ABSTRACT New generations of photovoltaics (PV) have demonstrated a significant cost-reduction wit... more ABSTRACT New generations of photovoltaics (PV) have demonstrated a significant cost-reduction with respect to c-Si wafer-based modules. Though second (thin-film) and third generation PV (high-intensity, low-cost) are already in the PV market, the preparation of standard procedures for their characterization is still ongoing. This work was developed by the author in order to extend some of the existing characterization techniques to a set of three different emerging technologies: multi-junction thin-film modules, concentrator PV cells and luminescent solar concentrators. An original method for the spectral response measurement of large area thin-film multijunction modules is presented in the first part: the method is validated with several examples. A basic theoretical approach is also presented to propose innovative explanations of measurement artefacts that are observed in the literature. In the second part of the thesis, the setup, characterization and classification of a high intensity pulsed solar simulator for concentrator PV cells is illustrated. A new procedure for the preparation of a set of filtered reference cells for the irradiance detection at high intensities is also presented, providing an original tool for the verification of the linearity of these devices towards irradiance, which is usually assumed in the literature. In the third part the performance characterization of high-efficiency luminescent solar concentrators is presented: a simple ray-tracing model and its experimental validation, the impact of backside diffusive reflector on the performance of this kind of devices are mainly highlighted. The work was developed in support of the activities of the European Solar Test Installation laboratory of the European Commission, a centre of reference for PV testing.
ABSTRACT Current-matching between junctions in a multi-junction photovoltaic device is fundamenta... more ABSTRACT Current-matching between junctions in a multi-junction photovoltaic device is fundamental for its performance prediction: the measurement of the spectral response of each junction provides a valuable information to optimize the device performance. Various aspects make spectral response measurements of such devices particularly challenging. In this work these aspects are analysed theoretically and guidelines to avoid their impact in the experimental practice are given.
ABSTRACT In this paper a new hybrid Model Output Statistics (MOS), named MOS cascade, is develope... more ABSTRACT In this paper a new hybrid Model Output Statistics (MOS), named MOS cascade, is developed to refine the day-ahead forecast of the global horizontal irradiance provided by the Weather Research and Forecast (WRF) model. The proposed approach is based on a sequence of two different MOS. The first, called MOSRH, is a new physically based algorithm, built to correct the treatment of humidity in the WRF radiation schemes. The second, called MOSNN, is based on artificial intelligence techniques and aims to correct the main systematic and learnable errors of the Numerical Weather Prediction output. The 1-day and 2-day forecast accuracies are analyzed via direct comparison with irradiance data measured in two sites, Rome and Lugano. The paper shows that a considerable reduction in error was achieved using MOSRH model and MOS cascade. The differences between the two sites are discussed in details. Finally, the results obtained are compared with the benchmark accuracy reached for the data available for the average climate in Southern Spain and Switzerland.
The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance T... more The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral ...
The large variety of photovoltaic (PV) technologies today available on the market makes the chara... more The large variety of photovoltaic (PV) technologies today available on the market makes the characterization of the spectral content of the used light sources a key parameter for calibration and energy yield estimation of PV devices. The use of pulsed, artificial light sources is spread worldwide but these solar simulators have the disadvantage of producing light beams with a spectral content rather different from the Air Mass 1.5 global (AM1.5G) standard spectrum, thus requiring a careful correction of the spectral mismatch between actual and standard spectral conditions. The spectral mismatch correction factor (SMM) may be difficult to apply in the PV module calibration process if reference and calibrating devices have different spectral responsivities and/or if the calibrating device is a multi-junction one. This paper describes the comparison results on the spectral measurements of two ESTI's pulsed solar simulators performed by teams from two ISO 17025 accredited PV calibra...
ABSTRACT Light Emitting Diodes (LEDs) have recently gained importance in the experimental practic... more ABSTRACT Light Emitting Diodes (LEDs) have recently gained importance in the experimental practice of photovoltaic (PV) devices. LEDs have already been proposed as the alternative to conventional xenon or halogen based solar simulators. Multi-junction PV devices use coloured LEDs in experimental tools as well: LEDs can transform a conventional solar simulator in a spectrally adjustable simulator for spectral characterization of multi-junction modules. Other useful applications include evaluating the dependence of the electrical parameters on the average photon energy and spectral responsivity measurements of multi-junction PV devices.
ABSTRACT In this work the authors show results of a measurement inter-comparison campaign that sa... more ABSTRACT In this work the authors show results of a measurement inter-comparison campaign that saw the cooperation of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI-ISAAC, indoor characterization), the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA, outdoor characterization) and the University of Cyprus (indoor and outdoor characterization). The measurement campaign is extremely useful to improve the know-how of the centres involved. Aside the well-known spectral mismatch effects, the importance of the "capacitive effect" is highlighted in this work, which arises when the tested high-efficiency CPV cell are characterized indoor on a pulsed solar simulator, depending on the duration of the pulse.
