bluuebunny/crossref_metadata_2025 huggingface dataset:
Desorption kinetics of indium adlayers on GaN(0001): Fractional order and non-monotonic behavior
Authors: Lymperakis L. , Lymperakis K. , Iliopoulos E.
Published: December 2024

Epitaxial growth is a dynamic process and, to the first order, is governed by the nature and the rates of elementary surface kinetic mechanisms, such as adatom desorption. In compound-type growing surfaces, particularly in III-nitride molecular beam epitaxy, where the presence of a metallic surface bilayer has a catalytic role, desorption also affects the rates of other elementary mechanisms. In this study, we investigated the desorption of an indium (In) adlayer from GaN(0001) surfaces, a critical kinetic process in the epitaxy of In-containing alloys, using reflection high-energy electron diffraction, density functional theory calculations, and quasi-continuous modeling methods to reveal the underlying physical mechanisms. Our results demonstrate that while the indium bilayer desorbs in a layer-by-layer mode, the desorption mechanisms from the bottom and top monolayers differ significantly. The bottom follows a 3/4 order Polanyi–Wigner relation, attributed to contributions from two different adlayer phases. The top monolayer desorption exhibits a non-monotonic dependence on coverage. This is associated with the liquidus status of this monolayer and its continuous restructuring during desorption. These findings clarify and quantify indium desorption processes from GaN(0001) surfaces, offering insights into analogous mechanisms in other compound-type material systems.
A novel hydrodynamic semiconductor model under Hall current effect and laser pulsed excitation
Authors: Alshehri Hashim M. , Lotfy Khaled
Published: December 2024

This paper presents a novel investigation into the effects of a strong external magnetic field on a hydro-poroelastic semiconductor model within the framework of photo-thermoelasticity theory in two dimensions. This study focuses on generating a Hall current and its impact on the coupled behavior of thermal, mechanical, and electronic fields in a semiconductor medium saturated with fluid. Using the normal mode analysis, we derive and analyze the wave propagation characteristics of key physical fields, including the non-dimensional temperature, displacement, mechanical stresses, carrier density, and excess pore water pressure, in response to the imposed magnetic field. Boundary conditions relevant to real-world applications are incorporated to assess the interactions between these fields. The results provide insight into the dynamic coupling of electromagnetic, thermal, and mechanical phenomena in porous semiconductor materials and offer potential applications in the design of magneto-sensitive semiconductor devices as well as in geophysical and biomedical engineering fields where such multi-field interactions are critical. The results obtained are plotted with some comparisons.
Large-scale turbulence effects on flow dynamics around and aerodynamic forces on a square cylinder
Authors: Wang Xincong , Li Qiusheng , Li Ming , Lu Bin
Published: December 2024

Turbulence effects on the aerodynamics of a square cylinder have been widely investigated due to their fundamental significance in both flow physics and engineering applications. However, the influence of large-scale turbulence on shear layer unsteadiness, and its consequences on flow structure and aerodynamic forces has received insufficient attention. The present study explores these effects, considering turbulent flows with turbulence intensities up to 20% and integral length scales up to four times the characteristic length of the obstacle. A reduced-order model and measurable indicators of flow dynamics are employed to investigate the underlying mechanisms quantitively. The findings reveal that large-scale, high-intensity freestream turbulence amplifies the root mean square (rms) flapping amplitudes of shear layers by provoking and superposing a set of low-frequency unsteadiness with energy levels comparable to that of Karman vortex shedding. The alteration in shear layer behavior results in (1) an extended region of high rms pressures around the square cylinder and (2) intermittent shear layer reattachment, followed by an intermittent weakening of the vortex shedding. These effects lead to a significant increase in rms pressure coefficients on the lateral and leeward surfaces, as well as an intermittent suppression of lift forces. Two new flow patterns were observed during periods of weakened flow dynamics: (1) vortices forming above the lateral surfaces shed downstream directly without interacting with the shear layer on the other side; and (2) Karman vortices in the wake region break down before shedding downstream.
Impact of swirler sleeve length on outlet temperature distribution of a small gas turbine combustor
Authors: Hu Yingqi , Zhang Chi , An Qiang , Cai Wenzhe , Xue Xin
Published: December 2024

Small gas turbine engine combustors hold promising application prospects. Investigating the patterns and mechanisms of how design parameters influence outlet temperature distribution plays a pivotal role in the development of small gas turbine engines with high thrust-to-weight ratios and extended lifespans. Therefore, this study employs high-temperature thermocouple scanning thermometry, particle image velocimetry, planar Mie scattering, and OH* chemiluminescence to examine the impact of varying swirler sleeve lengths on the outlet temperature distribution of a small gas turbine combustor. Both the pilot and main stages of the combustor are fueled with kerosene. Thermocouple test results indicate that increasing the sleeve length leads to an elevation in hot spots at the combustor exit and an expansion of high-temperature regions. In conjunction with optical results, it is revealed that elongating the sleeve enhances and “protects” the fuel–air mixing process within the sleeve, facilitating the formation of high-concentration fuel–air mixtures. Additionally, a longer sleeve stabilizes the heat release zone and recirculation zone further downstream in the combustor, thereby shortening the mixing distance and, to some extent, weakening the heat exchange effects between the mixing/cooling gases and the high-temperature jet core.
Influence of side channel inlet angle on energy conversion of a side channel pump
Authors: Cao Qi , Zhang Fan , Chen Ke , Zhu Lufeng , Xu Zhengxuan , Appiah Desmond
Published: December 2024

