bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental on-site measurement of thermal conductance by means of heat flow meter applied to nanocomposite thermal insulating mortar coating
Authors: Bergero S. , Cavalletti A. , Chiari A. , Marafioti C.
Published: December 2024

In the energy refurbishment of buildings, the declared thermal conductivity is the key to meet the minimum requirements concerning energy efficiency and tax incentives. Regardless of the assessment method for thermal conductivity, in situ measurements using the heat flow meter technique can be always performed, especially in case of very low and self-declared thermal conductivities. In the present work, the reliability of the heat flow meter approach is validated considering a multilayer wall, with all thermal properties declared by means of technical regulations or CE marking. The measured total conductance of the wall is in very good accordance with the calculated one. Then, the heat flow meter has been applied to a plastered stone masonry wall before and after the application of a nanocomposite, thermal insulating, mortar coating 8 mm thick, with a self-declared thermal conductivity of 0.0019 W/(m K) without CE marking or appropriate laboratory tests. The thermal conductance obtained from the on-site measurements is about five times greater than the expected one. The increase in thermal resistance due to the mortar is comparable to a material with the same thickness, but with the thermal conductivity one order of magnitude greater than the self-declared value.
Preliminary results of the deployment of the Smart Readiness Indicator in Italy
Authors: Canale Laura , Bongiorno Stefano , Monaco Marianna De , Pietra Biagio Di , Notte Luca La , Badan Nicola , Ficco Giorgio , Puglisi Giovanni , Dell’Isola Marco
Published: December 2024

The Smart Readiness Indicator (SRI) was firstly introduced by the 3rd Energy Performance of Buildings Directive as an optional certification scheme to rate the smart readiness of buildings and promote building smartness throughout Europe. According to the 4th EPBD recast the Commission shall, by June 2027, adopt a delegated and an implementing act by requiring the application of a common scheme for rating the smart readiness of buildings to highly energy intensive non-residential buildings. Although the SRI legal framework is now well defined, on the technical hand, national authorities must provide details of the SRI calculation for their own building stocks. Nowadays, only a generic technical framework designed after extensive European stakeholder consultations is available, allowing the SRI currently being officially tested in 13 EU countries. The aim of this paper is to provide an overview of the research activities currently ongoing at a national level on SRI to define a methodological approach for SRI calculation tailored for the national context. The standard and tailored methodologies were then compared using two representative case studies in the tertiary sector of the Italian building stock. Despite the high level of technological equipment, the results showed that the SRI indicator obtainable with the standard methodology was low. This suggests that an adaptation of the catalogue of smart-ready services will be required to make it more responsive to the characteristics of existing buildings and to the devices currently available on the market.
Multi-criteria analysis of the improvement interventions related to the Superbonus 110%: efficiency, renewables
Authors: Romano Giada , Scarlet Sferra Adriana , Mancini Francesco
Published: December 2024

The 2050 long-term strategy of the European Union contains an analysis of the actions that need to be taken for the transition to a zero GHG emission economy and to to build a better future for all by 2050. The outlined scenarios envisage ambitious objectives in terms of the energy efficient building improvements, the use of RES and the reduction of climate-changing emission. Following this European vision, EU Member States have developed national long-term strategies and focusing on the building sector, in Italy the Recovery and Resilience Plan is providing financing and national and European investment is expected to enable the renovation of more than 100,000 buildings, with a total upgraded area of more than 36 million square metres. The expected energy saving is about 191 Ktoe/year with a reduction in greenhouse gas emissions of about 667 Kton CO2/year. At the end of 2023, the energy requalification of buildings reached about 12 million square metres. By 31 December 2025, the objective is to ensure the energy requalification of buildings for at least 32 million square metres. The proposed research aims to investigate the effects of the renovation activities related to the Superbonus 110% through a multi-criteria analysis, taking into account the beneficial effects consisting of the energy efficiency improvement. The research has been conducted starting from a database of 1,545 dwellings on the territory of Italy, using a data collection questionnaire to estimate the energy consumption of a dwelling, with an in-house developed calculation code based on a simplified dynamic simulation. The database has been set to satisfy different purposes: to characterize the energy uses of residential utilities and identify flexible loads; to estimate the effects of energy upgrading interventions; to analyse the transformation potential of residential buildings with the introduction of an integrated PV-Heat Pump-Thermal Storage system; to evaluate the best energy upgrading proposal based on the climate zone and building location; to evaluate the cost of energy upgrading interventions. The proposed activity aims to complement the studies carried out by projecting the existing situation into more scenarios congruent with the national and European context; the envisioned scenario interprets the need to increase the building stock efficiency and integrate more renewable energy resources into energy systems. In light of the estimates produced and the results achieved, the research aims to emphasize the reuse of building materials issue, looking at circular reuse, offering a different and broader assessment of interventions aimed at the construction sector and, more specifically, the residential sector.
Indoor Thermal Comfort Impact of Windcatcher Ventilation in Tropical Climates: A Case Study in Panama via Fluid Dynamics Simulation
Authors: Bernal Ana , Montilla Lenin , Mora Dafni , Chen Austin Miguel
Published: December 2024

