an autodidact meets a dilettante…

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Archive for the ‘electricity’ Category

an interminable conversation 8: eddy currents, Ampere’s Law and other physics struggles

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easy peasy

Canto: So we were talking about eddy currents, but before we get there, I’d like to note that, according to one of the various videos I’ve viewed recently, this connection between electricity and magnetism, first observed by Faraday and Henry, and brilliantly mathematised by James Clerk Maxwell, has transformed our human world perhaps more than any other discovery in our history. I think this is why I’m really keen to comprehend it more thoroughly before I die.

Jacinta: Yeah very touching. So what about eddy currents?

Canto: Okay, back to Wikipedia:

Eddy currents (also called Foucault’s currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday’s law of induction or by the relative motion of a conductor in a magnetic field. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor.

Jacinta: Right. All is clear. End of post?

Canto: Well, this ‘perpendicular’ thing has been often referred to. I’ll steal this Wikipedia diagram, and try to explain it in my own words.

So, the eddy currents are drawn in red. They’re induced in a metal plate (C)…

Jacinta: What does induced actually mean?

Canto: That’s actually quite a difficult one. Most of the definitions of electrical induction I’ve encountered appear to be vague if not circular. Basically, it just means ‘created’ or ‘produced’.

Jacinta: Right. So, magic?

Canto: The fact that an electric current can be produced (say in a conductive wire like copper) by the movement of a magnet suggests strongly that magnetism and electricity are counterparts. That’s the central point. That’s why we refer to electromagnetism, and electromagnetic theory, because the connections – between the conductivity and resistance of the wire and the strength and movement of the magnet (for example it can be made to spin) will determine the strength of the electric field, or the emf, and all this can be calculated precisely via an equation or set of equations, which helps us to use the emf to create useful energy.

Jacinta: Okay, so this metal plate is moving, and I’m guessing V stands for velocity. The plate is a conductor, and the nearby magnet (N – that’s the magnet’s north pole) produces, or induces, a magnetic field (B) – or it just has a magnetic field, being a magnet, and this creates a current in the plate.

Canto: Which is perpendicular to the magnetic field, because what causes the current in the plate is the movement of electrons, which can’t jump out of the plate after all, but move within the plane of the plate. And the same would go for a wire. There’s also the matter of the direction, within the plane, of the current – clockwise or anticlockwise? And many other things beyond my understanding.

Jacinta: Would it help to try for a historical account, going back to the 18th century – Franklin, Cavendish, even Newton? The beginning of the proper mathematisation of physical forces? I mean, all I wanted to know was how an induction stovetop worked.

Canto: That’s life – you wonder why x does y and you end up reflecting on the origin of the universe. I’ve looked at a couple of videos, and they explain well enough what happens when a magnet goes inside an electrified coil, but never really explain why. But let’s just start with Faraday. He was a great experimenter, as they all tell me, but not too much of a mathematician. Faraday wasn’t the first to connect electricity with magnetism, though. H C Ørsted was the first, I think, to announce, and presumably to discover, that an electric current flowing through a wire produced a magnetic field around it. That was around 1820, which dates the first recognised connection between electricity and magnetism. The discovery was drawn to the attention of Andre-Marie Ampère, who began experimenting with, and mathematising, the relationship. Here’s a quote from Britannica online:

Extending Ørsted’s experimental work, Ampère showed that two parallel wires carrying electric currents repel or attract each other, depending on whether the currents flow in the same or opposite directions, respectively. He also applied mathematics in generalizing physical laws from these experimental results. Most important was the principle that came to be called Ampère’s law, which states that the mutual action of two lengths of current-carrying wire is proportional to their lengths and to the intensities of their currents.

Jacinta: That’s interesting – what does the mutual action mean? So we have two lengths of wire, which could be flowing in the same direction, in which case – what? Do they attract or repel? Presumably they repel, as like charges repel. But that’s magnetism, not electricity. But it’s both, as they were starting to discover. But how, proportional to the lengths of the wire? I can imagine that the intensity of the currents would be proportional to the degree of attraction or repulsion – but the length of the wires?

 

Canto: You want more bamboozlement? Here’s another version of Ampère’s law:

The integral around a closed path of the component of the magnetic field tangent to the direction of the path equals μ0 times the current intercepted by the area within the path.

\int \mathrm{B} \cdot \mathrm{d} \mathrm{l}=\mu_{o} I
Jacinta: Right. Why didn’t you say that before? Seriously, though, I do want to know what an integral is. I’m guessing that ‘tangent to’ means ‘perpendicular to’?
Canto: Not quite. Forget the above definition, though it’s not wrong. Here’s another definition:
The magnetic field created by an electric current is proportional to the size of that electric current with a constant of proportionality equal to the permeability of free space.
Jacinta: No, sorry, that’s  meaningless to me, especially the last bit.

Canto: The symbol in in the equation above, (μ0), is a physical constant used in electromagnetism. It refers to the permeability of free space. My guess is that it wasn’t defined that way by Ampère.

Jacinta: I understand precisely nothing about that equation. Please tell me what an integral is, as if that might provide enlightenment.

Canto: It’s about quantifying areas defined by or under curves. And a tangent – but let’s not get into the maths.

Jacinta: But we have to!

Canto: Well, briefly for now, a tangent in maths can sort of mean more than one thing, I think. If you picture a circle, a tangent is a straight line that touches once the circumference of the circle. So that straight line could be horizontal, vertical or anything in between.

Jacinta: Right. And how does that relate to electromagnetism?

Canto: Okay, let’s return to Ampère’s experiment. Two parallel wires attracted each other when their currents were running in the same direction, and repelled each other when they were running in the opposite direction. It’s also the case – and I don’t know if this was discovered by Ampère, but never mind – that if you coil up a wire (carrying a current), the inside of the coil acts like a magnet, with a north and south pole. Essentially, what is happening is that the current in a wire creates a magnetic field around it, circling in a particular direction – either clockwise or anti-clockwise. The magnetic field is ‘stronger’ the closer it is to the wire. So there’s clearly a relationship between distance from the wire and field strength. And there’s also a relationship between field strength and the strength of the current in the wire. It’s those relations, which obviously can be mathematised, that are the basis of Ampère’s Law. So here’s another definition – hopefully one easier to follow:

The equation for Ampère’s Law applies to any kind of loop, not just a circle, surrounding a current, no matter how many wires there are, or how they’re arranged or shaped. The law is valid as long as the current is constant.

That’s the easy part, and then there’s the equation, which I’ll repeat here, and try to explain:

\int \mathrm{B} \cdot \mathrm{d} \mathrm{l}=\mu_{o} I
So, that first symbol represents the integral, and B is the magnetic field. Remember that the integral is about the area of a ‘loop’, so the area of B, multiplied by the cosine of theta (don’t ask) with respect to distance (d), is equal to a constant, (μ0), multiplied by the current in the loop (I).
Jacinta: Hmmm, I’m almost getting it, but I’ve never really met trigonometry.
Canto: Well the video I’m taking this from simplifies it, perhaps: ‘the total magnetic field along the loop is equal to the current running through the loop times a constant number’. So, it’s an equation of proportionality, I think. And the constant – mu0, aka the magnetic constant – has a numerical value which I won’t spell out here, but it involves pi and newtons per amps squared.
Jacinta: So you’ve used a ‘crash course physics’ video for the last part of this conversation, which is useful, but assumes a lot of knowledge. Looks like we may have to start those videos almost from the beginning, and learn about trickonometry, and integers, and so much els
Canto: ……..
References
https://web.iit.edu/sites/web/files/departments/academic-affairs/academic-resource-center/pdfs/Amperes_law.pdf
https://en.wikipedia.org/wiki/Integral
https://www.sciencefacts.net/amperes-law.html

Written by stewart henderson

August 30, 2022 at 7:56 pm

An interminable conversation 6: trying to understand inductive cooking.

