• Energy Research

Raccolta delle lezioni della Winter School Gennaio 2011 a Sestriere con docenti italiani e stranieri e studenti italiani e stranieri.

Complex energy systems are made up of a number of components interacting together via different energy vectors. The assessment of their performance under dynamic working conditions, where user demand and energy prices vary over time, requires a simulation tool. Regardless of the accuracy of this procedure, the uncertainty in data, obtained both by measurements or by forecasting, is usually non-negligible and requires the study of the sensitivity of results versus input data. In this work, polynomial chaos expansion technique is used to evaluate the variation of cogeneration plant performance with respect to the uncertainty of energy prices and user requests. The procedure allows to obtain this information with a much lower computational cost than that of usual Monte-Carlo approaches. Furthermore, all the tools used in this paper, which were developed in Python, are published as free and open source software.

The purpose of this paper is to analyze the main techniques for magnetic field mitigation at power frequency and assess their effectiveness presenting two real applications used as case studies. Some mitigation techniques presented in the literature are reviewed and discussed. The result of the preliminary numerical design is compared with results of measurements on real installations, showing that the available methods are mature instruments for the design of mitigation measures.

The application of a trigeneration system to fruit conservation food-industry is studied. The economic and environmental benefits of the installation are analyzed by means of multi-objective optimization which takes into account operational costs of the system and greenhouse gas emissions. A contrast between the minimization of these two objectives is shown and thus different operative strategies are devised. Taken a practical case of the trigeneration load required by an industrial site in north-west of Italy where measurements of load profiles are available, different combined heat and power engines with and without a thermal energy storage system are studied and results are discussed. General considerations about the advantages of the proposed solutions are also presented.

In this paper, numerical and analytical approaches for the study of busbar systems are analyzed and compared. In the first part of this paper, the multiconductor model (MC) is presented for studying a general busbar system and the equation are formalized for ldquocurrent-drivenrdquo and ldquovoltage-drivenrdquo problems. Afterward, the ldquoMC methodrdquo has been applied for solving a ldquocurrent-drivenrdquo problem related to an industrial busbar system. The evaluation of current distribution and electrodynamic forces of the system has been compared with the one obtained by using a classical finite-element method. Finally, the total current in the massive conductors of the system has been compared with the measurement. In the second part, an analytical approach for evaluating the electrodynamic forces is presented. The ldquoadjacent massive conductorsrdquo configuration considered in the IEC standard 865/93 is fully detailed and the ldquononadjacent massive conductorsrdquo configuration, not considered in the standard, has been developed.

Abstract This paper deals with the application and optimization of active loops for the mitigation of the magnetic field generated by complex sources, especially MV/LV substations. Various active-loop configurations are proposed, which are analyzed in several regions located close to a particular MV/LV substation, and the optimum geometry and location of the loops are obtained together with the optimum current (magnitude and phase) to be injected into the loops. All this is performed by means of a genetic algorithm in order to reduce the average magnetic field inside the target volume (inspection volume) to the minimum. The performance of the proposed active loops is compared with that obtained via other well-known mitigation technique, such as conductive/ferromagnetic passive shields. The main results are analyzed, and the differences, in terms of performance, between the two shielding techniques, and their proper application to MV/LV substations, are highlighted.

Abstract This paper deals with a new concept of technology for the mitigation of the magnetic field produced by underground power lines called “High Magnetic Coupling Passive Loop” (HMCPL). The working principle of this technique is the creation of a current with the same amplitude but opposite phase for each source conductor, in order to nullify the magnetic field in a specified region. Since the number of thermal sources in the shielding region is roughy doubled, the aim of the paper is the investigation of the thermal behavior of HMCPL directly buried in the ground, both in transient and in steady-state conditions. The study is carried out with simulations in order to verify any possible configurations of the shield. Results confirm that HMCPL is a safe technology which does not modify the thermal behavior of the power line.