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Energies, Volume 3, Issue 5 (May 2010), Pages 899-1048

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Research

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Open AccessArticle A Transient Model for Fuel Cell Cathode-Water Propagation Behavior inside a Cathode after a Step Potential
Energies 2010, 3(5), 920-939; doi:10.3390/en3050920
Received: 9 March 2010 / Revised: 21 April 2010 / Accepted: 26 April 2010 / Published: 30 April 2010
Cited by 2 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Most of the voltage losses of proton exchange membrane fuel cells (PEMFC) are due to the sluggish kinetics of oxygen reduction on the cathode and the low oxygen diffusion rate inside the flooded cathode. To simulate the transient flooding in the cathode of
[...] Read more.
Most of the voltage losses of proton exchange membrane fuel cells (PEMFC) are due to the sluggish kinetics of oxygen reduction on the cathode and the low oxygen diffusion rate inside the flooded cathode. To simulate the transient flooding in the cathode of a PEMFC, a transient model was developed. This model includes the material conservation of oxygen, vapor, water inside the gas diffusion layer (GDL) and micro-porous layer (MPL), and the electrode kinetics in the cathode catalyst layer (CL). The variation of hydrophobicity of each layer generated a wicking effect that moves water from one layer to the other. Since the GDL, MPL, and CL are made of composite materials with different hydrophilic and hydrophobic properties, a linear function of saturation was used to calculate the wetting contact angle of these composite materials. The balance among capillary force, gas/liquid pressure, and velocity of water in each layer was considered. Therefore, the dynamic behavior of PEMFC, with saturation transportation taken into account, was obtained in this study. A step change of the cell voltage was used to illustrate the transient phenomena of output current, water movement, and diffusion of oxygen and water vapor across the entire cathode. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessArticle A Net-Present Value Analysis for a Wind Turbine Purchase at a Small US College
Energies 2010, 3(5), 943-959; doi:10.3390/en3050943
Received: 29 March 2010 / Accepted: 20 April 2010 / Published: 6 May 2010
Cited by 5 | PDF Full-text (140 KB) | HTML Full-text | XML Full-text
Abstract
Wind power is becoming an increasingly attractive method of electric power generation due to concerns with global climate change, increasing uncertainty of future oil supplies, and energy security. While most large-scale wind turbines are part of wind farms, which help states meet state
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Wind power is becoming an increasingly attractive method of electric power generation due to concerns with global climate change, increasing uncertainty of future oil supplies, and energy security. While most large-scale wind turbines are part of wind farms, which help states meet state renewable energy standards, several colleges and universities in the United States have purchased wind turbines for financial and educational purposes. This paper gives details of a cost-benefit analysis completed for a small liberal arts college in Illinois, Principia College, which is considering buying a single large-scale turbine. The process set forth here can easily be adapted to any college, university, or school. It is found that the project has a positive net present value for both a 20-year scenario and a 30-year scenario. Assuming the project did not receive any grants, Principia College would need to have an annual real return rate of about 6% on its initial investment to gain the same economic benefits. Full article
(This article belongs to the Special Issue Wind Energy)
Open AccessArticle Simulation of the Impact of SRT on Anaerobic Digestability of Ultrasonicated Hog Manure
Energies 2010, 3(5), 974-988; doi:10.3390/en3050974
Received: 26 March 2010 / Accepted: 15 April 2010 / Published: 11 May 2010
Cited by 9 | PDF Full-text (231 KB) | HTML Full-text | XML Full-text
Abstract
Ultrasonication at a specific energy of 500 kJ/kgTS was applied to hog manure in a continuous mode completely mixed anaerobic digestion. A process model in BioWin was developed, calibrated and tested at different solids retention times (SRTs) to evaluate the process economics. The
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Ultrasonication at a specific energy of 500 kJ/kgTS was applied to hog manure in a continuous mode completely mixed anaerobic digestion. A process model in BioWin was developed, calibrated and tested at different solids retention times (SRTs) to evaluate the process economics. The results showed that there was a 36% increase in volatile suspended solids (VSS) removal efficiency, a 20% increase in methane production rate, a 13.5% increase in destruction of bound proteins, and a reduction from 988 to 566 ppm in H2S concentration in the digester headspace. Furthermore, a calibrated model of the process using BioWin to assess the impact of SRTs on the economics of anaerobic digestion for unsonicated and sonicated hog manure revealed that ultrasonication resulted in a net benefit of $42–46/ton dry solids at SRTs of 15–30 days. Full article

