by Merrick
Q: When is a low-carbon fuel not a low-carbon fuel?
A: When it’s hydrogen.
If you think that’s not funny, you’re right. It’s not. Hydrogen is being touted as a climate saviour, yet would actually lead to greater carbon emissions.
A British company called ITM Power has unveiled a home electrolyser, a device that uses electricity to to make hydrogen from water.
The BBC report says
The hydrogen home refuelling station works via an electrolyser which produces the gas from water and electricity.
An internal combustion generator converts the gas back into electricity to provide power for the home.
So let me get this straight - we take electricity that’s coming into our house, convert it to hydrogen, then convert it back into electricity for use in the home.
Erm why not, I dunno, just use the electricity as electricity without wasting the majority of it in this machine? Making hydrogen from water takes colossal amounts of electricity; at 30% efficiency, we lose 70% of the energy we put in.
But the real focus for hydrogen isn’t on domestic consumption, it’s for making is into a car fuel.
Most hydrogen car prototypes are fuel-cells, basically using hydrogen to produce an electric charge to power the motor. As with the domestic use, the hydrogen is just being used as a way to store electricity; it’s a battery. There are far more efficient batteries on the market.
As I recently pointed out, the emissions from a smallish hydrogen fuel-cell car are at least as bad as a petrol car.
There is, though, an even more inefficient use of hydrogen. Don’t use a fuel-cell, but burn the hydrogen. That’s what ITM have done in their converted Ford Focus.
Here comes the maths
Get out the envelope and turn it over, it’s time for a calculation.
The ITM press release says
The demonstration vehicle can travel 25 miles on a single recharge of hydrogen
In emails, the firm say a ’single recharge’ is 1kg hydrogen.
Electrolysis requires 39 kilowatt-hours (kWh) of electricity to produce 1 kilogram of hydrogen.
CO2 emissions from the UK grid are 480g/kWh.
39×480= 18,720g/CO2 per kg hydrogen.
25 miles is 40.2km
So the emissions for the hydrogen Ford Focus are 18,720g divided by 40.2km = 466g/km
How does that compare?
The emissions figures we’re usually given for cars only measure the exhaust. The US government says that’s 78% of the CO2, with the remaining 22% being emitted between the well and the pump.
A normal petrol powered Ford Focus exhaust-emits 159g/km, giving a total 204g/km.
The UK average for a car on the road is 171g/km (219g/km total). The low end would be the Volkswagen Polo Bluemotion at 99g (127g), the high end is around the Porsche Cayenne at 310g (397g).
To beat the hydrogen car’s 466g we have to go off into the paramilitary level of a Hummer H2 at 412g (528g).
What if it’s made from renewables?
The maths presumes the electricity’s taken from the grid. The hydrogen could be made from renewable electricity, but even this would lead to an increase in emissions. At the moment we power our cars from oil. If we start powering them from electricity, we add to the overall amount of electricity consumed. If you ringfence the renewable electricity for making hydrogen, it means more fossils will be burnt to make up the shortfall.
It’s like the way biofuels companies say they’re not cutting down forest when they use arable land for their plantations; in doing so they displace the food that would’ve been grown there, and there’s a knock-on that means someone somewhere is cutting down forest to grow food.
And not only does hydrogen take from other sources, but it does so very inefficiently. There’s no justification for making hydrogen from electricity that isn’t a bigger reason to make straightforward electric vehicles.
In the film on the BBC report, the guy from ITM says they want hydrogen to ‘displace fossil fuels’ but that it will ‘take a few years of building up the infrastructure of renewable energy systems to be able to do it’.
It will, as the Tyndall Centre found, take more than that.
replacing current transport fuels with hydrogen via electrolysis from renewable electricity would require a doubling of the electricity generating capacity of the UK.
To make genuine carbon-free hydrogen for our cars we need to eradicate fossil-fuelled electricity whilst doubling the amount of electricity we produce!
