| Tokyo’s Plugless Plug-in Hybrid Bus |
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| Written by Joshua Liberles | |||||||||||
| Wednesday, 05 March 2008 | |||||||||||
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From Asahi.com:
Charging a large amount of electricity quickly without using cords enables the bus to provide longer distance services. For the next two weeks, it will link Haneda's first, second and international terminals three times in the morning and again in the afternoon, covering a distance of about 4.2 kilometers. Since the bus uses only electricity, carbon dioxide emissions are reduced by about 60 percent compared with regular buses. Thanks to AutoblogGreen for doing the grunt work and deciphering some of the Japanese explanation of how the charging system works. From AutoblogGreen:
Now, about that cordless charging. Apparently it is using an electromagnetic inductive charging setup. There is a coil on the bottom of the bus and also one embedded in concrete. The efficiency and speed of the charging system is not stated and I couldn't tell whether or not it employs magnetically coupled resonance. That’s some cool tech that allows mass transit to run on established roads (with chargers added in) but performs similarly to an electric rail. Seems to me that a fully-electric, rather than a hybrid model, shouldn’t be such a big leap. See also: More Hybrid Buses Hit the Road, Pick Up Speed Via AutoblogGreen.
Comments (5)
Nick
said:
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The only problem is how efficient is this sort of power transfer system? I would imagine a lot of energy would be lost. No thanks, lets go with overhead wires or a third rail or something a little more efficient. |
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Let's not judge this thing before we know about energy efficiency. Is anybody able to give more information on this subject? |
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I studied engineering during my undergrad and learned quite a bit about physics, especially with relation to how this sort of system would work. There will always be power transmission loss, even over a wire. But the loss over a wire will probably be orders of magnitude less than the power lost via wireless transmission. One way to think of it is 'How much of the transmitted power will be caught by the receiver?' The problem is that with wireless, a lot of the transmitted electromagnetic power will MISS the receiver. This is power that is completely lost and will not be used to move the bus forward. While there are ways to make the wireless transfer more direct, the amount lost will still be greater than if they used a direct connection (like overhead wires). I'm sure we will continually improve the efficiency of this wireless power transfer method, but it has a long way to go before it comes anywhere near the efficiency of a direct connection. And I'm sure it will never be equal to the efficiency of a direct connection. |
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Really good insights, Nick. It's great that companies are looking to change to more efficient fuel sources but as you said, without looking at the whole picture (in this case power transmission efficiency) there's little point. Look at the biofuel / ethanol disasters we have brewing. Details are sketchy on this Japanese endeavor, but I look forward to more specifics. I wonder if, even with inefficient transmission, it could still be significantly better than diesel? |
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Why don't we just use trolleybuses? They're a proven technology that is probably far more efficient than the "wireless" recharging system. |
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