The side channel pump generates several disadvantage vortices due to abrupt structural changes at the junction of the impeller and side channel, leading to unstable flow, which may induce severe vortex cavitation at the inlet section of the side channel, its impact on the pump's unstable flow mechanism and on the energy conversion characteristics has yet to be thoroughly investigated. This paper explores the effect of backflow vortex on pump performance through optimizing side channel inlet angles by combining the Ω criterion, helicity, and entropy production methods. The computational fluid dynamics numerical simulation's accuracy has been experimentally verified. It was found that increasing the side channel inlet angle could improve internal flow, thereby suppressing backflow vortices and promoting dynamic vortices formation in the inlet section. The backflow vortex is the primary source of high localized energy loss in the inlet section, significantly influencing the reduction of flow loss. It also reduces low pressure areas caused by backflow vortices, thus, restricting cavitation origin. In addition, within a certain range, the flat side channel pump enhances its hydraulic performance, exhibiting the best performance at a 60° inlet angle with an efficiency improvement of 4.6% at the Best Efficiency Flow Point (BEP), which has the most effective backflow vortex suppression, and therefore, lowest flow losses. However, the head improvement was negligible. The performance improvement is due to complete energy conversion within the inlet section. This paper offers new insights into the mechanisms underlying internal energy loss and cavitation characteristics in refining side channel pumps.
Experimental investigation on the spray structure of supercritical aviation kerosene in a swirling flow field
Authors: Shi Pengyu , Jiang Yuguang , Long Xudong , Jiang Jintao , Zhang Qibin , Fan Wei
Published: December 2024

In advanced aeroengines with higher inlet temperature, the cooling capacity of kerosene should be fully used, which turns kerosene into supercritical. The spray features of supercritical kerosene make the mixing process of supercritical kerosene with air different from that of subcritical kerosene. In this work, the spray of supercritical kerosene in a swirling flow field is investigated experimentally. The spray characteristics of supercritical kerosene are obtained using the schlieren technique. The instability of the jet morphology is analyzed using proper orthogonal decomposition (POD) method. The results prove that the combustor head structure significantly affects the overall spray morphology. A “packet structure” caused by density stratification is observed in the spray, which suppresses the circumferential diffusion of the jet. The “packet structure” is highly correlated with the airflow speed. The structural parameters of the supercritical kerosene jet are not sensitive to the changes in kerosene injection pressure, which, however, has a positive correlation with injection temperature. The main cause of the instability of the jet morphology in supercritical kerosene jets is the formation and shedding of vortices on the jet surface, which can be intensified by condensation. Density stratification suppresses shear layer instability, stabilizing the “packet structure” during the injection.
On the phase behaviors of CH4–CO2 binary clathrate hydrates: Equilibrium with aqueous phase
Authors: Tanaka Hideki , Matsumoto Masakazu , Yagasaki Takuma
Published: December 2024

We explore the solubilities of guest CH4 and/or CO2 in the aqueous state coexisting with the corresponding hydrate. The equilibrium conditions are estimated by calculating the chemical potentials of water and guest species in the hydrate on the basis of a statistical mechanical theory using pairwise intermolecular potentials. This requires the least computational cost while covering a wide range of temperature, pressure, and composition of guest species, even for the binary hydrate. The nonstoichiometric nature, one of the most important characters of hydrates, is invariably taken into account when evaluating its phase behaviors and the driving force for nucleation of hydrates. The two-phase equilibrium concerning CO2 hydrate is evaluated considering a low but finite value of CO2 solubility in water. It is found that the finite solubility gives rise to a small systematic deviation of the dissociation temperature of CO2 hydrate. The solubility of CO2 coexisting with fluid CO2 decreases with temperature but the opposite temperature dependence is obtained in the presence of hydrate, as in the case of CH4. This method is applied to CH4–CO2 binary hydrates of various guest compositions. We also find a significant difference in composition of guests among the phases involved in the equilibria.
Numerical investigation on the evolution process of hydraulic transport and overcurrent blockage of silted urban rainwater pipelines: An approach based on computational fluid dynamics and discrete element method
Authors: Li Tianwei , Di Danyang , Chen Zhuo , Fang Hongyuan , Li Bin , Wang Niannian , Sun Bin
Published: December 2024