(And the Tyndall Centre talk a lot about fuel-cell cars, so I’m guessing their figures are for those, rather than the far more profligate hydrogen combustion cars.)
Anyone think this can happen in the next couple of decades before runaway climate change begins?
Anyone think it’s sensible to be making what amounts to a new generation of higher-emitting cars in the mean time?
Does this take into account the new technology being touted by MIT.
This would work, if we had so much wind power that on windy days we had far more electricity than we needed; and so much nuclear power that every night we had far more electricity than we needed. Then it would make sense to produce hydrogen by electrolysis during those times, or to charge up battery vehicles. That is a possible path to low carbon transport, but replacing the vehicles is probably the last step, and not the first.
You’ve missed a few points:
1) The H2 from renewables would be “stranded” energy. This is the stuff generated when you are asleep (wind) or at work (solar) that can otherwise go wasted. H2 can be better than batteries for a number of reasons. This is particularly true for the target micro-generation market. A hell of a lot of energy goes wasted that could otherwise be stored & used later.
2) The H2 for automotive is via off-peak grid electricity if not renewables. This is generated in any case, is cheaper but yes does have a C02 component. If not off-peak then the economics don’t line-up either so only a fool would do that - or someone very desperate for a 25 mile ride without any oil to do it with.
3) H2 is a very effective storage medium for renewables - demand and supply don’t alwats line-up a storage medium smooths out the peaks and troughs. This is true for large-scale and micro-generation models.
4) If the H2 is developed from micro-generatin renewables then there is no C02 component once installed.
5) The ITM kit already beats the US DOE target price per KW !!
6) The idea is not to use Grid electricity to generate H2 to then power the home - it’s intended to use micro-generated electricity to do that.
To get your head around this you need to take a system view. Strange but tru electrolysis can be better than batteries. New versions will have the Eletrolyzer inside the storage tank and Electrolyzer marries to fuel-cell - the by product can be drinking water. With a water butt and simple filter you don’t need a Grid water supply either.
Care to name some of them?
Given the appalling inefficiency of electrolysis, I don’t see how it can be better than pumped hydro or compressed air. Heck, in order to store a significant amount of hydrogen in a reasonable space, you need to compress it to the point where there’s far more potential energy from the compression that there is in the actual gas itself. (Remember,a mere 2 grams of H2 at standard temperature and pressure occupies a volume of 22.4 litres…)
Oh, and we haven’t even mentioned the exotic catalysts required…
I’m pretty damn sure you’d be better off using compressed air as a storage medium.
You seem to have missed the great and proven advantages that do exist with the ITM technology. In fact you’ve missed so much I really do wonder what your purpose is in printing so much misinformation, seemingly quite deliberate.
A very disingenuous article.
I hope you find time to actually go through the technology rather than whip up a misinformed article on the back of a BBC news release.
For your info ITM Power website:–
http://www.itm-power.com/
I think author may have allowed himself to get carried away doing the maths, which is ok, but based on false premise and overlooked the basic points. H2 from solar or wind does not involve generation of CO2.
Dunc: you need to look up an uptodate source. ITM have done away with exotic catalysts. H2 storage is more advanced than that requiring 22 litres per 2 grammes.Batteries have 2 handicaps;
limited supply of Lithium, and eco issues concerning disposal.
A poorly researched article.
[A poorly researched comment. Either show why you think the claims in the piece are poorly researched, or stop wasting your own and everyone else's time... - The Management]
Richard
IMO Merrik did not do his homework and
jumped on an old BBC snapshot to write a
piece for his quota. I agree it is misinformation, but it’s caused by naivett not malice.
Perhaps he will do the honorable thing and correct himself, Given we do not have too many great inventions such as ITM’s so he should not knock it.
