Diego La Cascia

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.

Economical evaluation of ecological benefits of the demand side management

Environmental pollution and over-exploitation of non-renewable sources to find energy are current topics for the modern world that is now at having to deal with several issues such as the greenhouse effect, acid rain and climate change. In this study, the economical estimate of the savings in carbon dioxide obtained with a careful management of electrical loads is presented. Four particular scenarios are designed as case studies: Italy, France, United Kingdom and Germany. A comparison is presented with a similar study, made in 2007, when green energies were not yet very developed.

Design optimization for the adoption of bonded magnets in PM BLDC motors

The increment of the manageable power in machines where the normally adopted ferrites are replaced with bonded magnets can vary and can introduce saturation problems depending on the variations in the magnetic circuit design. The saturation of the magnetic circuit distorts the phase voltages, introducing undesired harmonics in the connection to the mains. Combined modifications of both stator poles and rotor ring of a Brushless DC motor are proposed to evaluate their impact on the increment of the manageable power and on the harmonic content. Several magnetic circuit modifications have been considered and the paper presents the results of the most reasonable solutions, obtaining significant increments of the power. The activity is still carrying on and will take into account also the magnetization directions.

Photovoltaic module characteristics from CIGS solar cell modelling

We describe our approach to the task of modelling, both at single cell structure and complete module levels, during the solar cell technology development process. This can give very helpful indications, in terms of global photovoltaic module characteristics, for the assessment of intermediate research results and planning of further experiments. We make reference specifically to the fabrication of thin film CIGS solar cells by means of single-step electrodeposition, a technique which appears fairly easy and low-cost but, at the same time, can lead to quite different structural and electrical properties.

A new modified Inc-Cond MPPT technique and its testing in a whole PV simulator under PSC

In this paper a new modified Inc-Cond MPPT technique able to lead PV plants to work in the real MPP (Maximum Power Point) under PSC (Partial Shading Condition) is proposed. The new Inc-Cond MPPT technique working principle is fully explained, discussed and then successfully tested in a whole and reliable PV simulator conceived and set-up by the Authors in order to test and compare several new MPPT algorithms. The simulation results show that the proposed Inc-Cond MPPT technique is able to successfully lead the PV plant to work in the real MPP both in the cases of instantaneous and gradual changing of shading and of temperature conditions.

Mixed heuristic-non linear optimization of energy management for hydrogen storage-based multi carrier hubs

In this paper, an heuristic and non-linear programming based algorithm to optimally operate an energy hub plant is proposed. The energy hub plant described in this work is the test system for the European INGRID research project. The Energy Management System defines the optimal energy flows dispatch in order to obtain the energy balance and the maximum profit for the owner of the plant. The problem is highly constrained and non-linear, for this reason the methodology cannot rely on Linear Programming (LP) methods. The Energy Management System manages two energy carriers, electricity and hydrogen, interfacing three distribution networks: the electricity, the hydrogen and the methane networks. Simulations show that the buffer function of the system is as more intense as greater the efficiency of the conversion systems is, as compared to the prices variations along the day. Although heuristic search methods are well-suited for the solution of highly constrained non-linear problems, the applications carried out over the INGRID project test-bed show that improved solutions can be found applying a non-linear programming method named Generalised Reduced Gradient (GRG), to refine the solutions outputted by heuristic algorithms, such as Simulated Annealing or Tabu Search.

On multi-objective optimal reconfiguration of MV networks in presence of different grounding

The present work faces the traditional multi-objective optimal reconfiguration problem of a distribution grid including the safety issue in the objective functions. Actually, in many medium voltage networks still transformers with ungrounded neutral and with resonant grounded neutral coexist in the same area. This may be sometimes cause of problems during a single-line-to-ground fault if the ground electrodes of one or more cabins, initially designed for satisfying the safety conditions in a resonant grounded neutral network, after the reconfiguration are in a grounded neutral one or vice versa. In the paper a safety objective function is defined and the Non dominated Sorting Genetic Algorithm II used for solving the optimization problem formulated considering the minimization of the energy losses, the maximization of the load balancing among the transformers, and the minimization of the safety function. The safety function is defined both in the case of independent grounding systems and in the case of grounding systems interconnected by the metal shields of the cables. Also the effects of a Global Grounding System on the multi-objective reconfiguration problem so formulated are discussed. Finally a case study is analyzed presenting also a comparison between the Non dominated Sorting Genetic Algorithm II and a traditional Fuzzy Evolution Strategy algorithm.

Green Data Centres providing ancillary services to power grid

This work investigates the possibility for a Data Centre to provide services to the Grid. In particular, the paper simulates a sudden shift of frequency because of a power decrease and estimates how a real-life Data Centre can contribute the secondary frequency regulation.

A novel heuristics-based energy management system for a multi-carrier hub enriched with solid hydrogen storage

In this paper, an efficient optimization algorithm for the energy management of a grid-connected energy hub plant is proposed. The Simulated Annealing algorithm is adopted for the solution of the energy management problem aiming at the profit maximization for the owner of the energy hub plant. The use of a heuristic algorithm was required by the non-linearity of the efficiencies of each component in the energy transformation stages. The proposed heuristics is applied to a large energy hub, corresponding to the simulation of the test-bed that is being designed and developed inside the ongoing INGRID European research project.

Effects of double ground faults in Wind Farms collector cables

Medium Voltage collector cables of Wind Farms have metal shields connected to the grounding systems of the towers and of the connection station. Thanks to this bonding, when a ground fault occurs, the fault current splits itself among all the grounding systems of the wind farm, this causing a reduction of the ground potential rise at the fault location. Nevertheless, in presence of double ground faults, very high ground potential rises occur at the two fault locations and safety against electric shock is not always assured. In order to study this issue, the paper presents a model for simulating in a simple way the effects of double ground faults occurring in Medium Voltage collectors of extended wind plants connected to the High Voltage network.