ASTM E2848-13(2023)
(Test Method)Standard Test Method for Reporting Photovoltaic Non-Concentrator System Performance
Standard Test Method for Reporting Photovoltaic Non-Concentrator System Performance
SIGNIFICANCE AND USE
5.1 Because there are a number of choices in this test method that depend on different applications and system configurations, it is the responsibility of the user of this test method to specify the details and protocol of an individual system power measurement prior to the beginning of a measurement.
5.2 Unlike device-level measurements that report performance at a fixed device temperature of 25 °C, such as Test Methods E1036, this test method uses regression to a reference ambient air temperature.
5.2.1 System power values calculated using this test method are therefore much more indicative of the power a system actually produces compared with reporting performance at a relatively cold device temperature such as 25 °C.
5.2.2 Using ambient temperature reduces the complexity of the data acquisition and analysis by avoiding the issues associated with defining and measuring the device temperature of an entire photovoltaic system.
5.2.3 The user of this test method must select the time period over which system data are collected, and the averaging interval for the data collection within the constraints of 8.3.
5.2.4 It is assumed that the system performance does not degrade or change during the data collection time period. This assumption influences the selection of the data collection period because system performance can have seasonal variations.
5.3 The irradiance shall be measured in the plane of the modules under test. If multiple planes exist (particularly in the case of rolling terrain), then the plane or planes in which irradiance measurement will occur must be reported with the test results. In the case where this test method is to be used for acceptance testing of a photovoltaic system or reporting of photovoltaic system performance for contractual purposes, the plane or planes in which irradiance measurement will occur must be agreed upon by the parties to the test prior to the start of the test.
Note 1: In general, the irradiance measur...
SCOPE
1.1 This test method provides measurement and analysis procedures for determining the capacity of a specific photovoltaic system built in a particular place and in operation under natural sunlight.
1.2 This test method is used for the following purposes:
1.2.1 Acceptance testing of newly installed photovoltaic systems,
1.2.2 Reporting of dc or ac system performance, and
1.2.3 Monitoring of photovoltaic system performance.
1.3 This test method should not be used for:
1.3.1 Testing of individual photovoltaic modules for comparison to nameplate power ratings,
1.3.2 Testing of individual photovoltaic modules or systems for comparison to other photovoltaic modules or systems, and
1.3.3 Testing of photovoltaic systems for the purpose of comparing the performance of photovoltaic systems located in different places.
1.4 In this test method, photovoltaic system power is reported with respect to a set of reporting conditions (RC) including solar irradiance in the plane of the modules, ambient temperature, and wind speed (see Section 6). Measurements under a variety of reporting conditions are allowed to facilitate testing and comparison of results.
1.5 This test method assumes that the solar cell temperature is directly influenced by ambient temperature and wind speed; if not the regression results may be less meaningful.
1.6 The capacity measured according to this test method should not be used to make representations about the energy generation capabilities of the system.
1.7 This test method is not applicable to concentrator photovoltaic systems; as an alternative, Test Method E2527 should be considered for such systems.
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user...
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2848 − 13 (Reapproved 2023) An American National Standard
Standard Test Method for
Reporting Photovoltaic Non-Concentrator System
Performance
This standard is issued under the fixed designation E2848; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 This test method provides measurement and analysis
standard.
procedures for determining the capacity of a specific photovol-
1.9 This standard does not purport to address all of the
taic system built in a particular place and in operation under
safety concerns, if any, associated with its use. It is the
natural sunlight.
responsibility of the user of this standard to establish appro-
1.2 This test method is used for the following purposes:
priate safety, health, and environmental practices and deter-
1.2.1 Acceptance testing of newly installed photovoltaic
mine the applicability of regulatory limitations prior to use.
systems,
1.10 This international standard was developed in accor-
1.2.2 Reporting of dc or ac system performance, and
dance with internationally recognized principles on standard-
1.2.3 Monitoring of photovoltaic system performance.
ization established in the Decision on Principles for the
1.3 This test method should not be used for:
Development of International Standards, Guides and Recom-
1.3.1 Testing of individual photovoltaic modules for com-
mendations issued by the World Trade Organization Technical
parison to nameplate power ratings,
Barriers to Trade (TBT) Committee.
