Theoretical analysis of a pure hydrogen production separation plant for fuel cells dynamical applications

This article proposes a mathematical model and develops the numerical simulation of a single stage hydrogen production-separation process during transient behaviour, suited for proton exchange membrane (PEM) fuel cell (FC) applications. Methanol reforming process is performed in a commercial catalytic membrane reactor (CMR), filled with a commercial ZnO-CuO, alumina supported catalyst. The permeate hydrogen is accumulated in a reservoir volume (buffer) connected to the permeate side. This configuration was studied in order to avoid the feed back control of the reactor feeding, even when transient power loads to the cell are applied. By numerical simulation, we verified that the system comprised by the CMR and the PEM, with an appropriate constant reactor feeding flow, is always self-sustaining so that the hydrogen demand by the FC can be satisfied at all power regimes. The achievement of this goal was obtained by redistribution of the hydrogen produced in the reactor between the buffer and the exhaust tail gases. Only the control of two independent variables of the system, such as reactor temperature and pressure, are needed, therefore, the configuration proposed here results in a simplified approach to the control strategy for the entire system. We apply the theoretical analysis to a pilot plant designed and assembled at the University of Rome "La Sapienza", in order to verify its functional parameters and the theoretical performance of the system before its real operation. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Off-normal and failure condition analysis of the MITICA negative-ion accelerator

The negative-ion accelerator for the MITICA neutral beam injector has been designed and optimized in order to reduce the thermo-mechanical stresses in all components below limits compatible with the required fatigue life. However, deviation from the expected beam performances can be caused by \u201coff-normal\u201d operating conditions of the accelerator. The purpose of the present work is to identify and analyse all the \u201coff-normal\u201d operating conditions, which could possibly become critical in terms of thermo-mechanical stresses or of degradation of the optical performances of the beam

The Full-Size Source and Injector Prototypes for ITER Neutral Beams

The development of the NBI systems for ITER requires unprecedented parameters (40A of negative ion current accelerated up to 1MV for one hour) so that a test facility is in the final phase of construction at Consorzio RFX (Padova, Italy), housing two experiments. A full-size negative ion source, SPIDER, aims at demonstrating the creation and extraction of a D-/H- current up to 50/60A on a wide surface (more than 1m2) with uniformity within 10 %. The second experimental device is the prototype of the whole ITER injector, MITICA, aiming to develop the knowledge and the technologies to guarantee the successful operation of the two injectors to be installed in ITER, including the capability of 1MV voltage holding at low pressure. The key component of the system is the beam source, whose design results from a trade-off between requirements of the optics and real grids with finite thickness and thermo-mechanical constraints due to the cooling needs and the presence of permanent magnets. Numerical simulations are a necessary supplement to the experimental effort to optimise the accelerator optics and to estimate heat loads and currents on the various surfaces. In this paper the main requirements for ITER NBI will be discussed. The design and the status of the main components and systems will be described. Particularly a review of the accelerator physics and a comparison between the designs of the SPIDER and MITICA accelerators are presented. Complex network theory will be applied to the NBI system in order to identify the hidden functional relationships and the most important parameters for the operation. \ua9 2016 The Japan Society of Plasma

Optimization of the electrostatic and magnetic field configuration in the MITICA accelerator

MITICA (Megavolt ITER Injector Concept Advancement) is a test facility for the development of a full-size heating and current drive neutral beam injectors for the ITER Tokamak reactor. The optimized electrostatic and magnetic configuration has been defined by means of an iterative optimization involving all the physics and the engineering aspects. The acceleration grids have been designed considering optical performances and mechanical constraints related to embedded magnets, to cooling channels, to the grid stiffness and manufacturability. A combination of "local" vertical field and horizontal "long range" field has been found to be the most effective set-up for ion extraction, beam focusing and minimization and equalization of thermo-mechanical loads and minimal number of electrons exiting the accelerator

1 MV power supplies integration issues in MITICA experiment, the ITER Heating Neutral Beam Injector prototype

MITICA, the full scale prototype of ITER Heating Neutral Beam Injector required to heat up ITER plasma with 16.5 MW injected power, is under realization at the Neutral Beam Test Facility (NBTF) in Padova (Italy) with the contributions of JApanese and EUropean Domestic Agencies (JADA and EUDA, respectively). The objective of MITICA is to produce a 16.5 MW neutral beam, obtained by accelerating negative Deuterium ions up to 1 MeV for a total ion current of 40 A and then neutralized.MITICA Power Supply (PS), installed from 2016 to 2019, includes several non-standard equipment, with ratings well beyond the present industrial standard for insulation voltage level (-1 MVdc) and dimensions:- the Acceleration Grid Power Supply (AGPS), composed of five DC Generators (DCG) rated for -200kVdc each, connected in series to produce -1 MVdc acceleration voltage;- the Ion Source and Extraction Power Supply system (ISEPS);- the large air insulated Faraday cage (High Voltage Deck1, HVD1) hosting ISEPS and connected to the Transmission Line (TL) through an air-to-SF6 Bushing (High Voltage Bushing Assembly, HVBA);- a 100 m gas (SF6) insulated TL, connecting AGPS and ISEPS to the beam source installed inside the vacuum vessel through- the SF6-to-vacuum HV Bushing (HVB).The definition of the interfaces both between components supplied by the different DA’s and towards the buildings has been studied and finalized as far as possible during the design phase. Nevertheless, during the installation phase some issues emerged and had to be solved, minimizing modifications of the components already manufactured. The paper deals with the experience gained during the installation activities, focusing on solutions to interface the aforementioned equipment with NBTF buildings according to the stringent dimensional requirements and to the electrical insulation issues of the TL from the buildings. In particular, the solutions adopted to realize the electrical and mechanical interfaces between the TL and the HVBA are described in detail