WIXLIB

EditorLeonard L. (‘‘Leo’’) Grigsby received his BS and MS in electrical engineering from Texas Tech Universityand his PhD from Oklahoma State University. He has taught electrical engineering at Texas Tech,Oklahoma State University, and Virginia Polytechnic Institute and University. He has been at AuburnUniversity since 1984 first as the Georgia power distinguished professor, later as the Alabama powerdistinguished professor, and currently as professor emeritus of electrical engineering. He also spent ninemonths during 1990 at the University of Tokyo as the Tokyo Electric Power Company endowed chair ofelectrical engineering. His teaching interests are in network analysis, control systems, and powerengineering.During his teaching career, Professor Grigsby has received 13 awards for teaching excellence.These include his selection for the university-wide William E. Wine Award for Teaching Excellence atVirginia Polytechnic Institute and University in 1980, his selection for the ASEE AT&T Award forTeaching Excellence in 1986, the 1988 Edison Electric Institute Power Engineering Educator Award,the 1990–1991 Distinguished Graduate Lectureship at Auburn University, the 1995 IEEE Region 3Joseph M. Beidenbach Outstanding Engineering Educator Award, the 1996 Birdsong Superior TeachingAward at Auburn University, and the IEEE Power Engineering Society Outstanding Power EngineeringEducator Award in 2003.Professor Grigsby is a fellow of the Institute of Electrical and Electronics Engineers (IEEE). During1998–1999 he was a member of the board of directors of IEEE as director of Division VII for power andenergy. He has served the Institute in 30 different offices at the chapter, section, regional, andinternational levels. For this service, he has received seven distinguished service awards, the IEEECentennial Medal in 1984, the Power Engineering Society Meritorious Service Award in 1994, and theIEEE Millennium Medal in 2000.During his academic career, Professor Grigsby has conducted research in a variety of projects relatedto the application of network and control theory to modeling, simulation, optimization, and control ofelectric power systems. He has been the major advisor for 35 MS and 21 PhD graduates. With hisstudents and colleagues, he has published over 120 technical papers and a textbook on introductorynetwork theory. He is currently the series editor for the Electrical Engineering Handbook Seriespublished by CRC Press. In 1993 he was inducted into the Electrical Engineering Academy at TexasTech University for distinguished contributions to electrical engineering.ß 2006 by Taylor & Francis Group, LLC.

ß 2006 by Taylor & Francis Group, LLC.

ContributorsMath H.J. BollenSTRILudvika, SwedenPatrick ColemanAlabama Power CompanyBirmingham, AlabamaSimon W. BowenAlabama Power CompanyBirmingham, AlabamaMurat DilekElectrical DistributionDesign, Inc.Blacksburg, VirginiaRobert P. BroadwaterVirginia Polytechnic Instituteand State UniversityBlacksburg, VirginiaD.A. DouglassPower Delivery Consultants, Inc.Niskayuna, New YorkSteven R. BrockschinkStantec ConsultingPortland, OregonMichael L. DyerSalt River ProjectPhoenix, ArizonaKristine BuchholzPacific Gas & Electric CompanyDanville, CaliforniaRichard G. FarmerArizona State UniversityTempe, ArizonaJim BurkeInfraSource TechnologyCary, North CarolinaCharles A. GrossAuburn UniversityAuburn, AlabamaWilford CaulkinsSherman & ReillyChattanooga, TennesseeJohn V. GrubbsAlabama Power CompanyBirmingham, AlabamaWilliam A. ChisholmKinectrics UQACToronto, Ontario, CanadaJames H. GurneyBC Transmission CorporationVancouver, British Columbia, CanadaGeorge L. ClarkAlabama Power CompanyBirmingham, AlabamaS.M. HalpinAuburn UniversityAuburn, Alabamaß 2006 by Taylor & Francis Group, LLC.

