Posts Tagged ‘hydrogen’
an interminable conversation 11: Hydrogen?
yeah, hang on a minute
Jacinta: So green hydrogen – what is it, is it real? Does it really have a future? Where, if anywhere, does it fit in that future? It keeps getting put down, it keeps getting talked about, and it seems most experts say, yeah, it’s in the mix, but at a fairly low concentration.
Canto: Good topic – this will allow us to look back at some videos we’ve viewed which have left me scratching my head. So first, on the inestimable Fully Charged podcast, Robert Llewellyn interviewed a clearly Australian Prof, David Cebon…
Jacinta: And this interview received really rave reviews in the comments, I noticed, which surely says something.
Canto: Yes, so let’s try and get our heads around it… and wow, having watched that interview, I feel a bit dumb for having vaguely hyped green hydrogen’s promise, and for being overly skeptical of Elon Musk’s dismissal of hydrogen a few years go – especially in light of the difficulty of compressing and moving the stuff.
Jacinta: So let’s start at the beginning. Prof Cebon is with the Hydrogen Science Coalition (https://h2sciencecoalition.com), and is a professor of mechanical engineering at Cambridge University. He’s the Director of the Centre for Sustainable Road Freight, and he’s co-authored over a hundred papers etc etc, so he’s super-knowledgeable about this stuff, especially when it comes to vehicular transport.
Canto: So Robert started by talking positively about hydrogen fuel cell cars as clean and green – no toxic fumes. But, nowhere to refuel them – and refuelling is one of many issues.
Jacinta: And then it was onto the colours of hydrogen, which I didn’t know about. So you ‘make’ hydrogen in two ways – electrolysing water, that is separating into hydrogen and oxygen by means of an electric current, which is energy-intensive. Pulling the H2O molecules apart isn’t easy. If the electricity you use for this is renewable, that makes ‘green hydrogen’. If that energy isn’t renewable it’s called ‘yellow hydrogen’. Of course, energy out of the grid may be a mix – here in South Australia it’s largely gas and renewables, whereas in the eastern states a lot of it is coal – nasty brown coal in Victoria. And so on.
Canto: And as Prof Cebon points out, using green energy to produce hydrogen, rather than to grid it directly into houses and businesses, might seem a bit odd. He calls it an opportunity cost.
Jacinta: The next main ‘colour’ of hydrogen comes from fossil fuel, particularly gas (mostly methane, CH4). By treating gas with super-hot steam, you can break it down into hydrogen and CO2. That carbon dioxide normally goes into the atmosphere. Some 2% of the world’s carbon emissions comes from producing this sort of ‘grey’ hydrogen, which is used to make ammonia (NH3) for fertiliser, and in the petrochemical industry. That percentage is about as much as aviation uses (though fertiliser is pretty essential). However, if you can ‘carbon capture and storage’ that CO2, then the hydrogen involved becomes lovely blue hydrogen.
Canto: Yes but as the Prof points out, once you’ve stripped the carbon from the methane, the remaining hydrogen isn’t very energy intensive, so you need a lot of methane to make a useful amount of hydrogen. Better to use the methane directly via the grid!
Jacinta: As Prof Cebon says, you need more methane to fuel your economy via hydrogen (around 40% more) than if you just used natural gas directly. All very attractive to the natural gas industry!
Canto: Right – what with the ‘electrify everything’ trend, the gas industry will be worried about its market, so here’s an opportunity – pump up hydrogen. Beware of the fossil fuel industry’s lobbying! And it’s blue hydrogen they’re really after, for financial reasons.
Jacinta: So back to electrolysis, green hydrogen, and efficiency. The electrolysis process is about 75% efficient, but importantly the energy has changed form. Think of energy as either work or heat, and forget kWhs for the moment. It’s work that’s important. You want the energy to produce more work and less heat (as with LED versus incandescent light globes). The combination of the two is the total energy output according to the first law of thermodynamics, or the law of energy conservation. Electricity from your battery produces work (eg in an EV) with very high efficiency. Diesel, petrol and other chemical fuels, including hydrogen, produce a lot of heat. According to the prof, the efficiency of an infernal combustion engine, which is essentially its work to heat ratio, is around 30%. Diesel may get up to maybe 45% but that’s the limit. Electricity can reach 90 to 95% efficiency. Chemical energy apparently runs up against the second law of thermodynamics, which limits the conversion of heat back to work. There’s always going to be a loss.
Canto: Right again. So 25% of the energy used in electrolysis is lost as heat. You have to convert the heat back to electricity via a fuel cell, which also has limited efficiency. And this efficiency reduction is before the energy required for compression, transportation, etc. So it’s all very problematic, though hydrogen has been touted as a miracle energy source since the early days of the nuclear industry.
Jacinta: Yes, and there are plenty of other problems with hydrogen – first, it’s colourless and odourless, and it’s very hard to contain without leaks, being of course the most molecularly tiny element in existence, so to use it as a home fuel would require a massive infrastructural upgrade, and of course it’s highly explosive and generates high NOx emissions when burned in the home – more so than methane. It’s also very inefficient compared to electrified heat pumps, which the prof calculates as about six times more efficient. So why would you use renewable energy in this inefficient way? The industry, according to the prof, is trying to hide this impracticability from the public.
Canto: Professor Cebon is involved with, or maybe heads up, the Hydrogen Science Coalition, which highlights five principles. First, the only acceptable form, in terms of fuel, is green hydrogen, using electrolysis via green energy. Blue hydrogen isn’t clean – being gotten from ‘dirty’ methane, and what Cebon calls fugitive methane, emissions from flaring and venting and leaking, amounts to the total annual carbon emissions of Europe – it’s a huge problem, due partially to the unregulated nature of the gas industry in Russia, the Middle East and elsewhere. Carbon capture and storage, which has been mooted for decades, has gotten nowhere, because – where are the profits in it? No private enterprise would touch it.
Jacinta: The second principle, or project, is to clean up the chemical use of hydrogen in ammonia fertilisers and in the steel and petrochemical industries by preventing the escape of so much of the C02 byproduct from escaping into the atmosphere. Not so much via CCS as by more efficient processing. The third project is to speed up electrification – let’s not pretend that hydrogen is an option for heating homes, for example, or that hydrogen fuel cell vehicles can be competitive with EVs. That battle has already been won.
Canto: Fourth is to rid ourselves of the idea that blending hydrogen into gas for any energy purposes is going to be useful. Hydrogen is a low energy replacement for methane, so you would need much more of the stuff, with all the attendant problems. And fifth and last is that hydrogen can only be used locally – that’s to say, at source. Transporting hydrogen safely is hugely expensive – being very light, many vehicles would be required to transport a sufficient energy load – 16 to 1 compared to diesel, according to our Prof. Not at all practicable.
Jacinta: And apparently hydrogen fuel cell vehicles are much more expensive to run than EVs, requiring replacement parts and so forth. So why are people still touting hydrogen. We’ll look more into that in a future piece.
Canto: Yes, Australia’s ‘Engineering with Rosie’ vodcaster has participated in a webinar for Mission Hydrogen, which sounds ominous, but I’ve heard her being skeptical about the green hydrogen movement, so we’ll see what she has to say.
References
green hydrogen? it has its place, apparently
easy-peasy? don’t be guiled
Canto: So now that Labor has won government in South Australia it’ll be implementing its hydrogen plan pronto, I presume. But so many people seem iffy about hydrogen, I thought we might do another shallow dive on the topic.
Jacinta: Yes, we jointly wrote a piece last June on SA’s hydrogen plan (linked below), and a brief interview today with Andrew ‘Twiggy’ Forrest caught my attention – time to revisit and further our education on the subject.