... rd EU PVSEC, Valencia, 552-555 (2008). 5. MJ Currie, JK Mapel, TD Heidel, S. Goffri and MA Ba... more ... rd EU PVSEC, Valencia, 552-555 (2008). 5. MJ Currie, JK Mapel, TD Heidel, S. Goffri and MA Baldo, Science 321, 226-228 (2008). ... & Solar Cells 93, 176-182 (2009). 7. LH Slooff, EE Bende, AR Burgers, T. Budel, M. Pravettoni, RP Kenny, ED Dunlop and A. Büchtemann, Phys. ...
ABSTRACT Performance testing of high-efficient, highly capacitive c-Si modules with pulsed solar... more ABSTRACT Performance testing of high-efficient, highly capacitive c-Si modules with pulsed solar simulators requires particular carefulness in order to avoid measurement artifacts. These devices in fact usually require a steady-state solar simulator or pulse durations longer than 100 ms. The aim of this work was to validate an alternative method for the testing of highly capacitive c-Si modules using a to-ms single pulse solar simulator. Our approach attempts to reconstruct a quasi steady-state IV curve of a highly-capacitive device during one single to-ms flash by applying customized voltage profiles -in place of a conventional V ramp -to the terminals of the device under test. The most promising results were obtained by using V profiles which we name "dragon-back" (DB) profiles. When compared to the reference IV measurement (obtained by using a multi-flash approach), the dragon-back V profile method provides excellent results with differences in the estimation of Pmax below ±0.5% (as well as of Isc, Voc, and FF). For the testing of highly-capacitive devices the method is accurate, fast (two flashes -possibly one -required), and cost-effective.
Progress in Photovoltaics Research and Applications
This paper describes the preliminary results of an intercomparison of spectroradiometers for glob... more This paper describes the preliminary results of an intercomparison of spectroradiometers for global (GNI) and direct normal incidence (DNI) irradiance in the visible (VIS) and near infrared (NIR) spectral regions together with an assessment of the impact these results may have on the calibration of triple-junction photovoltaic devices and on the relevant spectral mismatch calculation. The intercomparison was conducted by six European scientific laboratories and a Japanese industrial partner. Seven institutions and seven spectroradiometer systems, representing different technologies and manufacturers were involved, representing a good cross section of the todays' available instrumentation for solar spectrum measurements.
ABSTRACT New generations of photovoltaics (PV) have demonstrated a significant cost-reduction wit... more ABSTRACT New generations of photovoltaics (PV) have demonstrated a significant cost-reduction with respect to c-Si wafer-based modules. Though second (thin-film) and third generation PV (high-intensity, low-cost) are already in the PV market, the preparation of standard procedures for their characterization is still ongoing. This work was developed by the author in order to extend some of the existing characterization techniques to a set of three different emerging technologies: multi-junction thin-film modules, concentrator PV cells and luminescent solar concentrators. An original method for the spectral response measurement of large area thin-film multijunction modules is presented in the first part: the method is validated with several examples. A basic theoretical approach is also presented to propose innovative explanations of measurement artefacts that are observed in the literature. In the second part of the thesis, the setup, characterization and classification of a high intensity pulsed solar simulator for concentrator PV cells is illustrated. A new procedure for the preparation of a set of filtered reference cells for the irradiance detection at high intensities is also presented, providing an original tool for the verification of the linearity of these devices towards irradiance, which is usually assumed in the literature. In the third part the performance characterization of high-efficiency luminescent solar concentrators is presented: a simple ray-tracing model and its experimental validation, the impact of backside diffusive reflector on the performance of this kind of devices are mainly highlighted. The work was developed in support of the activities of the European Solar Test Installation laboratory of the European Commission, a centre of reference for PV testing.
ABSTRACT Current-matching between junctions in a multi-junction photovoltaic device is fundamenta... more ABSTRACT Current-matching between junctions in a multi-junction photovoltaic device is fundamental for its performance prediction: the measurement of the spectral response of each junction provides a valuable information to optimize the device performance. Various aspects make spectral response measurements of such devices particularly challenging. In this work these aspects are analysed theoretically and guidelines to avoid their impact in the experimental practice are given.
ABSTRACT In this paper a new hybrid Model Output Statistics (MOS), named MOS cascade, is develope... more ABSTRACT In this paper a new hybrid Model Output Statistics (MOS), named MOS cascade, is developed to refine the day-ahead forecast of the global horizontal irradiance provided by the Weather Research and Forecast (WRF) model. The proposed approach is based on a sequence of two different MOS. The first, called MOSRH, is a new physically based algorithm, built to correct the treatment of humidity in the WRF radiation schemes. The second, called MOSNN, is based on artificial intelligence techniques and aims to correct the main systematic and learnable errors of the Numerical Weather Prediction output. The 1-day and 2-day forecast accuracies are analyzed via direct comparison with irradiance data measured in two sites, Rome and Lugano. The paper shows that a considerable reduction in error was achieved using MOSRH model and MOS cascade. The differences between the two sites are discussed in details. Finally, the results obtained are compared with the benchmark accuracy reached for the data available for the average climate in Southern Spain and Switzerland.
