IEC 62817:2014/AMD1:2017

IEC 62817 ®
Edition 1.0 2017-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
A MENDMENT 1
AM ENDEMENT 1
Photovoltaic systems – Design qualification of solar trackers

Systèmes photovoltaïques – Qualification de conception des suiveurs solaires

IEC 62817:2014-08/AMD1:2017-07(en-fr)

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IEC 62817 ®
Edition 1.0 2017-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
A MENDMENT 1
AM ENDEMENT 1
Photovoltaic systems – Design qualification of solar trackers

Systèmes photovoltaïques – Qualification de conception des suiveurs solaires

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-4475-3

– 2 – IEC 62817:2014/AMD1:2017
© IEC 2017
FOREWORD
This amendment has been prepared by IEC technical committee 82: Solar photovoltaic energy
systems.
The text of this amendment is based on the following documents:
CDV Report on voting
82/1018/CDV 82/1097/RVC
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
_____________
7.3.3 Calibration of pointing error measurement tool
Add the following to 7.3.3
A procedure for calibration of pointing error measurement tool does not exist in this or any
other IEC document. It is recommended that the pointing error measurement tool be
calibrated at least once per year per the following:
Outdoor tracker pointing error sensor calibration procedure:
Apparatus and measurement requirements: Device for mounting and orienting the pointing
error sensor (typically a solar tracker but other devices suffice), data acquisition system
capable of measuring outputs of the pointing error sensor, recording the timestamp that is
accurate to the true time within 2 s, visual verification of no clouds impinging the view of the
sun during the entire measurement period (including thin cirrus clouds) or verification during
the entire measurement period that the DNI varies no more than 2 % from maximum to
minimum values recorded.
a) Determine the measurement range for which the calibration is desired. The maximum
measurement range is the field of view of the sensor under calibration but a smaller
measurement range can be used as applicable to the calibration.
b) Assume that ±1° is the measurement range for the calibration. Mount the sensor on the
alignment device and adjust the position of the device so that the sensor is pointing
approximately 1° (or other determined measurement range) ahead of the sun’s movement
path in both axes of orientation. If the alignment device is a solar tracker, this means
aligning the sensor with the solar tracker’s mounting plane and then moving the solar

© IEC 2017
tracker 1° ahead of the sun’s position (in both axes). Fix the position of the alignment
device (this means stopping movement of a solar tracker).
c) Start the data acquisition, recording both the timestamp and outputs of the pointing error
sensor at a 10 s or shorter interval. Record data for the time period it takes for the sun to
walk through the desired measurement range for each axis under calibration (for this
example this is 2° of sun movement for the ±1° measurement range). The time necessary
for the sun to move the desired range depends on the latitude/longitude of the
measurement location, the day of the year, and the time of day. Input this information into
the Solpos or SPA algorithms for determining sun location during the test period (freely
available at http://www.nrel.gov/midc/srrl_bms/).
d) After completion of the data acquisition period, using the timestamp from the dataset,
merge sun position data from the Solpos or SPA algorithms for both solar zenith and solar
azimuth angle into the measured data set. Determine the solar zenith and azimuth
positions for which the outputs of each axis of the pointing sensor correspond to zero
pointing error (For most sensor designs this corresponds to a zero voltage output signal).
Data points can be interpolated between to find the zero pointing error position. These
azimuth and zenith positions should be recorded as the “fixed azimuth” and “fixed zenith”
pointing position of the sensor for the calibration period.
e) Calculate the true azimuth and zenith pointing error for every data point in the data set as
follows:
True Zenith Pointing Error = Zenith – Zenith
Solpos FixedPosition
True Azimuth Pointing Error = (Azimuth – Azimuth )·Sine(Zenith )
Solpos FixedPosition Solpos
Note that the True Azimuth Pointing Error is an approximation which is only valid as
(Azimuth – Azimuth ) approaches 0. For cases where values of
Solpos FixedPosition
– Azimuth ) are less than 5 and where Zenith is more than
(Azimuth
Solpos FixedPosition Solpos
3, the error of the approximation is less than 0,0001°. Generally speaking achieving the
conditions for such low error is achievable.
f) Plot the True Zenith Pointing Error against the corresponding sensor output for the zenith
axis. The sensor manufacturer shall establish the details of the final output signal to be
used for the calibration plots as some sensors have a single signal while others that have
multiple signals that together are used for determining the measured pointing error. Plot
the True Azimuth Pointing Error against the corresponding sensor output for the azimuth
axis. For both plots apply a linear fit to the data set. Report the fit coefficients and the
standard deviation of the slope. The slope is the calibration factor between the output
signal and the pointing error in degrees. Note that the calibration procedure presented
here is a relative measurement of the sensor’s ability to represent a change in pointing
error with a change in its output and does not prove absolute pointing error. Also, the
calibration procedure is described in terms of azimuth and zenith as this relates to the
Solpos and SPA algorithms but the calibration coefficients apply to the two generic axes of
the sensor that can be mounted on various tracker configurations.
8.4.4 Torsional stiffness, mechanical drift, drive torque, and backlash testing
8.4.4.2 Procedure, paragraph preceding Option a)
In this paragraph, replace the last three sentences with the following text:
Assuming the tracker has a horizontal stow position, the stow moment coefficient derived from
third-party wind tunnel or field test data shall be for the tracker in a position 3° from
horizontal. This deviation from horizontal accounts for potential deviations from stow to the
true horizontal position and for minor variations in ground slope in otherwise flat areas. Wind
tunnel testing shall demonstrate establishment of a representative atmospheric boundary
layer which includes turbulence that accounts for the normal deviations in wind flow from
purely horizontal. Wind tunnel data shall be collected at the 3° tilt position, unless the said
tracker cannot achieve this position. In such an event, the wind tunnel testing and derivation
of the moment coefficient shall be performed at the nearest position to horizontal that the
tracker can achieve.
– 4 – IEC 62817:2014/AMD1:2017
© IEC 2017
NOTE The tilt position for extreme moment testing was changed from 10° to 3°, as the original 10° was deemed
overly conservative. Appropriate wind tunnel atmospheric boundary layers already account for deviations from
horizontal wind flows which the 10° was originally claimed to take into account.
8.5 Environmental testing
8.5.2 Procedure
Replace the existing item a) with the following new item a):
a) Temperature cycle (no humidity added to the air) where inclusion of dust is recommended
as follows but is not required: at least 40 cycles and 480 h shall be completed. The
maximum temperature shall be 55 °C and the minimum temperature shall be –20 °C. If the
operational temperature range specified in Table 1 (see 6.12.1) indicates the tracker can
operate outside –20 °C to 55 °C, then the temperature range of this test shall be expanded
to coincide with the specified values. In other words, –20 °C to 55 °C can be considered
the minimum test conditions, but more extreme values shall be applied to align with the
specification sheet. The cycle shall dwell for at least 5 min, but not more than 15 min, at
±3 °C of the maximum and minimum temperatures per average surface temperature
measurements at three distinct points on the drive train. The temp
...