(for those of a similarly cynical disposition to mine, I’ve checked assorted blog stats - the comments above come from different IP addresses and apparently from a reasonable range of referring pages. Which is weird, given that they’re near-identical content-free attempts to disparage the article without actually refuting any of its claims…)
It is a poorly researched article because of the same reasons highlighted above, which I agree with. Would you like me to copy and paste them to my message for in case you didn’t read them the first time? I suggest you make use of an editor to review and edit the content of such articles rather than expect me to do it for you.
John B: You are entitled to be a cynic.
That is an ok stance to take. However to deny that anyone refuted the claim made by the article is less than wise
Here is the main claim which I have already refuted in an earlier post.Thus your comments if I may say so, are in the same class as those made by someone you rejected rejected.
The article starts as follows :
“When is a low-carbon fuel not a low-carbon fuel?
A: When it’s hydrogen.
If you think that’s not funny, you’re right. It’s not. Hydrogen is being touted as a climate saviour, yet would actually lead to greater carbon emissions.
A British company called ITM Power has unveiled a home electrolyser, a device that uses electricity to to make hydrogen from water.”
I have pointed out in earlier post that H2 from Solar or wind does not involve CO2 generation. If that does not tear up the false premise of Mr Merrick’s note, I do not know what does. Cheers
The original article is so biased and orientated towards the promotion of battery Ev’s it’s tempting to not even bother making a comment, but I will as there’s issues larger than all of us at stake here. We need to urgently develop H2 technology as the spectre of Peak Oil stares us squarely in the face.
We need a Manhattan Project determination in ALL TECHNOLOGIES THAT WEAN US FROM FOSSIL FUELS. Creating an article that causes misleading negative sentiment to the less well informed is doing none of us any favours.
Please explain to me how I would be contributing Hummer grade emissions from my vehicle/home if an ITM electrolyser were powered from a solar PV system on my roof?
Please also explain to me how modern society is going to function in the face of Peak Oil with only your favoured battery technology? Battery technology has its place but it can only go so far and in a post Oil world it won’t power ships, planes, big rigs and other industrial vehicles e.g. farm equipment, construction industry machinery JCB’s etc.
I say thank goodness for forward thinkers such as the people at ITM Power. We should all be embracing their efforts and every other technology that has the potential to maintain the quality of life many of us have grown accustomed to. Attempting to discredit one of the potential solutions to me displays a worrying naivety of the bigger picture.
“I have pointed out in earlier post that H2 from Solar or wind does not involve CO2 generation. If that does not tear up the false premise of Mr Merrick’s note, I do not know what does.”
Under the most optimistic plausible projections, only 12% of UK grid electricity is expected to be generated from renewables by 2020. This suggests that you’re the one starting from false premises.
John B
I cannot believe what you have cited to justify the blind spot to your colleagues false premise. The Dept of energy had a cost target for renewable H” at $250/KGh2, for 2015. ITM are now below $100/KGH2.
You are not a cynic, but I am sorry to say, papering over your colleague’s mis-information, which being a cynic myself, leads me to believe you have an agenda which strips you of any shred of intellectual honesty. Look in a mirror and think about what I just said. Science progress would have been stillborn if scientists were dishonest.
If I give you benefit of the doubt and say the man does not do science, then that makes it worse as only a fool does not recognise his error, once pointed out to him.
John B
I should have added, that you are a little behind the clock in the speed of how things are progressing. Wind in USA will account for 20%+. Waves and wind are making big progress in UK. Not meaning to insult your knowledge, but anhydrous ammonia made from major renewable projects can generate cheap
100% renewable, non CO2 hydrogen. I will not press you more, since you are determined to diss ITM.
John B
Sorry but I must bring Paris Hilton into this discussion. It is fair to say she is better known for her beauty of form that cerebal strength, to be kind.
Yet even the lovely Blonde, Paris, knew that we will not immediately displace Oil & Fossil fuels totally, but we will reduce our dependance gradually.
Maybe it is time for Mr Merrick to adress the arguments made against his less than honest article, and come clean with his real agenda.