During urban flood events, the effect of urban rainwater pipeline siltation on overflow and stagflation intensifies the severity of flood disaster. However, the dynamic coupling mechanism of pipeline sedimentation and water flow is still unclear. To investigate the influence of two-phase flow on the hydraulic transport of siltation particles in rainwater pipelines, the numerical simulation model based on computational fluid dynamics (CFD) and discrete element method (DEM) is constructed. Then, the transient continuity governing equation and conservation equation of momentum are formulated to provide dynamic guidance and boundary constraint for CFD-DEM simulation. On this basis, the optimal drag force model and measurement method of equivalent siltation degree of pipeline are proposed and nested with CFD-DEM, and then, a high resolution numerical simulation model of pipeline sedimentation is formulated. The results show that the siltation degree affects the efficiency of drainage pipeline to a degree of 47%, which is much greater than the degree of influence of 33% for siltation length and 18% for slope. When the siltation degree is 0.1, the thickness of the silted bed surface under the influence of water flow scour is reduced by 33%. It revealed that the influence degree of siltation degree and flow rate was 168% and 20%, respectively, which was much larger than that of siltation length and slope. This study can provide technical support for subsequent pipeline cleaning and maintenance as well as flood prevention and mitigation.
Linear stability analysis in channel with slippery and rough boundaries
Authors: Zhang Jiayu , Zhang Ruigang
Published: December 2024

This study examines two-dimensional flow stability in a channel with a superhydrophobic wall and small amplitude roughness. We consider two primary cases: (1) the upper surface is smooth and allows slip, while the lower surface is rough and has no slip; and (2) both surfaces exhibit slip behavior. By using the orthogonal modal method for the Orr–Sommerfeld equation, we rigorously assess the flow's linear stability. The results demonstrate that the slip coefficient and rough wave number significantly influence stability characteristics. Variations in the slip coefficient lead to notable changes in stability thresholds, while the rough wave number alters the flow's response to perturbations. These findings enhance our understanding of the interactions between fluid dynamics, surface properties, and stability phenomena in channels, providing valuable insights for optimizing flow control strategies and designing surfaces in various engineering applications.
Magnon valley Hall effect and tunable chiral edge transport in AB-stacked kagome lattices
Authors: Xing Yuheng , Fu Hao , Li Mengyao , Qiu Wenjuan , Zhang Chunwei , Zhang Haiyang , Xu Ning
Published: December 2024

Our research investigates the magnon bands and their topological characteristics in a ferromagnetic pyrochlore lattice, with the Dzyaloshinskii–Moriya (DM) interaction playing a significant role. Given its kagome AB bilayer structure, the ferromagnetic exchange couplings, which may differ among the AB triangles, are further considered for their implications on the system’s magnetic properties. By employing the non-equilibrium Green’s function method, we explicitly demonstrate that the one-way chiral edge magnon transport is indeed regulated by the DM interaction direction (D→−D) and the exchange interaction of J1 and J2 (J1↔J2). Moreover, we demonstrate that the topological edge state predominantly resides along the edges and exhibits an oscillatory decay as it penetrates into the bulk in a non-equilibrium state. Although the chiral edge magnons and the corresponding energy current tend to travel along one edge from the hot region to the cold one, in the bulk, however, the energy current flows reversely from the cold to the hot region. The valley magnon Hall effects and chiral edge transport proposed here may be realized in the thin films of the insulating ferromagnet, such as Lu2V2O7. Thus, it will pave the way for a more extensive use of magnonics in future technologies.
High fire severity and frequency threaten the persistence of a widespread obligate-seeder Banksia in south-eastern Australia
Authors: Muir Annette M. , Amos Nevil N. , Moloney Paul D.
Published: December 2024

Context Obligate-seeding woody plants with long reproductive maturity periods and no soil seed banks are threatened with decline as climate change drives more frequent and severe fires, such as the extensive 2019–2020 wildfires in south-eastern Australia. Aims This study aimed to investigate the effects of fire intervals and severity on the persistence of one such species, Banksia cunninghamii (Hairpin Banksia), in temperate forests. Methods We measured post-fire seedling recruitment of B. cunninghamii at 25 sites in Victoria, burned at various severities in the 2019–2020 wildfires and with differing prior fire intervals. A Bayesian framework was used to model the relationship between seedling numbers, fire severity and fire interval. A spatial analysis compared a species distribution model for B. cunninghamii with fire severity and fire intervals. Key results There was a low chance of B. cunninghamii recruitment (<25%) at sites that either had burned eucalypt canopies or a preceding fire interval of less than 12 years. Sixty-seven percent of its distribution in the south-east of the state of Victoria was mapped as burned at high severity (burned eucalypt canopies) between 1998 and 2020, or burned at shorter than 12 year intervals between 1960 and 2020, although some B. cunninghamii populations will have persisted due to the patchiness of past burns. Conclusions Banksia cunninghamii is vulnerable to local extinctions in the wildfire-affected areas if fires occur again before plants reach maturity, or if high fire severity destroys seeds. Implications More frequent and severe wildfires mean that burn planning needs to consider the reproductive cycles of serotinous obligate-seeding plants.
Actin polymerization counteracts prewetting of N-WASP on supported lipid bilayers
Authors: Wiegand Tina , Liu Jinghui , Vogeley Lutz , LuValle-Burke Isabel , Geisler Jan , Fritsch Anatol W. , Hyman Anthony A. , Grill Stephan W.
Published: December 2024

