Proton exchange membrane (PEM) technology may regulate the electrical grid connected to intermittent power sources. The growing pace of R&D in alternative components is widening manufacturing methods and testing procedures across the literature. This turns the comparison between performances into a more laborious task, especially for those starting research in this area, increasing the importance of testing components accessible to all. In this study, an electrochemical characterization is performed on a commercial single-cell PEM water electrolyzer with commercial catalyst-coated membranes (CCMs) and one prepared in-house. Two membrane thicknesses and the effect of different catalysts are assessed. The thicker membrane, Nafion 117, operates with 5% greater ohmic overvoltage than the thinner Nafion 115, resulting in up to 1.5% higher voltage for the former membrane. Equivalent Ir black CCMs provided by different suppliers and one prepared in-house perform similarly. Regarding the influ... [more]

The power produced in a photovoltaic (PV) system is highly dependent on meteorological conditions and the features of the connected load. Therefore, maximum power point tracking (MPPT) methods are crucial to optimize the power delivered. An MPPT method needs a DC-DC converter for its implementation. The proper selection of both the MPPT technique and the power converter for a given scenario is one of the main challenges since they directly influence the overall efficiency of the PV system. This paper presents an exhaustive study of the performance of four step-down/step-up DC-DC converter topologies: Buck-Boost, SEPIC, Zeta and Cuk, using three of the most commonly implemented MPPT techniques: incremental conductance (IncCond), perturb and observe (P&O) and fuzzy logic controller (FLC). Unlike other works available in the literature, this study compares and discusses the performance of each MPPT/converter combination in terms of settling time and tracking efficiency of MPPT algorithms,... [more]

In electric vehicle (EV) applications, hybrid excitation of switched reluctance motors (HESRMs) are gaining popularity due to their advantages over other EV motors. The benefits include control flexibility, simple construction, high torque/power density, and the ability to operate over a broad speed range. However, modern HESRMs are constructed by increasing the air gap flux density with permanent magnets (PMs) in the excitation system in order to generate more electromagnetic torque. This study aims to investigate a new topology for increasing the torque capabilities of HESRM without the use of permanent magnets (PMs) or other rare-earth components. This paper provides a comprehensive evaluation of the static and dynamic characteristics, software analysis using the Ansys 2D finite element method (FEM), and an experimental demonstration of the real-time motor with an advanced control strategy in MATLAB/Simulink. Our simulation and experimental results for a machine with 12/8 poles and... [more]

Quantitative and qualitative analyses of chemical species out of CI engine tailpipe emissions fueled with pure diesel and diesel methanol blends, trapped in dinitro phenylhydrazine (DNPH) solutions, were performed. The formed hydrazine was studied using high-performance liquid chromatography (HPLC) accompanied by a detector for ultraviolet (UV). A set of carbonyl-DNPH derivative standards was developed and compared with engine tailpipe gases produced by both fuel modes. An understanding of carbonyl chemical compounds such as formaldehyde, acetaldehyde, and acrolein (HCHO, CH3CHO, and H2 = CHCHO, respectively) is essential for researchers to know how these chemicals affect human health and the environment. In both fuel modes, acetaldehyde was the main combustible product 25 ppm followed by formaldehyde 17 ppm, croton aldehydes 16 ppm, acrolein 12 ppm, and iso-valerdyhyde 10 ppm. In addition to these species, only a few other chemical species were detected in the exhaust gas. According t... [more]

Non-road sectors, such as agriculture and construction machinery, require high energy densities and flexibility in use, which is why diesel engines are mainly used. The use of climate-neutral fuels, produced from renewable energies, such as Oxymethylene Ether (OME) as a diesel substitute, can significantly reduce CO2 and pollutant emissions in these sectors. In addition to CO2 neutrality, OME also offers improved combustion characteristics compared to diesel fuel, eliminating the soot−NOx trade-off and thus enabling new opportunities in engine design and calibration. In this paper, the combustion of pure OME on a close-to-production, single-cylinder non-road diesel engine with a pump−line−nozzle injection system is analyzed. A variation of the center of combustion at constant power output was performed for diesel and OME at different operating points. Two injectors were investigated with OME. A study on ignition delay and a detailed thermodynamic analysis was carried out. In addition,... [more]

