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a new wave of hybrid electric-electric vehicles are going to arrive. you can read about them on the web.
instead of being battery powered only, where the regenerative breaking energy is stored back into the battery pack.
instead, the new designs ( look at eipc for instance ) are focussed around
restoring that regenerative breaking energy in supercapactors because they have almost no resistance and using that stored energy as a first reserve of energy for accelerating the vehicle ( for the same reason that there are less resistance losses drawing off a capacitor than a battery )
so now, because i've been noticing that bicycles are commonly being outfittied with electric hub motors, why not hook these up to super capacitors, which are light weight and idealy suited for bikes. PLUS.....if the super capacitor could store enough charge, perhaps the need for an electric battery to power the bike could be done away with entirely.
Off topic but related, very cool, and might augment this idea nicely.
http://reubenmiller...olar-ingenuity.html
[2 fries shy of a happy meal, Jun 25 2008]
[link]
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Sounds good to me, but what are the
details on supercapacitors? Cost? Energy
density? Charge leakage? Lifetime? |
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The last time I looked (and they are under feverish development), supercapacitors didn't have the same energy density as many types of batteries. However, they are very good for fast charge/discharge cycles which would be typical from braking and accelerating, as the OP noted. And, of course, that's exactly how they are used in electric vehicles already. |
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ultracaps are approximately 10x heavier and larger and more expensive than small LiFePO4 batteries that could serve the same purpose in a bicycle application. |
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the LiFePO4 batteries have almost perfect charge/discharge efficiency, so can actually absorb an amazing amount of charge, much like what you'd expect of a capacitor (in this application). they also have a cycle life such that you'd get about 8 years of using (discharge/charge) them 5 days a week! |
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another advantage of sticking with batteries, is that a capacitor's voltage varies depending on its state of charge, requiring another level of electronic complexity to handle that. |
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cars, having to deal with much higher bursts of current, could use an ultracap, and in fact are. i've read a few reports of ultracap/battery hybrid packs. makes sense. why torture your batteries when capacitors can level the loads. the expense may be justified in this case. |
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your last point: running a vehicle on caps alone really is the ultimate goal. a black-box that absorbs/provides tremendous amounts of energy as fast/slow as needed, can be recharged millions of times and is economical. i keep reading about a company called EEstor that claims to have such a device already developed. |
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One feature of electric bicycles is that you can reduce the amount of work you do period. Or not pedal at all (depending on juristiction). Batteries do that and regenerative braking too. |
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Ultracaps only do regenerative braking. They won't help you go uphill or do the work for you if you're tired/lazy. |
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I support the use of capacitors if they are good enough. They charge/discharge very quickly and I believe they give more of your energy back than a battery. But I think the battery is too good to not have on an electric bike until capacitors can hold more charge. |
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Why not have a solar panel on the bike? I bet it would collect far more energy than occasional regenerative braking. |
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Capacitors are an old but great idea. It has been implemented in lab but the old problem still remains, when you have a minor accident; the cyclist finds they're riding a “hot seat”. Damaged caps tend to discharge at the speed of plasma. |
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Regen is nice but it won't run the vehicle, it can only accelerate it partway back to the speed from which it decelerated the vehicle. In that capacity it can sharply reduce the engine requirements to operate the vehicle safely in traffic, but that's all. As to having enough power capacity to provide real-world range to operate a vehicle, ultracaps aren't there yet, though I keep hoping. |
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