Portable Electric Power Research Articles

Design and experimental study of a 300 We class combustion-driven high frequency free-piston Stirling electric generator

Portable electric power generator with a power level of several hundred Watts plays an important role in outdoor activities, emergency relief and tactical power supply. As an external-combustion heat engine with outstanding heat source adaptability, free-piston Stirling generator (FPSG) owns attractive advantages of quietness, high thermal efficiency, and high reliability. This paper proposes a novel ultra-high frequency (UHF) FPSG-based portable power supply system driven by a diesel porous media evaporative combustor (PMEC). An experimental setup was designed and built based on the quasi-one-dimension thermoacoustic impedance matching of the FPSG and three-dimension thermal coupling of steady combustion and alternating flow between FPSG and combustor. The fundamental operating characteristics of the system were investigated in terms of combustion powers and electric loads. Preliminary experimental results show that a maximum output electric power of 350 We at a heating temperature of 875 K and a maximum fuel-to-electric efficiency of 11.98 % were obtained. Computational fluid dynamics (CFD) simulations were employed to delve into the intricate combustion and heat transfer processes, unveiling the formation of carbon deposits and confirming the efficacy of cyclone holes in reducing carbon deposition. This pioneering exploration of 130 Hz UHF and evaporative-combustion coupled heat transfer successfully showcases the feasibility of constructing a high-specific-power FPSG-based portable power system.

Multidisciplinary Design Methodology for Micro-Gas-Turbines—Part II: System Analysis and Optimization

Abstract Owing to their high specific energy capabilities, ultramicrogas turbines (UMGT) are a high-potential technology to provide portable electric power supply for applications with demand of less than 1 kW. UMGT conceptual design is challenged by small-scale effects augmenting interdisciplinary dependencies leading to highly coupled, nonlinear component interactions. This work provides a novel approach to conceptual UMGT design by combining reduced order component and system modeling with constrained multi-objective optimization. Hereby, Part I presents integrated design and performance modeling of compressor, turbine, combustor, and generator. In Part II, the heat engine and generator modules are merged into a system framework by establishing conceptual UMGT rotor geometry and engine design. Following bearing selection and lifetime assessment, experimentally validated reduced order models are developed for heat transfer and rotordynamic analysis. Using the elaborated framework, a constrained multi-objective system optimization of a 300 W engine is performed based on ten design parameters and comparing SiAlON and Inconel 718 as potential rotor materials available for additive manufacturing. Hereby, bearing lifetime, system efficiency, and specific power are maximized while meeting rotordynamic, structural, and thermal requirements. Evaluating the results, interdisciplinary effects are highlighted, and two optimum engine configurations are suggested.

Design and Fabrication of Electric Portable Tiller for Agricultural Purpose

In Indian Agriculture, Generally tractors or cultivator machines are commonly used for ploughing. Before this method farmers uses the traditional method this is time consuming and hardworking and costly. Despite the massive mechanization of agriculture in some regions of the nation, the majority of agricultural activities in the country's bigger areas are carried out by hand utilizing rudimentary and traditional equipment and implements such as a wooden plough sickle, and so on. This low-cost portable battery-powered electric power tiller machine is a one-stop contemporary solution to improve traditional farming practices by reducing human labor at a very cheap cost through the use of a motorized tilling mechanism. Because design and manufacture are the keysof engineering, mechanical engineering education requires real design and production. Using a clever portable design, the electric power tiller helps minimize the time and expense required in tilling, consequently enhancing agricultural output and efficiency