Batteries downsides:
Kg per Kw out over life
Volume space per Kw out over life
Cycle life - limited - big downside
CO2 in manufacture & ship - substantial
Disposal - problematic
H2 upsides:
Kg per Kw out over LONG life
Voume space per Kw out over LONG life
Life - Long
Lower CO2 in manufacture over life
Disposal - long time off and easier
Now for SELF compression.
1) 75 bar currently demonstrated.
2) 300 bar ongoing.
Failure modes:
None yet demonstrated.
Rare Earth metals:
Being reduced to zero - already lower than competitors.
John B:
“Under the most optimistic plausible projections, only 12% of UK grid electricity is expected to be generated from renewables by 2020. This suggests that you’re the one starting from false premises.”
UK is not the first major target market. US/Spain/Denmark are.
Denmark has substantial wind power generation capability but 90% of it needs to be backed by conventional generation - why? Because there is insufficient supply smoothing via a storage medium and they have few mountain to do a pump-up hydro scheme.
Micro-Generation will become more popular too. I think we will all be surprised by the take-up and don’t forget the desalination side. Have a read of the latest from ITM.
Also, this MIT idea of solar to H2 is not new. Take a look at the patents logged and, you may be surprised to know, litle is new under the sun but some do hide their (sun) light under a bushel until the time is right.
A very interesting debate but I too fail to see how my own wind turbine generating H2 whilst I am at work or sleeping can make my car very C02 generative when I burn the subsequent H2??
At least I could also cook with H2 without conversion to electricity and so reduce C02 there too.
Granted all conversions have inefficiencies but a lot of renewable power goes wasted so every little bit captured and used is a bonus.
Equipment cost is another matter but that should fall as acceptance takes hold and volumes rise.
To be clear, I’ve nothing against H2 as a way of turning renewables into a portable fuel source - just (and as this is a UK site I’m entitled to take a UK perspective) this isn’t a plausible outcome for the UK in the medium term.
(on personal rather than grid renewables, I thought the carbon cost of putting up a personal wind turbine was higher than the carbon saved compared with conventional energy?)
John B - not if the turbine is there long enough. Cerianly not as bad as deforestation for Ethanol via crops - can take 100’s of years just to replace the carbon loss due to removal of the trees. There was a study on this or Indonesia and it was shocking - something like 300 yrs per hectare cleared.
Agreed, current-generation biofuels are also a terrible idea environmentally. Modal shift to mains-electric transportation - electrified railways, trams and trolleybuses - is what’s required…
Not enough generation capacity to replace Hydrocarbons and build-out time is long and what about non-urban livers?
Tax breaks for micro-generation would help make each household less grid dependent, less C02 generative and liberate grid power for new grid electric based mass transport.
Comes back to the micro-gen level imho. Get that moving in the right direction and other things start to fall into place a little easier.
Jacob@15
H2 from ammonia? That’s the daftest idea yet. Most of our ammonia is synthesised from H2 and N2 by the Haber process.
So if you have another source of ammonia it is better just to sell it, than to make H2 from it.
Tell me I have got the wrong end of the stick, please.
John B
It is clearly a waste of time to debate the issue with you. You are not willing to admit the Merrick article is a piece of calculated misinformation that ought to be withdrawn. You deny facts because you do not wish to see them. Inflexible mind is a handicap to be pitied.
Joe Otten
Anhydrous ammonia, by whichever method it is produced, happens to afford an efficient & convenient storage for H2
making it more user friendly.
Jock (1), walk me through it - it seems to me just saying that solar power can be used to create hydrogen that can create electricity. I’m probably being thick, but where’s the revolution in that?
Joe Otten (2), it would indeed be a way to store spare electricity produced at times of low demand. However, the question for cars is; why not use that same electricity to charge batteries? Given that it is far more efficient than using hydrogen, we would need far less ’spare’ electricity to power our entire vehicle fleet.
