Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: scotty234 on 11/05/2005 14:20:00
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OK, my knowledge of fuel cells is very limited, but I'll have a go.
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I never realy no how the engines work
There isn't an engine in the traditional sense... the hydrogen isn't burnt in the sense of being ignited by a spark, it's used in a fuel cell. Water can be electrolysed (split up by passing a current through it) to get hydrogen and oxygen, the fuel cell works backwards... H2 and O2 (from air) gases are at seperate electrodes but can be combined to make water, I think this involves loads of single steps involving H3O+ and/or OH- but essentially
2H2 + O2 --> 2H2O
The only product (at least in the vicinity of the car) is water (of course, they have to get the hydrogen from somewhere but even the current processes for getting it from hydrocarbons are more efficient than burning those hydrocarbons direct as fuel.
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what would happend if there was a leak
Well I guess if it was a big enough leak and there was a spark there'd be some sort of explosion. So the H2 tanks are going to have to be pretty strong (don't want rupture in the event of a crash.
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isn't hydrogen the main part in acids
Um, acids are acids because they have hydrogen atoms available for donation without their electron, but in order to make such a compound you need to react the hydrogen with something like chlorine (Cl2) to give HCl (hydrochloric acid) but then if there were those kinds of concentrations of chlorine about then a little HCl would be the least of your worries, I think.
Hydrogen is present in acids ...*H* is the reactive hydrogen, in CH3COOH, acetic acid (found in vinager) only the proton marked is acidic:
*H*2SO4
*H*Cl
*H*NO3
CH3COO*H*
But also in
H2O (water)
CH4 (methane)
C6H12O6 (glucose)
Which aren't acids at all.
And even OH-, NH3, which are bases.
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is this the way forward
I'd like to think so. It's a lot less dirty than hydrocarbons... no soot, no unburnt fuel, no CO2 (in the vicinity of the car, tho' some may be made in producing the hydrogen). The cars are much quieter, as they don't have an endless series of explosions going on inside them.
It depends on a way of making truly vast quantities of hydrogen becoming available of course. There are hopes (I think, and I think that's currently all they are) of finding a way of making H2 from plant matter instead of hydrocarbons from oil... which would be an enormously Good Thing as it would reduce our dependency on oil for (i) when it starts seriously to run out and becomes very expensive and/or (ii) the oil producing countries (Iraq, Saudi Arabia) decide they don't like the Western world and they aren't going to sell us fuel any more.
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If this did actually work it would be a massive step to stopping the use of fossil fuels, because, of course, we will run out reletivley soon. I think they wil always sell fuel to the western world though. I think they need the money and the relations too desparatly.
"There is no gravity, the earth just sucks"
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Fuel cells use hydrogen which doesn't exist in nature in its elemental form, so it has to be produced. One way to produce hydrogen is to use energy to electrolyse water. The fuel cell then recombines the hydrogen with oxygen to get the energy and water back. So fuel cells won't reduce our dependence on fossil fuels. We still need to get the energy from somewhere. Europe is pushing for generation of electricity using non-polluting means like solar, wind and geothermal. You could use these sources to make hydrogen.
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Hi Hades
I'm surprised that you say that hydrogen doesn't exist in nature in its elemental form - what about the sun ? That's burned up 5 billion year's worth of hydrogen so far !
Then there are hydrogen-yielding bacteria and algae - certain gut bacteria produce hydrogen which is why some people are able to set farts alight - it's not just methane as people often think.
Nice clear explanation though, thanks.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Yeah, well put, Hades...
that was what I meant, petrol or diesel have to come from oil reserves, many of which are in politically unstable areas and all of which are going to run out.
Hydrolysis of water to form hydrogen requires electricity, but this need not be generated by burning coal, oil or gas... it can come from solar, wind, tidal or wave power or, as I think is more likely, from nuclear fission.
There's not much hydrogen on earth as H2, and getting it from the sun might be tricky (anyway, it's not H2 there, is it? It's more like protons and electrons flying about). I'm not convinced we're going to be able to harvest enough farts to run our cars... the alternative technology is bio-fuels, probably methanol (from fermented crops grown to provide energy), which is basically an alternative way of using the sun's energy to provide fuel.
