disease Sediments can be pollutants Mining can release metals into water Examples: mercury, lead, nickel, and cadmium Oil and gas can run off Wastewater (sewage) contains human waste, household detergents, and soaps

Impact on Air Harms humans, plants, and animals Dust from construction contributes Volcanoes and forest fires are natural sources of air pollution

Types of Air Pollution Photochemical smog: the pollution that results from the reaction between sunlight and vehicle or factory exhaust Acid precipitation: sulfur-, nitrogen-, and carbon- based compounds released with moisture in the air

Types of Air Pollution

Reducing Pollution Ways to conserve resources Composting yard and kitchen waste Low-flush toilets and leak-free faucets will help reduce water impact Bicycling or using buses can help reduce impact on the air