ASTM_E_2939_-_13.pdf

Designation:E293913Standard Practice forDetermining Reporting Conditions and Expected Capacityfor Photovoltaic Non-Concentrator Systems1This standard is issued under the fixed designation E2939;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice provides procedures for determining theexpected capacity of a specific photovoltaic system in aspecific geographical location that is in operation under naturalsunlight during a specified period of time.The expectedcapacity is intended for comparison with the measured capacitydetermined by Test Method E2848.1.2 This practice is intended for use with Test MethodE2848 as a procedure to select appropriate reporting conditions(RC),including solar irradiance in the plane of the modules,ambient temperature,and wind speed,needed for the photo-voltaic system capacity measurement.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E772 Terminology of Solar Energy ConversionE2848 Test Method for Reporting Photovoltaic Non-Concentrator System Performance2.2 IEEE Standards:3IEEE 1547-2003 Standard for Interconnecting DistributedResources with Electric Power Systems3.Terminology3.1 Definitions of terms used in this practice may be foundin Terminology E772,IEEE 1547-2003,and Test MethodE2848.3.2 Definitions:3.2.1 expected capacity,photovoltaic system,nthe pre-dicted power rating that is derived from meteorological dataand a performance model that describes a specific PV system ina specific location and time period.3.2.2 measured capacity,photovolaic system,nthe outputpower of a photovoltaic system measured according to TestMethod E2848.3.2.3 performance model,photovoltaic system,na com-puter model which,at a minimum,simulates the operation of aparticular photovoltaic system using plane-of-array irradiance,ambient temperature and wind speed data as inputs to calculatethe instantaneous,simulated power output.3.2.4 performance simulation period,photovoltaic system,nthe period of time over which a single expected capacityprediction is performed.Compare with data collection periodin Test Method E2848.3.2.5 plane-of-arrayirradiance,POA,nseesolarirradiance,hemispherical in Terminology E772.3.2.6 simulatedpoweroutput,photovoltaicsystem,nphotovoltaic system power output derived from meteoro-logical data and a performance model.3.2.7 time resolution,meteorological data,nthe timeinterval between individual meteorological data points that hasa maximum averaging interval of 1 h,used to calculate both thereporting conditions and the expected capacity.4.Summary of Practice4.1 Test Method E2848 provides a procedure to measure thecapacity of a photovoltaic system.The procedure involves amultiple linear regression of output power as a function ofplane-of-array irradiance,ambient air temperature,and windspeed data collected during the data collection period,which isa relatively short time period,typically between 3 and 30 days.Using the regression results,the expected capacity(in watts)isthen calculated by substitution of a set of reporting conditions1This practice is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and OtherAlternative Energy Sources and is the direct responsibility ofSubcommittee E44.09 on Photovoltaic Electric Power Conversion.Current edition approved Sept.1,2013.Published September 2013.DOI:10.1520/E2939-132For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from Institute of Electrical and Electronics Engineers,Inc.(IEEE),445 Hoes Ln.,Piscataway,NJ 08854,http:/www.ieee.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 consistingofplane-of-arrayirradiance,ambientairtemperature,and wind speed appropriate for the system undertest into the regression equation.4.2 Although Test Method E2848 states that its procedure issuitable for acceptance testing of newly installed photovoltaicsystems(i.e.acceptance testing),it provides only generalguidance for the selection of the reporting conditions and noguidance for predicting expected capacity prior to test.Boththe reporting conditions and the expected capacity are neces-sary for acceptance testing.4.3 This practice provides