Showing papers on "Electric power published in 2012"

Challenges Facing Lithium Batteries and Electrical Double‐Layer Capacitors

Abstract: Energy-storage technologies, including electrical double-layer capacitors and rechargeable batteries, have attracted significant attention for applications in portable electronic devices, electric vehicles, bulk electricity storage at power stations, and “load leveling” of renewable sources, such as solar energy and wind power. Transforming lithium batteries and electric double-layer capacitors requires a step change in the science underpinning these devices, including the discovery of new materials, new electrochemistry, and an increased understanding of the processes on which the devices depend. The Review will consider some of the current scientific issues underpinning lithium batteries and electric double-layer capacitors.

Triboelectric-generator-driven pulse electrodeposition for micropatterning.

Abstract: By converting ambient energy into electricity, energy harvesting is capable of at least offsetting, or even replacing, the reliance of small portable electronics on traditional power supplies, such as batteries. Here we demonstrate a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation. Owing to the coupling of contact charging and electrostatic induction, electric generation was achieved with a cycled process of contact and separation between two polymer films. A detailed theory is developed for understanding the proposed mechanism. The instantaneous electric power density reached as high as 31.2 mW/cm(3) at a maximum open circuit voltage of 110 V. Furthermore, the generator was successfully used without electric storage as a direct power source for pulse electrodeposition (PED) of micro/nanocrystalline silver structure. The cathodic current efficiency reached up to 86.6%. Not only does this work present a new type of generator that is featured by simple fabrication, large electric output, excellent robustness, and extremely low cost, but also extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting.

Self-organized synchronization in decentralized power grids.

Abstract: Robust synchronization (phase locking) of power plants and consumers centrally underlies the stable operation of electric power grids. Despite current attempts to control large-scale networks, even their uncontrolled collective dynamics is not fully understood. Here we analyze conditions enabling self-organized synchronization in oscillator networks that serve as coarse-scale models for power grids, focusing on decentralizing power sources. Intriguingly, we find that whereas more decentralized grids become more sensitive to dynamical perturbations, they simultaneously become more robust to topological failures. Decentralizing power sources may thus facilitate the onset of synchronization in modern power grids.

State Estimation in Electric Power Grids: Meeting New Challenges Presented by the Requirements of the Future Grid

Abstract: This article provides a survey on state estimation (SE) in electric power grids and examines the impact on SE of the technological changes being proposed as a part of the smart grid development. Although SE at the transmission level has a long history, further research and development of innovative SE schemes, including those for distribution systems, are needed to meet the new challenges presented by the requirements of the future grid. This article also presents some example topics that signal processing (SP) research can contribute to help meet those challenges.

Electric Springs—A New Smart Grid Technology

Abstract: The scientific principle of “mechanical springs” was described by the British physicist Robert Hooke in the 1660's. Since then, there has not been any further development of the Hooke's law in the electric regime. In this paper, this technological gap is filled by the development of “electric springs.” The scientific principle, the operating modes, the limitations, and the practical realization of the electric springs are reported. It is discovered that such novel concept has huge potential in stabilizing future power systems with substantial penetration of intermittent renewable energy sources. This concept has been successfully demonstrated in a practical power system setup fed by an ac power source with a fluctuating wind energy source. The electric spring is found to be effective in regulating the mains voltage despite the fluctuation caused by the intermittent nature of wind power. Electric appliances with the electric springs embedded can be turned into a new generation of smart loads, which have their power demand following the power generation profile. It is envisaged that electric springs, when distributed over the power grid, will offer a new form of power system stability solution that is independent of information and communication technology.

Power Electronics and Control Techniques for Maximum Energy Harvesting in Photovoltaic Systems