Battery safety tests are defined by several international standards in different ways and with heterogenous termination and failure criteria. In this work, lithium-ion cells were examined regarding their behavior in the event of overcharging and also in the event of an external short circuit with varied parameters specified by standards. The voltage, current, and temperature curves were evaluated. In addition, the changes in the cells were analyzed using electrochemical impedance spectroscopy (EIS). It is shown that the cells exhibit reproducible behavior in a clamped state. Further, it could be determined that the position of the cell opening during an overcharge has an influence on the further behavior of the cell. EIS data showed that the cells have a significantly higher internal resistance after an overcharge. The short-circuit tests at different ambient temperatures indicated that the internal resistance of the cell decreases with increasing temperature. However, no reproducible... [more]

This article provides a brief introduction to the indicators of the volatility and flammability of lubricating oils and fuels. It is proposed that the initial boiling point be used as an indicator of the contamination of lubricating oil with distillate fuel (i.e., diesel biofuel oil) in the context of the rapid detection of explosion risks in the crankcase. Detailed tests were carried out on lubricating oil samples (SAE 30 and SAE 40 grades, which are most commonly used in the lubrication systems of marine trunk engines) diluted with diesel oil at selected mass concentrations (0, 1, 2, 5, 10, 20, 50, and 100%). The oils were tested to determine their relevant properties: the flash point temperature and the initial boiling temperature. The flash point was determined in a closed crucible using the Pensky−Martens method, which is in accordance with PN-EN ISO 2719. The differences between the initial boiling point and the flash point of the tested lubricating oils were determined for diffe... [more]

Currently, power electronics and AC machine drive systems are employed in numerous areas, such as in industrial processes, consumer electronics, electric vehicles (EVs), renewable-energy-source (RES)-based distributed generation (DG) systems, and electric power generation systems. As RESs such as wind and solar are attracting relatively more attention due to environmental issues caused by fossil fuel use, various RESs have been integrated into the utility grid (UG) as DG systems. As a result, the concept of a microgrid (MG), which constructs an electrical power system with DGs, energy storage systems (ESSs), and loads, has emerged. Recently, the DG-based MG has been regarded as a promising and flexible technology for those involved in constructing electric power systems. This article presents future technology and recent developments in applied power electronics. In this Special Issue, “The Recent Development of Power Electronics and AC Machine Drive Systems”, four papers were publishe... [more]

The exhaust heat of energy conversion systems can be usefully recovered by Organic Rankine Cycles (ORC) instead of wasting it into the environment, with benefits in terms of system efficiency and environmental impact. Rankine cycle technology, consolidated in stationary power plants, has not yet spread out into transport applications due to the layout limitations and to the necessity of containing the size and weight of the ORC system. The authors investigated an ORC system bottoming a compression ignition engine for marine application. The exhaust mass flow rate and temperature, measured at different engine loads, have been used as inputs for modeling the ORC plant in a Simulink environment. An energy and exergy analysis of the ORC was performed, as well as the evaluation of the ORC power at different engine loads. Two different working fluids were considered: R1233zd(e), an innovative fluid belonging to the class of hydrofluoroolefin, still in development but interesting due to its l... [more]

The option of wireless energy transmission in electric vehicles can become the main market driver for electric vehicles due to its distinct advantages, such as range, weight, or costs, over conventional conductive charging solutions. In addition to the great potential, which different research work and realized systems have already shown, there are new requirements for the associated production networks in the automotive industry which must be addressed at an early stage. Furthermore, no solutions currently exist for the industrial production of these components. This paper presents the main components for the feasibility of wireless power transmission in electric vehicles. In addition, the required value chains and processes for the new components of the inductive power transfer systems, and the final assembly for induction coils, which has been developed at the FAU, will be presented. These include the developing of a winding process on a 15-axis special machine, ultrasonic crimping... [more]