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the guts of an induction cooker, I believe

Canto: So, with all the fuss and excitement about renewables, we should continue the near impossible task of trying to get our heads around electricity, never mind renewable sources of electricity. It’s still electrickery to me. For example, Saul Griffith in The Big Switch recommends inductive electric stoves as a replacement for gas, which many swear by because they appear to heat your pot immediately, or at least very quickly compared to those old ring electric heaters…

Jacinta: Yes, but as Griffith says in that book, you can tell the gas isn’t too efficient because you feel yourself getting hot when you’re near the stove. That’s heat that isn’t going into the pot. Apparently that doesn’t happen with inductive electricity, which heats the pot just as rapidly if not more so, but almost nothing’s ‘wasted’ into the surrounding air.

Canto: Unless you like to feel toasty warm in the kitchen. Anyway we’re talking about induction cooktops,to give them their proper name, apparently. The old electric cooktops had those coils, and they’re what we grew up with. Here’s a summary from the Forbes website:

Also known as radiant cooktops, electric cooktops offer centralized heat. Electric cooktops have an electrical current that flows through a metal coil underneath the glass or ceramic surface. The coil becomes hot and starts glowing due to the electrical resistance. It will transfer its heat through the glass using infrared energy. This means the burner holding your pot or pan is the one that gets hot. Your food is then cooked by the transfer of heat between the cooktop and the pot. There is residual heat for an undetermined amount of time with electric cooktops, which is why these ranges tend to have an indicator light letting you know that the burner is still warm.

Jacinta: Metal coils under glass or ceramics…? As I recall, they were just coils, not under anything. They were grey. But maybe they were ceramic, with metal embedded within, or on the underside. I wish I was the type who pulled things apart to see how they worked, like geeky kids. And wtf is ‘infrared energy’? As far as I remember, the coils turned visible red when hot, not invisible infrared.

Canto: You see the red light but you feel the infrared heat. The heat you feel from the sun is in the non-visible part of the spectrum – the infrared and beyond. On the other side of the visible spectrum is the ultraviolet and beyond. I think.

Jacinta: So which side has the long wavelengths and which side has the short? – not that this would mean much to me.

Canto: Infrared radiation is about longer wavelength, lower frequency waves than visible light, and ultraviolet radiation is higher frequency and shorter wavelengths. So they bookend invisible light, if you will. But the longest wavelength, lowest frequency waves are radio waves, followed by microwaves, while the highest frequency, shortest wavelength radiation is gamma rays. Whether there are forms of radiation beyond these ends of the spectrum, I don’t know.

Jacinta: I’ve heard of gravitational waves, which were only detected recently. What about them?

Canto: They can have almost infinitely long wavelengths apparently. So to speak. Obviously if they were ‘infinitely’ long, if that’s even meaningful, they’d be undetectable. But let’s get back down to earth, and the most useful energy. Here’s how the Red Energy website describes induction cooktops:

Basically, a standard electric or gas cooktop transfers heat (or conducts heat) from the cooktop to the pot or pan. Whereas, an induction cooktop ‘switches on’ an electromagnetic field when it comes into contact with your pot or pan (as long as the cookware contains a ferrous material like iron or steel). The heat comes on fast and instantly starts cooking the contents.

Jacinta: Okay that explains nothing much, as I don’t know, really, how an electromagnetic field works (still stupid after all these years). As to ferrous cookware, I didn’t realise you could use anything else.

Canto: Well the same website says that, given the speed of heating, you might need to upgrade to cookware that can take the stress, so to speak. As to the electromagnetic field thing, Red Energy doesn’t really explain it, but the key is that an electromagnetic field doesn’t require the heating of an element – those coily things.

Jacinta: They’ve eliminated the middle man, metaphorically speaking? I’m all in for eliminating men, even metaphorically.

Canto: Thanks. So I’m trying to get my head around this. I need to delve further into the meaning of this magical, presumably infrared, heat. The essential term to explore is electromagnetic induction, and then to join that understanding to the practical aspects, yer everyday cooking. So this goes back to the working-class hero Michael Faraday, and the Scottish hero J C Maxwell, which will be fun, though of course I’m not at all nationalistic, but…

Jacinta: Canto isn’t a particularly Scottish name is it?

Canto: My real name is Camran Ciogach Ceannaideach, but I prefer a simpler life. Anyway electromagnetic induction has a great variety of applications, but this is the ultimate, i.e Wikipedia, definition:

Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic field.

Jacinta: None the wiser. What’s an electromotive force?

Canto: Called emf, it’s ‘the electrical action produced by a non-electrical source, measured in volts’. That’s also Wikipedia. So a non-electrical source might be a battery (which is all about chemistry) or a generator (all about steam in industrial revolution days -creating mechanical energy).

Jacinta: So the infernal combustion engine somehow converts petrol into mechanical energy? How does that happen?

Canto: Off topic. This is really difficult stuff. Here’s another Wikipedia quote which might take us somewhere:

In electromagnetic induction, emf can be defined around a closed loop of conductor as the electromagnetic work that would be done on an electric charge (an electron in this instance) if it travels once around the loop.

Jacinta: Right, now everything’s clear. But seriously, all I want to know is how to get rid of that middle man. We were talking abut cooking, remember?

Canto: So emf is also called voltage, or measured in volts, which I seem to recall learning before. Anyway, nowadays electromagnetic induction is everywhere – for example that’s how money gets removed from your bank account when you connect those cards in your wallet to those machines in the shop.

Jacinta: So they’re zapping your card, sort of?

Canto: I’ve looked at a few sites dealing with electromagnetic induction, and they all give me the same feel, that it’s like weird magic. I suppose because they explain how it works but not why.

Jacinta: Shut up and calculate?

Canto: Anyway, induction cooking has been around for more than a century, but it’s really catching on now. They always say it’s more direct, because it doesn’t involve heating an element.

Jacinta: Don’t you know it’s magic?

Canto: No, it’s magnetic. Which explains nothing. But let me try another website, this time Frigidaire:

Induction cooktops heat pots and pans directly, instead of using an electric or gas-heated element. It boils water up to 50 percent faster than gas or electric, and maintains a consistent and precise temperature. The surface stays relatively cool so spills, splatters and occasional boil-overs don’t burn onto the cooktop, making clean-up quick and easy…. Induction cooking uses electric currents to directly heat pots and pans through magnetic induction. Instead of using thermal conduction (a gas or electric element transferring heat from a burner to a pot or pan), induction heats the cooking vessel itself almost instantly….. An electric current is passed through a coiled copper wire underneath the cooking surface, which creates a magnetic current throughout the cooking pan to produce heat. Because induction doesn’t use a traditional outside heat source, only the element in use will become warm due to the heat transferred from the pan. Induction cooking is more efficient than traditional electric and gas cooking because little heat energy is lost. Like other traditional cooktops, the evenly heated pots and pans then heat the contents inside through conduction and convection…. Important: For induction to work, your cookware must be made of a magnetic metal, such as cast iron or some stainless steels.

