Second international spectroradiometer intercomparison: results and impact on PV device calibration

This paper describes the results of an intercomparison of spectroradiometers for measuring global normal incidence and direct normal incidence spectral irradiance in the visible and in the near infrared, together with an assessment of the impact these results may have on the calibration of the short circuit current (I-sc) 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 spectroradiometer systems, for a total of 13 different instruments/channels using two different technologies and made by four different manufacturers were involved. This group of systems represents a good cross section of the instrumentation for solar spectrum measurements available to date. The instruments were calibrated by each partner prior to the intercomparison following their usual procedure and traceability route in order to verify the entire measurement and traceability chain. The difference in measured spectral irradiance showed to have an impact on the calibration of a set of Iso-Type cells varying from +/- 2% to +/- 14% for middle and bottom cell, respectively

Second international spectroradiometer intercomparison: preliminary results and impact on PV device calibration

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

Development of an electronic interface for diagnostics of photovoltaic strings

Photovoltaic (PV) systems can generate less energy than expected owing to inefficiency of the inverter, deterioration of the PV modules or conditions of partial shading and soiling. The monitoring and diagnosis techniques of PV systems are therefore quite important to recognize the causes of the performances reduction and optimize the PV energy production. For a more in-depth diagnostic capability, it would be necessary to know the short-circuit current (Isc) and the open-circuit voltage (Voc) of the PV system. These quantities are indeed useful to recognize non-uniform operating conditions of the PV modules (partial shadings, malfunctions, generic electro-optical mismatch conditions), estimate the PV module junction temperature and the voltage temperature coefficient. However, so far, these quantities cannot be measured by the inverter in operative conditions. With this contribution we propose and test a new electronic interface for a more advanced diagnostics of the PV system to be easily installed between the PV string and the inverter, able to measure the values of Isc and Voc as well as the inverter voltage, current and power working points, avoiding any downtime of the PV system and minimizing the power losses during the diagnosis activity

Optical modelling based on angle and temperature dependent EQE measurements on III-V multi-junction solar cells

International audienc

Anti-soiling coatings for solar cell cover glass: Climate and surface properties influence

Publisher Copyright: © 2018 Elsevier B.V.The objective of this study has been twofold: i) to investigate different strategies for CPV module glass surface modification, in particular preparing hydrophilic and hydrophobic coatings in order to reduce the dust accumulation (soiling) on the module surface; ii) to perform a joint comparative soiling testing in Italy, Spain and Brazil in order to understand the limit and advantages of the proposed anti-soiling coatings in different climate condition. Two TiO2/SiO2 films with different titanium content have been synthesized and benchmarked against pure TiO2 in relation to transparency and hydrophilicity. Moreover, a hydrophobic antireflective material based on functionalized-SiO2 thin film was also investigated. All these coatings have been deposited over low iron float glass substrates by sol-gel dip-coating and electron-beam evaporation technique. TiO2/SiO2 and functionalized-SiO2 films showed higher transmittance in visible range than pure TiO2. TiO2/SiO2 films showed a persistent superhydrophilic character with water contact angles near to 0° while functionalized-SiO2 presented hydrophobic property. The joint comparative soiling tests showed the importance of setting anti-soiling strategies in region characterized by more dry climate: in Brazil, which during the soiling test was characterized by a long dry period, the anti-soiling coatings were effective in reducing the soiling deposition and in the removal of the contaminants by rainwater; in Spain and Italy, the more frequent rain precipitation made the soiling effect less relevant, however, the deposition of anti-soiling coating on the module cover glass allowed to fully recover the initial transmittance after rain washing. A chemical and mineral characterization of the soiling has been carried out revealing the dependence of the contaminants from the environment conditions (e.g. car traffic, presence of industries, amount of rain and local minerals in the ground).The authors gratefully acknowledge the support from SUN ON CLEAN project (European Commission, Call: FP7-PEOPLE-2011-IRSES, International Research Staff Exchange Scheme - MARIE CURIE ACTIONS) between CEFET-MG-Brazil, RSE-Italy, TECNALIA-Spain. The authors gratefully acknowledge the financial support of the Basque Government (project FRONTIERS ref. KK-2015/00101 and KK-2016/00093 ) and FAPEMIG (Minas Gerais State Agency for Research and Development). The authors gratefully acknowledge the support from SUN ON CLEAN project (European Commission, Call: FP7-PEOPLE-2011-IRSES, International Research Staff Exchange Scheme - MARIE CURIE ACTIONS) between CEFET-MG-Brazil, RSE-Italy, TECNALIA-Spain. The authors gratefully acknowledge the financial support of the Basque Government (project FRONTIERS ref. KK-2015/00101 and KK-2016/00093) and FAPEMIG (Minas Gerais State Agency for Research and Development).Peer reviewe

