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Role of Distributed Generation in Reinforcing the Critical Electric Power Infrastructure

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IEEE2001WMPanel;

RoleofDistributedGenerationinReinforcingtheCriticalElectricPower

Infrastructure.

Title:MicrogridsPanelist;BobLasseter

IntroductionEnvironmentallyfriendlyrenewableenergytechnologiessuchasphotovoltaicsandclewefficient,fossil-fielstechnologiessuchasmicro-turbinesandfbelcellsareamongnewgeneratingsystemsdrivingthedemandfordistributedgenerationofelectricity.If

combinedheatandpoweratresident~industrialplantsorcommercialbuildingcanbe

achievedtheefficienciescanbehigherthanconventionalcentralgenerationplants.The

smallnessofthesenewdistributedgenerationalongwiththelowvoltagesattheinterface

createanewclassofproblemswhichrequiresinnovativeapproachestomanagingand

operatingthedistributedresources.Onesuchconceptisthemicrogrid.

EmergingGenerationTechnologies

Thetrendsintechnologypointstowardsmallness,underthe500kWlevel.Anexcellentexamplearethesmallgasfiredmicro-turbinesinthe25-100kWrangethatcanbemass

producedatlowcost.Theyaredesignedtocombinethereliabfityofonboardcommercialaircraflgeneratorswiththelowcostofautomotiveturbochargers.These

systemsarehighspeedturbines(50,000-90,000rpm)withairfoilbearings.Theyaresmallandusepowerelectronictointerfiwewiththeload.ExamplesincludeHoneywell’s

75-kWTurbogenerator,AllisorI/GE.50-kWgeneratorandCapstone’s30kWsystem.

Fuelcellsarealsowellsuitedfordistributedgenerationapplications.Theyofferhigh

efficiencyandlowemissions,buttoday’scostsarehigh.Phosphoricacidcellare

commerciallyavailableinthe200kWrange,whilesolidoxideandmoltencarbonatecellareinapre-commercialstageofdevelopment.InOctober1997theU.S.Departof

EnergyandArthurD.Littleunveiledthe“first-everon-boardgasolinepoweredfielcell

fortheautomobile”.Thepossibilityofusinggasolineasafbelforcellshasresultedinamajordevelopmenteffortbytheautomotivecompanies.Thisworkisfocusedtowardsthepolymerelectrolytemembrane(J?EM)fiielcells.

In1997BallardGenerationSystemsformedastrategicallianceswithDaimler-ChryslerandFordtodevelopthenextgenerationofefficientandcleanenginesfortheworld’svehiclesusingtheBallard’sPEMfhelcell.Theseenginesareexpectedtomeettheperformanceandrangebetweenrefielingrequirementsoftransportationvehiclesataprojectedfuelcellcostof$200perkW.Thistogetherwithmuchhigherefficiencyand

withoutthesignificantpollutingemissionsassociatedwiththeinternalcombustion

engineareexpectedtoresultinfielcellscapturingemergingmarkets.ManyotherleadinginternationalautomobdecompaniesaremakingmajorinvestmentsinfielcellsincludingGeneralMotors,Hond~Nis~Volkswage~Volvo,andMatsushitaElectric.

0-7803-6674-3/00/$10.00 (C) 2000 IEEE1440-7803-6674-3/00/$10.00 (C) 2000 IEEE0-7803-6672-7/01/$10.00 (C) 2001 IEEE146

Iffhelcellsfortranspirationbecomearealitytheywillalsoprovideastationarypower

sourceunderthe100kWrangeataverycompetitiveprice.

Mixedfhelcellandmicro-turbinesystemswillalsobeavailableasdistributed

generation.InajointDOEWestinghouseprojectasolidoxidefuelcellhasbeen

combmedwithagasturbinecreatingacombinedcyclepowerplant.Ithasexpected

electricalefficiencyofgreaterthan70percentwithlowandandvirtuallyzero.Theexpectedpowerlevelsrangefrom250-kWto2.5-MW

Distributedresourcesincludemorethansmallgeneratorsandfbelcells.Storage

technologiessuchasbatteries,ultracapacitorsandflyWheelplayanimportantrole.

Combiningstoragewithmicro-sourcesprovidepeakpowerandride-throughcapabilitiesduringdisturbances.Storagesystemsarefiumoreefficientthanfiveyearsago.Flywheelsystemscandeliver700-kWfor5secondswhile28-cellultracapacitorscanprovideupto12.5kWforafewseconds.