Cortical condensates, transient punctate-like structures rich in actin and the actin nucleation pathway member Neural Wiskott-Aldrich syndrome protein (N-WASP), form during activation of the actin cortex in the
Caenorhabditis elegans
oocyte. Their emergence and spontaneous dissolution is linked to a phase separation process driven by chemical kinetics. However, the mechanisms that drive the onset of cortical condensate formation near membranes remain unexplored. Here, using a reconstituted phase separation assay of cortical condensate proteins, we demonstrate that the key component, N-WASP, can collectively undergo surface condensation on supported lipid bilayers via a prewetting transition. Actin partitions into the condensates, where it polymerizes and counteracts the N-WASP prewetting transition. Taken together, the dynamics of condensate-assisted cortex formation appear to be controlled by a balance between surface-assisted condensate formation and polymer-driven condensate dissolution. This opens perspectives for understanding how the formation of complex intracellular structures is affected and controlled by phase separation.
Co-free gradient lithium-rich cathode for high-energy batteries with optimized cyclability
Authors: Yang Haotian , Wang Lihang , Li Yuqiang , Zhuo Zengqing , Wu Tianhao , Liu Jie , Xu Ligang , Du Haozhe , Liu Shiqi , Wu Lingqiao , Zhao Shu , Tang Mingxue , Yang Wanli , Yu Haijun
Published: December 2024

Lithium-rich layered oxides (LLOs) hold the promise for high-energy battery cathodes. However, its application has been hindered by voltage decay associated with irreversible reactions at high voltages despite decades of intensive efforts. Here, we first theoretically studied the molecular orbitals of Mn-based Li-rich configurations. We found that the
π
-bond ring formed within the LiMn
6
structure could participate in stable redox reactions as one unit, but Co could disrupt its symmetry. We thus designed and synthesized Co-free concentration-gradient LLOs (CF-CG-LLOs) materials. The combination of concentration gradient and Co removal leads to exceptional capacity retention without any fading over 100 cycles of the pouch cell. More importantly, it exhibits an extraordinarily low voltage decay of 0.15 mV/cycle, accompanied by a high Coulombic efficiency of 99.86%. This concept and demonstration of CF-CG-LLO cathodes reveal a viable avenue toward low-cost, high-energy-density battery cathodes.
eLemur: A cellular-resolution 3D atlas of the mouse lemur brain
Authors: Jeon Hyungju , Kim Jiwon , Kim Jayoung , Choi Yoon Kyoung , Ho Chun Lum Andy , Pifferi Fabien , Huber Daniel , Feng Linqing , Kim Jinhyun
Published: December 2024

The gray mouse lemur (
Microcebus murinus
), one of the smallest living primates, emerges as a promising model organism for neuroscience research. This is due to its genetic similarity to humans, its evolutionary position between rodents and humans, and its primate-like features encapsulated within a rodent-sized brain. Despite its potential, the absence of a comprehensive reference brain atlas impedes the progress of research endeavors in this species, particularly at the microscopic level. Existing references have largely been confined to the macroscopic scale, lacking detailed anatomical information. Here, we present eLemur, a unique resource, comprising a repository of high-resolution brain-wide images immunostained with multiple cell type and structural markers, elucidating the cyto- and chemoarchitecture of the mouse lemur brain. Additionally, it encompasses a segmented two-dimensional reference and 3D anatomical brain atlas delineated into cortical, subcortical, and other vital regions. Furthermore, eLemur includes a comprehensive 3D cell atlas, providing densities and spatial distributions of non-neuronal and neuronal cells across the mouse lemur brain. Accessible via a web-based viewer (
https://eeum-brain.com/#/lemurdatasets
), the eLemur resource streamlines data sharing and integration, fostering the exploration of different hypotheses and experimental designs using the mouse lemur as a model organism. Moreover, in conjunction with the growing 3D datasets for rodents, nonhuman primates, and humans, our eLemur 3D digital framework enhances the potential for comparative analysis and translation research, facilitating the integration of extensive rodent study data into human studies.
OmpA controls order in the outer membrane and shares the mechanical load
Authors: Benn Georgina , Borrelli Carolina , Prakaash Dheeraj , Johnson Alex N. T. , Fideli Vincent A. , Starr Tahj , Fitzmaurice Dylan , Combs Ashton N. , Wühr Martin , Rojas Enrique R. , Khalid Syma , Hoogenboom Bart W. , Silhavy Thomas J.
Published: December 2024

