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ATENEA4SME: A Tool for Self-Evaluation of Energy Efficiency and Audit Support In Industrial SME
No full textThe limited diffusion and the lack of effective tools for carrying out energy audits in small and medium-sized enterprises (SMEs) are significant barriers to promote energy efficiency in the Italian production sector, which includes industry, tertiary sector and transportation. ATENEA4SME (Advanced Tool for Energy Audit for SMEs) is designed to assist SMEs in the self-evaluation of energy consumption, to support energy audit in SME and to identify and foster energy-efficiency investments. The tool is characterized by automatic procedures differentiated by NACE nomenclature and elaborates suggestions for energy efficiency investments by means of a mathematical model in which multi-criteria analysis and a questionnaire are considered. This article will provide a detailed description of the tool, highlighting and describing the Sections and the steps to obtain the final overview of the energy consumption of the enterprise under investigation and the opportunities of energy saving. The tool contributes to remove barriers to the development of energy-efficiency measures, both from a technical and economic point of view. In the paper, some application cases, focused on a comprehensive analysis of energy efficiency investments, have been included
C-HIL Implementation of Cascaded Multilevel Inverter for Vertical Stabilization and Radial Control Power Supplies of Divertor Tokamak Test
No full textThis paper deals with a Controller Hardware in the Loop (C-HIL) implementation of a cascaded multilevel inverter to supply the two Divertor Tokamak Test (DTT) equatorial in-vessel coils for plasma Vertical Stabilization (VS) and fast Radial Control (RC). The power converters suitable to drive the VS coils are medium-voltage inverters capable of delivering high-output currents. The adopted converter topology to power the VS coils is based on cascaded H-bridge IGBT converters implemented in a modular way. The number of 7 modules used in this paper is reduced compared to a previous solution with 8 modules. Every H-bridge converter employs Pulse-Width Modulation (PWM) on a switching leg and an unfolder technique in the other switching leg to attain the requested output current. The unfolder technique facilitates the minimization of the switching losses. The proposed schemes and the results showcased are tailored to the requirements of DTT. In this paper, the complete description of the hardware system, the current control, and C-HIL results are reported
A new dry deposition model implemented in CALPUFF code to simulate contamination of radionuclides released into atmospheric environment post-nuclear accidental event
Get PDFLong-range transport and deposition analyses of 137Cs following a hypothetical incident at Gösgen nuclear power plant are studied by using CALMET-CALPUFF model system. Comparisons are performed with results obtained from a version modified of CALPUFF using a new dry deposition velocity model. This model is based on a combination of aerodynamic resistances and considers local features of the mutual influence of inertial impact and turbulent processes. The results show that the modified CALPUFF code seems to be an appropriate tool for performing impact assessments on long-range transport in complex terrain contexts or to support preparedness and response capabilities for nuclear and radiological accidents
Thermal-Hydraulic Characterization and Numerical Modeling with RELAP5 Code of ATHENA Secondary Loop
No full textAmong the envisaged experimental infrastructures supporting Advanced Lead Fast Reactor European Demonstrator (ALFRED) reactor development, the FALCON [Fostering ALfred CONstruction] consortium identified the Advanced Thermo-Hydraulics Experiment for Nuclear Application (ATHENA) as one of the facilities to address the pool of thermal-hydraulic challenges and demonstrate the feasibility of the revised ALFRED configuration, along with the thermal-hydraulic performances of its main components. ATHENA is a large pool-type lead-cooled multipurpose experimental facility featuring a large-sized vessel (3.2-m diameter and 10-m height), conceived to host almost 800 tons of lead to test ALFRED-relevant scaled components. The test section to be installed in the main vessel includes an electrically heated core simulator, made of seven fuel assemblies, which delivers to the primary coolant a nominal thermal power of 2210 kW; a main coolant pump for lead circulation; and a countercurrent shell-and-tube main heat exchanger, of which the tube bundle is fed by pressurized water by a dedicated secondary circuit. This work presents the numerical model of ATHENA along with thermal-hydraulic characterization of the facility using the system code RELAP5/Mod3.3, properly modified to include the thermophysical properties of heavy liquid metals. After the characterization of the steady state representative of the Stage 3 foreseen for the ALFRED staged approach, results of a numerical sensitivity analysis aimed at defining the most suitable procedure for the shutdown transient of the facility are presented
Laser-driven ion and electron acceleration from near-critical density gas targets: Towards high-repetition rate operation in the 1 PW, sub-100 fs laser interaction regime
