Electric cars

[SilentDeath]

Thats not the point. Your assuming that normal cars are efficient. the engine, when running in best ideal ocnditions, is only 30% efficient.. but town driving I guess its about 10%.

So heres some numbers... Tesla roadster, as mentioned above, only has 55kW/HOUR of batterys. That is, after an hour at 55kW, the battery is DEAD. The motors are 185kW, in total. so if they are on full, you only have 15 minutes... can it do 217 miles in 15 minutes?...no they dont run on full except when accelerating.

Yet it can do 0-60 in 4 seconds. So our 15 minute batterys can do 225x 0-60 launches..

So you have a small higly tuned engine, always running at the most fuel efficient rpm, just to keep those 55kW of batterys topped up.

So the question is, how flawed is the tesla design... will the batterys be dead in 15 minutes if you drive it fast?!?


but, we dont need 0-60 in 4 seconds.. thats a bit OTT for me..and we are going to drive more resonably... so lets say our 185kW motor was really 75kW - 100 horseys (4x 18.5kW motors - one for each wheel), with a 30kW 234cc honda engine under the bonnet. We keep 30kW/H of those batterys, saving enough wieght (from the 55kW batterys) to put the tiny engine in..

[usxhe190]

i am not saying you are wrong but just highlighting some issues - for example...even the tesla isn't production ready yet? they are still testing...only a prototype

the only people who has successfully used a battery engine is toyota and those guys are smart so i would have thought they would think it through if it works the other way around (i.e. electric bigger than petrol)?

[kalniel]

I don't see how going from chemical->mechanical->induction->chemical->electrical->mechanical is going to be more efficient than chemical->mechanical, even if several of those stages are quite efficient.

The only reason trains/shuttle carriers do it that way is because they can't design a clutch that's capable of working with that much power/weight. Electricity is easy to manage.

As inefficient as they are, you can't make them more efficient by saying you're using the same diesel to power a generator instead of the wheels.

The only way electric cars can be more efficient than diesel is if you have a way of charging them that's *far* more efficient than a diesel engine (for the same amount of power). Hence regenerative braking, fuel cells etc. etc.

[Lee H]

Are they making these cars to produce excess noise?

The reason I'm asking is that electric motors are going to be quieter than a normal combustion engine and if the cars are quieter I forsee more people getting hit by them especially at night.

[Zak33]

Slightly different. Trains are heavy, like boats. They wieght 100x more than a car, without carraiges included.

Petrol engines are the uber ineficient. Converting battery energy into movement, using motors and such.. is about 90% efficient. The same goes for movement into electricity using a generator. Engines are far more efficient at a constant speed too.

200cc was a guess, but easly possible using a highly tuned bike engine. A larger engine would likely be more practicle.. 400-600cc...

chap...even if you were right, you've still lost 10% of the petrol power converting it...So you've wasted it.

Weight of car is irrelevent if you start looking at what people demand, ABS, airbags, alarms, central locking etc.

HOWEVER.....take that all aside. If you are going to convert petrol or diesel power into electricity, the one reason to do it, is that you need no clutch, no gear change and you use the electric motors for all of that.

Electric motors...which wear out. Faster than the petrol/diesel engine will.

Further..and you'l hate me for this: the electric car must be LIGHT to be efficient, and carrying a pertrol/diesel engine around, with the fuel tank, with theenegine management, and coolants, pumps, radiators etc...AND it needing some electricity to run.....well....I think it may fail

[Zak33]

The only reason trains/shuttle carriers do it that way is because they can't design a clutch that's capable of working with that much power/weight. Electricity is easy to manage.

beauuuutifully worded

[dkmech]

The advantage of fuel cells is that unlike batteries they can be charged back up to capacity in minutes. And while there is no infrastructure at the moment you may want to remember that there used to be no petrol stations at all relatively recently. The amount of amazing engineering and economical challenges that were overcome in the past amazes me. And the amount of new stuff people shy away from because "it will need stuff doing to make it work" sickens me.

It may be my engineering education but surelly we didn't get where we are (melting the penguins and polar bears ) without facing challenges and overcoming them.

[SilentDeath]

But in that case, why dont we just burn pure hydrogen in our engines. It is quite well suited to burning in engines.... those designed/modified for it ofcourse....

Dont know if its as efficient as fuel cells, but I can bet it is a lot less expensive. However we still have the infrustructure problems surrounding it.

We could even have my above idea, powered by...





A HYRDROGEN ENGINE!!!



Note that I really dont like the idea of batterys...heavy expensive... slow.. not reliable... the above idea could probably work quite well using hydrogen for energy storage. Using wasted engergy to electrolosice hydrogen back into the tank... but thats maybe a bit too far...

