« BlogAds UK. | Main | Message to Suicide Bombers. »
August 05, 2005
Hydrogen Production.
Something interesting today on hydrogen production.
The institute, working with colleagues in Switzerland, France and Sweden on the EU-backed project, used sunlight to heat a metal ore, such as zinc oxide, to about 1,200° Celsius in the presence of charcoal.
This split the ore, releasing oxygen and creating gaseous zinc, which was then condensed to a powder. The powder was later allowed to react with water, yielding hydrogen to be used as fuel and zinc oxide, which was recycled in the solar plant.
Michael Epstein, of the institute, said: "The success of our experiments brings industrial use closer."
He said he foresaw the building of a commercial plant in six to eight years.
The process generates no pollution and the resultant zinc can be easily stored, transported and converted to hydrogen on demand. In addition, the zinc can be used directly, for example, in zinc-air batteries, which serve as efficient converters of chemical to electrical energy.
I’ll admit that my chemistry isn’t good enough to really understand this. What happens to the charcoal? Don’t we get CO2 from that?
But then the announcement is being made by people who presumably do understand their chemistry so if they say it’s pollution free then I guess it is.
This isn’t the first such news either. There’s a known process where TiO2 and water react in sunlight to produce H and O. Bunch of Aussies working on it (link forgotten) and they think they’ll have it working efficiently in four to five years. The actual numbers stack up so that the average roof area (one can make roof tiles out of slag containing TiO2) of a house would produce enough hydrogen to power that household, assuming the usual sunlight in temperate climes. In sunnier climes, more than enough would be produced to power a car as well.
August 5, 2005 in Climate Change | Permalink
TrackBack
TrackBack URL for this entry:
https://www.typepad.com/services/trackback/6a00d8341c2d3e53ef00d83459f2cf69e2
Listed below are links to weblogs that reference Hydrogen Production.:
» So much hot air? from The Devil's Kitchen
OK, I've been getting into a debate over at Tim's place about this zinc/hydrogen power generation idea, and a lot of people seem to be confused about it... I was going to blog an explanation, but then I checked around, and found this post from Engine... [Read More]
Tracked on Aug 9, 2005 3:37:58 AM
Comments
I think the charcoal is there as a catalyst.
Posted by: andrew | Aug 5, 2005 8:35:44 AM
I think the charcoal is there as a catalyst
Yeah, that was my first thought too, but at 1,200 Celsius? In the presence of oxygen?
The article was written by a non chemist, otherwise he wouldn't have written that the zinc is "converted to hydrogen on demand". That would consume energy, in vast amounts, if we even knew how to do it. I guess something has been missed out here.
Posted by: Chris harper | Aug 5, 2005 9:14:28 AM
I'm not sure how spot on this article is, but it does explain exactly how it works.
http://www.greencarcongress.com/2005/06/solzinc_storing.html
Posted by: Devil's Kitchen | Aug 5, 2005 9:33:15 AM
Right, reading through it, yes, you are right: CO2 is given off in the normal way. However, the molar weight of CO2 required for the reaction is the same molar weight of CO2 given off.
So, looked at in this way, any CO2 emissions will be, basically, offset by the amount of carbonaceous material required (and the fact that you don't need to produce so much heat) and thus net gain can be counted as zero. It's an accounting trick essentially.
"One side-effect of operating at the lower temperature with carbon as a reactant is the release of CO2. The research team determined that:
...compared to the conventional fossil-fuel-based production of Zn, the solar-driven carbothermic process can reduce CO2 emissions by a factor of 5. If biomass is used as a reducing agent, the process has basically zero net CO2 emissions, if the production rate of biomass can be matched to its use as a reducing agent."
Posted by: Devil's Kitchen | Aug 5, 2005 9:44:34 AM
Forgive the stupid question, but why chase difficult means of producing hydrogen like this one ? What's wrong with plain old electrolysis of water ?
Posted by: Freddy | Aug 5, 2005 11:40:55 AM
There is a fascinating discussion of this, with data, over here. Bottom line is: it's a beauty, as the carbon input could be sourced from waste and biomass, and the energy budget is good.