Andrew HansonPowerComm EngineeringRaleigh, North CarolinaRama RamakumarOklahoma State UniversityStillwater, OklahomaGary L. JohnsonKansas State UniversityManhattan, KansasManuel Reta-HernándezUniversidad Autónomade ZacatecasZacatecas, MexicoJohn G. KappenmanMetatech CorporationDuluth, MinnesotaGeorge G. KaradyArizona State UniversityTempe, ArizonaJohn R. KennedyGeorgia Power CompanyAtlanta, GeorgiaWilliam H. KerstingNew Mexico State UniversityLas Cruces, New MexicoChristopher J. MelhornEPRIKnoxville, TennesseeRoger A. MessengerFlorida Atlantic UniversityBoca Raton, FloridaPaul I. NippesMagnetic Products and Services, Inc.Holmdel, New JerseyJoe C. PohlmanConsultantPittsburgh, PennsylvaniaSaifur RahmanVirginia Polytechnic Instituteand State UniversityAlexandria, Virginiaß 2006 by Taylor & Francis Group, LLC.Kenneth H. SebraBaltimore Gas andElectric CompanyDameron, MarylandDouglas B. SeelyStantec ConsultingPortland, OregonRaymond R. ShoultsUniversity of Texas at ArlingtonArlington, TexasLarry D. SwiftUniversity of Texas at ArlingtonArlington, TexasRao S. ThallamSalt River ProjectPhoenix, ArizonaRidley ThrashSouthwire CompanyCarollton, GeorgiaGiao N. TrinhRetired from Hydro-QuébecInstitute of ResearchBoucherville, Quebec, Canada

IElectric PowerGeneration:NonconventionalMethodsSaifur RahmanVirginia Polytechnic Institute and State University1Wind Power Gary L. Johnson . 1-1Applications . Wind Variability2Advanced Energy Technologies Saifur Rahman . 2-1Storage Systems . Fuel Cells . Summary3Photovoltaics Roger A. Messenger . 3-1Types of PV Cells . PV Applicationsß 2006 by Taylor & Francis Group, LLC.

ß 2006 by Taylor & Francis Group, LLC.

1Wind Power1.1Applications . 1-2Small, Non-Grid ConnectedLarge, Non-Grid ConnectedGary L. JohnsonKansas State University1.2.Small, Grid ConnectedLarge, Grid Connected.Wind Variability . 1-4Land RightsThe wind is a free, clean, and inexhaustible energy source. It has served humankind well for manycenturies by propelling ships and driving wind turbines to grind grain and pump water. Denmark wasthe first country to use wind for generation of electricity. The Danes were using a 23-m diameter windturbine in 1890 to generate electricity. By 1910, several hundred units with capacities of 5 to 25 kW werein operation in Denmark (Johnson, 1985). By about 1925, commercial wind-electric plants using twoand three-bladed propellers appeared on the American market. The most common brands wereWincharger (200 to 1200 W) and Jacobs (1.5 to 3 kW). These were used on farms to charge storagebatteries which were then used to operate radios, lights, and small appliances with voltage ratings of 12,32, or 110 volts. A good selection of 32-VDC appliances was developed by the industry to meet thisdemand.In addition to home wind-electric generation, a number of utilities around the world have builtlarger wind turbines to supply power to their customers. The largest wind turbine built before the late1970s was a 1250-kW machine built on Grandpa’s Knob, near Rutland, Vermont, in 1941. This turbine,called the Smith-Putnam machine, had a tower that was 34 m high and a rotor 53 m in diameter. Therotor turned an ac synchronous generator that produced 1250 kW of electrical power at wind speedsabove 13 m s.After World War II, we entered the era of cheap oil imported from the Middle East. Interest in windenergy died and companies making small turbines folded. The oil embargo of 1973 served as a wakeupcall, and oil-importing nations around the world started looking at wind again. The two most importantcountries in wind power development since then have been the U.S. and Denmark (Brower et al., 1993).The U.S. immediately started to develop utility-scale turbines. It was understood that large turbineshad the potential for producing cheaper electricity than smaller turbines, so that was a reasonabledecision. The strategy of getting large turbines in place was poorly chosen, however. The Department ofEnergy decided that only large aerospace companies had the manufacturing and engineering capabilityto build utility-scale turbines. This meant that small companies with good ideas would not have therevenue stream necessary for survival. The problem with the aerospace firms was that they had no desireto manufacture utility-scale wind turbines. They gladly took the government’s money to build testturbines, but when the money ran out, they were looking for other research projects. The governmentfunded a number of test turbines, from the 100 kW MOD-0 to the 2500 kW MOD-2. These ran for briefperiods of time, a few years at most. Once it was obvious that a particular design would never be costcompetitive, the turbine was quickly salvaged.Denmark, on the other hand, established a plan whereby a landowner could buy a turbine and sell theelectricity to the local utility at a price where there was at least some hope of making money. The earlyß 2006 by Taylor & Francis Group, LLC.