Jacinta: So I’m not sure if that gets closer to an explanation, but what’s surely missing is how magnetism, or a magnetic current, creates heat. It doesn’t use an ‘element’, but it must use something. I know that heat is energy, essentially, and presumably an electric current is energy, or force, like emf, which is also energy…

Canto: Yes it’s very confusing. The Wikipedia article gets into the maths fairly quickly, and when it describes applications it doesn’t mention cooking… Hang on, it takes me to a link on induction cooking. So here’s a definition, similar to the Frigidaire one, but a little more concise. Something to really zero in on:

In an induction stove (also “induction hob” or “induction cooktop”), a cooking vessel with a ferromagnetic base is placed on a heat-proof glass-ceramic surface above a coil of copper wire with an alternating electric current passing through it. The resulting oscillating magnetic field wirelessly induces an electrical current in the vessel. This large eddy current flowing through the resistance of a thin layer of metal in the base of the vessel results in resistive heating.

I’ve kept in the links, which I usually remove. For our further education. So it’s the resistance of the metal base of the pan that produces heat. Something like incandescent light, which is produced through the resistance of the tungsten filament, which makes it glow white (this was a light bulb moment for me). So you really have to use the right cookware.

Jacinta: Thanks for the links – yes, the key is that ‘resistive heating’, also called Joule heating. James Joule, as well as Heirnrich Lenz, independently, found that heat could be generated by an electric current, and, by experimental testing and measurement, that the heat produced was proportional to the square of the current (which is basically the emf, I think), multiplied by the electrical resistance of the wire. So you can see that the wire (or in cooking, the pot) will heat more readily if it has a high electrical resistance. This can be stated in a formula: , where P is the heating power generated by an electrical conductor (measured usually in watts), I is the current, and R is the resistance.

Canto: So we’ve made progress, but it’s the relation of magnetism to electricity – that’s what I don’t get, and that’s the key to it all. I think I understand that an electric current creates a magnetic field – though not really – and I get that an alternating current would induce an oscillating magnetic field, I think, but is this just observation without understanding? That electricity and magnetism are connected, so just shut up and calculate as you say?

Jacinta: So how, and why a high frequency alternating current creates a dynamic field, that’s what we’re trying to understand. And what’s an eddy current?

Canto: I think we’ve had enough for now, but we’re getting there….

Written by stewart henderson

August 27, 2022 at 5:20 pm

an interminable conversation 5: the RET, Mike Cannon-Brookes, and Big Gas issues

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Jacinta: So I’ve heard of this thing called the Renewable Energy Target (RET) – in fact I first heard about it years ago but I’ve paid little attention. Tell me more.

Canto: There’s a government website, the Clean Energy Regulator site, which purports to explain everything. Here’s the briefest statement about it:

The Renewable Energy Target is an Australian Government scheme designed to reduce emissions of greenhouse gases in the electricity sector and encourage the additional generation of electricity from sustainable and renewable sources.

Of course they have much more to say, in positive-speak, about it all, but a wee footnote at the bottom caught my attention:

In June 2015, the Australian Parliament passed the  Renewable Energy (Electricity) Amendment Bill 2015. As part of the amendment bill, the Large-scale Renewable Energy Target was reduced from 41 000 GWh to 33 000 GWh in 2020 with interim and post-2020 targets adjusted accordingly.

I believe the ultra-conservative Tony Abbott was PM in 2015, and the Fossils were calling the shots, as Marian Wilkinson’s The Carbon Club relates. Anyway, it’s a certificate system based on megawatt hours of power generated, and the rather pathetic target was apparently reached, based on approvals of large solar and wind installations, in the second half of 2019.

Jacinta: That’s something perhaps, but the IPCC wasn’t particularly impressed. The Clean Energy Council’s website, Ecogeneration, has boosted the achievement, describing the RET as ‘the most successful emissions reduction policy of all time for Australia’s electricity system’. But it hasn’t had any competition! And ominously, Kane Thornton, CEO of the Clean Energy Council, is quoted as saying ‘the industry doesn’t need new subsidies, we just need certainty’, etc etc, which contradicts everything I’ve heard from Saul Griffith, Mike Cannon-Brookes and others… we’ve been subsidising the fossil fuel industry forever, haven’t we? It’s rebuilding our manufacturing base that needs subsidising. Renewable energy has already become the cheaper option, but we have no EV manufacturing here and only one PV manufacturer.

Canto: Interesting Mike Cannon-Brookes interview in the Financial Review, which introduces the term ESG to me. This stands for Environmental, Social and Governance, perhaps in that order, as factors to be considered in any investment. Which all sounds v positive. And he’s very positive about ESG, which is a positive thing.

Jacinta: Yeah, apparently he’s a billionaire. How the fuck do people become billionaires? Why is it ever allowed?

Canto: Yeah, obviously it’s not just about working hard, like the Congolese in the diamond mines, and various slave populations over the centuries, whose only reward was death. Nature just ain’t fair. Herr Cannon-Brookes is co-founder of a company called Atlassian, which I’ve never heard of. Nor have I heard of their major products, such as Jiro and Trello, which are used by ‘teams’, but I don’t think they play soccer.

Jacinta: Sounds like they’re in the business of business, which is certainly none of our business.

Canto: Yeah, it’s probably all about digital environments. We’re about 40 years out of date. We need to stop reading books, paper is so 20th century.

Jacinta: Anyway, getting back to renewable energy …

Canto: Well this interview with Cannon-Brookes, he sounds pretty sincere, for a billionaire. They’re just people I suppose. If a bit weird. He’s very positive about renewables, and running his business that way, and pretty honest about the issues – like offloading the problem onto others, as he admits to having done, and facing that issue squarely. You know, like Australia exports coal and gas, and doesn’t take responsibility for the emissions. Like Norway.

Jacinta: They don’t have to take responsibility, the way the current system works. Apparently, as of July 2020, Australia became the world’s biggest gas (LNG) exporter, overtaking Qatar. That’s from the Climate Council. It’s hard to keep track of all these organisations. Anyway, Australia was exporting about 80 million tonnes of LNG per year two years ago. According to the latest, it was 77.7 MT (in 20-21 financial year). The article said it has ‘retained its crown’ as the world’s largest exporter. Shouldn’t that be a dunce’s cap?

Canto: So many people are late in getting with the program. By the way, China has taken over from Japan as our number one LNG buyer – adding to our problems with that fascist government. In any case the argument would be – and I’ve heard it stated in a public forum – that we owe our wealth as a nation to these exports, and by extension, to our trading relation with China. .

Jacinta: Well, it’s interesting that the price of gas is rising domestically. Presumably this has something to do with so much of our gas going offshore? And renewables, though growing, are hardly ready to fill the domestic energy gap, right?

