Blue Sky: Fuel Cells for Increasing Range?

MIKE

Just Joined
Oct 30, 2006
2
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fuel cells

Great idea I am all for it but surely it would be better for the fuel cell to work directly due to the fact that to use a power source to charge a battery to power the wheel leads to a waste of some of that power. What we want is the ability to swap power sources.
 

flecc

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Oct 25, 2006
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Although it's bikes that really should lead the way with this since they are the most burdened by battery weight, I think we'll probably have to wait until after the car manufacturers make a go of it. There are a number of trials running with hydrogen fuel cells, but the inevitable question is already being asked, where will the hydrogen come from? The only viable way for most countries to get enough electricity to produce the hydrogen without destroying the planet is nuclear power at present, and that's none too popular an option for many.

Of course methane can be used, but that brings it's own environmental problems, so the car manufacturers wouldn't go ahead if that's the only option available. Unless they can see enough fuel available to cope with cars by the million, they won't be able to manufacture cars economically enough for them to have a place in the market. The classic chicken and egg situation yet again, the more advanced we get, the more we hit this kind of impasse.
 

flecc

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Oct 25, 2006
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Query to Mike

Did you mean using the fuel, hydrogen of methane for example, directly in an engine? The fuel cell produces electricity so that would have to drive an electric motor. If you mean using the fuel directly without a fuel cell, then there's all the usual problems with internal combustion engines, although that's the only option on the horizon for jet aircraft once the age of oil passes.
 

flecc

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Oct 25, 2006
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P.s.

On second thoughts I think I've misread your posting Mike, you mean just leaving the battery out of the chain. Might work, but I don't know how responsive to current demands the chemical reaction of a cell is. It would need to respond as quick as we flick open a throttle.
 

mithril

Pedelecer
Oct 27, 2006
40
1
Clay Cross, Derbyshire
The up and coming Vectrix electric scooter (www.vectrix.com) is eventually going to have a fuel cell to battery to motor configuration apparently. I don't know if this is due to the responsiveness of the fuel cell vs battery as Flecc points out or if it is some trick to get around legislation i.e. if the battery drives the motor it's an electric bike with all the tax benefits, but if the fuel cell drives the motor it's a ... fuel cell bike with different legislation ?!?!?... just guessing really.
 

flecc

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Oct 25, 2006
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My reading of that legal puzzle is that using an unapproved power source to charge the battery that's driving the bike is still very definitely illegal. That's because it's impossible to stop any current from going direct to the motor, and at times of high demand that would definitely happen.

Oddly enough, even charging a spare battery while riding along is also technically illegal. Manufacturing on the public highway is apparently banned, and that includes making electricity! I remember when readymix concrete trucks first appeared very many years ago and breached the law, and a special order had to be passed to permit them to carry on. I don't know if that's still in force or whether legislation since then makes the provision. For some odd reason the issue of ice cream vans has never cropped up to my knowledge.
 

rsscott

Administrator
Staff member
Aug 17, 2006
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196
I've read that the BionX has the ability to recharge the battery when braking. I presume charging the primary source is ok or is this bike/kit illegal to use on British roads ?

Oddly enough, even charging a spare battery while riding along is also technically illegal. Manufacturing on the public highway is apparently banned, and that includes making electricity!
 

flecc

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Oct 25, 2006
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The BionX is legal since the regenerative power is only that which the bike put in the first place, and is later recovered by using the recovery as braking force. As such, it's got some parallel in turbo charging, where exhaust gases are used to generate extra power. In both cases the cycle is internalised. Of course the Bionex was originally a General motors design for the USA, or as it should be known, the USNA. :eek:
 

derrick7

Pedelecer
Aug 22, 2007
107
0
Llanberis LL55 4TD (Snowdonia)
Regenerative braking

The new Twists 1.0 & 2.0 can trickle charge the battery, that is when going downhill.
Does anyone know any other hub motor bike in which this is provided, you just press a little button on the handlebar control.
One of the first questions that people always ask me is "does it recharge when you go downhill?". I think they think I have got some form of perpetual motion machine!

