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Electrical Energy (electrical + energy)

Distribution by Scientific Domains

Chemistry	35%
Polymers and Materials Science	28%

Selected Abstracts

Engineered Pyranose 2-Oxidase: Efficiently Turning Sugars into Electrical Energy

ELECTROANALYSIS, Issue 7-8 2010
Oliver Spadiut
Abstract Due to the recent interest in enzymatic biofuel cells (BFCs), sugar oxidizing enzymes other than the commonly used glucose oxidase are gaining more importance as possible bioelements of implantable microscale-devices, which can, for example, be used in biosensors and pacemakers. In this study we used rational and semi-rational protein design to improve the catalytic activity of the enzyme pyranose 2-oxidase (P2Ox) with its alternative soluble electron acceptors 1,4-benzoquinone and ferricenium ion, which can serve as electron mediators, to possibly boost the power output of enzymatic BFCs. Using a screening assay based on 96-well plates, we identified the variant H450G, which showed lower KM and higher kcat values for both 1,4-benzoquinone and ferricenium ion compared to the wild-type enzyme, when either D -glucose or D -galactose were used as saturating electron donors. Besides this variant, we analyzed the variants V546C and T169G/V546C for their possible application in enzymatic BFCs. The results obtained in homogeneous solution were compared with those obtained when P2Ox was immobilized on the surface of graphite electrodes and either "wired" to an osmium redox polymer or using soluble 1,4-benzoquinone as mediator. According to the spectrophotometrically determined kinetic constants, the possible energy output, measured in flow injection analysis experiments with these variants, increased up to 4-fold compared to systems employing the wild-type enzyme. [source]

Algorithmic challenges and current problems in market coupling regimes

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2009
Bernd Tersteegen
Abstract Increasing cross-border trade at European borders has lead to the necessity of an efficient allocation of scarce cross-border capacities. Explicit auctions used to be the commonly applied auction method in the past at most borders, but due to the separation of the trade of electrical energy and the allocation of cross-border capacity, market inefficiencies arise. As a consequence, a trend toward a market coupling, which combines the trade of electrical energy with the allocation of cross-border capacity, can be observed across Europe. The most convincing approach to solve the complex optimization task associated with market couplings solves the problem by a maximization of the system-wide welfare based on a closed-form optimization. Practical experience shows that problems remain with such an approach. This paper thoroughly analyzes problems that may occur in market coupling regimes with a closed-form optimization. In this paper an extension of formerly presented formulations of the optimization problem is presented, which avoids the described problems. The extended formulation still assures practically feasible calculation times of far less than 10 minutes even for systems with up to 12 market areas. Further, a fair and transparent approach to determine feasible market clearing prices not neglecting the time and market coupling relationship between prices is shown in this paper and it is demonstrated that this approach does not lead to practically infeasible calculation times. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Volume Organization of Polymer and Hybrid Solar Cells as Revealed by Electron Tomography

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010
Svetlana S. van Bavel
Abstract Polymer and hybrid solar cells have the potential to become the leading technology of the 21st century in conversion of sun light to electrical energy because their ease processing from solution producing printable devices in a roll-to-roll fashion with high speed and low cost. The performance of such devices critically depends on the nanoscale organization of the photoactive layer, which is composed of at least two functional materials: the electron donor and the electron acceptor forming a so-called bulk heterojunction; however, control of its volume morphology still is a challenge. In this context, advanced analytical tools are required that are able to provide information on the local volume morphology of the photoactive layer with nanometer resolution. In this report electron tomography is introduced as the technique able to explore the 3D morphology of polymer and hybrid solar cells and the first results achieved are critically discussed. [source]

A Promising Approach to Enhanced Thermoelectric Properties Using Carbon Nanotube Networks

ADVANCED MATERIALS, Issue 4 2010
Chuizhou Meng
Enhanced Seebeck coefficients and power factors , important for the conversion of heat to electrical energy , are obtained in polyaniline/carbon nanotube (PANI/CNT) composites in which PANI coats CNT networks (see figure). The values are several times larger than those of either of the individual components. This new approach has potential for synthesizing high-performance thermoelectric materials. [source]

Comparison of real-time methods for maximizing power output in microbial fuel cells

AICHE JOURNAL, Issue 10 2010
L. Woodward
Abstract Microbial fuel cells (MFCs) constitute a novel power generation technology that converts organic waste to electrical energy using microbially catalyzed electrochemical reactions. Since the power output of MFCs changes considerably with varying operating conditions, the online optimization of electrical load (i.e., external resistance) is extremely important for maintaining a stable MFC performance. The application of several real-time optimization methods is presented, such as the perturbation and observation method, the gradient method, and the recently proposed multiunit method, for maximizing power output of MFCs by varying the external resistance. Experiments were carried out in two similar MFCs fed with acetate. Variations in substrate concentration and temperature were introduced to study the performance of each optimization method in the face of disturbances unknown to the algorithms. Experimental results were used to discuss advantages and limitations of each optimization method. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Life-Cycle Assessment of Biosolids Processing Options

