Advanced Technologies for Green Hydrogen Production

Hydrogen represents a versatile fuel that has found usage in several sectors, such as automotive, aerospace, chemical industries, etc. Today, fossil fuels, due to their high hydrogen content, are the dominant source of hydrogen production and steam methane reforming is the most widely used technology: over 95% of the current production of hydrogen is based on the reforming of fossil fuels. However, in the near future, in order to reduce fossil CO2 emissions, hydrogen production is expected to gradually shift toward green solutions

A Critical Analysis of the Oxy-Combustion Process: From Mathematical Models to Combustion Product Analysis

Fossil fuels are the most widely used resource for energy production. Carbon dioxide (CO2) emissions are correlated with climate change, and therefore these emissions must be reduced in the future. It is possible by means of many different technologies, and one of the most promising seems to be oxyfuel combustion. This process, with oxygen and recirculating gas, produces a concentrated stream of CO2 and water. In recent years, many scientists carried out research and studies on the oxyfuel process, but a sufficient level of knowledge was not yet reached to exploit the great potential of this new technology. Although such areas of research are still highly active, this work provides an overview and summary of the research undertaken, the state of development of the technology, and a comparison of different plants so far

Experimental Evaluation of a Full-Scale HVAC System Working with Nanofluid

Nowadays, energy saving is considered a key issue worldwide, as it brings a variety of benefits: reducing greenhouse gas emissions and the demand for energy imports and lowering costs on a household and economy-wide level. Researchers and building designers are looking to optimize building efficiency by means of new energy technologies. Changes can also be made in existing buildings to reduce the energy consumption of air conditioning systems, even during operational conditions without dramatically modifying the system layout and have as low an impact as possible on the cost of the modification. These may include the usage of new heat transfer fluids based on nanofluids. In this work, an extended experimental campaign (from February 2020 to March 2021) has been carried out on the HVAC system of an educational building in the Campus of University of Salento, Lecce, Italy. The scope of the investigation was comparing the COP for the two HVAC systems (one with nanofluid and the other one without) operating concurrently during winter and summer: simultaneous measurements on the two HVAC systems show that the coefficient of performance (COP) with nanofluid increased on average by 9.8% in winter and 8.9% in summer, with average daily peaks of about 15%. Furthermore, the comparison between the performance of the same HVAC system, working in different comparable periods with and without nanofluids, shows a mean increase in COP equal to about 13%

Numerical Evaluation of a HVAC System Based on a High-Performance Heat Transfer Fluid

none4Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working conditions of the HVAC system that lead to lower operating costs and higher COP and EER, guaranteeing the optimal conditions of thermo-hygrometric comfort inside the building. Finally, the results showed that the use of a nanofluid based on water-glycol mixture and alumina increases the efficiency about 10% and at the same time reduces the electrical energy consumption of the HVAC system.openColangelo, Gianpiero; Raho, Brenda; Milanese, Marco; de Risi, ArturoColangelo, Gianpiero; Raho, Brenda; Milanese, Marco; de Risi, Artur

numerical optimization of spr sensors for lube oil real time optical characterization in large 2 stroke marine diesel engines

Abstract Lubrication of large two stroke marine diesel engines typically is performed by specially blended lubricants with high CaCO 3 concentration in order to prevent sulphuric acid corrosion. The feed rate of lubricant, which is injected into the engine, is strictly related to neutralization reaction of sulphuric acid. At the state of the art, its amount is established following a function of engine load and sulphur content of fuel oil, but regardless the stoichiometric quantity needed to neutralize acid corrosion effects. As result of this lubrication strategy, feed rate of lubricant often results higher than the minimum stoichiometric quantity, yielding unnecessary costs, but sometimes feed rate of lubricant and its content of CaCO 3 cannot be enough to completely neutralize sulphuric acid, producing corrosion. Taking into account that concentration of CaCO 3 within lube oil can be estimated by measuring refractive index, this work aimed to study SPR sensors, capable to measure in real time small variation of lubricant optical properties, in order to adjust lubricant feed rate, according to the real needs of neutralization. Therefore, a numerical optimization of SPR sensors for lube oil characterization has been carried out, analysing several cases, different for laser source, optical prism and thickness of 3 metal film layers. Mathematical results allowed to find the best sensor in terms of sensitivity. This work is the first step towards the development of a semi-closed loop lubrication control system