Capabilities of Grazing Incidence X-ray Diffraction in the Investigation of Amorphous Mixed Oxides with Variable Composition

X-ray Diffraction has been fully exploited as a probe to investigate crystalline materials. However, very little research has been carried out to unveil its potentialities towards amorphous materials. In this work, we demonstrated the capabilities of Grazing Incidence X-ray Diffraction (GIXRD) as a simple and fast tool to obtain quantitative information about the composition of amorphous mixed oxides. In particular, we evidenced that low angle scattering features, associated with local structure parameters, show a significant trend as a function of the oxide composition. This evolution can be quantified by interpolating GIXRD data with a linear combination of basic analytical functions, making it possible to build up GIXRD peak-sample composition calibration curves. As a case study, the present method was demonstrated on Ta2O5–SiO2 amorphous films deposited by RF-magnetron sputtering. GIXRD results were validated by independent measurement of the oxide composition using Rutherford Backscattering Spectrometry (RBS). These materials are attracting interest in different industrial sectors and, in particular, in photovoltaics as anti-reflection coatings. Eventually, the optical properties measured by spectroscopic ellipsometry were correlated to the chemical composition of the film. The obtained results highlighted not only a correlation between diffraction features and the composition of amorphous films but also revealed a simple and fast strategy to characterize amorphous thin oxides of industrial interest

Study of the Cross-Influence between III-V and IV Elements Deposited in the Same MOVPE Growth Chamber

We have deposited Ge, SiGe, SiGeSn, AlAs, GaAs, InGaP and InGaAs based structures in the same metalorganic vapor phase epitaxy (MOVPE) growth chamber, in order to study the effect of the cross influence between groups IV and III-V elements on the growth rate, background doping and morphology. It is shown that by adopting an innovative design of the MOVPE growth chamber and proper growth condition, the IV elements growth rate penalization due to As “carry over” can be eliminated and the background doping level in both IV and III-V semiconductors can be drastically reduced. In the temperature range 748–888 K, Ge and SiGe morphologies do not degrade when the semiconductors are grown in a III-V-contaminated MOVPE growth chamber. Critical morphology aspects have been identified for SiGeSn and III-Vs, when the MOVPE deposition takes place, respectively, in a As or Sn-contaminated MOVPE growth chamber. III-Vs morphologies are influenced by substrate type and orientation. The results are promising in view of the monolithic integration of group-IV with III-V compounds in multi-junction solar cells

Second international spectroradiometer intercomparison: results and impact on PV device calibration

This paper describes the results of an intercomparison of spectroradiometers for measuring global (GNI) and direct (DNI) normal incidence spectral irradiance in the visible (VIS) and in the near infrared (NIR), together with an assessment of the impact these results may have on the calibration of the short circuit current (Isc) 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, for a total of thirteen different instruments/channels using two different technologies and made by four different manufacturers were involved. This group of systems represents a good cross section of the instrumentation for solar spectrum measurements available to date. The instruments were calibrated by each partner prior the intercomparison following their usual procedure and traceability route in order to verify the entire measurement and traceability chain. The difference of measured spectra shape showed to have an impact on the calibration of a set of Iso-Type cells varying from ±2% to ±12% for middle and bottom cell, respectively.JRC.F.7-Renewables and Energy Efficienc