Hydrogen fuelled cars: good idea in theory

[swansont]

You have to consider the weight of the fuel cell in addition to the hydrogen, and storing anything under pressure has its own set of safety challenges, compounded by the various types of damage hydrogen does to metals

[if_u_say_so]

Ok i figured something out. If you have 1 mole of hydrogen gas, that would weigh 1 gram and you could get around 100,000 coulombs out of it at 1.2volts (i think). 100,000 coulombs would be the same as having a 27.78 Ah 1.2volt battery, which would weigh something like 500g.

 

The equipment needed to store and convert the hydrogen and oxygen into electrical current could weigh up to 20kg which would be the same as having 40 batteries. But the thing is that if you want more energy, you can store a lot of hydrogen with 20kg equipment, but if you want to have more energy from batteries, each battery will take you up another 500grams. So it would be better to use a fuel cell for a project than a tonne of batteries.

 

Now i think i just made a terrible fool out of myself by posting all this, and i could be completly wrong with my estimates and calculations. Could someone please let me know if I should go back to school and re learn chemistry and physics?

[Peter_Pan]

You have to consider the weight of the fuel cell in addition to the hydrogen, and storing anything under pressure has its own set of safety challenges, compounded by the various types of damage hydrogen does to metals

 

 

Thats another down side of using Hydrogen, the safety concerns of storing it. I wouldn’t feel safe driving around with high pressure Hydrogen under my seat its like driving around with a bomb. Petrol is highly flammable but not explosive unless under pressure or in mist form. Just think every time there was car fire or crash they would need to evacuate the a large area.

[Cap'n Refsmmat]

No, because hydrogen is lighter than air, so it would dissipate incredibly quickly.

[Peter_Pan]

what would you do then release all the gas as soon as you crash and hope it will all dissipate. That’s fine if there isn’t any forms of ignition anywhere near to the cylinder. If there is you could end up with one hell of a blow torch.

[Cap'n Refsmmat]

Yes, and that's much better than a fireball from the gasoline, because it tends to point straight upwards and go away from everything else.

 

If there's a hydrogen leak, it'll just go straight up. It doesn't tend to hang around waiting for a match.

[insane_alien]

hydrogen(pure at any rate) is quite safe, even if you light it. think about the hindenburg. a heck of a lot more hydrogen (that even had some oxygen in it which makes it more explosive) did just blow up and take out 3 square miles/ it burned slowly shedding fire balls upward as the hydrogen bags burst. it was actually quite a safe combustion(if you convieniently forget the people strapped to the underside of it and those jumping to their deaths.) i would feel more comfortable with a tank of hydrogen than a tank of petrol

[swansont]

One should also note that the people in the Hindenberg who burned did so from the fuel, not the Hydrogen. The flames one sees in the pictures is from the skin burning or the fuel; hydrogen burns with a colorless flame.

[Ndi]

think about the hindenburg [...]it burned slowly

 

It wasn't under pressure. Natural gas also burns controllably until a pressurised container ruptures and kaboom.

 

I agree it's safer for an outdoor leak, but a more serious rupture that would expel a decent quantity of hydrogen into the air is bound to obtain the right mix at some point.

 

On one hand, gasoline is easier to contain; we have multiple layers, plastic, flexible rubber protections that hold the liquid in even if a tank is squashed. On the other hand, much more attention is given to a hydrogen tank than a normal gasoline one. Especially if you design a car around it.

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Anyway, back on thread, I believe the best (if not only) way we'd switch to hydrogen is if a cheap enough mix can be pumped into normal gasoline engine, LPG style. It WOULD grow into the market, just as LPG did. Out here LPG is quite popular, people retrofit such devices to normal cars, there are authorised companies that do the conversions and the option is available from factories to most if not all cars. And the only driving factor is price.

 

The switch to hydrogen site announces 10.000$ for a kit. For a quick and dirty evaluation, 10.000$ buys some 10.000 litres of gas, and with an average 10l/100Km (typical non-US average consumption sedan), it's approximately 100.000 Km worth of gas. Even if it was 100% free of any charges for ever (never breaks, never fills), not many people drive that many Km in a single car. It would also defeat the purpose of building a small, cheap, efficient town car if you plan on 300% price.

 

Double that for diesel (5l/100Km). Out here you can retrofit an LPG system for 300E.

[stormfish]

unfortunately the only place in the world that hydrogen fueled cars is feassable is in iceland, with their abundance of geothermal energy. it costs almost half again the energy to produce a litre of hydrogen fuel as you would ever get out of it. plus the fact that to compress hydrogen fuel enough to prevent re fueling every fifteen minutes worth of driving, it would have to be pressurized to 10000lb/sq inch. not a safe pressure by any standard. solar panels and wind turbines could theoretically produce enough hydrogen to power cars, they are, as of yet, too unreliable and slow to be of much help.