Numerical method for wind energy analysis applied to Apulia Region, Italy

A numerical method, named WEST (Wind Energy Study of Territory), has been developed and applied to a specific geographical area in south of Italy. This method, through actual historical meteorological and geophysical data of a territory, allows characterizing anemometric fields and, therefore, potential available wind power. WEST has been developed in such a way to be effective in both studies of large area and siting. Particularly, this method is composed by different calculation algorithms, which altogether constitutes the numerical model, which allow obtaining useful information on the technical feasibility of installing wind turbine in an area. In this work, by means of WEST, three-dimensional wind fields of Apulia Region (Italy) have been reconstructed, obtaining the wind power density maps at several heights: 35 m, 60 m, 80 m and 100 m above ground level

A Critical Review of Experimental Investigations about Convective Heat Transfer Characteristics of Nanofluids under Turbulent and Laminar Regimes with a Focus on the Experimental Setup

In this study, several experimental investigations on the effects of nanofluids on the con- vective heat transfer coefficient in laminar and turbulent conditions were analyzed. The aim of this work is to provide an overview of the thermal performance achieved with the use of nanofluids in various experimental systems. This review covers both forced and natural convection phenomena, with a focus on the different experimental setups used to carry out the experimental campaigns. When possible, a comparison was performed between different experimental campaigns to provide an analysis of the possible common points and differences. A significant increase in the convective heat transfer coefficient was found by using nanofluids instead of traditional heat transfer fluids, in general, even with big data dispersion from one case to another that depended on boundary condi- tions and the particular experimental setup. In particular, a general trend shows that once a critic value of the Reynolds number or nanoparticle concentrations is reached, the heat transfer perfor- mance of the nanofluid decreases or has no appreciable improvement. As a research field still under development, nanofluids are expected to achieve even higher performance and their use will be crucial in many industrial and civil sectors to increase energy efficiency and, thus, mitigate the en- vironmental impact

Thermo-physical properties of paraffin wax with iron oxide nanoparticles as phase change material for heat storage applications

Phase change materials (PCMs) are growing in importance in many thermal applications as heat storage or to smooth the energy peak demand in many technological fields in industrial as well as in civil applications. Conductive nanoparticles can be added to phase change material to improve their thermo-physical properties. In this work, Iron oxide nanoparticles (IOx-NPs) were synthesized using a simple and green synthesis method, free of toxic and harmful solvents, using the extract of a plant as a reducer and stabilizer at two different temperatures of calcination 500°C and 750°C. The metallic oxide was used as an additive with 2% wt. compositions to paraffin wax to prepare a nanocomposite. The variation in thermal properties of paraffin wax in the composite was experimentally investigated. The biosynthesized IOx-NPs were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and Thermal Gravimetric Analysis (TGA) techniques. The thermal properties of the synthesized nanocomposites were characterized by a thermal conductivity analyzer and differential scanning calorimetry (DSC). The FTIR spectra showed a bond at 535 cm-1, which confirms the Fe-O vibration. The XRD powder analysis revealed the formation of the cubic phase of Fe3O4 with an average particle size of 11 nm at 500°C and the presence of the phase a-Fe2O3 with Fe3O4 at 750°C. Scanning Electron Microscopy (SEM) showed that the obtained oxide was made up of particles of nanoscale size. Experimental measurements showed that the presence of nanoparticles can improve the latent heat capacity by a maximum of 16.16 % and the thermal conductivity of the nanocomposites by a maximum of 16.99%. © Published under licence by IOP Publishing Ltd.Peer ReviewedPostprint (published version

Progresses in Analytical Design of Distribution Grids and Energy Storage

In the last years, a change in the power generation paradigm has been promoted by the increasing use of renewable energy sources combined with the need to reduce CO2 emissions. Small and distributed power generators are preferred to the classical centralized and sizeable ones. Accordingly, this fact led to a new way to think and design distributions grids. One of the challenges is to handle bidirectional power flow at the distribution substations transformer from and to the national transportation grid. The aim of this paper is to review and analyze the different mathematical methods to design the architecture of a distribution grid and the state of the art of the technologies used to produce and eventually store or convert, in different energy carriers, electricity produced by renewable energy sources, coping with the aleatory of these sources