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Electrical Power (electrical + power)
Selected AbstractsBiofuel Cells: Harnessing Biomass or Body Fluids for the Generation of Electrical PowerFUEL CELLS, Issue 1 2009Itamar Willner Professor No abstract is available for this article. [source] Simulation of Direct-Current Microdischarges for Application in Electro-Thermal Class of Small Satellite Propulsion DevicesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2007P. S. Kothnur Abstract Microdischarges are miniature non-equilibrium plasma discharges with characteristic dimensions of ,10's,100's ,m and relatively high operating pressures of ,10's,100's Torr. Microdischarges possess several unique properties that have been exploited in a number of new applications. We have recently proposed amicrodischargebased electro-thermal class of microthrusters for small satellite propulsion. These devices utilize intense gas heating in microdischarges to preheat a propellant gas stream before it is expanded in a micronozzle to produce thrust; thereby improving specific impulse of the device over a conventional cold gas microthruster. This paper addresses direct-current microdischarge phenomena in a flowing gas stream. A two-dimensional, selfconsistent, fluid model of a helium microdischarge in a bulk gas flow is developed. For relatively high current/power levels considered in this study, the microdischarge operates in an abnormal glow mode with positive differential resistivity. Increasing discharge pressures for fixed power and bulk flow rates results in a decrease in charged species densities and the electron and gas temperatures. Also the discharge becomes increasingly constricted with increasing pressures, resulting in a more normal glow mode-like operation. Increasing bulk flow rates results in exactly the same trends as increasing pressures. For given input power and pressure, there exists an optimum flow rate for which the average outlet gas temperature from the discharge is a maximum. An increase in input electrical power results in an almost linear increase in the gas temperatures; this property of microdischarges is the key feature that is exploited in our microdischarge-based thruster concept. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Load-flow conditions for hvdc transmission in synchronous networksEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2000J. Warnking The basic purpose for HVDC (high-voltage direct current) transmission is to transmit a determined value of electrical power from one electrical node to another. If there is an AC system in parallel to an HVDC transmission, the load flow via this parallel AC system can be controlled directly. Since HVDC systems offer possibilities to perform fast load-flow control, they can also be used for improving stability. In this paper load-flow calculations of a simplified network are presented. First a comparison between HVDC transmission operating in asynchronous resp. synchronous networks is shown. Synchronous network means that the HVDC transmission works in parallel to an AC system at the same voltage level. It is shown how voltage at the point of installation and how the load angle are influenced due to the synchronous operation. A special regard is drawn to the losses of the transmission. Conditions for minimum total losses are presented. Informer calculations loads are involved. It is shown how they influence the minimum total losses. [source] Hydrogen Production via Autothermal Reforming of Diesel FuelFUEL CELLS, Issue 3 2004J. Pasel Abstract Hydrogen, for the operation of a polymer electrolyte fuel cell, can be produced by means of autothermal reforming of liquid hydrocarbons. Experiments, especially with ATR 4, which produces a molar hydrogen stream equivalent to an electrical power in the fuel cell of 3,kW, showed that the process should be preferably run in the temperature range between 700,° and 850,°. This ensures complete hydrocarbon conversion and avoids the formation of considerable amounts of methane and organic compounds in the product water. Experiments with commercial diesel showed promising results but insufficient long-term stability. Experiments concerning the ignition of the catalytic reaction inside the reformer proved that within 60,s after the addition of water and hydrocarbons the reformer reached 95% of its maximum molar hydrogen flow. Measurements, with respect to reformer start-up, showed that it takes approximately 7,min. to heat up the monolith to a temperature of 340,° using an external heating device. Modelling is performed, aimed at the modification of the mixing chamber of ATR Type 5, which will help to amend the homogeneous blending of diesel fuel with air and water in the mixing chamber. [source] Complete Characterization of Thermoelectric Materials by a Combined van der Pauw ApproachADVANCED MATERIALS, Issue 38 2010Johannes de Boor Thermoelectric materials can convert waste heat directly into electrical power and represent an important contribution to lessen energy scarcity. Here we present a novel, simple and inexpensive approach for a complete thermoelectric characterization, by which all relevant quantities, like the electrical conductivity, the thermal conductivity, the Seebeck coefficient, and the figure of merit, can be determined directly. [source] Thermoeconomic modeling of micro-CHP (micro-cooling, heating, and power) for small commercial applicationsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2008Alan Moran Abstract The increasing demand for electrical power as well as energy for heating and cooling of residences