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 intoanother form to perform a function Energy can be transformed to forms that are notuseful 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 othercountry in the world. The US is an industrialized country Example:graphs from 2008 show energyuses 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 onceliving organisms over the course of many years Combustion Reactions How do we use fossil fuels?
Fossil fuels contain energy in the form ofchemical potential energy that is stored in fossilfuels Fossil fuels stored energy is far higher than otherorganic substances Example:burning 1kg of coal releases two to threetimes 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 livingorganisms, fossil fuels are stored naturallyunderground Fossil fuels must be mined Petroleum Petroleum: a highly flammable liquid formed from thedecay of organisms, such as plankton and algae Humans pump millions of liters of petroleum every day A mixture of many different unique chemicalcompounds Most are hydrocarbons Contain hydrogen and carbon High energy bonds Bonds are broken when burned Fractional Distillation
Because petroleum contains many different typesof 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 towerand heated. The chemical compounds in the petroleum boil atdifferent temperatures. Materials with the lowest boiling points rise to the top ofthe tower as vapor are collected. Hydrocarbons with high boiling points, such as asphalt andsome types of waxes, remain liquid and are drained offthrough the bottom of the tower. Petroleum Use About 15 percent of the petroleum-basedmaterials that are used in the United States arenot used for fuel In addition to fuels, plastics and synthetic fabrics aremade from the hydrocarbons petroleum. Lubricants, such as grease and motor oil, as well as theasphalt used in surfacing roads, are made frompetroleum. Natural Gas Natural gas: a fossil fuel composed mostly ofmethan, CH4, but it also contains other gaseshydrocarbon such as propane, C3H8, and butane,C4H10. of energy consumed in the US comes from usingnatural gas Contains more chemical potential energy per kg thanpetroleum 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 beneathsediments, decays, and compacts Before the 1900s more than 90% of homes wereheated by burning coal Today, less than 25% Coal is often burned in power plants to generateelectricity Origin of Coal Coal is a mixture of hydrocarbons and otherchemical compounds. Compared to petroleum and natural gas, coalcontains more impurities, such as sulfur andnitrogen-based compounds. As a result, more pollutants, including sulfurdioxide and nitrogen oxides, are produced whencoal is burned. Electricity Graph shows the percentages of energy thatcomes 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 fuelis converted to electrical energy. No stage is 100 percent efficient. Thermal energyis released into the environment. The overall efficiency of a fossil fuel-burningpower 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, smokeis given off the pollutes the atmosphere with smallparticles 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 naturalgas Burning coal can release these impurities into airthat 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 quicklyas they are used As human population increases, production offossil fuel based products will continue toincrease, reserves of fossil fuels will decrease Fossil fuels will become more difficult to obtain To meet demands, some are looking foralternatives such as shale deposits Nonrenewable Resources Section 2 Nuclear Energy
Nuclear Fusion Fusion: when atomic nuclei combine at very hightemperatures The Sun is a giant nuclear reactor This process takes a small amount of mass and convertsit into huge amounts of thermal energy Fusion is the most concentrated energy source known Fusion-based power plants are not practical becausethe reaction occurs at millions of degrees Celsius Fission Fission: energy released when the nucleus of anatom splits apart Extremely small amounts of mass are converted tohuge amounts of energy 9% of US electricity is made using fission Nuclear power plants use thermal energy to generateelectricity Nuclear Reactors Nuclear reactor: uses the energy fromcontrolled nuclear reaction to generateelectricity All reactors share common parts They will contain: Fuel for fission Control rods Cooling system Nuclear Reactors The core of a reactor is the smallpart where fission occurs The core contains fuel rods andcontrol rods Control rods absorb neutrons fromradioactive decay Water acts as a coolant to removeheat Nuclear Fuel Only certain elements have nuclei that canundergo 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 nuclearreactor is usually uranium dioxide. Fuel Rods The core of a reactor contains about 100,000 kgof uranium in hundreds of fuel rods Cores contain pellets of uranium dioxide Tubes of fuel rods are bundled and covered inalloys For every kg of uranium that undergoes fission, 1gof matter is converted to energy 1g of matter converted to energy = energygenerated by burning 3 million kg of coal Fuel Rods The Nuclear Chain Reaction
Uranium atoms split to release neutrons whichcauses other atoms to split apart.This causes achain reaction When an atom of Uranium-235 (U-235) is hit by aneutron it splits into two smaller nuclei This causes two or three more neutrons to beemitted 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 muchheat In this case, cooling rods are used to absorb some ofthe neutrons and prevent them from striking other U- 235 atoms By raising or lowering the cooling rods, the reactioncan 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 asimilar way to burning fossil fuels Nuclear power plants to do not produce the samepollutants 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 beforereturned to streams or rivers The Release of Radioactivity
One of the most serious risks of nuclear power isthe release of harmful radiation from powerplants. The fuel rods contain radioactive elements withvarious half-lives. Some of these elements could harm livingorganisms if they were released from the reactorcore of a nuclear power plant The Disposal of Nuclear Waste