Timothy (3), you’re absolutely right that a lot of energy gets wasted. It would be far more efficient to, where possible, use that energy directly when it’s produced. For example, have ’smart plugs’ that know when there’s a glut. You stick your washing in the machine, and at 1pm when the solar panel’s gunning it, it actually turns on.
That wouldn’t take up all of the slack, but certainly a lot of it. You’re right that there would need to be a storage method for the rest. My big point is that, at 30% efficiency, hydrogen is a waste of the vast majority of that spare energy.
ITM’s new plastic material that appears to do away with the need for platinum is indeed a breakthrough. There may well be a place for hydrogen. I doubt it’s combustion, as fuel cells are more efficient. Even then, the heat generated in fuel cells is wasted in vehicles (the recent European bus trial had to have cooling systems installed – using energy to disperse energy!). In a building, a large fuel cell could generate electricity and use the heat. This is a possible future use for ‘stranded’ electricity in the home.
However, my beef is with taking grid electricity for electrolysis, and with use of hydrogen as a vehicle fuel.
The off-peak grid electricity does not just have ‘a CO2 component’; it has identical CO2 emissions to peak grid electricity.
“New versions will have the Eletrolyzer inside the storage tank and Electrolyzer marries to fuel-cell - the by product can be drinking water. With a water butt and simple filter you don’t need a Grid water supply either.”
Correct me if I’m wrong, but doesn’t it work by grid water being turned into hydrogen and oxygen, then when the hydrogen is used in the fuel cell water is the by-product. Thus, you only get water out because water went in. I don’t see how this gets you off grid water.
The fact that micro wind turbines aren’t as carbon-intensive as deforestation (reply number 22) doesn’t make them alright.
There’s certainly a place for micro solar, and I completely agree that there should be tax breaks for anything that gets people off grid that actually works, but for most non-rural homes wind turbines are a waste of time.
If something causes greater emissions than it saves, it’s not a climate technology.
Richard (5), you complain of ‘misinformation’ yet don’t say what it is let alone put it right. You say it’s ‘disingenuous’ yet don’t say why. Then you say it’s just off the back of the BBC story and provide the link to ITM.
The very first link in my piece is to ITM. In case you can’t find it, it’s the highlighted bit that says ‘ITM Power’. The further link to the ITM press release and the reference to emails from the company make clear that there has been proper research. The idea that it’s all based on the BBC story ignores the links to the Academy of Sciences, the US Department of Energy, the Tyndall Centre, DBERR, and other sources.
Disingenuous stuff indeed.
Jacob(6), “based on false premise and overlooked the basic points. H2 from solar or wind does not involve generation of CO2″
Please read the final section subheaded ‘what if it’s made from renewables?’. As for it ‘jumping on an old BBC snapshot’, see my reply to Richard above.
Your post (14) about ‘misinformation’ and an ‘error’ on my part that doesn’t cite what it refers to also attacks JohnB in strong yet vague terms. Be clear about what you mean.
Your post (26) again says ‘misinformation’ without citing what it refers to. If you truly believe ‘it is clearly a waste of time to debate the issue with you’, why are you trying to debate?
The point of such public discussions is to get the facts and perspectives out and cross-examined, disabuse each other of any errors or ignorance, and do it so that a reasonable third party can come away with something close to the truth. It’s not a gladiatorial match. So if you’re going to criticise, be specific, and drop the mud slinging.
Your reference to the price of hydrogen is irrelevant. This is not about cost, it’s about carbon emissions.
You’re right that wind power is making big progress in the UK. It’s a little over 1% of our electricity. It’s rising fast, but even so is not taking us a largely renewable grid any time soon. JohnB’s comments stand. Waves, contrary to what you say, are (even by comparison to wind) still so small as to be irrelevant for the foreseeable future, in terms of displacing fossil fuels.
Again, I refer you – and Timothy (19), and Sam (20) - to the ‘what if it’s made from renewables?’ section. Until the grid is 100% renewable with spare capacity, then hydrogen as a vehicle fuel is an extravagance and will deliver less emissions cuts than other technologies on the table.
