Over the past few decades, the aerodynamic improvements of turbocharger turbines contributed significantly to the overall efficiency augmentation and the advancements in downsizing of internal combustion engines. Due to the compact size of automotive turbochargers, the experimental measurement of the complex internal aerodynamics has been insufficiently studied. Hence, turbine designs mostly rely on the results of numerical simulations and the validation of zero-dimensional parameters as efficiency and reduced mass flow. To push the aerodynamic development even further, a precise validation of three-dimensional flow patterns predicted by applied computational fluid dynamics (CFD) methods is in need. This paper presents the design of an up-scaled volute-stator model, which allows optical experimental measurement techniques. In a preliminary step, numerical results indicate that the enlarged geometry will be representative of the flow patterns and characteristic non-dimensional numbers a... [more]

The flow of energy within external gear machines (EGMs) leads to the variation of fluid temperature in the EGMs, which affects their performance. However, the common approaches for the simulation of EGMs assume isothermal conditions. This isothermal assumption negatively impacts their modelling accuracy in terms of the internal flows which are dependent on the fluid temperature (via fluid properties). This paper presents a lumped parameter based thermal model of EGMs where the fluid temperature in the EGM is evaluated considering the effects of compression/expansion, internal flows, and power losses. Further, numerical techniques are developed to model each of these three aspects. The thermal model is validated via the outlet temperature and volumetric efficiency measurements obtained from experiments conducted on six units of an EGM taken as a reference with different internal clearances. The results from the model show that the fluid temperature increases as it is carried from the in... [more]

The volume of magnetic components for space applications, directly related to the launch cost, and their performance are critically influenced by their capability to dissipate the internal electromagnetic power losses. This is the reason why accurate thermal models are required. Furthermore, these models need to be simple and versatile to allow a fast analysis of many different designs. In this study, a specific methodology to analyze inductors and transformers by thermal networks and a simplification based on the Thevenin’s theorem leading to a simple equation are proposed. The specific details to address thermal modelling for space magnetic components are discussed. A generic 50 W Flyback transformer for space applications is analyzed in this study and experimental validation is provided, showing that the proposed method leads to a deviation in the temperature estimation between 1 °C and 5 °C, which is considered quite a good result from the literature review carried out.

In this paper the energy performances carried out by an investigation conducted on a Heating, Ventilation and Air Conditioning (HVAC) system, composed by an Air Handling Unit (AHU) for the primary air coupled with a horizontal-pipes Ground-to-Air Heat eXchanger (GAHX) and fan-coil units, for an office building, supposed to be placed in four different cities (Rio de Janeiro, Dubai, Naples, Ottawa) belonging to four different worldwide climatic areas, according to the Köppen climate classification. The investigation is performed by means of a two dimensional numerical model, experimentally validated, of an GAHX solved with finite element method. The results introduced in this paper are carried out by varying the length of the pipes and the air flow velocity; thus, also the number of tubes forming the GAHX is varied since the volumetric flow rate to be provided to the AHU must be kept constant. The energy performances of the above-mentioned HVAC system are analyzed, both in summer and in... [more]

This study addresses the thermal and energy performance assessment of a Building Integrated Photovoltaic Thermal (BIPVT) system installed on the façade of a test room in Solar XXI, a Net Zero Energy Building (NZEB) located in Lisbon, Portugal. A numerical analysis using the dynamic simulation tool EnergyPlus was carried out for assessing the performance of the test room with the BIPVT integrated on its façade through a parametric analysis of 14 scenarios in two conditions: a) receiving direct solar gains on the glazing surface and b) avoiding direct solar gains on the glazing surface. Additionally, a computational fluid dynamics (CFD) analysis of the BIPVT system was performed using ANSYS Fluent. The findings of this work demonstrate that the BIPVT has a good potential to improve the sustainability of the building by reducing the nominal energy needs to achieve thermal comfort, reducing up to 48% the total energy needs for heating and cooling compared to the base case. The operation mo... [more]

Introduced by the Civil Code, the rules of road safety are introducing continuously increasingly strict requirements on motor vehicles. These requirements relate to various aspects of the technical condition of vehicles, both those that determine traffic safety and those that affect the vehicle’s environmental impact. The law requires regular diagnosis of the technical condition of vehicles in service. Diagnostic tests conducted in the form of road tests or the tests performed in workshop conditions allow to determine the symptoms of dysfunctions of the tested vehicle, not always clearly defining the causes and location of damage. The purpose of the work is the design the simulation of a station for of vehicle dynamics tests up to 3.5 t using simulation programs OpenModelica and SciLab. A simulation of the work of the stand for testing the dynamics of vehicles in the form of a chassis dynamometer was achieved. The program enables the simulation of tests: NEDC (New European Drive Cycle)... [more]