Micro-sourceIssuesThesetechnologieshaveverydflerentissuesthannormallyfoundintraditionalpower

sources.Forexampletheareappliedveryclosetothecustomersloadatvoltageof480

voltsorless,requirepowerelectronicsanddifferentmethodsofcontrolanddispatch.All

ofthesesenergytechnologiesprovideadcoutputwhichrequirespowerelectronicsto

interfacewiththepowernetworkanditsloads.Inmostcasestheconversionwillbe

petiormedusingavoltagesourceconverterwithapossibilityofphasewidthmodulation

toprovidef~controlofvoltagemagnitude.

Powerelectronicinterfacesintroducesnewcontrolissuesandnewpossibfities.Asystem

withclustersofmicro-generatorsandstoragecouldbedesignedtooperateinbothanislandmodeandconnectedtothepowergrid.Onelargeclassofproblemsarerelatedthe

fhctthatmicro-turbmesandfbelcellhaveslowresponseandareinertia-less.Itmustberememberedthatthecurrentpowersystemshavestorageingenerators’inertia.Whena

newloadcomesonlinetheinitialenergybalanceissatisfiedbythesystem’sinertia.Thisresultsinaslightreductioninsystemfrequency.Asystemwithclustersofmicro-

generatorscouldbedesignedtooperateinanislandmodeprovidesomeformofstoragetoprovidetheinitialenergybalance.

ThecontrolofinvertersusedtosupplypowertoanACsysteminad~tributedenvironmentshouldbebasedoninformationavailablelocallyattheinverter.Inasystemwithmanymicro-sources,communicationofinformationbetweensystemsisimpractical.

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英语教研活动听课记录(3篇)

英语教研活动听课记录(3篇)

第1篇

Date: March 15, 2023

Subject: English Language Teaching

Classroom: Grade 8, Class 3

Teacher: Ms. Liu

Observer: Mr. Zhang

Introduction:

The purpose of this English research and development activity is to

observe and evaluate the teaching methods and strategies employed by Ms.

Liu in her Grade 8 English class. The focus of this observation is to

assess the effectiveness of her approach in engaging students, promoting

language skills, and fostering critical thinking.

Observation Details:

I. Introduction to the Lesson (5 minutes)

- Activity: Ms. Liu began the lesson by greeting the students and

reviewing the previous day's vocabulary. She used a simple question-and-answer session to ensure that students were familiar with the new words

introduced.

- Teaching Strategy: Ms. Liu utilized a warm-up activity to create a

5篇关于公平正义的英文文章

5篇关于公平正义的英文文章

Article 1: The Importance of Justice and Fairness in Society

In the fabric of any healthy society, justice and fairness serve as the

fundamental threads that hold it together. Without these

principles, the social fabric begins to unravel, leading to distrust,

instability, and ultimately, disharmony. Therefore, understanding

and upholding justice and fairness is crucial for the progress and

well-being of any community.

Justice is often defined as the fair and impartial treatment of all

individuals, regardless of their background, status, or beliefs. It

ensures that everyone is subject to the same rules and that no one

is discriminated against or favored based on personal biases. In a

just society, the law applies equally to all, and decisions are made

objectively, without prejudice.

Fairness, on the other hand, relates to the equitable distribution of

屈服线理论

屈服线理论

8 Yield Line Theory

8.1 The essentials

Yield Line Design is a well-founded method of designing reinforced concrete slabs, and

similar types of elements. It uses Yield Line Theory to investigate failure mechanisms at

the ultimate limit state. The theory is based on the principle that:

work done in yield lines rotating = work done in loads moving

Yield Line Design is easy to grasp but there are several fundamental principles that need to

be understood. Yield Line Design is a plastic method: it is different from ‘normal’

elastic methods.

8.1 .1 A short history of Yield Line Theory

Yield Line Theory as we know it today was pioneered in the 1940s by the Danish engineer

and researcher K W Johansen.

As early as 1922, the Russian, A Ingerslev presented a paper to the Institution of

Structural Engineers in London on the collapse modes of rectangular slabs. Authors such

参加志愿者活动的收获与感悟英语作文

参加志愿者活动的收获与感悟英语作文

参加志愿者活动的收获与感悟英语作文

全文共3篇示例，供读者参考

篇1

The Rewards of Volunteering: A Journey of Growth and

Fulfillment

As a student, the pursuit of knowledge and personal growth

extends far beyond the confines of textbooks and classrooms. It

is a holistic journey that encompasses various facets of life,

including the invaluable experience of volunteering. Through my

involvement in various volunteer activities, I have embarked on a

transformative odyssey, one that has bestowed upon me a

profound sense of purpose, deepened my understanding of the

world around me, and instilled within me a renewed appreciation

for the power of collective action.

The decision to volunteer was not born out of mere

obligation or compulsion; rather, it stemmed from a genuine

desire to contribute to something greater than myself. The allure