OmpA, a predominant outer membrane (OM) protein in
Escherichia coli
, affects virulence, adhesion, and bacterial OM integrity. However, despite more than 50 y of research, the molecular basis for the role of OmpA has remained elusive. In this study, we demonstrate that OmpA organizes the OM protein lattice and mechanically connects it to the cell wall (CW). Using gene fusions, atomic force microscopy, simulations, and microfluidics, we show that the β-barrel domain of OmpA is critical for maintaining the permeability barrier, but both the β-barrel and CW–binding domains are necessary to enhance the cell envelope’s strength. OmpA integrates the compressive properties of the OM protein lattice with the tensile strength of the CW, forming a mechanically robust composite that increases overall integrity. This coupling likely underpins the ability of the entire envelope to function as a cohesive, resilient structure, critical for the survival of bacteria.
Gasification of agricultural residues to support the decarbonization of the transport sector via electricity generation: a case study
Authors: Morselli Nicolò , Puglia Marco , Ottani Filippo , Pedrazzi Simone , Noussan Michel , Laveneziana Lorenzo , Prussi Matteo , Talluri Giacomo , Allesina Giulio , Tartarini Paolo
Published: December 2024

The gradual electrification of transport, particularly private cars, requires widespread electricity availability and potential peak demand in rural or underdeveloped regions could strain the existing electricity network. Therefore, exploring distributed electricity generation is crucial to reduce grid demand and can be an opportunity to promote low-carbon technologies. In this research work we analyze the potential contribution of a biomass gasifier, fueled by vine prunings, in supplying electricity to a local site for electric vehicles charging. The performance of the system is assessed from a technical, economic and environmental point of view. In particular, the specific equivalent CO2 emissions of the system are compared to the alternative emissions of the national power grid, considering the estimated charging profiles based on available patterns from real case studies that incorporate different users’ behaviours and preferences. The electricity produced by the gasifier has a calculated supply chain carbon intensity of 134 gCO
2e
· kWh
−1, which can be sharply reduced to -34 gCO
2e
· kWh
−1, indicating a carbon-negative process, when the carbon sequestration of the co-produced biochar is considered. These figures should be evaluated against a weighted average carbon intensity of the national electricity mix equal to 384 gCO
2e
· kWh
−1 in 2018, while the same figure for 2030 ranges from 141 gCO
2e
· kWh
−1 to 226 gCO
2e
· kWh
−1 depending on the future scenario that is considered. The economic assessment estimates payback times between 6 and 8 years with an average utilization factor of the charging station equal to 14% and a charging price equal to 0.62 €/kWh. In addition to the emission savings that are obtained, this approach could generate further positive effects on the territory: a) the production of electricity allows rural areas to establish their sustainable electric transportation network, reducing their marginalization; b) the production portfolio of farms or agricultural consortia is diversified; c) create a carbon-negative recovery chain for lignocellulosic waste and offers a sustainable solution for their disposal. The results of this analysis can be of use for other researchers dealing with similar topics, and for policymakers that aim to compare available solutions for the decarbonization of the transport sector.
Energy storage scenarios and design of a new Italian innovation infrastructure for energy transition
Authors: Conversano Antonio , Zatti Matteo , Sogni Davide , Consonni Stefano
Published: December 2024

The revised European Renewable Energy Directive sets the EU’s binding renewable energy target for 2030 to a minimum of 42.5% from renewable sources in the overall energy mix. To achieve the fit-for-55 objectives, Italy intends to increase solar and wind power plants installations by 2030, with expected power capacities of 79.3 GW and 28.1 GW respectively. Renewable energy penetration is unlocked by an adequate storage capacity availability which should increase by up to 95 GWh (2030) in the Country. The present paper aims at providing an outlook on the national energy scenarios and forecasts on energy storage systems penetration, sharing the design of an innovation facility to support the industry in advancing the technological maturity of energy storage systems with specific reference to hydrogen and e-fuel production as well as electrochemical storage.
An insight on the calculation of aerodynamic polars for stall-controlled wind turbines using CFD: the case of S8XX airfoils
Authors: Venturi Alessio , Melani Pier Francesco , Papi Francesco , Bianchini Alessandro
Published: December 2024

To ensure that stall control performs correctly in wind turbines making use of this logic, having accurate airfoil data near and post the stall limit is crucial. Due to the scarcity of experimental data, Computational Fluid Dynamics (CFD) simulations are increasingly used to this end, although modelling stall is critical due to the impact of turbulence that often impacts on transition; therefore, various numerical methods have been proposed for use within a Reynolds-Averaged Navier-Stokes approach. In this study, a critical analysis has been carried out to define some best practice in the simulation of airfoils designed for stall control. Commonly adopted transitional models, i.e., the k-ω SST and the γ-Reθ
ones, have been compared with the novel GEKO model by Ansys, and deriving CFD results are benchmarked against ubiquitous panel methods (XFoil and RFOIL), which still often represent an industry standard. Key performance factors have been critically compared, providing some case-specific indications on the benefits and drawback of the different models.
Integration of Floating Photovoltaics and Pumped Hydro Energy Storage with Water Electrolysis for Combined Power and Hydrogen Generation
Authors: Migliari Luca , Micheletto Davide , Marchionni Matteo , Cocco Daniele
Published: December 2024

