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Abstract Copper is a common impurity in photovoltaic silicon. While reported to precipitate instantly in n-type Si, copper causes light-induced degradation (Cu-LID) in p-type Si. Recently, partial recovery of Cu-LID was observed after only few minutes of dark annealing at 200 °C. In this contribution, we investigate the effects of the dark anneal on Cu-LID-limited minority carrier lifetime both experimentally and by simulations. Surprisingly, after initial recovery, the dark anneal results in further degradation corresponding to a many-fold increase in recombination activity compared to the degraded state after illumination. This anneal-induced degradation can potentially cause additional losses in accidentally Cu-contaminated devices when exposed to elevated temperatures, for example during recovery and regeneration treatments of solar cells. Transient ion drift measurements confirmed that the anneal-induced degradation cannot be attributed to residual interstitial Cu after illumination. After hundreds of hours of annealing, the samples showed another recovery. To analyze these experimental results, a comparison to simulations is performed at the end of the paper.

AbstractThe paper presents the concept, implementation and results of the hardware-in-the-loop test bench (HiL) established for a medium-scale parabolic trough collector system under construction. The 122.4m2 plant heats the make-up water of a fossil-fired steam boiler in a meat factory in Austria. The test bench consists of a plant model implemented in a Real-Time machine, which is electrically connected to the plant control hardware (PLC) through several I/O terminals. Within the test bench, it is possible to run different test cycles and emulate critical operation scenarios like collector loop overheating. The control strategy of the solar plant can be checked with minimal risk. The test bench also enables to improve the control ability to cope with weather and sensor disturbances. A suitable fault detection strategy is prepared, which minimizes the risk of component damage and enhances the plant availability.

AbstractThe energy sustainability, in the era of sources diversification [1], can be guaranteed by an energy resources utilization most correct, foreseeing no predominance of one source over the others in any area of the world but a proper energy mix, based on locally available resources and needs [2]-[4]. In this scenario, manageable with a smart grid system [5], [6], a virtuous use of RES must be visible, recognizable and quantifiable, in one word traceable [7]. The innovation of the traceability concept consists in the possibility of having information concerning the exact origin of the electricity used for a specific end use, in this case EV charging [8]. The traceability, in a context of increasingly sustainability [9], [10] and smartness city, is an important develop tool because only in this way it is possible to quantify the real emissions produced by EVs and to ensure the real foresight of grid load. This paper wants investigate the real ways to introduce this kind of real energy accounting, through the traceability.

AbstractA high-pressure/high-temperature reactor has been used to lead PVT and H2-solubility experiments in saline solutions covering conditions for which no data are available in literature: salinity up to halite concentration, pressure up to 200bar and temperature up to 373K. The hereby presented preliminary results show significant deviations from theoretical models. Further analysis and more measurements are needed to assess precision and reproducibility of these measurements; however they pinpoint the importance of experimental work to reliably constrain predictive models.

Abstract This paper presents a new analytical expression intended to accurately evaluate the leakage inductance of transformers in the step-up DC-DC conveter in the high frequency range in which the behavior of the magnetic field within the windings is altered. Unlike conventional expressions, which usually overestimate the leakage inductance at higher frequencies, this expression accounts for high frequency behavior of the magnetic field and provides high accuracy when operating at high frequencies. These high accuracy and applicability makes the derived expression of interest for designers to avoid time consuming finite element simulations without compromising with accuracy. The expression is validated by 2-D FEMM simulation, as well as by measurement.

AbstractMinority carrier lifetime measurements are a major characterization technique regarding the material quality of semiconductors. In particular, a large variety of electrically active defects can be detected at room temperature even if present in low concentrations down to 1010cm-3 only. Transient and (quasi) steady-state methods as well as combinations of both have been established. However, in either case, the measurable lifetime is influenced not only by the bulk lifetime itself but by a number of additional sample properties such as surface recombination, sample thickness, and wavelength of the carrier-generating light.An analytical model is investigated that relates the measurable lifetime to the bulk lifetime for samples of arbitrary thickness and surface quality when measured under steady-state conditions. It thus provides a generalization for the frequently used limiting expressions for thin Si-wafers and thick Si-blocks. In particular it allows the interpretation of data obtained for samples of intermediate thickness. Furthermore, it is shown under which conditions the surface properties can influence the lifetime measurements even for thick blocks. Finally, an approach is proposed that allows the simultaneous extraction of both bulk lifetime and surface recombination velocity. It is argued that reliable measurements of bulk properties are possible only for samples being thicker than some critical thickness while surface properties are best determined on samples thinner than this critical thickness. A quantitative estimate for this critical thickness is given. Experimental results are shown that demonstrate the applicability of the model.

AbstractThis work presents a novel insight to the aspects of silicon surface passivation and the influence of thin intermediate layers generated by chemically grown silicon oxides. Strong light induced effects on passivation properties are investigated. After exposure to light (0.25 suns) for about 60 s, samples based on a PECVD layer system consisting of SiNx and SiO2 deposited on crystalline silicon with native silicon oxides show an improvement of more than 100% in minority carrier lifetime. These improvements are stable over months and lead to effective surface recombination velocities as low as 10cm/s on chemically polished p-type FZ wafers. With the use of different light sources, corona charging and annealing experiments the effect is investigated in detail. Finally, the effect is proposed to be a photo induced curing process of defects in the Si/SiO2 interface with the incorporation of hydrogen.