Archive for the ‘electrolysis’ Category
some more on hydrogen and fuel cells
an electrolyser facility somewhere in the world, methinks
Canto: Our recent post on democracy and public broadcasting has made me turn to PBS, in order to be more democratic, and I watched a piece from their News Hour on clean hydrogen. Being always in need of scientific education, I’ve made this yet another starting point for my understanding of how hydrogen works as an energy source, what fuel cells are, and perhaps also about why so many people are so skeptical about its viability.
Jacinta: Fuel cells are the essential components of hydrogen vehicles, just as batteries are for electric vehicles, and infernal combustion engines are for the evil vehicles clogging the roads of today, right?
Canto: Yes, and Jack Brouwer, of the National Fuel Cell Research Centre in California, claims that fuel cells can be designed to be just as fast as battery engine. Now according to the brief, illustrated explanation, diatomic hydrogen molecules enter the fuel cell (hydrogen occurs naturally in diatomic form, as does oxygen). As Miles O’Brien, the reporter, puts it: ‘A fuel cell generates electricity by relying on the natural attraction between hydrogen and oxygen molecules. Inside the cell, a membrane allows positive hydrogen particles [basically protons] to pass through to oxygen supplied from ambient air. The negative particles [electrons] are split off and sent on a detour, creating a flow of electrons – electricity to power the motor. After their work is done, all those particles reunite to make water, which is the only tailpipe emission on these vehicles.’
Jacinta: He tells us that the oxygen is supplied by ambient air, but where does the hydrogen come from? No free hydrogen. That’s presumably where electrolysis comes in. Also, membranes allows protons to pass but not electrons? Shouldn’t that be the other way round? Electrons are much tinier than protons.
Canto: Very smart. Maybe we’ll get to that. Brouwer talks of the benefits of fuel cells, saying ‘you can go farther’, whatever that means. Presumably, going farther with less fuel, or rather, you can have a lot of fuel on board, because hydrogen’s the lightest element in the universe. Clearly, it’s not so simple. O’Brien then takes us on a brief history of hydrogen fuel, starting with the conception back in 1839, and real-world application in the sixties for the Apollo missions. The Bush administration pledged a billion dollars for the development of hydrogen fuel cell cars in the 2000s, but – here’s the problem – they were producing hydrogen from methane, that infamous greenhouse gas. Ultimately the cars would be emission free and great for our cities and their currently dirty air, but the hydrogen production would be a problem unless they could find new clean methods. And that’s of course where electrolysis comes in – powered by green electricity.
Jacinta: The splitting of water molecules, a process I still haven’t quite got my head around….
Canto: Well the PBS segment next focuses on the sectors in which, according to Brouwer, hydrogen fuel will make a difference, namely air transport and shipping. Rail and heavy vehicle transport too – where the lightness of hydrogen will make it the go-to fuel. It’s energy-dense but it must be compressed or liquefied for distribution. This makes the distribution element a lot more expensive than it is for petrol. So naturally Brouwer and others are looking at economies of scale – infrastructure. The more of these compressors you have, the more places you have them in, the cheaper it will all be, presumably.
Jacinta: Right, as presumably happened with wind turbines and solar panels, and the more people working on them, the more people coming up with improvements… But how do they liquefy hydrogen?
Canto: Hmmm, time for some further research. You have to cool it to horribly low temps (lower than −253°C), and it’s horribly expensive. There was a bipartisan infrastructure bill passed recently which will fund the building of hydrogen distribution hubs around the USA through their Department of Energy. That’s where the action will be. The plan, according to mechanical engineer Keith Wipke of the National Renewable Energy Laboratory, is to do in ten years what it took solar and wind 3 or 4 decades to achieve. That is, to bring hydrogen production costs right down. He’s talking $1 per kilogram.
Jacinta: Okay, remember that in 2032.
Canto: Yeah, I won’t. They’re talking about improving every aspect of the process of course, including electrolysers, a big focus, as we’ve already reported. They’re connecting these electrolysers with renewable energy from wind and solar, and, in the bonobo-science world of caring and sharing, any new breakthroughs will quickly become globalised.