Review paper on Portable Electric Power Tiller Machine

Review paper on Portable Electric Power Tiller Machine

STATE AND PROBLEMS OF PRODUCTION AND HOUSEHOLD ELECTROTRAUMATISM IN UKRAINE

Technogenic development of society has caused widespread use in the system «man – production environment» and the system «man – household environment» of household electrical equipment, industrial electrical installations. Failure to comply with the regulated rules of electrical safety of electric current leads to electrical injuries. Designs of electrical installations, equipment, electrical protective measures are constantly being improved. But the level of electrical injuries in Ukraine and abroad tends to increase. This leads to social and economic losses as a result of economic costs in accidents, employee deaths, loss of working time and so on. The most objective indicator of injury is fatal. Thus, the level of fatal injuries at work per 1,000 workers in the developed world compared to the same rate in Ukraine in the UK is 10 times less, in Japan 7 times less, in the US 3 times less. This situation requires analysis and development of appropriate measures to reduce the level of electrical injuries. The analysis of statistical data revealed that the highest level of electrical injuries is observed in the following areas: - in agriculture; - service sector; - in public utilities; - in everyday life. At the same time, the tendency of its growth in the non-productive sphere and the household sector is expressed. So, at present in the general list of accidents from action of an electric current household electric injuries make the largest part – more than 46%. This is due to the insufficient level of education of the population on electrical safety, operation of electrical equipment in high-risk areas or in particularly dangerous by the degree of electric shock. At the same time, the level of domestic electrical injuries is higher in rural than in urban areas. It was also found that the greatest danger is posed by mobile and portable electrical installations, power tools and internal wiring. In addition, the housing of such electrical installations is often grounded through one of the cores of the power cable, which is unacceptable. The reasons for the high level of electrical injuries also include non-compliance with regulated organizational measures to ensure occupational safety and the so-called «human» factor. To improve the situation, it is necessary to intensify and increase the level of training of the population and employees on electrical safety, development and application of more modern switching electrical protection.

Non‐Noble Metal‐Based Catalysts Applied to Hydrogen Evolution from Hydrolysis of Boron Hydrides

Hydrogen energy is proposed as a promising energy replacement to resolve the current energy problems for sustaining the long‐term development of human society and eventually achieving the hydrogen economy. The evolution of hydrogen from the hydrolysis of boron hydrides is considered as one of the most secure and effective strategies. Seeking appropriate non‐noble metal‐based catalysts is the vital step that is needed to improve the sluggish kinetics of the hydrolysis process. Herein, the evaluation approaches related to the catalytic activities, kinetics, and stability are first summarized. Then, different non‐noble metal‐based catalysts based on single metals and their alloys, metal phosphides, borides, and oxides, and even single‐atom catalysts, are systematically discussed. The relationships among the synthesis methods, material structure, compositions, and catalytic activities are also critically reviewed. Finally, the challenges and perspectives for future non‐noble metal‐based catalysts for hydrolysis of boron hydrides are included to aid in the development of sustainable and clean hydrogen energy. More importantly, the current research is mainly focused on the fundamental research, whereas the report on the practical application for the catalyzed hydrolysis of boron hydrides is less. Developing portable hydrogen generators as hydrogen sources for portable electric power is a potential strategy.

Omnidirectional Current Enhancement From Laminated Moth-Eye Textured Polymer Packaging for Large-Area, Flexible III-V Solar Modules

Epitaxial lift-off (ELO) processes have allowed for cheaper development of mechanically flexible, ultra-thin, and high-efficiency III-V solar cells. ELO solar cells are natural candidates for applications where solar cells must conform to curved surfaces and provide high efficiency and high specific power generation (W/kg). Such examples include power generation for unmanned aerial vehicles, electric vehicles, and portable electrical power. However, when considering these mobile solar applications, large variations in angle of incidence (AOI) that inevitably occur can greatly decrease overall system efficiency due to significant Fresnel reflections. In this article, we demonstrate the integration of moth-eye antireflection nanostructures on the polymer packaging layer of ELO solar cell arrays using a low-cost, colloidal self-assembly process. The moth-eye structures mitigate Fresnel reflections and increase photocurrent generation over all measured angles of incidence relative to ELO solar cell arrays with traditional untextured polymer packaging. The nanostructures survive a commercial lamination procedure, an important criterion that must be met to ensure the feasibility of integration into commercial processing. Outdoor solar characterization measurements are performed and, under direct optical illumination, moth-eye textured solar cell arrays show a maximum I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> enhancement of ~58% at 79° AOI relative to traditional untextured polymer packaged solar cell arrays, and when exposed to both direct and diffuse optical illumination a maximum I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> enhancement of ~23% at 79° AOI is observed.

Combustion Power in your Pocket: A Case for Portable Pyroelectric Energy Conversion

The pyroelectric effect has been rarely considered as a pathway toward portable electric power. Now, in a study published in Cell Reports Physical Science, Hanrahan et al. show chip-based pyroelectric combustion that has the potential to supersede Li-ion battery technology in terms of energy density and device lifetime.

High-Performance Magnesium-Carbon Nanofiber Hygroelectric Generator Based on Interface-Mediation-Enhanced Capacitive Discharging Effect.

