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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] Nowadays the control of greenhouse gas is probably the most challenging environmental policy issue. Since CO2 is considered the major greenhouse gas (GHG) that contributes to the global warming, enforcing technological strategies aiming to avoid or reuse CO2 emissions becomes crucial, in order to mitigate GHG environmental impact. Currently, solutions conventionally adopted to this purpose are carbon capture and storage (CCS) technologies. In this context, instead, the followed strategy aims to further improvements in energetic conversion efficiency with related reduced specific CO2 emissions (per produced kWhe). Therefore, with particular reference to the electric power generation, this paper proposes an innovative energy conversion system, based on solid oxide fuel cell (SOFC), characterized by higher efficiency and reduced CO2 emission factor respect to an analogous conventional energy plant. In particular, the innovative solution consists of combining SOFC to methane dry reforming technology, while the conventional system refers to steam methane reforming-SOFC coupling. The innovative system performance up to 65% electric efficiency as cited in the paper, was validated through simulations carried out in Aspen Plus environment. - Highlights: • An innovative high efficiency plant with low CO2 emissions is presented. • The new solution combined SOFC to methane dry reforming technology (CDR–SOFC). • A comparison between CDR–SOFC and SMR–SOFC system was carried out in Aspen Plus. • CDR–SOFC efficiency is greater of 6.4% percentage points respect to SMR–SOFC. • A CO2 emission factor reduction of about 10% was achieved by CDR–SOFC plant
[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] 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] This paper contributes to the development of a thermo-dynamic model of the 1 MW cogenerative internal combustion engine (I.C.E.), including also an artificial neural network simulator of the electronic control module. Such a study is part of a more wide research activity, concerning the development of a diagnosis and monitoring system specifically for power plants. In particular, the engine model was realized to simulate the engine functioning also in the case of malfunctions and failures occurrence, taking in consideration the compensation effect operated by the regulation system. The complete model was tested in reference to several experimental conditions, in particular in a first phase relative to different values of the target electrical power and, subsequently, concerning the case of compressor fouling. Therefore it was validated both the thermo-dynamic model and the regulator operation in reference to the experimental data.
[en] With the rapid development of industry, more and more waste gases are emitted into the atmosphere. In terms of total air emissions, CO2 is emitted in the greatest amount, accounting for 99 wt% of the total air emissions, therefore contributing to global warming, the so-called 'Greenhouse Effect'. The recovery and disposal of CO2 from flue gas is currently the object of great international interest. Most of the CO2 comes from the combustion of fossil fuels in power generation, industrial boilers, residential and commercial heating, and transportation sectors. Consequently, in the last years' interest in hydrogen as an energy carrier has significantly increased both for vehicle fuelling and stationary energy production from fuel cells. The benefits of a hydrogen energy policy are the reduction of the greenhouse effect, principally due to the centralization of the emission sources. Moreover, an improvement to the environmental benefits can be achieved if hydrogen is produced from renewable sources, as biomass. The present paper provides an overview of the steam methane reforming (SMR) process and methodologies for performances improvement such as hydrogen removal, by selective permeation through a membrane or simultaneous reaction of the targeted molecule with a chemical acceptor, and equilibrium shift by the addition of a CO2 acceptor to the reactor. In particular, attention was focused on the sorption-enhanced steam methane reforming (SE-SMR) process in which sorbents are added in order to enhance the reactions and realize in situ CO2 separation. The major operating parameters of SE-SMR are described by the authors in order to project and then realize the innovative carbonation reactor developed in previous studies
[en] Highlights: → A zero-dimensional of a micro cogenerative (CHP) energy system based on a Proton Exchange Membrane fuel cell (PEMFC) has been developed. → The electrochemical model has been validated with experimental data. → The performances of this CHP system have been evaluated through a series of simulations. → An energy/exergy analysis of the simulation results has allowed to define the PEMFC optimal operating conditions. → The PEMFC optimal operating conditions detected are: 1 atm, 353.15 K and 100% RH. -- Abstract: The use of fuel cell systems for distributed residential power generation represents an interesting alternative to traditional thermoelectric plants due to their high efficiency and the potential recovering of the heat generated by the internal electrochemical reactions. In this paper the study of a micro cogenerative (CHP) energy system based on a Proton Exchange Membrane fuel cell (PEMFC) is reported. With the aim to evaluate the performance and then the feasibility of this non-conventional energy system, in consideration of thermal and electrical basic demand of a multifamily apartment blocks, a zero-dimensional PEMFC model in Aspen Plus environment has been developed. A simulations sequence has been carried out at different operating conditions of the fuel cell (varying temperature, pressure and relative humidity). Subsequently, on the basis of the obtained results, an energy/exergy analysis has been conducted to define the optimal operating conditions of the PEMFC that ensures the most efficient use of the energy and exergy inputs.
[en] The present work deals with the creation, on the basis of experimental data, of the regulation maps for the 1 MW cogenerative internal combustion engine (ICE) installed at the Engineering Faculty of Perugia University. The regulation logic mapping is necessary for the development of a thermodynamic model of the engine behaviour to simulate the effects of possible malfunctions occurrence, such as deterioration or fouling not directly experienced on the engine. Such a work is carried out as a part of a more general research activity concerning the development of a diagnosis system for the cogenerative plant. Therefore, a first phase of the present work relates to the experimental data gathering campaign and the consequent data analysis to individuate the characteristic parameters of regulation. In the second phase, instead, a neural simulator of the control logic was developed on the basis of the experimental data for the engine operation at full load (initially considered at 980 kW) and during transitory. Consequently, through such a simulator the regulation maps of the engine were determined considering the variation range of all the characteristic parameters. Finally, a more accurate analysis of the experimental data relative to the dependence of the produced electric power at regimen on the fuel valve position, encouraged the authors to develop a further neural simulator able to reproduce the regulation commands for different values of the target power set for the regimen operation. Consequently, also the regulation mapping was revised obtaining a synthetic representation of the regulation logic useful for the implementation in the thermodynamic model of the engine dynamic behaviour