In this study, a PVT-based solar-assisted ground source heat pump (SAGSHP) system with a small size borefield as the long-term heat storage component was energetically evaluated. The mathematical model of the system was formulated in TRNSYS and three cities with distinctive climates were chosen: Athens (Greece); Melbourne (Australia); and Ottawa (Canada). The parametric analyses were carried out for 10 years by varying the number of the PVT collectors and the size of the earth energy bank (EEB). The evaluation of the systems was made via two energy indicators, and the heat flow across the EEB was analyzed. The under-consideration system was found capable of establishing self-sufficiency as regards the energy consumption (renewable power fraction RPF > 1) for all locations. Namely, for Athens, any system with more than four PVT collectors, and for Melbourne, any system with more than eight PVTs was found with an RPF higher than 1, regardless of the EEB size. For Ottawa, self-sufficiency... [more]

Rooftop photovoltaic generation can help cities become key players in the transition to clean energy. The optimal solar photovoltaic production on rooftops depends on two angles: tilt angle and azimuth angle. It is accepted in all studies that the ideal orientation of photovoltaic modules is toward the south (north) in the northern hemisphere (south). In contrast, the determination of the optimum tilt angle is more complex, and there are different equations for its calculation. Most of these equations do not take albedo into account. In this work, 47 Spanish province capitals representing the most populated cities have been studied with different equations for the calculation of the optimum annual tilt angle (Technical report by the Spanish Institute for the Diversification and Saving of Energy (IDAE), Lorenzo’s and Jacobson’s equation) and different types of albedo. Accounting for the geographical and the meteorological conditions of the cities, we analyzed the optimum tilt angle thro... [more]

The design and operation of performant and safe electric vehicles depend on precise knowledge of the behavior of their electrochemical energy storage systems. The performance of the battery management systems often relies on the discrete-time battery models, which can correctly emulate the battery characteristics. Among the available methods, electric circuit-based equations have shown to be especially useful in describing the electrical characteristics of batteries. To overcome the existing drawbacks, such as discrete-time simulations for parameter estimation and the usage of look-up tables, a set of equations has been developed in this study that solely relies on the open-circuit voltage and the internal resistance of a battery. The parameters can be obtained from typical cell datasheets or can be easily extracted via standard measurements. The proposed equations allow for the direct analytical determination of available discharge capacity and the available energy content depending o... [more]

The pumped two-phase cooling method is a practical way to dissipate heat from the battery module. The operating parameters of the cooling system should be investigated thoroughly to improve the performance of the battery thermal management system (BTMS). However, the previous BTMS designs only explored the thermal performance and ignored the electrical performance in the battery module. This study designed a pumped two-phase cooling BTMS with the refrigerant of R1233zd. An electrothermal coupled model was established for a series-connected battery module to predict thermal and electrical behavior. The results showed that the pumped two-phase cooling system could obtain excellent cooling performance with low system pressure under 2C discharging condition. The average temperature of the module and the temperature difference among cells could be maintained under 40 °C and 5 K under a 2C discharging rate. A lower saturation temperature, higher mass flux, and higher subcooling degree could... [more]

As the energy crisis intensifies, the global demand for natural gas is growing rapidly. Liquefied natural gas (LNG) technology is among the delivery solutions with flexible and reliable application prospects and is already a significant field of research in energy utilization. The performance of natural gas liquefaction process has a major influence on the production capacity, energy consumption, economics, and safety of the entire supply chain. Many scholars have conducted numerous studies on various LNG processes and designed many classical processes. This paper summarizes and discusses current research status and development level in the design and optimization of natural gas liquefaction processes in recent years, mainly focusing on cascade liquefaction process, expansion liquefaction process, and mixed refrigerant liquefaction process. The advantages and disadvantages of various liquefaction processes are compared and analyzed in terms of liquefaction capacity, energy consumption,... [more]