This study reports the concept of a water/moisture-induced hygroelectric generator based on the direct contact between magnesium (Mg) alloy and oxidized carbon nanofibers (CNFs). This device generates an open-circuit voltage up to 2.65 V within only 10 ms when the unit is placed in contact with liquid water, which is higher than the reduction potential of magnesium. The average peak short-circuit current density is ∼6 mA/cm2, which is among the highest values yet reported for water-induced electricity generators. Our results indicate that galvanic corrosion occurs at the interface between the CNF and Mg electrode, but the device can still generate electricity because of the high contact resistance caused by the work function difference between Mg and CNF and the surface oxidation. The oxidized CNF is shown to absorb water/moisture and get reduced, leading to a capacitive discharging effect to provide enhanced signal amplitude and sensitivity. These devices are found to be highly sensitive to small quantities of water, and their high output voltage and current make them useful for the detection of water vapor in the human breath as well as changes in ambient humidity. The Mg/CNF systems thus provide a new technology for use in the fabrication of self-powered water/moisture sensors and the development of portable electric power generators.

A “Press and Go” Thin Biofuel Cell Patch for Power Generation

Biofuel cells are devices that generate portable electrical power, typically from glucose, alcohols or related biofuels, by using enzymatic anodes and cathodes. We report on the performance of membrane- and mediator-free enzymatic glucose biofuel cells (BFCs) fabricated in a sandwiched, patch geometry with carbon nanotube nanopaper bio-electrodes prepared using a compression technique to immobilize the enzymes. A gel electrolyte comprised of agar mixed with glucose is sandwiched between the two bio-electrodes to form a patch. Power densities up to 111.90 μW/cm2 at a current density of 334.50 μA/cm2 at a voltage of 0.335 V were obtained for a typical single cell BFC of this design. The sandwich BFC also showed good stability with a half-life of about 1.5 days under continuous operation. The relatively high power density for this new design is attributed to the compression-induced immobilization of the enzymes by the nanotubes as indicated by scanning electron microscope images. This compression-induced immobilization of enzymes provides improved direct electron transfer at the carbon nanotube electrodes.

Health Risk Communication and The Hazards of Portable Electricity Generator Use: A Study of Awareness and Knowledge of Carbon Monoxide Poisoning Among Resident Nigerian Public University Students

The overall objective of the study was to determine Nigerian university students’ awareness and exposure to label warnings on portable electric power generators; their level of comprehension of these label warnings; knowledge of carbon monoxide poisoning; and, preventive measures taken to avoid carbon monoxide poisoning. The survey research method was used for this study. Data was collected in Southeastern Nigeria among undergraduate students, by administering questionnaire to a sample of 400 students from four universities. The study found a high level of exposure to label warnings on house hold products but a minimal exposure to label warnings on portable electric power generating sets among these students.Variables like placement of the warnings, font sizes and religious inclination hindered exposure to the warnings and compliance to the warning message; awareness of carbon monoxide information was high and a greater number among the respondents got informed either through their families and friends or read about it; a relatively lower number got informed through the media. While these university students were aware of carbon monoxide poisoning, they were not properly informed of the different symptoms that are associated with the gas and the preventive measures that could prevent carbon monoxide poisoning. This suggests that carbon monoxide poisoning is not being taken seriously as a health hazard among people susceptible to poisoning. Key words : Health risk communication, portable electricity generator use, carbon monoxide poisoning, label warnings DOI : 10.7176/JEES/9-6-14 Publication date :June 30 th 2019

Portable and Inventive Electrical Power Supply

Portable and Inventive Electrical Power Supply

Knee-braced energy harvester: Reclaim energy and assist walking

Abstract In recent years, the increasing power requirement of wearable electronics and exoskeletons has made it very necessary to develop new methods of providing portable electrical power sources. In this paper, we present a knee-braced energy harvester to reclaim human kinetic energy and to assist human walking by redistributing the torque of the knee joint. The energy harvester is mounted at the knee and uses a spiral spring and generator to form a spring-damping mechanism. The spring-damping mechanism can partly replace the function of knee joint muscles during walking by reducing knee biomechanical torque and power; thus, the total metabolic energy used for walking can be reduced while electricity is generated at the same time. A prototype harvester was built to test the performance; the experimental results show that at the walking velocity of 4.2 km/h, the energy harvester can reduce the metabolic cost of walking by 3.6%, with a spring stiffness of 2 N·m/rad and an electrical damping coefficient of 0.5, and an average electrical power of 2.4 W is generated within the harvesting process.

