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Abstract Recently bifacial n-type passivated emitter and rear totally diffused (PERT) monocrystalline silicon solar cells have become one hot spot in photovoltaic (PV) industries, due to good bifaciality, high and stabilised conversion efficiency. Unlike passivated emitter and rear contacts (PERC) structure, n-PERT solar cells require the use of a thin and uniform back surface field (BSF) layer, usually achieved by phosphorus doping. In this study, we optimised the phosphorus diffusion process in terms of surface concentration, junction depth and carrier lifetime. The effects of different phosphorus BSF were investigated by fabricating n-type front and back contact (nFAB) PERT solar cells using industrial feasible approaches and M2 size Czochralski (Cz) monocrystalline Si wafers (6 in., 244.32 cm2). Good phosphorus profiles were developed, which gives low parasitic absorption, low contact resistance and low J0 value when passivated with silicon nitride (SiNx) layer. The optimised champion cell shows a high Voc of 666.5 mV, Jsc of 40.2 mA/cm2, fill factor of 79.9%, efficiency of 21.43% from front side-illumination, together with a good bifaciality factor of 93.0%.

Abstract This paper presents a mathematical model for the prediction of the probabilities of reverse power flow exceeding predefined critical thresholds at feed-in points of a distribution network. The parametric prediction model is based on hourly forecasts of global horizontal irradiation and uses copulas, a tool for modeling the joint probability distribution of two or more strongly correlated random variables with non-Gaussian (marginal) distributions. The model is used for determining the joint distribution of forecasts of global horizontal irradiation and measured solar power supply at given feed-in points, where respective sample datasets were provided by Deutscher Wetterdienst and the N-ERGIE Netz GmbH. It is shown that the fitted model replicates important characteristics of the data such as the corresponding marginal densities. The validation results highlight strong performance of the proposed model. The copula-based model enables to predict the distribution of solar power supply conditioned on the forecasts of global horizontal irradiation, thus anticipating great fluctuations in the distribution network.

Abstract The cooperative effect of hybrid Au-Ag nanoparticles and organic-inorganic cathode interfacial layers to advance the power conversion efficiency (PCE) of regio regular (rr) P3HT:PCBM based polymer solar cells (PSCs) are systematically demonstrated. In this work initially, two types of plasmonic nanoparticles (NPs), namely, citrate stabilized gold (AuNPs) and silver (AgNPs) were separately synthesized and then physically blend together with three different volume ratio [AuNPs + AgNPs (25:75), AuNPs + AgNPs (50:50) and AuNPs + AgNPs (75:25)]. These three blended NP solutions were then mixed together in the PEDOT:PSS (20 v/v %) hole extraction layer (HEL) to form three new NPs doped HEL and their effect on the rr-P3HT:PCBM based PSCs were systematically analyzed. For dual organic-inorganic cathode interfacial layers, two organic hole blocking materials, BPhen and BCP were used for enhanced charge collection in combination with LiF:Al as conventional cathode electrode. The collective effect of hybrid NPs with the dual cathode interfacial layers was examined with two varying active polymer blends, rr-P3HT:PC61BM and rr-P3HT:PC71BM. It has been found that the PCE increases considerably for both the active blend systems, with PEDOT:PSS + [AuNPs:AgNPs (25:75)] + BCP:LiF:Al as the modified cathode electrode. This is due to suitable electronic energy level matching of BCP:LiF:Al and active blend with the excellent surface plasmon property of the AuNPs:AgNPs (25:75) in the UV–Visible region compared to AuNPs:AgNPs (50:50) and AuNPs:AgNPs (75:25). Devices having configuration PEDOT:PSS + [AuNPs:AgNPs (25:75)] as HEL, rr-P3HT:PC71BM as active blend and BCP:LiF:Al provided PCE, ɳmax = 5.71% with Jsc = 16.44 mA/cm2, Voc = 0.58 V, FF = 60% and device with rr-P3HT:PC61BM as active blend layer was showing as PCE, ɳmax = 5.31% with Jsc = 14.77 mA/cm2, Voc = 0.58 V and FF = 62% with the same PEDOT:PSS + [AuNPs:AgNPs (25:75)] layer and BCP:LiF:Al. These results conclusively described a very simple technique in which the cooperative effect of plasmonic hybrid metals nanoparticles and dual cathode interfacial layers outstandingly enrich the PCE and in general the complete nature of rr-P3HT:PCBM based PSCs.

