nificantintheoverallpictureandattemptstodeterminethosetechnicalmeasuresthatcanreduceusageandsavemoney.Meanwhile,lookingforidealenergysourcesisalsoveryimportanttosolveenergycrisis.Therecipeforanidealenergysourcecallsforonethatisunlimitedinsupply,widelyavailable,andinexpensive;itshouldnotaddtotheearth'stotalheatburdenorproducechemicalairandwaterpollutants.Solarenergyfulfillsallofthesecriteria.Solarenergydoesnotaddexcessheattothatwhichmustberadiatedfromtheearth.Onaglobalbasis,utilizationofonlyasmallfractionofsolarenergyreachingtheearthcouldprovideforallenergyneeds.Solarenergyisunlimitedinsupply,butitsexploitationandutilizationarelimitedowingtothelimitationoftechnologyandconditions.Solarenergyutilizationneedsanenormousamountofland,andthereareeconomicandenvironmentalproblemsrelatedtotheuseofevenafractionofthisamountoflandforsolarenergycollection.Certainly,manyresid采集一组数据。