Review

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Open AccessReview Microbial Fuel Cells, A Current Review
Energies 2010, 3(5), 899-919; doi:10.3390/en3050899
Received: 19 January 2010 / Revised: 13 March 2010 / Accepted: 24 March 2010 / Published: 28 April 2010
Cited by 150 | PDF Full-text (507 KB) | HTML Full-text | XML Full-text
Abstract
Microbial fuel cells (MFCs) are devices that can use bacterial metabolism to produce an electrical current from a wide range organic substrates. Due to the promise of sustainable energy production from organic wastes, research has intensified in this field in the last few
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Microbial fuel cells (MFCs) are devices that can use bacterial metabolism to produce an electrical current from a wide range organic substrates. Due to the promise of sustainable energy production from organic wastes, research has intensified in this field in the last few years. While holding great promise only a few marine sediment MFCs have been used practically, providing current for low power devices. To further improve MFC technology an understanding of the limitations and microbiology of these systems is required. Some researchers are uncovering that the greatest value of MFC technology may not be the production of electricity but the ability of electrode associated microbes to degrade wastes and toxic chemicals. We conclude that for further development of MFC applications, a greater focus on understanding the microbial processes in MFC systems is required. Full article
(This article belongs to the Special Issue Fuel Cells)
Open AccessReview A High Capacity Li-Ion Cathode: The Fe(III/VI) Super-Iron Cathode
Energies 2010, 3(5), 960-972; doi:10.3390/en3050960
Received: 31 March 2010 / Accepted: 12 April 2010 / Published: 6 May 2010
Cited by 18 | PDF Full-text (1354 KB) | HTML Full-text | XML Full-text
Abstract
A super-iron Li-ion cathode with a 3-fold higher reversible capacity (a storage capacity of 485 mAh/g) is presented. One of the principle constraints to vehicle electrification is that the Li-ion cathode battery chemistry is massive, and expensive. Demonstrated is a 3 electron storage
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A super-iron Li-ion cathode with a 3-fold higher reversible capacity (a storage capacity of 485 mAh/g) is presented. One of the principle constraints to vehicle electrification is that the Li-ion cathode battery chemistry is massive, and expensive. Demonstrated is a 3 electron storage lithium cathodic chemistry, and a reversible Li super-iron battery, which has a significantly higher capacity than contemporary Li-ion batteries. The super-iron Li-ion cathode consists of the hexavalent iron (Fe(VI)) salt, Na2FeO4, and is formed from inexpensive and clean materials. The charge storage mechanism is fundamentally different from those of traditional lithium ion intercalation cathodes. Instead, charge storage is based on multi-electron faradaic reduction, which considerably enhances the intrinsic charge storage capacity. Full article
(This article belongs to the Special Issue Lithium-ion Batteries)
Open AccessReview CFD in Wind Energy: The Virtual, Multiscale Wind Tunnel
Energies 2010, 3(5), 989-1013; doi:10.3390/en3050989
Received: 16 March 2010 / Accepted: 24 April 2010 / Published: 17 May 2010
Cited by 27 | PDF Full-text (357 KB) | HTML Full-text | XML Full-text
Abstract
Over the past two decades, computational fluid dynamics and particularly the finite volume method have been increasingly used to predict the performance of wind turbines within their environment. Increases in available computational power has led to the application of RANS-based models to more
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Over the past two decades, computational fluid dynamics and particularly the finite volume method have been increasingly used to predict the performance of wind turbines within their environment. Increases in available computational power has led to the application of RANS-based models to more and more complex flow problems and permitted the use of LES-based models where previously not possible. The following article reviews the development of CFD as applied by the wind energy community from small to large scale: from the flow around 2D airfoils to the flow through an entire wind farm. Full article
(This article belongs to the Special Issue Wind Energy)
Open AccessReview Exploiting Laboratory and Heliophysics Plasma Synergies
Energies 2010, 3(5), 1014-1048; doi:10.3390/en30501014
Received: 1 March 2010 / Revised: 5 May 2010 / Accepted: 18 May 2010 / Published: 25 May 2010
Cited by 1 | PDF Full-text (2926 KB) | HTML Full-text | XML Full-text
Abstract
Recent advances in space-based heliospheric observations, laboratory experimentation, and plasma simulation codes are creating an exciting new cross-disciplinary opportunity for understanding fast energy release and transport mechanisms in heliophysics and laboratory plasma dynamics, which had not been previously accessible. This article provides an
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Recent advances in space-based heliospheric observations, laboratory experimentation, and plasma simulation codes are creating an exciting new cross-disciplinary opportunity for understanding fast energy release and transport mechanisms in heliophysics and laboratory plasma dynamics, which had not been previously accessible. This article provides an overview of some new observational, experimental, and computational assets, and discusses current and near-term activities towards exploitation of synergies involving those assets. This overview does not claim to be comprehensive, but instead covers mainly activities closely associated with the authors’ interests and reearch. Heliospheric observations reviewed include the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the National Aeronautics and Space Administration (NASA) Solar Terrestrial Relations Observatory (STEREO) mission, the first instrument to provide remote sensing imagery observations with spatial continuity extending from the Sun to the Earth, and the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Japanese Hinode spacecraft that is measuring spectroscopically physical parameters of the solar atmosphere towards obtaining plasma temperatures, densities, and mass motions. The Solar Dynamics Observatory (SDO) and the upcoming Solar Orbiter with the Heliospheric Imager (SoloHI) on-board will also be discussed. Laboratory plasma experiments surveyed include the line-tied magnetic reconnection experiments at University of Wisconsin (relevant to coronal heating magnetic flux tube observations and simulations), and a dynamo facility under construction there; the Space Plasma Simulation Chamber at the Naval Research Laboratory that currently produces plasmas scalable to ionospheric and magnetospheric conditions and in the future also will be suited to study the physics of the solar corona; the Versatile Toroidal Facility at the Massachusetts Institute of Technology that provides direct experimental observation of reconnection dynamics; and the Swarthmore Spheromak Experiment, which provides well-diagnosed data on three-dimensional (3D) null-point magnetic reconnection that is also applicable to solar active regions embedded in pre-existing coronal fields. New computer capabilities highlighted include: HYPERION, a fully compressible 3D magnetohydrodynamics (MHD) code with radiation transport and thermal conduction; ORBIT-RF, a 4D Monte-Carlo code for the study of wave interactions with fast ions embedded in background MHD plasmas; the 3D implicit multi-fluid MHD spectral element code, HiFi; and, the 3D Hall MHD code VooDoo. Research synergies for these new tools are primarily in the areas of magnetic reconnection, plasma charged particle acceleration, plasma wave propagation and turbulence in a diverging magnetic field, plasma atomic processes, and magnetic dynamo behavior. Full article
(This article belongs to the Special Issue Nuclear Fusion)