This study proposes a floating photovoltaic - pumped hydro energy storage system integrated with a water electrolyzer for combined power and hydrogen generation. Compared to solutions without electrolyzers, this integrated system is able to further mitigate the non-programmable photovoltaic generation and simultaneously decarbonize hard-to-abate sectors. The performance of the integrated system is herein studied on daily, monthly, and yearly bases using a mathematical model with a 1-hour time resolution for a real case represented by a pumped hydroelectric energy storage system in Sardinia. The study considers integrating the existing system with a 11 MW floating photovoltaic system and a 4 MW PEM electrolyzer, appropriately sized to achieve a hydrogen production target of 100 tonnes per year and a photovoltaic self-consumption not below 95%. The power used for pumping water and producing hydrogen is 100% renewable, as it is supplied solely by the floating photovoltaic plant, and the electricity is fed in the grid at night, aiming to increase the share of renewables in the nighttime energy mix of the Sardinia region. Results show that the integration provides significant benefits to the grid, with 8.5 GWh/year of nighttime inertial feed-ins. Moreover, since the integrated plant is characterized by annual self-consumption values of photovoltaic generation around 97% and monthly values never below 93%, the negative impact caused by its non-programmable feed-ins on the grid is minimal. Hydrogen production, capable of replacing approximately 0.1% of the current yearly fossil fuel-based thermal demand of the regional industrial sector, exhibits strong seasonality, with daily production averaging 65 kg/day during winter months and over 7 times more (465 kg/day) during summer months, suggesting the opportunity for a seasonal storage.
Optimized design procedure for small-scale Pumped Hydro Energy Storage systems based on the use of pumps as turbines
Authors: Laconi Nicola , Licheri Fabio , Cambuli Francesco , Cocco Daniele , Petrollese Mario
Published: December 2024

Pumped Hydro Energy Storage (PHES) is a well-established technology offering large storage capacities. In recent years, small-scale PHES plants are becoming more interesting, due to their possibility of being integrated with renewable-based microgrids. However, the high capital costs represent the most critical economic factor for such storage systems. The cost of the hydraulic machines can be mitigated by using commercial centrifugal pumps in reverse mode (the so called Pump as Turbine, PAT, technology) in place of small hydro-turbines. One of the main issues in PHES systems that operate with a single machine is the procedure followed to select the optimal PAT for a given case study. In this study, an automatic selection method was developed, utilizing commercial pump data and optimization algorithms in MATLAB to identify the optimal PAT configuration based on site-specific characteristics and user load profiles. To test the effectiveness of the proposed procedure, the case study of a small-scale PHES located in Sardinia (Italy) coupled with a photovoltaic plant is considered. Results demonstrated that while the choice of the PAT closest to the theoretical best efficiency point exhibit higher nominal efficiencies, their actual operational efficiencies showed considerable variation. This underscores the importance of both developing an algorithm capable of comparing different PATs and defining a method to determine an adequate group of PAT candidates. Additionally, the number of PATs installed significantly impacts the performance of PHES systems. Increasing the number of PATs generally enhances flexibility and efficiency in energy usage during the charging phase, leading to greater energy output during discharge phases. However, operating an excessive number of PATs far from their nominal conditions can result in efficiency losses.
OWC Systems Savonius Turbine Reduced Order Model Implementation by Means of Experimental Data
Authors: Brusca Sebastian , Galvagno Antonio , Mauro Stefano , Messina Michele , Lanzafame Rosario
Published: December 2024

The present paper discusses the implementation of a Reduced Order Model (ROM) for an OWC Power Take-Off Savonius turbine. The turbine’s ROM relies primarily on experimental data. An ad hoc laboratory-scale oscillating flow simulator was constructed to replicate the behaviour of the OWC power take-off turbine under various operating conditions. A laboratory-scale Savonius turbine with a diameter of 0.09 m, an aspect ratio of 1, and an overlap ratio of 1/3 was subjected to testing. Performance evaluations were conducted using the laboratory-scale oscillating flow simulator. In this paper, all tests were conducted at a fixed maximum air velocity of 5 m/s and different air flow oscillation frequencies. A data-driven method was employed to implement the turbine ROM, utilizing data collected during the experimental campaign. To test ROM model air flow oscillation frequency of 1.0 Hz is used.
Fluidized Bed Reactors for energy recovery from biomass and wastes: a data-driven approach towards the development of digital twins for real time control and monitoring
Authors: Baldelli Matteo , Bartolucci Lorenzo , Cordiner Stefano , Mulone Vincenzo
Published: December 2024

