Hydrogen

[meganiwish]

I've just been watching a thing about hydrogen cars.  It seems that the way they're going is to use the hydrogen to make electricity to power an electric motor. Can any of you clever chaps tell me why they don't just make a combustion engine that uses hydrogen?

I can see the problem with hydrogen.  There's lots of it about, but all tied up.  It takes a lot of fossil fuel to release it, so rather pointless, and electrolysis leaves you with an uncomfortable amount of chlorine, even for California, where I'm told they have a lot of swimming pools.

It's tempting to think we might use hydrogen as the energy to release hydrogen, but that has the ring of perpetual motion about it.  We might be better off walking.

[at9]

Hydrogen can indeed be used in conventional internal combustion engines. It works pretty well giving just water vapour in the exhaust. Thus any nasty emissions are moved fromt he point of use to the centralised places where the hydrogen is produced. You can make hydorgen with any form of energy, from coal to renewables. The alternative to burning hydrogen is using it in fuel cells to make electricity. This could give better thermodynamic efficiency but is currently expensive and complex.

Not sure why you say that electrolysis will produce chlorine. Water contains hydrogen and oxygen so electrolysis will just give those 2 gases. Not entirely sure what happend if you electrolyse sea water. You'll probably get some chlorine but it's a useful industrial feedstock.

My worries about hydrogen are about overall efficiency, infrastructure and safety. I don't know the total thermodynamic efficiency from primary fuel to the car's wheels but I'm pretty certain it won't be good. Too many stages each with its own losses. You can make a case that this is a price worth paying in city centres where tailpipe emissions are a severe problem. Hence some hydrogen buses in London.

A nationwide infrastructure to handle hydrogen is no small thing to build which is why I suspect it will be confined to niche applications like city transport. Also intimately tied up with safety. Hydrogen is quite nasty. It will burn or explode over a very wide range of concentrations in air. It burns with a near invisible flame too. Much more hazardous than petrol in all respects. More hazardous than natural gas (methane) too.  It's also a houdini of a gas and will escape from the tiniest of leaks with attendant fire hazard. We also have no idea if increasing atmospheric hydrogen concentration will be harmful. It will increase signifcantly with a large infrastructure if only because of leaks and accidental releases. I suspect not harmful but that's not really good enough. I wouldn't like to see another problem like CFCs. Having said that, old fashioned town gas contained a lot of hydrogen and we seemed to be OK with that. People got poisoned by town gas due to its carbon monoxide content.

A lot of questions, not too many answers. Overall I'm glad there's lots of R&D plus some niche applications but I can't see hydrogen fuelled transport becoming mainstream.

[Heelster]

at9 pretty much has it summed up.

[dww]

What about all those cars taxi's etc driving around with large canvas bags on the roof, during the war years.

[ShoeDre]

I'm not sure about the previous answers, but the hydrogen car is effectively a battery car.  Just like other battery systems, the pure hydrogen holds potential energy.  It uses oxygen from our atmosphere as the other potential energy source.  The hydrogen is combined with oxygen, which releases energy in an exothermic reaction.  The resultant output is H2O aka water.  The reaction energy is harnessed to create drive.

I remember seeing a working model of this in a report at least five years ago.  At the time the key issues were cost and how the hydrogen was made.  I think hydrogen was roughly double the price of regular fuels at the time I viewed the report.

Making hydrogen uses energy.  If you use coal or petroleum sources to create the energy, then the process is just as dirty as our current system.  Harnessing renewable clean energy needs to be part of the process involved in hydrogen vehicles.

I will admit that this is all from memory, so I might have missed something.  Also worth noting, I don't know much about the above mentioned safety issues, however the current petroleum products shouldn't be considered ultra safe either.

Hope that helped a little.

[at9]

"... but the hydrogen car is effectively a battery car.  Just like other battery systems, the pure hydrogen holds potential energy.

That is equally true of a petrol car, a steam locomotive etc. In all these cases there is stored energy of some kind on board the vehicle. But not of a tram (trolley in US), or electric train where there is no significant stored energy on board the vehicle.

The main advantage of hydorgen fuelled vehicles is that there are no nasty emissions local to the vehicle. If the hydrogen can be produced from clean energy sources then the whole supply chain is clean. Otherwise it's simply transferring the pollution to somewhere else, where it may or may not be better controlled.

