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[en] Highlights: • State of the art and past experimental investigations were describe. • Feeding flow rate effect on SE-SR performance was investigated. • S/C and particle size effects on SE-SR performance were investigated. • CO_2 capture capacity of M3 sorbent was compared to the state of the art. • Operating conditions of SE-SR process with M3 sorbent were optimized. - Abstract: The development of a sustainable power generation using fossil fuels will be strongly encouraged in the future in order to achieve European targets in terms of CO_2 emissions. In this context, sorption-enhanced steam reforming (SE-SR) is a promising process that can be implemented as a CCS pre-combustion methodology. Regarding conventional catalyst-CO_2 sorbent materials, main challenges concern the development of innovative CO_2 sorbents with higher stability and regeneration temperature lower than CaO one. In recent study, a high-performance material based on incorporation of CaO particles into calcium aluminates was developed by authors exhibiting high sorption capacity and stability in multi cycle process. In this study, such a sorbent was packed, together with the catalyst, in a fixed bed reactor and tested in multi-cycle SE-SR process optimizing the operating conditions. Sensitivity analysis was carried out in reference to feeding flow rate, steam to carbon molar ratio and material particle size. The innovative sorbent exhibits, in optimized process, significant performance improvements (in terms of H_2 purity and total CO_2 amount adsorbed in each carbonation cycle) respect similar approaches available in the technical literature
[en] A method of thermo-economic analysis for the choice of optimal thermodynamic parameters of steam bottoming cycles in combined cycle power plants is presented. By keeping the thermodynamic aspects separated from the economic aspects, this method allows designers to easily perform a sensitivity analysis of the change in the economic parameters
[en] Highlights: • A new reactor solution based on rotating fixed beds was presented. • The preliminary design of the reactor was approached. • A CFD model of the reactor, including CO_2 capture kinetic, was developed. • The CFD model is validated with experimental results. • Sorbent exploitation increasing is possible thanks to the new reactor. - Abstract: In future decarbonization scenarios, CCS with particular reference to post-combustion technologies will be an important option also for energy intensive industries. Nevertheless, today CCS systems are rarely installed due to high energy and cost penalties of current technology based on chemical scrubbing with amine solvent. Therefore, innovative solutions based on new/optimized solvents, sorbents, membranes and new process designs, are R&D priorities. Regarding the CO_2 capture through solid sorbents, a new reactor solution based on rotating fixed beds is presented in this paper. In order to design the innovative system, a suitable CFD model was developed considering also the kinetic capture process. The model was validated with experimental results obtained by the authors in previous research activities, showing a potential reduction of energy penalties respect to current technologies. In the future, the model will be used to identify the control logic of the innovative reactor in order to verify improvements in terms of sorbent exploitation and reduction of system energy consumption.
[en] Highlights: • Biogas-to-electricity conversion through Solid Oxide Fuel Cell is investigated. • Two solutions are compared for biogas-to-electricity conversion. • Direct feeding by partially upgraded biogas meets with fuel cell long operation. • Best energy and exergy performances are obtained with an innovative system-design. • A sensitivity analysis on the process parameters determines its convenience margin. - Abstract: Aiming at designing biogas-to-electricity advanced systems, Solid Oxide Fuel Cells are promising candidates. They benefit from scalability on plant sizes that suit anaerobic digesters potentialities. For biogas-Solid Oxide Fuel Cells applications, the implementation of an external pre-reformer is usually considered. However, the possibility to perform direct fuel feeding to the Solid Oxide Fuel Cell offers new opportunities towards the realization of lean systems, which are competitive especially on small-scale installations (i.e. on-farm biogas-to-electricity conversion). In this frame, scientific literature is rather poor and, to cover this gap, system simulations are called for two reasons: first, to demonstrate the potential efficiency gain of new concepts; second, to provide a meaningful support for long-term experimental investigation on Solid Oxide Fuel Cells operated upon direct feeding of unreformed biogas. For that, the current study compares two system designs for biogas utilization into Solid Oxide Fuel Cells. The conventional one realizes biogas steam reforming prior the fuel cell, while the novel concept is based on direct feeding of partially upgraded biogas by means of carbon dioxide-separation membranes. As main outcome of the study, the system equipped with carbon dioxide-separation membranes achieves better performances than its conventional competitor does, scoring 51.1% energy efficiency and 52.3% exergy efficiency (compared to 37.2% and 38.6% respectively exhibited by the reformer-based system). Because of the lack a high endothermic process steps, the membrane-based system is also convenient whether heat recovery is required, producing a combined heat-and-power efficiency of 74.8% versus 47.0% obtained in the other system. Moreover, the results of a sensitivity analysis of the impact of membrane and reforming operating parameters on the overall system performances justify the convenience of adopting the solution of biogas direct feeding. Even in the hypothesis of a poorly performing membrane and an optimized reformer, the membrane-based system exhibits a gain in the system energy and combined heat-and-power efficiency of 25.2% and 34.9% respectively, with regard to the reforming-based concept. The forcefulness of this result is reinforced by a preliminary evaluation of capital expenditures, which represents a further economic advantage beside the economic revenue coming from a higher energy conversion efficiency.