Abstract The state-of-the-art modelling of solar collectors as described in the European Standard EN 12975-2 is based on equations describing the thermal behaviour of the collectors by characterising the physical phenomena, e.g. transmission of irradiance through transparent covers, absorption of irradiance by the absorber, temperature dependent heat losses and others. This approach leads to so called collector parameters that describe these phenomena, e.g. the zero-loss collector efficiency η 0 or the heat loss coefficients a 1 and a 2 . Although the state-of-the-art approach in collector modelling and testing fits most of the collector types very well there are some collector designs (e.g. “Sydney” tubes using heat pipes and “water-in-glass” collectors) which cannot be modelled with the same accuracy than conventional collectors like flat plate or standard evacuated tubular collectors. The artificial neural network (ANN) approach could be an appropriate alternative to overcome this drawback. To compare the different approaches of modelling investigations for a conventional flat plate collector and an evacuated “Sydney” tubular collector have been carried out based on performance measurements according to the European Standard EN 12975-2. The investigations include the parameter identification (training), the comparisons between measured and modelled collector output and the simulated yearly collector yield for a solar domestic hot water system for both models. The obtained results show better agreement between measured and calculated collector output for the artificial neural network approach compared with the state-of-the-art modelling. The investigations also show that for the ANN approach special test sequences have to be designed and that the determination of the ANN that fits the thermal performance of the collector in the best way depends significantly on the expertise of the user. Nevertheless artificial neural networks have the potential to become an interesting alternative to the state-of-the-art collector models used today.

Etude experimentale des relations des phases du systeme. Determination des points invariants, des compositions en phases correspondantes, temperatures de transition et changements d'enthalpie

In this paper the work and current findings about thin film solar cell technology––CISCuT (CuInS2 on Cu-tape) is reviewed. Taking current market requirements into account it is shown that CISCuT based solar cells and modules could satisfy the demands of the market. The results of this study show that especially flexible and lightweight cells and modules should be made available on the basis of CISCuT. The innovative reel-to-reel technology to make quasi-endless tapes of solar cells and the inseparable connected unique absorber growth is explained in more detail. It is shown that the growth process can be monitored and even be controlled by means of an on-line measurement of electrical properties, which are strongly correlated to the properties of the final solar cell. Investigations and modelling of cell physics result in a p-i-n like cell structure of the CISCuT solar cells. The efficiency potential is explained for this device connected with an outlook for further improvement of the cell performance. The current batch of cells with an efficiency of about 9% is demonstrated connected with an appropriate stability of cells. The efficiency losses during the module assembling process are discussed. Efficiencies of test modules up to 7% are reported.

Abstract The wood drying process consumes a great deal of energy with pollutants carrying bi-products. To preserve tropical and temperate forests and protect the environment, it is important to optimize the use of energy using solar dryers that are less expensive and easy to construct. In this paper, mathematical modeling of a novel solar dryer for firewood has been examined and experimentally validated using average relative error analysis. The solar dryer functioning in forced convection is constructed with wood and wood panels, and it is constituted of a solar collector. This field experimental solar dryer is numerically simulated for climatic conditions existing in Yaounde and Nancy environments. The role of the solar collector is methodically identified ultimately permitting its usage as an effective dryer in a temperate environment. Our results indicate that in the tropical environment, and during the summer and spring seasons, the thermal efficiency is higher than 40 %, but lower than 30 % during the winter and autumn seasons. The construction of this solar dryer type of 7 steres capacity functioning all the year is capable of reducing the production of pollutants near 26.106 tons of CO2 and 58.433 tons of CO2 for Nancy and Yaounde respectively. Constructed for a life duration of 10 years, the payback period is equal to 1.893 years and 0.971 years when the dryer is used all the year from Nancy and Yaounde respectively.