Electric hybrid vehicles are somewhat different because they utilise the ability of electric motors to work efficiently in a stop/start enviroment such as city driving. The associated internal combustion engine can then be run either under optimal conditions or not at all. They give no advantage under motorway cruising conditions since that is where an IC engine is operating efficiently anyway. In fact there's a disadvantage because you're lugging around the extra weight of batteries and motors. It's hardly surprising that many London minicab drivers use a Toyota Prius hybrid

[meganiwish]

Ooh, lots of informative answers.  Thank you.

at9, I was taught electrolysis at school.  We used salt water and foil and a pencil lead for the anode and the cathode (I can't remember which way round.  We collected the gas over water.  I did it with a number of my primary school classes using 12v batteries.  A glowing splint gives a satisfying pop in the hydrogen.  One needs to inspire future scientists beyond the undoubted joys of sitting still, watching closely and writing down numbers.), so I'm ashamed to admit that I rather thought the salt an important part of the process.  Can you use  electrolysis with fresh water?  But of course you  couldn't on a large scale.  It's sea water we're awash with.  Yes, it produces chlorine. If you were aiming to use hydrogen as a global fuel source it would give you much more chlorine than could be used industrially, but I didn't know of other ways of producing hydrogen.

One can theoretically make ice using a wet tea towel.  Wrap a bottle of water (or wine, if you're more sensible) in a wet tea towel and put it in the sun.  When the towel's dry the wine will be chilled.  Now, if you rewet the towel often enough and keep it in the sun for long enough you'll have ice.  The trouble is, the sun goes down, so the problem is, how to get permanent sun?  Would it be possible to have something that was not in geo stationary orbit, but in solar stationary orbit?  Then you'd have endless solar energy.  You could use that to unlock hydrogen, the most abundant element in the universe.  Why bother, you ask, since you can have unlimited electricity?  Well even I know that it's more fun to put your foot on the pedal and go vroom rather than zzzzzz.  Actually, they don't even go zzzzz they go eeeee.  No electric motor could have inspired this https://www.youtube.com/watch?v=xm5DPlNCmtk

Safety is just logistics, just a case of taking enough care.  Forewarned is forearmed.  You probably can't increase atmospheric hydrogen, because it so joyously joins with oxygen.  You might make it rain more, though, and that could be a problem.  As I said, we should probably walk more.

[at9]

The reason you added salt was to make the water conduct electricity. Pure water is a very poor conductor.In fact electrical conductivity is used to meaure the purity of water. As well as electrolysis there's a lot of work going on to mimic photosynthesis to get electricity directly from sunlight. None of it very successful yet.

There are several grand schemes to harness solar energy on a huge scale without the trouble of going into space. Look up Desertec for example. Technically feasible, politically difficult. If you covered a relatively tiny part of the Sahara or Arizona with solar power systems (photovoltaic and/or solar thermal) you'd have ample energy for the world.  Apart from the politics and the logistics of getting the energy to the point of use the problem as you rightly say is storing the energy when the sun isn't shining. There are various systems for doing this such as flow batteries, compressed air in caverns, molten salts. None is quite ready for mainstream use yet but there's nothing that a bit of intensive R&D can't solve. Along with the will to do it.

We honestly don't know what happens if you leak siginificant amounts of H into the atmosphere. It may react harmlessly with O to make H2O. Or there may be unforeseen effects. Concentration in air is about 1ppm. Free hydrogen tends to escape into space.

[meganiwish]

Now, I'd been led to believe that water was quite an efficient conductor, the reason why switching on lights with wet hands is dangerous and why you die of hypothermia so quickly when wet.   Of course, the free hydrogen escapes into space.  It's lighter than helium, and Captain Joe Kitinga showed us what you can do with helium.

Always better to avoid going into space if you can.  Battery technology is the important thing.  I'm sure we all know the joke about the chap with two heavy suitcases who sells an amazing watch to a passer-by at a givewaway price.  The buyer makes to walk off and the seller says, 'You'll need the batteries.'  But it seems to me that, if you can harness unlimited energy, you can stop worrying about efficiency.  Anyway, here's a thought - are there deserts that could be pink on the map, that the Sun never sets on? You've got the Gobi, the Sahara, the Atacama, the Arabian.