[en] Penetration of renewable energy is strongly slowed by its characteristic intermittency and fluctuating trend and by the inadequacy of electricity networks. These issues can be addressed through the development of new or improved storage technologies with higher performance, availability, durability, safety and lower costs. In the present work, micro-grids characterized by the presence of different subsections including renewable plants coupled with batteries storage solution are investigated through the development of a suitable code. Several design conditions and features, related to RES plant, storage system and users, were considered in order to realize a sensitivity analysis aimed to examine, on a yearly base and with one minute time step, interactions among the different micro-grid subsections and to identify the best solutions from both economic and energy point of views. - Highlights: • Storage systems coupling to RES plants is investigated for micro-grids. • Interactions between RES plants, storage batteries and users are analyzed. • Self-consumption increases with storage installation. • Investment pay-back analysis is performed varying plant configurations. • Pay-back reduction up to 30–40% for new RES/Storage integrated installations.
[en] Many kinds of fault detection systems for reciprocating engines have been proposed. Mostly these systems rely on dynamic analysis of engine behavior or chemical analysis of exhaust. Very few systems achieve a real on line diagnosis. On the other hand, land based and aeronautic turbine power plants are mostly equipped with thermodynamic fault detection systems (gas path analysis). The authors are trying to design a simple, cheap and reliable diesel engine monitoring system, performing a real time, continuous service. State of the art dynamics, gas path analysis and some new ideas will be used. Here we present the first part of this project, dealing with thermodynamic engine analysis. Soon we hope to present also a different approach, relying on engine dynamic analysis. This paper is mainly concerned with diesel engines. It seems reasonable to concentrate ourselves on large and based engines, whose size and cost justify the implementation of a fault detection system. Anyway many results are fairly general, and could be used for smaller engines, like vehicle engines, and other cases in which large number of units can lower costs
[en] A performance and economic analysis of an existing combined heat and power plant with an internal combustion engine and district heating for the Faculty of Engineering of the University of Perugia is presented. Results of the first 15 months of operation are shown and discussed with reference to daily performance of the combined heat and power plant, which shows how electric efficiency is only slightly affected by ambient temperature. A comparison of evaluation indexes for cogeneration plants is made with particular attention to the energy index (EI) which is used by Italian legislation as an evaluation parameter to decide if a combined heat and power plant can have access to financial benefits.A cost-benefits analysis based on the first year of operation was made to decide eventual changes in heat and power management, in order to reduce pay-back period and increase the internal rate of return of the investment. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)
[en] A research activity has been initiated to study the development of a diagnostic methodology, for the optimization of energy efficiency and the maximization of the operational time in those conditions, based on artificial intelligence (AI) techniques such as artificial neural network (ANN) and fuzzy logic. The diagnostic procedure, developed specifically for the cogeneration plant located at the Engineering Department of the University of Perugia, must be characterized by a modular architecture to obtain a flexible architecture applicable to different systems. The first part of the study deals with the identifying the principal modules and the corresponding variables necessary to evaluate the module 'health state'. Also the consequent upgrade of the monitoring system is described in this paper. Moreover it describes the structure proposed for the diagnostic procedure, consisting of a procedure for measurement validation and a fuzzy logic-based inference system. The first reveals the presence of abnormal conditions and localizes their source distinguishing between system failure and instrumentation malfunctions. The second provides an evaluation of module health state and the classification of the failures which have possibly occurred. The procedure was implemented in C++
[en] Highlights: • Steam gasification of charcoal pellet has been performed. • Hydrogen concentration of about 58%v has been measured. • Steam gasification can be sustained by burning pyrolysis reformed volatiles. • The energy efficiency of producing hydrogen from charcoal is about 25%. • Hydrogen yield is about 30 g/kg of biomass pellet. - Abstract: The University of Perugia has developed an Integrated Pyrolysis Regenerated Plant, which can be integrated with a steam gasification plant to produce hydrogen from charcoal. The advantage of using charcoal instead of biomass in steam gasification is represented by the reduction of tar production. To verify this new plant concept an experimental campaign was performed feeding water into a hot char bed. An interesting gas composition was measured, with hydrogen concentration equal to 58.26% in volume. Based on the mass and energy balance of the experimental tests a plant based on a pyro-reforming stage, coupled with a steam gasification was designed, focusing the analysis on heat integration between the pyro-reforming and the steam gasification process. The results show that the pyrolysis process can entirely provide the heat of reaction of the pyrolysis itself, the reforming stage and the steam gasification stage. A yield of 0.03 kg of hydrogen for 1 kg of biomass can be achieved.
[en] Highlights: ► A vibration analysis of an internal combustion engine was carried out. ► Sound intensity and surface vibration velocity measurements have been employed. ► The radiation factor of the engine vibrating surfaces was determined. ► The radiation factor can be applied for diagnostic scopes. -- Abstract: The present work deals with the problem of monitoring and diagnosis, through non-intrusive methodologies, of stationary internal combustion engine, with particular attention to the cogenerative 1 MW unit installed at the Engineering Faculty of the University of Perugia. Specifically, acoustic and vibrational measurements have been performed to correlate the engine functional status (and therefore the vibration of mechanical surfaces) with the acoustic emissions features through the characteristic radiation factor. The ISO/TS 7849 normative for the correlation of vibration and acoustic measurement has been employed.