The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance T... more The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral irradiance The paper reports on indoor spectral ...
The large variety of photovoltaic (PV) technologies today available on the market makes the chara... more The large variety of photovoltaic (PV) technologies today available on the market makes the characterization of the spectral content of the used light sources a key parameter for calibration and energy yield estimation of PV devices. The use of pulsed, artificial light sources is spread worldwide but these solar simulators have the disadvantage of producing light beams with a spectral content rather different from the Air Mass 1.5 global (AM1.5G) standard spectrum, thus requiring a careful correction of the spectral mismatch between actual and standard spectral conditions. The spectral mismatch correction factor (SMM) may be difficult to apply in the PV module calibration process if reference and calibrating devices have different spectral responsivities and/or if the calibrating device is a multi-junction one. This paper describes the comparison results on the spectral measurements of two ESTI's pulsed solar simulators performed by teams from two ISO 17025 accredited PV calibra...
ABSTRACT Light Emitting Diodes (LEDs) have recently gained importance in the experimental practic... more ABSTRACT Light Emitting Diodes (LEDs) have recently gained importance in the experimental practice of photovoltaic (PV) devices. LEDs have already been proposed as the alternative to conventional xenon or halogen based solar simulators. Multi-junction PV devices use coloured LEDs in experimental tools as well: LEDs can transform a conventional solar simulator in a spectrally adjustable simulator for spectral characterization of multi-junction modules. Other useful applications include evaluating the dependence of the electrical parameters on the average photon energy and spectral responsivity measurements of multi-junction PV devices.
ABSTRACT In this work the authors show results of a measurement inter-comparison campaign that sa... more ABSTRACT In this work the authors show results of a measurement inter-comparison campaign that saw the cooperation of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI-ISAAC, indoor characterization), the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA, outdoor characterization) and the University of Cyprus (indoor and outdoor characterization). The measurement campaign is extremely useful to improve the know-how of the centres involved. Aside the well-known spectral mismatch effects, the importance of the "capacitive effect" is highlighted in this work, which arises when the tested high-efficiency CPV cell are characterized indoor on a pulsed solar simulator, depending on the duration of the pulse.
... rd EU PVSEC, Valencia, 552-555 (2008). 5. MJ Currie, JK Mapel, TD Heidel, S. Goffri and MA Ba... more ... rd EU PVSEC, Valencia, 552-555 (2008). 5. MJ Currie, JK Mapel, TD Heidel, S. Goffri and MA Baldo, Science 321, 226-228 (2008). ... & Solar Cells 93, 176-182 (2009). 7. LH Slooff, EE Bende, AR Burgers, T. Budel, M. Pravettoni, RP Kenny, ED Dunlop and A. Büchtemann, Phys. ...
ABSTRACT Performance testing of high-efficient, highly capacitive c-Si modules with pulsed solar... more ABSTRACT Performance testing of high-efficient, highly capacitive c-Si modules with pulsed solar simulators requires particular carefulness in order to avoid measurement artifacts. These devices in fact usually require a steady-state solar simulator or pulse durations longer than 100 ms. The aim of this work was to validate an alternative method for the testing of highly capacitive c-Si modules using a to-ms single pulse solar simulator. Our approach attempts to reconstruct a quasi steady-state IV curve of a highly-capacitive device during one single to-ms flash by applying customized voltage profiles -in place of a conventional V ramp -to the terminals of the device under test. The most promising results were obtained by using V profiles which we name "dragon-back" (DB) profiles. When compared to the reference IV measurement (obtained by using a multi-flash approach), the dragon-back V profile method provides excellent results with differences in the estimation of Pmax below ±0.5% (as well as of Isc, Voc, and FF). For the testing of highly-capacitive devices the method is accurate, fast (two flashes -possibly one -required), and cost-effective.
Progress in Photovoltaics Research and Applications
This paper describes the preliminary results of an intercomparison of spectroradiometers for glob... more This paper describes the preliminary results of an intercomparison of spectroradiometers for global (GNI) and direct normal incidence (DNI) irradiance in the visible (VIS) and near infrared (NIR) spectral regions together with an assessment of the impact these results may have on the calibration of triple-junction photovoltaic devices and on the relevant spectral mismatch calculation. The intercomparison was conducted by six European scientific laboratories and a Japanese industrial partner. Seven institutions and seven spectroradiometer systems, representing different technologies and manufacturers were involved, representing a good cross section of the todays' available instrumentation for solar spectrum measurements.
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