1.3.2 Testing of individual photovoltaic modules or systems
2. Referenced Documents
for comparison to other photovoltaic modules or systems, and
1.3.3 Testing of photovoltaic systems for the purpose of
2.1 ASTM Standards:
comparing the performance of photovoltaic systems located in
D6176 Practice for Measuring Surface Atmospheric Tem-
different places.
perature with Electrical Resistance Temperature Sensors
E772 Terminology of Solar Energy Conversion
1.4 In this test method, photovoltaic system power is
E824 Test Method for Transfer of Calibration From Refer-
reported with respect to a set of reporting conditions (RC)
ence to Field Radiometers
including solar irradiance in the plane of the modules, ambient
E927 Classification for Solar Simulators for Electrical Per-
temperature, and wind speed (see Section 6). Measurements
formance Testing of Photovoltaic Devices
under a variety of reporting conditions are allowed to facilitate
E948 Test Method for Electrical Performance of Photovol-
testing and comparison of results.
taic Cells Using Reference Cells Under Simulated Sun-
1.5 This test method assumes that the solar cell temperature
light
is directly influenced by ambient temperature and wind speed;
E973 Test Method for Determination of the Spectral Mis-
if not the regression results may be less meaningful.
match Parameter Between a Photovoltaic Device and a
Photovoltaic Reference Cell
1.6 The capacity measured according to this test method
should not be used to make representations about the energy E1036 Test Methods for Electrical Performance of Noncon-
centrator Terrestrial Photovoltaic Modules and Arrays
generation capabilities of the system.
Using Reference Cells
1.7 This test method is not applicable to concentrator
E1040 Specification for Physical Characteristics of Noncon-
photovoltaic systems; as an alternative, Test Method E2527
centrator Terrestrial Photovoltaic Reference Cells
should be considered for such systems.
E1125 Test Method for Calibration of Primary Non-
Concentrator Terrestrial Photovoltaic Reference Cells Us-
ing a Tabular Spectrum
This test method is under the jurisdiction of ASTM Committee E44 on Solar,
Geothermal and Other Alternative Energy Sources and is the direct responsibility of
Subcommittee E44.09 on Photovoltaic Electric Power Conversion. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2023. Published August 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2011. Last previous edition approved in 2018 as E2848 – 13 (2018). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E2848-13R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2848 − 13 (2023)
E1362 Test Methods for Calibration of Non-Concentrator 3.2.5 sampling interval, n—the elapsed time between scans
Photovoltaic Non-Primary Reference Cells of the sensors used to measure power, irradiance, ambient
E2527 Test Method for Electrical Performance of Concen- temperature, and wind speed. Individual data points used for
trator Terrestrial Photovoltaic Modules and Systems Un- the performance test are averages of the values recorded in
der Natural Sunlight these scans. There are multiple sampling intervals in each
G138 Test Method for Calibration of a Spectroradiometer averaging interval.
Using a Standard Source of Irradiance
3.2.6 utility grid, n—see electric power system in IEEE
G167 Test Method for Calibration of a Pyranometer Using a
1547-2003.