Jacinta: Yeah, and Mr Pudding will win the Nobel Peace Prize…
References
Could hydrogen be the clean fuel of the future? (PBS News Hour video)
green hydrogen? it has its place, apparently
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
what is electricity? part 9 – the first battery
from Wikipedia, etc
Canto: So, going back to the eighteenth century, now. The exploration of electricity was becoming thoroughly fashionable. Lightning was an obviously powerful force that scientists of the day were looking to tame and harness. Most of these modern histories begin with Franklin, but what, or who, turned him on to the subject?
Jacinta: Well of course knowledge and influences developed slowly in the eighteenth century and before. I’ve already spoken of William Gilbert’s De Magnete, written some 150 years before Franklin’s work. Gilbert posited that the Earth itself was essentially a gigantic magnet, with an iron core, which was pretty clever in 1600. He studied static electricity, using amber, and called its effects an electric force, the first modern usage. He was one of the first modern experimentalists, undervalued in his own time, most unfortunately by Francis Bacon, who contributed so much to the development of new scientific methods.
Canto: The 1600s were important in Britain, of course, the period of their Scientific Enlightenment, but one of the most intriguing and brilliant experimenters upon electrostatics in that century was the German polymath Otto von Guericke. His work on vacuums and static electricity in the mid 17th century found its way to England and inspired Robert Boyle to experiment in these fields. But no great breakthroughs occurred, at least for electricity, and no real attempts were made to mathematise electrical concepts until the eighteenth and nineteenth centuries.
Jacinta: Yes, we won’t dwell for too long on these pioneers (famous last words), but J L Heilbron’s 1979 book Electricity in the 17th and 18th centuries: a study of early modern physics, much of which is available online, should guide us towards the advances made by Volta and the nineteenth century mathematisers, notably Maxwell.
Canto: Yes, Heilbron divides the physics of this period into three stages, the first, before 1700, was a relatively amateur, narrow form of neo-Aristotelian systemising (pace Gilbert), and the second involved new discoveries and experiments treated without systematic quantising, which gave way to a more modern, mathematical third stage leading to new discoveries and inventions, such as the battery, just at the end of the 18th century.
Jacinta: We’ve mentioned triboelectric effects in an earlier post. These were the first static effects, between all sorts of different materials, experimented with by scientific pioneers such as Newton and many others. The enormous variety of these effects were, and still are, difficult to quantise. Why was their attraction in some cases and repulsion in others? In fact, ACR, the attraction-contact-repulsion process, came gradually to be recognised, but with no understanding of atoms and particles, or elements in the modern sense, little sense could be made of it.
Canto: There were some attempts to characterise the phenomenon, which was considered a fluid in those early days. In 1733 the French chemist Charles DuFay, one of many electrical experimenters of the time, divided these fluids into two types, vitreous and resinous – the positive and negative forms of today, sort of. Perhaps he was trying to define an attracting and a repelling force.
Jacinta: Effluvia was in the air at that time… ‘particles of electrical matter, which effect attraction and repulsion either by direct impact or by mobilising the air’, to quote Heilbron. But I should mention here the work of Stephen Gray, one of those marvellous upwellers from the lower classes with great practical skills and an experimental spirit, who, like Newton, built his own telescope, with which he made discoveries about sunspots and other things. An obviously alert observer, he noted that electricity could be conducted over distances in various substances, while other substances, such as silk, damped down the effect, acting as insulators. These discoveries were of vital importance, but Gray is probably the most underrated and unrecognised of all the electrical pioneers.
Canto: With the ‘discovery’ of the Leyden jar in 1745 the idea of electricity as a fluid, or two fluids, was laid to rest. This instrument, the key components of which were a jar of glass with metal sheets attached to its inner and outer surfaces, and ‘a metal terminal projecting vertically through the jar lid to make contact with the inner foil’ (Wikipedia), was the first type of capacitor, though it took time for their storage capacity, and those of other devices, to be quantised. Today it’s understood that these early Leyden jars could be charged to as much as 60,000 volts.
Jacinta: Another important early device was called an electrophore, or electrophorus, first invented in 1762 and later improved by Alessandro Volta. These instruments, and the increasing realisation throughout the eighteenth century that this mysterious force, substance or capacity called electricity was a Big Thing, with enormous potential, kept interest in the phenomenon bubbling along.