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I studied hydrogen fuel cell cars in University, as my profs believe hydrogen will power automobiles and homes in this century.
The hydrogen fuel cell is straightforward: the cell contains a catalyst and a semi-permiable membrane, and takes O2 and H2 as "fuels". Products are heat, electricity, and water vapour. One of these units in your home could provide you with heat, water, and electricity.
The problems with fuel cells right now are mostly with hydrogen: obtaining a purity that won't harm the catalyst, and from a source that won't use more energy than it provides.
The best sources for hydrogen include steam reformation of coal, natural gas conversion, and electrolysis of water. As you can see, there are problems with each of them -- two use fossil fuels, and the third uses electricity.
The other problem is building a container that will fit into your auto and provide a decent driving distance. Hydrogen tends to leak out of most containers, but a metal "sponge" has been used with success. The other problem is that hydrogen doesn't have the specific heat of gasoline, so that to provide a driving distance of 500 km, the fuel tank would be a third of the size of the car!
Another option is that fuel cells aren't restricted to hydrogen ... the catalyst and membrance can be tailor-made to react other gases.
Regardless, hydrogen fuel cells are seen as the 21st century's answer to providing a clean source of heat and electricity.
Canada's Ballard Energy has received a lot of funding from Ford Motors and Daimler-Chrysler to pursue fuel cells. They have installed a couple of them in city busses around Vanouver suburbs to demonstrate their technology.
Now, my information's a few years old, so hopefully some new breakthroughs have occured in the meanwhile.
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I think I heard a radio programme about a fortnight ago which featured someone test-driving a fuel cell powered car and describing it as almost indistinguishable from a standard petrol car except for the lack of noise and engine braking.
For UK based readers, I think it might have been one of the Top Gear team doing the testing.
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from a source that won't use more energy than it provides
It's always going to use more energy than it provides (thermodynamics!) but it's a case of maximising the effciency and using an appropriate source to produce the hydrogen.
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Hydrogen Fuel would make for a cleaner enviroment, it would not be a god-send for a new fuel or a new energy source. Hydrogen would need to be generated from some other energy source, and if you have ever met the Carno (sp) efficency equations, you know that hitting 30% efficency is very good. I.E. it takes more energy to produce hydrogen than you will ever get back.
That said, it would still be a good thing even if we used coal to make the hydrogen for one simple reason: we can afford to spend millions on a fixed facilty to scrub the pollutents where as we can't afford much more than a hundred dollors on each and every moving car or truck.
I personally like coal though it has a lot of problems. We can scrub out the sulfur, and new technology promises we can scrub out the mercury (my biggest worry). I am not sure about the residual radioactivity that some have reported, but there is a whole lot of coal laying around (300 years supply).
Even if we used oil to generate the hydrogen, due to the size of the plants, it would be possible to clean the emmissions of such a plant to a much higher level than we can clean the emmissions of cars.
All that said, there are still major obsticals to overcome, and in this world of crazies that like to blow things up, giving everyone a hydrogen gas torch (substitute the b word) may not be a great idea...
David
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Fascinating stuff, this. I do not have much training in the chemistry and physics of this topic, but there is a good book out on it entitled The hype about Hydrogen. As you might guess the author is critical of those who expect a quick panacea from this evolving technology. He makes the point that it is quite problematic to depend on "breakthroughs" because breakthroughs are not predictable- and sometimes just do not happen. Hydrogen tanks in a car would have to be under very high pressure to keep the hydrogen in a liquid- and that does raise the risk of explosions. How would you like to pump a super-cold substance into your vehicle every couple of days? Makes me nervous.
But the greater question is what problem does it solve. To me, it is not enough to just solve the "reliance on Arab oil" problem. An even bigger problem is the dreadful danger of climate change if we continue to derive power from fossil fuels due to the global warming process. Hydrogen derived from fossil fuel would do nothing to solve this problem, and might in fact give us a false sense of smugness that would discourage a real solution. You can burn scrubbed coal to manufacture hydrogen and have zero Sulphur emissions, but you will still have plenty of Carbon emissions.