Abstract: Incentives provided by European governments have resulted in the rapid growth of the photovoltaic (PV) market. Many PV modules are now commercially available, and there are a number of power electronic systems for processing the electrical power produced by PV systems, especially for grid-connected applications. Filling a gap in the literature, Power Electronics and Control Techniques for Maximum Energy Harvesting in Photovoltaic Systems brings together research on control circuits, systems, and techniques dedicated to the maximization of the electrical power produced by a photovoltaic (PV) source. Tools to Help You Improve the Efficiency of Photovoltaic Systems The book supplies an overview of recent improvements in connecting PV systems to the grid and highlights various solutions that can be used as a starting point for further research and development. It begins with a review of methods for modeling a PV array working in uniform and mismatched conditions. The book then discusses several ways to achieve the best maximum power point tracking (MPPT) performance. A chapter focuses on MPPT efficiency, examining the design of the parameters that affect algorithm performance. The authors also address the maximization of the energy harvested in mismatched conditions, in terms of both power architecture and control algorithms, and discuss the distributed MPPT approach. The final chapter details the design of DC/DC converters, which usually perform the MPPT function, with special emphasis on their energy efficiency. Get Insights from the Experts on How to Effectively Implement MPPT Written by well-known researchers in the field of photovoltaic systems, this book tackles state-of-the-art issues related to how to extract the maximum electrical power from photovoltaic arrays under any weather condition. Featuring a wealth of examples and illustrations, it offers practical guidance for researchers and industry professionals who want to implement MPPT in photovoltaic systems.

Control of Power Inverters in Renewable Energy and Smart Grid Integration

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The Progressive Smart Grid System from Both Power and Communications Aspects

Abstract: The present electric power system structure has lasted for decades; it is still partially proprietary, energy-inefficient, physically and virtually (or cyber) insecure, as well as prone to power transmission congestion and consequent failures. Recent efforts in building a smart grid system have focused on addressing the problems of global warming effects, rising energy-hungry demands, and risks of peak loads. One of the major goals of the new system is to effectively regulate energy usage by utilizing the backbone of the prospectively deployed Automatic Meter Reading (AMR), Advanced Meter Infrastructure (AMI), and Demand Response (DR) programs via the advanced distribution automation and dynamic pricing models. The function of the power grid is no longer a system that only supplies energy to end users, but also allows consumers to contribute their clean energy back to the grid in the future. In the meantime, communications networks in the electric power infrastructure enact critical roles. Intelligent automation proposed in smart grid projects include the Supervisory Control And Data Acquisition/Energy Management Systems (SCADA/EMS) and Phasor Management Units (PMU) in transmission networks, as well as the AMR/AMI associated with field/neighborhood area networks (FAN/NAN) and home area networks (HAN) at the distribution and end-use levels. This article provides an overview of the essentials of the progressive smart grid paradigm and integration of different communications technologies for the legacy power system. Additionally, foreseeable issues and challenges in designing communications networks for the smart grid system are also rigorously deliberated in this paper.

Design for reliability of power electronic systems

Abstract: Advances in power electronics enable efficient and flexible processing of electric power in the application of renewable energy sources, electric vehicles, adjustable-speed drives, etc. More and more efforts are devoted to better power electronic systems in terms of reliability to ensure high availability, long lifetime, sufficient robustness, low maintenance cost and low cost of energy. However, the reliability predictions are still dominantly according to outdated models and terms, such as MIL-HDBK-217H handbook models, Mean-Time-To-Failure (MTTF), and Mean-Time-Between-Failures (MTBF). A collection of methodologies based on Physics-of-Failure (PoF) approach and mission profile analysis are presented in this paper to perform reliability-oriented design of power electronic systems. The corresponding design procedures and reliability prediction models are provided. Further on, a case study on a 2.3 MW wind power converter is discussed with emphasis on the reliability critical components IGBTs. Different aspects of improving the reliability of the power converter are mapped. Finally, the challenges and opportunities to achieve more reliable power electronic systems are addressed.

The Prospects for Cost Competitive Solar PV Power

Abstract: New solar Photovoltaic (PV) installations have grown globally at a rapid pace in recent years. We provide a comprehensive assessment of the cost competitiveness of this electric power source. Based on data available for the second half of 2011, we conclude that utility-scale PV installations are not yet cost competitive with fossil fuel power plants. In contrast, commercial-scale installations have already attained cost parity in the sense that the generating cost of power from solar PV is comparable to the retail electricity prices that commercial users pay, at least in certain parts of the U.S. This conclusion is shown to depend crucially on both the current federal tax subsidies for solar power and an ideal geographic location for the solar installation. Projecting recent industry trends into the future, we estimate that utility-scale solar PV facilities are on track to become cost competitive by the end of this decade. Furthermore, commercial-scale installations could reach “grid parity” in about ten years, if the current federal tax incentives for solar power were to expire at that point.