Canto: Yes, a recent ABC article described Forrest’s ‘green hydrogen hub’ in Gladstone in central Queensland. He’s building the world’s largest electrolyser facility there. We’re talking gigawatts rather than megawatts. He expects – by which he means hopes – that the facility will have the capacity to produce 2 gigawatts (that’s 2000 megawatts) of electrolysers per annum, just for starters.
Jacinta: I’m not sure whether to trust Forrest’s hype, but I like his enthusiasm. He reckons he already has buyers for his electrolysers and that ‘the order list is growing rapidly’
Canto: Interesting – Forrest says that the lack of electrolysers has been a problem for a while, and apparently Australian researchers at the University of Wollongong, associated with a company called Hysata, have achieved a ‘giant leap for the electrolysis industry’, with its ‘capillary-fed electrolysis cells’, which have attained 95% efficiency, up from the previous 75%. This was published in the peer-reviewed journal Nature Communications, so it’s not just hot air.
Jacinta: Apparently electrolysers have been around for quite some time, with very few improvements, so this seems important. The researchers describe their approach thus:
The central challenge was to reduce the electrical resistance within the electrolysis cell. Much like a smart phone battery warming as it charges, resistance wasted energy in a regular cell as well as often requiring additional energy for cooling.
“What we did differently was just to start completely over and to think about it from a very high level,” Swiegers said. “Everyone else was looking at improving materials or an existing design.”
Canto: Reducing electrical resistance – that’s always the key to cheaper and more effective electricity, it seems to me. That was at the heart of the AC versus DC battle, and it’s what has made LED lighting such a vital development.
Jacinta: I still don’t understand LED lighting. Photons instead of electrons, yet still connected to an electric circuit driven by electrons in wires…
Canto: Anyway, returning to hydrogen, there’s a presumably new organisation called the Australian Hydrogen Council, whose website has a frequently asked questions section. The key thing about green hydrogen, or otherwise, is where the electricity comes from to produce electrolysis. To be green, obviously, it needs to be from solar or wind, or hydro. The FAQ section also mentions that the electricity can come from carbon capture and storage, resulting in ‘low to zero carbon emissions’.
Jacinta: Hmmm. We’ll have to do a shallow dive on carbon capture and storage soon. I know that ‘greenies’ are generally highly skeptical, but sometimes I feel a bit skeptical of greenies. Am I allowed to say that?
Canto: A generalised skepticism means looking critically at any scientific claims. But I’ve been thinking about electrolysis, particularly the electrolysis of water, which is key to this clean green hydrogen-producing process, presumably. It’s about ‘lysis’ – splitting, or separating – by means of an electrical current. But to paraphrase Woody Allen, ‘I’m two with science’. Or to put it another way, science is to me like a lover I’m passionate about but can never fully, or even partially, understand…
Jacinta: Well I’ve watched a wee citizen science video about doing electrolysis of water at home. You need, according to these guys, distilled water, nice and pure, and ‘kosher’, non-iodised salt. Mix it together in a heat-resistant beaker, about nine parts water to one part salt, until the salt dissolves, and insert a couple of spoons attached to a nine volt battery into the mix. The salt increases the conductivity of the solution, as pure water isn’t conductive, much. You’ll need an acid, such as vinegar, to neutralise the alkaline solution that results from the experiment. That alkaline solution is essentially sodium hydroxide, NaOH, aka caustic soda or lye, which can cause burns, so home experimenters need to protect themselves accordingly. Then you insert the spoons, each connected to one of the two terminals of the battery, into the beaker. Bubbles of hydrogen and chlorine gas will form, as long as the two spoons are kept separate. Note that inhaling chlorine gas is a v bad idea, so, again, protection. And best to do the experiment outside. So what is happening here? Salt is an electrolyte, an ionically-bonded compound. The ions are what facilitates the transfer of electrical energy. So what we have in the solution are molecules of H, O, Na and Cl, the molecular bonds having been broken by the electrical current. In this home experiment, the hydrogen and chlorine gases escape into the air, but of course the hydrogen will be captured for energy use in the system being developed by Forrest and others.
Canto: Yes the salt water is used as an electrolyte, but different electrolysers will use different electrolytes. The US website energy.gov describes three types of electrolysers being used or considered at the commercial level – polymer electrolyte membrane (PEM), alkaline, and solid oxide. The problems with all these types is cost-effectiveness. For example the solid oxide membranes in that type of electrolyser need to operate at very high temperatures – between 700 and 800°C – to function effectively, though promising work is being done to lower the temperature. From what I can gather, the PEM electrolysers are showing the most promise. This uses a solid plastic electrolyte, and for what it’s worth I’ll quote something about how it works:
- Water reacts at the anode to form oxygen and positively charged hydrogen ions (protons).
- The electrons flow through an external circuit and the hydrogen ions selectively move across the PEM to the cathode.
- At the cathode, hydrogen ions combine with electrons from the external circuit to form hydrogen gas.
- Anode Reaction: 2H2O → O2 + 4H+ + 4e– Cathode Reaction: 4H+ + 4e– → 2H2
Jacinta: As you’ve said, the cost of electrolysers is a major barrier, and I’ve been unable to find out the type of electrolysers Forrest’s company (Green Energy Manufacturing) is going with. I did find out that Twiggy likes to be called Dr Forrest now, having completed a doctorate in Marine science recently. Also, there’s quite a lot of skepticism about his green hydrogen project.
Canto: Yeah, like there was with SA’s big battery… Stop Press –
The electrolysers produced at the GEM facility will partner FFI’s advanced manufacturing capabilities with cutting-edge Polymer Electrolysis Membrane (PEM) technology developed by NASDAQ-listed company Plug Power to deliver a high-purity, efficient and reliable end product.
That’s advertising blurb from the Queensland government, so we’ll have to wait and see. But getting back to the skepticism about hydrogen as an energy source – what gives? Well, according to Rosie Barnes, Australia’s engineering Wonderwoman, the process of creating hydrogen by electrolysis and then burnng it in a full cell is very energy-inefficient compared to direct or battery electrical energy. That’s three compared to one wind turbine, for example. Also hydrogen takes up a lot of space – remember those massive zeppelins?
Jacinta: Not personally.
Canto: Well, another problem with hydrogen is its flammability. The Hindenburg wasn’t the only hydrogen airship that went up in flames. They can replace hydrogen with helium apparently, but that presents another set of problems. In any case, it looks like hydrogen isn’t going to be the silver bullet for green energy, but it will surely be a part of the energy mix, and with technologies for storage and transport being developed and improved all the time, it’ll be interesting to see how and where green hydrogen finds its place.
Jacinta: Yes I’ll certainly be keeping an eye on the projects happening here in Australia, and how the likely change of government at the federal level makes a difference. My feeling is that they’re keeping mum about their energy plans until after the election, but maybe I’m being overly optimistic.
References
https://www.nature.com/articles/s41467-022-28953-x
The Sci Guys: Science at home – electrolysis of water (video)
https://www.energy.gov/eere/fuelcells/hydrogen-production-electrolysis
https://www.sciencedirect.com/science/article/pii/S2589299119300035
https://skepticalscience.com/hydrogen-fuel.html
more on fuel cells and electrolysers
Cross section of a PEMEL(polymer exchange membrane electrolyte?) stack comprising four cells, according to Science Direct
Jacinta: So continuing with Philip Russell’s simple video of a small hydrogen fuel cell (in the previous post), he explains that when the electrolysis process reverses itself, powering the fan, hydrogen is entering the cathode where it reacts with the palladium catalyst. The reaction with palladium is described as complex and weird, so he puts the matter off to a future video. In any case the hydrogen is split, producing electrons and hydrogen ions. Those electrons travel around the circuit which powers the fan, or a light bulb or some other electrical device, and the hydrogen ions travel through/across the PEM, where they react with the electrons in the circuit, and the oxygen, to produce water, which escapes from the anode side.