Derrick - Llanberis
 

flecc

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Oct 25, 2006
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As far as I'm aware, only the BionX and the new Twists have this feature. The gains on bicycles are too small to be worthwhile, bikes not having enough mass and speed for anything worthwhile to be gained.

A to B were unable to detect any gain on the Twist I, despite having some good measuring equipment.

All too often on bikes the speed gathered downhill is useful for attacking the slope up the other side or travelling further without pedalling along the flat. If the downhill speed is held back by the regeneration as happens on the new Twist, the result is a net loss, since power conversion always loses efficiency.

Fortunately on the BionX the option to use it is switched and under rider control.
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Ian

Esteemed Pedelecer
Apr 1, 2007
1,333
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Leicester LE4, UK.
I used to have a Synergie electric bike that did charge the battery while coasting above a certain speed. The system did work and it was possible to recharge a completely flat battery sufficiently on a long downhill stretch to get some assistance on a following short uphill stretch. Unfortunately, in spite of its very low power motor the bike was so inefficient that even with this feature range was very limited, 8 miles on one particularly hilly journey that I remember. One serious disadvantage was the lack of a freewheel in the front hub motor, a necessary omission with any kind of regeneration meaning all pedalling had to overcome the very noticeable motor drag. As a consequence the bike was very hard work without power, even on the flat.
 

flecc

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Oct 25, 2006
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I understand the new Twist is the same Ian, permanent motor engagement, no disengagement option.
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flecc

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Oct 25, 2006
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Thanks for that Nick, very interesting.

Of course that's a much better application for regeneration, first because a Velomobile has much more mass to store kinetic energy, second because the streamlining improves the downhill speed so much.

A diamond frame upright bike is much less suitable, and I'd rather use the stored kinetic energy directly and avoid the very substantial energy conversion loss.

Mind you, I'd prefer that on a Velomobile too, 75 mph can be real fun! :eek:
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flecc

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Oct 25, 2006
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On the thread subject, those having rosy specs about hydrogen fuel cells might consider this extract:

"This means producing hydrogen from oil or, in the case of the hydrogen for London, from natural gas. So it's not quite the clean fuel that many imagine. Another problem is that hydrogen isn't cheap. In fact, it's far more expensive than diesel. Early results from the Madrid trials suggest that hydrogen buses cost around 4 euros (£2.80) a mile to run; that compares with a single-decker bus in London running on diesel for about 23p a mile."

Sounds ideal for running an e-bike for at least 12 times the cost. :rolleyes:
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Mussels

Esteemed Pedelecer
Jun 17, 2008
3,207
8
Crowborough
On the thread subject, those having rosy specs about hydrogen fuel cells might consider this extract:

"This means producing hydrogen from oil or, in the case of the hydrogen for London, from natural gas. So it's not quite the clean fuel that many imagine. Another problem is that hydrogen isn't cheap. In fact, it's far more expensive than diesel. Early results from the Madrid trials suggest that hydrogen buses cost around 4 euros (£2.80) a mile to run; that compares with a single-decker bus in London running on diesel for about 23p a mile."

Sounds ideal for running an e-bike for at least 12 times the cost. :rolleyes:
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If we take storage (battery or tank) cost into consideration then hydrogen may not be hugely more expensive and a tank lasts many years. Unfortunately I've never seen a lighweight HP tank. :(
 

flecc

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Oct 25, 2006
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If we take storage (battery or tank) cost into consideration then hydrogen may not be hugely more expensive and a tank lasts many years. Unfortunately I've never seen a lighweight HP tank. :(
Against batteries certainly Mussels, but against fossil fuels it doesn't stand a chance at present. We'll have to almost run out of oil before hydrogen competes on cost grounds, though we'll probably use it before on environmental grounds.

Hydrogen tanks certainly are large. There's been at least two hydrogen powered bike designs, the Aprilia and one private recumbent trike design and the tanks were rather too large on both.
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