In this paper, the authors present an overview of biomass gasification modeling approaches with the aim of evaluating their effectiveness as a modeling tool for the design and optimization of polygeneration plants based on biomass gasification. In fact, the necessity to build plant operating maps for efficiency optimization requires a significant number of simulations, and non-stoichiometry equilibrium models may allow fast computations thanks to their relative simplicity. The main objective consists of the assessment of thermodynamic equilibrium models performance as a function of biomass type and composition to better understand in which conditions of practical interest such models can be applied with acceptable reliability. To this aim, the authors developed two equilibrium models using both a commercial software (referred as Aspen model) and a simulation tool implemented in a non-commercial script (referred as analytical model). To assess their advantages and disadvantages, the two models were applied to the gasification simulation of different biomasses, employing experimental data available from the scientific literature. The obtained results highlighted strengths and limitations of using equilibrium models as a function of biomass type and composition. For example, they showed that the analytical model predicted syngas composition with better accuracy for biomass types characterized by a low ash content, whereas the Aspen model appeared to fairly predict the syngas composition at different conditions of ER; however, its accuracy might be reduced if the properties of the treated biomass changed.

The performance of the artificial compressibility (AC) version of the characteristic based split (CBS) scheme for the solution of transient free convection in tall cavities is analyzed. A dual time-stepping procedure is used to recover the transient solution. The true transient term is discretized explicitly up to the fourth order of approximation, with consequent possibility to adopt larger true time-steps and to gain in accuracy and computing efficiency. In order to obtain the present results, the novel stability analysis recently developed by the authors for the steady-state AC-CBS scheme is here extended to the transient algorithm. Cavities with three different aspect ratios have been considered: 8:1, 10:1, and 16:1. The obtained results have been compared with the analytical and numerical data available in the literature.

This study offers a detailed techno-economic assessment of Carbon Capture (CC) integration in an existing Waste-to-Energy (WtE) incineration plant, focusing on retrofit application. Post-combustion carbon capture using monoethanolamine (MEA) was modeled for various low-scale plant sizes (3000, 6000, and 12,000 t of CO₂ per year), using a process simulator, highlighting the feasibility and implications of retrofitting a WtE incineration plant with CC technology. The comprehensive analysis covers the design of the CC plant and a detailed cost evaluation. Capture costs range from 156 EUR/t to 90 EUR/t of CO₂. Additionally, integrating the CO₂ capture system reduces the overall plant absolute efficiency from 22.7% (without carbon capture) to 22.4%, 22.1%, and 21.5% for the different capture capacities. This research fills a gap in studying small-scale CC applications for the WtE incineration plants, providing critical insights for similar retrofit projects.

Green hydrogen exploitation plays a crucial role in achieving carbon neutrality by 2050. Hydrogen, in fact, provides a number of key benefits for the energy system, due to its integrability with other clean technologies for energy production and consumption. This paper is aimed at presenting the project of recovery of an abandoned industrial area located in central Italy by developing a site for the production of green hydrogen. To this aim, the analysis of the territorial and industrial context of the area allowed us to design the project phases and to define the sizing criteria of the hydrogen production plant. The results of a preliminary cost–benefit analysis show that a huge initial investment is required and that, in the short term, the project is sustainable only with a very large public grant. On the other hand, in the long term, the project is sustainable, and the benefits significantly overcome the costs.

The increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in renewable energy sources such as wind energy. Amongst the different typologies of wind generators, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, Computational Fluid Dynamic (CFD) simulations were performed in order to investigate the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds. The micro turbine under investigation is composed of three pairs of airfoils, consisting of a main and auxiliary blades with different chord lengths. The simulations were made using the open source finite volume based CFD toolbox OpenFOAM, considering different turbulence models and adopting a moving mesh approach for the turbine rotor. The simulated data were reported in terms of dimensionless power coefficients for dynamic performance analysis. The results from the simulations were compared to the data obtained from experiments on a scaled model of the same VAWT configuration, conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). From the proposed analysis, it was observed that the most suitable model for the simulation of the performances of the micro turbine under investigation is the one-equation Spalart-Allmaras, even if under the conditions analysed in the present work and for TSR values higher than 1.1, some discrepancies between numerical and experimental data can be observed.