The aim of the present study was to investigate the effects of the application of hydrotreated vegetable oil (HVO) mixed with pure duck fat (F100) as fuel, replacing the conventional fossil diesel fuel (D100). The tests were performed using a four-stroke direct injection CI engine diesel engine. Six fuel samples were used: D100, HVO100, F100, as well as three HVO−fat mixtures F25, F50, and F75. To further study the main characteristics of fuel combustion, the AVL BOOST software (Burn program) was applied. The results of experimental studies showed that with the addition of pure fat to HVO, the ignition delay phase increased with an increase in the amount of heat released during the premix combustion phase and the pressure and temperature rise in the cylinder increased; however, the mentioned parameters were not higher as compared to diesel fuel. It was found that as the concentration of fat in the HVO−fat mixtures increases, the viscosity and density increases, while LHV was decreased,... [more]

In this study, an algae biomass gasification process using a dual fluidized bed with combined power and methanol cogeneration was developed. The gasification process was modeled using Aspen Plus and validated using experimental data of two microalgae species (Nannochloropsis oculata and Dunaliella salina) commonly found on the western coast of Saudi Arabia. The impacts of different operating conditions, including the gasifier temperature, steam-to-biomass ratio, and algae-char split ratio, on the compositions of four main gases (CO, CO2, CH4, and H2) were investigated. The results of the parametric studies indicated that the gasification temperature has a significant effect on the composition of the synthesis gas, where 700−850 °C was the ideal operating range for gasification. Altering the ratio of biomass to steam showed a slightly smaller effect on the synthesis gas composition. The char split ratio should be kept below 75% to ensure an adequate heat supply to the process. The propo... [more]

Carbonated water has proven advantages over conventional CO2 injection in terms of arresting free CO2 mobility, low-pressure injection, lower volume requirement, and higher efficiency. The term “engineered water” is designated to selective ion-spiked injection water with the advantage of the ion-exchange reactions with the rock minerals and releasing trapped oil. This article investigated the synergic effect of dissolved CO2 and engineered water for oil recovery and understanding inner mechanisms. Recovery efficiencies were evaluated through coreflood studies, which revealed that the hybrid water could recover 6−10% more oil than engineered water and about 3% more than carbonated water. HP-HT pendant-drop studies show the insignificance of IFT reduction. Wettability change from oil wet to near-water wet is attributed as a significant factor. The dissolution of Ca2+ and Mg2+ and deposition of SO42− observed in coreflooding may have a significant contribution to oil recovery. Pore enlarg... [more]

Emissions from the road transport sector are a major contributor to the climate change. Commonly used heavy vehicles powered by diesel engines emit toxic and harmful compounds that adversely affect the environment. For this reason, increasingly newer Euro emission standards are being introduced. Therefore, the emission performance of heavy-duty vehicles used in the transportation processes of diverse loads was investigated. The first research object was a set of vehicles equipped with a crane used for loading and unloading timber. The measurements were carried out in a specially designed research test reflecting the way the vehicle is used. It consisted of the drive to the loading site, the transport of timber to the destination and the processes of loading and unloading timber. The test route included driving on both unpaved forest roads and asphalt roads. The second research object was a set of vehicles used in long-distance road transport. The research route characterizing the traff... [more]

Biodiesel is a clean-burning, alternative diesel replacement fuel that may be used in existing diesel engines in either pure or blended form without or with modest modifications. In some countries, biodiesel is recommended as a potential alternative to diesel fuel since it is a renewable energy source that is environmentally benign. The main problems with the widespread commercialization of biodiesel are its high viscosity and its limited feedstock, due to which complete replacement of diesel fuel is not possible and the use of blends of biodiesel and petrodiesel are being used increasingly worldwide. The paper presents a behavioral study of the petro-based diesel, and their blend (B20, B40, B60, B80) with Pongamia and Jatropha biodiesel. The results reveal a considerable viscosity lowering due to the dilution effect of increasing diesel concentration in both the cases. In addition, improvements in oxidation stability in both cases have also been observed. The research shows that as th... [more]

