Tiny Fuel Cell May Power Portable Electronics
for National Geographic News
|August 30, 2005|
As tech gadgetry from MP3 players to PDAs continues to evolve, the lithium- based batteries that run these power-thirsty gizmos are increasingly unable to keep up. Just think how annoying a laptop running out of juice can be.
Now chemical engineers at Purdue University in West Lafayette, Indiana, say they have come up with a solution to make our electronic devices dramatically more portable.
Their new method produces hydrogen for fuel cells that would automatically recharge batteries in portable electronics, such as notebook computers, eliminating the need to use a wall outlet.
"Currently, rechargeable batteries need a relatively long time to be charged," said Evgeny Shafirovich, one of the Purdue engineers who worked on the project. "The use of fuel cells and combustion-based hydrogen generators makes it possible to eliminate the need for plugging into the [power grid]."
In addition to increasing the portability of gadgets, the technology could also have important environmental benefits. Hydrogen can be produced from renewable energy sources and thus help reduce the emission of harmful greenhouse gases.
Fuel cell technology has, for example, long been touted as a future solution to automobile pollution. Applying similar technology to electronic devices may help lower demand for electricity from environmentally harmful power plants.
"If a hydrogen economy can be realized, the environmental benefits in terms of reduction in global warming gases is enormous," said Jay Gore, a mechanical engineering professor at Purdue who was not involved in the project.
Either methanol (wood alcohol) or hydrogen can be used for the new fuel cell technology, which provides a much higher energy-output-to-weight ratio than lithium-based batteries.
The methanol approach, however, has several drawbacks, including low power density (power ouput relative to a fuel cell's size) and other technical challenges. It also gives off carbon dioxide, a pollutant, as a byproduct.
The problem with hydrogen, by contrast, has always been storage. It is impossible to use high-pressure hydrogen gas containers or liquid hydrogen in portable electronic devicessuch devices would be bulky or dangerous.
The Purdue scientists have combined two previously known methods for producing hydrogen. Their technique uses the chemical compound sodium borohydride in a gel created by combining water with a water-absorbent thickener and aluminum particles.
"We have been able to find a chemical mixture that produces 6.7 weight percent hydrogen, and this is an important benchmark," said Arvind Varma, who led the research. Varma heads the School of Chemical Engineering at Purdue.
The 6.7 percent figure means that for every 100 grams of mixture, the scientists were able to produce 6.7 grams of hydrogen. Varma says his team hopes to increase the yield to about 10 percent through additional experiments.
The researchers envision that pellets of hydrogen-releasing material could be stored in credit card-size cartridges. Consumers could buy a fuel cartridge in a store for their mobile phone, laptop, digital camera, or PDA.
Users would install the cartridge in their electronic device, which would also contain a fuel cell and a rechargeable battery. When the stored energy of the battery dropped below a certain threshold, the processor would ignite combustion of one pellet. This would generate hydrogen, feeding the fuel cell, which in turn would produce electrical energy to recharge the battery.
"Now you can forget about recharging your battery and plugging into the electrical network," Shafirovich said. "All you need is to install a new cartridge when all pellets have been used."
While the technology would not eliminate the need for batteries, battery sizes could become much smaller.
The breakthrough may have important applications in portable electronics for soldiers and for equipment in spacecraft and submarines.
No one knows how many portable electronic devices exist worldwide, but conservative estimates place the number at more than a billion.
The new technology could have important environmental benefits, because electronics users would no longer have to plug into a common 110- or 220-volt electrical network.
According to the U.S. Department of Energy, more than half of the electricity consumed in the United States comes from coal-fired power plants, which are sources of smog, greenhouse gases, and mercury pollution.
"If hydrogen were to be produced from renewable sources, it will be great for the environment as there will be no pollutants," said Rakesh Agrawal, a Purdue chemical engineering professor who was not involved in the project.
Varma, the research team leader, says the products of the hydrogen reaction in his team's new fuel cell are environmentally benign and nontoxic.
The findings were presented Sunday at the annual meeting of the American Chemical Society in Washington, D.C. They will be detailed in the journal Combustion and Flame.
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