Canto: So what they’re after in all this is the electrons, in sufficient abundance and in continuous supply to power whatever, without the use of carbon-based fuels. Frankly I’m not even sure how fossil fuels, hydrocarbons etc produce electricity, but hopefully I’ll learn something about this along the way.
Jacinta: You mean how does coal, oil or gas get transformed into high-energy electrons bumped along in a circuit? Yes, we have a lot to learn.
Canto: And how do electrons in a wire make an air-conditioner work? But let’s stick with hydrogen for now. An older video, from 2012, from the excellent Fully Charged series, provides some other insights. I won’t go into too much detail with it, as the fuel cell described is very similar to Russell’s, but it does highlight some problems, at least from 2012. First, the interviewee, James Courtney from Birmingham University, uses the term proton-exchange membrane (PEM) rather than Russell’s PEM – a polymer exchange membrane. They mean the same thing, as the membrane is made of a polymer, and the key is that it’s an ‘electron insulator’, allowing protons to pass through. The polymer is usually nafion, a synthetic polymer created sixty years ago. It’s described as an ionomer for its ionic properties. But the most important thing I learned from Courtney is about the issue of platinum/palladium. It’s very very expensive, and its price is rising. Courtney – nine years ago – was experimenting with solid oxide electrolytes.
Jacinta: From Wikipedia:
A solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte. Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage is the high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues.
Canto: An organisation called Bloom Energy, self-described as ‘a leader in the SOFC industry’, has a bit to say about the technology. So, again we have the negative anode and the positive cathode, and the electrolyte in between which undergoes ‘an electrochemical reaction’…
Jacinta: That’s when the miracle occurs.
Canto: Yes, and this produces an electrical current. So here’s something to think about re electrolytes:
The electrolyte is an ion conductor that moves ions either from the fuel to the air or the air to the fuel to create electron flow. Electrolytes vary among fuel cell types, and depending on the electrolyte deployed, the fuel cells undergo slightly different electrochemical reactions, use different catalysts, run on different fuels, and achieve varying efficiencies.
Does that help?
Jacinta: Yes, it helps to complicate matters.
Canto: So the Bloom Energy website reckons that SOFCs have the best potential for fuel cell technology, and promises they’ll bear fruit in the next six years – instead of the usual five. Here’s their diagram of an SOFC.
Note that they’re using natural gas (methane) in a process called methane reformation, also mentioned by James Courtney. So, not exactly a clean technology, but also, as the illustration mentions, no precious metals, corrosive acids or molten materials.
Jacinta: But apparently this isn’t a hydrogen fuel cell. Barely a mention of hydrogen.
Canto: Yes, the illustration presents oxygen ions reacting with ‘fuel in the fuel cell’ to produce electricity. The cleanness comes from the fact that there’s no combustion, making it more sustainable and of course more green than combustion-based tech. Apart from a partial reduction in greenhouse gases, this tech does away with the emission of harmful sulphur dioxide and nitrogen oxide. And their ‘Bloom box’ fuel cell packs can run on hydrogen, with net zero carbon emissions. They see their technology being well suited to distributed networks and mini-grids, which may provide the power supplies of the future.
Jacinta: We shall see – if we live long enough. Meanwhile let’s look at another video, featuring Dr Stephen Carr, of the H2 Centre, University of South Wales, on how a hydrogen fuel cell works. Eventually it’ll all come together.
Canto: And then fall apart again. This video is more recent than the previous two, but I’m not sure that there have been any new developments in the interval. So Dr Carr presents ‘a demonstration kit of a renewable hydrogen energy storage system’, in which the hydrogen is produced by solar power…
Jacinta: Another magical moment?
Canto: Well, apparently. Anyway, he represents the sun with a lamp – so I suppose it’s a demonstration, not the real thing. The lamp shines on a PV (photovoltaic) panel which produces electricity.
Jacinta: Grrr, they never explain that bit.
Canto: How do you produce annoyance? Bet you can’t explain that either. Anyway, the electricity runs through an electrolyser, which splits water into oxygen and hydrogen, which is stored for times when we can’t directly produce power from the sun. At such times we can run the hydrogen and oxygen through a fuel cell (which seems to operate oppositely to an electrolyser) to produce electrical power. As he says (and this is new) the photons from the lamp (in lieu of the sun) are converted by the panel into electrical energy or power (but I think those are two distinct things). This is of course referring to how solar energy/power works, which is an entirely different thing. We’ll leave that aside for now, along with the big heap of other things.
Jacinta: Yes let’s just focus on what Dr Carr says. The electrical power powers an electrolyser. The electrons are used to drive an electrochemical process which splits water into hydrogen and oxygen. On one side of this electrolyser the water is ‘split into hydrogen’ and on the other side it produces oxygen (magic happens). Then the hydrogen and oxygen can be stored until required, when we can somehow convert these elements into electricity. We can observe, as in the Philip Russell video, bubbles of hydrogen and oxygen forming on either side of the electrolyser, and being collected and stored.
Canto: So we’re again not going to discover the detailed physics/chemistry of all this, but apparently we now have stored power. And this gets run backwards through the fuel cell. In the fuel cell, the released oxygen and hydrogen, in a reverse process to electrolysis (I think), produces pure, apparently drinkable water, and electricity. So the two gases are released from the electrolyser into the fuel cell, oxygen at one electrode, hydrogen at the other, and they’re combined and subjected to electrochemical processes (more magic), producing water and electricity sufficient in this tiny demo model to power a fan or small light. So far, precisely as enlightening as the Philip Russell video.
Jacinta: So next we’re taken to a big electrolyser, something like the new one at Tonsley, South Australia. It uses a stack of some 80 fuel cells to produce stacks of hydrogen. The electrolyser takes in about 50kw of power and produces about 1 kilogram of hydrogen per hour – which means very little to me.
Canto: It’s good that they know this I suppose. So they have an electrolysis stack, and they feed in ‘pure de-ionised water’ – I bet we could do a whole post on that – and apply DC electric power – another post’s worth – which splits the water into hydrogen and oxygen.
Jacinta: When I think of AC and DC I think of Tesla v Edison. History is so much easier than science. I think we need to do a basic course in electricity. But continuing with Dr Carr, for what it’s worth to us, he says that ‘everything else in this unit is gas clean-up’. The hydrogen is ‘de-watered’ to make sure it’s completely dry, and it’s also de-oxygenated, in other words thoroughly purified. Then, for storage, it’s compressed to 200 bar, meaning 200x atmospheric pressure.
Canto: The bar, presumably for barometric pressure, is commonly used in Europe but not accepted by the US, centre of arseholedom with regard to weights and measures.
