Posts Tagged ‘solar energy’
advancing solar, the photovoltaic effect, p-type semiconductors and the fiendishness of human manipulation
how to enslave electrons – human, all too human – stolen from E4U
Canto: Back to practical stuff for now (not that integral calculus isn’t practical), and the efficiencies in solar panels among other green technologies. Listening to podcasts such as those from SGU and New Scientist while walking the dog isn’t the best idea, what with doggy distractions and noise pollution from ICEs, so we’re going to take some of the following from another blog, Neurologica, which was also summarised on a recent SGU podcast.
Jacinta: Yes it’s all about improvements in solar panels, and the materials used in them, over the past couple of decades. We’re talking about improvements in lifespan and overall efficiency, not to mention cost to the consumer. Your standard silicon solar panels have improved efficiency since the mid 2000s from around 11% to around 28% – something like a 180% improvement. Is that good maths? Anyway, it’s the cheapest form of new energy and will become cheaper. And there’s also perovskite for different solar applications, and the possibility of quantum hi-tech approaches, using advanced AI technology to sort out the most promising. So the future is virtually impossible for we mere humans to predict.
Canto: Steven Novella, high priest of the SGU and author of the Neurologica post, suggests that with all the technological focus in this field today, who knows what may turn up – ‘researchers are doing amazing things with metamaterials’. He takes a close look at organic solar cells in particular, but these could possibly be combined with silicon and perovskite in the future. Organic solar cells are made from carbon-based polymers, essentially forms of plastic, which can be printed on various substrates. They’re potentially very cheap, though their life-span is not up to the silicon crystal level. However, their flexibility will suit applications other than rooftop solar – car roofs for example. They’re also more recyclable than silicon, which kind of solves the life-span problem. Their efficiency isn’t at the silicon level either, but that of course may change with further research. Scaling up production of these flexible organic solar materials has already begun.
Jacinta: So, I’ve mentioned perovskite, and I barely know what I’m talking about. So… some basic research tells me it’s a calcium titanium oxide mineral composed of calcium titanate (chemical formula CaTiO3), though any material with the ‘perovskite structure’ can be so called. It’s found in the earth’s mantle, in some chondritic meteorites, ejected limestone deposits and in various isolated locations such as the Urals, the Kola Peninsula in Russia, and such other far-flung places as Sweden and Arkansas. But I think the key is in the crystalline structure, which can be found in a variety of compounds.
Canto: Yes, worth watching perovskite developments in the future. I’m currently watching a video from Real Engineering called ‘the mystery flaw of solar panels’, which argues that this flaw has been analysed and solutions are being found. So, it starts with describing the problem – light-induced degradation, and explaining the photovoltaic effect:
The photovoltaic effect is the generation of voltage and electric current in a material upon exposure to light. It is a physical and chemical phenomenon.
Jacinta: Okay can we get clear again about the difference between voltage and current? I know that one is measured in volts and the other in amps but that explains nout.
Canto: Well, here’s one explanation – voltage, or emf, is the difference in electric potential between one point and another. Current is the rate of flow of an electric charge at any particular point. Check the references for more detail on that. Anyway we really are in the middle of a solar revolution, but the flaw in current solar panels is that newly manufactured solar cells are being tested at a little over 20% efficiency, that’s to say, 20% of the energy input from the sun is being converted into electric current. But within hours of operation the efficiency drops to 18% or so. That’s a 10% drop in generation, which becomes quite substantial on a large scale, with solar farms and such. So this is the problem of light-induced degradation, as mentioned. So, to quote the engineering video, ‘[the photovoltaic effect] is where photons of a particular threshold frequency, striking a material, can cause electrons to gain enough energy to free them from their atomic orbits and move freely in the material’. Semiconductors, which are sort of halfway between conductors and insulators, are the best materials for making this happen.
Jacinta: That’s strange, or counter-intuitive. Wouldn’t conductors be the best for getting electrons moving? Isn’t that why we use copper in electric wiring?
Canto: That’s a good question, which we might come back to. The first semiconducting material used, back in the 1880s, was (very expensive) selenium, which managed to create a continuous current with up to 1% efficiency. And so, silicon.
Jacinta: Which is essentially what we use, in inedible chip form, in all our electronic devices. Pretty versatile stuff. Will we always have enough of it?
