• Energy Research
• 2021-2025close
• Restricted close
• Open Source close
• National Research Council close

The most widely used process for hydrogen production is steam methane reforming. It can be carried out using a membrane reactor in which simultaneous hydrogen production and purification occur. Mathematical modeling of these reactors plays a key role in the selection of the design and operating parameters that yield high performance for the reactor. This review study discusses, synthesizes, and compares different mathematical modeling studies on the packed bed membrane reactors for hydrogen production from methane found in the literature. Different approaches used in these modeling studies for the hydrogen permeation steps, reaction kinetic expressions, phases involved (pseudo-homogeneous and heterogeneous), and spatial dimensions (one, two, and three dimensional) are given.

The launch traffic to Low Earth Orbit (LEO) is undergoing significant changes: instead of launching few, complex, large and expensive spacecraft, the trend is now towards the use of multitudes of small, less complex and lower-cost satellites. Large constellations, encompassing thousands of satellites in restricted regions of space, are emerging as important space assets. The intensifying commercial use of LEO and international debate regarding the stability of the space environment is a growing discussion among policy makers. Utilizing the SDM 5.0 evolutionary model developed by the Italian National Council of Research (CNR), the first step of this analysis is to estimate the growth of the space objects in LEO in the next decades. The analysis considers the space objects >10 cm, including active and defunct satellites, spent rockets bodies and fragments, along with varying future traffic, mitigation and remediation scenarios. Subsequently, the analysis focuses on the probability of collision with active satellites and on related mitigation and remediation scenarios. Based on this, the study employs a qualitative and preliminary approach to assess satellite operators' economic convenience of adopting measures that can mitigate the risk of collision by comparing their cost to the damage costs that may occur in case of collision. Finally, the study dedicate its concluding considerations to discuss if a free market setting can stimulate the formation of effective solutions to space debris challenges (namely, if it provides operators with the economic incentive to adopt or develop mitigation measures) or if public institutions' intervention is needed to finance mitigation strategies and, in particular, complex technologies development and adoption.

La transizione energetica e lo sviluppo sempre più capillare delle energie da fonti rinnovabili stanno suscitando un interesse sempre più crescente, favorendo la nascita di comunità per la produzione di energia e l'autoconsumo collettivo, al fine di ridurre drasticamente le emissioni e poter così raggiungere definitivamente l'obiettivo di decarbonizzazione prefissato per il 2050 dall'Unione Europea. Nel nostro Paese, le comunità energetiche potranno diventare il volano per le energie da fonti rinnovabili, permettendo ai cittadini di partecipare alla generazione, alla distribuzione, alla fornitura, al consumo, all'aggregazione ed allo stoccaggio dell'energia. Proprio attraverso una maggiore consapevolezza del fenomeno che si sta sviluppando, i cittadini possono associarsi ed effettuare scelte comuni per produrre localmente l'energia elettrica necessaria al proprio fabbisogno, anche condividendola, avendo così accesso a servizi di efficienza energetica. Queste nuove forme di mobilitazione collettiva, già note nei movimenti comunitari legati alla filiera alimentare, cominciano a diventare sempre più presenti nella costituzione delle comunità energetiche, con il fine ultimo, non solo di ridurre l'uso di fonti fossili ed emissioni, in favore di un sistema energetico basato sull'impiego di risorse energetiche rinnovabili, ma anche di poter produrre innovazione sociale in termini di empowerment delle persone, inclusività ed impatto di lunga durata, incoraggiando il cambiamento di pratiche sociali e valori collettivi; il mutamento tecnologico, quanto quello sociale, può essere soddisfatto solo da un forte coinvolgimento degli attori sociali.

In the recent years, some experimental forms of housing (cohousing and social housing) have developed in Italy, which also take on the features of real energy communities. These initiatives have been planned and implemented thanks to the active participation and investments of the people involved in the project. Their primary aim is to implement new form of shared housing, but by adopting renewable generation systems and sharing both energy production and consumption, they are contributing to foster the energy transition process. In this research, we studied the management of the energy resource and the social interactions among the cohousers. Moreover, we analysed the social impacts on the surrounding territory in order to know as they can widespread the clean energy technologies and social innovation processes. To do this, we compared two experiences of collaborative housing: the first one, active since some years in Northern Italy, is a bottom-up initiative set up by the voluntary action of some families and individuals. Its goal is to share common spaces and activities, but also to produce and use renewable energy with a view to economic and environmental sustainability. The second one is a social cohousing, established in Messina (Southern Italy) and implemented by the Fondazione di Comunità di Messina. The project involves people who live in socio-economic difficulties. Through the ESCO Solidarity & Energy, the Fondazione has designed and applied energy systems to allow the tenants to become prosumers and prosumagers.