Jacinta: The trouble is that ‘atmosphere’ for measures of atmospheric pressure, is highly contestable. Anyway, we’ll finish this off next time, for now I’ll just say that Elon Musk is still not much impressed with hydrogen technology, saying that hydrolysis is way too energy-intensive-expensive, that methane or propane etc extraction defeats the purpose, that hydrogen is too light to store easily, that it’s very volatile etc, but maybe it could work for aircraft in the future… So why is so much money being expended on it, in so many countries? Why is it suddenly such a big deal? That’s a ‘mystery’ we’ll have to investigate…
References
https://www.sciencedirect.com/science/article/pii/S0360319919312145
The Hydrogen fuel cell explained, clean energy, by Philip Russell, youtube video
Hydrogen Fuel Cells | Fully Charged, youtube video
https://en.wikipedia.org/wiki/Solid_oxide_fuel_cell
https://www.bloomenergy.com/blog/everything-you-need-to-know-about-solid-oxide-fuel-cells/
https://www.sciencedirect.com/science/article/pii/S1369702103003316
How does a hydrogen fuel cell work, with Dr Stephen Car, video
on fuel cells and electrolysers and other confusions
Canto: So it seems the more you look towards future technologies, the more future technologies there are to look at. Funny that. Two future developments we want to focus on in these next few posts are the graphene aluminium ion batteries being researched and developed in Queensland for the world, and the whole field of green hydrogen technology, a topic we’ll start on today.
Jacinta: Yes and the two key terms which we’re hoping might enlighten us if we can get a handle on them are fuel cell and electrolyser.
Canto: But first, I’ve just watched a brief video, admittedly five years old, a lifetime it seems in nuevo-tech terms, in which Elon Musk, who I’ve generally considered a hero, describes hydrogen fuels as silly, and seems at the end to be lost for words in expressing his contempt for the technology.
Jacinta: Yes, and the video appears to have been unearthed recently because all the comments, mostly well-informed (as far as I can discern) are only months old, and contradict Musk’s claims. But let’s not dwell on that. What is a fuel cell?
Canto: Well, we’re looking at the possibility of fuel cell electric vehicles (FCEVs), which presumably will operate in direct competition with Tesla’s EVs. Interestingly, one of the claimed deficits of EVs is their long charging times, which the new graphene-aluminium ion technology should greatly reduce. If FCEVs become a thing, the ‘old’ battery driven things will become known as BEVs, even before the EV term has really caught on.. Anyway, fuel cells produce electricity. You don’t have to plug them in, according to BMW.com (which may have a bias towards hydrogen in terms of investment). However, they don’t really show how the hydrogen is produced, and their image, shown above, presents a hydrogen tank without explaining where the hydrogen comes from.
Jacinta: Yes, so here’s how BMW.com begins its explanation:
In fuel cell technology, a process known as reverse electrolysis takes place, in which hydrogen reacts with oxygen in the fuel cell. The hydrogen comes from one or more tanks built into the FCEV, while the oxygen comes from the ambient air. The only results of this reaction are electrical energy, heat and water, which is emitted through the exhaust as water vapor. So hydrogen-powered cars are locally emission-free…
Canto: Which explains nothing much so far. Hydrogen reacts with oxygen. How? By reverse electrolysis. What’s that? The name implies splitting by electricity (but in reverse?), but I’d like more detail.
Jacinta: Yeah we’ll have to go elsewhere for that. In the image above you see a battery pack, much smaller than those in EVs, and an electric engine or motor. The BMW site reckons that the generated electricity from the fuel cell can either flow directly to the electric motor, powering the vehicle, or it can go to the battery, called a ‘peak power battery’, which stores the energy until needed by the motor. Being constantly recharged by the fuel cell, it’s only a fraction of the size of an EV battery.
Canto: Okay, that’s the BMW design, but I want the science nitty-gritty. I’ve heard that fuel cells go back a long way.
Jacinta: Yes, and we may need several posts to get our heads around them. I’ll start with the English engineer Francis Thomas Bacon (illustriously named), who developed the first alkaline fuel cell, or hydrogen-oxygen fuel cell, also known as the Bacon fuel cell, in the 1930s. This type of fuel cell has been used by NASA since the sixties. But the Wikipedia article again skips some steps.
Canto: So alkaline is the opposite of acidic, sort of, and car batteries require acid, but I don’t know what the difference is, in electrical terms.
Jacinta: Hopefully all will be revealed. One basic thing I’ve learned is that a fuel cell requires a cathode, an anode (collectively, two electrodes) and an electrolyte. So let’s take this slowly. The cathode is the one from which the conventional current departs – CCD, cathode current departs. Conventional current is defined as the direction of the positive charge. In the case of hydrogen, that’s just protons. The electrons go in the opposite direction. The anode, which maybe I should’ve mentioned first, is the electrode through which a conventional current enters the fuel cell or device. Think ACID, anode current into device. Now, the cathode and anode must be made of particular materials, which presumably relate to the fuel you’re trying to split, or electrolyse.
Canto: Hmmm, I’m wondering if a fuel cell and an electrolytic cell are the same thing, or one is a subset of the other. Apparently not, according to Wikipedia.
For fuel cells and other galvanic cells, the anode is the negative terminal; for electrolytic cells (where electrolysis occurs), the anode is the positive terminal. Made from, with, or by water.
So, shit, what’s a galvanic cell and how does it differ from an electrolytic cell? From the above description, it sounds like an electrolytic cell (anode positive) is the opposite of a fuel/galvanic cell (anode negative). We need to know what electrolysis actually means – not to mention galvanisis. And I believe reverse electrolysis is a thing.
Jacinta: Shit indeed. So at least from the above we know that electrolysis always involves water. Or does it? Okay, a galvanic cell, also known as a voltaic cell (Luigi Galvani, Alessandro Volta) combines two metals and an electrolyte (in Galvani’s case, a frog’s leg). Galvani and others thought the frog, or some other creature, was necessary for the current – ‘animal electricity’ became a thing for a while. Volta showed that this was not the case, though there was much argy-bargy for a while. But enough easy history, we need to tackle tough science.
Canto: So I don’t know if the currently titled hydrogen fuel cells are correctly described as alkaline fuel cells, but there are some videos, such as one by Philip Russell, describing very simple hydrogen fuel cells, driving a small fan. Russell explains the process very carefully, and I’ll go through it myself for my understanding. He has a tiny blue fuel cell connected by two tubes to two glasses of water. In one glass, hydrogen will be collected from one side of the cell, and oxygen from the other side in the other glass. He connects the fuel cell to a small solar panel via two wires, one red one black. He says that ‘to the negative side [holding the black wire] I’m going to connect to the side [of the cell] that produces hydrogen and the positive side [red] I’m going to connect to the side that produces hydrogen’. And now I’m confused. Both sides will produce hydrogen? How? What does that even mean?
Jacinta: In DC circuitry, black is conventionally negative and red positive. The difference between AC and DC may have to be explored because I think it’s relevant to all this nuevo-tech. Now, considering that Russell plugged the wires into opposite sides of the cell and said twice ‘the side that produces hydrogen’, the logical conclusion is that he made a mistake, but I can’t be sure. After all, what does he want to produce other than hydrogen?
Canto: Actually he said that one of the glasses will be collecting oxygen, so clearly he should’ve said oxygen for one of those two sides. But which one? Let’s continue with the video. So he’s connected the solar panel to the cell and he says ‘now we can collect solar energy and turn it into hydrogen and oxygen’. So the mistake hypothesis seems right, and that might have to be clarified with other videos. We plan to look at about a hundred of them, because our skulls are thick. So Russell next takes us inside the fuel cell. The outside is of blue-tinted glass or plastic. Inside we see ‘a perforated metal sheet’ (at least on one side). Apparently this is a hydrogen flow field, which ‘allows the hydrogen gas to escape from the fuel cell’. This again makes little sense to me. How did the hydrogen get in there in the first place? Hopefully all will be explained – or not. Next to, or behind this flow field is an anode consisting of a palladium catalyst. And in a fuel cell, the anode is negative.
Jacinta: According to Britannica, palladium is a type of platinum metal which makes an excellent catalyst:
Because hydrogen passes rapidly through the metal at high temperatures, heated palladium tubes impervious to other gases function as semipermeable membranes and are used to pass hydrogen in and out of closed gas systems or for hydrogen purification.
