Safe Speed Forums

I realise this only is an "urban" leccy car, but there might be a safety issue on certain types of road.

Should we allow cars which are only capable of "up to 50mph", which I read as 'typically 45mph' (and headwinds will reduce that further), onto roads like motorways, where they would be going significantly slower than the massive trucks?

Note: the ultracapacitors will be giving out around 20KW when accelerating, so acceleration isn't limited by the 6kw fuel cell


An aside: this is something I gleaned from the comments section of that webpage:

Is there any truth in this?

Oddly enough, such slow cars disrupting motorway traffic flow (especially the trucks) would likely cause more CO2 than the cars themselves would save...sorry, displace!

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

I'm not sure why the 50mph limit ?.... My experience with electric vehicles suggests they are more often than not limited (accel or speed) wise by a) the weight of the batteries and b) the need to preserve the battery life... for a fuel cell vehicle none of the above applies

Certainly one of our customers wanted to put a stripped down, delimited version of a very unlikely vehicle round the nurburgring to demonstrate what it was capable of.




Yes.. this is already a large scale industrial process used to create hydrogen for other purposes.
Hard to comment whether the actual CO2 output is more or less overall and i don't have any figures to hand but hydrogen production aside the efficiency of the fuel cell and elec drives is likely to be alot better than a combustion engine.

I'm looking at an article on my desk at the moment that has calculated C02 emissions per km for electric vehicles, and it varies wildly depending on the energy mix used for charging (from 0 g/km for 100% nuclear/renewable to 122 g/km for coal generation, diesel & petrol vehicles stated as 99 & 108 respectively)

So crunching the numbers is by no meand straightforward.

It would cause great havoc if the HGV,s need to overtake 50 mph cars. They should be able to achieve 56mph min up a 1:20 gradient.

on the other side ... knackered horse boxes, old landrovers and 125cc bikes are allowed on motorways

not to mention caravans

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Speed limit sign radio interview. TV Snap Unhappy
“It has never been the rule in this country – I hope it never will be - that suspected criminal offences must automatically be the subject of prosecution” He added that there should be a prosecution: “wherever it appears that the offence or the circumstances of its commission is or are of such a character that a prosecution in respect thereof is required in the public interest”
This approach has been endorsed by Attorney General ever since 1951. CPS Code

It seems that's related to the maximum power output of the fuel cell; 6KW is about 8bhp (excluding motor losses), then there's transmission losses. Perhaps the real question is why the cell output is limited to 6KW. I suspect this is because the 4 motors are too small to be capable of handling more than 1.5kw continuously (the motors are within the wheels).


Thanks Ed.


I don't disagree, but this leccy car seems to require hydrogen refills, so I think electrical recharging may not be relevant.

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Is this a design requirement for loaded HGVs?

A 315+80KG load on a 1:20 gradient at 45mph needs 4kw - that's half the fuel cell power output before any electrical/motor/mechanical/drag losses or additional weight (passengers) are considered (let alone lights and heaters). This thing might struggle to exceed 30 with that gradient That cannot be safe! Surely that's a speed for plod pulling?


You probably can't legislate against old clapped out vehicles going slower than their design speed. What's nominal top speed of a 125cc?

Caravanners aren't liked no matter where they go

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

Time for a minimum speed limit on the motorways? I have travelled on American freeways where there is a minimum speed of 50mph on all but the inside lane. (And yes I know how that would play with the "Speed Kills" brigade )

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

yes.. i realise that sorry... what i was thinking was even if you generate by electrolysis you need electricity and the source of that electricity would have a big impact on the overall carbon cost of the hydrogen.
(one of the things hydrogen has going for it is that even if generated in this way you don't get transmission losses from distribution on the grid... although i guess you get some carbon from transporting it.. ho hum)

website seems to be here..
http://www.riversimple.com/Default.aspx

little technical detail.... i need to get at my notes back at work to revise power density for fuel cells vs batteries

Hydrogen does provide a convenient way of storing "electricity". Produce it by electrolysis using unreliable wind power and burn it in automobile fuel cells.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

Absolutely! I feel exactly the same way. Plant a big nest of hydrogen tanks round all these offshore windmills and then you don't have to mess about with unreliable power outputs - just leave them to electrolyse the seawater that they're stood in (of which we keep getting told we have too much anyway!) and pipe the hydrogen ashore. I can see that system working much better than trying to feed the national grid! SAme with tidal barrages - get them to electrolyse the water that they happen to be located near.