No full textIon acceleration from gaseous targets driven by relativistic-intensity lasers was demonstrated as early as the late 1990s, yet most of the experiments conducted to date have involved picosecond-duration, Nd:glass lasers operating at low repetition rate. Here, we present measurements on the interaction of ultraintense (≈1020Wcm-2, 1 PW), ultrashort (≈70fs) Ti:Sa laser pulses with near-critical (≈1020cm-3) helium gas jets, a debris-free targetry with the potential for future compatibility with high (≈1 Hz) repetition rate operation. We provide evidence of α particles being forward accelerated up to ≈2.7-MeV energy with a total flux of ≈1011sr-1 as integrated over >0.1-MeV energies and detected within a 0.5-mrad solid angle. We also report on on-axis emission of relativistic electrons with an exponentially decaying spectrum characterized by a ≈10-MeV slope, i.e., five times larger than the standard ponderomotive scaling. The total charge of these electrons with energy above 2 MeV is estimated to be of ≈1nC, corresponding to ≈0.1% of the laser drive energy. In addition, we observe the formation of a plasma channel, extending longitudinally across the gas density maximum and expanding radially with time. These results are well captured by large-scale particle-in-cell simulations, which reveal that the detected fast ions most likely originate from reflection off the rapidly expanding channel walls. The latter process is predicted to yield ion energies in the MeV range, which compare well with the measurements. Finally, direct laser acceleration is shown to be the dominant mechanism behind the observed electron energization
Power-to-Gas: Process analysis and control strategies for dynamic catalytic methanation system
No full textThe methanation process, or Sabatier process, allows carbon dioxide and carbon monoxide to be hydrogenated into methane, which can be subsequently injected (once the gas grid specifications have been respected) into the gas network infrastructures already present in Europe. This process can be effectively adopted to convert captured CO2 streams from power plants or hard to abate plants by using green hydrogen from renewable-driven water electrolysis. The technical aspects of concern in the methanation process are certainly the strong exothermicity of the process, with consequent possible generation of hotspots along the entire catalyst bed and the management of reaction heat through thermal recovery. These peculiar aspects influence the choice of construction materials and geometry of the methanation reactor, operating parameters, cooling system, type of catalyst/support and the initial conditions of the feed. In particular, the generation of hotspots influences the local kinetic reaction in the methanation reactor, the diffusional limits of hydrogen and carbon dioxide inside the catalyst and the chemical-physical characteristics of the catalyst bed. The present work reports a first scale-up of the Sabatier process, developed in Aspen Plus simulation environment, with the following characteristics: reactor size to process 925 Nm3/h, (750 hydrogen and 175 carbon dioxide), at 15 bar and 250 °C. After the implementation in the steady state, a dynamic simulation is performed to carry out a transient study of the entire plant. In particular, the attention is focused on the variation in the hydrogen load, produced by electrolysis from the energy surplus from renewable sources. Considering the variable nature of the power flow supplied to the electrolyser and therefore any shutdown and cold start-up phases of this equipment, the following load variation scenarios for the Power to Gas (PtG) system are simulated: −5%, +5% and −30 % molar flow rate of incoming hydrogen, compared to steady conditions used in the preliminary design of the equipment. The study highlights how the cooled reactor configuration is more performing and characterized by a lower number of reactors in series (2 reactors) when compared to the adiabatic configuration (5 reactors). Furthermore, in the cooled reactor configuration the control system is able to respond more quickly to load variations compared to that designed for the adiabatic case, although the latter is mostly adopted from the industrial viewpoint due to temperature control issues. Moreover, the control system manages to respond to load variations by bringing the values of interest (gas grid residual concentration of hydrogen and carbon dioxide, Wobbe index) into the target intervals
Helical-shaped double wall tubes solution for the breeding zone cooling in the WCLL breeding blanket
No full textOne of the two most promising Breeding Blanket (BB) concepts to be chosen as driver design of the EU-DEMO fusion reactor is the Water-Cooled Lead Lithium (WCLL) BB. A crucial point of this key component is the cooling of the BB structural elements and of the Lithium-Lead alloy, used as neutronic multiplier and Tritium breeder. Indeed, the high neutronic flux needed for breeding implies high volumetric power affecting the Breeding Zone (BZ) materials. The current BB layout employs water-cooled Double Wall Tubes (DWTs) with a C-shaped configuration for the BZ cooling. Despite the WCLL BB have reached a mature design in the last years, some open issues remain to be solved to increase the reliability and performance of this technology. The present paper describes a promising upgrade of the BZ cooling layout adopting helical-shaped DWTs. This solution has the potential to increase the BB reliability, cooling performance, Tritium Breeding Ratio and cooling water flow-path simplicity. The new proposed layout is described in the paper, along with results of CFD analyses carried out to investigate the new cooling performances in BZ. Advantages and drawbacks with respect to the current BB layout have been also highlighted in the paper
Protected Loss-of-Flow Accident in a HLM Pool Facility: Long-Term Cooling Experiment