Canto: So this is all new stuff to get my head around, but a ‘Bloomberg Green’ video linked below has it that the Australian Competition and Consumer Commission (ACCC) has produced an interim gas report, a forecast for 2023. It predicts that the supply of gas for next year will fall short of demand by about 56 petajoules – 3% of total demand. This doesn’t sound like much, but with rising gas prices… Anyway the ACCC is recommending that the federal government bring into force the ‘Australian Domestic Gas Security Mechanism’, pressuring LNG exporters to reserve some of those earmarked exports (70 to 75 percent of production) for the domestic market. Now, some 11% of those exports aren’t covered by long-term contracts – they’re available for those as bids for them, and there might be a few countries bidding, considering the global situation.

Jacinta: Hmmm, sounds like a seller’s market, with impoverished buyers, including domestic ones. So the idea is that the government can intervene to force gas exporters to sell some of their stuff here, with reduced profits?

Canto: Yes, but whether they do is a question. The video goes on to talk about Australia’s new emissions reduction target of 43% on 2005 levels by 2030, with the aim of net zero emissions by 2050. Interestingly, the Bloomberg economist says that while it’s good news to get clear targets after years of nothing much, the targets are still a bit weak. Most notably, only 3% of passenger vehicles sold last year were EVs, and with no manufacturing here in the foreseeable future, the chances of EVs reaching 89% of sales by 2030 – Labor’s target – are surely minuscule.

Jacinta: Yes, but all the other cars purchases would be overseas-made vehicles, wouldn’t they?

Canto: Hmmm, so there might have to be legislation to favour EV imports, as well as plenty of infrastructure… And a turnaround in public attitudes, which I don’t presently see.

Jacinta: Returning to gas, the Australia Institute, which appears to be a left-leaning public policy think tank, has a critique of our gas exporters in another, very brief, video. It just advises turning our backs on gas tout de suite. Forget reserving gas for the domestic market – which might involve something more or less in the form of a bribe to the exporters. Instead, electrify everything, of course. More pronto than pronto, to make up for a lost decade of relative inaction. They describe it as a gas export crisis, in which domestic prices are soaring because so much of our gas is going offshore. A win-win for the gas companies.

Canto: So, is this the situation? Gas companies are in the business of profit. They sell gas overseas, even at the expense of the domestic market, because they can, because they’re owned by private individuals, they can sell to the highest bidder. And If this means gas is scarce domestically, and in high demand, because we’ve become dependent on gas, we haven’t been weaned off it, the gas companies can make another killing on the domestic market? They’re holding us to ransom, so to speak?

Jacinta: Oil and gas companies in the US as well as in Australia are making huge profits currently, due to scarcities caused by war, embargoes and such…

Canto: The Australian Domestic Gas Security Mechanism was designed to ensure sufficient domestic supply, but it’s not very efficient, and the domestic supply target is too low. Some state governments, notably Western Australia, have a higher domestic reserve, but of course what we need is to switch to renewable-based electric as quickly as possible, to get out from under the control of the fossil fuel barons.

Jacinta: Are gas companies subsidised here?

Canto: Do koalas shit in the trees? Renew Economy has a scathing article about this, posted today. It describes companies like Santos recording super-massive-record profits this year, and the term ‘war profiteering’ is mentioned. This has also been at the expense of the domestic market. Here’s a quote:

Santos categorically stated its project would not affect the domestic market because it would not buy gas out of the domestic market. But that is exactly what it has done. Santos bought large volumes of gas out of the domestic market in the first half of 2022, forcing domestic prices above export prices in the last six months. These actions have generated super profits, gouged from domestic gas consumer and forcing up domestic electricity prices to unaffordable levels. Santos has broken its approval conditions and IEEFA calls on the government to cancel their export licence.

The IEEFA, for our info, is the Institute for Energy Economics and Financial Analysis. Bruce Robertson, who wrote the Renew Economy article, has a similar piece on the IEEFA website. The thing is, the domestic reserve could be raised, and made non-negotiable (it isn’t at present) without having much of an effect on these windfall profits. As it is, gas companies are largely ignoring existing reserve requirements. The ACCC has the capacity to prosecute but apparently has no intention of doing so. They’re also doing nothing to tackle these companies’ collusion re price-fixing and tax avoidance. There’s something rotten about all this. Clearly we’re not going to wean ourselves from gas as quickly as we should, but we certainly shouldn’t be pumping up and sending off ever more of the stuff.

Jacinta: Well, yes, considering that the aim is to electrify everything, and people are starting to get on board with this, that means no new gas fields, so what are these companies going to do with these massive extra profits, other than line the pockets of CEOs and their immediate underlings?

Canto: Well, there will still be offshore markets for the foreseeable, so keep on despairing. Two months ago, the Sydney Morning Herald ran an opinion piece by Tony Wood of the Grattan Institute, arguing for a ‘windfall profit tax’ considering that some importers are paying ‘more than four and up to 10 times the contract prices’. The Federal Treasurer, Jim Chalmers, isn’t interested. And so the rich get richer, for the time being….

References

https://www.cleanenergyregulator.gov.au/RET/About-the-Renewable-Energy-Target

Marian Wilkinson, The Carbon Club, 2020

RET reached ahead of 2020 target

https://www.afr.com/policy/energy-and-climate/mike-cannon-brookes-on-esg-agl-and-why-australia-needs-no-more-gas-20220616-p5au3b

What the frack? Australia overtakes Qatar as world’s largest gas exporter

https://www.upstreamonline.com/lng/australia-remains-worlds-top-lng-exporter-but-it-could-lose-its-crown-this-year/2-1-1147625

Santos windfall: Australia is swimming in subsidised gas and we’re giving it away

https://ieefa.org/resources/why-government-must-break-eastern-australias-gas-cartel

https://www.smh.com.au/national/all-australians-should-share-in-record-profits-from-overseas-gas-sales-20220608-p5aryk.html

 

 

Written by stewart henderson

August 17, 2022 at 11:16 pm

some more on hydrogen and fuel cells

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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

Written by stewart henderson

April 25, 2022 at 5:37 pm

green hydrogen? it has its place, apparently

with one comment

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

a hydrogen energy industry in South Australia?

https://www.abc.net.au/news/2022-02-28/andrew-forrest-begins-work-on-green-hydrogen-hub-in-gladstone/100865988

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://www.statedevelopment.qld.gov.au/news/people-projects-places/breaking-ground-how-aldoga-is-leading-queenslands-renewable-energy-charge

https://skepticalscience.com/hydrogen-fuel.html

Hydrogen and Helium in Rigid Airship Operations

 

Written by stewart henderson

April 18, 2022 at 5:57 pm

some stuff on super-grids and smart grids

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In a recent New Scientist article, ‘The rise of supergrids’, I learned that Australia is among 80 countries backing a project, or perhaps an idea for a project, launched at COP26 in Glasgow, called One Sun One World One Grid, ‘a plan to massively expand the reach of solar power by joining up the electricity grids of countries and even entire continents’. My first reaction was cynicism – Australia’s successive governments have never managed to come up with a credible policy to combat global warming or to develop renewable energy, but they love to save face by cheering on other countries’ initiatives, at no cost to themselves.

Our state government (South Australia) did invest in the construction of a giant lithium ion battery, the biggest of its kind at the time (2017), built by Tesla to firm up our sometimes dodgy electricity supply, and, to be fair, there’s been a lot of state investment here in wind and solar, but there’s been very little at the national level. 