Canto: Later. So when light hits this silicon crystal material, it can either be reflected, absorbed or neither – it may pass through without effect. Only absorption creates the photovoltaic effect. So, to improve efficiency we need to enhance absorption. Currently 30% of light is reflected from untreated silicon panels. If this wasn’t improved, maximum efficiency could only reach 70%. So we treat the panels with a layer of silicon monoxide reducing reflection to 10%. Add to that a layer of titanium dioxide, taking reflection to as low as 3%. A textured surface further enhances light absorption – for example light might be reflected sideways and hit another bump, where it’s absorbed. Very clever. But even absorbed light only has the potential to bring about the photovoltaic effect.
Jacinta: Yes, in order to create the effect, that is, to get electrons shifted, the photon has to be above a certain energy level, which is interesting, as photons aren’t considered to have mass, at least not when they’re at rest, but I’m not sure if photons ever rest… As the video says, ‘a photon’s energy is defined by multiplying Planck’s constant by its frequency’. That’s E = h.f, where h is Planck’s constant, which has been worked out by illustrious predecessors as 6.62607015 × 10−34 joule-seconds, according to the International System of Units (SI). And with silicon, the photons need an electromotive force of 1.1 electron volts to produce the photovoltaic effect, which can be converted, apparently, to a wavelength of 1,110 nanometres. That’s in the infrared, on the electromagnetic spectrum, near visible light. Any lower, in terms of energy (the lower the energy, the lower the frequency, the longer the wavelength, I believe), will just create heat and little light, a bit like my brain.
Canto: I couldn’t possibly comment on that, but the video goes on to explain that the solar energy we get from the sun, shown on a graph, is partially absorbed by our atmosphere before it reaches our panels. About 4% of the energy reaching us is in the ultraviolet, 44% is in the visible spectrum and 52% is in the infrared, surprisingly enough. Infrared red light has lower energy than visible light but it has a wider spectrum so the total energy emitted is greater. Now, silicon cannot use light above 1,110 nms in wavelength, meaning that some 19% of the sun’s energy can’t be used by our panels.
Jacinta: Yes, and another thing we’re supposed to note is that higher energy light doesn’t release more electrons, just higher energy electrons…
Canto: And presumably they’re talking about the electrons in the silicon structure?
Jacinta: Uhh, must be? So blue light – that’s at the short-wavelength end of the visible spectrum – blue light has about twice the energy of red light, ‘but the electrons that blue light releases simply lose their extra energy in the form of heat, producing no extra electricity. This energy loss results in about 33% of sunlight’s energy being lost.’ So add that 33% to the 19% lost at the long-wavelength end, that’s 52% of potential energy being lost. These are described as ‘spectrum losses’.
Canto: Which all sounds bad, but silicon, or its reaction with photons, has a threshold frequency that ‘balances these two frequency losses’. So, it captures enough of the low-energy wavelengths (the long wavelengths beyond the infra-red), while not losing too much efficiency due to heat. The heat problem can be serious, though, requiring active cooling in some climates, thus reducing efficiency in a vicious circle of sorts. Still, silicon is the best of threshold materials we have, presumably.
Jacinta: So, onto the next piece of physics, which is that there’s more to creating an electric current than knocking an electron free from its place in ye olde lattice, or whatever. For starters, ye olde electron just floats about like a lost lamb.
Canto: No use to anyone.
Jacinta: Yeah, it needs to be forced into doing work for us.
Canto: Because humans are arseholes who make slaves of everything that moves. Free the electrons!
Jacinta: You’ve got it. They need to be forced to work an electric circuit. And interestingly, the hole left when we’ve knocked an electron out of its happy home, that hole is also let loose to roam about like a lost thing. Free electrons, free holes, when they meet, they’re happy but the circuit is dead before it starts.
Canto: This sounds like a tragicomedy.
Jacinta: So we have to reduce the opportunities for electrons and holes to meet. Such is the cruelty of progress. For of course, we must needs use force, taking advantage of silicon’s unique properties. The most excellent crystal structure of the element is due to its having 4 electrons in its outer shell. So it bonds covalently with 4 other silicon atoms. And each of those bonds with 3 others and so on. A very stable balance. So the trick that we manipulative humans use to mess up this divine balance is to introduce impurities called dopants into the mix. If we add boron, which has 3 outer electrons, into the crystal lattice, this creates 3 covalent bonds with silicon, leaving – a hole!
