Mariagiovanna Minutillo

Biomethane plays a key role in the green transition, offering a renewable, carbon-neutral substitute for natural gas while enabling the storage and use of intermittent renewable energy. This work presents a techno-economic assessment of biomethane production through the Power-to-Biomethane concept, which combines electrolytic hydrogen from renewable electricity with the direct catalytic methanation of raw biogas from anaerobic digestion. The main objective of this study is to identify the optimal plant size and configuration, taking into account the different operational management strategies of the system’s constituting units. The analysis integrates thermochemical modeling with a techno-economic optimization procedure. Three different configurations for renewable energy production, photovoltaic-based, wind-based, and hybrid photovoltaic–wind, were evaluated for a case study in Southern Italy. Results show that the hybrid configuration provides the best techno-economic balance, achieving the highest annual biomethane output (≈2288 t) and the lowest levelized cost of biomethane (EUR 97.4/MWh). While current biomethane production costs exceed natural gas prices, the proposed pathway represents a viable long-term solution for renewable integration and climate-neutral gas supply.

To reduce fossil fuel dependency in shipping, adopting alternative fuels and innovative propulsion systems is essential. Solid Oxide Fuel Cells (SOFC), powered by hydrogen carriers, represent a promising solution. This study investigates a multi-fuel SOFC system for ocean-going vessels, capable of operating with ammonia, methanol, or hydrogen, thus enhancing bunkering flexibility. A thermodynamic model is developed to simulate the performance of a 3 kW small-scale system, subsequently scaling up to a 10 MW configuration to meet the power demand of a container ship used as the case study. Results show that methanol is the most efficient fueling option, reaching a system efficiency of 58% while ammonia and hydrogen reach slightly lower values of about 55% and 51%, respectively, due to higher auxiliary power consumption. To assess technical feasibility, two installation scenarios are considered for accommodating multiple fuel tanks. The first scenario seeks the optimal fuel share equivalent to the diesel tank’s chemical energy (17.6 GWh), minimizing mass increase. The second scenario optimizes the fuel share within the available tank volume (1646 m³), again, minimizing mass penalties. In both cases, feasibility results have highlighted that changes are needed in terms of cargo reduction, equal to 20.3%, or, alternatively, in terms of lower autonomy with an increase in refueling stops. These issues can be mitigated by the benefits of increased bunkering flexibility.

The interest in analyzing alternative fuels and new propulsion technologies for shipping decarbonization is growing rapidly. This paper aims to evaluate the performance of high-temperature polymeric exchange membrane fuel cells (HT-PEMFCs) fed by reformed methanol and their potential application as a propulsion system for vessels. The proposed system is intended to be installed on board a 10 m long ship, designed for commercial use in the marine area of Capri Island. Numerical and experimental analyses were performed to estimate the system’s performance, and a feasibility assessment was carried out to verify its real applicability on board the reference case study. From the numerical perspective, a CFD model of the ship hull, as well as a thermochemical model of the propulsion system, was developed. From the experimental point of view, the system behavior was tested by means of a dedicated test bench. The results of the numerical models allowed for the sizing of the propulsion system and the calculation of the fuel consumption. In particular, to satisfy the ship’s power demand, two 5 kW HT-PEMFCs were needed, with a total fuel consumption of 12.7 kg over a typical daily cruise, with a methanol consumption of 1.88 kg/h during cruising at 7 knots. The feasibility analysis highlighted that the propulsion system fits the vessel’s requirements, both in terms of volume and weight.

In this study, the authors present a techno-economic assessment of on-site hydrogen refuelling stations (450 kg/day of H₂) based on different hydrogen sources and production technologies. Green ammonia, biogas, and water have been considered as hydrogen sources while cracking, autothermal reforming, and electrolysis have been selected as the hydrogen production technologies. The electric energy requirements of the hydrogen refuelling stations (HRSs) are internally satisfied using the fuel cell technology as power units for ammonia and biogas-based configurations and the PV grid-connected power plant for the water-based one. The hydrogen purification, where necessary, is performed by means of a Palladium-based membrane unit. Finally, the same hydrogen compression, storage, and distribution section are considered for all configurations. The sizing and the energy analysis of the proposed configurations have been carried out by simulation models adequately developed. Moreover, the economic feasibility has been performed by applying the life cycle cost analysis. The ammonia-based configurations are the best solutions in terms of hydrogen production energy efficiency (>71%, LHV) as well as from the economic point of view, showing a levelized cost of hydrogen (LCOH) in the range of 6.28 EUR/kg to 6.89 EUR/kg, a profitability index greater than 3.5, and a Discounted Pay Back Time less than five years.

Microbial fuel cells (MFCs) have recently attracted more attention in the context of sustainable energy production. They can be considered as a future solution for the treatment of organic wastes and the production of bioelectricity. However, the low output voltage and the low produced electricity limit their applications as energy supply systems. The scaling up of MFCs both by developing bigger reactors with multiple electrodes and by connecting several cells in stacked configurations is a valid solution for improving these performances. In this paper, the scaling up of a single air-cathode microbial fuel cell with an internal volume of 28 mL, has been studied to estimate how its performance can be improved (1523 mW/m³, at 0.139 mA). Four stacked configurations and a multi-electrode unit have been designed, developed, and tested. The stacked MFCs consist of 4 reactors (28 mL × 4) that are connected in series, parallel, series/parallel, and parallel/series modes. The multi-electrode unit consists of a bigger reactor (253 mL) with 4 anodes and 4 cathodes. The performance analysis has point ed out that the multi-electrode configuration shows the lowest performances in terms of volumetric power density equal to 471 mW/m³ at 0.345 mA and volumetric energy density of 624.2 Wh/m³. The stacked parallel/series configuration assures both the highest volumetric power density, equal to 2451 mW/m³ (274.6 µW) at 0.524 mA and the highest volumetric energy density, equal to 2742.0 Wh/m³. These results allow affirming that to increase the electric power output of MFCs, the stacked configuration is the optimal strategy from designing point of view.