In recent years, the biomass as a renewable feedstock has been gaining utmost importance in order to meet the global need for fuels and chemicals from sustainability perspectives [1,2]. Principal components of biomass are cellulosic and triglycerides derivatives. The triglyceride part is principally used to obtain biodiesel and liquid alkanes, as alternative fuels [3]. Biomass derived from the lignocellulose part is rich in carbohydrates and furan derivatives, and the presence of oxygen in their structure makes them suitable for further utilization to obtain added-value products. As concern the sustainability of the chemical processes, efforts are being made to turn them into "green" processes, working on the procedures (favorable reagent ratio, catalyst amount and green solvents) and exploiting heterogeneous catalysis. The use of solid catalyst is indeed very favorable from a sustainable point of view, due to its simple separation, regeneration and recycling of the material [4,5]. This implies a high efficiency of the catalysts accompanied by a decrease in the processing cost. This presentation will focus on different types of functionalized silica or titania based materials applied to the biomass exploitation, both to the synthesis of biodiesel and its additives and for the obtainment of added-value products such as GVL, diols or HMF. Biomass can use also for the production of new materials applied in the abatement of aqueous pollutants

This research proposes an innovative solar thermal plant able to generate mechanical power through an optimized system of heliostats with Scheffler-type solar receivers coupled with screw-type steam expanders. Scheffler receivers appear to perform better than parabolic trough collectors due to the high compactness of the focal receiver, which minimizes convective and radiative heat losses even at high vaporization temperatures. At the same time, steam screw expanders are volumetric machines that can be used to produce mechanical power with satisfactory efficiency also by admitting two-phase mixtures and with further advantages compared to steam turbines: low working fluid velocities, low operating pressures, and avoidance of overheating. This study establishes a mathematical model to assess the energetic advantages of the planned solar thermal power system by evaluating the solar-to-electricity efficiency for different off-design working conditions. For this purpose, a numerical model on the Scheffler receiver is initially investigated, thus assessing all the energy losses which affect the heat transfer phase. A thermodynamic model is then developed to evaluate the energy losses and performance of the screw expander under real working conditions. Finally, parametric optimization of the solar energy conversion is performed in a wide range of operating conditions by establishing thermodynamic formulations related to the whole solar electricity generation system. Water condensation pressure and vaporization temperature are so optimized with respect to global energy conversion efficiency which, under the best operating conditions achieved in this research, rises from 10.9% to 14.4% with increasing solar irradiation intensity. Hence, the combined use of screw expanders and Scheffler receivers for solar thermal power system application can be a promising technology with advantages over parabolic dish concentrators. Novelty statement: This research proposes an innovative direct steam solar power plant based on an SRC, with water utilized as both heat transfer and working fluid, equipped with Scheffler solar receivers as a thermal source and screw expanders as work-producing devices. Technical studies and energy assessments of this kind of SEGS at part-load operation do not exist in scientific literature; after reviewing the literature, it was determined that volumetric expanders have been rarely combined with Scheffler receivers for solar thermal power system application. In effect, combined use of screw expanders and Scheffler-type solar concentrator in a direct steam solar power system represents a completely new plant configuration; however, as a promising DSG solar system, at present numerical model of this new sort of SEGS is lacked in literature and the optimum operating conditions have yet to be defined. For this reason, the chief objective of this paper is to define a first parametric optimization of all thermodynamic variables involved to maximize global efficiency of the proposed solar thermal power generation system for ordinary working conditions.

In this work, a novel enhanced deep borehole heat exchanger (EDBHE) was proposed to improve heat extraction efficiency based on the jet grouting method. By means of this technology, a soilcrete zone with high thermal conductivity was built near the wellbore. To analyze the feasibility and efficiency of this method, we firstly constructed a validated deep borehole heat exchanger (DBHE) model based on the field experimental data. Numerical simulations were carried out to investigate the 30-year production performance of EDBHE. Results demonstrated that the jet grouting method is an efficient way for improving thermal output of DBHE. It is evaluated that the average annual heat production rate over a 30-year heating period of EDBHE is 463.2 kW, which is 1.27 times as that of DBHE. Sensitivity analyses indicate that the heat production rate and outlet temperature mainly depend on the height and radius of the artificial soilcrete zone. However, thermal output is not sensitive to thermal conductivity of the soilcrete zone due to the higher thermal resistance of the geological formation. For the experimental site used in this work, the recommended height, radius, and thermal conductivity of the soilcrete are 1000 m, 1.0 m, and 50 W/m °C, respectively.

Growing interest of the European Union to introduce new emission regulations seeking to lower the particle cut-off size down to the current limit set at 23 nm, has made crucial to achieve an extensive comprehension on their nature. In this regard, it is necessary to deepen their knowledge under different engine technologies, operating conditions, fuel properties and after-treatment devices and how their measure is affected by the sampling and dilution procedure. This paper provides a study on the sub-23 nm particles emitted from a small direct/port fuel injection, spark ignition engine fueled with gasoline, ethanol and a 30% v/v ethanol/gasoline blend, at different operating conditions. Particles were measured both upstream and downstream of a three-way catalyst. The conditions of the sampling were changed in order to investigate the volatile organic fraction. For this purpose, the exhaust gas sample was diluted through a Particulate Measurement Programme compliant system. The temperature of the first dilution stage and of evaporation chamber were changed to discriminate the volatile compounds by enhancing the condensation and the nucleation processes. An engine Exhaust Particle Sizer was used for the sizing and the counting of the particles in the range 5.6-560 nm. The results show a strong dependence of the sub-23 nm particle emissions from the engine operating condition and the fuel type. A moderate impact of the three-way catalyst was instead observed. Moreover, a significant effect of the dilution parameters in the sampling system was noted pointing out the importance to define an appropriate protocol for the measurement of the sub-23 nm particles.