How new battery tech will make your gadgets last longer

Fuelling the Future

Invariably, when conversation turns to innovative new energy sources, sooner or later the fuel cell crops up. So it’s somewhat surprising, perhaps, to learn that the fuel cell was invented over 150 year ago. Despite their long heritage, however, and while fuel cells have been use used for decades in niche applications like submarines and spacecraft, they are still to make a significant impact on everyday life. Yet, potentially, they have a lot to offer.

Like primary batteries, the chemical reaction that generates electricity in a fuel cell cannot be reversed in the cell. Where it differs from a non-rechargeable battery, however, is that the supply of chemicals used in the cell can be replenished. In the first fuel cells, the chemical reaction was between hydrogen, which is the fuel supplied to the cell, and oxygen taken from the air to produce water which is discharged into the atmosphere as steam. Commonly, and especially where the fuel cell is designed for use in portable equipment, hydrogen is not used as the fuel because other substances are more easily and safely handled. Instead, various chemical compounds that are a source of hydrogen – often methanol or a hydrocarbon such a liquefied butane – are used instead.

The amount of heat that can be generated by burning the butane gas that’s often used in space heaters and barbecues is testimony to the energy that’s locked away in its chemical bonds. In fact the energy density of many hydrocarbons can be twenty times that of today’s lithium ion cells so the benefit of being able to use this technology for powering mobile devices is huge. Despite all this, fuel cells remain elusive as a power source for electronic equipment, although a pending product launch provides a glimpse of what the future may hold.

Lilliputian Systems will shortly start to ship Nectar 3.0, the latest incarnation of its fuel cell-based portable power source, which is intended to recharge batteries in mobile electronic equipment, via their USB ports, without access to mains power. It’s fairly compact, weights 200g, and can supply 55 Watt hours per cartridge which, the company claims, is sufficient to charge a typical smartphone ten times. The hot-swappable fuel cartridges, or pods as they call them, weigh just 35g. Unfortunately, this level of convenience doesn’t come cheap. The basic unit is priced at US$299 with cartridges coming in at US$10 each.

^Lilliputian Systems’ Nectar 3 promises almost unlimited power but at a cost

If a portable fuel cell-based power source is good, having the fuel cell built into the equipment is surely better since you don’t have a separate box of tricks to carry around. Several companies including Toshiba and Panasonic have done just that, demonstrating various prototype laptops, some as long as eight years ago. With an internal fuel cell, power is supplied via a small plug-in fuel cartridge which provides plenty of power and, in so doing, will make larger screens, faster processors and many of the other benefits of desktops available to laptop users.

None of these became commercial products with cost and convenience being key issues, we all have a large, uninterrupted supply of electricity in our home, and having a device run off another fuel source would probably require us to maintain a supply of it. It remains to be seen whether these obstacles can be overcome and this 176 year old technology eventually becomes the ultimate enabler of the 21st century’s love affair with ubiquitous electronics.

Generate your Own Energy

The most common method of generating a small amount of electrical power on the move is via a hand-cranked generator with dozens of companies now having jumped on the bandwagon. This approach was first adopted by Trevor Baylis, of wind-up radio fame, and his company Freeplay are still major players in the market. Their Freecharge 12V is one of the more universal wind-up chargers available. In generating power at 12V you can charge any equipment for which you have an adapter for a car cigarette lighter socket, and are not restricted to USB-powered gear. Realistically, though, it’s only practical to use it with smartphones and similar small items of electronic gear as you’d have to wind forever to power a laptop for more than the odd minute. A few years ago Freeplay had a pedal-powered charger for use with more power-hungry equipment but, presumably, most people weren’t prepared to have a good workout just to inject enough energy for five minutes of operation into a laptop battery.

^The Freecharge 12V will allows you to power just about anything by cranking its handle

Hand cranking and pedalling aren’t the only technologies for producing human-generated power but all methods tend to involve carrying out some repetitive action, often for a protracted period of time. Shaking is another option although, to date, this has tended to be used as the power source of battery-less LED torches as opposed to charging separate electronic gear. Torches that require a handle to be squeezed periodically are also available.