and small commercial buildings is a growing worldwide concern. Micro-cooling, heating, and power (micro-CHP), typically designated as less than 30,kW electric, is decentralized electricity generation coupled with thermally activated components for residential and small commercial applications. The number of combinations of components and parameters in a micro-CHP system is too many to be designed through experimental work alone. Therefore, theoretical models for different micro-CHP components and complete micro-CHP systems are needed to facilitate the design of these systems and to study their performance. This paper presents a model for micro-CHP systems for residential and small commercial applications. Some of the results that can be obtained using the developed model include the cost per month of operation of using micro-CHP versus conventional technologies, the amount of fuel per month required to run micro-CHP systems, the overall efficiency of micro-CHP systems, etc. A case study is used to demonstrate differences in the system performances of micro-CHP systems driven by a natural gas internal combustion engine and a diesel engine. Some of the results show that both systems have similar performance and that system total efficiencies in cooler months of up to 80% could be obtained. Also, modeling results show that there is a limit in fuel price that economically prevents the use of CHP systems, which is $11 MBTU,1 for this specific case. Copyright © 2008 John Wiley & Sons, Ltd. [source] Parametric study of chemical looping combustion for tri-generation of hydrogen, heat, and electrical power with CO2 captureINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2005J. Wolf Abstract In this article, a novel cycle configuration has been studied, termed the extended chemical looping combustion integrated in a steam-injected gas turbine cycle. The products of this system are hydrogen, heat, and electrical power. Furthermore, the system inherently separates the CO2 and hydrogen that is produced during the combustion. The core process is an extended chemical looping combustion (exCLC) process which is based on classical chemical looping combustion (CLC). In classical CLC, a solid oxygen carrier circulates between two fluidized bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In exCLC the oxygen carrier circulates along with a carbon carrier between three fluidized bed reactors, one to oxidize the oxygen carrier, one to produces and separate the hydrogen, and one to regenerate the carbon carrier. The impacts of process parameters, such as flowrates and temperatures have been studied on the efficiencies of producing electrical power, hydrogen, and district heating and on the degree of capturing CO2. The result shows that this process has the potential to achieve a thermal efficiency of 54% while 96% of the CO2 is captured and compressed to 110 bar. Copyright © 2005 John Wiley & Sons, Ltd. [source] Numerical and analytical calculations of the temperature and flow field in the upwind power plantINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2004Henry Pastohr Abstract The upwind power plant is an interesting system to generate electrical power from free solar energy. The authors have carried out an analysis to improve the description of the operation mode and efficiency. The pressure drop at the turbine and the mass flow rate have a decisive influence on the efficiency. This can be determined only by coupling of all parts of an upwind power plant. In this study the parts ground, collector, chimney and turbine are modelled together numerically. The basis for all sections is the numerical CFD programme FLUENT. This programme solves the basic equations of the thermal fluid dynamics. Model development and parameter studies particularly arise with this tool. Additional to the calculations using FLUENT a simple model is developed for comparison purposes and parameter studies. The numerical results with FLUENT compare well with the results given by the simple model, therefore, we can use the simple model for parameter studies. The basis for the geometry is the prototype Manzanares. Copyright © 2004 John Wiley & Sons, Ltd. [source] Initial evaluation of a field-friendly extraction procedure for the enzymatic assay of cassava cyanogensINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2007Gerard M. O'Brien Summary A novel ,field friendly' extraction procedure has been developed for the enzymatic colorimetric determination of cyanogenic potential (CNP) in fresh cassava root parenchyma. The novel procedure does not require electrical power or vacuum, and employs inexpensive lightweight equipment, making it suitable for remote field sites. Testing of the procedure involved ten fresh roots (24,80 mg kg,1 total CNP, as HCN, fresh basis). From the parenchyma of each root, one extract was made using the novel procedure, and a ,control' extract was made using a traditional laboratory-based procedure. Total CNP assay of the extracts indicated strong (y = mx) or very strong (y = mx + c) correlation of results obtained using the two procedures, while a very strong correlation (y = mx) was obtained for free HCN. Based on this preliminary evidence, the novel procedure is satisfactory at least for total CNP assay of fresh low-CNP cassava roots. [source] Electrothermal model of optocoupler for SPICEINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4 2009Krzysztof Górecki Abstract In the paper a new electrothermal model of the optocoupler for SPICE is proposed. The model is based on electrical models of the LED and the bipolar phototransistor with