Chapter 11: ENERGY

Chapter 11: ENERGY « The Law of Conservation of Energy tells us thatwecan’tgetsomething for nothing, but we refuse to believeit. » Isaac Asimov, American Science Writer

11.1 Fossil Fuels to Electricity In thischapter, wewillbelookingat how wegetenergy and how we use it to power our world We’ll examine some alternative to ourmost important energyresources

Electricity: Energy on Demand Enormous amounts of electrical energy can be transported through a wire the diameter of a quarter Flow of electrons (tiny charged particles that whirl around the nucleus of an atom); to generate electricity, you just have to set the electrons in motion (move an electrically conductive material – copper wire – through a magnetic field) Electric generator is simply a device for converting mechanical energy into electricity

Fossil Fuels Power plants convert energy sources (fossil fuels: coal, oil, natural gas) into electricity Fossil fuels are rich in carbon compounds, which contain a lot of stored energy in their molecular bonds; burning them releases this energy as heat Also used to operate the engines of planes, trains, cars and buses World’s main source of energy: almost 90% of energy used

Dwindling Supplies of Fossil Fuels Fossil fuel supplies are limited; we are using them up at a rate much faster than they can be replaced naturally Much of the Earth’s oil supplies will be used up in our lifetime In U.S., 22% of known coal reserves will last only about 400 years at our current rate of consumption Other drawbacks: environment is threatened by exhaust from power plants and vehicles, oil spills, and strip mining for coal; large amounts of CO2 when fossil fuels are burned

Renewable and Nonrenewable Energy Resources Renewable resources are resources that are continually produced Ex: wind, sunlight Nonrenewable resources are resources that can be used up Ex: coal, oil There is always the possibility that new deposits of fossil fuels will be discovered, but we need to find ways to lessen the severity and/or rate at which they are being used up

11.2 Nuclear Energy Nuclear energy is the energy which holds the nucleus of an atom together (strong nuclear force) Powerful forces bind together the components of the atomic nucleus

How Nuclear Energy Works When those bonds are broken (nuclear fission) a huge amount of energy is released Uranium is the element whose atoms are most easily split using this process The fission process is dangerous because of the chance of a chain reaction A chain reaction is an uncontrolled release of nuclear energy like in a nuclear weapon In power plants, nuclear energy is released in a controlled manner The tremendous amount of heat released from the uranium; used to boil water and make high pressure steam to operate electric generators

Advantages of Nuclear Energy One gram of uranium can supply the same amount of energy as about 7000 lbs. of coal Well designed reactors can run for years without having to be shut down or refueled Nuclear energy does not add carbon dioxide to the atmosphere (unlike fossil fuels) Nations who do not have access to fossil fuels to produce electricity can use nuclear power instead

So Why Aren’t We Using more Nuclear Energy? One of the most serious disadvantage of nuclear energy is that it produces radioactive waste U.S. has no facility for the permanent disposal of its commercial nuclear waste; each has its own temporary storage facility There is a relatively short supply of nuclear fuel Nuclear power plants are very expensive to build; are very large and complex; and a fear of nuclear accidents

Safety Concerns Fission reaction creates radioactive products which are highly dangerous; if it gets out of control, enormous amounts of heat created will destroy reactors, spewing radioactive materials into the air, ex: Chernobyl (1986), Ural Mountains (1957) Many people died or were seriously injured; others contracted cancers as a result of their exposure to the high levels of radiation U.S. suffered a serious nuclear accident in 1979 at the Three Mile Island nuclear power plant

Nuclear Fusion Nuclear fusion occurs when light weight atoms like hydrogen are forced together to make heavier ones like helium The fusion process releases even more energy than fission without any toxic or radioactive side effects Scientists are currently trying to master the fusion process but with little to no success It takes a tremendous amount of pressure and heat to make the fusion process work Scientists can not replicate these conditions in a laboratory nor can they find or make a material that would not melt in the face of such awesome heat

11.3 A Sustainable Energy Future Our fossil fuel supplies are dwindling, while our appetite for energy is increasing Can no longer be careless with our energy consumption; need to find new energy sources, make the most of what we have, and use our resources efficiently

Energy Conservation The average American uses twice as much energy as an average European The best way to combat the “deficit” is by taking conservation measures – doesn’t mean making do with less, just using it wisely (turn down thermostat in the winter and putting on a sweater; use a fan in summer rather then an air conditioner, whenever you can; car pool, walk or ride a bike) Modify structures, systems and vehicles to use less energy and not waste as much

Energy For the Future What form of energy will be used to light our homes, cities, and power our vehicles in the future? That will be left to be seen, however, some of those energy resources may be in use today: solar, wind, hydroelectricity, geothermal, biomass, hydrogen

Solar Energy Energy from the sun Solar energy can be used in three basic ways: - Passive solar heating – used in homes made of materials that help insulate the inside in conjunction with high efficiency windows that maximize the ‘greenhouse effect.’ - Solar water heating – solar collectors capture the sun’s energy and transfer it to a mixture which flows through the collectors and is pumped through a heat exchanger which directly heats water for use in homes or pools Solar cells – are devices that change the sun’s energy into electricity; these are not efficient enough for large jobs and are very expensive to make

Wind Energy Energy in the wind can be harnessed by windmills which are attached to electrical generators Wind energy is a renewable source of energy Wind generated electricity is relatively inexpensive and efficient However, strong wind is not consistent enough in most areas to make it feasible Windmills are very large structures and their blades can interfere with communications (cell phones)

Hydroelectricity Electricity generated by the energy of moving water Made possible by large dams which channel a river’s energy Clean and renewable source of energy Can only be used by large moving bodies of water

Geothermal Energy Heat from the Earth’s interior can be used to convert water into the steam that drives electrical generators Overuse of this energy can deplete it’s availability; another disadvantage is that it can only be tapped in a few places so its availability is limited

Biomass Biomass is the organic matter in plants or plant products This form of energy is primarily from the burning of wood; wood is the major source of energy for much of the world In the U.S., more people are using wood to heat their homes in order to conserve fossil fuels; however, it produces carbon dioxide and other noxious gases

Waste to Energy Like other things, even waste products from industrial processes can be burned for energy An enormous amount of biomass exists as waste material; pulp and paper industries generate more than ½ of the energy it uses from its own waste products; Hawaiian sugar cane industry uses its waste and sells the excess electricity to the public

Liquid Fuels from Biomass Liquid fuels can be derived from certain types of biomass, ex: methane (a type of alcohol) comes from wood; Ethanol (another alcohol) comes from corn, fruit or agriculture waste Cars and trucks can run on either one with a little modification They burn cleaner than gasoline or diesel Gasohol is a blend between gasoline and alcohol (10% alcohol/90% gasoline); used in some parts of the U.S.; Brazil relies on it more than any other country

Hydrogen Most plentiful substance on Earth Water is 2 parts hydrogen, one part oxygen; when split from oxygen, hydrogen is a clean-burning gas that has great promise as a fuel for the future; it is a nonpolluting fuel Most internal-combustion engines can run on hydrogen gas without any major modifications Drawbacks: separating it from oxygen requires energy, cannot easily be stored in useful concentrations; it is not concentrated enough and would require large amounts at any one time so it would need to be either compressed to a very high pressure or chilled to extremely low temps (liquidify)

Chapter 11: ENERGY