Canto: Good, so between the two electrodes is our electrolyte, consisting of a polymer electrolyte membrane (PEM) which ‘allows the transfer of the hydrogen gas and hydrogen ions’. Again this isn’t particularly enlightening but we’ll explore it later. Next to the the electrolyte membrane is the cathode (positive), and then comes the oxygen flow field, ‘which allows the oxygen to come in and escape from the fuel cell’. Again unclear.
Jacinta: It’s a start, sort of. We’ll glean what we can from this little video and supplement it from other videos and info sites. So electricity is coming into the fuel cell which breaks down the water coming from the two glass jars. I’m confused, though, about the glass jars and the tubes leading to, or from, the fuel cell. They’re filled with water (which I’m presuming is highly purified) and they’re delivering water to either side of the fuel cell, via these tubes, which are attached, in each of the glasses, to something like a suction cup, which will, it seems, have something to do with gas coming from the fuel and being sent through the tube to the bottom of the glass jars – hydrogen along one tube, oxygen along the other. So the water is presumably being depleted from the jars and the two gasses are being collected at the bottom of the jars, to judge from the look of the setup. But how are these tubes able to deliver water one way and collect gas in the other direction at the same time?
Canto: Haha and we’re only halfway through this teeny video. And we next go to a diagram which again upsets our thinking, as it shows the anode as positive, whereas Wikipedia says the anode is negative in fuel cells. It seems we’re being stumped by nomenclature. What Philip Russell is demonstrating appears to be an electrolytic cell or an electrolyser, but it’s being called a fuel cell. A website from energy-gov, linked below, has a diagram of a fuel cell/electrolyser very similar to Russell’s. They call it an electrolyser. They’re conspiring to confuse us!
Jacinta: Anyway, Russell explains his thingummmy, and I quote: ‘We have, in the middle, this polymer electrolyte membrane [PEM] surrounded by the electrodes, and on either side, the anode and cathodes[!]. When we start, water enters through the anode, and here, when it reaches the cathode and anode [!] things start to happen. The water is broken down into hydrogen ions by the electrons in the battery, and this then produces oxygen gas. The hydrogen ions travel across/through the PEM where they are reacted with electrons and this forms hydrogen gas which escapes through to the cathode side of the fuel cell’.
Canto: Yes, clear as far as it goes. So this is electrolysis he’s talking about isn’t it? Is it really this simple? Probably not, in scaled up versions. Anyway, Russell finishes up by disconnecting his wires from the solar panel and connecting them to a small fan, which immediately starts to function. The fuel cell has reversed, according to Russell, and is producing electricity from H2 and O2.
Jacinta: Yes, the way he presents it, it’s all very simple. But I don’t think so. We’ve scratched the surface of this technology, and informed ourselves in very small part, but there’s a long way to go. We need to struggle on, in our brave, heroic way.
References
https://www.bmw.com/en/innovation/how-hydrogen-fuel-cell-cars-work.html
https://en.wikipedia.org/wiki/Alkaline_fuel_cell
https://en.wikipedia.org/wiki/Galvanic_cell
https://www.britannica.com/science/palladium-chemical-element
https://www.energy.gov/eere/fuelcells/hydrogen-production-electrolysis
a hydrogen energy industry in South Australia?
an artist’s impression of SA’s hydrogen power project
I recently received in the mail a brochure outlining SA Labor’s hydrogen energy jobs plan, ahead of the state election in March 2022. The conservatives are currently in power here. The plan involves building ‘a 200MW hydrogen fuelled power station to provide firming capacity in the South Australian Electricity Market’.
So, what does a ‘hydrogen fuelled power station’ entail, what is ‘firming capacity’ and what does 200MW mean?
A presumably USA site called energy.gov tells me this:
Hydrogen is a clean fuel that, when consumed in a fuel cell, produces only water. Hydrogen can be produced from a variety of domestic resources, such as natural gas, nuclear power, biomass, and renewable power like solar and wind. These qualities make it an attractive fuel option for transportation and electricity generation applications. It can be used in cars, in houses, for portable power, and in many more applications. Hydrogen is an energy carrier that can be used to store, move, and deliver energy produced from other sources.
This raises more questions than answers, for me. I can understand that hydrogen is a clean fuel – after all, it’s the major constituent, molecularly speaking, of water, which is pretty clean stuff. But what exactly is meant by ‘clean’ here? Do they mean ‘carbon neutral’, one of today’s buzz terms? Presumably so, and obviously hydrogen doesn’t contain carbon. Next question, what exactly is a fuel cell? Wikipedia explains:
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from metals and their ions or oxides that are commonly already present in the battery, except in flow batteries. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.
So the planned 200 megawatt power station will use the chemical energy of hydrogen, and oxygen as an oxidising agent, to produce electricity through a pair of redox reactions. Paraphrasing another website, the electricity is produced by combining hydrogen and oxygen atoms. This causes a reaction across an electrochemical cell, which produces water, electricity, and some heat. The same website tells me that, as of October 2020, there were 161 fuel cells operating in the US with, in total, 250 megawatts of capacity. The planned SA power station will have 200 megawatts, so does that make it a gigantic fuel cell, or a fuel cell collective? In any case, it sounds ambitious. The process of extracting the hydrogen is called electrolysis, and the devices used are called electrolysers, which will be powered by solar energy. Excess solar will no longer need to be switched off remotely during times of low demand.
There’s no doubt that the fortunes of hydrogen as a clean fuel are on the rise. It’s also being considered more and more as a storage system to provide firming capacity – to firm up supply that intermittent power sources – solar and wind – can’t always provide. The completed facility should be able to store 3600 tonnes of hydrogen, amounting to about two months of supply. There are export opportunities too, with all this excess supply. Japan and South Korea are two likely markets.
While it may seem like all this depends on Labor winning state government, the local libs are not entirely averse to the idea. It has already installed the nation’s largest hydrogen electrolyser (small, though, at 1.25 MW) at the Tonsley technology hub, and the SA Energy Minister has been talking up the idea of a hydrogen revolution. The $11.4 million electrolyser, a kind of proof of concept, extracts hydrogen gas from water at a rate of up to 480 kgs per day.
The difference between the libs and labor it seems is really about who pays for the infrastructure. Unsurprisingly, the libs are looking to the private sector, while Labor’s plans are for a government-owned facility, with the emphasis on jobs. Their brochure on the planned power station and ancillary developments is called the ‘hydrogen jobs plan’. According to SA’s Labor leader, Peter Malinauskas, up to 300 jobs will be created in constructing the hydrogen plant, at least 10,000 jobs will be ‘unlocked from the $20bn pipeline of renewable projects in South Australia’ (presumably not all hydrogen-related, but thrown in for good measure) and 900+ jobs will be created through development of a hydrogen export industry. He’s being a tad optimistic, needless to say.
But hydrogen really is in the air these days (well, sort of, in the form of water vapour). A recent New Scientist article, ‘The hydrogen games’, reports that Japan is hoping that its coming Olympic and Paralympic Games (which others are hoping will be cancelled) will be a showcase for its plan to become a ‘hydrogen society’ over the next few decades. And this plan is definitely good news for Australia.