The formation of an inlet vortex seriously restricts axial-flow pump device performance and poses a great threat to the safe and stable operation of the entire system. In this study, the change trends of an inlet vortex and its influence on an axial-flow pump are investigated numerically and experimentally in a vertical axial-flow pump device. Four groups of fixed vortex generators (VGs) are installed in front of the impeller to create stable vortices at the impeller inlet. The vortex influence on the performance of pump device is qualitatively and quantitatively analyzed. The vortex patterns at different positions and moments in the pump device are explored to reveal the vortex shape change trend in the impeller and the pressure fluctuation induced by the vortex. The reliability and accuracy of steady and unsteady numerical results are verified by external characteristics and pressure fluctuation experimental results. Results show that it is feasible to install VGs before the impeller... [more]

The research on two-stroke engines has been focused lately on the development of direct injection systems for reducing the emissions of hydrocarbons by minimizing the fuel short-circuiting. Low temperature combustion (LTC) may be the next step to further improve emissions and fuel consumption; however, LTC requires unconventional ignition systems. Jet ignition, i.e., the use of prechambers to accelerate the combustion process, turned out to be an effective way to perform LTC. The present work aims at proving the feasibility of adopting passive prechambers in a high-pressure, direct injection, two-stroke engine through non-reactive computational fluid dynamics analyses. The goal of the analysis is the evaluation of the prechamber performance in terms of both scavenging efficiency of burnt gases and fuel/air mixture formation inside the prechamber volume itself, in order to guarantee the mixture ignitability. Two prechamber geometries, featuring different aspect ratios and orifice number... [more]

Polymer electrolyte membrane fuel cells (PEMFCs) are often used for household applications, utilizing hydrogen produced from natural gas from the gas grid. The hydrogen is thereby produced by steam reforming of natural gas followed by a water gas shift (WGS) unit. The H2-rich gas contains besides CO2 small amounts of CO, which deactivates the catalyst used in the PEMFCs. Preferential oxidation has so far been a reliable process to reduce this concentration but valuable H2 is also partly converted. Selective CO methanation considered as an attractive alternative. However, CO2 methanation consuming the valuable H2 has to be minimized. The modelling of selective CO methanation in a household fuel cell system is presented. The simulation was conducted for single and two-stage adiabatic fixed bed reactors (in the latter case with intermediate cooling), and the best operating conditions to achieve the required residual CO content (100 ppm) were calculated. This was done by varying the gas in... [more]

Recently, the concept of “circular economy”, the design for end-of-life, the problem of reduction of waste of electronic and electrical equipment are becoming more and more important. The design of electronic systems for end-of-life considers the possibility of their repair, reuse and recycle, in order to reduce waste. This work proposes a new accurate model of failure probability density, that includes the failure probability of a used component in new equipment. The model has been tested, in conjunction with the International Electrotechnical Commission and Telcordia standard, in real industrial production. Eight years of historical faults have been analyzed and used to derive the fault models of the components. The model and analysis have been used for the analysis of real electronic products. The reuse of components could make an improvement to the reliability of the equipment.

The building sector contributes approximately one third of the total energy consumption worldwide. A large part of this energy is used for the heating and cooling of buildings, which can be drastically reduced by use of energy-efficient glazing. In this study, we performed building energy simulations on a prototypical residential building, and compared commercially available static (low-e, solar IR blocking) to newly developed adaptive thermochromic glazing systems for various climate regions. The modeling results show that static energy-efficient glazing is mainly optimized for either hot climates, where low solar heat gain can reduce cooling demands drastically, or cold climates, where low-e properties have a huge influence on heating demands. For intermediate climates, we demonstrate that adaptive thermochromic glazing in combination with a low-e coating is perfectly suited. The newly developed thermochromic glazing can lead to annual energy consumption improvement of up to 22% in c... [more]

Energy communities are key elements in the energy transition at the local level as they aim to generate and distribute energy based on renewable energy technologies locally. The literature on community energy systems is dominated by the study of electricity systems. Yet, thermal energy applications cover 75% of the total energy consumption in households and small businesses. Community-driven initiatives for local generation and distribution of thermal energy, however, remain largely unaddressed in the literature. Since thermal energy communities are relatively new in the energy transition discussions, it is important to have a better understanding of thermal energy community systems and how these systems function. The starting point of this understanding is to study factors that influence the formation and continuation of thermal energy communities. To work towards this aim, an abstract agent-based model has been developed that explores four seemingly trivial factors, namely: neighborh... [more]