Different ventilation approaches are recommended to address the effects of low indoor air quality while reducing electrical consumption. One of these approaches follows the natural ventilation strategy, such as windcatchers. This results in a practical method to improve occupant health by positively influencing air quality and reducing electrical consumption for air conditioning. Due to the small temperature difference between a building’s inner and outer spaces, windcatchers prove effective even in tropical climates. Thus, this research aimed to evaluate the potential of windcatchers with local indicators, such as air velocity, pressure, and temperature, using the Computational Fluid Dynamics (CFD) module integrated into DesignBuilder software v7. This study consists of two CFD analyses of a single-zone and single-story building in Panama City with a short semicircular windcatcher. Results showed that implementing natural ventilation combined with a windcatcher is effective during seasons with high wind velocities, as the model experienced an inlet airflow velocity of 0.67 m/s and an outlet airflow velocity of 0.43 m/s. Meanwhile, during low wind velocities, the model experimented with inlet and outlet airflow velocities of 0.26 m/s and 0.07 m/s, respectively. Therefore, incorporating a windcatcher is an effective way to reduce energy consumption and improve comfort. Future studies will focus on developing improvements in its geometry and characteristics.
Monitoring the impact of micro-photovoltaic production on a real residential case study
Authors: Lauro Fiorella , Romano Sabrina , Botticelli Martina
Published: December 2024

In this paper a case study of micro-photovoltaic (MPV) production impact on real houses in Rome area is presented. The experimentation was conducted as part of the “Electrical System Research” Program, funded by the Italian Ministry for the Environment, and thanks to a Collaboration Agreement between ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development) and ARETI (the Distributor System Operator in Rome urban area). During this experimental activity, it was possible to carry out a few pilot cases and integrate the Smart Home Kit, supplied by ENEA, with the new generation electricity meters, supplied by ARETI. Different types of users were involved, both simple consumers and prosumers equipped with micro-photovoltaic and photovoltaic (PV) panels. Starting from the collected data, some considerations were made regarding the percentage of self-sufficiency of the users. The common goal was to test innovative energy management methods aimed at increasing users’ energy awareness and encouraging a more virtuous and flexible use of energy, also thanks to a greater diffusion of the electric vector.
High-efficiency waste heat recovery systems integrated with thermal energy storage for sustainable Data Centres.
Authors: Sechi Alessandro , Serra Fabio , Casti Efisio , Cocco Daniele
Published: December 2024

This paper proposes an advanced energy recovery system for Data Centres (DCs), highly energy-intensive facilities that can be effectively coupled with eco-sustainable technologies to meet the Green New Deal targets. In this context, this study aims to assess the opportunities of recovering the waste heat produced by a DC to satisfy the energy heating demand of some office buildings. The evaluation was carried out by a simulation model developed in MATLAB-Simulink environment. The considered DC was cooled with rear door and CPU cold plate heat exchangers coupled with two chillers and a water TES. The parametric analysis showed how an average 53 kW DC placed in south Sardinia (Italy) can effectively meet the heating needs for office building volumes from 20000 to 40000 m3. Since the recovered energy never exceeds 60% of the available energy from the DC, the payback time is always higher than 10 years. Further analysis, considering more demanding utilities, as hospitals, district heating or industrial processes, could make this solution more profitable.
Advancing Energy Efficiency in Automotive Production: A Model-Based Optimization of Pneumatic Blowing Processes for Metal Sheet Separation
Authors: Rakova Elvira , Simeone Antonio , Frosina Emma , Fusco Aniello , Senatore Adolfo
Published: December 2024

This study investigates the high energy demand of pneumatic systems in automotive production and presents the development of a predictive model for optimizing the blowing process. Through experimental validation, the findings highlight significant energy savings and operational efficiency improvements. This paper aims to provide a comprehensive analysis of energy optimization in pneumatic systems, specifically focusing on metal sheet separation in the automotive industry.
A steady-state numerical approach for the thermo-structural analysis of a cryogenic piston pump
Authors: Cioni Stefano , Balduzzi Francesco , Romani Luca , Sambri Luca , Marianetti Luca , Ferrara Giovanni
Published: December 2024

