spectral modelling poster - tÜv rheinland · this poster contains results of high-precision indoor...

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This poster contains results of high-precision indoor and outdoor measurements of different PV module technologies performed at the headquarters of TÜVRheinland, Cologne. Modules based on CdTe, CI(G)S, a-Si, a-Si/µ-Si, a-Si/a-Si and c-Si (mono and poly) semiconductors were analyzed nondestructivelyaccording to their spectral response and technology specific differences are pointed out. After the indoor characterization the modules were exposed outdoorfor one year, steadily measuring the maximum power point PMPP and the I/V-curves with the corresponding solar spectrum. With this data volume it ispossible to describe the spectral conditions at the test-site in Cologne using the APE-Method. In a next step the influence on the module performance and theenergy yield of the different technologies are analyzed. The photo current is calculated theoretically by the integral of spectral response data and spectralmeasurements and compared to temperature and irradiance corrected real outdoor measurements.

Depending on the position of the sun related to the module and theatmosphere the spectral distribution of solar irradiation can be shifted intoblue or red wavelength areas. Some technologies can benefit while othersmay be disadvantaged depending on their spectral response. In what wayand why these spectral shifts happen in the course of a day and theseason and what influence they have on the energy yield of a certaintechnology are described in the following.

Markus Schweiger, Ulrike Jahn, Werner Herrmann TÜV Rheinland Energie und Umwelt GmbH, Am Grauen Stein, 51105 Cologne, Germany

Tel.: +49 221 806-5585, E-Mail: Markus.Schweiger@de.tuv.com

RESULTS

CONCLUSIONS

SPECTRAL ANALYSIS OF VARIOUS THIN FILM MODULES USING HIGH PRECISION SPECTRAL RESPONSE DATA AND

SOLAR SPECTRAL IRRADIANCE DATA

Figure 1 Non-destructive measurement of the spectral response (SR) of a triple-junction module with the test equipment atTÜV Rheinland, Cologne

Spectral response of different PV module technologies

Characterizing solar spectrum with the average photon energy (APE)

Influence of spectrum on performance and yield

Since 2013 TÜV Rheinland runs extensive energy yieldmeasurements at five different locations all over the world.Requests can be sent to the authors.

� Significant differences in SR-Signal of CIGS and a-Si specimens

� APE-Method appropriate method to describe solar spectrum

� Automatable procedure to correct T, G and MM implemented

� Sinus-shaped performance fluctuation of a-Si because of spectrum

� Spectrum not significant for energy yield of c-Si and most CIGS

� Annual gains of +3% (some a-Si) and +1% (CdTe) calculated in 11/12

INTRODUCTION

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� The SR-equipment is suitablefor all common moduledesigns (Fig. 1)

� Step-size 1nm for single-,double- and triple-junctionspecimens possible

� Large spread of the spectralresponse for different moduletechnologies (Fig. 2)

� Also large technology internalspreads for a-Si and CIGS(Fig. 3 + 4)

� The spectral mismatch (MM)and the theoretical photocurrent can be calculated toimprove PMax determinationand outdoor monitoring

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� Spectrum < 1.65 eV � red

� Spectrum > 1.65 eV � blue

� Spectrum = 1.65 eV � STC

� Winter red spectrum (Fig. 5 + 8)

Calculated Measured

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AM1,5g Summer (21.08.2010) Fall (10.10.2010) Winter (29.01.2011) Spring (19.04.2011)

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Figure 5 Solar spectral irradiance drift for cloudless days insummer (blue), spring (green), fall (yellow) and winter (red)for modules mounted facing south and 35° tilted in Cologne

Figure 9 Correcting spectral effects of an a-Si specimenFigure 8 Seasonal variations of APE-values and averageAPE-value per month

Figure 6 Dependency of ISC on spectral changes,calculated with formula, normalized to ISC,STC at 1.65 eV

Figure 7 Dependency of ISC on spectral changes, measured(T, G corrected), normalized to ISC,STC at 1.65 eV

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Figure 2 Rel. spectral response signal of different PV-module technologies in comparison with IEC 60904-3spectrum

Figure 3 + 4 Rel. spectral response signal of different CIGSand a-Si modules, illustrating significant differences withinthe same thin-film technology

� Results of calculated and measured ISC (APE) almost similar (Fig. 6+7)

� Dependency of a-Si/µ-Si on spectrum screened out as combination ofa-Si behavior for APE < 1.65eV and µ-Si behavior for APE > 1.65eV�significant losses because of current mismatch expected

� Almost no dependency of c-Si and most CIGS on spectrum

� Strong dependency of a-Si and small dependency of CdTe on spectrum

� The seasonal average spectrum was calculated to 1.68 eV in 2011/12.� Small energy yield gains of max. +3% (some a-Si) and +1% (CdTe).