Background: The aim of our study was to identify an optimal heating system for the analyzed church. We also evaluated the energy consumption of the existing system and of those proposed in order to choose the best heating system. Methods: We analyzed the current existing heating system, a mixed system (static heaters and hot air heating) in a Romanian heritage church, build in the 16th century, and we compared it with an underfloor heating system that has been mentioned in the literature as an alternative for church heating. We used a computational fluid dynamics (CFD) analysis of the indoor climate with two turbulence models (k-ε and k-ω). Results: Comparing the two heating systems through boxplot graphs, we could highlight pertinent conclusions regarding the temperatures and velocities of the measured air currents. Thus, of all the heating systems, the underfloor heating had the lowest temperatures, but the highest air velocities, in the churchgoers area, especially under the towers... [more]

Capacity markets (CM) are energy markets created to ensure energy supply security. Energy storage devices provide services in the CMs. Li-ion batteries are a popular type of energy storage device used in CMs. The battery lifetime is a key factor in determining the economic viability of Li-ion batteries, and current approaches for estimating this are limited. This paper explores the potential of a lithium-ion battery to provide CM services with four de-rating factors (0.5 h, 1 h, 2 h, and 4 h). During the CM contract, the battery experiences both calendar and cycle degradation, which reduces the overall profit. Physics-based battery and degradation models are used to quantify the degradation costs for batteries in the CM to enhance the previous research results. The degradation model quantifies capacity losses related to the solid−electrolyte interphase (SEI) layer, active material loss, and SEI crack growth. The results show that the physics-based degradation model can accurately predi... [more]

This paper presents a study on the impact of adjacent markets on the electricity market, realizing the advantages of acting in several different markets. The increased use of renewable primary sources to generate electricity and new usages of electricity such as electric mobility are contributing to a better and more rational way of living. The investment in renewable technologies for the distributed generation has been creating new opportunities for owners of such technologies. Besides the selling of electricity and related services (ancillary services) in energy markets, players can participate and negotiate in other markets, such as the carbon/CO2 market, the guarantees of origin market, or provide district heating services selling of steam and hot water among others. These market mechanisms are related to the energy market, originating a wide market strategy improving the benefits of using distributed generators. This paper describes several adjacent markets and how do they complem... [more]

Three Ni-based natural gas steam reforming catalysts, i.e., commercial JM25-4Q and JM57-4Q, and a laboratory-made catalyst (26% Ni on a 5% SiO2−95% Al2O3), are tested in a laboratory reactor, under carbon dioxide methanation and methane steam reforming operating conditions. The laboratory catalyst is more active in both CO2 methanation (equilibrium is reached at 623 K with 100% selectivity) and methane steam reforming (92% hydrogen yield at 890 K) than the two commercial catalysts, likely due to its higher nickel loading. In any case, commercial steam reforming catalysts also show interesting activity in CO2 methanation, reduced by K-doping. The interpretation of the experimental results is supported by a one-dimensional (1D) pseudo-homogeneous packed-bed reactor model, embedding the Xu and Froment local kinetics, with appropriate kinetic parameters for each catalyst. In particular, the H2O adsorption coefficient adopted for the commercial catalysts is about two orders of magnitude hig... [more]

Air quality and energy consumption are among the top ten environmental priorities in seaports as stated by the European Sea Ports Organization. Globally, it is estimated that 15% of energy consumption can be attributed to refrigeration and air conditioning systems in fishing activities. There is a real need to understand energy usage in fishery ports to help identify areas of improvements, with a view to optimize energy usage and minimize carbon emissions. In this study, we elaborate on ways in which a simulation capability can be developed at the community level with a fishery port, using a real-world case study seaport in Milford Heaven (Wales, UK). This simulation-based strategy is used to investigate the potential of renewable energy, including local solar farms, to meet the local power demand. This has informed the development of a simulation-based optimization strategy meant to explore how smart energy communities can be formed at the port level by integrating the smart grid with... [more]

An integrated energy system, referred to specifically as a heterogeneous energy system that combines cooling, heating, power, etc., is a dynamic system containing continuous as well as discrete behaviors on both technical and economic levels. Currently, the comprehensive utilization of multiple forms of energy and the implementation of the energy market have made the simulation of such a system very complicated, which is reflected in two aspects. First, the simulation model becomes complex and varied. Second, the time-varying characteristics of the models are quite diverse. Therefore, a standard and normative modeling and simulation method is urgently needed. This work aims to obtain a compatible modeling and simulation method for the energy economy coupling system. The individual-based model is widely used to describe organisms in an ecology system that are similar to the energy−economy coupled system. Inspired by this, a general simulation approach based on the individual-based model... [more]