The process of liquefaction of gaseous fuels, such as natural gas or hydrogen, is an essential technology that helps reduce transportation costs over long distances. Cryogenic piston pumps play a critical role in these systems, as they compress the fuel up to 700 bar before vaporization and storage in high-pressure vessels. Due to the extreme temperatures and pressures involved, the design of these machines poses a significant challenge from the thermal and structural point of view. This work presents the application of a simplified numerical approach for evaluating the thermally induced stresses and deformations through a de-coupled thermo-structural three-dimensional analysis of a prototype cryogenic piston pump. Thermal simulations of the solid domain are carried out to assess the steady-state temperature distribution of the pump. The heat transfer between the pump and cryogenic liquid is computed using three-dimensional steady-state CFD simulations of the suction and discharge phases. Heat generated by friction during the working cycle of the pump and external natural convection are calculated and imposed as a heat source in the simulations. The steady-state temperature distribution is imposed in a finite-element steady-state three-dimensional structural simulation to evaluate the combined effect of thermal loads induced by the cryogenic temperatures and loads induced by the high working pressures. Results show how the proposed methodology can assist in the design of cryogenic piston pumps by offering valuable insights into the most critical aspects of these machines.
Techno-economic assessment of Green Hydrogen Production for Blending in the Natural Gas Network
Authors: Calabrese Mattia , Ademollo Andrea , Busi Lorenzo , Meazzini Michele , Carcasci Carlo
Published: December 2024

Increased electricity generation from renewable sources is critical for the transition towards a zero-carbon future. While this growth of production presents challenges in grid management due to inadequate storage systems for surplus electricity, solutions such as green hydrogen production offer promising avenues for integration into existing infrastructure. By leveraging surplus renewable electricity to power electrolyzers and inject green hydrogen into natural gas networks, we take a significant step forward in realizing an integrated gas-electric system. This study delves into this concept by conducting a comprehensive techno-economic assessment of a hydrogen production facility. The initial step is to determine the required volume of hydrogen to achieve a 10% concentration within a real natural gas distribution network. This value is such that the gas mixture remains within the Higher Heating Value (HHV), Wobbe Index (WI) ranges defined by Italian legislation. The goal is to optimize component sizing using a genetic algorithm to minimize the Levelized Cost of Hydrogen (LCOH) while meeting criteria for green hydrogen production. In fact, results show that an input from electricity grid is necessary to meet the hydrogen demand while maintaining the techno-economic feasibility of the system. A sizing optimization is therefore performed on photovoltaic, electrolyzer and storage system. Furthermore, the study underscores the critical role of energy policies, particularly green hydrogen incentives, in determining the economic feasibility of the system. By analyzing their impact on economic revenues, the authors emphasize the importance of supportive regulatory frameworks in driving the transition towards a more sustainable future.
Identification of synthetic parameters for the thermal characterization of Phase Change Materials in MH-PCM hydrogen storage systems
Authors: Krastev V. K. , Baldelli M. , Bartolucci L. , Cordiner S. , Falcucci G. , Mulone V.
Published: December 2024

The present work adopts a multidimensional CFD methodology to investigate the thermal coupling between Phase Change Materials coupled and intermetallic Metal Hydrides, for hydrogen storage and delivery. In contrast to the currently available literature on this topic, the focus here is shifted from specific application-oriented modeling towards the systematic identification of a minimum set of parameters to highlight eventual similarity patterns among different PCM families. To achieve this goal, a representative cylindrical-type MH-PCM system model has been defined for a discharge-mode configuration, taking into account engineering-related constraints like the optimal hydrogen pressure delivery and hydrogen massflow control. The results obtained are expected to significantly improve design practices based on standard CFD methods, as well as to pave the way for the derivation of fast and accurate data-driven model surrogates for real-time modeling applications.
Enhancing PEM Electrolyzer Performance through Electrochemical Impedance Spectroscopy: A Review
Authors: Discepoli Gabriele , Barbi Silvia , Venturelli Matteo , Montorsi Monia , Montorsi Luca , Milani Massimo
Published: December 2024

The development of electrolyser technology is currently undergoing a breakthrough phase, poised to meet the upcoming demands for widespread hydrogen production under stringent requirements including high efficiency, purity, affordability, and rapid response to harness the full potential of renewable energy sources. In recent years, this rapid advancement necessitated concerted efforts supported by various diagnostic tools to achieve a comprehensive understanding of the underlying mechanisms governing electrolytic processes across diverse operating conditions. These tools prove particularly effective when capable of providing real-time insights into the features and behaviour of the studied system during operation. This paper presents a review of the latest diagnostic tools employed in the investigation of modern electrolyzers, with particular emphasis on electrochemical impedance analysis (EIS). It delves into how this tool facilitates a deeper comprehension of the fundamental electrochemical principles governing electrolysis, its evolution in the study of electrolysis, and its interconnectedness with other diagnostic methodologies.
Hydrogen as a direct heat exchange fluid in room temperature hydride systems: Numerical study on the desorption process
Authors: Vincenti Ferdinando , Valenti Gianluca
Published: December 2024