Pyrheliometer
3.3 Symbols: The following symbols and units are used in
G173 Tables for Reference Solar Spectral Irradiances: Direct
this test method:
Normal and Hemispherical on 37° Tilted Surface
−1
3.3.1 α—reference cell I temperature coefficient, °C
G183 Practice for Field Use of Pyranometers, Pyrheliom- SC
eters and UV Radiometers
3.3.2 a , a , a , a —linear regression coefficients, arbitrary
1 2 3 4
2.2 IEEE Standards:
3.3.3 a, b, c, d—spectral mismatch factor calibration
IEEE 1526-2003 Recommended Practice for Testing the
constants, arbitrary
Performance of Stand-Alone Photovoltaic Systems
2 −1
3.3.4 C—reference cell calibration constant, Am W
IEEE 1547-2003 Standard for Interconnecting Distributed
Resources with Electric Power Systems
3.3.5 C —reference cell calibration constant at SRC,
o
2 −1
Am W
2.3 International Standards Organization Standards:
ISO/IEC Guide 98-1:2009 Uncertainty of measurement—
3.3.6 E—plane-of-array irradiance, W/m
Part 1: Introduction to the expression of uncertainty in
3.3.7 E —irradiance at SRC, plane-of-array, W/m
o
measurement
ISO/IEC Guide 98-3:2008 Uncertainty of measurement— 3.3.8 E (λ)—reference spectral irradiance distribution,
o
−2
−1
Part 3: Guide to the expression of uncertainty in measure- Wm nm
ment (GUM:1995) 2
3.3.9 E —RC rating irradiance, plane-of-array, W/m
RC
2.4 World Meteorological Organization (WMO) Standard:
−2
3.3.10 E (λ)—spectral irradiance distribution at RC, Wm
RC
WMO-No. 8 Guide to Meteorological Instruments and
−1
nm
Methods of Observation, Seventh Ed., 2008
3.3.11 E (λ)—spectral irradiance distribution, test light
T
−2 −1
source, Wm nm
3. Terminology
3.3.12 F—fractional error in short-circuit current, dimen-
3.1 Definitions—Definitions of terms used in this test
sionless
method may be found in Terminology E772, IEEE 1547-2003,
and ISO/IEC Guide 98-1:2009 and ISO/IEC Guide 98-3:2008.
3.3.13 I —short-circuit current, A
SC
3.2 Definitions of Terms Specific to This Standard:
3.3.14 M—spectral mismatch factor, dimensionless
3.2.1 averaging interval, n—the time interval over which
3.3.15 p—p-value, dimensionless quantity used to deter-
data are averaged to obtain one data point. The performance
mine the significance of an individual regression coefficient to
test uses these averaged data.
the overall rating result
3.2.2 data collection period, n—the period of time defined
3.3.16 P—photovoltaic system power, ac or dc, W
by the user of this test method during which system output
power, irradiance, ambient temperature, and wind speed are
3.3.17 P —photovoltaic system power at RC, ac or dc, W
RC
measured and recorded for the purposes of a single regression
3.3.18 RC—reporting conditions
analysis.
3.3.19 R (λ)—reference cell spectral responsivity, A/W
R
3.2.3 plane-of-array irradiance, POA, n—see solar
irradiance, hemispherical in Tables G173. 3.3.20 R (λ)—test device spectral responsivity, A/W
T
3.2.4 reporting conditions, RC, n—an agreed-upon set of
3.3.21 SRC—standard reporting conditions
conditions including the plane-of-array irradiance, ambient
3.3.22 SE—standard error, W
temperature, and wind speed conditions to which photovoltaic
system performance are reported. The reporting conditions 3.3.23 T —ambient temperature, °C
a
must also state the type of radiometer used to measure the
3.3.24 T —RC rating temperature, °C
RC
plane-of-array irradiance. In the case where this test method is
3.3.25 U —expanded uncertainty with a 95 % coverage
to be used for acceptance testing of a photovoltaic system or
probability of photovoltaic system power at RC, W
reporting of photovoltaic system performance for contractual
purposes, RC, or the method that will be used to derive the RC,
3.3.26 λ—wavelength, nm
shall be stated in the contract or agreed upon in writing by the
3.3.27 v—wind speed, m/s
parties to the acceptance testing and reporting prior to the start
of the test. 3.3.28 v —RC rating wind speed, m/s
RC
E2848 − 13 (2023)
4. Summary of Test Method 5.3.1 The linear regression results will be most reliable
when the measured irradiance, ambient temperature, and wind
4.1 Photovoltaic system power, solar irradiance, ambient
speed data during the data collection period are distributed
temperature, and wind speed data are collected over a defined
around the reporting conditions. When this is not the case, the
period of time using a data acquisition system.
reported power will be an extrapolation to the reporting
4.2 Multiple linear regression is then used to fit the collected
conditions.
data to the performance equation (Eq 1) and thereby calculate
5.4 Accumulation of dirt (soiling) on the photovoltaic mod-
the regression coefficients a , a , a , and a .
