Solar simulators—beyond Class A
of more sophisticated (and likely more Figure 6. It is apparent that there is no intervals (400-500 nm and 900-1100 nm,
expensive) filter designs without significant change in spectrum over the duration of a respectively). These results clearly show
increase in total cost. The net result of this single long pulse. virtually no change in spectrum during the
new design is a spectrum that falls within As well as providing good short-term useful lamp life of 100,000 flashes.
±10% of AM1.5G, well beyond Class A. temporal stability, it is highly desirable to
Not only are there needs for spatial have a stable spectrum over time periods Summary and conclusions
uniformity and high accuracy of spectrum, corresponding to the useful lifetime of Newer and more advanced PV module
but it is also necessary to provide temporal the flash lamps. Illustrated in Figure 7 are designs have started to increase the
stability of spectrum. Using our PASS results of spectral measurements over a demands on spectral accuracy, spectral
spectrometer that permits selection of the period corresponding to 100,000 lamp uniformity, and spectral stability of solar
temporal capture window, we were able flashes. During this period we monitored simulators. Current spectral standards
to measure spectra at the start of the SLP the irradiance fractions in all wavelength developed by ASTM and IEC may not be
light flash and at the end of the flash. intervals. Shown in the figure are the adequate to meet some of these needs.
Results of this measurement appear in results for the lower and upper wavelength Described in this paper are results for
continued on page 41
Figure 4. Spectral output measurement results obtained at 1-sun intensity from a Figure 5. Spectral measurement results near the center of a Spire SLP simula-
Spire 3500SLP long pulse simulator. Irradiance fraction data from 96 test loca- tor that employs a new optical filter geometric configuration. Measurements in
tions distributed over the entire test plane are shown for each of the six wavelength all wavelength intervals fall on or within ±10% of AM1.5G (the red region) in
intervals (bins) from 400 to 1100 nm. The blue region corresponds to a Class contrast to the normal ±25% of Class A (blue region).
A spectrum (±25% about AM1.5G). The red region corresponds to a tighter
specification of ±10%.
Figure 6. Spectral stability during a single 80 ms duration light pulse. The black Figure 7. Long-term stability of a Spire 3500SLP simulator. Each lamp pulse was
circles show the spectrum for each of the six wavelength intervals near the start of approximately 100 ms in duration and pulse repetition rate was approximately 2/
the pulse (10 to 20 ms portion); the black crosses show the spectrum at the end of min. Shown are the short-circuit current for a 75-Watt test module placed on the
the pulse (70 to 80 ms portion). No change in spectrum is detected. simulator surface and the fractional amounts of irradiance in the 400-500 and
900-1100 nm wavelength intervals (bins). No significant changes in any of the
parameters occurred during the rated 100,000 flash lifetime of the xenon lamp.
26 – Global Solar Technology – October/September 2009
www.globalsolartechnology.com
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