It is noteworthy that we need oil to create plastics and other chemicals and that will be a good use for it after we stop putting it into vehicles and burning it up.
chris wiegard
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I had to watch a boring half an hour program on this in science ugrrr!
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The problem with carbon emmissions is that the poor countries of the world will not be denied the right to increase their standard of living. Hence parts of China look like the industralized Pittsburg of the late 1800's when the robber barons ran the show. We can clean up our act as much as we want, but the countries now industralizing will only pollute more to fill up our manufactoring gap.
Little dicodimy here: we raise the cost of manufactoring so much by insisting on clean manufactoring that the jobs are pushed to China where they cause much more pollution. We would have reduced pollution by allowing lower cleanliness standards here - duh. Likewise, clean California has exported its energy production to Mexico, and when the winds are right, the Mexican pollution comes right back into California.
My hope is for the poor countries of the world, where energy costs are beyond them, to be the seeding grounds for efficency discoveries and energy breakthroughs. But the way things are going, Germany has become poor with the EU, its taxes and the original devaluation of the DM when the Euro was first introduced, England is fast on the track to becoming a poor country, and the US is slowly being sucked down with kinder and gentler taxes. So maybe good old yankee ingenuity will be needed once again.
David
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we raise the cost of manufactoring so much by insisting on clean manufactoring that the jobs are pushed to China where they cause much more pollution.
You are probably right; I suppose the only effective solutions are either a clean, economical power sources and/or applying the same emission restrictions to developing countries. IMO carrying on regardless isn't an option, or at least not a survivable one [:)]
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Germany has become poor with the EU, its taxes and the original devaluation of the DM when the Euro was first introduced, England is fast on the track to becoming a poor country, and the US is slowly being sucked down with kinder and gentler taxes.
Not exactly becoming poor, I think even the German economy is still growing, although slowly, but the US economy is growing faster and has done pretty consistently for decades. This is probably because the US still has vast unexploited natural resources (including the Yankee ingenuity you mention, I suspect[:D])
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I find it interesting that you see the success of the USA being based on resources. I would say that Russia has the most resources of any country in the world.
How about the phylosophy of the country, the mix of individuality, capitalism, responsibility, and irrevent behavior that makes us snubbed by those who know better, but can't do as well.
Put that together with the Japanese ability to take a concept and perfect it, and it is an interesting world. Of course the Japanese still haven't come to grips with the fact that their plants in the USA are their most productive plants.
An American will start out working today for about $8 an hour, get two weeks vacation after the first year, and just a few sick days. He doesn't think his boss is his better, and is generally encouraged to speak up and make suggestions or to solve problems on his own. Not quite an Italian in his disreguard for rules and laws, but proud of what he does, and not afraid to look for a better job, and more education. I know something of education, and admire how tough the British system is. But for all your abilities to write, and our inabilities, we still get by very nicely. Hmmm
David
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I have to give you the hard work thing, I know at least two people (former colleagues) who took jobs in the States and came back after a couple of years for a rest![:)]
I still think there is something in my argument that resources play a part in US economic success. For example, land and timber are plentiful and cheap, which means houses and food are. More disposable income, greater economic activity.
I must admit, though, that I was being a bit snide (because of your remark about the UK being on the fast track to poverty!). To make up for that I will further admit to reading a number of American authors with pleasure [:)]
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I think the USA is on a track to poverty as well. More and more people "ask what their government can do for them" (Sorry JFK). Tax away incentive and we all become impoverished.
There is an interesting movement on over here for a unique flat tax that would restore a lot of that incentive. They are proposing a flat 17% retail (as apposed to value added) tax. Easy to collect, minimum paperwork, the poor get a check each month to reimburse for food shelder and clothing.
The thinking is that all products have at least that much build into their price and that the prices would not need to increase.
That may be but I am not sure about the shock of transitioning to the new structure. Otherwise it sounds like a great idea, unless you work for the tax bureau or are a tax accountant.
David
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Hi! I'm new member here. While surfing I came here ands found some interesting topics so decided to be a part of this community. Hello to all forum members, I'm john.
Hi Hades
I'm astonished that you say that gas doesn't exist in nature in its elemental appearance - what most the sun ? That's tempered up 5 billion twelvemonth's couturier of element so far !
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