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1、Chapter 8 Renewable and Alternative Energy Sources,World Wide Energy Production,15.2%alternative,84.8%fossil fuels,U.S.Energy Consumption,The four primary consumers of energy in the U.S.in 2007 wereIndustrial32%Transportation28%Residential22%Commercial18%93%of the energy generated and used in the U.
2、S.are from nonrenewable resources,World-wide,with the exception of coal,which has known reserves that will last a couple of centuries,the known reserves of oil are expected to be exhausted in your lifetime.Clearly,alternative energy sources are needed for the future,Alternative Energy Sources,We wil
3、l look at:Solar energyGeothermal powerHydropowerTidal PowerOcean thermal energy conversionWind energyBiomass,Alternative Energy Sources,Solar Energy,The Sun is free(nobody owns or controls it)In principle,the amount of solar energy that reaches the Earths surface could provide for all human energy n
4、eeds forever,Solar Energy,The distribution of solar energy over the continental U.S.in watts per square meterThe desert regions of the southwest U.S.receive the most sunlight,Clean Solar Energy,Solar energy is clean energyIt produces no hazardous solid,liquid or gas wastesIt does not create water or
5、 air pollution,Solar Energy,The two areas in which solar energy can make the greatest contribution are in space heating and in the generation of electricityThese are uses that account for two-thirds of U.S.energy consumption,Solar Heating,The simplest approach to solar heating is passive-solar heati
6、ngThe building design should allow the maximum amount of sunlight to stream in through south and west windows during the cooler monthsThis heats the house and materials inside,Solar Heating,Trees can be positioned to shade the house in summerWide eaves can shade windows in summer,but allow winter su
7、nlight to enterDrapes and shutters can insulate window areas in winter,Solar Heating,It has been estimated that 40 to 90%of most homes heating requirements could be supplied by passive-solar heating systems100%solar homes have been built,but such homes usually cost many tens of thousands of dollars
8、more to build,Retrofitting older homes to be solar efficient can be too costlyOver insulation can aggravate indoor pollution,Solar Electricity,Direct production of electricity using sunlight is accomplished using photovoltaic cells,also called solar cellsThey have no moving parts and are“clean”energ
9、y,They are used to power the space station and to provide electricity in remote areas on Earth,Solar Electricity,A major limitation is cost,which greatly exceeds the cost of producing electricity using fossil fuels or nuclear powerThe best solar cells are only 20%efficient and only provide 50 watts
10、of electricity per square meter of cell size,Solar Electricity,A 100 watt light bulb would require 2 square meters of solar cellsAnd a 100-megawatt power plant would require 2 square kilometers(0.78 square miles)of solar cells,This represents a major use of land and resource,which would use far more
11、 steel and concrete than a fossil fuel power plant,Storing Solar Electricity,In a solar energy home,extra electricity is stored in batteries for later useThis work well for one houseUnfortunately,no wholly practical technology has been developed to store large amounts of electricity,despite advances
12、 in batteries,Storing Solar Energy,Some possible schemes for storing the energy of solar generated electricity include breaking up water into oxygen and hydrogen to burn later as fuelsAlso pumping water to an elevated reservoir for later use as hydroelectric power generation,Solar Energy,Currently,s
13、olar energy provide less that 0.5%of the U.S.power needs,but even with existing technology,it could provide up to 15%,Solar Electricity,In summation,to make solar energy truly useful for large-scale power generation:We need more efficient solar cellsWe need a means of better storing electricity,Geot
14、hermal Power,Geothermal Power,Magma rising from the mantles brings unusually hot material near the surfaceHeat from the magma,in turn,heats any groundwaterThis is the basis for generating geothermal energy,Geothermal Power,The steam and/or hot water is used to create electricity or for heating,Geoth
15、ermal Power Plants,Worldwide,there are now about 40 geothermal power plants,especially in Japan,Mexico and the Philippines,Note that most geothermal power plants are built along plate tectonic boundaries,Geothermal Power Plants,How the geothermal energy is used depends on the temperature of the wate
16、r Three types of power plants are used to generate power from geothermal energy:Dry steam Flash Binary,Types of Geothermal Power,Dry steam plants take steam out of the ground and uses the steam to turn a turbine that spins a generatorThis was first done in Italy in 1904,Iceland,a volcanic island,has
17、 many geothermal areas that produce steam and are tapped to generate electricity,Types of Geothermal Power,Flash plants take super heated water,usually at temperatures over 200C,out of the ground,allowing it to boil as it rises to the surface,then separates the steam from the water and uses the stea
