G. Cipriani

Economic analysis on dynamic photovoltaic systems in new Italian “feed in tariffs” context

Dynamic photovoltaic generators, based on the application of solar-trackers, are able to give an increment to the electric energy production from solar source. Their realization and maintenance costs are certainly higher than those of fixed ones. In this paper the Authors propose a method to estimate the increment of electrical energy generation that must be guaranteed by a dynamic photovoltaic generator, so as its realization could be more favorable with respect to that of a fixed generator one with the same rated power. This method, developed by means of classical economic indexes like the Pay-Back-Period and the Net Present Value, takes in to account the economic incentives for the PV systems. The method has been here performed on several numerical applications by considering different size of PV systems and of biaxial solar-trackers. Results report the possible advantages of the two PV plants type.

A PV plant simulator for testing MPPT techniques

This paper introduces a versatile and reliable photovoltaic systems simulator. It includes the main components of a photovoltaic plant: a PV string and a PWM controlled boost chooper. The key feature of this simulator is the ability to consider different and non-uniform irradiation and temperature conditions (partial shading and partial heating of the strings). All the different I-V and P-V or P-I characteristics can then be determined in such non-uniform irradiation and temperature conditions, with the aim to try different MPPT algorithms. The simulator also allows to verify an enhanced version of the Incremental Conductance algorithm (IncCond) where, in order to reach the real absolute maximum power condition, the reference control current of the boost chopper are periodically reset to a given percentage of the short circuit current at standard conditions. After this perturbation, the steady state power values are registered and compared to establish the final value of reference current that allows the IncCond algorithm to reach a steady state at the real abolute maximum power transfer.

Thin Film CIGS Solar Cells, Photovoltaic Modules, and the Problems of Modeling

Starting from the results regarding a nonvacuum technique to fabricate CIGS thin films for solar cells by means of single-step electrodeposition, we focus on the methodological problems of modeling at cell structure and photovoltaic module levels. As a matter of fact, electrodeposition is known as a practical alternative to costly vacuum-based technologies for semiconductor processing in the photovoltaic device sector, but it can lead to quite different structural and electrical properties. For this reason, a greater effort is required to ensure that the perspectives of the electrical engineer and the material scientist are given an opportunity for a closer comparison and a common language. Derived parameters from ongoing experiments have been used for simulation with the different approaches, in order to develop a set of tools which can be used to put together modeling both at single cell structure and complete module levels.

A device for PV modules I-V characteristic detection

In this paper an electronic load suitable for the PV module I-V characteristic curve fast detection is presented. This device is designed in agreement with the IEC 82 Techinical Committee Standard since it allows the detection of the characteristic starting from voltage values even lower than 3% of the PV module open circuit voltage. The device main features are short time characteristc detection (2 s), limited ripple of the detected characteristic and low cost. Its validation is carried out by comparing measured data with data from simulations. Simulations are carried out considering two different commercial PV modules and by implementing in Matlab-Simulink environment the four lumped parameters PV cell mathematical model. This comparison sets the device is very reliable. Thanks to the device properties, the device allows the execution of experimental surveys directly on the premises, before the plant installation, optimizing the plants efficiency.

A photovoltaic charging system of an electrically assisted tricycle for touristic purposes

In this paper the design, realization and testing of a photovoltaic charging system suitable for the management of an electrically power assisted tricycle are described. This vehicle uses a photovoltaic module as a source of electric energy for the battery recharging. In this work, an overview on the needs of sustainable mobility and on the commercial electrically power assisted velocipedes is presented. The electrical rickshaw prototype, developed in the SDELab laboratory of the University of Palermo, is presented in detail, underlining the design, implementation and developing phases of the photovoltaic charging system assembled on the velocipede. Moreover, tests oriented on the setting up of the whole system and validation tests on the prototype are described, with the aim of determining the growing up of performances. Particular attention is dedicated to the vehicle autonomy, by using the management system here proposed. The results show how is possible to reach an increase of the 30% of the electrical rickshaw autonomy by using the management system conceived by the Authors. Furthermore, these tests are carried out in order to demonstrate that the electrical rickshaw vehicle supported by the PV charging system could be targeted for touristic purposes.