Canto: How fiendishly clever!
Jacinta: It’s called a p-type trick, as it has this ‘positive’ hole just waiting for an electron to fill it. Sounds kind of sexy really.
Canto: Manipulation can be sexy in a perverse way. Stockholm syndrome for electrons?
Jacinta: Okay, there’s a lot more to this, but we’ve gone on long enough. I’ve had complaints that our blog posts are too long. Well, one complaint, because only one or two people read our stuff…
Canto: No matter – at least we’ve learned something. Let’s continue to rise above ourselves and grasp the world!
Jacinta: Okay, to be continued….
References
https://www.theskepticsguide.org/podcasts
https://news.mit.edu/2022/perovskites-solar-cells-explained-0715
The Mystery Flaw of Solar Panels (Real Engineering video)
https://byjus.com/physics/difference-between-voltage-and-current/
Amazing internet, female science communicators and fighting global warming: an interminable conversation 4
from Renew Economy – SA doing quite well
Jacinta: As I’ve said many times – or at least I’ve thought many times – the internet is surely the greatest development in human history for those interested in self-education. Can you think of anything to compare?
Canto: Not really. The printing press was important, but literacy rates were much lower when that came out – which makes me think that universal education, which includes literacy of course, must be up there. But of course it was never really universal, and I suppose neither is the internet, but it appears to have penetrated further and wider, and much faster than any previous technology…
Jacinta: Universal education was more or less compulsory, and so very top-down. Not self-education at all. The internet gives every individual more control…
Canto: And most choose to stay within their own social media bubble. But for those keen to learn, yes the internet just gets more and more fantastic.
Jacinta: And the trend now is for spoken presentations, with bells and whistles, rather than reams of writing, which can be off-putting…
Canto: Well, our stuff is pretend-speak. We don’t do videos because we’re both extremely ugly, and even our voices are hideous, and we haven’t a clue about bells and whistles.
Jacinta: Sigh. Consigned to obscurity, but we must perforce mumble on into the vacuum of our little internet space. Even so, I’d like to enthuse, however impotently, about the many excellent female science presenters out there, with their vodcasts or vlogs or whatever, such as Australia’s Engineering with Rosie, as well as Kathy loves physics and history, Sabine Hossenfelder and Dr Becky. And I’ll keep an eye out for more.
Canto: But of course we still love books. The most recent read has been Saul Griffith’s The Big Switch, a call to action on renewables, particularly here in Australia.
Jacinta: So with a change of government, Australia is now going to try and catch up with the leading nations re renewable energy and generally changing the energy landscape. So it’s time to turn to the Renew Economy website, the best Australian site for what’s happening with renewables. First stop is the bar graph that’s long featured on the site. It shows that the eastern states, Queensland, NSW and Victoria, are the problem states, still heavily reliant on coal. Victoria is arguably worst as it relies on brown coal for about two thirds of its supply.
Canto: And the other two states use black coal, but they’ve developed a lot more solar than Victoria. They are, of course, a lot sunnier than Victoria. What’s the difference between the two coals, in environmental terms?
Jacinta: Black coal, aka anthracite, is generally regarded as a superior fuel. It contains less water than brown coal, aka lignite, and more carbon. You have to use quite a lot more brown coal – maybe 3 times as much – to extract the same amount of energy as anthracite. According to Environment Victoria,
Brown coal is pulverised and then burned in large-scale boilers. The heat is used to boil water and the steam is used to drive turbines that generate electricity. When brown coal is burnt it releases a long list of poisonous heavy metals and toxic chemicals like sulphur dioxide, mercury, particulate matter and nitrogen oxides. By world standards these pollutants are poorly monitored & controlled, and they impose a staggering health cost of up to $800 million every year.
I’ve left in the links, which are to other Environment Victoria articles. Clearly this website isn’t government controlled, as it castigates heavily subsidised ‘boondoggle’ projects intended to keep the brown coal afloat (very problematic for mining). These projects have apparently gone nowhere. However the site does mention the ‘recent’ announcement of an electric vehicle manufacturing plant in the Latrobe Valley, providing at least 500 jobs. But since the article isn’t dated, I don’t know how recent it is. PLEASE DATE YOUR ARTICLES.