But you have it with 'the will to do it'.  People are hypnotised by the notion of political power, a nonsense.  There are three ways of holding power - control the water supply, control the food supply, control the fuel supply.  The three basic human needs,  So why would those who control energy.....?

 

[at9]

Pure water is a very poor conductor of electricity but most water is not pure. Hypothermia is nothing to do with conduction of either heat or electricity. When any substance evaporates it absorbs heat. So as water evaporates it absorbs heat leaving whatever it was on colder. For a dramtic demo of this look look at propane cylinders covered in ice when in use. The liquid propane inside evaporates into propane gas with associated cooling.

Correct to say that efficiency doesn't matter if the technology is cheap enough and you have enough space. For large scale solar the most important parameter is usually cost per installed peak kilowatt. The sunshine is free. Just need to be sure that maintenance costs are also low.

True to say the sun is always shining somewhere. Getting huge amounts of leccy between continents is nowhere near solvable at present. Geopolitics is a big reason why Desertec is likely to fail.

[meganiwish]

You'd be more accurate saying that any change in state of matter is an exchange of energy.  Melting or evaporating  needs energy in, so it draws it from the surroundings.   That would be why the children measuring the temperature of melting ice found that it went down, and why my martini gets cold.  Semantics, I know, but who am I if not semantics?  I think the phrase you were holding back from was 'latent heat'.  I've 'sniffed ether contrary to teacher's instructions' with the best of them.  I was one of the ones who passed out.

Au contraire, being in water is a cause of hypothermia and nothing to do with evaporation, all to do with conduction, because water is a good conductor.  Spend enough time in enough cold water and you'll die of hypothermia because of entropy.

There you have it, the cost should be almost nil, barring maintenance

[at9]

You're right that I shied away from the term "latent heat". Of evaporation in this case.

I'd overlooked the case of being immersed in water. The cooling is then by conduction and convection, not evaporation. Water is a mediocre thermal conductor so I suspect that convection is the main culprit. A wetsuit works by trapping a thin layer of water next to the body. Since there is minimal convection this reduces heat loss dramatically. Of course the good thermal insulation properties of neoprene help too.

Conduction of heat and conduction of heat are not necessarily related. For example diamond is an excellent electrical insulator and superb thermal conductor. Some metal oxides such as alumina and beryllia are in the same category. I'm struggling for examples of good electrical conductors that are also poor thermal conductors. If only because most good electrical conductors are metals. There are some electrically conductive polymers and also thermoelectric materials like bismuth telluride. Not exactly good electrical conductors but definitely not insulators either.

I rather liked the smell of benzene** in 6th form chemistry. Known carcinogen even back then. I'm almost 60 and no ill effects so far.

 

**Benzene, the cyclic C6H6 compound, not benzine, sometimes used for various fluids including petrol

[meganiwish]

You're quite to infer that I hadn't considered convection, but I still think that conduction must be the culprit, by analogy with the experience of touching metal or wood on a frosty morning.  They're the same temperature, but the metal feels colder because it conducts heat from your hand.  Jump into an ambient temperature pool and it feels cold.  That must be down to conduction.

I suppose we get here from using unquantifiable terms like 'efficient' and 'mediocre'.  I suppose I should have said that water is a better conductor than air.

I imagine it's almost entirely the insulating properties of neoprine at work stopping hypothermia with a wetsuit, and that the water works by maintaining a layer of body heat around the body, like being in a blood temperature pool.  Of course, the water could only be blood temperature if the heat had been conducted into it.  I suppose with the air trapped in layers of dry clothing it's radiation at work.

I should say, 'I love the smell of napalm in the morning,' but I prefer the smell of cordite in the autumn.

[Gudulitooo]

Hi Megan,

I am working in the fuel cell industry so my point of view may be biased.

To my better understanding, the reason why people think hydrogen powered vehicles may be of interest comes out of the following reasoning:

1) Fossil fuels produce greenhouse gases, which is armful on a medium range (already seeable effect is the rise of sea level that reduces land)

 

2) Most western countries (I am in Europe) have depleted their fossil fuel reserves (I am not telling that shale gas and oil are bad, but even the US does not seem to 100% rely on this ), thus

      2 a) they rely on third parties to satisfy their needs, which may turn harmful for any of the parties, emitting or receiving (wars, embargos, etc.)

      2 b ) this costs a lot to customer countries

      2 c) following the example of western countries, fossil fuel rich countries may also deplete their reserves, especially when China, india and Africa reach the same level of consumption as us (per individual).