TABLE 1.1Wind Power Installed es were larger than what a farmer would need for himself, but not what we would consider utilityscale. This provided a revenue stream for small companies. They could try new ideas and learn fromtheir mistakes. Many people jumped into this new market. In 1986, there were 25 wind turbinemanufacturers in Denmark. The Danish market gave them a base from which they could also sell toother countries. It was said that Denmark led the world in exports of two products: wind turbines andbutter cookies! There has been consolidation in the Danish industry since 1986, but some of thecompanies have grown large. Vestas, for example, has more installed wind turbine capacity worldwidethan any other manufacturer.Prices have dropped substantially since 1973, as performance has improved. It is now commonplacefor wind power plants (collections of utility-scale turbines) to be able to sell electricity for under fourcents per kilowatt hour.Total installed worldwide capacity at the start of 1999 was almost 10,000 MW, according to the trademagazine Wind Power Monthly (1999). The countries with over 50 MW of installed capacity at that timeare shown in Table 1.1.1.1 ApplicationsThere are perhaps four distinct categories of wind power which should be discussed. These are1.2.3.4.small, non-grid connectedsmall, grid connectedlarge, non-grid connectedlarge, grid connectedBy small, we mean a size appropriate for an individual to own, up to a few tens of kilowatts. Large refersto utility scale.1.1.1Small, Non-Grid ConnectedIf one wants electricity in a location not serviced by a utility, one of the options is a wind turbine, withbatteries to level out supply and demand. This might be a vacation home, a remote antenna andtransmitter site, or a Third-World village. The costs will be high, on the order of 0.50 kWh, but if thetotal energy usage is small, this might be acceptable. The alternatives, photovoltaics, microhydro, anddiesel generators, are not cheap either, so a careful economic study needs to be done for each situation.ß 2006 by Taylor & Francis Group, LLC.

1.1.2 Small, Grid ConnectedThe small, grid connected turbine is usually not economically feasible. The cost of wind-generatedelectricity is less because the utility is used for storage rather than a battery bank, but is still not competitive.In order for the small, grid connected turbine to have any hope of financial breakeven, the turbineowner needs to get something close to the retail price for the wind-generated electricity. One way this isdone is for the owner to have an arrangement with the utility called net metering. With this system, themeter runs backward when the turbine is generating more than the owner is consuming at the moment.The owner pays a monthly charge for the wires to his home, but it is conceivable that the utility willsometimes write a check to the owner at the end of the month, rather than the other way around. Theutilities do not like this arrangement. They want to buy at wholesale and sell at retail. They feel it isunfair to be used as a storage system without remuneration.For most of the twentieth century, utilities simply refused to connect the grid to wind turbines. Theutility had the right to generate electricity in a given service territory, and they would not toleratecompetition. Then a law was passed that utilities had to hook up wind turbines and pay them the avoidedcost for energy. Unless the state mandated net metering, the utility typically required the installation of asecond meter, one measuring energy consumption by the home and the other energy production by theturbine. The owner would pay the regular retail rate, and the utility would pay their estimate of avoidedcost, usually the fuel cost of some base load generator. The owner might pay 0.08 to 0.15 per kWh, andreceive 0.02 per kWh for the wind-generated electricity. This was far from enough to economicallyjustify a wind turbine, and had the effect of killing the small wind turbine business.1.1.3 Large, Non-Grid ConnectedThese machines would be installed on islands or in native villages in the far north where it is virtuallyimpossible to connect to a large grid. Such places are typically supplied by diesel generators, and have asubstantial cost just for the imported fuel. One or more wind turbines would be installed in parallelwith the diesel generators, and act as fuel savers when the wind was blowing.This concept has been studied carefully and appears to be quite feasible technically. One would expectthe market to develop after a few turbines have been shown to work for an extended period in hostileenvironments. It would be helpful if the diesel maintenance companies would also carry a line of windturbines so the people in remote locations would not need to teach another group of maintenancepeople about the realities of life at places far away from the nearest hardware store.1.1.4 Large, Grid ConnectedWe might ask if the utilities should be forced to buy wind-generated electricity from these smallmachines at a premium price which reflects their environmental value. Many have argued this overthe years. A better question might be whether the small or the large turbines will result in a lower netcost to society. Given that we want the environmental benefits of wind generation, should we get theelectricity from the wind with many thousands of individually owned small turbines, or should we use amuch smaller number of utility-scale machines?If we could make the argument that a dollar spent on wind turbines is a dollar not spent on hospitals,schools, and the like, then it follows that wind turbines should be as efficient as possible. Economies ofscale and costs of operation and maintenance are such that the small, grid connected turbine will alwaysneed to receive substantially more per kilowatt hour than the utility-scale turbines in order to breakeven. There is obviously a niche market for turbines that are not connected to the grid, but small, gridconnected turbines will probably not develop a thriving market. Most of the action will be from theutility-scale machines.Sizes of these turbines have been increasing rapidly. Turbines with ratings near 1 MWare now common,with prototypes of 2 MW and more being tested. This is still small compared to the needs of a utility, soclusters of turbines are placed together to form wind power plants with total ratings of 10 to 100 MW.ß 2006 by Taylor & Francis Group, LLC.