Canto: Yeah, and please do your research Jazz. That plant, announced in 2018, was scrapped last November. Apparently it was announced ahead of the 2018 election. And over-hyped, as it was never guaranteed that the ‘promised’ 500 jobs would be created. Politics.
Jacinta: Sad. Manufacturing has been in a sorry state in Australia for years. As Saul Griffith points out, we rely largely on the raw materials – crushed rocks – we export to keep our economy going, but if we could switch to other crushed rocks for the growing renewable energy economy we would be even better off. Further, if we added value through processing this material at home, we might be even better off financially, and we wouldn’t have to import those processed materials as we do now. Our two biggest imports are petrol and cars. If we could produce that stuff here we wouldn’t be paying for another country’s production costs, according to Griffith. Though I’m not quite sure if it’s that simple.
Canto: So you’re talking essentially about manufacturing in Australia. The Reserve Bank (RBA) has an interesting article on this topic, and here’s a quote from the opening summary:
Manufacturing output and employment have fallen steadily as a share of the Australian economy for the past three decades… the increase in the supply of manufactured goods from low-cost sources abroad, exacerbated by the appreciation of the Australian dollar during the period of rising commodity prices, impaired the viability of many domestic manufacturers and precipitated the closure of some manufacturing production over the past decade. While the recent exchange rate depreciation has helped to improve competitiveness of Australian producers, so far there is only limited evidence of a recovery in manufacturing output and investment.
Economics isn’t my strong suit, but I think I understand what ‘exchange rate depreciation’ means. Something like the exchange rate has swung a bit more in our favour (for home-grown manufacturing) than it was before..
Jacinta: But wouldn’t the exchange rate between us and other countries vary greatly from country to country? Or maybe they take an average, that’s to say of the countries we tend to trade with?
Canto: I suppose so. The article goes on to say that manufacturing hasn’t declined so much as commodity exports have increased. Commodities being raw materials, mostly. And by the way, this article is from the June quarter of 2016, and I suspect things have gotten worse for this gap between manufacturing and commodities. So, not so out-of date re trends. It claims that ‘over the 2000s, strong Asian demand for Australian commodities led to a sharp increase in the terms of trade and an appreciation of the Australian dollar’.
Jacinta: Well, we all appreciate the Aussie dollar…
Canto: Appreciation just means a rise in value. An increase in the terms of trade means an increase in the trading price agreed by any two countries, for example Australia and China, our big bogey man trading partner. Here it might mean beneficial terms of trade for Australia specifically. So basically, manufacturing has stagnated, and declined as a percentage of total output, which includes commodities. Manufacturing industries as an employer have declined quite sharply – as I can personally attest to. I’ve worked in five different factories in my life, all of which have since closed down – for which I take no responsibility.
Jacinta: So there would be a lack of skilled workers in manufacturing, unless… do we make solar panels here? And what about the old car factories we had here – Mitsubishis and Holdens, remember? Though I presume making EVs would require a whole different skill-set, and besides, wouldn’t it be largely automated?
Canto: Well, in February – that’s 2022 – the Australia Institute posted a highly optimistic media release entitled ‘Australia ready to become sustainable EV-making powerhouse: new research’. And with the new federal government elected in May, this hope, expressed in a report from the AI’s Carmichael Centre, Rebuilding Vehicle Manufacturing in Australia: Industrial Opportunities in an Electrified Future, may actually be realised, at least partially. But before I explore that report – solar photovoltaic manufacturing in Australia. A recent (early July) Guardian article reports that ‘China controls over 80% of the global photovoltaic (PV) solar supply chain, with one out of every seven panels produced worldwide being manufactured by a single factory’. And China is actually increasing production, so as to dominate the market. Diversification is urgently required. Meanwhile, Australia is suffering a labour shortage in the field. The International Energy Agency (IEA) has found that ‘one in three installation jobs in Australia – including electricians and installers – were unfilled and at risk of remaining unfilled in 2023’. Tindo Solar is our only home-grown PV manufacturer, and is expanding its output, but clearly this is dwarfed by China’s production. Also there’s a problem with expending production here because, currently, it actually creates more carbon emissions. We need to ‘create renewables with renewables’, which local experts are saying is now more cost-effective than ever. So, back to the report on vehicle manufacturing in Australia. It’s a job trying to access the full report, so I’ll rely on the media release. It describes our country as ‘uniquely blessed’ to rebuild our car manufacturing capabilities, retooled to EVs, but this will require essential government input – a view very much consistent with Griffith’s. Here are some of the recommendations from the report:
- Establishing an EV Manufacturing Industry Commission
- Using tax incentives to encourage firms involved in the extraction of key minerals – primarily lithium and rare earths – with local manufacturing capabilities, especially emerging Australian EV battery industries
- Introducing a long-term strategy for vocational training, ensuring the establishment of skills to service major EV manufacturers looking to set up operations Australia
- Offering major global manufacturers incentives (tax incentives, access to infrastructure, potential public capital participation, etc) to set up – especially in Australian regions undergoing transition from carbon-intensive industries
- Introducing local procurement laws for the rapid electrification of government vehicle fleets
Jacinta: So, as Griffith points out, we need to do some lobbying for this ourselves. Here in SA, we have a sympathetic state government as well as a federal government keen to make up for lost time, or at least saying all the right things. Where do we start?