No full textSince the 2000s, the development of Generation-IV fast reactors cooled by heavy liquid metals (HLMs) has been pursued by several research activities and projects, many of which are co-funded by the European Commission. One of the key points of HLMs regards their good neutronic and thermophysical properties, allowing for the of design cores with a high pitch-to-diameter ratio. In terms of passive safety, with a properly designed configuration, it is possible to increase the system capability to remove the decay power in a natural circulation regime, reducing active safety systems involvement. Such a safety-related aspect has been experimentally investigated at the ENEA Brasimone Research Center within the European Union co-funded Euratom H2020 SESAME project. An experimental campaign reproducing protected loss-of-flow accident (PLOFA) scenarios has been executed on CIRCE, a lead-bismuth eutectic-cooled pool-type facility reproducing in relevant scale the main components of HLM-cooled fast reactors. A test section named HERO has been installed in the CIRCE main vessel, hosting a double-wall bayonet tube steam generator scaled 1:1 in length with respect to the one envisioned for the ALFRED reactor. The tests reproduce the loss of primary coolant flow, while the power supplied by the heating source decreases according to a characteristic decay heat curve. The feedwater in the secondary system is regulated to operate the main steam generator as a decay heat removal (DHR) system. This paper presents the PLOFA transient reproducing the worst case, where the steam generator feedwater is suddenly stopped, simulating the full loss of the heat sink (no DHR). The main phenomena occurring during the transition from forced to natural circulation are presented and discussed. The experiment shows that, despite the loss of the forced circulation regime in the primary loop and the full loss of the heat sink, the entire system is still capable of operating safely, assuring an effective long-term cooling, as long as the thermal heat losses from the main vessel balance the decay power supplied by the heating source
Decision Support System Driven by Thermo-Complexity: Scenario Analysis and Data Visualization
No full textThe present modelling aims to construct a computational information representation system useful for decision support system (DSS) solutions in the realization of intelligent systems or complex systems analysis solutions. Starting from an n-dimensional space (with n ≥ 7) represented by problem variables (referred to as CSF—Critical Success Factors), a dimensional embedding procedure is used to transition to a two-dimensional space. In the two-dimensional space, thanks to new lattice motion algorithms, the decision support system can determine the optimal solution with a lower computational cost based on the decision-maker’s preferences. Finally, thanks to an algorithm that takes into account the hierarchical order of importance of the seven CSFs as per the expert’s liking or according to his optimization logics, a return is made to the n-dimensional space and the final solution in the original space. As we will see, the starting and ending states in the n-dimensional space (referred to as micro-states) when projected into the two-dimensional space generate states (referred to as macro-states) which are degenerate. In other words, the correspondence between micro-states and macro-states is not one-to-one, as multiple micro-states correspond to one macro-state. Therefore, in relation to the decision-maker’s preferences, it will be the responsibility of the decision support system to provide the decision-maker with the micro-state of interest in the n-dimensional space (dimensional emergence procedure), starting from the obtained optimal macro-state. This result can be achieved starting from a flat chain of sensors capable of measuring/emulating certain specific parameters of interest. As we will see, it emerges that by considering random–exhaustive rolling value paths in order to track and potentially intervene to rebalance a dynamic system representing the state of stress/sensing of a system of interest, we are using the most general and, therefore, complex hypotheses of ergodic theory. In this work, we will focus on the representation of information in n-dimensional and two-dimensional spaces, as well as construct evaluation scenarios. We will also show the results of the decision support system in some cases of specific interest, thanks to a specific lattice motion algorithm of the realized decision-making environment
Shake Table Tests of a Bridge Model with Different Seismic Isolation Devices
No full textThe importance of improving the surveillance and maintenance of road infrastructures has become an issue in most countries in the world. Actually, most bridges were built several years ago, when traffic loads were different from the current ones and seismic actions were often neglected. Today, one of the main goals is the identification of suitable seismic retrofit interventions for existing bridges. A scaled span of a real viaduct was tested on a shake table in order to study the efficiency of different isolation systems, composed of HDRBs and SDs or CSSs, in comparison with the original rubber support systems. Different sensors were used to measure accelerations and displacements of the structure under increasing seismic input and to point out the different experimental behavior of the seismically isolated configurations. HDRBs + SDs allowed to obtain significant reduction in accelerations and no residual displacements, while the performances of CSSs were improved by means of lubrication