181 research outputs found
PV-Electrolyzer plant: models and optimization procedure
No full textThe work focused on the analysis of the connection between a photovoltaic (PV) plant and an electrolyzer for hydrogen production. On the basis of PV plant and electrolyzer experimental data, the effectiveness of the models adopted in the simulation program has been verified in order to choose the best model and, eventually, modify some parameters.
By running the simulations, the procedure to optimize the PV plant and the electrolyzer combination has been established. In fact, the simulation results might be considered to size an electrolyzer as small as possible, which is able to exploit up to the maximum power actually produced by the PV plant during a working year. This criterion allows minimizing the overall plant costs. Furthermore, the possibility of deleting the Maximum Power Point Tracker (MPPT) and the DC/DC converter has been analyzed. On the basis of the obtained results, this opportunity is preferable to avoid the energy losses in the power control system; and it is convenient even from an economic point of view, considering that the electronic devices costs are comparable with the PV plant ones
A new method for collecting vehicle behaviour in daily use for energy and environmental analysis
No full textThe power supply, fuel consumption, and noxious emissions of a vehicle depend on the use that is made of it. Usually [1] only the driving cycle is considered to be a sufficient way to gauge a vehicle’s usage. It is not, however, enough. Experimental tests have proved that, while similar driving cycles entail similar power demand, fuel consumption and emissions differ. In addition, a driving cycle, usually a synthesis [1–7] of several cycles collected experimentally, represents neither a specific link of the road network nor a specific user. Vehicle use must, accordingly, be described by something more comprehensive than the driving cycle, and this might be called the ‘use cycle’, for which a definition needed to be found. For a definition of the use cycle, all possible factors influencing vehicle emissions had to be examined. It was thus necessary to develop a tool both for gathering data that might reveal a different use of the vehicle and for identifying factors that might have an influence on emissions. The easiest, cheapest, and most versatile way to collect real data on the use of a vehicle is to use the vehicle’s own sensors connected to the on-board diagnostic (OBD-2) port. Readings from a GPS can provide some characteristics related to the vehicle’s position. This paper describes the development of a tool for collecting real-time OBD and GPS information. The acquisition tool was validated by a number of tests on a dynamometer chassis and differences are never higher than 3 per cent (e.g. on speed max 2 km/h). The first result obtained on vehicle usage is that driver behaviour influences throttle position independently of the driving cycle. Even with similar driving cycles, the accelerator pedal position and its variations turned out to be heavily different, suggesting a new definition of driver behaviour linked to the way the driver uses the pedals. Such pedal movement does have an influence on the air–fuel ratio, which remains stable around the stoichiometric value with ‘calm’ use of the accelerator, while it changes continuously, never becoming stoichiometric, with ‘aggressive’ accelerator behaviour. The continuous use of the developed tool on large fleets of vehicles will allow progress along this path and help define use cycles that may then be used by car manufacturers to design vehicles more efficient in their different uses and by the authorities to force more stringent homologation rules
A technological solution for everywhere energy supply
No full textThe hydrogen economy is still at the beginning, but society innovation, and the market push inexorably toward hydrogen, inspiring the idea to build an energy-integrated system that can satisfy, in an independent way, the energy needs of small-sized consumers. The technologies used for the system design are already available in the market and, at least for the standard Solutions, sufficiently mature. The innovation consists of an integration, optimization, and industrialization of this modular system, which is an electric zero-emissions generator giving 3.5 kW(p) as an output power This is the only system able to produce its own fuel, guaranteeing renewable and clean energy., available where and when you want. This system is constituted by a polymer membrane electrolyzer, a metal hydrides tank (which absorbs and desorbs hydrogen), and a polymer fuel cell (PEM). The system modularity can also satisfy higher energy requirements, and the low-pressure hydrogen storage system through metal hydrides guarantees the system safety.