Graded Carrier Concentration Absorber Profile for High Efficiency CIGS Solar Cells

We demonstrate an innovative CIGS-based solar cells model with a graded doping concentration absorber profile, capable of achieving high efficiency values. In detail, we start with an in-depth discussion concerning the parametrical study of conventional CIGS solar cells structures. We have used the wxAMPS software in order to numerically simulate cell electrical behaviour. By means of simulations, we have studied the variation of relevant physical and chemical parameters—characteristic of such devices—with changing energy gap and doping density of the absorber layer. Our results show that, in uniform CIGS cell, the efficiency, the open circuit voltage, and short circuit current heavily depend on CIGS band gap. Our numerical analysis highlights that the band gap value of 1.40 eV is optimal, but both the presence of Molybdenum back contact and the high carrier recombination near the junction noticeably reduce the crucial electrical parameters. For the above-mentioned reasons, we have demonstrated that the efficiency obtained by conventional CIGS cells is lower if compared to the values reached by our proposed graded carrier concentration profile structures (up to 21%).

Parametrical study of multilayer structures for CIGS solar cells

In this paper, a numerical analysis of relevant electrical parameters of multilayer structures for CIGS-based solar cells was carried out, employing the simulation software wxAMPS. In particular, we have focused on thin film cells having a ZnO:Al/ZnO/CdS/CIGS structure with a Molybdenum back contact. The aim of this work is to establish good theoretical reference values for an ongoing experimental activity, where our technology of choice is the single-step electrodeposition. In detail, we have analyzed how the main electrical properties change with the bang gap and the thickness of the absorber layer, for such a type of solar cell structure. Our results show that both efficiency and fill factor strongly depend on the energy gap. Instead, the absorber thickness plays a role up to a few microns, after which the cell parameters remain almost constant. As expected, the theoretical peak efficiency was found for a band gap value of 1.40 eV, corresponding to a Ga/(In+Ga) ratio of 0.66.

Design, sizing and set up of a specific low cost electronic load for PV modules characterization

In this paper, the design, sizing and set-up of a specific low cost electronic load, based on a DC-DC step-down converter, suitable for the PV module I - V characteristic curves determination, is described. In particular, for its set up, a low cost and user friendly micro-controller has been employed in order to generate the PWM signal. The measures carried out connecting the electronic load prototype to a commercial PV module are here presented and discussed. The conceived electronic load has allowed the determination of 80% of the PV module characteristic curves in 2 s. This low measurement time, lower than the time intervals in which weather conditions may change, allows to assume as constant the PV module temperature and the environment conditions. The obtained characteristics, affected by a limited ripple, have been compared with simulation data from the Matlab/Simulink implementation of the most common PV module four and five lumped parameters with good results.

Experimental validation of a distribution theory based analysis of the effect of manufacturing tolerances on permanent magnet synchronous machines

An experimental study on the effect of permanent magnet tolerances on the performances of a Tubular Linear Ferrite Motor is presented in this paper. The performances that have been investigated are: cogging force, end effect cogging force and generated thrust. It is demonstrated that: 1) the statistical variability of the magnets introduces harmonics in the spectrum of the cogging force; 2) the value of the end effect cogging force is directly linked to the values of then remanence field of the external magnets placed on the slider; 3) the generated thrust and its statistical distribution depend on the remanence field of the magnets placed on the translator.

A Prototypal Architecture of a IEEE 21451 Network for Smart Grid Applications Based on Power Line Communications

This paper deals with the development of reliable measurement and communication devices and systems and their integration on a prototypal network architecture for smart grid applications, based on the use of narrowband power line communications (PLCs). The proposed solution is presented and discussed in the framework of the ISO/IEC/IEEE 21451 family of Standards. Currently, PLCs are not properly addressed by the aforesaid Standards; on the other hand, by including such issue, their guidelines could represent a common platform for the integration and interoperability of the proposed systems and devices. This would allow to exploit the benefits of the IEEE 21451 approach also for PLC-based smart grid applications, not only for the known functions of the smart metering, but also for sensing, automation, protection, and control functions and advanced system operation and management.