1、Designation: E2939 13 (Reapproved 2018)Standard 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 adopti
2、on 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
3、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 Me
4、thodE2848 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 unit
5、s 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, health, and environmental practices and deter-mine the applic
6、ability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by th
7、e World Trade Organization TechnicalBarriers to Trade (TBT) Committee.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
8、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 meteorolo
9、gical 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 w
10、hich, 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 whi
11、ch a single expected capacityprediction is performed. Compare 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
12、 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 Te
13、st Method E2848 provides a procedure to measure thecapacity of a photovoltaic system. The procedure involves a1This practice is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and Other Alternative Energy Sources and is the direct responsibility ofSubcommittee E44.09 on Photovoltaic
14、 Electric Power Conversion.Current edition approved May 1, 2018. Published September 2013. Originallyapproved in 2013. Last previous edition approved in 2013 as E2939-13. DOI:10.1520/E2939-13R182For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at s
15、erviceastm.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
16、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Re
17、commendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1multiple 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
18、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 conditionsconsisting of plane-of-array irradiance, ambient airtemperature, and wind speed appropriate for the system undertest into the
19、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 capac
20、ity prior to test. Boththe reporting conditions and the expected capacity are neces-sary for acceptance testing.4.3 This practice provides guidance for selecting the report-ing conditions needed for Test Method E2848. This practicealso provides a procedure for determining the expected capac-ity of a
21、 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 representa-tive4of the POA irradiance, ambient air temperature, and windspeed conditions during the data collection period.4.4.1.1 This is best acc
22、omplished 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 develop a performance model representa-tive of the photovoltaic system,4.4.3 Substitute the meteorological data into the perfor-mance model to c
23、alculate the instantaneous, simulated poweroutput of the photovoltaic system, and4.4.4 Use the data set to calculate the expected capacityaccording to Section 9 of Test Method E2848.4.5 The expected capacity can then be compared with thecapacity measured during an acceptance test of a photovoltaicsy
24、stem, if both capacities are determined from the samereporting conditions.5. Significance and Use5.1 This practice can be used to determine an expectedcapacity for an existing or a proposed photovoltaic system in aparticular location during a specified period of time (see datacollection period in Te
25、st Method E2848).5.2 The expected capacity calculated in accordance withthis practice can be compared with the capacity measuredaccording to Test Method E2848 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
26、 user of this practice must select the performancesimulation period over which the reporting conditions andexpected capacity will be derived. Seasonal variations willlikely cause both of these to change with differing performancesimulation periods.5.5 When this practice is used in conjunction with T
27、estMethod E2848, the performance simulation period and the datacollection period must agree. If they do not agree, the com-parison between expected and measured capacity will not bemeaningful.5.6 Historical or measured5plane-of-array irradiance, am-bient air temperature and wind speed data can be us
28、ed to selectreporting conditions and calculate expected capacity. If histori-cal data are used, the data collection period should match thetime period of the measured data in terms of season and length.5.7 The simulated power output that is used to calculate theexpected capacity should be derived fr
29、om a performance modeldesigned to represent the photovoltaic system which will bereported per Test Method E2848.6. Meteorological Data Procurement6.1 Select a meteorological data set that includes at aminimum, plane-of-array irradiance, ambient temperature andwind speed for a minimum of 5 contiguous
30、 days. This datasetwill be used to calculate reporting conditions and expectedcapacity. Another disadvantage is that historical data is rarelymeasured in the plan-of-array. Therefore, the data will have tobe transposed into the plane-of-array which will have errorswhen compared to actual measurement
31、s. Historical or mea-sured meteorological data may be used to calculate reportingconditions and expected capacity. Both have advantages anddisadvantages.6.2 The advantage of using historical data to calculatereporting conditions is that the reporting conditions and asso-ciated expected capacity can
32、be calculated in advance of theconstruction of a project. This is beneficial when this practiceand Test Method E2848 are used for the purpose of acceptancetesting. The disadvantage of using historical data for calculat-ing reporting conditions is that actual meteorological condi-tions during the tes
33、t may differ from historical conditions. Thismay increase uncertainty in the comparison of expectedcapacity to capacity measured per Test Method E2848.6.3 Generally, it is recommended to use historical data toselect reporting conditions, as this will allow the reportingconditions and expected capaci
34、ty to be calculated in advance ofthe capacity measurement per Test Method E2848.6.4 When applicable, the averaging interval used in thispractice should be the same as the averaging interval used inTest Method E2848.7. Performance Model Procurement7.1 Select a performance model that at a minimum conv
35、ertsPOA irradiance, ambient temperature and wind speed intosimulated power output.4In the event that data is not available that will be representative for the system,the user of the practice may translate the data so that it is representative. Alltranslations should use industry standards when possi
36、ble 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 during the Test Method E2848 testprocedure.E2939 13 (2018)27.2 Use the selected performance model and the selectedmeteor
37、ological data 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 MethodE2848.8.2 After filtering, the dataset must represent no less than750 total minutes that span
38、 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 750minutes after filtering, extend the test period until 750 minutesof data points exist after filtering.8.3 If historical meteorological d
39、ata were selected, use POAirradiance, ambient temperature, and wind speed during thesame time of year as the expected test period associated withTest Method E2848 to calculate the reporting irradiance,reporting ambient temperature and reporting wind speed. In theevent that the test period is unknown
40、 at the time of RCselection, generate monthly tables of reporting irradiances,reporting ambient temperatures and reporting wind speeds. Thepurpose of using seasonal tables of reporting conditions is toaccount for seasonal biases in the reporting conditions;therefore, the number of seasonal reporting
41、 conditions mayvary by climate and location. In areas with strong seasonality,more granular seasonal tables are recommended. In areas withlittle seasonality, less granular tables may suffice. At aminimum, four and at a maximum twelve sets of reportingconditions are recommended.8.3.1 Compare POA irra
42、diance, ambient temperature andwind speed of the filtered data that will be used to calculatereporting conditions to the filtered POA irradiance, ambienttemperature and wind speed measured during the Test MethodE2848 test. If applicable, report differences between theconditions.8.3.2 The comparison
43、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-pected capacity in the event that the measured data is notavailable when the reference conditions are selected and theexpected capacity c
44、alculated.8.4 Calculate the irradiance value that exceeds 60 % of thefiltered irradiance data. This is the reporting plane of arrayirradiance.8.5 Calculate the arithmetic mean ambient temperature ofthe filtered data. This is the reporting ambient temperature.8.6 Calculate the arithmetic mean wind sp
45、eed of the filtereddata. This is the reporting wind speed.9. Expected Capacity Calculation9.1 Use the filtered POA irradiance, filtered ambienttemperature, filtered wind speed, and filtered simulated powerdata to calculate the regression coefficients specified in 4.2 ofTest Method E2848.9.2 Calculat
46、e 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 expected capacity.10. Report10.1 The user ultimately determines the amount of informa-tion to be reported. At a minimum the user shall report
47、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 location.10.3 Resource dataset selected for determining reportingconditions and expected capacity:10.3.1 Source of the data,10.3.2 If the data
48、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 historical, the time period the histori-cal data spans, and10.3.5 If applicable, differences in POA irradiance, ambienttemperature, and wind
49、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 Calculated 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 the regression(s) shall be reported as anindicator of the quality of the regression(s).10.7.2 All simulated system perfor