18、m to turn a turbine generator,A flash power plant in Japan,Types of Geothermal Power,In binary plants,the hot water flows through heat exchangers,boiling an organic fluid that spins the turbineFor all three types of power plants,the condensed steam and remaining geothermal fluid are injected back in
19、to the hot rock to pick up more heatThis is why geothermal energy is viewed as sustainable It is also very“clean”Only produces steam,The Geysers,California,The largest U.S.geothermal power plant is The Geysers in California(it uses dry steam)By 1989,a total of 10 billion watts of electricity was bei
20、ng produced by The Geysers and six other plants in the U.S.,Geothermal Power Plants,By the end of 2005 worldwide use of geothermal energy for electricity had reached 9.3billion watts,with an additional 28billion watts used directly for heating,In 1999,it was estimated that the U.S.could produce 100
21、billion watts of geothermal energy by 2050,Geothermal Heat,Even if the geothermal water is not as hot as steam,the warm water can be used to heat buildings,home and even greenhousesThis is routinely done in Russia and Iceland,In fact,using geothermal energy to heat is about 2-3 times as common as us
22、ing it to create electricity,Limitations,Each geothermal field can only be used for a period of time,a few decades,before heat extraction is seriously reducedSimply put,you can take hot water out of the ground faster than it can be renewed(even if you pump the water back into the ground)For example,
23、steam pressure at The Geysers has declined rapidly over recent yearsIt peaked at over 2 billion watts by 1991,but now in 2011 produces about 0.7 billion watts,Hydropower,One-third(33%)of all power plants in the U.S.are hydroelectric,but they only generate 6%of U.S.electricity needs,Hydropower,A cros
24、s-section of a typical hydroelectric damWater flows down the penstock,turns the turbine blades which power the generators,Hydropower,Water use for generating hydroelectric power is totally dependent on the available water(duh!)The Glen Canyon Dam in Utah is the classic example of building too big of
25、 dam for not enough water,Hydropower,Hydropower is a very clean,pollution-free,renewable energy sourceThe water is not consumed,but rather simply passes thru the generating equipment,and since several dams may occur along the same river,the water can be reused and reused,Hydropower,If every stream a
26、nd river in America was dammed to generate power,you still only provide 20%of current U.S.power needsThere are about 1000 dams in the U.S.and there is very little prospect of building any new onesIn fact,some older dams have been removed,such as the 162 years old Edwards Dam in Maine,Three Gorges Da
27、m,The Three Gorges Dam is now the largest hydroelectric dam in the world,Three Gorges Dam,As a size comparison,it is 5 times larger than the Hoover Dam on the Colorado River,Three Gorges Dam,The dam is 185 meters(600 feet)high and 2.3 kilometers(1.4 miles)wideIt has 26 hydroelectric power generators
28、 with a collective generating capacity of about 18,000 megawatts(the average nuclear power plant generates about 1000 megawatts),Three Gorges Dam,The Chinese began filling the reservoir in 2003When filled to capacity,the reservoir will hold 22 cubic kilometers of water,Three Gorges Dam,As with any e
29、ngineering project of great magnitude,there are serious problemsThe reservoir will eventually stretch over 600 kilometers(375 miles)in lengthIt will submerge 125,000 acres of prime farmland,Three Gorges Dam,1,900,000 people were forced to relocate,many against their willEntire cities have been aband
30、onedOver 1200 historic areas are being flooded,Three Gorges Dam,Three spectacular river gorges called Qutang,Wuxia and Xiling,all worthy of being national parks,have been flooded,Three Gorges Dam,Officials report that the cost is within its US$25 billion budget and insisted early on that the project
31、 would pay for itself through electricity generation,However,the project is thought to have cost more than any other single construction project in modern China,with unofficial estimates of US$100 billion or more,Tidal Power,All large bodies of water,including the oceans and large lakes,have tidesTi
32、dal power captures the energy contained in moving water mass due to tides,Tidal Power,Two types of tidal energy can be extracted:Kinetic energy of currents between ebbing and surging tidesPotential energy from the difference in height(or head)between high and low tides,Tidal Power,You can use the fl
33、owing water between low and high tides to generate electricity,similar to hydropower,Tidal Power,Turbines can be place on the ocean floor,for example at the entrance of a bay,where the flowing water can turn the fan to generate electricity,Tidal Power,Another option is to use under water turbines,wh