Interesting points on the slow car though. It's one of the scariest aspects of the current speed limit reduction fad sweeping the nation. The LAST thing we want is another incentive / excuse for them to drop speed limits all over the road network to (a) further discourage conventional car use and (b) ENcourage the use of under-powered eco-cars!

Not sure the hub motor power is the limiting thing - you can get 200kW hub motors. 4 of them should get it going quite nicely! I think it's more the cost of the fuel cell to keep them fed and the size of the hydrogen tank needed to feed the bigger fuel cell.

No way - seriously? That amount of power transfer within such a small volume (within a wheel)?
(I'm assuming that's without the use of superconductors)

I wanted this to be about the safety aspect, but I feel myself being drawn more to the technical aspects <geek>

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

That'll teach me to get my facts right before quoting something! I was told this by someone in the industry and didn't think to question it at the time. In retrospect, he may have been talking bhp rather than kW - although even then, a quick Google doesn't reveal anything quite that powerful.

Best I've been able to find is this:

http://www.lightningcarcompany.co.uk/home.php

which has a 120kW "pancake" motor in each wheel.

Still, 4 lots of 120kW (and obscene torque!) ought to make for reasonable progress!

Apologies for misleading - am updating my CV and sending it off to my local SCP as I speak! (reckon the job's in the bag )!

Please gawd no

I don't think you misled, at least not by significant amount anyway. A 120kw motor within a wheel is still a big leap for me. I could believe it if that was the rated surge power (as opposed to continuous) which I think is reasonable - like a loudspeaker's PMPO rating. It is limited to 130mph, quite low for 700HP plant.
Now I think about it, those motors could be cooled using a externally coupled coolant system, so the power rating of the Lightning's motors may not be unreasonable after all.

It still could be that the cheap 'n' nastier Riversimple Urban Car's wheel motors are limited to bog all continuous power, especially as it is unlikely to have such a coolant system. It could of course all be due to a crappy fuel cell.....

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

An average 125 4-stroke.


Cooling wheel-hub motors on stored-hydrogen-fuel-cell vehicles: Route the fuel through the wheel hubs ?

Using local water for electrolysis with offshore/tidal waters generating plant: What happens when you use electrolysis on salt water ?



Along with sodium hydroxide (weak)

Hydrogen is better (and more cheaply) produced by the breakdown of methane (Steam Methane Reforming ) where the redundant gas is carbon monoxide (also flammable) which is further reduced to carbon dioxide in another process.
Although there are several processes being researched (and used) to produce hydrogen by bacterial action...

http://www.fuelcells.org/info/charts/carchart.pdf

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The world runs on oil, period. No other substance can compete when it comes to energy density, flexibility, ease of handling, ease of transportation. If oil didn’t exist we would have to invent it.”

56 years after it was decided it was needed, the Bedford Bypass is nearing completion. The last single carriageway length of it.We have the most photogenic mayor though, always being photographed doing nothing

Add to that the drivers that can't/won't keep up with the flow .Someone said you can't legislate against it - why not -a simple MINIMUM limit for vehicles under a set GVW would work wonders ( and with the subsequent addition of minimum speed cameras ) -just think how much extra cash old Gordo could rake in .-Suprised it hasent been thought of already

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

just a technical aside for tony... these are probably all slightly out of date... and I dont have as much / as complete data as I thought:

Specific Energy:
Lead Acid - 35 Wh/kg
NimH - 45-70 Wh/kg
Li-Ion - 120 Wh/kg
Hydrogen @ 70MPa (type IV) - 1600 Wh/kg

Power Density:
NimH - 1-1.8 Kw/kg

I can't find a good comparison for fuel cell specific energy (or even enrgy density.. i.e. by volume)


Also some indicative costs for hydrogen generations:
Water electrolysis from wind : 0.32 US$/kWh (no source for this so not sure if this is capital costs or what?)
Water electrolysis from grid : 0.1 US$/kWh
Methane steam reforming of LNG: 0.04 US$/kWh
Methane steam reforming of natural gas: 0.01 US$/kWh

Interesting that generating hydrogen the CO2 emissive way is ten times cheaper than doing it the 'green' (whatever that means) way. I wonder which one is the method of choice?

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

i assume partly because this is the most developed volume process.... as discussed a little further up.

i'm a little suspicious at the wind cost as obviously the actual power used is free, which means capital costs may be spread over life of the turbine and assumptions made about efficiency etc ?