Hydrogen, as an energy carrier, is a promising candidate to foster decarbonization. However, its storage poses significant challenges. Common methods, such as compressed gas and liquid hydrogen, have high energy consumption and safety concerns. Recently, solid hydrogen storage in materials like metal hydrides has gained attention for their ability to store hydrogen safely at low pressures and low temperatures. This study aims to develop a numerical model to simulate the performance of metal hydrides using hydrogen as a direct fluid heat exchanger during desorption. The model, formulated as a system of partial differential equations, is implemented in MATLAB with the ODE15s solver and applied to a disk-type lanthanum nickel reactor to minimize pressure drops. Performance is investigated by varying design parameters, including reactor length and diameter, bed porosity, hydride particle diameter, operating pressure and temperature, and hydrogen mass flow rate at the reactor inlet. Additionally, the energy consumption of auxiliary equipment, such as pumping and thermal power, is evaluated. Results show that the system energy requirement is about 8-9% of the hydrogen lower heating value, with most desorption occurring in less than 300 seconds. The reactor dimensions are crucial for fast desorption and low pressure drops, with pumping power under 1 W given the small thickness and flow rate. Particle diameter and porosity have minor impacts, while pressure, temperature, and flow rate are fundamental. High temperatures, low pressures, and high recirculating flow rates favor the reaction, though a trade-off between performance and energy consumption is necessary since all high temperatures high recirculated mass flow rate allows for high consumption.
Investigating experimentally the performances of a natural gas reciprocating compressor adapted to pure hydrogen up to 30 MPa
Authors: Dalberto T. , Battistella F. , Perus T. , Corsini M. , Ravidà A. , Valenti G.
Published: December 2024

Hydrogen as an energy carrier can be integrated into various value chains, enabling the decarbonization of hard-to-abate processes. Hydrogen storage is necessary to handle the intermittency of renewables. Moreover, it allows hydrogen to be deployed in sectors such as mobility and backup power. Currently, high-pressure vessels are typically used for hydrogen storage. The compression process is required since hydrogen production occurs at lower pressure than storage. This study examines a three-stage reciprocating compressor for natural gas, which is operated with pure hydrogen. The compressor, driven by a 3-kW electric motor, can deliver 30 MPa starting from pressures between 0.3 and 0.8 MPa. The aim is to assess the energy impact of compression on hydrogen production and analyze potential issues such as leakages or contamination that can arise after changing the Gluid. The study involves measuring hydrogen Glow rates, inlet and outlet pressures, and electric power consumption during the Gilling of a vessel. The experiment shows a specific power input of 1.2 kW/(Nm3/h), more than 1/3 of the lower heating value, maximum isothermal efficiency of 21% and maximum isentropic efficiency of 34%. The optimal compression ratio is found to be between 25 and 30. Based on the few data available in literature, the performances do not reach state-of-art levels of 55-80% isentropic efficiency. However, the device was optimized for the compression of natural gas, and the scope of this study was to use it with fewer possible modifications.
Impact of Hydrogen Blending Policies on the Energy Efficiency, Environmental and Economics parameters of Residential Gas Boilers
Authors: Vespasiano Domiziana , Vespasiano Flavia , Massulli Axel Riccardo , Ciancio Alessandro , Santoli Livio de
Published: December 2024

At present, gas-fired boilers are among the most common systems for heating residential buildings. The potential integration of hydrogen into the gas network is being considered as a viable option for decarbonising heating systems. This study investigates the impact of hydrogen injection into the network, focusing on how it affects boiler performance by analysing energy and environmental parameters with different hydrogen fractions. Specifically, the study examines the technical, economic and environmental consequences of using hydrogen-enriched natural gas (H2NG) blends in gas-fired boilers. Primary energy consumption and emissions were evaluated using H2NG blends with hydrogen fractions ranging from 0% to 25% by volume. In addition, the study evaluates the influence of the blend on the system operating costs and the LCOH (levelized cost of heat) in relation to the LCOH2
(levelized cost of hydrogen). An analysis was carried out to determine the effect of hydrogen on emissions to facilitate the calculation of the Carbon Abatement Cost (CAC) of using the blend. The results show that the incorporation of H2NG blends further reduces the EPnr, with a 30% hydrogen blend achieving a 12.05% reduction. CO2 emissions also decrease proportionally with increasing hydrogen content. Economically, LCOH increases with increasing hydrogen content, with a 30% blend increasing boiler costs by 4.93%. In conclusion, the integration of hydrogen into heating systems can significantly reduce both non-renewable energy consumption and CO2 emissions but requires an increase in costs for fuel purchase due to the different energy vector.
Simultaneous estimation of in- and out-of-plane thermal conductivities of composite materials using a contact-heating technique: an optimum experimental set-up design
Authors: D’Alessandro Giampaolo , Monte Filippo de , Sfarra Stefano
Published: December 2024

The optimum set-up of a two-dimensional (2D), transient, three-layer, heat conduction experiment aimed at simultaneously estimating the thermal properties of composite materials is designed. The experimental apparatus is based on the plane-source method consisting of a thin electrical heater in contact with two larger samples of the same material and thickness.