Japan has pledged to achieve net-zero greenhouse gas emissions by 2050. However, this is likely impossible to achieve by solar or other established renewables. There just isn’t enough available areas for large scale solar or wind, in spite of floating solar plants on its lakes and offshore wind farms in planning. This is a problem for its hydrogen plans too, as it currently needs to produce the hydrogen from natural gas. It hopes that future technology will make green hydrogen from local renewables possible, but meanwhile it’s looking to overseas imports, notably from Australia, ‘which has ample sunshine, wind and empty space that make it perfect for producing this fuel’. Unfortunately we also have an ample supply of empty heads in our federal government, which might get in the way of this plan. And the Carbon Club, as exposed by Marian Wilkinson in her book of that name, continues to be as cashed-up and almost thuggishly influential as ever here. The success of the South Australian plan, Labor or Liberal, and the growing global interest in hydrogen as an energy source – France and Germany are also spending big on hydrogen – may be what will finally weaken the grip of the fossil fuel industry on a country seen by everyone else as potentially the best-placed to take financial advantage of the green resources economy.
References
Hydrogen Jobs Plan: powering new jobs & industry (South Australian Labor brochure)
https://www.energy.gov/eere/fuelcells/hydrogen-fuel-basics
https://en.wikipedia.org/wiki/Fuel_cell
https://www.eia.gov/energyexplained/hydrogen/use-of-hydrogen.php
‘The hydrogen games’, New Scientist No 3336 May 2021 pp18-19
Marian Wilkinson: The Carbon Club: How a network of influential climate sceptics, politicians and business leaders fought to control Australia’s climate policy, 2020
water on Earth – no problemo
So, as described in my last post, H2O in its various forms is plentiful in our solar system as well as beyond it. But, being more or less scientifically illiterate – despite decades of reading stuff on science – I can’t quite work out how liquid water is so abundant on the Earth’s surface. The story has long been told of water-iced asteroids in the time of the heavy bombardment being responsible, with the major proof being that these carbonaceous chondrite asteroids have, or had, the same signature of heavy (deuterium-rich) water as the water we find on Earth. While this seems a strong argument to me, how did the Earth manage to hold on to that water during those super-heated days?
I’ve looked at this in a previous post, sort of, but I’m still not clear on the atmospheric conditions that brought about our soggy planet (much more soggy during the Mesozoic though). In any case, I’ve recently read that bonafide researchers on this topic have also been mystified about the sheer volume of water on Earth.
Enter a new (to me) hypothesis, published in the Journal of Geophysical Research: Planets a little over a year ago. It argues – and other astrophysicists appear to be impressed by the reasoning and the detailed analysis in the paper – that the water came not only from asteroids but also from the solar nebula.
Solar nebula? Never heard of it, but apparently the concept has a long history. The so-called nebular hypothesis for the formation of our solar system was first proposed by Emanuel Swedenborg in the 1730s, and further elaborated by such luminaries as Immanuel Kant and Pierre-Simon Laplace later in the 18th century. Surprisingly for such an early contention, it has stood the test of time and survives today, though the details are still argued, and there are a few competing hypotheses. In any case, without going into too much detail, a nebula of dust and gas began to form around 4.6 billion years ago, and collapsed in on itself due to gravitational forces, spinning around a newly-formed sun. Out of this material, protoplanets gradually formed.
Water in the Earth’s oceans has approximately the same D/H (deuterium to hydrogen) ratio as that of the above-mentioned asteroidal carbonaceous chondrites, so it has always seemed a safe bet that most if not all water came from those asteroids. Yet the sheer volume of water was still a problem. Jun Wu, the lead author of the recent paper, had this to say about the theoretical situation:
The solar nebula has been given the least attention among existing theories, although it was the predominant reservoir of hydrogen in our early solar system.
What has apparently added credence to the new hypothesis is that samples of hydrogen near the core of the Earth have significantly less deuterium and may fit better with the ratio of hydrogen in the solar nebula. Also the isotopic signatures of the noble gases helium and neon found in the Earth’s mantle fit the signatures of these gases from the time of the solar nebula. The explanation of how the lighter hydrogen found itself drawn to the Earth’s centre, in a process called isotropic fractionation, is provided in the paper, apparently. It’s a very interesting story, if true, and it may have implications for liquid water on habitable-zone exoplanets. That’s to say, there’s no reason for it not to be quite common. Here, to finish, are a couple of thought-provoking comments from members of the research team.
… there’s another way to think about sources of water in the solar system’s formative days. Because water is hydrogen plus oxygen, and oxygen is abundant, any source of hydrogen could have served as the origin of Earth’s water.
Our results suggest that forming water is likely inevitable on sufficiently large rocky planets in extrasolar systems.
References
How did Earth get its water?
https://www.britannica.com/science/solar-nebula
https://ussromantics.com/2018/09/24/a-little-about-the-chemistry-of-water-and-its-presence-on-earth/
a little about the chemistry of water and its presence on Earth
So I now know, following my previous post, a little more than I did about how water’s formed from molecular hydrogen and oxygen – you have to break the molecular bonds and create new ones for H2O, and that requires activation energy, I think. But I need to explore all of this further, and I want to do so in the context of a fascinating question, which I’m hoping is related – why is there so much water on Earth’s surface?
When Earth was first formed, from planetesimals energetically colliding together, generating lots of heat (which may have helped with the creation of H2O, but not in liquid form??) there just doesn’t seem to have been a place for water, which would’ve evaporated into space, wouldn’t it? Presumably the still-forming, virtually molten Earth had no atmosphere.
The most common theory put out for Earth’s water is bombardment in the early days by meteors of a certain type, carbonaceous chondrites. These meteors were formed further out from the sun, where water would have frozen. Carbonaceous chondrites are known to contain the same ratio of heavy water to ‘normal’ water as we find on Earth. Heavy water is formed with deuterium, an isotope of hydrogen containing a neutron as well as the usual proton. Obviously there had to have been plenty of these collisions over a long period to create our oceans. Comets have been largely ruled out because, of the comets we’ve examined, the deuterium/hydrogen ratio is about double that of the chondrites, though some have argued that those comets may be atypical. Also there’s some evidence that the D/H ratio of terrestrial water has changed over time.
So there are still plenty of unknowns about the history of Earth’s water. Some argue that volcanism, along with other internal sources, was wholly or partly responsible – water vapour is one of the gases produced in eruptions, which then condensed and fell as rain. Investigation of moon rocks has revealed a D/H ratio similar to that of chondrites, and also that of Earth (yes, there’s H2O on the moon, in various forms). This suggests that, since it has become clear that the Moon and Earth are of a piece, water has been there on both from the earliest times. Water ice detected in the asteroid belt and elsewhere in the solar system provides further evidence of the abundance of this hardy little molecule, which enriches the hypotheses of researchers.
But I’m still mystified by how water is formed from molecular, or diatomic, hydrogen and oxygen. It occurs to me, thanks to Salman Khan, that having a look at the structural formulae of these molecules, as well as investigating ‘activation energy’, might help. I’ve filched the ‘Lewis structure’ of water from Wikipedia.
It shows that hydrogen atoms are joined to oxygen by a single bond, the sharing of a pair of electrons. They’re called polar covalent bonds, as described in my last post on the topic. H2 also binds the two hydrogen atoms with a single covalent bond, while O2 is bound in a double covalent bond. (If you’re looking for a really comprehensive breakdown of the electrochemical structure of water, I recommend this site).
So, to produce water, you need enough activation energy to break the bonds of H2 and O2 and create the bonds that form H2O. Interestingly, I’m currently reading The Emerald Planet, which gives an example of the kind of activation energy required. The Tunguska event, an asteroid visitation in the Siberian tundra in 1908, was energetic enough to rip apart the bonds of molecular nitrogen and oxygen in the surrounding atmosphere, leaving atomic nitrogen and oxygen to bond into nitric oxide. But let’s have a closer look at activation energy.