1.2 Wind VariabilityOne of the most critical features of wind generation is the variability of wind. Wind speeds vary withtime of day, time of year, height above ground, and location on the earth’s surface. This makes windgenerators into what might be called energy producers rather than power producers. That is, it is easierto estimate the energy production for the next month or year than it is to estimate the power that will beproduced at 4:00 PM next Tuesday. Wind power is not dispatchable in the same manner as a gas turbine.A gas turbine can be scheduled to come on at a given time and to be turned off at a later time, with fullpower production in between. A wind turbine produces only when the wind is available. At a good site,the power output will be zero (or very small) for perhaps 10% of the time, rated for perhaps another10% of the time, and at some intermediate value the remaining 80% of the time.This variability means that some sort of storage is necessary for a utility to meet the demands of itscustomers, when wind turbines are supplying part of the energy. This is not a problem for penetrationsof wind turbines less than a few percent of the utility peak demand. In small concentrations, windturbines act like negative load. That is, an increase in wind speed is no different in its effect than acustomer turning off load. The control systems on the other utility generation sense that generation isgreater than load, and decrease the fuel supply to bring generation into equilibrium with load. In thiscase, storage is in the form of coal in the pile or natural gas in the well.An excellent form of storage is water in a hydroelectric lake. Most hydroelectric plants are sized largeenough to not be able to operate full-time at peak power. They therefore must cut back part of the timebecause of the lack of water. A combination hydro and wind plant can conserve water when the wind isblowing, and use the water later, when the wind is not blowing.When high-temperature superconductors become a little less expensive, energy storage in a magneticfield will be an exciting possibility. Each wind turbine can have its own superconducting coil storageunit. This immediately converts the wind generator from an energy producer to a peak power producer,fully dispatchable. Dispatchable peak power is always worth more than the fuel cost savings of an energyproducer. Utilities with adequate base load generation (at low fuel costs) would become more interestedin wind power if it were a dispatchable peak power generator.The variation of wind speed with time of day is called the diurnal cycle. Near the earth’s surface, windsare usually greater during the middle of the day and decrease at night. This is due to solar heating, whichcauses ‘‘bubbles’’ of warm air to rise. The rising air is replaced by cooler air from above. This thermalmixing causes wind speeds to have only a slight increase with height for the first hundred meters or soabove the earth. At night, however, the mixing stops, the air near the earth slows to a stop, and the windsabove some height (usually 30 to 100 m) actually increase over the daytime value. A turbine on a shorttower will produce a greater proportion of its energy during daylight hours, while a turbine on a verytall tower will produce a greater proportion at night.As tower height is increased, a given generator will produce substantially more energy. However, mostof the extra energy will be produced at night, when it is not worth very much. Standard heights havebeen increasing in recent years, from 50 to 65 m or even more. A taller tower gets the blades into lessturbulent air, a definite advantage. The disadvantages are extra cost and more danger from overturningin high winds. A very careful look should be given the economics before buying a tower that issignificantly taller than whatever is sold a

The Electrical Engineering Handbook Series Series Editor Richard C. Dorf University of California, Davis Titles Included in the Series The Handbook of Ad Hoc Wireless Networks, Mohammad Ilyas The Biomedical Engineering Handbook, Third Edition, Joseph D. Bronzino The Circuits and Filters Handbook, Second Edition, Wai-Kai Chen The Communications Handbook, Second Edition, Jerry Gibson