[swansont]

unfortunately the only place in the world that hydrogen fueled cars is feassable is in iceland, with their abundance of geothermal energy. it costs almost half again the energy to produce a litre of hydrogen fuel as you would ever get out of it. plus the fact that to compress hydrogen fuel enough to prevent re fueling every fifteen minutes worth of driving, it would have to be pressurized to 10000lb/sq inch. not a safe pressure by any standard. solar panels and wind turbines could theoretically produce enough hydrogen to power cars, they are, as of yet, too unreliable and slow to be of much help.

 

That's the case currently, but unlike many governments, we are looking ahead past the next election. As fossil fuel prices increase, alternative sources will become economical. It's prudent to research them before they are required.

 

Some fuel cell technologies can be run in reverse. If they become reasonably efficient at this, then hydrogen could be used as a storage medium for variable/unreliable sources such as wind power. Metal hydrides have already been mentioned. That, an improvement on that, or some new method (as yet undiscovered/unperfected), would likely be used, preferable to high pressure storage.

[insane_alien]

IIRC the metal hydride method has an equilibrium at a few(4-7 ish) bar. substantially less that the standard commercial tank pressures of 300 bar. also it stores hydrogen more effectively than pressurisation. still, i'd be happier with a tank full of 300bar H2 than petrol. hydrogen doesn't stick around near the ground.

[Corillian]

To extract hydrogen from water uses electrolysis. To extract it, you use less energy than you get out from burning oxygen and hydrogen back together again, so why don't we use some of the kinetic energy made by the engine to recharge the battery to keep the process continuous. Also, you wouldn't need to refill it, because its reactants are hydrogen and oxygen (water), and in the end, you get water as a product, so its renewable. Even if the kinetic idea doesn't work, you could use small solar panels to get the energy you need for the electrolysis.

 

If I am wrong please tell my why and how i can correct myself.

[insane_alien]

it takes exactly the amount of energy to break the molecule apart as you get out of it when you burn the hydrogen and oxygen. due to losses you'll find it actually takes a LOT more to get the hydrogen/oxygen mix than you get out of it.

[Corillian]

Okay. Thankyou for setting me straight. Now i have to go and tell my chemistry teacher that.

 

Does that mean that hydrogen cars aren't really renewable because you need the energy for electrolysis, probably from fossil fuels so its not really a great option for the future.

[insane_alien]

well, they are renewable in the sense that we can recover the hydrogen and oxygen again. just need to get power from another source. it IS a good option though. we can use solar, or nuclear or wind or whatever to get the hydrogen back.

[Corillian]

What othe clean source do we have, wind to power cars? not practical, mini nuclear power plants? not practical and dangerous, Solar Panels? damage could stop car, only really usuable in sunny enviroments.

Oil wil run out eventually, so we may have to use a mixture of all sources?

[insane_alien]

mini nuclear power plants? not practical and dangerous

 

only if its fission. besides i meant all those as source of electricity for making hydrogen for fuel cells, or just to charge up batteries

[Corillian]

I know, im sorry i probably didn't explain it properly, i meant that they couldn't work individully, so a combination may be the best idea. Or maybe none of them at all, we might discover and new source or way of extracting a source never found before

[Peter_Pan]

What othe clean source do we have, wind to power cars? not practical, mini nuclear power plants? not practical and dangerous, Solar Panels? damage could stop car, only really usuable in sunny enviroments.

Oil wil run out eventually, so we may have to use a mixture of all sources?

 

 

We have Bio fuels which normal engines will run on, Things like vegetable oil, alcohol.

[Corillian]

Which produce emissions that "hurt" the planet

[insane_alien]

corillian, biofuels also absorb a lot of CO2 in their production. to make them(globably) we would require vast tracts of photosynthetic bio matter. the same stuff that absorbs CO2 and pumps out O2.

[Corillian]

they can still "hurt" the planet before they are used in the creation of new bio fuel plants. I suppose they are alright, but at the rate global warming is happening, the climate may become to hot for them to grow, is this true?

[insane_alien]

1/ plants like heat, why do you think greenhouses are used a lot.

 

2/global warming does not necessarily mean that everywhere will heat up, the UK for example is predicted to cool down, a lot.

 

3/global warming will also lead to increased humidity, plants like this.

[Corillian]

So basically global warming is good for plants

Apart from the fact the melting ice caps are likely to melt enough to destroy a large amount of the worlds animal and plant life.