At the global level, the Chinese thugocracy has been talking up the idea of a ‘global energy internet’ for some years – but let’s face it, the WEIRD world has good reason not to trust the CCP. Apparently China is a world leader in the manufacture and development of UHVDC (ultra-high voltage direct current) transmission lines, and is no doubt hoping to spread the algorithms of Chinese technological and political superiority through a globe-wrapped electrical belt-and-road. 

But back in the WEIRD world, it’s the EU that’s looking to spearhead the supergrid system. It already has the most developed international system for trading electricity, according to the Financial Review. And of course, we’re talking about renewable energy here, though an important ancillary effect would be trade connections within an increasingly global energy system. There’s also an interest, at least among some, in creating a transcontinental supergrid in the US. 

Renewable sources such as solar and wind tend to be generated in isolated, low-demand locations, so long-distance transmission is a major problem, especially when carried out across national boundaries. Currently the growth has been in local microgrids and battery storage, but there are arguments about meshing the small-scale with the large scale. One positive feature of a global energy network is that it might just have a uniting effect, regardless of economic considerations. 

But of course economics will be a major factor in enticing investment. Economists use an acronym, LCOE, the levelized cost of electricity, when analysing costs and benefits of an electrical grid system. This is a measure of the lifetime cost of a system divided by the energy it produces. The Lappeenranta University of Technology in Finland used this and other measures to analyse the ‘techno-economic benefits of a globally interconnected world’, and found that they would be fewer than those of a national and subnational grid system, which seems counter-intuitive to me. However the analysts did admit that a more holistic approach to the supergrid concept might be in order. In short, more research is needed. 

Another concept to consider is the smart grid, which generally starts small and local but can be built up over time and space. These grids are largely computerised, of course, which raises security concerns, but it would be hard to over-estimate the transformative nature of such energy systems.

Our current grid system was pretty well finalised in the mid-twentieth century. It was of course based on fossil fuels – coal, gas and oil – with some hydro. The first nuclear power plant – small in scale – commenced operations in the Soviet Union in 1954. With massive population growth and massive increases in energy demand (as well as a demand for reliability of services) more and more power plants were built, mostly based on fossil fuels. Over time, it was realised that there were particular periods of high and low demand, which led to using ‘peaking power generators’ that were often switched off. The cost of maintaining these generators was passed on to consumers in the form of increased tariffs. The use of ‘smart technology’ by individuals and companies to control usage was a more or less inevitable response. 

Moving into the 21st century, smart technology has led to something of a battle and an accommodation with energy providers. Moreover, combined with a growing concern about the fossil fuel industry and its contribution to global warming, and the rapid development of variable solar and wind power generation, some consumers have become increasingly interested in alternatives to ‘traditional’ grid systems, and large power stations, which can, in some regions, be rendered unnecessary for those with photovoltaics and battery storage. The potential for a more decentralised system of mini-grids for individual homes and neighbourhoods has become increasingly clear.   

Wikipedia’s article on smart grids, which I’m relying on, is impressively fulsome. It provides, inter alia, this definition of a smart grid from the European Union:

“A Smart Grid is an electricity network that can cost efficiently integrate the behaviour and actions of all users connected to it – generators, consumers and those that do both – in order to ensure economically efficient, sustainable power system with low losses and high levels of quality and security of supply and safety. A smart grid employs innovative products and services together with intelligent monitoring, control, communication, and self-healing technologies in order to:

  1. Better facilitate the connection and operation of generators of all sizes and technologies.
  2. Allow consumers to play a part in optimising the operation of the system.
  3. Provide consumers with greater information and options for how they use their supply.
  4. Significantly reduce the environmental impact of the whole electricity supply system.
  5. Maintain or even improve the existing high levels of system reliability, quality and security of supply.
  6. Maintain and improve the existing services efficiently.”

So, with the continued growth of innovative renewable energy technologies, for domestic and industrial use, and in particular with respect to transport (the development of vehicle-to-grid [V2G] systems), we’re going to have, I suspect, something of a technocratic divide between early adopters and those who are not so much traditionalists as confused about or overwhelmed by the pace of developments – remembering that most WEIRD countries have an increasingly ageing population. 

I’m speaking for myself here. Being not only somewhat long in the tooth but also dirt poor, I’m simply a bystander with respect to this stuff, but I hope to to get more integrated, smart and energetic about it over time. 

References

https://www.afr.com/companies/energy/the-future-of-power-is-transcontinental-submarine-supergrids-20210622-p5837a

Global supergrid vs. regional supergrids

https://en.wikipedia.org/wiki/Smart_grid

https://en.wikipedia.org/wiki/Vehicle-to-grid

Written by stewart henderson

March 15, 2022 at 7:33 pm

resetting the electrical agenda

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the all-electric la jamais contente, first car to break the 100 kph barrier, in 1899

In his book Clearing the air, Tim Smedley reminds us of the terrible errors we made in abandoning electric vehicles in the early 20th century. Smedley’s focus was on air pollution, and how the problem was exacerbated, and in fact largely caused, by emissions from car exhausts in increasingly car-dependent cities like Beijing, Delhi, Los Angeles and London. In the process he briefly mentioned the electric tram systems that were scrapped in so many cities worldwide in favour of the infernal combustion engine. It’s a story I’ve heard before of course, but it really is worth taking a deeper dive into the mess of mistakes we made back then, and the lessons we need to learn. 

A major lesson, unsurprisingly, is to be suspicious of vested interests. Today, the fossil fuel industry is still active in denying the facts about global warming and minimising the impact of air pollution on our health. Solar and wind power, and the rise of the EV industry – which, unfortunately, doesn’t exist in Australia – are still subject to ridiculous attacks by the heavily subsidised fossil fuel giants, though at least their employees don’t go around smashing wind turbines and solar panels. The website Car and Driver tells a ‘funny story’ about the very earliest days of EVs: 

… Robert Davidson of Aberdeen, built a prototype electric locomotive in 1837. A bigger, better version, demonstrated in 1841, could go 1.5 miles at 4 mph towing six tons. Then it needed new batteries. This impressive performance so alarmed railway workers (who saw it as a threat to their jobs tending steam engines) that they destroyed Davidson’s devil machine, which he’d named Galvani.

If only this achievement by Davidson, before the days of rechargeable batteries, had been greeted with more excitement and wonder. But by the time rechargeable batteries were introduced in the 1860s, steam locomotives were an established and indeed revolutionary form of transport. They began to be challenged, though, in the 1880s and 90s as battery technology, and other features such as lightweight construction materials and pneumatic tyres, started to make electric transport a more promising investment. What followed, of course, with the development of and continual improvements to the internal combustion engine in the 1870s and 80s, first using gas and then petrol – the 1870s into the 90s and beyond was a period of intense innovation for vehicular transport – was a serious and nasty battle for control of the future of private road transport. Electricity wasn’t widely available in the early twentieth century, but rich industrialists were able to create a network of filling stations, which, combined with the wider availability of cheap oil, and the mass production and marketing capabilities of industrialists like Henry Ford – who had earlier considered electric vehicles the best future option – made petrol-driven vehicles the eventual winner, in the short term. Of course, little thought was given in those days to fuel emissions. A US website describes a likely turning point: 

… it was Henry Ford’s mass-produced Model T that dealt a blow to the electric car. Introduced in 1908, the Model T made gasoline [petrol]-powered cars widely available and affordable. By 1912, the gasoline car cost only $650, while an electric roadster sold for $1,750. That same year, Charles Kettering introduced the electric starter, eliminating the need for the hand crank and giving rise to more gasoline-powered vehicle sales.