Charging on the Go

Already you can buy solar cells to power your hand-held devices but, realistically, these are never going to be particularly effective with typical British weather. There are also devices that will turn a modest amount of shaking or cranking into electrical power for emergency use but scientists are also looking for ways to keep your gear charged up, without access to a power socket, and with no deliberate action on your part.

Just walking around is an inefficient process because a lot of the energy we use doesn’t translate to forward motion. Acoustic energy is lost as the click of our footsteps on the pavement, for example, and no doubt we heat up the ground just by pounding it with our feet. These might sound like infinitesimally small losses but, even so, scientists are finding ways of harnessing some of the energy we waste in walking to power our electronic gear.

Of the many techniques that have been used, one of the latest employs the effect that gives us static shocks in hot and dry weather. Called the triboleteric effect, this process generates a static charge when two dissimilar materials – for example our hands and a cat’s coat – rub against each other.

What Professor Zhong Lin Wang and his team at the Georgia Institute of Technology have done is to arrange for two sheets of material rub against each other as a result of walking. While, initially, only minute amounts of energy could be produced, by using nano materials the area of contact between the two sheets was increased 1,000-fold leading to the potential of 33W per square metre. Keeping a smartphone’s battery constantly topped up is, therefore, entirely feasible.

^Using the triboelectric effect, researchers at Georgia Tech have salvaged the energy lost in walking

Ann Makosinski, a 15-year old student from Victorian Vancouver, has used a different method to provide battery-less power to a torch with the potential for powering other electronic kit. The development, which gained her a prize in Google’s annual international science fair, generates electrical energy from body heat. Her device uses Peltier tiles which produce power from the temperature difference between one side of the tiles, which is in contact with the user’s hand, and the other side which is in contact with the air. At present it generates a fairly small 24 lumens, but work is being done to improve this into the hundreds.

^Makosinski’s award-winning torch generates power from body heat

The Outer Limits

While we’ve been looking at the main contenders for future battery technology, there are some more unusual research projects that are worth a mention; as seemingly off-the-wall developments do occasionally make huge breakthroughs.

Take, for example, researchers at Virginia Tech who have created a battery that generates electrical energy from sugar using a chemical reaction that parallels the way living organisms obtain energy from food. Their creation is a type of fuel cell, so it’s charged by adding a cartridge of sugar whenever its power output dwindles but, as its inventors point out, unlike the fuels used in other fuel cells, sugar is neither explosive nor flammable. An energy density ten times greater than today’s best batteries is claimed.

Going one further, in that they use real living organisms rather than just mimicking their chemical behaviour, scientists at the University of Newcastle have turned their attention to generating energy from bacteria. The team have created a microbial fuel cell that uses the Bacillus stratosphericus bacteria which is found in large quantities 30km above the Earth’s surface but, for this application, was extracted from the Wear Estuary. However, it’s rather early to get your hopes up about the possibility of a bacterial-powered tablet. Although the University has doubled the energy density previous available from microbial fuel cells, 200mW per cubic metre isn’t exactly huge. We can imagine that having to carry the fuel cell in a large backpack wouldn’t be too popular.

Another unlikely sounding possibility is a battery made out of cloth and a specially formulated ink but this is exactly what scientists at Stanford University have been fine tuning for several years. The batteries can store about three times more energy than ordinary lithium ion cells but this isn’t the main benefit on offer. Instead, its developers say that it will be key to the up-and-coming wearable electronics revolution. So cloth batteries won’t be produced as components in their own right but will be printed onto garments, alongside other printable electronic components. The batteries can be printed in any colour, they can be washed, and they’ll even continue to work if stretched to twice their original length.

^Scientists a Stanford University have used special ink to print batteries onto fabric

No End in Sight

While lithium-ion technology represents a huge improvement over earlier generations of batteries, indications suggest that we’re still a long way from the theoretical limits of portable power. Coupled with the massive enhancements we’ve seen in the electrical efficiency of processors in recent years –and with further gains pretty much assured – the mobile revolution shows no signs of running out of steam. So are we going to see smartphones lasting a week on a single charge in the next decade? Surely only the brave would bet against such an eventuality.