RTZ shares are, I think, a buy.
Tim adds: Yes, I saw that and meant to add it. EngineerPoet has done some good work there.
Posted by: Alex | Aug 5, 2005 11:52:44 AM
Forgive the stupid question, but why chase difficult means of producing hydrogen like this one? What's wrong with plain old electrolysis of water?
Because that requires a more power to be put into the reaction than you get out, which would rather negate the whole point of it. Plus, the electricity would have to come from somewhere.
If you use conventional powerstations, then you are rather rendering the hydrogen power redundant. If you use output from the hydrogen to power the electrolysis, you will still be consuming net power, and the same argument applies. Either way, you are consuming more power than you are producing.
Posted by: Devil's Kitchen | Aug 5, 2005 12:05:32 PM
Devil's Kitchen :
In this context, hydrogen is not a source of energy, rather it is a store of energy, just like the hydrocarbons in your petrol tank.
It is not as good as hydrocarbons because it is a gas rather than a liquid, which makes it a more of a bugger to store than petrol, but I assume the lack of CO2 from oxidising it makes up for this.
The only point of these alternative fuels is to find a way to convert energy from a form of which we have plenty (sunlight, wind, tidal) into a form we can conveniently use. Once we have a suitable process for this, then we needn't depend on oil.
The point of my question is that surely it would be easier to convert solar energy to hydrogen via electrolysis. This could be via Stirling engines (might be talking rubbish here?) or just a simple steam turbine that only needs temperatures of 101 Celsius rather than 1,200 Celsius.
It obviously wouldn't be 100% efficient - but it has got to be better than these daft ideas about biomass, which are also supposed to convert solar energy to chemical energy.
Any thoughts ?
Posted by: Freddy | Aug 5, 2005 1:40:04 PM
Freddy, what it all boils down to is which system is more economically viable. Which one, taking into account all factors, delivers a usable erg at the cheapest price once it is scaled up into production.
And the answer to that question is - dunno.
Posted by: Chris harper | Aug 5, 2005 3:03:04 PM
Freddy, I believe you have missed the point.
The energy is not stored as hydrogen in this case but as a powder which only needs water added in order to create the hydrogen. Storing and transporting a powder would be a damn site more cost effective/easier than trying to store and transport hydrogen in gas form or in some kind of carbon/oxide sink.
Converting solar/wind/fluid energy to hydrogen (via Solar Stirling, or any other mechanism) still leaves the huge issue of how you store the hydrogen produced, and how you transport the hydrogen to its' point of use.
Although there have been significant developments in these areas (carbon nanotube storage, high pressure cylinders and chemical storage), there is still scope for new ideas that could supercede any already being studied.
Posted by: Nik | Aug 5, 2005 4:27:00 PM
Nik, fair point, store the energy as zinc rather than hydrogen. But you've got to wonder if it is that easy to handle a substance that reacts so thoroughly with both water and air. (I have vague memories of metallic sodium having to be kept in large jars of some neutral sort of oil.)
Still ploughing my way through Engineer-poet's good stuff ...
Tim adds: Zinc is pretty unreactive. It’s the galvanised bit of galvanised steel. Certain metals, when powdered, become very dangerous (pyrophoric for example, if dry and then shocked can burst into flames) but I don’t think this is true of zinc. I do wonder how you would control the release of the H2 made by adding water to powdered zinc though.
Posted by: Freddy | Aug 5, 2005 4:50:36 PM
Freddy, you're right, of course. The zinc would also be 'difficult' to store and transport, but, in the powder form they are talking about, may prove to be far simpler than hydrogen gas.
On the other hand, it may not. It is certainly worth exploring, though.
Posted by: Nik | Aug 5, 2005 4:59:50 PM
Zinc (a transition metal, not a Group 1 like Sodium) is in pyrophoric form, fairly combustable; it would probably need to be kept in vacuum, or at least used almost immediately. This shouldn't be a problem, since the process of creating the powder would be happening within the power station itself.
Zinc Oxide, which is the ore which would be being transported around the place, is almost totally unreactive (hence the heat/energy needed to separate it from the oxygen during the process).