The application of machine learning (ML) techniques for the control and development of digital twins for a fluidized bed reactors represents a significant advancement in process engineering. In this study, the integration of data-driven models trained using computational fluid dynamics (CFD) simulations, is explored for developing and optimizing the lab-scale fluidized bed reactor operations. By leveraging the collection of data generated from CFD simulations, data-driven algorithms, based on the Singular Value Decomposition (SVD) and Gaussian processes for regression, are trained to predict the gas-solid flow patterns under different operating condition. The data-driven models presented, serve as efficient reduced order model (ROM) surrogate for computationally expensive CFD simulations, enabling real-time predictions and control strategies for fluidized bed reactors, facilitating continuous monitoring, optimization, and predictive maintenance. Moreover, the ROM can effectively capture the complex relationships within the reactor system, with an overall error < 10% even without precise knowledge of the underlying physical phenomena. The synergistic combination of ML techniques and CFD simulations offers valuable insights into complex multiphase flow phenomena and reactor dynamics, leading to improved process control, energy efficiency, and overall performance of fluidized bed reactors. This approach holds great promise for accelerating innovation and sustainability in chemical and energy industries.
A new data-driven Life Cycle Assessment tool at the urban scale: the case of the Milan building stock analysis to reduce the related environmental potential impacts
Authors: Famiglietti Jacopo , Motta Mario , Mazzarella Livio
Published: December 2024

Given the ambitious targets for greenhouse gas emissions reduction set by the European Union and the importance of cities in achieving these goals, there is an increasing need to analyze a city’s environmental footprint with a life cycle approach. The life cycle assessment is considered the leading methodology for environmental metrics, permitting a holistic environmental perspective on cities. Life Cycle Assessment software applications are aimed at single product evaluation, making urban scale, data management, and environmental assessment complicated or impractical, mainly due to the massive data processing required. The novelty of this work is a new tool, utilizing a data-driven approach, that allows an extensive environmental evaluation of buildings (following the EN 15978 standard, considering 20 impact categories). The tool was applied to analyze the city of Milan. Approximately 240 000 building units were investigated and compared using as activity data the information described in the energy performance certificates of building units. The results for Residential, Commercial, and Retail building units (old and new) are 58, 65, and 84 kg CO2eq / (m2 of useful floor area * year), respectively, considering space heating, domestic hot water, and controlled mechanical ventilation. Actions linked with: (i) improving energy systems, (ii) the decarbonization of energy carriers (i.e., electricity and natural gas), and (iii) the retrofitting of envelopes by running the tool developed. The outcomes obtained were used to verify pieces of legislation listed in the “Fit for 55” and “REPowerEU.” The scenarios lead to the conclusion (for Milan) that the reduction of greenhouse gas emissions by at least 55% (by 2030) is achievable only by retrofitting at a rate of 1.6% per year both energy systems and envelopes, plus also acting on the decarbonization of energy carriers.
A review on outdoor urban environment modelling
Authors: Naila  , Prataviera Enrico , Carli Michele De
Published: December 2024

Outdoor environment modelling is crucial for multiple facets of a sustainable urban development, such as mitigating the detrimental environmental impacts (i.e. greenhouse gas emissions), proposing energy-efficient building designs, optimizing the usage of green resources, and improving the overall comfort level of urban residents. This paper presents a comprehensive review of the techniques and models related to the various aspects of an outdoor urban environment modelling, including the microclimate dynamics modelling, solar radiation modelling, wind-flow and air-temperature assessment simulations, urban-canyons and heat island effects modelling, and green-infrastructure planning. Each section covers and compares the traditionally used methods and models in the field with the newer artificial intelligence (AI) based models, aiming to explore their relevant efficiencies and areas of improvement. For instance, microclimate’s traditional models like radiative transfer models are evolving to machine-learning based high-resolution remote sensing methodologies and community-based participatory models. Similarly, wind-flow section encompasses the traditional CFD, and wind-tunnel models modified by machine learning (ML) and data-driven methodologies. Moreover, the paper also discusses the urban heat island (UHI) phenomenon and the related models. Overall, the paper aims to provide a comprehensive state of the art on the traditional and cutting-edge methodologies of all the necessary aspects of outdoor environment modelling, to help provide informed decision-making for sustainable urban environments.
CFD simulation of the increased electric boost effects on the glass melting process in a real glass furnace to support decarbonisation of glass industry
Authors: Cravero Carlo , Marsano Davide , Milanese Gabriele
Published: December 2024

The glass industry plays a pivotal role in modern manufacturing, providing essential materials for a multitude of applications ranging from construction to consumer goods. However, the substantial energy demands, primarily driven by the intense heat required to melt raw materials within furnaces, pose significant challenges. Traditionally, thermal energy is sourced from combustion processes in dedicated chambers. Yet, in the pursuit of efficiency and environmental sustainability, there is a growing preference for integrated systems. Notably, the utilization of electrode installations within glass baths emerges as a promising choice for direct melting augmentation through electricity in a more efficient way. This study introduces a sophisticated computational fluid dynamics (CFD) model, developed by the authors, tailored to simulate the real operation of a glass furnace. The model fully couples the reactive flow in the combustion space (the furnace) with convective motions within the glass tank including the effect of the electrodes. By changing the thermal energy from combustion with varying levels of electrode operation (keeping the same overall heat flux to the glass), the furnace behaviour is investigated. The research specifically examines the effects of electrode operation on crucial furnace parameters, including flame heat release and convective motions inside the glass bath, across different scenarios. Insights are gained into the complex interplay between electrode operation, thermal dynamics, and glass quality within the furnace environment. The findings of this study not only deepen the understanding of fundamental processes within glass manufacturing but also offer actionable insights for industry stakeholders. By elucidating the intricate relationship between electrode operation and glass melting process, this research provides practical guidance for optimizing furnace design and operation, enhancing efficiency and CO2 reduction, with the same product quality, in the glass industry.
Hourly carbon intensity of natural gas combined cycles compared to the current and future electricity mixes in Italy
Authors: Fambri Gabriele , Noussan Michel , Badami Marco , Chiaramonti David
Published: December 2024