So, according to Wikipedia:
In chemistry and physics, activation energy is the energy which must be available to a chemical or nuclear system with potential reactants to result in: a chemical reaction, nuclear reaction, or various other physical phenomena.
This stuff gets complicated and mathematical very quickly, but activation energy (Ea) is measured in either joules (or kilojoules) per mole or kilocalories per mole. A mole, as I’ve learned from Khan, is the number of atoms there are in 12g of carbon-12. So what? Well, that’s just a way of translating atomic mass units (amu) to grams (one gram equals one mole of amu).
The point is though that we can measure the activation energy, which, in the case of molecular reactions, is going to be more than the measurable change between the initial and final conditions. Activation energy destabilises the molecules, bringing about a transition state in which usually stable bonds break down, freeing the molecules to create new bonds – something that is happening throughout our bodies at every moment. When molecular oxygen is combined with molecular hydrogen in a confined space, all that’s required is the heat from a lit match to start things off. This absorption of energy is called an endothermic reaction. Molecules near the fire break down into atoms, which recombine into water molecules, a reaction which releases a lot of energy, creating a chain of reactions until all the molecules are similarly recombined. From this you can imagine how water could have been created in abundance during the fiery early period of our solar system’s evolution.
I’ll end with more on the structure of water, for my education.
As a liquid, water has a structure in which the H-O-H angle is about 106°. It’s a polarised molecule, with the negative charge on the oxygen being around 70% of an electron’s negative charge, which is neutralised by a corresponding positive charge shared by the two hydrogen atoms. These values can change according to energy levels and environment. As opposite charges attract, different water molecules attract each other when their H atoms are oriented to other O atoms. The British Chemistry professor Martin Chaplin puts it better than I could:
This attraction is particularly strong when the O-H bond from one water molecule points directly at a nearby oxygen atom in another water molecule, that is, when the three atoms O-H O are in a straight line. This is called ‘hydrogen bonding’ as the hydrogen atoms appear to hold on to both O atoms. This attraction between neighboring water molecules, together with the high-density of molecules due to their small size, produces a great cohesive effect within liquid water that is responsible for water’s liquid nature at ambient temperatures.
We’re all very grateful for that nature.
exploring oxygen
I’ve been reading David Beerling’s fascinating but demanding book The Emerald Planet, essentially a history of plants, and their contribution to our current life-sustaining atmosphere, and it has inspired me to get a handle on atmospheric oxygen in general and the properties of this rather important diatomic molecule. Demanding because, as always, basic science doesn’t come naturally to me so I have to explain it to myself in great detail to really pin it down, and then I forget. For example, I don’t have any understanding of oxidation right now, though I’ve read about it, and probably written about it, and more or less understood it, many times. Things fall apart, and then we fall apart…
Okay, let me pull myself together. Oxygen is a highly reactive gas, combining with other elements readily in a number of ways. A bushfire is an example of oxidation, in which free oxygen is ‘consumed’ rapidly, reacting with carbon in the dry wood to produce carbon dioxide, among other gases. This is also called combustion. Rust is a slower form of oxidation, in which iron reacts with oxygen to form iron oxide. So I think that’s basically what oxidation is, the trapping of ‘free’ oxygen into other gases or compounds, think carbon monoxide, sulphur dioxide, hydrogen peroxide, etc etc. Not to mention its reaction with hydrogen to form water, that stuff that makes up more than half our bodily mass.
Well, I’m wrong. Oxidation doesn’t have to involve oxygen at all. Which I think is criminally confusing. Yes, fire and rust are examples of oxidation reactions, but so is a reaction between hydrogen and fluorine gas to produce hydrofluoric acid (it’s actually a redox reaction – hydrogen is being oxidised and fluorine is being reduced). According to this presumably reliable definition, ‘oxidation is the loss of electrons during a reaction by a molecule, atom or ion’. Reduction is the opposite. The reason it’s called oxidation is historical – oxygen, the gas that Priestley and Lavoisier famously argued over, was the first gas known to engage in this sort of behaviour. Basically, oxygen oxidises other elements, getting them to hand over their electrons – it’s an electron thief.
Oxygen has six valence electrons, so needs another two to feel ‘complete’. It’s diatomic in nature, existing around us as O2. I’m not sure how that works – if each individual atom wants two electrons, to make eight electrons in its outer shell for stability, why would it join with another oxygen to complete this outer shell, and then some? That makes for another four electrons. Are they now valence electrons? Apparently not, in this stable diatomic form. Here’s an expert’s attempt to explain this, from Quora
For oxygen to have a full outer shell it must have 8 electrons in it. But it only has 6 electrons in its valence shell. Each oxygen atom is actively seeking to get more electrons to complete its valence shell. If no other atoms except oxygen atoms are available, each oxygen atom will try to wrestle extra valence electrons from another oxygen atom. So if one oxygen atom merges with another, they “share” electrons, giving both a full outer shell and ultimately being virtually unreactive.
For a while this didn’t make sense to me, mathematically. Atomic oxygen has eight electrons around one nucleus. Six in the outer, ‘valence’ shell. Molecular oxygen has 16 electrons around two nuclei. What’s the configuration to make it stable? Presumably both nuclei still have 2 electrons configured in their first shells, that makes 12 electrons to make for a stable configuration, which doesn’t seem to work out. Did it have something to do with ‘sharing’? Are the shells configured now around both nuclei instead of separately around each nucleus? What was I missing here? Another expert on the same website writes this:
[The two oxygen atoms combine to] create dioxygen, a molecule (O2) in which both oxygen atoms have 8 valence electrons, so they are happy (the molecule is stable).
But what about the extra electrons? It seems I’d have to give up on understanding and take the experts’ word, and I hate that. However, the Khan academy has come to the rescue. In video 14 of his chemistry series, Khan explains that the two atoms share two pairs of electrons, so yes, sharing was the key. So each atom can ‘kind of pretend’, in Khan’s words, that they have eight valence electrons. And this is a covalent bond, unlike an ionic bond which combines metals with non-metals, such as sodium and chloride.
Anyway, moving on. One of the most important features of oxygen, as mentioned, is its role in water – which is about 89% oxygen by weight. But how do these two elements – diatomic molecules as we find them in our environment – actually come together to form such a very different substance?
Well. According to this video, when H2 and O2, and presumably other molecules, are formed
electrons lose energy to form the new orbitals, the energy gets away as a photon, and then the new orbitals are stuck that way, they can’t undo themselves until the missing energy comes back.
This set me on my heels when I heard it, I’d never heard anything like it before, possibly because photon stuff tends to belong to physics rather than chemistry, though photosynthesis rather undoes that argument…
So, sticking with this video (from Brigham Young University Physics Department), to create water from H2 and O2 you need to give them back some of that lost energy, in the form of ‘activation energy’, e.g by ‘striking a match’. The video turns out to be kind of funny/scary, and it again involves photons. After the explosion, water vapour was found condensing on the inside of the glass through which hydrogen was pumped and ignited…
Certainly the demonstration was memorable (and there are a few of these explosive vids online), but I think I need more theory. Hopefully I’ll get back to it, but it seems to have much to do with the strong covalent bonds that form, for example, molecular hydrogen. It requires a lot of energy to break them.
Once formed, water is very stable because the oxygen’s six valence electrons get two extras, one from each of the hydrogens, while the hydrogens get an extra electron each. The atoms are stuck together in a type of bonding called polar covalent. Oxygen is more electronegative than hydrogen, meaning it attracts electrons more strongly – the negative charge is polarised at the oxygen, giving that part of the molecule a partial negative charge, with a proportional positive charge at the hydrogens. I might explore the effects of this polarity in another post.
