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Publisher's Letter

Your future electric car may use ultracapacitors

As it says in one of the letters in Mailbag this month, electric cars are coming. Or at the very least, they are coming closer. A recent issue of The Wall Street Journal reported that General Motors and Toyota are now punting on electric cars rather than hydrogen power. Good thing too. We have always thought that fuel cells and hydrogen were a distraction from the main game because fuel cells are very expensive and the distribution and storage of hydrogen was always going to be a major problem.

Part of the change of heart has come about due to recent advances in Lithium-ion batteries whereby future electric cars might have a range of up to 500km before they need to recharge. With a potential range of 500km, car makers will no longer be able to argue that people won’t buy electric cars because they cannot go far enough on a single charge.

At the same time, Nissan has just announced that it will release an electric car in 2010. Will it be along the same lines as the Nissan Mixim concept car? Probably not but you can be sure that it will use some of the same technology, with Lithium-ion batteries and a similar power-train. Mitsubishi has also indicated that it will sell an electric sports car.

GM will also release its Chevrolet Volt electric car but since it has a small on-board petrol generator to top up the battery for long drives, we don’t think it is a full-on electric car – it’s a "pretend" one. It is really just a further refinement of hybrid electric vehicles like the Toyota Prius or Honda Civic. Why don’t they revisit the EVA-1 with Lithium-ion batteries?

However, the latest really interesting development is highlighted with the article on ultracapacitors in this issue (page 12). In themselves, ultra-capacitors are mind-boggling because of the sheer values of capacitance now being achieved. Years ago, the standard unit of capacitance, the Farad, was always regarded as an academic curiosity, something that would never be a practical device. Yet we are now talking about capacitances of 1000 Farads and huge energy storage.

For anyone who has played with a typical supercapacitor over the last few years, this is an amazing shift. For example, if you have tested how much energy can be stored in a 1 Farad 5.5V supercapacitor (15 Joules), you will know that it is fine for lighting LEDs and powering low-current circuits but compared to a couple of NiMH AA cells, it is like the proverbial 110 pound weakling on the beach! (Oh, and before the metric thought police come to take me away in shackles, is there a better comparison?)

So it is even more amazing just how much energy can now be stored in banks of ultracapacitors. We are now talking about the same amount of energy as would be required for a practical electric car – 30 kilowatt-hours or more. This could be used on its own or combined with a large rechargeable battery bank. Ultracapacitors are even being tried out in electric buses. And it turns out that our very own CSIRO has been researching this area for quite a few years, as reported in our story in this issue.

So the developments are coming thick and fast. In fact, next month we will be reviewing the first really practical electric vehicle for consumer use. It is already available in Australia and they are selling fast.

Leo Simpson

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