1 2 3 4
ules can have a significant impact on the system rating. The
P 5 E a 1a · E1a · T 1a · v (1)
~ !
1 2 3 a 4
user of this test may want to eliminate or quantify the level of
4.3 Substitution of the RC values E , T , and v into Eq 1
soiling on the modules prior to conducting the test.
o o o
then gives the ac or dc power at the reporting conditions.
5.5 Repeated regression calculations on the same system to
P 5 E a 1a · E 1a · T 1a · v (2)
~ ! the same RC and using the same type of irradiance measure-
RC RC 1 2 RC 3 RC 4 RC
ment device over successive data collection periods can be
4.4 The collected input data and the performance at the
used to monitor performance changes as a function of time.
reporting conditions are then reported.
5.6 Capacity determinations are power measurements and
5. Significance and Use
are adequate to demonstrate system completeness. However, a
single capacity measurement does not provide sufficient infor-
5.1 Because there are a number of choices in this test
mation to project the energy generation potential of the system
method that depend on different applications and system
over time. Factors that may affect energy generation over time
configurations, it is the responsibility of the user of this test
include: module power degradation, inverter clipping and
method to specify the details and protocol of an individual
overloading, shading, backtracking, extreme orientations, and
system power measurement prior to the beginning of a mea-
filtering criteria.
surement.
5.2 Unlike device-level measurements that report perfor-
6. Reporting Conditions
mance at a fixed device temperature of 25 °C, such as Test
6.1 The user of this test method shall select appropriate RC.
Methods E1036, this test method uses regression to a reference
In the case where this test method is to be used for acceptance
ambient air temperature.
testing of a photovoltaic system or reporting of photovoltaic
5.2.1 System power values calculated using this test method
system performance for contractual purposes, the RC, or the
are therefore much more indicative of the power a system
method that will be used to derive the RC, must be agreed upon
actually produces compared with reporting performance at a
by the parties to the test.
relatively cold device temperature such as 25 °C.
6.1.1 Reporting conditions may be selected either on the
5.2.2 Using ambient temperature reduces the complexity of
basis of expected conditions or actual conditions during the
the data acquisition and analysis by avoiding the issues
data collection period. Choose RC irradiance and ambient air
associated with defining and measuring the device temperature
temperature values that are representative of the POA irradi-
of an entire photovoltaic system.
ance and ambient air temperature for the system location for a
5.2.3 The user of this test method must select the time
clear day in the data collection period. When the selection is
period over which system data are collected, and the averaging
based on expected conditions, irradiance can be evaluated from
interval for the data collection within the constraints of 8.3.
a year-long hourly data set of projected POA values calculated
5.2.4 It is assumed that the system performance does not
from historical data measured directly on the system site or at
degrade or change during the data collection time period. This
a nearby site. Ambient temperatures can be evaluated by a
assumption influences the selection of the data collection
review of historical data from the site or a nearby location.
period because system performance can have seasonal varia-
Reporting conditions should be chosen such that the system is
tions.
not subject to frequent shading, inverter clipping, or other
5.3 The irradiance shall be measured in the plane of the
nonlinear operation at or around the RC. For instance, in larger
modules under test. If multiple planes exist (particularly in the
photovoltaic systems, the ratio of installed DC capacity to AC
case of rolling terrain), then the plane or planes in which
inverter capacity may be such that the inverter limits the
irradiance measurement will occur must be reported with the
production of the modules under certain conditions. If this is
test results. In the case where this test method is to be used for
the case, care should be taken to choose a reference within the
acceptance test
...
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