Canto: An electrophore typically consists of a plastic plate, which won’t conduct electricity, connected to a metal conducting disc with an insulating handle. There are some useful demonstration videos of this, and I’m describing one. If you rub the plastic with some silk cloth, this will, as we now know, transfer electrons from the silk to the plastic, giving it a negative charge (the triboelectric effect). Placing the metal disc on the plastic will not enable too much transfer of electrons, or electron flow. It will in fact cause a polarisation in the disc, positively charging it on the side facing the plastic, and negatively charging it on its opposite side, due to like charges repelling, though this wasn’t known in Volta’s time.
Jacinta: The plastic plate, or sheet, has become a dielectric, I think, which is a pretty complicated concept, involving dielectric constants and relatively complicated mathematical formulae, but for our current purpose (and theirs in the 18th century) this electrophore was a useful demonstrator of static electricity. The metal plate was on balance neutral in charge, but in a sense magnetised, with a negative charge on its upper side, which could be grounded at a touch – causing a spark. Being replaced on the plastic, it could again have its charges separated, a cycle which could be endlessly repeated in theory, though not in practice – due ultimately to the second law of thermodynamics, perhaps.
Canto: So, the battery. It was a term coined by Franklin, giving a sense of overwhelming power, though what he created in connecting Leyden jars in an array was a capacitor.
Jacinta: In fact even one Leyden jar is a capacitor. So what he created was a battery of capacitors, though not quite a supercapacitor. I think.
Canto: Volta is famously supposed to have arrived, in a roundabout way, at the construction of an effective battery due to his dispute with a soon-to-be-former friend Louis Galvani (as described in part 4 of this series), and the dispute led him to further experiments. He came to realise that the reason Galvani’s dead frogs were ‘reanimated’ by electricity had to do with the wires being used, and the chemistry of the frogs.
Jacinta: And meanwhile this ‘reanimation’ business became popularised by Galvani’s nephew, Giovanni Aldini, among others, with popular displays and discussions which led to Mary Shelley’s Frankenstein.
Canto: And meanwhile again, Volta experimented with different wires, including zinc and silver, and with moisture, because he noticed that wetness had an electrifying effect. He soon found that these wires of silver and zinc, connected in a series of water containers, increased the electric effect. Further experimentation with silver and zinc discs, separated by cardboard saturated in salt water, enhanced the effect – the more discs, the stronger the effect. And this effect was permanent (more or less). A battery in the modern sense.
Jacinta: In effect. So voltage is electric potential, as we keep saying. So it’s there even when the battery isn’t connected to anything, a storage device which provides electrical flow when connected. And that potential is measurable, as in a 1.5v battery. Current is the actual flow, which is often quite small, especially in Volta’s original pile, though he was able to build a potential, or voltage of up to 20v. The key to an effective battery, I think, is to get as much current per volt as possible. That’s current flowing steadily, reliably and safely over time. A typical lithium ion phone battery of 3.7 volts delivers between 100 and 400 milliamps of current, whereas Volta’s pile will get you not much more than 1/2 of a milliamp of steady flow. And by the way, why did salt enhance the electrical effect?
Canto: That has to do with with the ionisation of the salt, which when dissolved in water splits into positively charged sodium ions and negatively charged chlorine ions. Sending a current through the water will drive the chlorine ions to the positive terminal and the sodium ions to the negative terminal. This creates a bridge of ions, somehow.
Jacinta: Yeah, great explanation. And apparently one of the most interesting features of Volta’s weak battery, or voltaic pile, at the time was its use in separating H2O into hydrogen and oxygen. This new chemical power – electrolysis – particularly interested Humphrey Davy in England. He proceeded to create the largest battery of the age at the Royal Institution, using it to isolate a large number of elements for the first time, including sodium, calcium, potassium, magnesium, boron and strontium. That was in the first decade of the 19th century – and electricity was really coming of age.
References (just some)
How Volta Invented the First Battery Because He Was Jealous of Galvani’s Frog (video – Kathy loves physics)
https://sciencing.com/salt-water-can-conduct-electricity-5245694.html
https://en.wikipedia.org/wiki/Humphry_Davy
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