their parameters dependent on temperature, their thermal models including both the self-heating phenomenon and the mutual thermal interactions between the LED and the phototransistor, and the dependences describing electrical power dissipated in these components. The final form of the electrothermal model of the optocoupler elaborated by the authors, dedicated to the d.c. and a.c. computations, was implemented in SPICE. The usefulness of the new model was experimentally verified for the optocoupler 4N25. Copyright © 2008 John Wiley & Sons, Ltd. [source] Operating and scale-up factors for the electrolytic removal of algae from eutrophied lakewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Catalino G Alfafara Abstract Electrolytic removal of algae was conducted in batch and continuous reactors to investigate operating factors affecting removal efficiency and to explore engineering relationships which could be useful for operation and scale-up. The system integrated both electro-flocculation and electro-flotation mechanisms by using polyvalent metal anodes and inert metal cathodes. Batch reactor studies confirmed that high electrical input power or higher electrical current achieved higher and faster removal efficiencies. Natural liquid circulation was observed during electrolytic operation and increased with higher electrical power. However, a small degree of external mixing may be useful at lower electrical power input. Electro-flotation alone could not achieve complete algae removal (maximum efficiency 40,50%), and showed the importance of algal floc formation for the complete removal of algae. In continuous electrolysis experiments, the ratio of the volumetric current intensity (amperes,dm,3) and the chlorophyll a loading (mg,dm,3,h,1) was found to be a useful operating and scale-up factor to balance high algal removal efficiency with minimum release of excess aluminum. This ratio was eventually found to be just the charge dose or the amount of coulombs required to remove a unit mass of chlorophyll a. The optimum charge dose was determined and used to relate the operating current and electrolysis time of a continuous process. © 2002 Society of Chemical Industry [source] Optimization of a Composite Working Electrode for a New Family of Electrochemical Cell for NO DecompositionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2003Kazuyuki Matsuda The electrochemical properties of a composite (NiO)x,(yttria-stabilized zirconia (YSZ))1,x working electrode for a new type of electrochemical cell for NO decomposition in the presence of excess oxygen are investigated. It is shown that the dependence of the NO conversion on the value of the current passed through the electrochemical cell with a nanoporous (NiO)x,(YSZ)1,x working electrode is linear and that the value of current efficiency depends on the NO and O2 gas concentrations only (,= [NO] /([NO] + 2[O2]). The optimum NiO addition (35% by volume) to the YSZ resulted in a decrease of the cell operating voltage and, as a result, in a decrease in the electrical power required for NO decomposition. The observed high performance of the composite working electrode at this composition is consistent with the effective medium percolation theory, which predicts the ambipolar transport behavior of the composite mixed ionic,electronic (YSZ,NiO) conductors as a function of the volume fraction of each of the randomly distributed constituent phases. [source] Acceptability, feasibility and affordability of infant feeding options for HIV-infected women: a qualitative study in south-west NigeriaMATERNAL & CHILD NUTRITION, Issue 3 2006Titilayo C. Abiona Abstract The objective of this study was to explore the acceptability, feasibility, affordability, safety and sustainability of replacement feeding options for HIV-infected mothers in Ile-Ife, in south-west Nigeria. Six focus group discussions were conducted with a purposive sample of mothers, fathers and grandmothers. The HIV status of all participants was unknown to investigators. All text data were analysed using the Text-based Beta Software program. With regard to the acceptability of replacement feeds, respondents perceived the stigma associated with not breastfeeding to be an important consideration. In this community, breastfeeding is the norm , even though it is not necessarily exclusive. For infected mothers who choose to breastfeed exclusively and then to wean their infants before 6 months of age, respondents did not anticipate early cessation of breastfeeding to be problematic. Respondents noted that acceptable replacement foods included infant formula, soy milk and cow's milk. Barriers to replacement feeding that were mentioned included: the high costs of replacement foods and fuel for cooking; an unreliable supply of electrical power; poor access to safe water; and poor access to storage facilities. The research confirms the difficulty of replacement feeding for HIV-infected mothers in sub-Saharan Africa. The results also provide the basis for new issues and hypothesis for future research in other communities with similar socio-cultural and economic characteristics. [source] Shipboard Fluid System Diagnostic Indicators Using Non-Intrusive Load MonitoringNAVAL ENGINEERS JOURNAL, Issue 2 2007GREGORY R. MITCHELL Field studies have demonstrated that it is possible to evaluate the state of many shipboard systems by analyzing the electrical power that is drawn by electromechanical actuators. This paper demonstrates how a device known as a non-intrusive load monitor (NILM) uses only electrical power data to detect several critical faults in shipboard