(ASME Transactions
MCFC and microturbine power plant simulation
No full textThe consistent problem of the CO2 emissions and the necessity to find new energy sources, are motivating the scientific research to use high efficiency electric energy production's technologies that could exploit renewable energy sources too. The molten carbonate fuel cell (MCFC) due to its high efficiencies and low emissions seems a valid alternative to the traditional plant. Moreover, the high operating temperature and pressure give the possibility to use a turbine at the bottom of the cells to produce further energy, increasing therefore the plant's efficiencies. The basic idea using this two kind of technologies (MCFC and microturbine), is to recover, via the microturbine, the necessary power for the compressor, that otherwise would remove a consistent part of the MCFC power generated. The purpose of this work is to develop the necessary models to analyze different plant configurations. In particular, it was studied a plant composed of a MCFC 500 kW Ansaldo at the top of a microturbine 100 kW Turbec. To study this plant it was necessary to develop: (i) MCFC mathematical model, that starting from the geometrical and thermofluidodynamic parameter of the cell, analyze the electrochemical reaction and shift reaction that take part in it; (ii) plate reformer model, a particular compact reformer that exploit the heat obtained by a catalytic combustion of the anode and part of cathode exhausts to reform methane and steam; and (iii) microturbine-compressor model that describe the efficiency and pressure ratio of the two machines as a function of the mass flow and rotational regime. The models developed was developed in Fortran language and interfaced in Chemcad© to analyze the power plant thermodynamic behavior. The results show a possible plant configuration with high electrical and global efficiency (over 50 and 74%). © 2006 Elsevier B.V. All rights reserved
Social Impact Method of Energy Analysis: improvements and results
No full textSIMEA (Social Impact Method of Energy Analysis) is a new methodology to evaluate the environmental impact of energy systems. The SIMEA approach is based on "enlarged environment" definition, considering as environment not only the natural environment, but also the "human environment", with so including the economy structure, social organisation, cultural and historical aspects of the site.
The aim of SIMEA is to consider in an integrated way many possible effects on the environment (considering the definition of enlarged environment: nature economy, culture etc) of an energy system and evaluate the social consequences and effects as social impact.
SIMEA is being developed in an "iterative" way, so after the first development end validation in 1996, a second version SIMEA has been realised and tested by applying the improved methodology to the same site. The improvements and results are proving the methodology effectiveness and show that a possible computer aided application can be expected after analysis of the comparison between the two experiences.
IEEE Catalog n. OOCH37043, IEEE Library of Congress n. 99-6604
Oltre il PIL:nuovi indicatori di benessere e sostenibilità dello sviluppo
No full textThe paper underlines the importance of overcoming the estimation of GDP based on old criteria and try to identify a new way of evaluation on the basis of the literature reviewe
Process simulation of a neutral emission plant using chestnut's coppice gasification and molten carbonate fuel cells
No full textThe problem of CO2 emissions and the need to find new energy sources sources are pushing scientific research toward the use of high efficiency technologies for electric power generation that can exploit renewable energy sources - potentially neutral for the environment in terms of greenhouse gas emissions. Process simulations of advanced plants fed by biomass are a key step to develop renewable resources based high temperature fuel cell applications. The aim of this work is to predict the component behavior of a specific power plant mainly composed of a gasifier, a molten carbonate fuel cell (MCFC), and a micro-gas-turbine (mGT) and fed by chestnut coppice, waste available in great quantity in Central Italy, as well as in several other European regions. The gasifier produces a gas with a high content of hydrogen and low content of char and tar. This syngas is exploited by the MCFC-mGT plant. The mGT using the MCFC cathode outlet gases, shows through simulation to be able to operate the air compressor and produce further electrical power Particular models for the MCFC and gasifier have been developed in FORTRAN by the authors and then interfaced to commercial software (CHEMCAD©) to simulate the plant's thermodynamic behavior. The results show the possibility of an extremely interesting "carbon neutral" plant configuration with high electrical and global efficiency (respectively, 41% and 86%), exclusively based on the use of renewable resources (biomass). Copyright © 2008 by ASME
Search for the elusive magnetic state of hexagonal iron: The antiferromagnetic Fe71Ru29hcp alloy
No full textInelastic neutron scattering investigation of ball-milled FeSiB described as a magnetic nanoglass-like structure
No full textAn inelastic neutron scattering study has been carried out to assess the effects of mechanical milling treatments (10, 20 and 70 h) on an amorphous melt-spun FeSiB ribbon. Faint traces of crystallization were observed after 10 and 20 h milling by X-ray diffraction and Mössbauer spectroscopy and a minor fraction of bcc-Fe was clearly detected after 70 h. Whilst the neutron spectrum S(E) of the 10 h-milled sample, at temperature T = 300 K, does not differ from that of the precursor FeSiB ribbon, the area of the inelastic region of S(E) decreases more and more after 20 and 70 h milling. Moreover, in the samples milled for 20 and 70 h, also the area of the elastic region of the S(E) spectrum is definitely smaller than the one of the FeSiB ribbon. This is consistent with a reduction of the magnetic cross section upon milling and it agrees also with magnetization measurements. We interpret this behavior assuming that the milling treatment causes local alterations of the short-range atomic order within the amorphous phase, and hence of the precursor collinear ferromagnetic order, finally giving rise to a sort of magnetic nanoglass structure
- …