 

The intermediate conclusion is that a way of powering our transportation means, our industry, our homes (also for heat), that can be produced, stored, transported,and used without the need of third parties, is required.

 

Now look at what ressources western countries have.

 - Oil, Gas, etc. : not really enough (except for US but for how long ?)

 - Wind, solar, waves: a lot. That produces mainly electricity.

 - land / crops : somewhat limited, we also have to eat.

 - wastes: a lot. But already recycled into heat / electricity when possible. Definetely something to consider.

 - nuclear facilities (which are harder to erect than to find radioactive material) : many, they produce electricity

 

Now how to get these "local" ressources, which are almost all electricity, into a car and have the car move ?

 - battery cars ? Yes good. But having a battery with a drive range is 600 km and cost effective is an ongoing process and can take ages. The idea of recycling, at the world scale, all these different batteries containing polluting elements, and made of almost depleted ressources (metal, rare earth) is scary. Today car batteries (starters) are all the same, so easy to recycle.

  - convert electricity into hydrogen, store it, distribute it, then power the car ? Weight / drive range is ok 1000 km+. Cost is not that bad.

 - convert electricity into hydrogen then into natural gas (it is possible) ? That is a nonsense today, too much losses in the conversions

 - convert wastes into biogas and upgrade to NG for home heating ? Excellent, but projects are slow going because neighboors say it will stink.

 - convert biogas or directly wastes into a liquid fuel, which is simpler to handle ? Still in reseach phase.

 - reduce car / transportation needs

 

What we think is not only one of these routes is able to fulfill alone our energy needs. So people try to develop every idea. Also hydrogen.

Of course, should the initial hypothesis change (new abundant ressource found, no more worries about climate change), then it will be over for hydrogen.

 

Finally, of course you will find that it is cheaper, easier, safer, whatever to power a car with diesel fuel.

Yes, taking the ressource in the ground is "easy". That is why trying to live without, while other people do not care, seems to be a nonsense.

 

[meganiwish]

Hi Gudulitoo,

Thank you for your long and considered reply, more effort, I know, when it's not your first language. I've learnt a lot.

My real wondering was why use hydrogen to make electricity for cars rather than using it directly in a combustion engine?  There must be a reason, I suppose.

You raise two interesting points.  First is the last in your list -just reduce energy use  . Mr Micawber's famous, and oft-quoted, recipe for happiness: "Annual income twenty pounds, annual expenditure nineteen [pounds] nineteen [shillings] and six [pence], result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery."  Second you mention bio-fuel.  Quite right.  Plants convert the Sun's energy into a form we can use, but only a finite amount.  It leaves the question, do you want to eat or drive.  Ultimately it's all hydrogen and carbon, I suppose, carbohydrates or, in the case of fossil fuels, hydrocabons.  I suppose the thing is that the rate of energy coming from the Sun is fairly steady, but with fossil fuels you have thousands of years of the Sun's energy stored.  Hard to replace in a hurry.

[Gudulitooo]

Hi Megan,

Thank you for reading even if my english is that bad.

You are right hydrogen can be useful in a combustion engine.

But people want to show improvements right from the first hydrogen car. They don't follow my last post, in which I stated that hydrogen is not considered for improving the car only, but for improving the whole energy sector (from the reduction of energy imports to mitigation of climate change, through reduction of local emissions).

However, first hydrogen cars may be powered with standard industrial hydrogen out of natural gas conversion. Yes fossil natural gas. Almost a nonsense.

"Almost", because it is borderline :

 - with a combustion engine hydrogen car, converted natural gas proves no better than diesel cars, except for local emissions.

 - with a fuel cell, thanks to the better efficiency than combustion engine, even the first hydrogen car, powered with converted fossil natural gas, show more than 25% cut in CO2 emissions.

All automakers have thus choosen fuel cells because they do not want to rely on "renewable hydrogen". A game changer to this is that recently, large gas companies understood that they were able to pay "bio - methane" certificates to provide hydrogen for cars, when biogas plants are feeding gas to the grid.

 

[meganiwish]

You've answered my question really. So electric motors are more efficient.  Sad not to have the vrrmm of the combustion engine, though.

By the way, your English is fine, but if you ever need to PM me you're welcome to do it in French if that's easier.