The allegation of a ‘real agenda’ smacks to me of desperation. It’s unfounded, and indeed makes no attempts to suggest what it might be or why.
LC (12), “Please explain to me how I would be contributing Hummer grade emissions from my vehicle/home if an ITM electrolyser were powered from a solar PV system on my roof?”
Unless you live in a mansion, your roof is unlikely to be large enough to generate your domestic and vehicle needs. What you put in to the car is not put into the home, and the shortfall’s made up from the grid.
For someone who has a massive solar array and a large wind turbine with all the power they need and spare, go for it. However, that’s almost nobody.
I reiterate the point that powering our vehicles from electrolysis hydrogen would take more electricity than we currently use for everything combined.
You are right that battery technology would be inappropriate for some large scale uses. However, that’s not what this is about. It’s about a home electrolyser and a Ford Focus.
Even with those other uses such as shipping, hydrogen’s not a clear winner. As with the cars, there’s a range issue - by volume, hydrogen gas at 5,000psi contains only a tenth of the energy of petrol.
I am not slanted to battery EVs out of some dogmatic position. I do not vociferously advocate them here or anywhere else. It’s just that I’ve yet to hear an argument for hydrogen cars or buses that isn’t a far stronger argument for battery ones.
I agree that we need a massive Manhattan Project style effort to develop low-carbon technologies. However, that isn’t quite the same as ‘all technologies that would wean us off fossil fuels’. Some climate technologies make little difference, others can be deployed in such a way as to increase carbon emissions. Agrofuels commonly do this, so does hydrogen.
We certainly need a lot of technological change, but we should not be ‘embracing their efforts and every other technology that has the potential to maintain the quality of life many of us have grown accustomed to’ if it doesn’t deliver the cuts in carbon emissions that climate science demands.
(I’m going to be away until Monday. I’ll respond to any further comments on my return)
May last 2p.
Merrick, in summary, there is a need for a storage medium for “stranded” renewable energy. Not every user will be grid connected so using their stranded energy on my washer via a “smart-plug” won’t always be possible. Load demand control via a “smart plug” is a good idea and one California bods considered when they had there energy shortage - also works to cut-off unecessary loads like toasters when there is insufficient generation capacity for the imporant stuff by sending out a “turn-off” signal. Different devices can be graded by importance and respond to different alert levels.
Anyway, every single % of renewables used instead of wasted = less C02 than would otherwise be the case.
H2 isn’t a bad storge medium and if done cheap enough can have a lot less impact than batteries. Using it in short range transport avoids the scrapping of existing combustion engine vehicles until their end of life. If the energy is from renewables the C02 contribution is minimal.
A side product of an Fuel Cell is drinking water and if/when it is shown saline can be used as the water source you have irrigation and pottable water for the sunny parts of the world where people can’t live. It might help green the desert fringes and offer a power source for irrigatin pumps etc.
I’m all for every effort to help get us off Russian and Arab dependency and help reduce C02.
There is supposed to be enough energy from the sun in 1hr to power the whle human race for 365 days but it’s not much use in the middle of the night unless stored. Chemical batteries are heavy, unpleasant chemically and can be hard to dispose of. An electrolser of the right design could offer a long service life and with less noxious debris at the end of life.
Finally, there are some island communities where H2 storage will make a massive difference whether generated from daylight or intermittent wind.
This is one of the weirdest threads I’ve seen for a while. Let’s take comment 29:
Erm, here in the UK, 99.9% of houses are on the grid. This is true in any Western country. In Africa, I think they have better things to spend money on than generating hydrogen: a lead-acid battery and a solar panel work can give you light at night.
What? A normal car won’t run on hydrogen without significant changes. I don’t believe a petrol engine can burn hydrogen; and, at the least, you’d need to add an expensive hydrogen fuel tank. Why is retooling old cars better than buying new ones using fuel cells? Especially as the life of a car is short compared to the likely uptake time of any significant number of people making their own hydrogen.