JOURNAL OF INDUSTRIAL ECOLOGY, Issue 2 2001
Gregory M. Peters
Summary Biosolids, also known as sewage sludge, are reusable organic materials separated from sewage during treatment. They can be managed in a variety of ways. Different options for biosolids handling in Sydney, Australia, are compared in this study using life-cycle assessment. Two key comparisons are made: of system scenarios (scenario 1 is local dewatering and lime amendment; scenario 2 is a centralized drying system) and of technologies (thermal drying versus lime amendment). The environmental issues addressed are energy consumption, global warming potential (GWP), and human toxicity potential (HTP). Scenario 2 would consume 24% more energy than scenario 1. This is due to the additional electricity for pumping and particularly the petrochemical methane that supplements biogas in the drier. A centralized system using the same technologies as scenario 1 has approximately the same impacts. The GWP and HTP of the different scenarios do not differ significantly. The assessment of technology choices shows significant differences. The ample supply of endogenous biogas at North Head sewage treatment plant for the drying option allows reductions, relative to the lime-amendment option, of 68% in energy consumption, 45% in GWP, and 23% in HTP. Technology choices have more significant influence on the environmental profile of biosolids processing than does the choice of system configurations. Controlling variables for environmental improvement are the selection of biogas fuel, avoidance of coalsourced electrical energy, minimization of trucking distances, and raising the solids content of biosolids products. [source]

Integrated approach to optimization of an ultrasonic processor

AICHE JOURNAL, Issue 11 2003
Vijayanand S. Moholkar
In an ultrasonic processor, the input electrical energy undergoes many transformations before getting converted into the cavitation energy, which is dissipated in the medium to bring out the physical/chemical change. An investigation of the influence of free and dissolved gas content of the system on the efficiency of this energy transformation chain is attempted. The results of the experiments reveal that the cavitation intensity produced in the medium varies significantly with the gas content of the system. A unified physical model, which combines basic theories of acoustics and bubble dynamics, has been used to explain the experimental results. An attempt has been made to establish the mechanism of the steps in the energy transformation chain, the involved physical parameters, and interrelations between them. It has been found that the influence of free and dissolved gas content of the medium on the overall energy transformation occurs through a complex inter-dependence of several parameters. Thus, simultaneous optimization of individual steps in the energy transformation chain, with an integrated approach, is necessary for the optimization of an ultrasonic processor. The present study puts forth a simple methodology, with the gas content of the system as manipulation parameter, for this purpose. [source]

Replacement of dopaminergic medication with subthalamic nucleus stimulation in Parkinson's disease: Long-term observation,

MOVEMENT DISORDERS, Issue 4 2009
Luigi M. Romito MD
Abstract Stimulation of the subthalamic nucleus (STN) is an effective treatment for advanced Parkinson's disease (PD), but the medication requirements after implant are poorly known. We performed a long-term prospective evaluation of 20 patients maintained at stable dopaminergic therapy for 5 years after bilateral STN implants, who were evaluated 6 months, 1 year, 3 years, and 5 years after surgery. We measured, during the entire observation period, the effect of deep brain stimulation on motor and functional outcome measures, the levodopa equivalent daily dose and the total electrical energy delivered. At 5 years, the UPDRS motor score had improved by 54.2% and levodopa equivalent dose was reduced by 61.9%, compared with preimplant. Dopaminergic medication remained stable during the observation period, but energy was progressively increased over time. Rest tremor, rigidity, gait, lower and upper limb akinesia, and total axial score were improved in decreasing order. Postural stability and speech improved transiently, whereas on-period freezing of gait, motor fluctuations and dyskinesias recovered durably. Functional measures did not show improvement in autonomy and daily living activities after STN implant. Chronic STN stimulation allows to replace for dopaminergic medications in the long-term at the expense of an increase of the total energy delivered. This is associated with marked improvement of motor features without a matching benefit in functional measures. © 2008 Movement Disorder Society [source]

Polarization effects and phase equilibria in high-energy-density polyvinylidene-fluoride-based polymers

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2010
V. Ranjan
Using first-principles calculations, the phase diagrams of polyvinylidene fluoride (PVDF) and its copolymers under an applied electric field are studied and phase transitions between their nonpolar , and polar , phases are discussed. The results show that the degree of copolymerization is a crucial parameter controlling the structural phase transition. In particular, for tetrafluoroethylene (TeFE) concentration above 12%, PVDF,TeFE is stabilized in the , phase, whereas the , phase is stable for lower concentrations. As larger electric fields are applied, domains with smaller concentrations ( 12%) undergo a transition from the , to the , phase until a breakdown field of ~600,MV,m,1 is reached. These structural phase transitions can be exploited for efficient storage of electrical energy. [source]

Intrinsic irreversibility in semiconductor light emission

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007
D. Ding
Abstract The study of the light emission in semiconductors using energy and entropy balance equations reveals that there is an intrinsic entropy generation built into the emission process. Such an irreversible property provides insight into the conversion of electrical energy into light. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Influence of imidazolium-based ionic liquids on the performance of ionic polymer conductor network composite actuators

