1、Designation: E2939 13Standard 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
2、 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 photovo
3、ltaic 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 pro
4、cedure 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 a
5、re 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
6、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. Termin
7、ology3.1 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 specif
8、ic 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 aparticula
9、r 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. Com
10、pare with data collection periodin Test Method E2848.3.2.5 plane-of-array irradiance, POA, nsee solarirradiance, hemispherical in Terminology E772.3.2.6 simulated power output, photovoltaic system,nphotovoltaic system power output derived from meteoro-logical data and a performance model.3.2.7 time
11、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 thecapaci
12、ty 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.
13、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 Other Alternative Energy Sources and is the direct responsibility ofSubcommittee E44
14、.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 inform
15、ation, 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 19428-2
16、959. United States1consisting of plane-of-array irradiance, ambient airtemperature, 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.
17、 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 guidance for sel
18、ecting the report-ing conditions needed for Test Method E2848. This practicealso provides a procedure for determining the expected capac-ity of a photovoltaic system.4.4 The procedure for determining expected capacity con-sists of the following steps:4.4.1 Procure meteorological data that will be re
19、presenta-tive4of the POA irradiance, ambient air temperature, and windspeed conditions during the data collection period.4.4.1.1 This is best accomplished by using meteorologicaldata that is of the same time of year and same weatherconditions seen or expected to be seen during E2848.4.4.2 Procure or
20、 develop a performance model representa-tive of the photovoltaic system,4.4.3 Substitute the meteorological data into the perfor-mance model to calculate the instantaneous, simulated poweroutput of the photovoltaic system, and4.4.4 Use the data set to calculate the expected capacityaccording to Sect
21、ion 9 of Test Method E2848.4.5 The expected capacity can then be compared with thecapacity measured during an acceptance test of a photovoltaicsystem, if both capacities are determined from the samereporting conditions.5. Significance and Use5.1 This practice can be used to determine an expectedcapa
22、city for an existing or a proposed photovoltaic system in aparticular location during a specified period of time (see datacollection period in Test Method E2848).5.2 The expected capacity calculated in accordance withthis practice can be compared with the capacity measuredaccording to Test Method E2
23、848 when the RC are the same.5.3 The comparison of expected capacity and measuredcapacity can be used as a criterion for plant acceptance.5.4 The user of this practice must select the performancesimulation period over which the reporting conditions andexpected capacity will be derived. Seasonal vari
24、ations willlikely cause both of these to change with differing performancesimulation periods.5.5 When this practice is used in conjunction with TestMethod E2848, the performance simulation period and the datacollection period must agree. If they do not agree, the com-parison between expected and mea
25、sured capacity will not bemeaningful.5.6 Historical or measured5plane-of-array irradiance, am-bient air temperature and wind speed data can be used to selectreporting conditions and calculate expected capacity. If histori-cal data are used, the data collection period should match thetime period of t
26、he measured data in terms of season and length.5.7 The simulated power output that is used to calculate theexpected capacity should be derived from a performance modeldesigned to represent the photovoltaic system which will bereported per Test Method E2848.6. Meteorological Data Procurement6.1 Selec
27、t a meteorological data set that includes at aminimum, plane-of-array irradiance, ambient temperature andwind speed for a minimum of 5 contiguous days. This datasetwill be used to calculate reporting conditions and expectedcapacity. Another disadvantage is that historical data is rarelymeasured in t
28、he plan-of-array. Therefore, the data will have tobe transposed into the plane-of-array which will have errorswhen compared to actual measurements. Historical or mea-sured meteorological data may be used to calculate reportingconditions and expected capacity. Both have advantages anddisadvantages.6.