Due to the thermal symmetry of the apparatus and neglecting the thermal heater inertia and related contact resistance with the sample, the three-layer composite conduction problem is modeled through only one orthotropic rectangular plate (sample) whose thermal properties are assumed temperature-independent. This plate is partially heated for a finite period at the front boundary through a surface heat flux (due to the thin heater), whereas its opposite boundary is subject to heat losses with the environment simulated by a heat transfer coefficient (the remaining boundaries are kept insulated). This coefficient accounts only for free convection when the unheated back side of the sample is exposed to the surrounding air and, hence, its temperature is measured using an infrared camera or a pyrometer. However, if thermocouples are used on the back side of the sample, it is a common practice to thermally insulate it to reduce the air disturbance on the thermal measurements. In this case, the above coefficient accounts for both the insulating material and free convection with the air.

The exact analytical temperature solution of the addressed heat conduction problem is obtained using a generalized solution available in the specialized literature. The superposition principle is also applied to account for a finite heating period. Then, the scaled sensitivity coefficients of temperature with respect to the parameters of interest (in- and out-of-plane thermal conductivities, volumetric heat capacity, and the heat transfer coefficient with the surrounding ambient) are computed on the back side of the specimen, and a sensitivity analysis is performed to establish whether correlation between them exists at different locations. Finally, the optimum experiment is designed by applying one of the D-optimum criteria, known as Δ+ criterion. Its application leads to the optimum heating and experiment times, the optimum sample aspect ratio, and the optimum width of the heated region.
Thermal Transport in the Entry Region of a Microchannel in the Presence of Electro-osmotic Flow
Authors: Suzzi Nicola , Lorenzini Marco
Published: December 2024

The motion of a polar fluid in microducts induced by an external electric field, known as electro-osmotic flow, enables fluid circulation without the need for mechanical devices. This feature makes it particularly appealing for the thermal management of electronic components, as microchannels with almost any cross-sectional shape can be easily integrated on the chips. Therefore, it is essential to evaluate how the channel’s geometry influences heat transfer performance. This study investigates the thermal entry region and fully developed electro-osmotic flow in a microchannel with a rectangular cross-section and smoothed corners, with one adiabatic wall and uniform temperature elsewhere. The paper proposes correlations for the Poiseuille and Nusselt numbers, taking into account the aspect ratio and non-dimensional smoothing radius under fully developed thermal and hydrodynamic conditions, which can be valuable for practical design purposes. The study also emphasizes how Joule heating may lead to the reversal of heat flow and how the thermal entry length is linearly dependent on the logarithm of the non-dimensional Joule heating in thermally developing flow. Additionally, it demonstrates that smoothing the corners may increase the local Nusselt number over sharp corners, but it may also shorten the thermal entry length.
Surface Roughness Effects on Heat Transfer in Additive Manufactured Microchannels: A CFD Study
Authors: Gammaidoni Tamara , Zembi Jacopo , Battistoni Michele
Published: December 2024

Microchannel heat exchangers are widely used in applications where compactness and efficient heat transfer are essential. The difficulty of producing metal microchannels with conventional techniques leads to the adoption of additive manufacturing, such as Direct Metal Laser Sintering (DMLS), which offers unprecedented design freedom but introduces relevant surface roughness, impacting heat transfer phenomena.

The objective of this research is to methodically examine the impact of roughness factors on heat transfer through Computational Fluid Dynamics (CFD) analyses.

In particular, the parametric study focuses on one specific spatial parameter, the roughness Correlation Length (CL), to consider the spatial distribution of surface features. This parameter offers a more thorough analysis than the commonly used Average Roughness (Ra
) and Root Mean Square Roughness (Rq
). Specifically, two types of rough surfaces are investigated: isotropic and anisotropic, to capture the complex interplay between surface roughness and heat transfer more accurately.

