Probably the coolest thing we saw at IFA in Berlin last week was a set of batteries that run off water. They're known as the NoPoPo (non-pollution power) Aqua Battery, and they work simply by inserting liquid into the base with a teat pipette.
They come in a range of battery sizes, and according to the manufacturer, a single AAA version can run a small handheld torch light for up to 20 hours. Incredibly, these batteries also work with other types of liquid: we saw them tested with beer and apple juice, but the makers say they can run off cola, saliva or even urine. That's apple juice in the picture, although now we come to think about it, it was rather tangy.
Inside the batteries, a mixture of carbon and magnesium reacts with the liquid to produce power -- around 500mAh in the case of an AA battery. Unlike conventional dry-cell batteries, NoPoPo batteries don't deteriorate over a short time period. They can retain their charge for ten years, making them perfect for emergency situations. Be warned though, they can only be refilled a finite number of times.
They're also far better for the environment -- they don't contain harmful substances, such as mercury, hexavalent chrome, lead or cadmium, so you can dispose of them with a clearer conscience.
As well as powering small devices, NoPoPo batteries can be linked in series to create larger power cells. We saw a bunch of them joined up to power lamps and the effect was astonishing.
Unfortunately they're only being sold in Japan at the moment, but expect to see them hit the West in early 2008. -Rory Reid