This paper presents a compact nonlinear thermal model of pulse transformers. The proposed model takes into account differentiation in values of the temperatures of a ferromagnetic core and each winding. The model is formulated in the form of an electric network realising electrothermal analogy. It consists of current sources representing power dissipated in the core and in each of the windings, capacitors representing thermal capacitances and controlled current sources modelling the influence of dissipated power on the thermal resistances in the proposed model. Both self-heating phenomena in each component of the transformer and mutual thermal couplings between each pair of these components are taken into account. A description of the elaborated model is presented, and the process to estimate the model parameters is proposed. The proposed model was verified experimentally for different transformers. Good agreement between the calculated and measured waveforms of each component temperat... [more]

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants using organic fluids for electricity “production” or in cogeneration configuration. The improvement in the use of geothermal aquifers at low-medium enthalpy in small deep sites favours the reduction of drilling well costs, and in addition, it allows the exploitation of local resources in the energy districts. The heat exchanger evaporator enables the thermal heat exchange between the working fluid (which is commonly an organic fluid for an Organic Rankine Cycle) and the geothermal fluid (supplied by the aquifer). Thus, it has to be realised taking into account the thermodynamic proprieties and chemical composition of the geothermal field. The geothermal fluid is typically very aggressive, and it lea... [more]

This work addresses the effect of the total solar reflectance (TSR) value of paints applied in residential buildings upon their thermal performance. A semi-detached residential building was modeled in the ESP-r software, and taken as the basis for parametric studies which assessed the effects of variations in (i) the TSR values; (ii) the thermal characteristics of the building envelope; (iii) the location/climate; and: (iv) the way how the indoor temperature is controlled. The parametric studies were used to find optimal TSR values for each combination of Location + Building envelope characteristics (mainly the existence of thermal insulation). It was concluded that paints having a carefully chosen TSR value lead to better indoor thermal temperatures if the buildings have no mechanical heating or cooling, or to energy savings of up to 32% if they do.

This paper evaluates the liquid water at the gas diffusion layer-channel (GDL-channel) interface of reconstructed GDL microstructures with uniform and non-uniform fiber diameters in wave-like channels. A non-uniform GDL microstructure is reconstructed for the first time at the GDL-channel interface to evaluate droplet motion. The three-layer GDL microstructures are generated using the stochastic technique and implemented using the OpenFOAM computational fluid dynamics (CFD) software (OpenFOAM-6, OpenFOAM Foundation Ltd., London, UK). The present study considers the relationship between reconstructed GDL surfaces with varying fiber diameters, wettability, superficial inlet velocity and droplet size. Results show that the droplet detachment and the average droplet velocity decrease with an increase in the fiber diameter as well as the structural arrangement of the fibers. Under the non-uniform fiber arrangement, the removal rate of water droplets is not significantly improved. However, t... [more]

The existence of an efficient and sufficiently extensive charging infrastructure network appears to be of vital importance for the widespread acceptance of electric mobility by users. The present work aims to develop a tool based on big data analysis that helps to deploy a network of charging stations which can efficiently serve the potential demand, both from the user side, improving the level of service for charging and to cover the territory in a satisfactory way, and from the business side, allowing an analysis of the potential power load. The paper integrates real world traffic data and the results of an experimental campaign on an electric vehicle to evaluate the instantaneous power demand of a fast charging station, based on a procedure for the evaluation and proper time allocation of each charge request.

The aim of the present paper is to investigate the use of the site “Potamon” Dam in the Prefecture of Rethymnon, Crete island, Greece, as a “virtual” renewable electricity supply of a pumped storage plant (PSP) in order to save and exploit the maximum possible part of the rejected wind energy of the autonomous power system of the Crete island. Taking into account the annual time series of the rejected power of the Crete power grid, the present research work targets the optimal configuration of the proposed PSP power station, including the sizing of its individual components as well as the determination of the capacity it could guarantee in order to be economically viable. The rejected electric energy from the actually operating wind farm production, which is not possible to be absorbed by the grid of Crete due to its stable operation limitations, could be absorbed by the here proposed pump storage plant (PSP) and converted to hydraulic energy. This can be achieved by pumping the water... [more]

The aim of this work is the development of a simulation model for the anaerobic digestion process of source-sorted organic fractions of municipal solid wastes. In particular, a detailed model simulating both biological and thermal behaviors of the process was developed. The biological model is based on the Anaerobic Digestion Model 1 (ADM1), which allows one to evaluate the dynamic trends of the concentrations of the main components and the biogas production as a function of the digester operating temperature. The work also includes a detailed thermal model which is developed considering the geometrical and structural features of the digester. The thermal behavior of the digester was also modeled, considering a purposely designed heat exchanger immersed inside the digester. Therefore, the thermal behavior of the process was evaluated by the well-known heat exchange equations and thermal energy balances. The combination of these two models is used to analyze the different possible opera... [more]