Re-assessment of station blackout accident in VVER-1000 NPP with additional measures following Fukushima accident using Relap/Mod3.2

The Fukushima accident indicated that the safety systems of nuclear power plants should be re-assessed against site-specific extreme natural hazards using additional BDBA management equipment and organizational measures. The occurrence of loss of power supply (SBO) accident in VVER-1000 NPP, which is the most contributor to the total core damage frequency, is the focus of this study. The SBO accident analysis of the reference plant with and without operator actions are investigated by Relap5 code to identify the characteristics of additional measures, available times for operator actions (critical time points) as well as scenarios to manage the accident consequences. The additional BDBA management equipment includes robust and reliable portable additional electrical power backup sources and water supplies into the primary and secondary cooling system to remove the residual heat of the core. The main purpose of this study is an evaluation of efficiency and sufficiency of additional equipment and organizational measures at NPP site based on deterministic safety analysis during SBO accident. This analysis is also expected to prepare a useful guideline for the SBO management in VVER-1000/V-446 NPP. A validated Relap5 model of VVER-1000 is employed to implement the proposed SBO accident scenarios consisting of residual heat removal through primary and secondary cooling systems as well as additional measures to mitigate this accident. The main thermal-hydraulic parameters of NPP in response to SBO accident are compared with specified acceptance criteria. The deterministic safety analysis demonstrates the provided accident scenarios with specified additional BDBA management equipment ensures the long-term reliable cooling of the reactor core under loss of power supply condition. The result also illustrates that a high degree of confidence in the robustness of the VVER-1000 NPP could be achieved against SBO accident with the inclusion of additional measures.

Covalently functionalized graphene as a supercapacitor electrode material

The need for efficient, lightweight, flexible, stable and eco-friendly portable electric power delivery has placed research on supercapacitor electrode materials at the forefront of endeavors to provide future energy storage. Graphene-based materials and composites have been shown to be promising materials toward this goal. In this review, we describe recent progress in the development of electrode materials by the covalent functionalization of graphene. Covalent graphene derivatives are an emerging and potentially large class of very efficient materials, whose structural and physicochemical properties can be tailored according to the specific needs of capacitive charge storage. They also open doors to new composites and hybrids, which may further advance the field-encoding properties and other features as yet unexplored.

All-in-one portable electric power plant using proton exchange membrane fuel cells for mobile applications

A portable electric power plant is developed using a NaBH4 (sodium borohydride)-based proton exchange membrane fuel cell stack. The power plant consists of a NaBH4-based hydrogen generator, a fuel cell stack, a DC-DC converter, a micro-processed controller and a data monitoring device. The hydrogen generator can produce 5.9 L/min pure hydrogen gas using catalytic hydrolysis of 20 wt% NaBH4 to feed a 500-W scale fuel cell stack. Thus, the Co/γ-Al2O3 and Co-P/Ni foam catalysts in the hydrogen generator play significant roles in promoting hydrogen production rates that are as fast as necessary by enhancing the slow response that is intrinsic to using only Co-P/Ni foam catalysts. Moreover, different hydrogen production rates can easily be achieved during the operation by controlling NaBH4 solution rates using a fuel pump so that the hydrogen storage efficiency can be improved by supplying required hydrogen gas in accordance with load demands. The specific energy density of the electric power plant was measured 211 Wh/kg. Therefore, the power plant described here can be a power source for mobile applications, such as cars and UAVs, as well as a stationary power supplier when electric energy is required.

In-depth understanding of interfacial crystallization via Flash DSC and enhanced energy storage density in ferroelectric P(VDF-CTFE)/Au NRs nanocomposites for capacitor application.

High-capacity or high-power-density capacitors are being actively investigated for portable electronics, electric vehicles, and electric power systems. We describe the filler system in dielectric nanocomposites with a small loading of Au nanorods [NRs] to elucidate the mechanism of interfacial crystallization behavior including the crystallization kinetics, and crystalline morphology and structure, and to investigate the intrinsic causes for concurrent great improvements in the dielectric constant and energy density in the nanocomposite system. Remarkly, at high crystallization temperature, the addition of Au NRs, which are used as heterogeneous nucleators, can reduce the nucleation barrier, resulting in accelerating the crystallization rate. However, the crystallization rate slows down at low temperatures because the addition of Au NRs limited the mobility of poly(vinylidene fluoride-chlorotrifluoroethylene) [P(VDF-CTFE)] chains, and thus enhanced the diffusion barrier. Furthermore, the addition of NRs has a huge impact on the crystalline morphology and structure which changes from large paraelectric α-phase spherulites with TGTG' conformations into minor ferroelectric γ-phase spherulites with T3GT3G' conformations, and also produces more exogenous interfaces between the lamellar crystals and amorphous regions, resulting in a higher dielectric constant and higher electric energy density in P(VDF-CTFE)/Au NRs nanocomposites. Our approach provides a facile and straightforward way to design or understand PVDF-based polymers for their practical applications in high-energy-density capacitors.