The joy of this process is that you get two fuels: hydrogen for burning (e.g. in a power station where you need to heat water, which produces steam to turn the turbines), and zinc for batteries (which could conceivably run cars). Or, alternatively, you can recycle the ZnO, and you start all over again.
It's a very neat solution.
Freddy, you may well be able to use a Stirling engine, but I do not believe that it would provide the power needed to yield the electricity required to power electrolysis on an industrial scale. Seriously, the bonds in water are extraordinarily strong, formed not only from strong covalent bonding, but also involving hydrogen bonds (which are the cause of water expanding, instead of contracting, when it freezes).
To build a Stirling engine which would create that kind of power, you would have to have industrial freezing units (using electricity) to create the hot/cold potential that makes the Stirling engine work. This is why we don't use them for generating electricity by themselves.
Electrolysis is very expensive in terms of power, and thus economically. It also negates the point of producing something that requires (almost) no power to run (other than sustanable energy, i.e. the sun). And, as I'm sure Tim will point out, the power required to build the power station in the first place.
(BTW, don't forget that we store methane and ethane quite happily (especially when they are under pressure). The problem with hydrogen has always been its very high combustibility. Hydrocarbons requires considerable heat to catch fire and liquid petrol, as we all know, doesn't burn: only the vapour combusts).
And I hate you all for forcing me to dredge up my A-Level Chemistry again...
Posted by: Devil's Kitchen | Aug 5, 2005 6:12:34 PM
So how much would it cost me to fill up my garage with Zinc, and what sort of profit might I make?
Posted by: Rub-a-Dub | Aug 5, 2005 9:24:15 PM
Yes, I know what you mean about A-levels, they do seem a long time ago...
Tim, I agree about zinc being unreactive; that's why I am having trouble getting my head around this whole miracle metal thing. I don't think the pyrophoric aspect counts for much - it just means that if you grind the metal to a fine powder, it burns in air; sort of like rusting very fast. It's a surface area to volume thing, and it applies to lots of boring old metals, including lead and iron.
Look, details are great, they make the world go round, but don't forget the big picture. In this case, in the absence of nuclear reactions, energy is not going to be created or destroyed, it is only going to be shifted around from one form to another, generally with a bit of wastage at each conversion.
DK (may I call you DK?) I'm sure the bonds in water are strong, but it doesn't matter what you use to break them, it takes the same amount of energy, whether via electrolysis or via this zinc reaction.
Forget the Stirling engine ('cos I don't know much about them) and the zinc-air batteries ('cos I don't know anything about them), and focus on the hydrogen generation.
If you have a field full of sunlight, and you want to convert it into a tank full of hydrogen, then you want a simple reliable process for getting from one to the other.
The article Tim linked to originally described a process with temperatures of 1200C, strange chemical reactions and the production of carbon monoxide.
Electrolysis requires temperatures of 101C, a bog-standard steam turbine and a dynamo.
From a position of no expertise whatsoever, I would have thought the electrolysis route would be cheaper and easier. Why am I wrong ?
Chris Harper was entirely correct a few posts back about what matters is finding a process that is economically viable - to which I would add, without any explicit or implicit public subsidy.
The trouble with the whole area of alternative energy is that, even without the global warming clowns, it is so filled with people looking for a hand-out from the public sector that there is a lot of bullshit in there.
As Nik rightly says "there is still scope for new ideas that could supercede any already being studied". I am happy for my taxes to be used to fund research in this direction, but I would like to see it being spent sensibly.
Bah. Don't understand this yet. Makes me grumpy.
Posted by: fFreddy | Aug 5, 2005 11:31:57 PM
"Electrolysis requires temperatures of 101C, a bog-standard steam turbine and a dynamo."
Really? I was pretty sure electrolysis was the splitting of the H and O bonds, not the production of steam. I was also pretty sure it involved putting in electricty (the elec- being the operative part) rather than merely heat.
About the storage of H2. This has been "solved" recently. Carbon nano tubes (another team used buckyballs) either coated in or containing scandium (Yay, our favourite element!) hold up to 9% of their weight in H2. Easy and quick to fill such a tank, measured release OK, and that by weight number sufficient to give a reasonably sized tank capable of reasonable distances between fillings.