Nuclear waste: any radioactive material thatresults when radioactive materials are used. After about three years, not enough fissionable U- 235 is left in the fuel pellets in the reactor coreto sustain the chain reaction. The spent fuel contains radioactive fissionproducts in addition to the remaining uranium. Low-Level Waste Contain small amounts of radioactive material
Have short half lives By product of electricity generation, medicalresearch and treatments, pharmaceuticalindustry, and food preparation Low-level wastes are usually buried in trenchesabout 30m deep in special locations If dilute, some waste is released into air or waterwhere it will dissipate High-Level Waste Generated by nuclear power plants and nuclearweapons programs After a fuel rod is spent, it is stored in a deeppool of water Many high-level wastes have long half-lives High-level wastes remain radioactive for tens ofthousands of years Must be stored in extremely stable containers High-Level Waste One method of long-term waste storage incasesradioactive wastes in glass and ceramic thenplaced in protective metal containers Containers are then buried hundreds of metersbelow ground in stable rock formations or saltdeposits Section 3 Renewable Energy Resources
Energy Options Renewable Resources: an energy source that isreplaced by natural processes faster than humans canconsume the resource Demand for energy increases as Earths populationincreases Other sources must be used to meet the demand Some alternatives are renewable Energy From the Sun Photovoltaic cells: convert radiant energy fromthe sun directly into electrical energy About 1 billionth of the suns energy strikes earth The suns energy should last for billions of years its inexhaustible Solar energy is a renewable resource Many devices use photovoltaic cells Example: cars How Solar Cells Work Two layers of semiconducting material betweentwo 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 areejected from the electron-rich semiconductor. These electrons can travel in a closed circuit backto 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 toget Best forms focus solar power into a receiver Heated fluid is circulated through a boiler tomake 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 tunnelsat the base Energy from Water Rushing water spins a turbine, which rotates theshaft of an electric generator to produceelectricity Hydroelectricity Electricity produced from moving water
8% of electrical energy in the US made byhydroelectric power plants Very efficient with little pollution Reservoirs created by dams for hydroelectricpower 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 usingturbines to generate electricity Tide differences are limiting, only a few places onearth 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 haveenough wind to meet needs Renewable resource Energy from Inside Earth
The thermal energy that is contained in hotmagma is called geothermal energy. Heat is generated within Earth by the decay ofradioactive elements. This heat is called geothermal heat. Geothermal heat causes the rock beneath Earthscrust to melt. This hot molten rock beneath Earths surface iscalled magma Alternative Fuels The use of fossil fuels would be greatly reduced ifcars could run on other fuels or sources of energy. Cars have been developed that use electricalenergy supplied by batteries as a power source. Hydrogen gas is another possible alternative fuel.It produces only water vapor when it burns andcreates no pollution Biomass Fuels Biomass is renewable organic matter, such aswood, sugarcane fibers, rice hulls, and animalmanure. Biomass can be burned in the presence of oxygento convert the stored chemical energy to thermalenergy. Converting biomass is probably the oldest use ofnatural resources for meeting human energyneeds. Section 4 Population and Carrying Capacity
Population: all the individuals of one speciesliving in a particular area Carrying Capacity: the largest number ofindividuals of a particular species that theenvironment can support Since the mid-1800s human population hasincreased 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, theenvironment is threatened and populations suffer Irresponsible usage of earths resources couldresult in us reaching our carrying capacity People and the Environment
Pollutants: any substance that contaminates theenvironment You have an impact Electricity you use comes from fossil fuels.Thiscan affect the air you breath Water you use must be treated Impact on Land Land is affected when fossil fuels are extractedfrom earth Land: used for agriculture, forests, urbandevelopment, and waste management Deforestation: the clearing of forest land foragriculture, urban development, or logging Increases the amount of carbon dioxide in theatmosphere Can cause increases in atmospheric temperatures Urban Development Over time as population grows, urbandevelopment increases Highways, office buildings, parking lots Some communities, states, countries, and privatebusinesses try to preserve natural areas bydesignating them as historic sites or nationalparks 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 sanitarylandfills The rest is recycled or burned National and State Parks
National and state parks are areas of landprotected and preserved by the government. The forests, wetlands and grasslands, and parks inthe United States are safe from urbandevelopment, waste disposal, and extensivedeforestation Impact on Water Life on Earth would not be possible without water.
Plants need water to convert radiant energy intofood energy. Some animals make water their homes. Sixty percent of the human body is composed ofwater Sources of Water Pollution
Polluted water contains chemicals and organismsthat 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 ofair pollution Types of Air Pollution Photochemical smog: the pollution that resultsfrom the reaction between sunlight and vehicle orfactory exhaust Acid precipitation: sulfur-, nitrogen-, and carbon- based compounds released with moisture in theair Types of Air Pollution Reducing Pollution Ways to conserve resources
Composting yard and kitchen waste Low-flush toilets and leak-free faucets will helpreduce water impact Bicycling or using buses can help reduce impacton the air