IEC TS 62989 pdf free download
IEC TS 62989 pdf free download.Primary optics for concentrator photovoltaic systems.
5.2.1.4 Test specimens
5.2.1.4.1 Specimen size and geometry
Specimens shall consist of placard or discs composed of the POE material(s). The radius of curvature for the specimens should be sufficiently large that the width of the transmitted (or reflected) beam remains smaller than the aperture of the integrating sphere.
The specimens shall contain an examination region free from visible flaws including:
scratches, pits, sink marks, bubbles, or other imperfections. The examination region shall be at least 50 % larger in diameter than the measurement area of the test instrument. A spot size of 1 cm x 1 cm is common in many commercial spectrophotometer instruments. Use of specimens at least 2 to 3 times this size will improve uniformity (resulting from fabrication) and handling (during measurement). The size (length and width) should, however, be adequate to allow the specimen to fit inside the test instrument.
The nominal thickness of the specimens shall be equal to the thickness intended for use in CPV modules. When a laminate or composite material is used, the thickness of each of the component layers shall be the same as intended for use in a CPV POE.
Specimens should be prepared according to the manufacturer’s specification and using a process as similar as possible to the method used in the intended manufacturing process.
The thickness of the test specimen shall be measured after its preparation. The thickness shall be taken as the average of three measurements obtained at different locations on the test region of the specimen.
Both surfaces of the specimens shall not be faceted or intentionally textured.
5.2.1.4.2 Number of specimens
A minimum of 3 replicates shall be used for the determination of the transmittance or in weathering studies. Optical characteristics, including transmittance, Yl, and the UV cut-off wavelength shall be subsequently calculated using the average of the three separate specimens, with the range of the measurements indicated to identify their variability.
5.2.1.4.3 Conditioning of specimens
Specimens used for the purpose of datasheet reporting shall be maintained at (23 ± 2) °C,
(50 ± 10) % relative humidity for at least 24 h, or until the mass has stabilized to ± 10 %
(which can take on the order of 300 h for PMMA, if not force-dried), as recommended in
ISO 291 Class 2, prior to optical measurement.
5.2.1.5 Measurement procedure
5.2.1.5.1 Specimen preparation
Prior to measurement, specimens should be free of dust, grease, or other contaminants. The specimens and instrument should be in thermal equilibrium prior to measurement.
5.2.1.5.2 Instrument calibration (baseline measurements)
Allow the instrument lamp to adequately equilibrate after it has been lighted, observing the typical warm-up period, for example 15 mm or as recommended by the instrument manufacturer. Perform the correction scan(s) to compensate for the instrument baseline signal.
The 100 % transmittance baseline measurement should be performed in air, with no specimen present. The 100 % reflectance baseline measurement should be performed using a calibrated standard similar to the reflector specimens, for example silvered glass for silvered glass reflectors or Spectralon for general purposes. The 0 % transmittance baseline measurement should also be performed, if possible. Periodic measurement of the baseline is recommended to minimize instrument drift and ensure the measured values are accurate. The instrument drift occurring over an extended measurement session may be instrument specific.
5.2.1.5.3 Specimen measurements
Perform the transmittance measurements for the test specimens over the wavelength range of at least 280 nm to 2 500 nm using a 1 nm increment.
Linear interpolation to a 1 nm increment may be used when only a coarser measurement increment (maximum of 5 nm) is available. The error associated with a coarser increment may be more influential at shorter wavelengths (where Yl and the UV cut-off wavelength are determined) than at longer wavelengths (where only the solar-weighted transmittance is affected). When applied, the use of linear interpolation should be noted in the test report. The spectral bandwidth should be less than or equal to the increment of the measurement, i.e. 1 nmor5nm.IEC TS 62989 pdf download.