This research advances understanding regarding the effects of surface roughness on heat transfer, advocating for the adoption of comprehensive spatial parameters for its accurate characterization. Additionally, the findings provide crucial insights for optimizing thermal management systems, guiding engineers in improving heat transfer efficiency in additively manufactured microchannels.
On the influence of the refrigerant inlet position and circuitry layout on plate-finned tube evaporator performance through the hybrid method
Authors: Macchitella Silvia , Colangelo Gianpiero , Starace Giuseppe
Published: December 2024

Multiple factors can impact the performance of a plate-finned tube evaporator in terms of heat transfer rate and refrigerant pressure drops, including the circuitry layout and the position of the refrigerant distributors. In order to assist designers, various circuitry layout alternatives together with different refrigerant inlet positions were examined in this work, using the hybrid method to calculate the evaporator performance. Based on prediction functions coming from the outcomes of either numerical, analytical, or experimental analysis, the hybrid method has the advantage of combining affordable computing costs with accurate findings. Moreover, the refrigerant inlet position can cause uneven vapor quality entering the various circuits. This characteristic, along with the variation in flow rates it implies, was also examined to investigate their influence on the heat exchanger’s performance.
The biomethane potential for public transport decarbonization in Italian cities
Authors: Noussan Michel , Prussi Matteo , Chiaramonti David
Published: December 2024

The transport sector remains heavily reliant on oil products, and it is among those that are considered harder to decarbonize, especially in some specific segments. Considering public transport, there is currently a significant interest in electrifying urban buses, especially for some routes that are well suited for the current characteristics of battery electric buses. However, for some applications, including long-distance buses, biomethane could play an important role in contributing to the decarbonisation of the sector, especially considering the important part of the current fleet in Italy that is already operating on fossil natural gas. This analysis presents a comparison of the potential role of biomethane to support public transport decarbonization in Italy, by estimating CO2 equivalent emissions savings considering the current biogas plants and natural gas buses in Italian cities. An additional evaluation is performed considering the future expected evolution of biomethane production in line with the new Piano Nazionale Integrato per l’Energia e il Clima, that aims to a total production of 5.7 bcm by 2030, as well as the expected 1.5 bcm of biomethane allocated to the transport sector. Within these maximum potential levels, the results of the analysis demonstrate the important savings that can be achieved with biomethane, especially when exploiting specific feedstocks that have a very low impact in terms of well-to-wheels emissions. Biomethane can represent an interesting complement to electric buses, as it can exploit the already existing fleet based on natural gas, and it also shows a number of advantages on routes that are not suitable for electric buses.
Definition and Validation of a Zero-Dimensional IC Engine Model for Assessing the Performance of Different Methane-Hydrogen Mixtures
Authors: Cazzoli Giulio , Falfari Stefania , Bianchi Gian Marco
Published: December 2024

To decarbonize the maritime transport sector, a solution inspired by the automotive industry involves using a solid oxide fuel cell (SOFC) in conjunction with an internal combustion engine. For optimal emission efficiency, the internal combustion engine is fueled with a primary fuel, typically methane already on board for feeding the SOFC, plus anode off-gases from SOFC, which are a mixture of variable composition of hydrogen, carbon dioxide, and carbon monoxide. To assess the performance of the integrated system (SOFC+ICE) and subsequently search for an optimal set-up, it is useful to use a zero-dimensional model of each component of the system. Particularly, the internal combustion engine model must balance speed of execution with flexibility in terms of fuel composition, engine dimensions, and other relevant parameters. In this study, an engine model originally developed for gasoline-fueled ICE, is adapted for variable methane-hydrogen mixtures. The model is validated against experimental data measured on an engine operating with similar mixture compositions and available in the literature.
Analysis of the Heat Content of Exhaust Gases from a Heavy-Duty Diesel Engine under Real-world Driving Conditions and Cold Start Operation
Authors: Donateo Teresa , Cutuli Paolo , Vilotta Niccolò , Algieri Angelo , Morrone Pietropaolo
Published: December 2024

European Commission is currently working on defining new Euro 7 standards for light and heavy-duty vehicles, which will set severe restrictions on emissions in real driving conditions, and under cold-start operations. It is well known that about 60% of fuel energy converted in a diesel engine is lost in exhaust flow, coolant, and other forms of loss. A more efficient vehicle usage can be achieved by exploiting such dissipated energy content to produce additional mechanical or electrical energy. Several solutions can be adopted for Waste Heat Recovery (WHR) systems. Among them, exploiting the synergy between Organic Rankine Cycles (ORCs), thermal storage with Phase Change Materials (PCM), and electric hybridization is the solution adopted in the research project IRIDESCENT (biodIesel hybRID Electric buS with waste heat reCovEry aNd sTorage). The efficacy of recovering heat content from exhaust gases in reducing fuel consumption has already been demonstrated under stationary conditions. However, one of the challenges in applying WHRs to the powertrain of road vehicles is the fast dynamics of the engine load that determines fast variations in the flow rate and temperature of the exhaust gases. This makes it difficult to optimize energy recovery and explains the need to adopt PCM thermal storage systems. In this framework, the goal of the present work is to characterize the variability of temperature and flow rate in the exhaust gases of a diesel engine for heavy-duty applications under real-world driving conditions. To this end, a dataset of information retrieved from the scientific literature for the Isuzu FTR850 truck was used. The dataset consists of twenty-eight trips performed with the same driver over the same route. It includes both hot-start and cold-start trips and three different values of trailer load (0, 1500, 3000 kg). For each trip, data from GPS, ambient sensors, onboard diagnostics (OBD) systems, and portable emissions measurement systems are made available with a frequency of 1 Hz. In this investigation, a statistical analysis of the data set and a preliminary selection of the ORC and PCM technologies are performed.
Techno-economic analysis of diesel, natural gas, electric and hydrogen buses
Authors: Zuccari Fabrizio , Santiangeli Adriano , Rampini Andrea , Orecchini Fabio , Bocci Enrico
Published: December 2024

