Tag: 上海最新油压2018

Hydrogen fuel cells provide power when fuel supply is off

first_img Journal information: Nano Letters This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. (Phys.org) — Fuel cells, which generate electricity from the chemical energy of a fuel such as hydrogen, are not intrinsically capable of storing energy. When a fuel cell’s hydrogen supply runs out or is temporarily interrupted, the cell’s power output quickly decreases to zero. If an application requires energy storage, then the fuel cell must be coupled to an external charge storage device, such as a battery, which increases the weight and volume of the system. But now researchers have designed a hydrogen fuel cell with a new anode that can supply electricity up to 14 times longer than conventional fuel cells, which could be particularly useful for mobile energy applications. New fuel cell keeps going after the hydrogen runs out Copyright 2012 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Explore further (Left) Each dark speck within the nine white circles is a tiny fuel cell. An AA battery is shown for size comparison. Image credit: Caroline Perry, SEAS Communications (Right) One of the nine circles is magnified in this image, showing the wrinkled surface of the electrochemical membrane. Image credit: Quentin Van Overmeerecenter_img For now, the researchers do not know exactly what allows the new fuel cell to run after its supply is cut off. They identified and tested three possible charge storage mechanisms, with the results showing that reversible oxidation of the anode contributed a portion of the observed charge, but did not account for all of it. The finding suggests that the power generation in the absence of fuel arises from multiple mechanisms.Although identifying the underlying mechanisms will require further research, the discovery that vanadium oxide anodes can store energy and deliver power when the fuel supply is depleted could be useful for developing future miniature power sources. Applications could include miniature autonomous systems, military technologies, and other devices that need to operate for short time periods.”Unmanned aerial vehicles, for instance, would really benefit from this,” said Van Overmeere. “When it’s impossible to refuel in the field, an extra boost of stored energy could extend the device’s lifespan significantly.” More information: Quentin Van Overmeere, Kian Kerman, and Shriram Ramanathan. “Energy Storage in Ultrathin Solid Oxide Fuel Cells.” Nano Letters. DOI: 10.1021/nl301601y The laboratory setup for testing solid-oxide fuel cells. Image credit: Caroline Perry, SEAS Communications Citation: Hydrogen fuel cells provide power when fuel supply is off (2012, July 11) retrieved 18 August 2019 from https://phys.org/news/2012-07-hydrogen-fuel-cells-power.html The researchers, Quentin Van Overmeere, Kian Kerman, and Shriram Ramanathan, at the Harvard School of Engineering and Applied Sciences in Cambridge, Massachusetts, have published their study on the energy-storing solid-oxide fuel cells (SOFCs) in a recent issue of Nano Letters.In their study, the researchers fabricated the solid-oxide fuel cell’s anode with either vanadium oxide or a combination of vanadium oxide and porous platinum. Vanadium is known for its tendency to change oxidation state, a process that involves the transfer of electrons. Since a key to enabling fuel cells to store charge is to use materials that can reversibly transfer electric charges, vanadium’s properties make it a good candidate for these technologies. “This thin-film SOFC takes advantage of recent advances in low-temperature operation to incorporate a new and more versatile material,” said Ramanathan. “Vanadium oxide at the anode behaves as a multifunctional material, allowing the fuel cell to both generate and store energy.”The researchers’ experiments showed that, after the hydrogen fuel supply is turned off, fuel cells with the vanadium oxide anode could generate power for more than 3 minutes, compared with about 10-15 seconds for fuel cells with porous platinum anodes. Both fuel cells produced a comparable amount of power, and the researchers expect that future improvements will further extend this time. With the ability to store electrochemical energy, the new device could be thought of as combining the characteristics of a fuel cell and a battery.last_img read more

Read more…

Why Your Password is Hackerbait Infographic

first_img Attend this free webinar and learn how you can maximize efficiency while getting the most critical things done right. January 27, 2015 Opinions expressed by Entrepreneur contributors are their own. Another day, another warning of potential password pitfalls. Is it just us or do the days of handwritten letters and carrier pigeons seem to be increasingly appealing?We recently wrote about the fact that people are still using terrible passwords. The passwords themselves are just the beginning. A new infographic compiled by password-management firm Meldium shows some interesting (read: frightening) statistics on how our online behavior is leaving us vulnerable to cyberthieves.Related: Does President Obama’s Bid to Bolster Cyber Security Go Far Enough?Did you know, for instance, that 90 percent of employee passwords can be cracked in six hours? That’s less than a full work day! Moreover, nearly two-thirds of people use the same password for their many different accounts. Imagine if whomever you shared your Seamless account password with also had your online banking password. Not a pleasant thought.The infographic below offers a look at the common ways of keeping track of various passwords, and how often people forget the magic word or phrase for a site.Click to EnlargeRelated: 12 Tips to Protect Your Company Website From Hackers Free Webinar | Sept 5: Tips and Tools for Making Progress Toward Important Goals 1 min read Register Now »last_img read more

Read more…