Other

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Open AccessCommentary Oil and the Best Brain of the 20th Century
Energies 2010, 3(5), 940-942; doi:10.3390/en3050940
Received: 8 April 2010 / Accepted: 29 April 2010 / Published: 30 April 2010
PDF Full-text (77 KB) | HTML Full-text | XML Full-text
Abstract
If you meet someone at a party who says that he is Napoleon, you don’t start discussing cavalry tactics at Waterloo ─ Professor Robert Solow

Well that depends, Robert. If he is the gentleman who gave the party, and you would like to
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If you meet someone at a party who says that he is Napoleon, you don’t start discussing cavalry tactics at Waterloo ─ Professor Robert Solow

Well that depends, Robert. If he is the gentleman who gave the party, and you would like to receive another invitation from him some day, you might feel it wise to suggest that if his boys had been riding elephants or dinosaurs instead of horses, he might have enjoyed another few years in swinging Paris instead of being turned over to that nasty Sir Hudson Lowe on St. Helena. [...] Full article
(This article belongs to the Special Issue Oil Recovery)
Open AccessCorrection Correction: Energy Resources in the Future
Energies 2010, 3(5), 973; doi:10.3390/en3050973
Received: 30 April 2010 / Published: 11 May 2010
PDF Full-text (36 KB) | HTML Full-text | XML Full-text
Abstract We found three errors in our paper published in Energies [1]. The corrections are as following: [...] Full article
(This article belongs to the Special Issue Nuclear Fusion)

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