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| CSIRO | SOLVE | Issue 1 Nov 04 | |
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MICRO FUEL CELLS
Super Cells
By Graeme O'Neill
Mobile phone 'batteries' that can go for a month without charging may soon be a reality. Dr Sukhvinder Badwal’s CSIRO research team is developing a compact, lightweight battery that could power a laptop computer for up to 24 hours, or a mobile phone for up to a month, before requiring a recharge.
One year into its three-year project, Badwal’s team at CSIRO Manufacturing and Infrastructure Technology in Clayton,Victoria, has already developed working prototypes of both hydrogen- and methanol-powered micro fuel cells, and aims to have commercial versions ready for market as early as 2007. Badwal says multinational electronics companies like Sony, Sanyo, Nokia and Hewlett-Packard are also racing to develop micro fuel cells as replacements for rechargeable batteries. But the global market will run into tens of billions of dollars, so there will be room for multiple players – and Badwal says Australia is well positioned to compete. He describes the micro fuel cell “as a totally new paradigm”, that could rapidly evolve into a billiondollar industry for Australia. Badwal predicts that micro fuel cells, ranging from 0.5 watts to 50 watts in output, will revolutionise the microelectronics industry, by providing operating and standby times 6 to 7 times longer than the current generation of lithium-ion batteries. They will be used in laptop computers, mobile phones, video cameras, portable TVs, DVD and audio devices, games consoles and power packs for soldiers in the field. They could also power autonomous remote-sensing devices or small, silent robotic aircraft that will monitor the terrestrial environment, collect weather data in remote areas or over the oceans, or carry video cameras and other surveillance devices for homeland security. Eventually, scaled-up micro polymer electrolyte membrane fuel cells ranging in output from 100 W up to 2 kilowatts could power variable message signs, wheelchairs, provide emergency lighting or even power entire households. Badwal’s team has had a hydrogen-powered prototype operating continuously for nearly 7000 hours, with no significant degradation or loss of performance. They aim to achieve a working life of at least 15,000 hours, or nearly two years of continuous operation. The cells can readily be shut down, and restarted, and when the compact cartridge of hydrogen or methanol runs out, another can be slotted into place to reactivate the cell within seconds. Badwal says the heart of the micro fuel cell is a thin but tough membrane only 20 to 50 microns thick (1 micron = .001 mm), made of a special polymer that conducts protons.
The protons reacts with oxygen on the other side of the membrane, forming pure water that simply evaporates away, while an electrode gathers the electrons, completing an electrical circuit that powers the host device. A different type of polymer is used in the methanol cell. The methanol (CH3OH) is diluted with water, and the mixture dissociates into carbon dioxide and protons; thereafter the reaction is the same as for the hydrogen fuel cell, except that the methanol fuel cell produces small amounts of carbon dioxide in addition to water. Badwal says the current generation of polymer electrolyte membrane fuel cells being developed for transport applications to power cars and buses are bulky devices, that require hydrogen and oxygen to be pumped into them under pressure. For a micro fuel cell, pumps and plumbing are out. A complex network of micro-channels will distribute the hydrogen or methanol fuel evenly across the polymer membrane.The cell must be sealed, and virtually 100 per cent efficient, completely consuming each fuel charge. It will “breathe” by absorbing oxygen directly from the atmosphere. Badwal says the micro fuel cell technology his team is developing is at the cutting edge of the technology internationally. He believes that the team has all the requisite expertise in fuel cells, microfluidics, microtechnology, polymer chemistry and manufacturing located at one site in Clayton that gives it a logistical advantage over most of its multinational rivals. For further information contact: |
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The secret of its phenomenal
performance is that it’s
not a battery at all, but a tiny, polymer-electrolyte membrane (PEM) fuel cell
that produces electricity electrochemically, by reacting hydrogen or methanol
with oxygen.The reaction mimics the chemistry of combustion, but runs “cool”,
at just a few degrees above room temperature.
Hydrogen,
the simplest element, comprises a positively charged proton and a negatively
charged electron. The catalyst on the polymer
electrolyte membrane causes the hydrogen atoms to dissociate into protons and
electrons.
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