The development of solid oxide fuel cells (SOFCs) for powering vehicles requires high power densities. The radial flows generated by the insert structures in SOFC fuel channels could improve the power density by facilitating the fuel to enter the porous anode for electrochemical reactions. In this paper, we developed a 2D axisymmetric numerical model to examine the influence of a convergent conical ring insert on the flow and mass transfer characteristics in a tubular SOFC. The mass transfer conductance of fuel was analyzed and proposed to quantify the performance of different insert designs. The effects of the radius and offset angle of the convergent conical ring insert were examined and analyzed. We demonstrate that increasing the insert radius could increase the fuel mass transfer conductance and effectively improve the net output power of the tubular SOFC by 12% while the offset angle of the inserts exhibits a negligible impact on the fuel mass transfer conductance. Increasing the... [more]

This study comprehensively examines the effects of the COVID-19 pandemic on energy consumption in the United States. The purpose of the study is to quantify the effects of lockdowns and pandemic disruptions on energy consumption trends in order to inform policymakers and utilities on how to prepare for such events in the future. The study focuses on 2020 data collected by the Federal government. The effects are quantified using descriptive statistics. State-wise and sector-wise data have been presented using plots and heat maps. Related metrics like COVID case data, GDP, emissions, and expenditures were also presented. The total energy consumption fell by 7.5% in 2020. Besides Alaska, every state saw a decrease in energy, with some as high as 26%. The residential sector had the most states that saw an increase in energy, stemming from lockdowns and working from home. Similarly, petroleum consumption saw a decrease of 11.4% as a result of a decrease in travel. Biomass-related renewable... [more]

Geothermal heat pump systems (GHP) are the spearhead of geothermal achievement and development, and one of the fastest growing applications of renewable energy technologies worldwide. When Swiss GHP activities started in the late 1970s, market introduction and penetration needed science-based proof of reliable, stable, long-term GHP operation. A special, extended project, realized in a field-laboratory setting, provided this proof. Detailed measurements, as well as numerical model simulations, proved the sustainable operation of the installed GHP system. The measurement setup, the recording of the various time series, and their interpretation are presented. Furthermore, basic perceptions were elaborated concerning geothermal resources behavior in production and regeneration. The Swiss GHP was developed from nothing. Early GHP installation costs halved within 20 years; GHP growth was nearly exponential from 1980 to 2020 (8.5% annually). Drilled borehole heat exchanger (BHE) meters are t... [more]

Solar concentrator collectors have the potential of meeting the medium- and high-temperature thermal energy demands of the world. A heat transfer fluid (HTF) is a vital component of a concentrating system to transfer and store thermal energy. This paper presents the design development of a solar paraboloidal dish concentrator (SPDC) and a study of selected HTFs using the storage receiver system of the concentrator. The locally designed SPDC (diameter 1.21 m and height 0.20 m) has features like light weight, effortless tracking, convenient transportation along with high optical and thermal performance. Three HTFs, silicone oil (SO), engine oil (EO) and ethylene glycol (EG), are selected based on their favorable properties for medium temperature (150−300 °C) applications. The characteristic parameters of HTFs, heating rate (Rh), instant thermal efficiency (ηith) and the overall heat loss coefficient (UL), are illustrated and determined experimentally. A new characteristic parameter, the... [more]

Balancing electricity demand and supply remains a significant challenge for the power systems in developing countries, such as Nigeria. In Nigeria, there is a shortage of adequate power supply, and demand-side management (DSM) plays a minor role in the power balancing mechanism with load shedding being widely used. The paper aims to review and compare various existing and emerging DSM strategies in developing countries. An extensive and systematic review was conducted to evaluate potential solutions using DSM to increase the overall energy efficiency in the Nigerian electricity market. This study found that, although the technical and economic potentials of DSM vary in developed countries, the uptakes of DSM have been severely hampered hence preventing the full exploitation and utilisation of the full potential of DSM. The initiatives of a DSM model in Nigeria and other developing countries can play a significant role in addressing demand and supply challenges but an upgrade of the ene... [more]