34、ich is like an underwater wind farmThis is currently being tested offshore of Scotlands Orkney IslandsThe ebbing and surging tidal flows turn 100 foot propellers,which each produce 1 megawatts of electricity,Ocean energy thermal conversion(OTEC)is a new,clean technology that is still in the developm
35、ental stageIt exploits the temperature difference between warm surface water and the cold water at depth to run a“heat engine”A heat engine is a device placed between a high temperature reservoir and a low temperature reservoir that produces energy,OTEC,Either the warm water is used directly to run
36、a turbine,or the heat is used to vaporize a working fluid(ammonia)which runs the turbine,OTEC,The cold water is used to chill down the water or vaporDrinkable,distilled fresh water is a by-product,The temperature difference must be at least 40oF(22oC)year round,which is only found near the equatorSo
37、 this emerging technology is best for tropic islands,OTEC,A test plant is currently being constructed at Keahole Pointe on the Kona coast of Hawaii and should become operational in 2013,OTEC,Wind energy has been utilized for thousands of years,Wind Energy,The wind is free,commonly available and can
38、provide clean,pollution-free energyTodays wind-turbines are very high tech,Wind Energy,In most places,the cost of commercial wind power on a large scale is not now economically competitive with conventionally generated electricityOne important factor is that with a doubling of wind speed,power outpu
39、t increases by a factor of 8,Wind Energy,The numbers indicate the percentage of 1990 regional electricity demand that full utilization of wind energy could meetClearly,the great plains have significant wind energy potential,Wind Energy,U.S.wind power capacity from 1981 to 2002,Wind Energy,U.S.wind p
40、ower capacity from 1996 to 2008,Wind Energy,The U.S.remains the world leader in wind energy,but Europe has embarked on an very ambitious wind-power development program,Wind Energy,It is predicted that by 2030,wind energy will supply at least twice the electricity it does now,It would take about 1000
41、 one-million watt windmills to equal the energy output of one sizable fossil fuel power plant,Wind Energy Limitations,The windmills can be noisy And they are hard on migrating birds,Biomass energy is derived from organic matterStoves that burn wood are the classic exampleIn fact,there had been a 20-
42、25%increase in the use of wood stoves over the past several decades,Biomass Energy,Biofuels differ from other renewable energy sources,such as wind,hydroelectric,geothermal and solar,as they are primarily used in the transportation sector and are derived from recently living matter,both plant and an
43、imal,Biomass Fuels or Biofuels,Ethanol fuel is a biofuel alternative to gasoline,which is gaining popularity world-wideCar engines can be designed to run on 10%,50%even 100%pure ethanol,Ethanol Fuel,It is cleaner burning than gasolineWorldwide,the use of ethanol is rapidly increasing,Ethanol fuel mi
44、xtures have E numbers which describe the percentage of ethanol in the mixture by volume,for example,E85 is 85%ethanol and 15%gasoline,“E”Numbers,Low ethanol blends,from E5 to E25,are also known as gasohol,though internationally the most common use of the term gasohol refers to the E10 blend,E10 gaso
45、hol is becoming more commonly found at gas stations in the U.S.(Tennessee is way behind)As the“10”indicates it is made from a mixture of gasoline(90%)and ethanol(10%),Gasohol,Gasohol has higher octane,or antiknock,properties than gasoline and burns more slowly,more cooler,and more completely,resulti
46、ng in reduced emissions of some pollutants,Ethanol Fuel,Automotive ethanol capabilities vary widely country to country,but most spark-ignited gasoline style engines will operate well with mixtures of up to 10%ethanol Brazil is the world leader in ethanol fuels,In Brazil,ethanol-powered and flexible-
47、fuel vehicles are manufactured to be capable of operation by burning hydrated ethanol,an azeotrope of 93%ethanol and 7%water,Ethanol Fuel,Ethanol fuel is produced from sugar cane in Brazil,which is a more efficient source of fermentable carbohydrates than corn as well as much easier to grow and proc
48、ess in the tropical climate,UT&Switchgrass,The UT Biofuels Initiative has started testing the use of switchgrass,which is believed to offer a greater ethanol yield than corn in a temperate climate,such as in Tennessee,UT&Switchgrass,The project represents the culmination of years of corporate resear
49、ch and development and a highly touted$40.7 million investment from the state of Tennessee to build a plant for demonstrating technology developed by DuPont Danisco Cellulosic Ethanol,Most of the world still relies very heavily on fossil fuels,but slowly but surely,attention is being diverted to alternative energyEnergy use in the future will not be dominated by a single source,Alternative Energy Sources,The most important aspects of most alternative energy sources is that they promise clean,pollution-free energy,Alternative Energy Sources,Chapter 9 Water Resources,
