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An extended study of c-Si cell performance under transient conditions for various concentration ratios,C, between 0.6 and 12.25 is presented. PV cell temperature,Tc, open-circuit voltage,Voc, and short-circuit current,Isc, were measured using an experimental set-up based on a solar light simulator. The dependence ofVoc,Isc, dVoc/dTc, dIsc/dTcandrsonTcwas investigated againstC. A model was developed to predictTc. Generalised formulae were proposed for prediction ofVocandIsc. Theoretically obtainedTcandVocprofiles were compared with the measured ones. A good agreement was observed. The time constants ofVocandTcprofiles were determined experimentally for variousCvalues and lie within ±5% from theoretically predicted time constants. The coefficient dVoc/dTcwas determined for variousCvalues. The results show a decrease in the absolute value of dVoc/dTcagainstC. A partial recovery of PV cell performance through a ventilation process was tried. [ABSTRACT FROM PUBLISHER]

This paper outlines and formulates a compact and effective simulation model, which predicts the performance of single and double glaze flat-plate collector. The model uses an elaborated iterative simulation algorithm and provides the collector top losses, the glass covers temperatures, the collector absorber temperature, the collector fluid outlet temperature, the system efficiency, and the thermal gain for any operational and environmental conditions. It is a numerical approach based on simultaneous guesses for the three temperatures, Tp plate collector temperature and the temperatures of the two glass covers Tg1, Tg2. A set of energy balance equations is developed which allows for structured iteration modes whose results converge very fast and provide the values of any quantity which concerns the steady state performance profile of any flat-plate collector design. Comparison of the results obtained by this model for flat-plate collectors, single or double glaze, with those obtained by using the Klein formula, as well as the results provided by other researchers, is presented. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes an improved approach for (a) the estimation of the mean expected hourly global solar radiation I(h;nj ), for any hour h of a day nj of the year, at any site, and (b) the estimation of stochastically fluctuating I(h;nj ) values, based on only one morning measurement of a day. Predicted mean expected values are compared, on one hand with recorded data for the period of 1995–2000 and, on the other, with results obtained by the METEONORM package, for the region of Patra, Greece. The stochastically predicted values for the 17th January and 17th July are compared with the recorded data and the corresponding values predicted by the METEONORM package. The proposed model provides I(h;nj ) predictions very close to the measurements and offers itself as a promising tool both for the on-line daily management of solar power sources and loads, and for a cost effective PV sizing approach. [Copyright &y& Elsevier]

A synergistic set of NDT techniques, including I-V analysis, UVF imaging, IR thermography, and EL imaging, supports a diagnostics methodology developed in this work to qualitatively and quantitatively identify a wide range of PV defects. The methodology is based on (a) the deviation of the module electrical parameters at STC from their nominal values, for which a set of mathematical expressions was developed that provide an insight into potential defects and their quantitative impact on the module electrical parameters, and (b) the variation analysis of EL images captured at a sequence of bias voltages for a qualitative investigation on the spatial distribution and strength of the defects. The synergy of these two pillars, supported by UVF imaging, IR thermography, and I-V analysis cross-correlating their findings, makes the diagnostics methodology effective and reliable. It was applied on c-Si and pc-Si modules operating from 0-24 years, exhibiting a diversity of defects of varying severity, either pre-existing or formed by natural ageing or externally induced degradation. Defects such as EVA degradation, browning, corrosion in the busbar/interconnect ribbons, EVA/cell-interface delamination, pn-junction damage, e - +hole recombination regions, breaks, microcracks, finger interruptions, and passivation issues are detected. Degradation factors triggering a cascade of internal degradation processes through cause and effect are analysed and additional models are proposed for the temperature pattern under current mismatch and corrosion along the busbar, further empowering the cross-correlation of NDT results. Power degradation was determined from 1.2% in 2 years of operation to more than 50% in modules with film deposition.