[Dreaming]

Maybe they're worried about hydrogen being so extremely volatile if a car has a crash it's gonna blow up lol. Not that petrol isn't extremely volatile - but it's petrol fumes that are so it tends to have to evaporate first - doesn't take that long but hydrogen it will just go supernova on you.

[mallett]

Maybe they're worried about hydrogen being so extremely volatile if a car has a crash it's gonna blow up lol. Not that petrol isn't extremely volatile - but it's petrol fumes that are so it tends to have to evaporate first - doesn't take that long but hydrogen it will just go supernova on you.

That’s not entirely true. Hydrogen is in fact safer then petrol in SOME ways, and the hydrogen storage systems that have to be used on cars are extremely safe and with all the redundancies that are built into the tanks, there is less of a chance of explosion from a crash then with conventional fuel.

But in that case, why dont we just burn pure hydrogen in our engines. It is quite well suited to burning in engines.... those designed/modified for it ofcourse....

Dont know if its as efficient as fuel cells, but I can bet it is a lot less expensive. However we still have the infrustructure problems surrounding it.

I agree that this is the way forward over the next 20 or so years as engines are being built now that can run on both hydrogen and petrol and this is the way that hydrogen as a fuel will spread around the world. Hydrogen engines are also more efficient then petrol and diesel engines and have the potential to be more powerful, but they need more development before this happens. The BIG problem with hydrogen at the moment is the amount that can be stored on the car, despite, as someone said earlier, hydrogen having a higher kJ/kg then petrol and diesel it has a much lower density so can only be stored at huge pressure (around 700 bar at the moment) or at very low temps (about -260 C) for it to be feasible.

Just my 2 pence worth...

Oh and by the way I think I read somewhere that it will cost something like £5 trillion to add a hydrogen source to every service station around the world. That’s less than 1% of the total spending on defence worldwide, iirc.

[dkmech]

Thing about fuel cell cars is that you avoid so much weight. Hydrogen tank is bound to be lighter than a huge load of batteries. And the cell and electric motors will be lighter than an engine and drive train. I'd imagine fuel cells should be fairly efficient too.

I am also not sure how good hydrogen would be as a fuel in internal combustion engines as I am not up to speed on its properties. Remember that petrol isn't just something you squeeze out of oil - its quite a sophisticated blend in order to avoid detonation and so on. Some of the pollution questions would not be an issue for hydrogen but I'd imagine things aren't that simple.

[SilentDeath]

Have you ever moved a large compressed gas cylinder? Thats what hyrdrogen cars will probably end up using, ofcourse in a more car-friendly shape, but it will need to withstand very high pressures AND be safe in a crash, I guess a full one would likely wiegh 150kg or so..

Fuel cells are also quite heavy I think, and most current hydrogen cars will heavly rely on batterys.

Hydrogen has some very nice propertys for combustion.
clicky

[dkmech]

It'd probably be hefty, but a lot of the weight will be fuel too. If you tried moving an engine, gearbox, driveshafts and a full fuel tank I am sure it won't be particularly light either. I imagine a lot of hydrogen technology would be greatly improved with a bit of engineering on a big scale (although this may prohibit some of the fancier materials).

Thanks for the link on hydrogen, will have a read

[StevenF]

I think that eventually, it will be the way forward. At the moment, I can imagine electrical cars to be very, very slow, and no where near as much fun to drive. Interesting thread, I've enjoyed reading it

[Wh@l3fish]

At the moment, I can imagine electrical cars to be very, very slow,

Check out the Venturi Fetish! 0-60 in 4 secs is hardly slow....

In the stopgap between current engine technology and 'next gen' technology, there are a few things that would help fuel efficiency. One of themis KERS - Kinetic Energy Retrieval System. It basically uses a flywheel and regenerative braking to spin the flywheel. THe momentum in the flywheel can then help you get going again. Its due to appear in F1 in 2009, although not so much for fuel efficiency as providing extra 'oomph' for overtaking. I can't post links yet, but a company called XTrac is going to make them.

Also, a campany called Torotrak has 'inventented' a transmission system called 'IVT' - Infinitely Variable Transmission, which claims to improve fuel efficiency by 20%, while also improving performance. It has no 'gears' but rollers arranged in a toroid (or donut). You can be sitting on the motorway, with the engine just ticking over enough to keep the car moving. Don't now when it's likely to appear in mainstream cars though

[dkmech]

It's also called CVT by some manufacturers or variable ratio gearbox and has been on some cars for a while. One of the problems with it is that when you floor a car with cvt it can keep the revs the same and change the gear ration - which sounds odd as your car accelerates without changing the engine note.