Electrically-powered vehicles quickly became ‘quaint’ and unfashionable, leading to to the trashing of electric trams worldwide. 

The high point of the internal combustion engine may not have arrived yet, as numbers continue to climb. Some appear to be addicted to the noise they make (I hear them roaring by nearly every night!). But surely their days are numbered. What shocks me, frankly, is how slow the public is to abandon them, when the fossil fuel industry is so clearly in retreat, and when EVs are becoming so ‘cool’. Of course conservative governments spend a fortune in subsidies to the fossil fuel industry –  Australia’s government  provided over $10 billion in the 2020-21 financial year, and the industry in its turn has given very generously to the government (over $1.5 million in FY2020, according to the Market Forces website).

But Australia is an outlier, with one of the worst climate policies in the WEIRD world. There will be a federal election here soon, and a change of government is very much on the cards, but the current labor opposition appears afraid to unveil a climate policy before the election. The move towards electrification of vehicles in many European countries, in China and elsewhere, will eventually have a knock-on effect here, but the immediate future doesn’t look promising. EV sales have risen markedly in the past twelve months, but from a very low base, with battery and hybrids rising to 1.95% of market share – still a paltry amount (compare Norway with 54% EVs in 2020). Interestingly, Japan is another WEIRD country that is lagging behind. China continues to be the world leader in terms of sheer numbers. 

The countries that will lead the field of course, will be those that invest in infrastructure for the transition. Our current government announced an infrastructure plan at the beginning of the year, but with little detail. There are issues, for example, about the type of charging infrastructure to fund, though fast-charging DC seems most likely.

In general, I’ve become pessimistic about Australians switching en masse to EVs over the next ten years or so – I’ve read too many ‘just around the corner’ articles with too little actual change in the past five years. But perhaps a new government with a solid, detailed plan will emerge in the near future, leading to a burst of new investment…. 

References

Tim Smedley, Clearing the air, 2019

https://www.caranddriver.com/features/g15378765/worth-the-watt-a-brief-history-of-the-electric-car-1830-to-present/

https://www.energy.gov/articles/history-electric-car

https://www.marketforces.org.au/politicaldonations2021/

 

Written by stewart henderson

February 27, 2022 at 1:07 pm

what is electricity? part 10 – it’s some kind of energy

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je ne sais pas

Canto: We’ve done nine posts on electricity and it still seems to me like magic. I mean it’s some kind of energy produced by ionisation, which we’ve been able to harness into a continuous flow, which we call current. And the flow can alternate directionally or not, and there are advantages to each, apparently.

Jacinta: And energy is heat, or heat is energy, and can be used to do work, and a lot of work has been done on energy, and how it works – for example there’s a law of conservation of energy, though I’m not sure how that works.

Canto: Yes maybe if we dwell on that concept, something or other will become clearer. Apparently energy can’t be created or destroyed, only converted from one form to another. And there are many forms of energy – electrical, gravitational, mechanical, chemical, thermal, whatever.

Jacinta: Muscular, intellectual, sexual?

Canto: Nuclear energy, mass energy, kinetic energy, potential energy, dark energy, light energy…

Jacinta: Psychic energy… Anyway, it’s stuff that we use to do work, like proteinaceous foodstuff to provide us with the energy to get ourselves more proteinaceous foodstuff. But let’s not stray too far from electricity. Electricity from the get-go was seen as a force, as was gravity, which Newton famously explained mathematically with his inverse square law.

Canto: ‘Every object or entity attracts every other object or entity with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres’, but he of course didn’t know how much those objects, like ourselves, were made up of a ginormous number of particles or molecules, of all shapes and sizes and centres of mass.

Jacinta: But the inverse square law, in which a force dissipates with distance, captured the mathematical imagination of many scientists and explorers of the world’s forces over the following generations. Take, for example, magnetism. It seemed to reduce with distance. Could that reduction be expressed in an inverse square law? And what about heat? And of course electrical energy, our supposed topic?

Canto: Well, some quick net-research tells me that magnetism does indeed reduce with the square of distance, as does heat, all under the umbrella term that ‘intensity’ of any force, if you can call thermal energy a force, reduces in an inverse square ratio from the point source in any direction. As to why, I’m not sure if that’s a scientific question.

Jacinta: A Khan Academy essay tackles the question scientifically, pointing out that intuition sort of tells us that a force like, say magnetism, reduces with distance, as does the ‘force’ of a bonfire, and that these reductions with distance might all be connected, and therefore quantified in the same way. The key is in the way the force spreads out in straight lines in every direction from the source. That’s how it dissipates. When you’re close to the source it hasn’t had a chance to spread out.

Canto: So when you’re measuring the gravitational force upon you of the earth, you have to remember that attractive force is pulling you to the earth’s centre of mass. That attractive force is radiating out in all directions. So if you’re at a height that’s twice the distance between the earth’s surface and its centre of mass, the force is reduced by a particular mathematical formula which has to do with the surface of a sphere which is much larger than the earth’s sphere (though the earth isn’t quite a sphere), but can be mathematically related to that sphere quite precisely, or to a smaller or larger sphere. The surface of a sphere increases with the square of the radius.

Jacinta: Yes, and this inverse square law works for light intensity too, though it’s not intuitively obvious, perhaps. Or electromagnetic radiation, which I think is the technical term. And the keyword is radiation – it radiates out in every direction. Think of spheres again. But we need to focus on electricity. The question here is – how does the distance between two electrically charged objects affect the force of attraction or repulsion between them?

Canto: Well, we know that increasing the distance doesn’t increase the force. In fact we know – we observe – that increasing the distance decreases the force. And likely in a precise mathematical way.

Jacinta: Well thought. And here we’re talking about electrostatic forces. And evidence has shown, unsurprisingly, that the decreased or increased force is an inverse square relationship. To spell it out, double the distance between two electrostatically charged ‘points’ decreases the  force (of attraction or repulsion) by two squared, or four. And so on. So distance really matters.

Canto: Double the distance and you reduce the force to a quarter of what it was. Triple the distance and you reduce it to a ninth.

Jacinta: This is Coulomb’s law for electrostatic force. Force is inversely proportional to the square of the distance –     F = k \frac{q_1q_2}{r^2}. Where F is the electric force, q are the two charges and r is the distance of separation. K is Coulomb’s constant.

Canto: Which needs explaining.

Jacinta: It’s a proportionality constant. This is where we have to understand something of the mathematics of variables and constants. So, Coulomb’s law was published by the brilliant Charles Augustin de Coulomb, who despite what you might think from his name, was no aristocrat and had to battle to get a decent education, in 1785. And as can be seen in his law, it features a constant similar to Newton’s gravitational constant.

Canto: So how is this constant worked out?

