1、Designation: E 948 09Standard Test Method forElectrical Performance of Photovoltaic Cells UsingReference Cells Under Simulated Sunlight1This standard is issued under the fixed designation E 948; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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 test method covers the determination of the elec-trical performance of a photovoltaic cel
3、l under simulatedsunlight by means of a calibrated reference cell procedure.1.2 Electrical performance measurements are reported withrespect to a select set of standard reporting conditions (SRC)(see Table 1) or to user-specified conditions.1.2.1 The SRC or user-specified conditions include the cell
4、temperature, the total irradiance, and the reference spectralirradiance distribution.1.3 This test method is applicable only to photovoltaic cellswith a linear response over the range of interest.1.4 The cell parameters determined by this test methodapply only at the time of test, and imply no past
5、or futureperformance level.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 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
6、 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:2E 490 Standard Solar Constant and Zero Air Mass SolarSpectral Irradiance TablesE 491 Practice for Solar Simulation for Th
7、ermal BalanceTesting of SpacecraftE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 772 Terminology Relating to Solar Energy ConversionE 927 Specification for Solar Simulation for PhotovoltaicTestingE 973 Test Method for Determination of the Spectral
8、Mis-match Parameter Between a Photovoltaic Device and aPhotovoltaic Reference CellE 1125 Test Method for Calibration of Primary Non-Concentrator Terrestrial Photovoltaic Reference Cells Us-ing a Tabular SpectrumE 1328 Terminology Relating to Photovoltaic Solar EnergyConversionE 1362 Test Method for
9、Calibration of Non-ConcentratorPhotovoltaic Secondary Reference CellsG 173 Tables for Reference Solar Spectral Irradiances:Direct Normal and Hemispherical on 37 Tilted Surface3. Terminology3.1 DefinitionsDefinitions of terms in this test methodmay be found in Terminology E 772 and Terminology E 1328
10、.3.2 Definitions of Terms Specific to This Standard:3.2.1 cell temperature, C, nthe temperature of the semi-conductor junction of a photovoltaic cell.3.2.2 junction temperature, nsynonym for cell tempera-ture.3.2.3 light source, na source of radiant energy used forcell performance measurements that
11、simulates natural sunlight.3.3 Symbols:3.3.1 The following symbols and units are used in this testmethod:Acell area, m2artemperature coefficient of reference cell, C1Ccalibration constant of reference cell, Am2W1Eirradiance, Wm2Eostandard reporting irradiance, Wm2hefficiency, %FFfill factor, %1This
12、test method 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 April 1, 2009. Published May 2009. Originallyapproved in 1993.
13、 Last previous edition approved in 2005 as E 948 05a.2For 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.TABLE 1
14、Standard Reporting ConditionsReference Spectral IrradianceDistributionTotal Irradiance(Wm2)Temperature(C)Tables G 173 Direct Normal 1000 25Tables G 173 Hemispherical 1000 25Tables E 490 1366.1 251Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit
15、ed States.Icurrent, AIocurrent with respect to SRC, AIrreference cell short-circuit current, AIscshort-circuit current, AMspectral mismatch parameterPmmaximum power, WRsseries resistance, VTtemperature, CTostandard reporting temperature, CTrtemperature of reference cell, CVvoltage, VVovoltage with r
16、espect to SRC, VVocopen-circuit voltage, V4. Summary of Test Method4.1 The performance test of a photovoltaic cell consists ofmeasuring the electrical current versus voltage (I-V) charac-teristic of the cell while illuminated by a suitable light source.4.2 Acalibrated photovoltaic reference cell (se
17、e 6.1) is usedto determine the total irradiance during the test and to accountfor the spectral distribution of the light source.4.3 Simulated sunlight is used as the light source for theelectrical performance measurement, and solar simulationrequirements are defined in Specification E 927 (terrestri
18、alapplications) and Practice E 491 (space applications).4.4 The data from the measurements are corrected to stan-dard reporting conditions, or to optional user-specified report-ing conditions.The standard reporting conditions are defined inTable 1.34.4.1 Measurement error caused by deviations of the
19、 irradi-ance conditions from the SRC is corrected using the totalirradiance measured with the reference cell and the spectralmismatch parameter, M, which is determined in accordancewith Test Method E 973.4.4.2 Measurement error caused by deviation of the celltemperature from the SRC is minimized by
20、maintaining the celltemperature close to the required value (see 7.6.1).5. Significance and Use5.1 It is the intent of this test method to provide a recog-nized method for testing and reporting the electrical perfor-mance of photovoltaic cells.5.2 The test results may be used for comparison of cells
21、among a group of similar cells or to compare diverse designs,such as different manufacturers products. Repeated measure-ments of the same cell may be used to study changes in deviceperformance.5.3 This test method determines the electrical performanceof a cell based upon the output power at a single
22、 instant oftime. It does not provide for integrating the output power overa given period of time and conditions to predict an energyoutput.5.4 This test method requires a reference cell calibrated withrespect to an appropriate reference spectral irradiance distribu-tion, such as Tables E 490,orG 173
23、. It is the responsibility ofthe user to determine which reference spectral irradiancedistribution is appropriate for a particular application.6. Apparatus6.1 Photovoltaic Reference CellA calibrated referencecell is used to determine the total irradiance during theelectrical performance measurement.