The percentage of oxygen in our atmosphere seems stable at 21% – that’s to say, it appears to be the same now as when I was born, but that’s not a lot of time, geologically. The issue of oxygen levels in our atmosphere over geological time is complex and contested, but the usual story is that something happened with the prokaryotic life forms that had evolved in the oceans billions of years ago, some kind of mutation which enabled a bacterial species to capture and harness solar energy. This green mutation, cyanobacteria, gave off gaseous oxygen as a waste product – a disaster for other life forms due to its highly reactive nature. The photosynthesising cyanobacteria, however, multiplied rapidly, oxygenising the ocean. Oxygen reacted with the ocean’s iron, creating layers of rust (iron oxide) on the ocean floor, later visible on land through tectonic forces over the eons. Gradually over time, other organisms evolved that were adapted to the new oxygen-rich atmosphere. It became an energy source, which in turn produced its own waste product, carbon dioxide. This created a near-perfect cycle, as cyanobacteria required CO2 as well as water and sunlight to produce oxygen (and sugar). Other photosynthesising water-based and land-based life forms, plants in particular, emerged. In fact, these life forms had harnessed cyanobacteria as chloroplasts, a process known as endosymbiosis.
I’ll end this bitsy post with the apparent fact, according to this Inverse article, that our oxygen levels are actually falling, and have been for near a million years, and that’s leaving aside the far greater effects due to human activity (fossil fuel burning consumes oxygen and releases CO2). Of course oxygen is very vastly more abundant in the atmosphere than CO2, and the change is minuscule on the overall scale of things (unlike the change we’re making to CO2 levels). It will make much more of a difference in the oceans however, where the lack of dissolved oxygen is creating dead zones. The article explains:
The primary contributor to these apocalyptic scenes is fertilizer runoff from agriculture, which causes algal blooms, providing a great feast for bacteria that consume oxygen. The abundance of these bacteria cause O2 levels to plummet, and if they go low enough, organisms that need it to survive swim away or die.
Just another of the threats to sea-life caused by humans.
the continuing story of South Australia’s energy solutions
In a very smart pre-election move, our state Premier Jay Weatherill has announced that there’s a trial under way to install Tesla batteries with solar panels on over 1,000 SA Housing Trust homes. The ultimate, rather ambitious aim, is to roll this out to 50,000 SA homes, thus creating a 250MW power plant, in essence. And not to be outdone, the opposition has engaged in a bit of commendable me-tooism, with a similar plan, actually announced last October. This in spite of the conservative Feds deriding SA labor’s ‘reckless experiments’ in renewables.
Initially the plan would be offered to public housing properties – which interests me, as a person who’s just left a solarised housing association property for one without solar. I’m in community housing, a subset of public housing. Such a ‘virtual’ power plant will, I think, make consumers more aware of energy resources and consumption. It’s a bit like owning your own bit of land instead of renting it. And it will also bring down electricity prices for those consumers.
This is a really important and exciting development, adding to and in many ways eclipsing other recently announced developments in SA, as written about previously. It will be, for a time at least, the world’s biggest virtual power plant, lending further stability to the grid. It’s also a welcome break for public housing tenants, among the most affected by rising power bills (though we’ll have to wait and see if prices do actually come down as a result of all this activity).
And the announcements and plans keep coming, with another big battery – our fourth – to be constructed in the mid-north, near Snowtown. The 21MW/26MWh battery will be built alongside a 44MW solar farm in the area (next to the big wind farm).
South Australia’s wind farms
Now, as someone not hugely well-versed in the renewable energy field and the energy market in general, I rely on various websites, journalists and pundits to keep me honest, and to help me make sense of weird websites such as this one, the apparent aim of which is to reveal all climate scientists as delusionary or fraudsters and all renewable energy as damaging or wasteful. Should they (these websites) be tackled or ignored? As a person concerned about the best use of energy, I think probably the latter. Anyway, one journalist always worth following is Giles Parkinson, who writes for Renew Economy, inter alia. In this article, Parkinson focuses on FCAS (frequency control and ancillary services), a set of network services overseen by AEMO, the Australian Energy Market Operator. According to Parkinson and other experts, the provision of these services has been a massive revenue source for an Australian ‘gas cartel’, which has been rorting the system at the expense of consumers, to the tune of many thousands of dollars. Enter the big Tesla battery , officially known as the Hornsdale Power Reserve (HPR), and the situation has changed drastically, to the benefit of all:
Rather than jumping up to prices of around $11,500 and $14,000/MW, the bidding of the Tesla big battery – and, in a major new development, the adjoining Hornsdale wind farm – helped (after an initial spike) to keep them at around $270/MW.
This saved several million dollars in FCAS charges (which are paid by other generators and big energy users) in a single day.
And that’s not the only impact. According to state government’s advisor, Frontier Economics, the average price of FCAS fell by around 75 per cent in December from the same month the previous year. Market players are delighted, and consumers should be too, because they will ultimately benefit. (Parkinson)
As experts are pointing out, the HPR is largely misconceived as an emergency stop-gap supplier for the whole state. It has other, more significant uses, which are proving invaluable. Its effect on FCAS, for example, and its ultra-ultra-quick responses to outages at major coal-fired generators outside of the state, and ‘its smoothing of wind output and trading in the wholesale market’. The key to its success, apparently, is its speed of effect – the ability to switch on or off in an instant.
Parkinson’s latest article is about another SA govt announcement – Australia’s first renewable-hydrogen electrolyser plant at Port Lincoln.
I’ve no idea what that means, but I’m about to find out – a little bit. I do know that once-hyped hydrogen hasn’t been receiving so much support lately as a fuel – though I don’t even understand how it works as a fuel. Anyway, this plant will be ten times bigger than one planned for the ACT as part of its push to have its electricity provided entirely by renewables. It’s called ‘green hydrogen’, and the set-up will include a 10MW hydrogen-fired gas turbine (the world’s largest) driven by local solar and wind power, and a 5MW hydrogen fuel cell. Parkinson doesn’t describe the underlying technology, so I’ll have a go.
It’s all about electrolysis, the production of hydrogen from H2O by the introduction of an electric current. Much of what follows comes from a 2015 puff piece of sorts from the German company Siemens. It argues, like many, that there’s no universal solution for electrical storage, and, like maybe not so many, that large-scale storage can only be addressed by pumped hydro, compressed air (CAES) and chemical storage media such as hydrogen and methane. Then it proceeds to pour cold water on hydro – ‘the potential to extend its current capacity is very limited’ – and on CAES ‘ – ‘has limitations on operational flexibility and capacity. I know nothing about CAES, but they’re probably right about hydro. Here’s their illustration of the process they have in mind, from generation to application.
Clearly the author of this document is being highly optimistic about the role of hydrogen in end-use applications. Don’t see too many hydrogen cars in the offing, though the Port Lincoln facility, it’s hoped, will produce hydrogen ‘that can be used to power fuel cell vehicles, make ammonia, generate electricity in a turbine or fuel cell, supply industry, or to export around the world’.
So how does electrolysis (of water) actually work? The answer, of course, is this:
- 2 H2O(l) → 2 H2(g) + O2(g); E0 = +1.229 V
Need I say more? On the right of the equation, E0 = +1.229 V, which basically means it takes 1.23 volts to split water. As shown above, Siemens is using PEM (Proton Exchange Membrane, or Polymer Electrolyte Membrane) electrolysis, though alkaline water electrolysis is another effective method. Not sure which which method is being used here.
In any case, it seems to be an approved and robust technology, and it will add to the variety of ‘disruptive’ and innovative plans and processes that are creating more regionalised networks throughout the state. And it gives us all incentives to learn more about how energy can be produced, stored and utilised.