• Energy Research

Abstract High energy efficiency SOFCs generators can be adopted for local and distributed micro-generation systems to promote the reduction of greenhouse gas emissions with their high fuel flexibility, long-term stability also at partial load and low noise. One of the main drawbacks for such generators, fed by biogenous gas is the impact of trace compounds on the anode compartment. For this reason, a gas clean-up section is mandatory. The effect of temperature and gas moisture was investigated through experiments on the removal performance of the tested sorbents. An increase in the operating temperature caused lower values of the maximum capacity of the adsorbent. The decrease of removal performance considering a humidified gas is connected to the interference of water in the pores of activated carbons. Biochar, compared to the other commercial sorbent materials showed the lowest removal performance, even if with activated biochar the adsorption capacity growth to commercially available materials. The highest adsorption capacity at 1% of the initial concentration was showed by commercial carbons with 1.75 mg/g for H2S and 20.4 mg/g for HCl. Experimental data were employed in a porous particle diffusion model to estimate the breakthrough time. Low values of errors validate the model in the first part of the breakthrough curve, even for competitive adsorption case.

Volatile Organic Compounds (VOCs) formed during anaerobic digestion of aerobically pre-treated Organic Fraction of Municipal Solid Waste (OFMSW), have been monitored over a 30 day period by a direct injection mass spectrometric technique: Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS). Most of the tentatively identified compounds exhibited a double-peaked emission pattern which is probably the combined result from the volatilization or oxidation of the biomass-inherited organic compounds and the microbial degradation of organic substrates. Of the sulfur compounds, hydrogen sulfide had the highest accumulative production. Alkylthiols were the predominant sulfur organic compounds, reaching their maximum levels during the last stage of the process. H(2)S formation seems to be influenced by the metabolic reactions that the sulfur organic compounds undergo, such as a methanogenesis induced mechanism i.e. an amino acid degradation/sulfate reduction. Comparison of different batches indicates that PTR-ToF-MS is a suitable tool providing information for rapid in situ bioprocess monitoring.

In recent years, research efforts on fuel cells have been addressed on the development of multifuel reformers with particular emphasis toward the potential use of non-traditional fuels. Among these, biogas is considered very promising to be used as syngas source for fuel cell system applications. The interest on this hydrogen source is focused mainly to supply high temperature fuel cells (HTFC). This paper reports a wide experimental research investigation on SOFC device supplied by syngas produced with different biogas reforming processes (steam reforming, autothermal reforming and partial oxidation). Thermodynamic simulations have been performed to determine the reformed gas composition varying process, reaction temperature and steam to carbon - oxygen to carbon ratios. Syngas mixtures obtained were experimentally tested in order to evaluate the performance of a SOFC mono-cell. Furthermore, an analysis of the combination: fuel processor with a SOFC stack has been determined in order to assess the total energy efficiency.

Abstract Issues related to SOFCs performance and durability are strictly dependent on the feeding fuel quality. SOFC capability to be fed with fuels different from hydrogen opens to scenarios in which a big variety of fuels can be used at the aim. Unfortunately, problems related to anode deactivation due to the contaminants presence can arise. The present work investigates the performance of anode supported solid oxide fuel cells in case of co-feeding of different trace compounds. Electrochemical impedance spectroscopy is the investigation technique used to analyze the impedance spectra. Typical biogas from OFMSW trace contaminants that follow an initial failure in the cleaning system, such as sulphur, aromatic compounds and siloxanes, have been simultaneously tested. Tests showed that the most deleterious impact for the SOFC was due to the H 2 S action. This influences mostly the electrochemical losses respect to diffusion losses, even if this last are not null and can be accounted as a secondary effect. On the contrary, the co-presence of D4 and H 2 S mitigates in the short-term the effect that the only D4 produces when fed with biogas. The most relevant consequence produced by C 7 H 8 was recorded in the low frequency of Nyquist plot, affecting mainly the mass transport phenomena. Experimental tests are accompanied by the implementation of the fuel cell model through COMSOL Multiphysics software to study the effect of pollutants on fuel cell performance.

