Low Impact

With rising petrol costs, and the fact that a quarter of our carbon emissions are caused by transport, cutting back on car use makes a lot of sense. Bicycles are a great option. They’re quiet, emit no global warming emissions, and are much faster than walking!

But they do require muscle power. On the positive side, this means that as well as being a way to get around town, your trusty bike can save you your gym membership! But on the negative side, the effort required can make a bike ride daunting for the elderly, or when contemplating a longer trip.

Enter the electrical bicycle. An electric bike carries a battery and a motor. Typically the motor then provides “an assist”. That is, you still have to pedal, but the motor helps too, lessening the effort required to get up that hill. This means you can go even longer distances, without feeling tired.

Battery technology has been one area which has held back electric bikes – often lead-acid batteries have been used which are very heavy. Some of the gains you make in having the motor help are lost in carrying the battery around! The other issue is battery life. Moving a 14kg bike, with a 75kg person on top takes a bit of work, even when that person is helping on the pedals!

But things are improving. Lithium-Ion batteries are now making an appearance. These batteries are the same as what you find in your mobile phone and have the advantages of holding more charge, and being substantially lighter.

Something else I haven’t seen until recently is the introduction of regenerative brakes on bicycles.

This is something that’s commonplace in hybrid cars. Normally when you use the brakes on a car or a bicycle, pads press on the wheel or a disk connected to the wheel. The resultant friction slows the wheel down and produces waste heat. In a regenerative brake, an electric motor is engaged on the wheel, so that the wheel turns the motor. This effectively turns the motor into a generator – rather than taking power in and producing motion, it takes the motion of the wheel in and produces power. And, as a side effect of having to turn the motor, the wheel slows down.

The end effect of all this is that when you need to slow down, rather than take all that speed and convert it to unused heat, you can convert it to power which you can store in a battery and use later.

A few blog posts have appeared about Panasonic Japan’s recent announcement of a new electric bike, the Vivi RX-10S, featuring regenerative braking. Apparently, it will sell for about $1400 – a lot cheaper than a car, and even a fair bit cheaper than a fancy mountain bike! Normally a fully charged battery could assist the rider for about 90km, but with regenerative braking this increases by around 33% to 125km.

Panasonic aren’t the only player with this technology. Sanyo also has a contender (the “Enacle”) in the Japanese market, but with a smaller battery capacity – it can get you 35km without regenerative braking or 50km with.

I haven’t seen any indication of when or if these bikes will be sold outside of Japan. But as petrol prices go up, there’s sure to be a market for them. For me, the trusty, original pedal-powered version will do me just fine. But this is a great example of technology making it easier to choose a cleaner, greener alternative.

• Link to the Japanese language page on the Panasonic Vivi RX-10S
• Link to the Japanese language page on the Sanyo Enacle

Categories: energy, environment, green, transport

Tags: bicycle, cycling, transport