24、6.1.1 Reference cells may be calibrated in accordance withTest Methods E 1125 or E 1362, as is appropriate for aparticular application.NOTE 1No reference cell calibration standards presently exist forspace applications, although procedures such as high-altitude balloon andlow-earth orbit flights are
25、 being used to calibrate such reference cells.6.1.2 A current measurement instrument (see 6.3) shall beused to determine the Iscof the reference cell under the lightsource.6.2 Test FixtureBoth the cell to be tested and the refer-ence cell are mounted in a fixture that meets the followingrequirements
26、.6.2.1 The test fixture shall ensure a uniform lateral tempera-ture distribution to within 60.5C during the performancemeasurement.6.2.2 The test fixture shall include a provision for maintain-ing a constant cell temperature for both the reference cell andthe cell to be tested (see 7.6.1).NOTE 2When
27、 using pulsed or shuttered light sources, it is possiblethat the cell temperature will increase upon initial illumination, even whenthe cell temperature is controlled.6.2.3 The test fixture, when placed in the simulated sunlight,shall ensure that the field-of-view of both the reference cell andthe c
28、ell to be tested are identical.NOTE 3Some solar simulators may have significant amounts ofirradiation from oblique or non-perpendicular angles to the test plane. Inthese cases, it is important that the cell to be tested and the reference cellhave similar reflectance and cosine-response characteristi
29、cs.6.2.4 A four-terminal connection (also known as a Kelvinconnection, see Fig. 1) from the cell to be tested to the I-Vmeasurement instrumentation (see 6.3-6.5) shall be used.3Wehrli, C., Extraterrestrial Solar Spectrum, Publ. No. 615, Physikalisch-Meteorologisches Observatorium and World Radiation
30、 Center, Davos Switzerland,1985. FIG. 1 I-V Measurement SchematicE9480926.3 Current Measurement EquipmentThe instrument orinstruments used to measure the cell current and the Iscof thereference cell shall have a resolution of at least 0.02 % of themaximum current encountered, and shall have a total
31、error ofless than 0.1 % of the maximum current encountered.6.4 Voltage Measurement EquipmentThe instrument orinstruments used to measure the cell voltage shall have aresolution of at least 0.02 % of the maximum voltage encoun-tered, and shall have a total error of less than 0.1 % of themaximum volta
32、ge encountered.6.5 Variable LoadAn electronic load, such as a variableresistor or a programmable power supply, used to operate thecell to be tested at different points along its I-V characteristic.6.5.1 The variable load shall be capable of operating the cellto be tested at an I-V point where the vo
33、ltage is within 1 % ofVocin the power-producing quadrant.6.5.2 The variable load shall be capable of operating the cellto be tested at an I-V point where the current is within 1 % ofIscin the power-producing quadrant.6.5.3 The variable load must allow an output power (theproduct of cell current and
34、cell voltage) resolution of at least0.2 % of the maximum power.6.5.4 The electrical response time of the variable load mustbe fast enough to sweep the range of I-V operating pointsduring the measurement period.NOTE 4It is possible that the response time of cell to be tested maylimit how fast the ran
35、ge of I-V operating points can be swept, especiallywhen pulsed solar simulators are used. For these cases, it may benecessary to measure smaller ranges of the I-V curve using multiplemeasurements to obtain the entire range required.6.6 Light SourceRequirements of the solar simulationused to illumina
36、te the cell to be tested are defined in Specifi-cation E 927 (terrestrial applications) and Practice E 491(space applications).6.7 Temperature Measurement EquipmentThe instrumentor instruments used to measure the cell temperature of both thereference cell and the cell to be tested shall have a resol