The current solutions for power generation include a wide range of technologies, each providing specific advantages and limitations. In a decarbonization perspective, their carbon intensity will represent a crucial factor in determining their success towards a future low-carbon electricity mix. Today, natural gas combined cycles are among the most efficient plants, especially when operating in combined heat and power mode. This paper presents the analysis of the actual carbon intensity of a large-scale natural gas combined cycle, calculated on an hourly basis over several years of operational data, compared with the average hourly emissions of the Italian power grid both with the most recent electricity mix and the forecast to 2030 and 2040, based on the decarbonization targets that are currently in place. The results of this study highlight the very low carbon intensity of the electricity produced in CHP mode, with average monthly values as low as 242 g/kWh during the winter months, compared to around 350 g/kWh when operating in full-electric mode in summer. These values are lower than the current performance of the Italian electricity mix in winter, although the opposite is true in summer, confirming the importance of the cogeneration in decreasing the carbon intensity of the energy output. However, in a future low-carbon electricity system, fossil gas CHP units will have higher carbon emissions than the average mix. In order to achieve the decarbonisation objective it is necessary to take these considerations into account. The availability of a high-resolution estimate of the performance of power generation will support policy makers in developing strategies to deploy the most effective technologies to decarbonize the energy system.
Exergy Analysis of Gas Turbine Open Cycle with Pressure Gain Combustion Based on Humphrey Cycle
Authors: Dubey Abhishek , Sorce Alessandro
Published: December 2024

This paper describes an exergy comparison of the pressure gain combustion (PGC) gas turbine (GT) with conventional GT. PGC has recently emerged as a promising approach to achieve major performance improvements in the current gas turbines operating on the Joule cycle, where the potential for major performance upgrades has nearly plateaued. However, the inherently unsteady and periodic nature of this combustion technology presents challenges in modelling the PGC process and understanding its impact on the cycle. In this work, PGC is represented by a steady-state model of constant volume combustion based on the Humphrey cycle, along with a constant pressure combustion loss model for capturing practical losses. Exergy performance was analysed in terms of exergy destruction for three air-cooled GT cycles with different combustors: a conventional isobaric combustor, an optimistic PGC combustor with no losses and a realistic PGC combustor with losses. Gas turbine cycles were modelled in WTEMP (Web-based Thermo-Economic Modular Program) software, a modular and flexible cycle analysis tool developed by TPG at the University of Genova. Simulations were performed at compressor pressure ratios from 5 to 40 at turbine inlet temperatures of TIT=1300°C and TIT=1700°C, and results were analysed in terms of exergy destruction and exergy efficiency. It was found that a PGC combustor with optimistic losses recovers more exergy than a conventional combustor due to pressure gain. At a cycle pressure ratio of 20 and 1700°C TIT, the PGC combustor with a pressure ratio of 1.35 resulted in an exergy efficiency of 79.6% compared to 77.9% of the Joule combustor. However, with realistic loss from inlet pressure drop and constant pressure combustion in the PGC combustor, the PGC combustor showed higher irreversibility than conventional combustor but the overall benefit on the cycle was retained at low compressor pressure ratios. Moreover, the percentage increase in turbine irreversibility from blade cooling was found to be slightly lower for the PGC cycle as compared to Joule.
Numerical and experimental investigation on the performance of a biodiesel ICE-ORC integrated system
Authors: Falbo Luigi , Perrone Diego , Morrone Pietropaolo , Algieri Angelo
Published: December 2024

Improving the efficiency of energy systems is a fundamental step towards decarbonized energy production. Waste thermal energy recovery from internal combustion engines (ICEs) is critical, and organic Rankine cycle (ORC) technology is one of the most effective solutions. In this work, a performance analysis was carried out on an integrated system consisting of a compression ignition engine fuelled with biodiesel bottoming with an ORC used for the waste heat recovery from the exhaust gas. In particular, experimental tests were conducted to evaluate the effectiveness of biodiesel as a substitute for diesel fuel and the main differences with traditional fuel in terms of electric efficiencies and exhaust gas temperatures. Furthermore, an experimental investigation was performed on a micro-ORC system. Mathematical models were developed for both sub-systems to allow coupling and evaluate the performance of the integrated apparatus, even when the size of the engine varies. The results show that the electric efficiency of the biodiesel ICE is comparable with the pure diesel, whereas the exhaust gas temperature is lower. The integrated ICE-ORC system guarantees higher electric efficiency and power than the standard internal combustion engine.