Jacinta: Well, think of the most famous equation in physics, E=mc2, which involves a constant, c, the speed of light in a vacuum. This speed can be measured in various ways. At first it was thought to be infinite, which is crazy but understandable. It would mean that that we were seeing the sun and stars as they actually are right now, which I’m sure is what every kid thinks. Descartes was one intellectual who favoured this view. It was ‘common sense’ after all. But a Danish astronomer, Ole Roemer, became the first person to calculate an actual value, when he recognised that there was a discrepancy between his calculation of the eclipse of Io, Jupiter’s innermost moon, and the actual eclipse as seen from earth. He theorised correctly that the discrepancy was due to the speed of light. Later the figure he arrived at was successively revised, by Christiaan Huygens among others, but Roemer was definitely on the right track…

Canto: Okay, I understand – and I understand that the calculation of the gravitational force exerted at the earth’s surface, about 9.8 metres per sec per sec, helps us to calculate the gravitational constant, I think. Anyway, Henry Cavendish was the first to come up with a pretty good approximation in 1798. But what about Coulomb’s constant?

Jacinta: Well I could state it – that’s to say, quote it from a science website – in SI units (the International System of units), but how that was arrived at precisely, I don’t know. It wasn’t worked out mathematically by Coulomb, I don’t think, but he worked out the inverse proportionality. There are explanations online, which invoke Gauss, Faraday, Lagrange and Maxwell, but the maths is way beyond me. Constants are tricky to state clearly because they invoke methods of measurements, and those measures are only human. For example the speed of light is measured in metres per second, but metres and seconds are actually human constructions for measuring stuff. What’s the measure of those measures? We have to use conventions.

Canto: Yes, this has gone on too long, and I feel my electric light is fading. I think we both need to do some mathematical training, or is it too late for us?

Jacinta: Well, I’m sure it’s all available online – the training. Brilliant.org might be a good start, or you could spend the rest of your life playing canasta – chess has been ruined by AI.

Canto: So many choices…

 

Written by stewart henderson

February 20, 2022 at 2:34 pm

what is electricity? part 8: turning DC current into AC, mostly

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Canto: So before we go into detail about turning direct current into alternating current, I want to know, in detail, why AC is better for our grid system. I’m still not clear about that.

Jacinta: It’s cheaper to generate and involves less energy loss over medium-long distances, apparently. This is because the voltage can be varied by means of transformers, which we’ll get to at some stage. Varying the voltage means, I think, that you can transmit the energy at high voltages via power lines, and then bring the voltage down via transformers for household use. This results in lower energy loss, but to understand this requires some mathematics.

Canto: Oh dear. And I’ve just been reading that AC is, strictly speaking, not more efficient than DC, but of course the argument and the technical detail is way beyond me.

Jacinta: Well let’s avoid that one. Or…maybe not. AC isn’t in any way intrinsically superior to DC, it depends on circs – and that stands for circuits as well as circumstances haha. But to explain this requires going into root mean square (RMS) values, which we will get to, but for now let’s focus on converting DC into AC. Here’s a quote from ‘all about circuits’:

If a machine is constructed to rotate a magnetic field around a set of stationary wire coils with the turning of a shaft, AC voltage will be produced across the wire coils as that shaft is rotated, in accordance with Faraday’s Law of electromagnetic induction. This is the basic operating principle of an AC generator, also known as an alternator

The links explain more about magnetic fields and electromagnetic induction, which we’ll eventually get to. Now we’ve already talked about rotating magnets to create a polarised field…

Canto: And when the magnet is at a particular angle in its rotation, no current flows – if ‘flow’ is the right word?

Jacinta: Yes. This same website has a neat illustration, and think of the sine curves.

Canto: Can you explain the wire coils? They’re what’s shown in the illustration, right, with the magnet somehow connected to them? And the load is anything that resists the current, creating energy to power a device?

Jacinta: Yes, electric coils, or electromagnetic coils, as I understand them, are integral to most electronic devices, and according to the ‘industrial quick search’ website, they ‘provide inductance in an electrical circuit, an electrical characteristic that opposes the flow of current’.

Canto: OMG, can you explain that explanation?

Jacinta: I can but try. You would think that resistance opposes the flow of current – like, to resist is to oppose, right? Well, it gets complicated, because magnetism is involved. We quoted earlier something about Faraday’s Law of electromagnetic induction, which will require much analysis to understand. The Oxford definition of inductance is ‘the property of an electric conductor or circuit that causes an electromotive force to be generated by a change in the current flowing’, if that helps.

Canto: Not really.

Jacinta: So… I believe… I mean I’ve read, that any flow of electric current creates a magnetic field…

Canto: How so? And what exactly is a magnetic field?

Jacinta: Well, it’s like a field of values, and it gets very mathematical, but the shape of the field is circular around the wire. There’s a rule of thumb about this, quite literally. It’s a right-hand rule…

Canto: I’m left-handed.

Jacinta: It shouldn’t be difficult to remember this. You set your right thumb in the direction of the current, and that means your fingers will curl in the direction of the magnetic field. So that’s direction. Strength, or magnitude, reduces as you move out from the wire, according to a precisely defined formula, B (the magnetic field) = μI/2πr. You’ll notice that the denominator here defines the circumference of a circle.

Canto: Yes, I think I get that – because it’s a circular field.

Jacinta: I got this from Khan Academy. I is the current, and μ, or mu (a Greek letter) stands for the permeability of the material, or substance, or medium, the wire is passing through (like air, for example). It all has something to do with Ampere’s Law. When the wire is passing through air, or a vacuum, mu becomes, or is treated as, the permeability of free space (μ.0), which is called a constant. So you can calculate, say, with a current of 3 amps, and a point 2 metres from the wire that the current is passing through, the magnitude and direction of the magnetic field. So you would have, in this wire passing through space, μ.0.3/2π.2, or μ.0.3/4π, which you can work out with a better calculator than we have, one that has all or many of the constants built in.

Canto: So easy. Wasn’t this supposed to be about alternating current?

Jacinta: Okay forget all that. Or don’t, but getting back to alternating current and how we create it, and how we switch from AC to DC or vice versa…

Canto: Let’s start, arbitrarily, with converting AC to DC.

Jacinta: Okay, so this involves the use of diodes. So, a diode conducts electricity in one direction only…. but, having had my head spun by the notion of diodes, and almost everything else electrical, I think we should start again, from the very beginning, and learn all about electrical circuits, in baby steps.

Canto: Maybe we should do it historically again, it’s more fun. People are generally more interesting than electrons.

Jacinta: Well, maybe we should do a bit of both. It’s true that we’re neither of us too good at the maths of all this but it’s pretty essential.

Canto: Okay, let’s return to the eighteenth century…

References

https://www.allaboutcircuits.com/textbook/direct-current/chpt-15/magnetic-fields-and-inductance/

Alternating Current vs Direct Current – Rms Voltage, Peak Current & Average Power of AC Circuits (video – the organic chemistry tutor)

 

Written by stewart henderson

January 16, 2022 at 6:19 pm

what is electricity? part 7 – alternating current explained, maybe

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Canto: So, alternating current is electrical current that alternates, or wobbles, or zig-zags, or cycles back and forth, at fifty or sixty cycles per second, aka hertz, but how and why?

Jacinta: Well, as Sabine would say, that’s what we’re going to talk about today. As always, when we look online for explanations, they tend to assume the reader or viewer has background knowledge by the bucketful. Here’s a typical example:

Many sources of electricity, most notably electromechanical generators, produce AC current with voltages that alternate in polarity, reversing between positive and negative over time. An alternator can also be used to purposely generate AC current.

It goes on to explain what an alternator is, but not very effectively for types like us.