Many regions and cities are implementing Electric (BEB – Battery Electric Bus) and hydrogen (FCB – Fuel Cell Bus) buses instead of the diesel (Diesel) and natural gas (CNG – Compressed Natural Gas) traditional ones. Many papers and reports compare the different Total Cost of Ownership of these buses but not always clarify mission, powertrain and context data. This study, starting from literature analysis, referring to a specific typical urban bus mission (17 km/h average speed per 12 h daily service), quotes techno-economic-environmental buses (purchase, maintenance, energy consumption and CO2 emissions costs), powertrains (combustion engine, battery, fuel cells, hydrogen storage) and context (diesel, CNG, electricity, hydrogen costs) data. Furthermore, a comparative analysis is carried out considering different operational scenarios based on high or low consumptions, high or low electricity costs, three hydrogen production ways and current (current, batteries and hydrogen technologies costs) and future (15% increase of diesel and CNG costs and decrease of batteries and hydrogen technologies costs) so evaluating 24 scenarios. The results shows that TCO is mainly constituted by every year costs (i.e. maintenance plus emissions and energy consumption,) respect to the one-time cost (so divided by the lifetime, i.e. purchase costs) except in the more competitive hydrogen scenarios where these 3 costs correspond equally to a 30% of the overall TCO. Thus, the bus choice, have to be made on the specific technologies and energies context costs instead on the international buses purchase cost. In fact, it is not possible to define a best technology for any scenario, especially for the future scenarios (so with a variation of diesel, CNG, battery, fuel cells, electricity and hydrogen costs). The best technology will depend on the specific context, and so specific analysis have to be made before to choose the technology to be applied. Indeed, CNG in the current scenarios is always the best technology followed by diesel, but CNG and diesel have emission costs and fossil fuel cost are expected to increase. BEB in the current and future scenarios are never the best technologies but it can be the best technology in scenarios with lower autonomy. FCB in the future scenarios are the best technology for 10 of the 12 scenarios analysed, that it is possible to say that FCB, taking into account the great possibilities of hydrogen production and the flexibility in power and energy respect the electric, even with the lower powertrain efficiencies respect to electric, is a technology that can be applied in many different contexts.
Analysis of limitations of tomographic BOS measurements in a lean H2-air premixed flame
Authors: Iapaolo F , Cozzi F , Cárdenas Barrera O F , Orlando M
Published: December 2024

Background Oriented Schlieren (BOS) is an optical technique that visualizes and quantifies refractive index gradients in transparent media, used extensively in studying compressible flows, heat transfer, and combustion. The refractive index field can be converted to a density field using the Lorentz-Lorenz or Gladstone-Dale equations. Recently, the tomographic version of BOS has gained attention for its application in these fields. Sipkens et al. proposed the ARAP method for tomographic BOS, which improves reconstruction accuracy by accounting for light rays converging at the camera pinhole, a common setup with entocentric lenses. This study aims to assess the limitations of tomographic BOS reconstruction using numerical simulations of an axisymmetric hydrogen Bunsen flame, comparing the results with experimental BOS measurements. It has been observed that the constant composition assumption (i.e., assuming a unique value of the Gladstone-Dale constant independently from composition) may introduce some limited errors, whereas the implementation of the ARAP algorithm has a negligible impact on the computation of temperature distribution.
Temperature monitoring strategy for microclimate prediction in low-automation greenhouses: a preliminary analysis
Authors: Miserocchi Lorenzo , Caposciutti Gianluca , Franco Alessandro , Tellini Bernardo
Published: December 2024