This is insane. You need water to make hydrogen. If the water is saline, there exist way more efficient ways of making it potable (reverse osmosis). So you must be taking about transporting hydrogen: somewhat different to the “use it locally” idea before. Transporting water is far easier. And in the middle of a desert? Erm, I’ll use a solar panel (or solar thermal) before piping in hydrogen and putting it into a fuel cell.
Pumped hydro-electric. Compressed air. Fly-wheels. All more efficient then stored hydrogen.
Well, of course - by increasing the pressure. Which is why I specified that figure at standard temperature and pressure (273K, 1 atmosphere).
Has somebody repealed the Ideal Gas Laws while I wasn’t looking?
How much energy is required to achieve those pressures (via either single-stage or multi-stage compression), and how much energy is stored in the gas as a result? How does that stored energy compare to the energy of combustion? Wouldn’t it be more efficient simply to dodge the whole hydrogen business and compress air? Especially considering that Compressed Air Energy Storage (CAES) is already in use (and has been since 1978) and that according to this article, round-trip efficiencies of 70% are not unreasonable (when operated adiabatically).
In the electrolyser, yes. However, if you want to use the H2 generated in a fuel cell… (Presumably this is part of the reason for preferring burning the H2 instead, with all the additional inefficiency that implies.)
ITM have FC based on the same material as electrolyser.
Batteries can be a problem in central Africa - you would know if you had lived there.
H2 economy needs energy cost to be comparable to oil. That is what ITM capabilities are offering - the keys to it via patented materials and manufacture process.
Doormat
I now realise how strongly contrarian and emotive this subject is. No one as blind as those who refuse to see. No wonder the thread feels weirs. Science has moved on the last few years and it is no shame not to be uptodate, but sad to refuse to consider what is happening to realise the hydrogen potential most likely solution to wean us from Big Oil.
Timothy (29) - As Doormat (30) pointed out, you may well have a case for remote off-grid people. However, they’re not really a big issue with regards to carbon emissions or energy independence.
This is the key issue that makes batteries more viable than hydrogen; not only are they more efficient, but electricity infrastructure is pretty much everywhere, hydrogen infrastructure is pretty much non-existent.
Yes, there’s a need for storage of stranded energy. Hydrogen, at 30% efficiency, before you factor in compression (another 4-8% or the energy it contains) or liquefaction (30-40%, and then more for maintaining refrigeration), is ludicrously inefficient.
[figures from the US National Academy of Engineering]
You’re right that ‘every single % of renewables used instead of wasted = less C02 than would otherwise be the case’.
However, using a technology that requires more units in for less out is waste, and requires more fossils to be burned to make up the difference.
I too am ‘all for every effort to help get us off Russian and Arab dependency and help reduce C02′; my point is that sometimes those things are in conflict. The clear priority is carbon reduction. Energy dependency is expensive, maintaining or incresing carbon emissions is suicidal.
Dunc (31) - as cited earlier in this post, compression of hydrogen to 300 bar (around 5000psi) takes 4-8% of the energy the hydrogen contains.
Burning the hydrogen does indeed remove the need for expensive and heavy fuel cell materials, and I too would guess this is part of the reason for using it as a combustion fuel.
It also doesn’t impact on performance as much as fuel cells, and drivers want the technofix to deliver speed and acceleration, even at the expense of the climate.
It is also much more inefficient than hydrogen fuel cells (let alone other technologies on the table) and so requires a lot more energy input per km.
Jacob (33) - please re-read my response to you (28). Vagueness and cliches help nobody. If you have something to refute then you should be clear and specific if you wish to avoid looking foolish.
Not sure if you’ve seen this before, Merrick.
http://www.evworld.com/library/ten_steps.pdf
Its got loads of good renewable data and refs, thought you might find it useful.
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