Comparing the Topological and Electrical Structure of the North American Electric Power Infrastructure

Abstract: The topological (graph) structure of complex networks often provides valuable information about the performance and vulnerability of the network. However, there are multiple ways to represent a given network as a graph. Electric power transmission and distribution networks have a topological structure that is straightforward to represent and analyze as a graph. However, simple graph models neglect the comprehensive connections between components that result from Ohm's and Kirchhoff's laws. This paper describes the structure of the three North American electric power interconnections, from the perspective of both topological and electrical connectivity. We compare the simple topology of these networks with that of random, preferential-attachment, and small-world networks of equivalent sizes and find that power grids differ substantially from these abstract models in degree distribution, clustering, diameter and assortativity, and thus conclude that these topological forms may be misleading as models of power systems. To study the electrical connectivity of power systems, we propose a new method for representing electrical structure using electrical distances rather than geographic connections. Comparisons of these two representations of the North American power networks reveal notable differences between the electrical and topological structures of electric power networks.

Power transmitting apparatus, power receiving apparatus, and power transmitting method

Abstract: Provided is a electric power transmitting apparatus ( 300 ) that has sub-electric power transmission mode, and main electric power transmission mode for transmitting power larger than that transmitted in the sub-electric power transmission mode. A power transmitting unit ( 310 ) transmits power in a wireless manner. A electric power transmission control unit ( 320 ) controls, in sub-electric power transmission mode, power to be transmitted by means of the power transmitting unit ( 310 ) and transmission timing of the electric power transmission such that at least power that the electric power receiving apparatus needs to transmit power request notification is transmitted at random intervals. A electric power transmission control unit ( 320 ) performs switching to the main electric power transmission mode, in the cases where a communication unit ( 350 ) acquired the power request notification transmitted from the electric power receiving apparatus.

Managing demand charge tariffs for electric power

Abstract: A method for demand charge management at public charging stations may be provided. The method may comprise collecting information related to electric vehicle (EV) charging from a plurality of interested parties by an infrastructure service cloud, computing charge rate offers based on the collected information by the infrastructure service cloud, transmitting the computed charge rate offers to a driver of an EV by the infrastructure service cloud, and reserving a charge spot for the driver using the infrastructure service when the driver accepts an offer.

Wireless energy transfer systems

Abstract: An inductively coupled power system for use in a structure having at least one power emitter electrically coupled to an external electrical power source and at least one power receptor directly coupled to a load with direct electrical connections, which is configured to inductively couple to energy wirelessly resonating from the at least one power emitter and to convert the inductively received energy to a desired output energy configuration for supply to the load. The system can also include at least one passive power emitter that is configured to be inductively coupled to energy wirelessly resonating from the at least one power emitter or the at least one passive power emitter.

Sustainable biogas energy in Poland: Prospects and challenges

Abstract: The article investigates prospects and challenges for expanding of sustainable biogas energy in Poland. The number of Polish biogas fuelled power plants and installed electrical power during the 2001–2010 decade is presented. Current economical incentives for biogas energy are discussed. It is emphasized that some revisions to the Polish tradable certificate system are urgently needed in order to encourage energy crop cultivation and the use of best available power technologies. Further, promising, but mostly unexplored feedstocks, such as energy crops, grasses and sorted municipal organic wastes are analyzed. It is also revealed that agrobiogas is characterized by a unique feature of ‘negative net’ CO2 atmospheric emissions and thus the role of agrobiogas in solving Polish CCS dilemmas is discussed. In regard to biogas energy systems it is stressed, that the cost of electricity from biogas is almost independent on the size of agrobiogas CHP power plants in the range of 0.2–5 MWe. Therefore agrobiogas energy is well suited for distributed energy systems involving small-scale agrobiogas power plants offering more green jobs and improved local waste management characteristics. Finally, reliable technologies suitable for biogas energy conversion and upgrading of biogas fuel to marketable gaseous fuels are briefly characterized.

Method and apparatus for actively managing electric power supply for an electric power grid

Abstract: Systems and methods for managing power supplied over an electric power grid by an electric utility and/or other market participants to multiplicity of grid elements and devices for supply and/or load curtailment as supply, each of which having a Power Supply Value (PSV) associated with its energy consumption and/or reduction in consumption and/or supply, and wherein messaging is managed through a network by a Coordinator using IP messaging for communication with the grid elements and devices, with the energy management system (EMS), and with the utilities, market participants, and/or grid operators.