Climate control strategies in low-automation greenhouses typically rely on the measurements from a single sensor. Indeed, implementing more complex monitoring devices and sensor networks may increase investment costs without necessarily improving profitability. This paper presents a low cost and low complexity temperature monitoring strategy, which is illustrated in a case study of tomato cultivation during the mid-season in a traditional Mediterranean greenhouse located in Pisa, Italy. The objective is to evaluate the temperature distribution within a portion of the greenhouse and to investigate the representativeness of single-point measurements for assessing the local microclimate. During the experimental campaign, the vertical and horizontal temperature differences reached maximum values of 9.9 °C and 7.3 °C, respectively. The performed temperature measurements appear to be correlated (R2 > 0.95), and this information was exploited for the prediction of the greenhouse temperature in multiple points, resulting in an average RMSE of 1.3 °C, with differences depending on the specific position taken as reference. These findings offer insights into the representativeness of single-point measurements and the optimal positioning of the sensor station within the greenhouse. The inclusion of microclimate heterogeneity in climate control strategies can help minimise the local presence of unfavourable growth conditions, the excess of energy use, and installation and maintenance costs.
Development of a test rig for the study of gas-based nanofluids
Authors: Milanese Marco , Faraz Muhammad , Colangelo Gianpiero , Risi Arturo de
Published: December 2024

Nanofluids, comprising nanoparticles suspended in conventional heat transfer fluids, reveal significant increase in thermal conductivity and convective heat transfer. This research article investigates the application of gas-based nanofluid in concentrated solar power plant (CSP) technologies. Traditional heat transfer fluids, like synthetic oil and molten salts, present limitations such as flammability, toxicity and operational temperature. In contrast, gas-based nanofluids show improved thermal and optical properties making them a promising alternative for high-temperature solar applications. In this research, an innovative open circuit test bench operating with gas-based nanofluid as heat transfer fluid is presented. Particularly, an open circuit test bench was designed for experimental analysis, incorporating a solar simulator to control sunlight intensity in a laboratory setting. A theoretical model was developed based on solar simulator irradiance, and numerical analysis was conducted. Nanofluids containing CuO nanoparticles exhibited an optimal extinction distance within a few centimeters at a volume concentration of 0.50f. Besides, also the temperature increase achievable with this concentration of nanoparticles is compatible with various thermal and electrical power generation applications.
Effect of combined refrigerant leakage and HEX fouling on performances on an air-to-air EHP in different Italian Climates
Authors: Mastrullo Rita , Mauro Alfonso William , Pelella Francesco , Trinchieri Raniero , Viscito Luca
Published: December 2024

The use of heat pumps for the needs related to the heating and cooling in the building sector has largely increased and it is expected to increase more with the limitations in the use of burners. Even though the use of heat pumps has, generally, a reduced environmental impact, it is important to preserve the performance of the machine during its lifetime to control the direct and indirect environmental impact. In this regard, the effect of some soft faults is relevant, such as refrigerant leakage and heat exchanger fouling, which may contribute to highly degrade system performances, since their evolution often remains unidentified for long periods of time. In particular, it is important to quantify the potential performance degradation that faults may cause on heat pump systems, as well as to identify the most influencing parameters for implementing monitoring strategies.

This work analyzes the effect of these three faults on the behavior of an air-to-air reversible electric heat pump for domestic heating and cooling, both on actual performance and heating/cooling capacity, and of seasonal performance in five different Italian climate conditions of Courmayeur, Milan, Rome, Palermo, Pantelleria. Results show the effect of standalone and combined soft faults on both actual system performance and capacity in heating and cooling operating modes, analyzing counterbalance and superposition effects. Also, the results of lifetime (12 years) performance are presented assuming for each climate condition different scenarios of fault evolution and maintenance strategy.
Steady-state model of Vapour Compression Systems for Refrigeration Applications
Authors: Roberti Giovanni , Giovannini Michael , Molinaroli Luca , Lorenzini Marco
Published: December 2024

This work focuses on the model of steady-state vapour compression systems (VCSs), to provide a useful and simple tool to evaluate their performance, both during the design and tuning phase, but also for the control strategy definition and automatic fault detection applications. The main issue faced in the modelling of such systems is related to the dependence of the thermophysical properties of the fluids on the local temperature conditions, which in turn determines a dependence of the transport coefficients which must be solved iteratively. In this work, a solution algorithm for the non-linear system of equations that describes the system behaviour is developed. The model is validated through experimental data obtained for an experimental refrigeration loop employing a zeotropic mixture, R450A. Comparison of the experimental and computed data of pressure, temperature and mass flowrate is demonstrated to be quite satisfactory.
Energy Balance of a Renewable Energy Community Using Stochastic Methods, a Case Study in Genoa City
Authors: Bocanegra Johan Augusto , Pallavidino Emanuela , Schenone Corrado
Published: December 2024

Renewable energy is at the core of decarbonization; some strategies that could impulse a rapid adoption of those energy systems implies the sharing of the produced energy. Renewable Energy Communities are organizations of different stakeholders (citizens, public entities, authorities, companies) that share energy produced in one or more renewable energy implants of some prosumers that participate in this collective. In this paper, we perform some numerical analysis based on a stochastic analysis of energy consumption and production data; this methodology was implemented to study the performance of a community located in Genoa; in this case, study, the focus is on the energy balance and derive an approximative self-consumption factor.