Canto: We really need our own ‘For Dummies’ library.

Jacinta: The alternating current that’s used in our electrical grids has a neat sine wave form, undulating at precise intervals above and below a time line.

I’ll try to find out how we bring about alternating current, but first some points about its usefulness. As I think we mentioned before, AC is useful for transporting electrical energy, because it produces lower current at higher voltages (I DON’T REALLY UNDERSTAND THIS), so creating less resistance in the power lines, and so less energy lost as heat.

Canto: Some simple definitions, via Wikipedia et al, which we really need to keep reinforcing. Voltage is electric potential, or pressure, or tension. It’s usually analogised as water in a tank, or a boulder at the top of a mountain, ready to unleash its ‘tension’ by rolling downhill, and meeting resistance along the way, which makes things happen.

Jacinta: Did you know that there’s also three-phase AC power? OMG. But we talked in an earlier post about electrons only moving slightly, bumping the next electron along and so on. But, duh, I didn’t think that one through – that bumping action would be continuous, like people in a queue. You’d bump the person before and be bumped by the person behind, so the movement would be continuous, more or less, they’d all move from the positive to the negative. It’s what they call a chain reaction.

Canto: Interesting, but back to these analogies, I understood that a water tank has the potential to pour out water, and that a boulder has a potential to release kinetic energy down a mountain, but what is this potential energy that a battery has? It’s something called voltage, but that’s what I don’t understand. It’s the storage of a certain amount of electricity, like so much water. But I can visualise stored water. I can’t visualise stored electricity, or electric potential, or whatever.

Jacinta: Well, one day, understanding will dawn. Meanwhile, AC power, that’s when you get electrons to oscillate backwards and forwards, for example via a spinning magnet, which alternately repels and attracts electrons. It’s the movement of the electrons rather than their direction that creates the current.

Canto: Changing polarity. That’s what a spinning magnet will do (and maybe that’s what is meant by an alternator, or something like). And it will do it in an undulating rather than abrupt way. Very fast undulating – 50 cycles a second.

Jacinta: So I think we need to look at transformers, which are able to change the ac voltage, but not dc. Don’t ask why, at least not yet.

Canto: I’m looking at a vid which says that with AC the voltage varies, creating a sinusoidal function, as in the graphic above. But this explains nothing to me. Voltage is electric potential, but what really is that? I don’t want fucking analogies, I want the reality of it. How do you store this ‘electric potential’ in a battery, or whatever? And what really gets me about this and other videos are the comments – ‘great explanation’, ‘what a great teacher you are’, I’ve learned more from this than from months of study’ etc etc etc. And I’m thinking – am I a complete moron or what?

Jacinta: I feel your frustration, but we’ve promised to focus on AC, so just hold on to that question, which can be formulated as – How can a battery (or any other device) store electric potential for later use?

Canto: Which I suppose is something the same as – what is a battery (or an electric potential storage device)? How can you make one?

Jacinta: Anyway, a battery is used for DC energy, flowing from its positive to its negative terminal. That’s why, if you have batteries in series, like in the tube of my computer keyboard, they have to be in the right order, positive connected to negative terminals.

Canto: And if you have, say, three 1.5v batteries in series, that means you have 4.5v of ‘electric potential’?

Jacinta: Uhhh, let’s focus on AC. So, in Australia we typically have 230v household sources of AC electricity, oscillating, or changing polarity, at a frequency of 50 cycles/second, or 50 hertz. Imagine if you have a battery that’s spinning around so that the polarity is, well, spinning around too.

Canto: So if we have a 230v AC source in every home, is that like a gigantic spinning battery? I’d like to see that. Is that what an alternator is?

Jacinta: Well, if you look up ‘What’s an alternator’, you’ll generally find stuff about motor vehicles, but it’s definitely all about alternating current. And if you think polarity, you should think magnetism. So an alternator is essentially a magnet connected to an electric circuit, that changes polarity, usually by spinning, which creates a smooth alternation – back to the sine wave. We’re talking here about one-phase AC.

Canto: Yeah, we don’t presumably have alternators in our homes because it’s already AC in the wires, so it’s all AC?

Jacinta: Don’t confuse me. Running an electric current through a wire – usually copper – creates a magnetic field, and you can strengthen this magnetic field by coiling the wire. I’m not sure why, but this is essential electromagnetism, which we might understand one day. Anyway, this coil of wire is now an electromagnet, with its own polarity. Increasing the current induces a stronger magnetic field. If we run a magnet through the coil, we’ll create a stronger electric current, in DC form. Stop the magnet, and you stop that current. Reverse the magnet and you reverse the current. Push and pull the magnet in and out, and you create an AC current.

Canto: So that’s how sex can be electrifying – if it’s done fast enough?

Jacinta: Hmmm. The speed of the magnet’s movement does create a stronger current, as does the strength of the magnet.

Canto: Ahh, so it’s both the meat and the motion? Anyway, how to transform DC into AC – I’ve heard of a new device, or whatever – an inverter.

Jacinta: Ok, backing up, you’ve no doubt heard of the big battle between Edison and Tesla regarding AC and DC, back at the end of the 19th century. Well, Edison proved himself a bit of an arsehole during this battle, though the hero-worship of Tesla has since become a bit extreme. Since then, it’s been AC for big electrical networks worldwide, but DC is still used for car batteries and other smaller scale power. And, yes, an inverter is the device used to convert DC to AC.

Canto: Let me say that I do understand how AC works to create energy. It doesn’t matter if the movement is in one direction, or two, or a thousand. It’s the movement itself that creates the energy, which creates heat to boil your kettle or light your lamp.

Jacinta: Good, now there are rectifiers, which are a collection of diodes, which can convert AC to DC, but that’s for another post. An inverter comes in more than one type. Some use electromagnetic switches, reversing the flow abruptly, even brutally, with a pattern very different from our sine wave. More like castle crenellations. But electronic inverters use components such as capacitors and inductors – yes, they’ll be explained eventually – to smooth out the transitions. Transformers can also be used to change DC input voltage into a quite different AC voltage output, though of course, according to the law of conservation of energy, (first law of thermodynamics) you can’t get more power out of the system than you put in.

Canto: Changing the subject yet again, I was getting aerated about batteries, and I should’ve thought about them a bit more – I know that they get their electric potential from chemistry. I’ve been reading about Volta’s battery, made from zinc, silver and cloth or paper soaked in salty water. But that, and later improvements, and the mechanisms involved, are also for later posts.

Jacinta: Yes, a battery has an anode and a cathode and an electrolyte material separating them. A fun topic to explore more thoroughly. But we’re onto inverters. We need them to convert DC voltage providers, such as batteries and solar panels, into AC power for households. So batteries work to cause a current to flow, in say, a copper wire, and this creates a circuit between the cathode and the anode, heating up lamps and kettles along the way. But inverting the current, to create the sine wave pattern, or multiple such patterns, requires a magnet, coils and such. It’s complicated, so our next post will be horrible.

a pure sine wave inverter, apparently

References

What is Alternating Current (AC)? – Basic AC Theory – AC vs. DC (video)

Electric current (Khan Academy)

https://www.britannica.com/science/conservation-of-energy

https://www.explainthatstuff.com/how-inverters-work.html

 

Written by stewart henderson

January 11, 2022 at 5:35 pm