The big question about the "hydrogen economy" is how one is going to produce the hydrogen. Pretty much everything else we already know how to do.
Posted by: Tim Worstall | Aug 6, 2005 5:35:50 AM
Ok,
I made an assumption not based on any explicit information. Given that water has free h+ and oh- ions floating around in it, even if few in number and balanced, I assumed that the zinc powder was sufficiently fine to give a surface area/volume ratio which would allow a reaction to take place. It is the only way that the reaction as described makes sense. Maybe I shouldn't have made that assumption, not enough information to justify it. Although as Tim points out, galvanising iron protects the iron because the zinc reacts preferentially, slowing down the irons rusting. Even so, if you drop a lump of zinc into a bucket of water it will be a long long time before you have anything other than a lump of zinc in a bucket of water.
We are still missing something. Anyone local want to ring em up and ask?
Posted by: Chris harper | Aug 6, 2005 5:45:23 AM
Tim, my apologies for not being clear. What I meant was :
Solar energy vapourises water, which drives a steam turbine, which drives a dynamo, which generates electricity, which electrolyses (?) water to oxygen and hydrogen.
There is no magic here: you put solar energy in one end and get chemical energy out at the other, just like with the funky zinc thing. All that matters is how much energy is lost as inefficiencies of the process, and how much you have to spend on the kit to do the job.
It also seems to me that if the original energy source is solar/wind/tidal, and you don't need lots of complicated intermediary products like the zinc thing, then you can probably afford a fairly inefficient process, because the original energy is free.
That being said, if it is feasible to use solar power to generate temperatures of 1200C, it must surely be much easier to use solar power to generate temperatures of 101C to drive the steam turbine, etc. Hence my original question - why isn't electrolysis easier ?
Tim adds: Put that way it makes sense. I agree that it depends completely on the relative efficiencies of each process. That’s something that will play out I’m sure.
The TiO2 process I allude to for generating H2 above seems pretty good as you’ve got a catalyst in there. No concentration of sunlight necessary at all, just TiO2, water and regular sunlight.
Posted by: fFreddy | Aug 6, 2005 7:06:34 AM
You're right, catalysts do great things for efficiency. All the same, I am a bit dubious that we get enough sunlight on the roof to power all the electricals within a house - and more so, of course, for a block of flats. Even assuming there's enough titanium in the world to cover all the roofs (it ain't cheap).
It just seems to me that anything which is going to significantly affect the energy usage of a major industrial nation is going to require some major industrial plant.
Rooftop panels (or rooftop windmills, forsooth) are just feel-good fiddling around the edges. I haven't seen the numbers, but I'll bet they don't stack up. (Without a nice big public subsidy...)
Tim adds: Titanium is expensive, yes, because of the energy required to smelt it. TiO2 is pretty cheap. It’s the dye in white paint for example. A few months ago I ran the numbers. Average insolation onto the roof of a house should be enough to powerthat house, given a reasnably efficient system of collecting and storing that energy. Those mini-windmills in the UK offer about 1/3 of average consumption for about 1,000 pounds.
Posted by: fFreddy | Aug 6, 2005 10:13:23 AM
Tim, you surprise and delight me. I shall have to go and do some research to cure my cynicism. Thank you.
Posted by: fFreddy | Aug 6, 2005 11:48:40 AM
This wouldn't be an example of "New Technologies" helping in reducing greenhouse emissions would it? I thought the EU just told us that that is not the way to go?
Posted by: B's Freak | Aug 7, 2005 12:20:08 AM
Possibly. Now let's tell the EU where to go ...
Posted by: fFreddy | Aug 7, 2005 4:42:35 PM
errm.......so having ploughed my way through all this and not being a chemist, are we going to get a zinc economy or not? And if so how quickly? Anybody?
Tim adds: Don’t buy zinc futures just yet. The inventors think 6-8 years before commercial scale test plant up and running.