37、utionof at least 0.1C, and shall have a total error of less than 61Cof reading.6.7.1 Sensors used for the temperature measurement(s)must be located in a position that minimizes any temperaturegradients between the sensor and the photovoltaic devicejunction.7. Procedure7.1 Determine the series resist
38、ance, Rs, of the cell to bemeasured. An acceptable method is described in Annex A1.7.1.1 If the total irradiance during the performance mea-surement as measured by the reference cell is within 62%ofthe standard reporting total irradiance, the series resistance isnot needed.7.2 Measure the cell area,
39、 A, using the definition in Termi-nology E 1328.7.3 Determine the spectral mismatch parameter, M, usingTest Method E 973.7.4 Mount the cell to be tested and the reference cell in thetest fixture.NOTE 5Any nonuniformity of irradiance (see Specification E 927)between the locations of the reference cel
40、l and the cell to be tested willintroduce a bias error in the measured cell performance.7.4.1 If a pulsed or shuttered light source is used, expose thetest fixture to the source illumination.7.5 Measure the temperature of the reference cell, Tr.7.5.1 If the temporal instability of the light source (
41、asdefined in Specification E 927) is less than 0.1 %, the totalirradiance may be determined with the reference cell prior tothe performance measurement. In this case, use the followingsteps to measure the total irradiance.7.5.1.1 Measure the short-circuit current of the referencecell, Ir.7.5.1.2 Rep
42、lace the reference cell with the cell to be tested.7.6 Measure the temperature of the cell under test.7.6.1 The measured temperature of the cell under test shallbe within 61C of the applicable SRC.7.7 Measure the I-V characteristic of the cell under test bychanging the operating point with the varia
43、ble load so that theprovisions of 6.5.1-6.5.3 are met. At each operating point onthe I-V characteristic, measure the cell voltage, cell current,and the Iscof the reference cell.7.7.1 If the provision of 7.5.1 is met, it is not necessary tomeasure the Iscof the reference cell at the same time that th
44、eI-V characteristic is measured.7.8 Measure the temperature of the cell under test to verifythat the provision in 7.6.1 is met.8. Calculation8.1 Obtain the temperature coefficient of the reference cellfrom the calibration report.8.2 Correct each I-V data pair using the following equa-tions:Io5IEoCMI
45、r1 2arTo2 Tr!#(1)Vo5 V 2 RsIo2 I! (2)NOTE 6If the provision of 7.1.1 is met, it is not necessary to correctthe cell voltage using the series resistance.8.3 Determine the short-circuit current using one of thefollowing procedures:8.3.1 If an IoVodata pair exists where Vois within60.005Voc,Iofrom this
46、 pair may be considered to be theshort-circuit current.8.3.2 If the condition in 8.3.1 is not met, calculate theshort-circuit current from the two IoVodata pairs where Vois closest to zero using linear interpolation.8.4 Determine the open-circuit voltage using one of thefollowing procedures:8.4.1 If
47、 an IoVodata pair exists where Iois within60.001Isc,Vofrom this pair may be considered to be theopen-circuit voltage.8.4.2 If the condition in 8.4.1 is not met, calculate theopen-circuit voltage from the two IoVodata pairs where Ioisclosest to zero using linear interpolation.8.5 Calculate the cell o
48、utput power P for each data pair fromthe product of Ioand Vo, and determine the maximum powerpoint Pmalong with the corresponding Vmfrom the P vs. Votable. Because of random fluctuations and the probability thatone point in the tabular I-V data will not be exactly on theE948093maximum power point, i
49、t is recommended that the followingprocedure be used to calculate the maximum power point,especially for devices with fill factors greater than 80 %.8.5.1 Perform a fourth-order polynomial least-squares fit tothe P vs. Vodata that are within the following limits. Theselimits are guidelines that have been found to be useful for thisprocedure and need not be followed precisely. This results in apolynomial representation of P as a function of Vo.0.75Im#Io#1.15Im(3)0.75Vm#Vo#1.15Vm(4)8.5.2 Calculate the derivative polynomial o