Development and investigation of a non-catalytic self-aspirating meso-scale premixed burner integrated thermoelectric power generator

Portable electrical power generation using hydrocarbons presents significant potential owing to their higher power densities and negative environmental factors associated with chemical cell batteries. Small scale combustors have been widely developed and tested for power generation purposes, employing thermoelectrics and thermo-photovoltaic conversion of combustion heat into electricity. This experimental study is concerned with development and investigation of a novel non-catalytic meso-scale self-aspirating premixed burner with integrated thermoelectric generator which can be used in remote places to generate electricity for a continuous period of one month. Flame stabilisation has been one of the main issues in small scale combustion systems due to higher surface to volume ratio associated with small size of the combustor. Previous research has shown that catalytic combustion is one way of improving flame stabilisation, however employing a catalyst into the system increases the manufacturing cost which can be a significant downside. This research work studies flame stabilisation mechanisms in meso-scale burner which mainly focuses on backward facing step and secondary air addition into the combustion chamber. The first phase of the research was involved development of the burner which included optimisation of the design to achieve a stable enclosed premixed flame as per the design and operational requirements. The second phase of the research focused on the integration of the burner with thermoelectric power generators. This involved investigation of various configurations to optimise the electrical power output when limited amount of heat is available. The relationship between ambient temperature and thermoelectric power generation using an environmentally controlled chamber has also been presented in this experimental study.

Crosslinked P(VDF-CTFE)/PS-COOH nanocomposites for high-energy-density capacitor application

High-capacity or high-power-density capacitors are being actively investigated for portable electronics, electric vehicles, and electric power systems. The dielectric nanocomposite with a small loading of carboxylic polystyrene (PS-COOH) nanoparticles in poly(vinylidene fluoride-chlorotrifluoroethylene) [P(VDF-CTFE)] matrix, followed by chemical crosslinking has been described. Combination of these two methods significantly improved the capacity of electric energy storage at low electric field. Specially, the nanocomposite with 2 wt % nanoparticles and 15 wt % crosslinking agent achieved a dielectric constant of 17.2 and a discharged energy density of 17.5 J/cm3 (4.9 Wh/L) at an electric field as high as 324 MV/m, while corresponding values for pristine P(VDF-CTFE) are 9.6 and 13.3 J/cm3 (3.7 Wh/L), respectively. Fundamental physics underlying the enhancement in the performance of the nanocomposites with respect to P(VDF-CTFE) is illustrated by solid-state 19F nuclear magnetic resonance of direct excitation or 19F{1H} cross polarization. It revealed different dynamics behavior between crystalline/amorphous regions, and PS-COOH nanoparticles favored the formation of polar γ-form crystals. Small-angle X-ray scattering studies revealed the contribution of the interface to the extraordinary storage of electric energies in the nanocomposites. This approach provided a facile and straightforward way to design or understand PVDF-based polymers for their practical applications in high-energy-density capacitors. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1160–1169

Noise from Portable Electric Power Generators in an Institutional Setting: A Neglected Risk Factor

An ideal educational setting should be serene and conducive for both learning and working. However, due to the erratic power supply in Nigeria coupled with increase in number of commercial outfits, there has been an upsurge in the proliferation of portable generators at institutional settings. Studies conducted on noise from portable generators and its effects on human health in institutional environment are sparse. Noise levels from exposure to portable generators and its perceived attendant effects was assessed in this study. Oladele Ajose building (OAB) was purposively selected for this pilot study based on the frequency of generator use and level of commercial activities. A semi structured questionnaire was used to elicit information from staff and students. Noise levels in decibels (dB) was measured in six selected location for eight weeks in the indoor and outdoor environment of the building, using a calibrated AEMC sound meter. Results were compared with WHO guideline limits. Mean noise level in the indoor and outdoor environment was 60.26±8.45dB and 58.15±4.53dB respectively. Reported health problems in the last six months prior the study include ear pains (68%), headache (46%), tiredness (60%) and tinnitus (34%). Occupants of OAB are exposed to noise from electric generator at levels exceeding WHO limit. There is a need to find an alternative way to power generation in institutional settings because of the threat noise from generators poses to the serene and conducive learning environment.