fluid systems. Using the example of reverse-osmosis units installed aboard the US Coast Guard's Medium Endurance Cutters, it is shown that the NILM can provide ship's force with a highly reliable real-time system monitoring capability. [source] A Passive Magnetically and Hydrodynamically Suspended Rotary Blood PumpARTIFICIAL ORGANS, Issue 3 2009Martin Stoiber Abstract A combined hydrodynamic,magnetic bearing allows the design of rotary blood pumps that are not encumbered with mechanical bearings and magnets requiring sensors or electrical power. However, such pumps have so far needed very small and accurately manufactured gaps between rotor and housing to assure effective hydromagnetic bearing behavior. In order to use this concept in disposable pump heads, a design that allows larger rotor-housing gaps, and thus larger manufacturing tolerances, is needed. A pump with passive magnetic bearings and a gap between rotor and housing in the range of 0.5 mm was designed. Numerical simulations were performed to optimize the rotor geometry at low levels of shear stress. An experimental test stand was used to find a range of speeds and gap settings that resulted in low levels of vibration and useful pressure,flow relationships. Three different rotor geometries were tested using a viscosity-adjusted test fluid. Blood damage tests were conducted within the desirable range of speeds and gap settings. In this study stable pump performance was demonstrated at total gap widths between 0.3 and 0.7 mm at flows of 0,10 L/min, with afterloads up to 230 mm Hg. Best performance was achieved with rotors sliding on a fluid pillow between the rotor and the outer housing at a gap distance of 50 to 250 µm. The inner gap distance, between the rotor and the inner housing, could be as great as 500 µm. Hemolysis tests on the prototype within the chosen operating range showed lower values (NIH = 0.0029 ± 0.0012 g/100 L) than the Biomedicus BP-80 pump (NIH = 0.0033 ± 0.0011 g/100 L). In conclusion, it is possible to build rotary blood pumps with passive hydromagnetic bearings that have large gaps between their rotors and housings. Rotor behavior is sensitive to the position of the permanent magnetic drive unit. To minimize vibration and blood damage, the fluid gaps and the rotational speed have to be adjusted according to the desired operating point of the pump. Further study is needed to optimize the magnetic drive unit and to ascertain its ability to withstand inertial loads imposed by sudden movements and external shock. [source] A Study on an Energy Supply Method for a Transcutaneous Energy Transmission SystemARTIFICIAL ORGANS, Issue 1 2003Toshinaga Ozeki Abstract: This study proposes a new type of a transcutaneous energy transmission system (TETS) that can supply electrical power for an implanted device without an external battery. In this system, the power is supplied from the floor to the shoes of the patients through coils that are set beneath the floor and the bottom of the shoes. If the patients wear the special shoes, they will be able to move freely on the specially designed floor without an external battery. Direct current (DC)-DC power efficiency was measured in the experiments, and the results showed that it varies with relative positions between the shoe and the floor coils. The results suggested that three-layered floor coils would enable the system to meet the demand for providing the required power anywhere on the floor without intermission. DC-DC power efficiency could be kept over 60% under the practical condition. It can then be concluded that the proposed system has a potential to provide better quality of life for the patients using a TETS. [source] Technical characterization of an ultrasound source for noninvasive thermoablation by high-intensity focused ultrasoundBJU INTERNATIONAL, Issue 3 2002K.U. Köhrmann Objective,To develop a generator for high-intensity focused ultrasound (HIFU, a method of delivering ultrasonic energy with resultant heat and tissue destruction to a tight focus at a selected depth within the body), designed for extracorporeal coupling to allow various parenchymal organs to be treated. Material and methods,The ultrasound generated by a cylindrical piezo-ceramic element is focused at a depth of 10 cm using a parabolic reflector with a diameter of 10 cm. A diagnostic B-mode ultrasonographic transducer is integrated into the source to allow the focus to be located in the target area. The field distribution of the sound pressure was measured in degassed water using a needle hydrophone. An ultrasound-force balance was used to determine the acoustic power. These measurements allowed the spatially averaged sound intensity to be calculated. The morphology and extent of tissue necrosis induced by HIFU was examined on an ex-vivo kidney model. Results,The two-dimensional field distribution resulted in an approximately ellipsoidal focus of 32×4 mm (, 6 dB). The spatially maximum averaged sound intensity was 8591 W/cm2 at an electrical power of 400 W. The lesion caused to the ex-vivo kidney at this maximum generator power with a pulse duration of 2 s was a clearly delineated ellipsoidal coagulation necrosis up to 8.8×2.3 mm (length×width) and with central liquefied necrosis of 7.9×1.9 mm. Conclusion,This newly developed ultrasound generator with a focal length of 10 cm can induce clear necrosis in parenchymal tissue. Because of its specific configuration and the available power range of the ultrasound generator, there is potential for therapeutic noninvasive ablation of tissue deep within a patient's body. [source] | |||||||||||||||||||