solar spectral irradiance measurements R. Galleano, W. Zaaiman, D. - - PowerPoint PPT Presentation

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Fifth spectroradiometer comparison for improved solar spectral irradiance measurements

• R. Galleano, W. Zaaiman, D. Alonso Alvarez, A. Minuto, N. Ferretti, R. Fucci, M.

Marzoli, L. Manni, M. Halwachs, M. Friederichs, F. Plag, D. Friedrich, E. Haverkamp

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Rationale The wider portfolio

• f

today’s available PV technologies with diversified spectral responsivities makes the knowledge of the light source spectrum a key parameter in calibrations Energy yield estimations/predictions in PV may improve with more accurate long term solar spectral data at specific locations Needs for an evidence-based quality-control system as required by ISO 17025 standard

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Main scopes Comparison of calibrated spectroradiometers and secondary calibration for broadband radiometers Exchange of “good laboratory practices” on solar spectral measurements to improve accuracy Assessing equivalence level for solar spectral irradiance measurements among laboratories Reduce terrestrial and space solar cell calibration uncertainty through the dissemination of reference measurements directly traceable to the SI units

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Location: ‘Instituto Nacional de Técnica Aeroespacial’ Madrid (E) from 18th to 22nd May 2015 Twentytwo people from fourteen Institutions Ten spectroradiometer systems (Wv ~300-1100 nm

• r ~300-1700 nm)

60+ broadband radiometers: cavity, pyrheliometer, pyranometer, PV reference and ISO-type cells

People and instruments involved

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Some issues and challenges Use

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accurate solar tracker for mounting instruments reducing angular response issues Diversified spectroradiometer technologies including mono- and poly- chromator based systems with spectral bandwidth from 0.5 to 4 nm and integration time from few milliseconds to five minutes Needs of irradiance stability ≤1% during the longest acquisition time assessed by cavity radiometers Cavity radiometers as link to SI units for irradiance

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Preliminary results presented here

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Daily wavelength-by-wavelength differences

• 2.0%
• 1.0%

0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0% Lab B Lab C Lab D Lab E Lab F Lab G Lab H Lab I Lab L

19/05 average difference 19/05 average

• std. dev.

20/05 average difference 20/05 average

• std. dev.

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Different analysis approach: Spectra shape comparison using 𝐹𝑜 numbers (ISO/IEC 17043 on conformity assessment). Applying the ISO/IEC 60904-9, the percentage of total irradiance in six wavelength intervals is computed for the spectra under test, 𝑁𝑀𝑏𝑐𝑗 , and compared with the reference one, 𝑁𝑠𝑓𝑔. The observed deviations are coherent with declared uncertainty if -1<𝐹𝑜<1 𝐹𝑜 = 𝑁𝑀𝑏𝑐𝑗 − 𝑁𝑠𝑓𝑔 𝑉𝑀𝑏𝑐𝑗 ∗ 𝑁𝑀𝑏𝑐𝑗 2 + 𝑉𝑠𝑓𝑔 ∗ 𝑁𝑠𝑓𝑔 2

𝑉𝑀𝑏𝑐𝑗 = 5% and 𝑉𝑠𝑓𝑔 = 3% (k=2)

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Laboratory Wv-by-Wv mean difference

Lab B 1.9% Lab C 4.2% Lab D 1.1% Lab E

• 0.8%

Lab F 1.0% Lab G

• 0.2%

Lab H 4.3% Lab I 0.2% Lab L 0.3%

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Nice, but ... What all this stuff means for PV people? Practical example: Impact of using simultaneously acquired spectra from different spectroradiometers for the calibration

• f a reference PV cell using a cavity radiometer as

the reference device. Spectral mismatch (MM) factor calculation.

11 0.00005 0.0001 0.00015 0.0002 300 400 500 600 700 800 900 1000 1100 1200

Arbitrary unit

Wavelength nm

Data for MM calculation Reference cell: SRdut Reference AM1.5 spectrum: Gref Measured spectra: Gmeas

𝑁𝑁 = 𝑇𝑆𝑠𝑓𝑔 𝜇 𝐻𝑠𝑓𝑔 𝜇 𝑒𝜇 𝑇𝑆𝑠𝑓𝑔 𝜇 𝐻𝑛𝑓𝑏𝑡 𝜇 𝑒𝜇 𝑇𝑆𝑒𝑣𝑢 𝜇 𝐻𝑛𝑓𝑏𝑡 𝜇 𝑒𝜇 𝑇𝑆𝑒𝑣𝑢 𝜇 𝐻𝑠𝑓𝑔 𝜇 𝑒𝜇

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Mismatch values computed at four different time

• f the day using spectra by four ‘best

performing’ spectroradiometers

Acquisition time 10:27 12:08 12:18 14:47 MM Lab A 1.003 1.019 1.018 1.018 MM Lab E 1.007 1.021 1.022 1.019 MM Lab F 1.003 1.020 1.020 1.019 MM Lab H 1.004 1.012 1.012 1.011 MM pk-pk difference 0.004 0.009 0.010 0.008

1% difference in mismatch values translates in 1% difference in cell short circuit current calibration value

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Conclusions:  1-day wavelength-by-wavelegth difference relative to peak irradiance within ±3.1%  Performance statistics analysis shows results

• f seven participants consistent with their

uncertainty values  Spectral mismatch pk-pk differences ≤1% using spectra simultaneously acquired by four

• spectroradiometers. This figure directly

impact the calibration of primary PV detectors  From first comparison edition MM difference reduced from almost 3% to 1% or better

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