29、2 The advantage of using historical data to calculatereporting conditions is that the reporting conditions and asso-ciated expected capacity can be calculated in advance of theconstruction of a project. This is beneficial when this practiceand Test Method E2848 are used for the purpose of acceptance
30、testing. The disadvantage of using historical data for calculat-ing reporting conditions is that actual meteorological condi-tions during the test may differ from historical conditions. Thismay increase uncertainty in the comparison of expectedcapacity to capacity measured per Test Method E2848.6.3
31、Generally, it is recommended to use historical data toselect reporting conditions, as this will allow the reportingconditions and expected capacity to be calculated in advance ofthe capacity measurement per Test Method E2848.6.4 When applicable, the averaging interval used in thispractice should be
32、the same as the averaging interval used inTest Method E2848.7. Performance Model Procurement7.1 Select a performance model that at a minimum convertsPOA irradiance, ambient temperature and wind speed intosimulated power output.7.2 Use the selected performance model and the selectedmeteorological dat
33、a to derive simulated power output.8. Reference Conditions Determination8.1 As applicable, conduct data filtering of the meteorologi-cal data and the simulated power output per 9.1 of Test MethodE2848.4In the event that data is not available that will be representative for the system,the user of the
34、 practice may translate the data so that it is representative. Alltranslations should use industry standards when possible and when not possibleindustry best practices. All translations of meteorological data shall be documentedand included in the report.5Here measured data refers to data measured d
35、uring the Test Method E2848 testprocedure.E2939 1328.2 After filtering, the dataset must represent no less than750 total minutes that span at least three days. For example, anaveraging interval of fifteen minutes requires a minimum of 50data points. In the event the data points represent less than 7
36、50minutes after filtering, extend the test period until 750 minutesof data points exist after filtering.8.3 If historical meteorological data were selected, use POAirradiance, ambient temperature, and wind speed during thesame time of year as the expected test period associated withTest Method E2848
37、 to calculate the reporting irradiance,reporting ambient temperature and reporting wind speed. In theevent that the test period is unknown at the time of RCselection, generate monthly tables of reporting irradiances,reporting ambient temperatures and reporting wind speeds. Thepurpose of using season
38、al tables of reporting conditions is toaccount for seasonal biases in the reporting conditions;therefore, the number of seasonal reporting conditions mayvary by climate and location. In areas with strong seasonality,more granular seasonal tables are recommended. In areas withlittle seasonality, less
39、 granular tables may suffice. At aminimum, four and at a maximum twelve sets of reportingconditions are recommended.8.3.1 Compare POA irradiance, ambient temperature andwind speed of the filtered data that will be used to calculatereporting conditions to the filtered POA irradiance, ambienttemperatu
40、re and wind speed measured during the Test MethodE2848 test. If applicable, report differences between theconditions.8.3.2 The comparison is applicable only if this practice willbe used for an operational plant. This step can occur after theselection of reporting conditions and the calculation of ex
41、-pected capacity in the event that the measured data is notavailable when the reference conditions are selected and theexpected capacity calculated.8.4 Calculate the irradiance value that exceeds 60 % of thefiltered irradiance data. This is the reporting plane of arrayirradiance.8.5 Calculate the ar
42、ithmetic mean ambient temperature ofthe filtered data. This is the reporting ambient temperature.8.6 Calculate the arithmetic mean wind speed of the filtereddata. This is the reporting wind speed.9. Expected Capacity Calculation9.1 Use the filtered POA irradiance, filtered ambienttemperature, filter
43、ed wind speed, and filtered simulated powerdata to calculate the regression coefficients specified in 4.2 ofTest Method E2848.9.2 Calculate the power using the regression coefficientsfrom 10.1 and the reporting conditions from 9 of this practiceper 4.3 of Test Method E2848.9.3 This power is the expe
44、cted capacity.10. Report10.1 The user ultimately determines the amount of informa-tion to be reported. At a minimum the user shall report thefollowing:10.2 Description of performance model including:10.2.1 Input parameters,10.2.2 Software used for performance modeling, and10.2.3 Modeled system locat
45、ion.10.3 Resource dataset selected for determining reportingconditions and expected capacity:10.3.1 Source of the data,10.3.2 If the data is measured or modeled,10.3.3 Location at which the resource data was measured ormodeled,10.3.4 If the data is historical or measured.610.3.4.1 If the data is his
46、torical, the time period the histori-cal data spans, and10.3.5 If applicable, differences in POA irradiance, ambienttemperature, and wind speed between data used for TestMethod E2848 and this practice. These differences will bereported pre- and post-filtering.10.4 Filtering criteria used.10.5 Calcul
47、ated reporting conditions or table of reportingconditions.10.6 Calculated expected capacity or table of expectedcapacities.10.7 Calculated regression coefficients or tables of regres-sion coefficients, a1,a2,a3and a4.10.7.1 The mean and standard deviation of the residuals forthe data used to derive
48、the regression(s) shall be reported as anindicator of the quality of the regression(s).10.7.2 All simulated system performance data, POA irradi-ance data, ambient temperate data and wind speed data shall beincluded in this report as an appendix in a tabulated textformat.11. Keywords11.1 performance;
49、 photovoltaics; reporting; systems6Here measured data refers to data measured during the E2848 test.E2939 133ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not r