POLYMER INTERNATIONAL, Issue 3 2010
Sheng Liu
Abstract We investigated the influence of ionic liquids (ILs) on the electromechanical performance of ionic polymer conductor network composite (IPCNC) actuators. Four imidazolium ILs with two cations of different sizes, i.e. 1-ethyl-3-methylimidazolium ([EMI+]) and 1-butyl-3-methylimidazolium ([BMI+]), and two anions of different sizes, i.e. tetrafluoroborate ([BF4,]) and trifluoromethanesulfonate ([Tf,]), were used. The IPCNC actuators were fabricated using a direct assembly method with RuO2/Nafion® nanocomposite as the electrode layers. The experimental results reveal that the actuator strain response time is nearly one order of magnitude shorter than the charging time. The IPCNCs with [EMI+][Tf,] exhibit the highest capacitance and the fastest response in both actuation and electrical charging as capacitors. In contrast, the IPCNCs with [EMI+][BF4,] display the slowest charging time and lowest value of capacitance as capacitors. The IPCNCs with [BMI+][BF4,] show the slowest response time. Furthermore, although the ILs used have a marked effect on the capacitances of the IPCNCs, using different ILs does not cause much change in the maximum strain of these IPCNCs. Consequently, the IPCNC actuators with [EMI+][BF4,] show the highest electromechanical conversion efficiency while those with [EMI+][Tf,] have the lowest electromechanical efficiency because of the highest capacitance and largest input electrical energy. The experimental results indicate that the two oppositely charged ions contribute in opposite manner to the strain response and hence the observed shorter actuation response time is likely caused by the strain cancellation effect between the cations and anions. Copyright © 2010 Society of Chemical Industry [source]

Conjugated polymers with tethered electron-accepting moieties as ambipolar materials for photovoltaics

POLYMER INTERNATIONAL, Issue 8 2007
Antonio Cravino
Abstract Conjugated polymers are of increasing interest as semiconductors for soft (opto)electronic devices, including photovoltaic elements. A promising conversion of solar energy into electrical energy is possible with blends of soluble electron donor-type conjugated polymers and fullerenes as electron-acceptor, transporting component. This approach, called bulk-heterojunction, suggested the preparation of intrinsic ambipolar materials to control simultaneously the electronic and morphological properties. On these bases, the covalent grafting of acceptor moieties onto conjugated backbones seemed attractive for the preparation of intrinsically ambipolar polymeric materials (,double-cable' polymers) as an alternative to donor,acceptor composites. The design, characterisation and application of this novel class of polymers are reviewed taking into account the current understanding of organic photovoltaics. Copyright © 2007 Society of Chemical Industry [source]

Energy scavenging for energy efficiency in networks and applications

BELL LABS TECHNICAL JOURNAL, Issue 2 2010
Kyoung Joon Kim
Telecommunication networks will play a huge part in enabling eco-sustainability of human activity; one of the first steps towards this is to dramatically increase network energy efficiency. In this paper we present two novel approaches for energy scavenging in networks. One involves thermal energy scavenging for improving wireless base station energy efficiency, and the other involves mechanical energy scavenging for powering sensors in sensor networks, for machine-to-machine (M2M) communications, and for smart grid applications. Power amplifier (PA) transistors in base stations waste 30 percent of the total energy used in a wireless access network (WAN) as heat to the environment. We propose a thermoelectric energy recovery module (TERM) to recover electricity from the waste heat of PA transistors. A fully coupled thermoelectric (TE) model, combining thermoelectricity and heat transfer physics, is developed to explore the power generation performance and efficiency as well as the thermal performance of the TERM. The TE model is comprehensively used to determine optimized pellet geometries for power generation and efficiency as a function of PA transistor heat dissipation, heat sink performance, and load resistance. Maximum power generation and efficiency for various parametric conditions are also explored. Untapped kinetic energy is almost everywhere in the form of vibrations. This energy can be converted into electrical energy by means of transducers to power wireless sensors and mobile electronics in the range of microwatts to a few milliwatts. However, many problems limit the efficiency of current harvesting generators: narrow bandwidth, low power density, micro-electro-mechanical system (MEMS) scaling, and inconsistency of vibrating sources. We explore energy scavenger designs based on multiple-mass systems to increase harvesting efficiency. A theoretical and experimental study of two degrees-of-freedom (2-DOF) vibration-powered generators is presented. Both electromagnetic and piezoelectric conversion methods are modeled by using a general approach. Experimental results for the multi-resonant system are in agreement with the analytical predictions and demonstrate significantly better performance in terms of maximum power density per total mass and a wider bandwidth compared to single DOF (1-DOF) generators. © 2010 Alcatel-Lucent. [source]

Light-Driven Thermoelectric Conversion Based on a Carbon Nanotube,Ionic Liquid Gel Composite

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8 2009
Eijiro Miyako Dr.
A photoinduced thermoelectric conversion system based on single-walled carbon nanotube,room temperature ionic liquid composite gels is reported. These new types of gel-based near-infrared laser-driven thermoelectric convertors generate high electrical energy. [source]