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The integration of energy storage systems (ESS) in PV plants is a very topical subject. In recent years, many research activities have been addressed to PV plants combined with batteries. Most of the papers in literature refer to plants for residential or industrial users with significant self-consumptions. Only a few papers investigate on ESS for utility-scale PV plants and on the optimal energy management strategies, some examples are in [1], [2]. As a contribution to fill this gap, this paper presents a study on a specific power layout in which the ESS is distributed into the PV field and no longer centralized close to the inverter cabin, as for the majority of the existent PV plants with ESS. Focus is on the design and implementation of suitable models for both the PV field and the ESS with the purpose to establish optimal energy management strategies. The validation process of such models has been carried out through laboratory tests as well as exploiting data coming from the monitoring system of a real PV plant in Central Italy.

35th European Photovoltaic Solar Energy Conference and Exhibition; 1935-1941, One of the most considered solutions to improve the performance of PV plants is the adoption of distributed power converters. The evaluation of the performance increasing by using string inverters or optimizers instead of central inverters in utility-scale PV fields is usually a difficult task due to several reasons such as numerous partial unavailabilities, monitoring system issues, operating constraints imposed by the Power Plant Controllers, etc. To support the data analysis and to forecast the behavior of the PV field under several operating scenarios, a novel modeling approach addressed to large PV plants with multiple conversion stages has been introduced. This work is focused on the comparison among central and string converters installed for testing purpose in two different subfields of the Enel Green Power 300 MW PV plant in Nova Olinda (Brazil). The elaboration of data acquired by the PV plant monitoring system in some months using the developed model highlights that string inverters ensure a remarkable gain in terms of produced energy. Anyway, the accurate estimation of such gain requires data for a larger time period in order to detect the variations due to seasonality. Moreover, the identification of the causes leading to mismatch phenomenon compensated by string inverters requires further investigations in future works.

In this paper, the AMPS-1D (Analysis of Microelectronic and photonic structure) simulation program is used to understand the origin of the differences observed in Space Charge Limited Current (SCLC) analysis in thin and thick a-Si:H n + -i- n+ structure. For that purpose, the problem of applicability of SCLC measurements to n+-i-n+ a-Si:H samples are investigated by using both the thin (0.3 m m) and thick (3 m m) samples. The simulation results show that activation energy in thick samples is larger than in thinner samples, which are an agreement with the experimental results. It is emphasized that this method is highly useful for good quality a-Si:H samples, even if it is a thin sample, and den Boer analysis gives correct information about the density of states. This information comes from the states in the upper limited part of the gap, as exhibited by the lower activation energy of thin samples.

Contains fulltext : 126098.pdf (Publisher’s version ) (Open Access) OBJECTIVES: To evaluate the immunological and viral consequences of planned treatment interruptions (PTI) in children with HIV. DESIGN: This was an immunological and virological sub-study of the Paediatric European Network for Treatment of AIDS (PENTA) 11 trial, which compared CD4-guided PTI of antiretroviral therapy (ART) with continuous therapy (CT) in children. METHODS: HIV-1 RNA and lymphocyte subsets, including CD4 and CD8 cells, were quantified on fresh samples collected during the study; CD45RA, CD45RO and CD31 subpopulations were evaluated in some centres. For 36 (18 PTI, 18 CT) children, immunophenotyping was performed and cell-associated HIV-1 DNA analysed on stored samples to 48 weeks. RESULTS: In the PTI group, CD4 cell count fell rapidly in the first 12 weeks off ART, with decreases in both naive and memory cells. However, the proportion of CD4 cells expressing CD45RA and CD45RO remained constant in both groups. The increase in CD8 cells in the first 12 weeks off ART in the PTI group was predominantly due to increases in RO-expressing cells. PTI was associated with a rapid and sustained increase in CD4 cells expressing Ki67 and HLA-DR, and increased levels of HIV-1 DNA. CONCLUSIONS: PTI in children is associated with rapid changes in CD4 and CD8 cells, likely due to increased cell turnover and immune activation. However, children off treatment may be able to maintain stable levels of naive CD4 cells, at least in proportion to the memory cell pool, which may in part explain the observed excellent CD4 cell recovery with re-introduction of ART.

27th European Photovoltaic Solar Energy Conference and Exhibition; 285-289, Epitaxial deposition of high-quality GaAs layers on cost effective Si substrates is a quite desirable route to decrease III-V cell cost and guarantee mass production for very high efficiency solar cells for Photovoltaic concentration (CPV). Several techniques have been proposed for the deposition of SiGe virtual substrates. Among them we propose two different methods for the realization of Si-Ge virtual substrates. The first one based on PECVD deposition of graded Si-Ge microcrystalline and amorphous layers having different hydrogen content is nearest to others proposed PECVD approaches. The Si-Ge stacked layers are conditioned by laser crystallization and/or Solid Phase crystallization. The second one is an innovative proposal based on a the utilization of a deposition system developed in our laboratories which can assure simultaneous deposition and X-Y laser beam laser crystallization processing under vacuum. Preliminary results are very interesting showing a high degree of crystallinity of the Si/Ge layers realized layers.

26th European Photovoltaic Solar Energy Conference and Exhibition; 2519-2524, This paper is concerned with the numerical simulation of amorphous silicon single junction solar cells, done to improve the device properties of a-Si:H pin single junction solar cells and to understand the degradation kinetics. Analysis of Microelectronic and photonic structure device simulation program (AMPS-1D) has been used to present data concerning the optimization of electronic properties of amorphous silicon p-i-n solar cells and examine the correlation of the external electrical characteristics to the internal solar cell properties such as band diagram, the electric field profile, free and trapped carrier concentrations, space charge density, recombination rate profiles, electron and hole lifetime and spectral response. The simulation program and its application were extensively described. Applying an optimized graded buffer layer at p+/i interface of single cells a further efficiency improvement has been realized. A standard procedure of midgap density of state optimization of p+ window layer and p+/i buffer layer has been performed. We have investigated the degradation kinetics of a-Si:H solar cells with improved buffer design. The influence of the mid gap defect density and the thickness variations in the intrinsic layer were also studied to improve the stability. Our findings show that thin cells can be exposed to light for longer periods before degradation effect dominates their operation.