Abstract Biogas from the dry anaerobic digestion of OFMSW from a pilot plant was analyzed in terms of sulfur compound removal through a gas cleaning section based on activated carbons, from lab. scale to real plant. In general, even the presence of sub-ppm(v) of selected biogas contaminants can hamper the life-time of SOFC systems. For this reason, stringent fuel cell quality requirements apply. The challenge of real-time monitoring of the performance and quality of the fuel feeding the SOFC can be solved through the use of PTR-MS. This technique – once properly and preliminary calibrated as shown in this study – has the capability of rapidly resolving the wide spectrum of contaminants slipping from the clean-up section. A commercial sorbent material was adopted to remove sulfur compounds and was tested for 80 h in a pilot gas cleaning system. H2S, the main sulfur compound detected (99.36% of total sulfurs) was removed to a satisfactory level. The sulfur compounds elute from the cleaning section in the following order: CH3SH, CH3SCH3, CH3CH2CH2SH, CH3(CH2)3SH, CS2 and H2S. The filter section was able to provide a clean biogas (1 ppm(v)) throughout the whole experimental trial (almost 450 h) with an average H2S inlet concentration of 52 ppm(v).

This study presents a novel methodology for developing a digital twin of a lithium-ion coin cell battery (Graphite-NMC622), accurately replicating the average discharge behaviour of various laboratory-tested batteries and characterizing degradation phenomena through cyclic ageing experiments. Given the anticipated rise in electric vehicle adoption, this work is particularly relevant for addressing the growing demand for lithium-ion batteries. The experimental characterization identified the minimum requirements for battery modelling, with tests conducted up to a C/5 current. Degradation behaviours were analysed through cycle ageing tests at two State-Of-Charge (SOC) ranges (100 %–0 % and 90 %–10 %), establishing a robust foundation for modelling degradation trends. While further calendar ageing tests could enhance the degradation modelling, they would require extensive data and time. Despite these constraints, the virtual coin cell model developed using GT-AutoLion, an industry-standard CAE software, demonstrated excellent accuracy, achieving an RRMSE of less than 2.0 % and R2 greater than 0.95. This work is significant as it provides a reliable framework for battery modelling that can assist companies in optimizing battery design and performance.

AbstractThe real‐life operation of solid oxide fuel cell (SOFC) system has to deal with fuel contaminants which might reduce even significantly the lifetime of reformer and stack depending on the type and amount of contaminant present in the feed stream. From a system perspective, detecting and correlating observed stack and reformer performance degradation with fuel contamination is fundamental to implement correctional procedures (e.g., change of clean‐up vessels catalysts) and/or trigger alarms to prevent a further contamination of the fuel cell. In this work, based on own experiments with several fuel contaminants (H2S, HCl, tars, siloxanes), we have developed empirical degradation models which are able to quantitatively correlate the range of degradation rate resulting from known amounts of a certain contaminant type in the fuel stream. Degradation induced by carbon deposition is also assessed using a simulation model. The techno‐economic trade‐off of having ultra‐stringent purification requirements on the fuel clean‐up unit due to additional operating costs (e.g., for frequent catalysts change) or capital costs (e.g., for vessel over‐sizing to accommodate a larger amount of catalysts and possibly of different types) versus the lifetime of the fuel cell stacks is eventually analyzed.

Abstract The most thermodynamically stable sulfur compound in the anode electrode at SOFC temperature is H 2 S, which dissociates on a nickel (Ni) surface according to a chemisorption mechanism. In this study, SOFC performance losses have been quantified in the presence of H 2 S contamination. The deactivation process has been well quantified by correlating it to Ni surface coverage by sulfur through a Temkin-like isotherm adsorption process. The detailed microscopic features of an Ni-based electrode have been taken into account to quantitatively predict atomic sulfur adsorption on the Ni surface. The results show that, in anode-supported cells, the entire available Ni surface is affected by sulfur contamination and not just the three-phase-boundary (TPB) region. Experiments on both commercial single-cells and on a stack have been described in this work. The H 2 S concentration was varied from 0.8 to 6.5 ppm(v) in the single-cell experiments, and between 0.01 and 25 ppm(v) in the stack experiment. The time-to-coverage evaluation has been established on the basis of the relationship between the sulfur capacity of the Ni anode and the sulfur flow rate through the fuel feed.