Alcohol-fuelled mobiles

4 Apr 2003

If you’ve ever had to face the amused contempt of your colleagues for suggesting a trip to the pub to recharge your batteries, the smile could soon be on the other side of their faces, if technology under development in the US to use alcohol to eliminate the need for plug-ins ever reaches the shops.

Studies in St Louis University are showing that a new kind of battery, fuelled by ethanol (more active and less toxic than methanol, which had been experimented on before) may be the future power source for all mobile handsets.

Although academics have been experimenting on the ‘biofuel’ cells for years they have so far been unsuccessful in developing anything that would generate power for more than a few days. But scientists at the institution have now developed a battery that has continued to generate electricity from the biofuel cell for more than two months and counting.

An ordinary fuel cell works by constantly changing the chemical energy of a fuel and an oxidant to create electrical energy, but a biofuel fuel cell uses biological molecules – in this case enzymes – to trigger this reaction.

In an interview with Wired magazine, a member of the research team, Nick Akers, said: “You can use any alcohol. You will be able to pour it straight out of the bottle and into your battery. We have run it on various types. It didn’t like carbonated beer and doesn’t seem fond of wine, but any other works fine.”

He added: “Once the system is fully optimised, probably one to three drops of alcohol could power your cell phone for a month.”

Ethanol is more active than methanol in the presence of enzymes, which are used as catalyst inside the cell.

“We chose these [dehydrogenase enzymes] because they strip protons from alcohol and this is the reaction we need to get electricity,” continued Akers.

One of the biggest obstacles that has prevented rapid development of this technology in the past is the tendency of these enzymes -which are very fragile – denature.

According to the scientists, their greatest achievement was in creating an environment for the enzymes in which they would remain active for much longer periods of time.

They did this by coating the electrodes of the biofuel cell with a polymer that contain pores which provide a perfect environment in which enzymes can thrive.

Other scientists are warning, however, that the rate of power that can be generated is low and this may restrict its use to certain applications such as sensors. At the moment the battery the team has developed can only generate two milliwatts of power per square centimetre, while the average mobile phone needs 500 milliwatts to work.

By Suzanne Byrne