Method and Apparatus for Actively Managing Consumption of Electric Power Supplied by One or More Electric Utilities

Abstract: A system manages consumption of power supplied by at least one electric utility to multiple power consuming devices. Power flow to the power consuming devices is enabled and disabled by controllable devices controlled by one or more client devices. According to one embodiment, a group of one or more client devices to which to communicate a power control message is determined. The power control message indicates at least one of an amount of electric power to be reduced and an identification of one or more controllable devices to be instructed to disable a flow of electric power to one or more associated power consuming devices. The power control message is communicated to the determined group of client devices to initiate a power reduction event. Subsequent to initiation of the power reduction event, a determination is made that at least one controllable device has prematurely exited the power reduction event.

Optimal deployment of charging stations for electric vehicular networks

Abstract: In a smart city environment, we look at a new, upcoming generation of vehicles running on electric power supplied by on-board batteries. Best recharging options include charging at home, as well as charging at public areas. In this setting, electric vehicles will be informed about public charging stations using wireless communications. As the charging stations are shared resources, cooperating electric vehicles have the potential to avoid unbalanced use of recharging stations and lengthy waiting times.We present a model for electric vehicles and their battery depletion, vehicle mobility, charging stations, and give a solution for optimal placement of charging stations in a smart city. Our placement approach is based on genetic programming and simulation of electric vehicles which move on a real map of a European city. We show that after a few evolution steps, an optimal solution of the charging infrastructure is derived based on mean trip times of electric vehicles.

Demand profile study of battery electric vehicle under different charging options

Abstract: An increased research on electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) deals with their flexible use in electric power grids. Several research projects on smart grids and electric mobility are now looking into realistic models representing the behavior of an EV during charging, including nonlinearities. In this work, modeling, simulation and testing of the demand profile of a battery-EV are conducted. Realistic work conditions for a lithium-ion EV battery and battery charger are considered as the base for the modeling. Simulation results show that EV charging generates different demand profiles into the grid, depending on the applied charging option. Moreover, a linear region for the control of EV chargers is identified in the range of 20-90% state-of-charge (SOC). Experiments validate the proposed model.

A Review of Power Electronics Based Microgrids

Abstract: The increased penetration of Distributed Energy Resources (DER) is challenging the entire architecture of conventional electrical power system. Microgrid paradigm, featuring higher flexibility and reliability, becomes an attractive candidate for the future power grid. In this paper, an overview of microgrid configurations is given. Then, possible structure options and control methods of DER units are presented, which is followed by the descriptions of system controls and power management strategies for AC microgrids. Finally, future trends of microgrids are discussed pointing out how this concept can be a key to achieve a more intelligent and flexible power system.

A Review of Power Electronics Based Microgrids

Abstract: The increased penetration of Distributed Energy Resources (DER) is challenging the entire architecture of conventional electrical power system. Microgrid paradigm, featuring higher flexibility and reliability, becomes an attractive candidate for the future power grid. In this paper, an overview of microgrid configurations is given. Then, possible structure options and control methods of DER units are presented, which is followed by the descriptions of system controls and power management strategies for AC microgrids. Finally, future trends of microgrids are discussed pointing out how this concept can be a key to achieve a more intelligent and flexible power system.

Radio Frequency Energy Harvesting and Management for Wireless Sensor Networks

Abstract: Radio Frequency (RF) Energy Harvesting holds a promising future for generating a small amount of electrical power to drive partial circuits in wirelessly communicating electronics devices. Reducing power consumption has become a major challenge in wireless sensor networks. As a vital factor affecting system cost and lifetime, energy consumption in wireless sensor networks is an emerging and active research area. This chapter presents a practical approach for RF Energy harvesting and management of the harvested and available energy for wireless sensor networks using the Improved Energy Efficient Ant Based Routing Algorithm (IEEABR) as our proposed algorithm. The chapter looks at measurement of the RF power density, calculation of the received power, storage of the harvested power, and management of the power in wireless sensor networks. The routing uses IEEABR technique for energy management. Practical and real-time implementations of the RF Energy using Powercast harvesters and simulations using the energy model of our Libelium Waspmote to verify the approach were performed. The chapter concludes with performance analysis of the harvested energy, comparison of IEEABR and other traditional energy management techniques, while also looking at open research areas of energy harvesting and management for wireless sensor networks.