Posted by: Mark T | Aug 8, 2005 11:36:57 AM
DK (may I call you DK?) I'm sure the bonds in water are strong, but it doesn't matter what you use to break them, it takes the same amount of energy, whether via electrolysis or via this zinc reaction.
This is not entirely true. Every chemical reaction has a reaction barrier, the energy that it takes to initiate it. Zn will react relatively easily with O, even in the presence of H, since ionic bonds (formed between the Zn and O) are far stronger than the both the covalent and hydrogen bonds that bind H2O.
Zn + H2O = ZnO + H2
This is quite advanced chemistry, but I can go and look up the reaction differentials if you like (I can't remember them, off hand).
Solar energy vapourises water, which drives a steam turbine, which drives a dynamo, which generates electricity, which electrolyses (?) water to oxygen and hydrogen.
What is the point of generating electricity so that you can use electricity to generate electricity (for your electrolysis)? That makes no sense at all especially, as I pointed out before, you are going to use more electricity generating the H2 from electrolysis than you will obtain when burning it.
On a practical basis, you also have the problem of impurities in the water, which will drop the yield of hydrogen in the electrolysis reaction. Unless you purify the water (more energy expenditure).
There is no magic here: you put solar energy in one end and get chemical energy out at the other, just like with the funky zinc thing.
Yes, but what we actually want is electrical energy, not chemical. Using zinc negates the need to consume electrical energy, and thus your yield is higher.
OK, according to the extended PDF article, the heat is generated by a complex collection of mirrors, which refract and focus the light. These reactors are going to be big; this isn't a garden shed set-up.
That being said, if it is feasible to use solar power to generate temperatures of 1200C, it must surely be much easier to use solar power to generate temperatures of 101C to drive the steam turbine, etc. Hence my original question - why isn't electrolysis easier?
And if you are going to use the sun to heat water to turn a turbine, you need to have a constant, and consistant, supply of power. When performing the zinc reaction, you don't because you can stockpile the raw material, i.e. H2 and so feed it in in a constant stream. You have to maintain a consistant level of generation or you screw up the Grid; this is one of the reasons why wind turbines are a horrible, expensive failure that no one, except the lunatic Green fringe, thinks is going to be a viable future for electrical generation.
There is also the question of portability to consider. Part of the neatness of the process is that you can also manufacture zinc batteries. You can't really manufacture H2 batteries and so unless, for instance, your car is going to have a wire attached to the mains, or a significantly better capacitor than we have managed to build so far, they are still going to have to run on hydrocarbons (or similar).
Posted by: Devil's Kitchen | Aug 9, 2005 3:09:08 AM
DK, we are agreeing on the fundamentals, but somehow we are missing each other's points. Clearly, it is my fault for poor communications.
With regard to cars, yes, I agree that hydrogen storage at that scale is not yet solved, so let's leave them aside for now. What I am interested in is energy storage at industrial scales.
You make the point about wind turbines being useless because of their unpredictability - I entirely agree. BUT - if you could store the energy they generate over the course of the day, then release it to the Grid during the hours of peak demand - then they might start to make some sense. (Still be bloody ugly, though.)
Same applies to wave power and, to a lesser extent, tidal power. (Tidal is predictable, it just doesn't come when you want it.)
The key point is that all these "natural" sources of energy are largely an excuse for subsidy hunting - until we solve the problem of energy storage on an industrial scale. At that point, it could become a whole new ball game.
Regarding your detailed points :
I don't think the energy released in forming the ZnO bond is relevant to this - you just have to put the energy back in to break them apart. (I'm looking at hydrogen as the eventual energy store rather than zinc.)
I don't understand your "generating electricity so that you can use electricity to generate electricity, which electrolyses...".
To clarify what I was saying, to me a turbine is a whirly thing with fan blades (like a jet engine) and a dynamo is a whirly thing with magnets and copper wire. I'm only after "generating electricity, which electrolyses..."
Regarding impurities in the water - engineering problem, and I doubt it would be a big one. After all, we've got a whole load of pure steam from driving the turbine. Recondensing some shouldn't be hard.
Posted by: fFreddy | Aug 9, 2005 3:31:24 PM