Canto: The Clean Energy Council has a website that encourages everyone to get educated (they cite a number of resources such as Renew Economy and ARENA), to spread the word, and of course to actually invest in renewable energy, which we, as impoverished public housing renters, aren’t in a great position to do, though we are trying to get our Housing Association to explore renewable options, and to lobby the government in our name.
Jacinta: I think I’m starting to feel more optimistic…
References
Saul Griffith, The big switch: Australia’s electric future. 2022
Difference Between Black and Brown coal
Nem Watch
Australia ready to become sustainable EV-making powerhouse: new research
https://www.carmichaelcentre.org.au/rebuilding_vehicle_manufacture_in_australia
stand-alone solar: an off-grid solution for Australia’s remote regions (plus a bit of a rant)
According to this article, Australia is leading the world in per capita uptake of rooftop solar, though currently South Australia is lagging behind, in spite of a lot of clean energy action from our government. The Clean Energy Regulator has recently released figures showing that 23% of Australians have installed rooftop solar in the last ten years, and this take-up is set to continue in spite of the notable lack of encouragement from the feds. South Australia is still making plenty of waves re clean energy, though, as it is continually lowering its record for minimum grid demand, through the use of solar PV. The record set a couple of days ago, interestingly on Sunday afternoon rather than in the middle of the night, was 587MW, almost 200MW less than the previous record set only a week or so before. Clearly this trend is set to continue.
It’s hard for me to get my head around what’s happening re disruptive technologies, microgrids, stand-alone solar, EVs, battery research and the like, not to mention the horribly complex economics around these developments, but the sense of excitement brought about by comprehensive change makes me ever-willing to try. Only this morning I heard a story of six farming households described as being ‘on the fringe of Western Australia’s power network’ who’ve successfully trialled stand-alone solar panels (powered by lithium-ion batteries) on their properties, after years of outages and ‘voltage spikes’*. The panels – and this is the fascinating part – were offered free by Western Power (WA’s government-owned energy utility), who were looking for a cheaper alternative to the cost of replacing ageing infrastructure. The high costs of connecting remote farms to the grid make off-grid power systems a viable alternative, which raises issues about that viability elsewhere given the decreasing costs of solar PV, which can maintain electricity during power outages, as one Ravensthorpe family, part of the trial, discovered in January this year. The region, 500 kilometres south of Perth, experienced heavy rain and flooding which caused power failures, but the solar systems were unaffected. All in all, the trial has ‘exceeded expectations’, according to this ABC report.
All this has exciting implications for the future, but there are immediate problems. Though Western Power would like to sign off on the trial as an overwhelming success, and to apply this solution to other communities in the area (3,000 potential sites have been pinpointed), current regulation prevents this, as it only allows Western Power to distribute energy, not to generate it, as its solar installations are judged as doing. Another instance of regulations not keeping up with changing circumstances and solutions. Western Power has no alternative but to extend the trial period until the legislation catches up (assuming it does). But it would surely be a mistake not to change the law asap:
“You’d be talking about a saving of about $300 million in terms of current cost of investment and cost of ongoing maintenance of distribution line against the cost of the stand-alone power system,” Mr Chalkley [Western Power CEO] said.
Just as a side issue, it’s interesting that our PM Malcolm Turnbull, whose government seems on the whole to be avoiding any mention of clean energy these days, has had solar panels on his harbourside mansion in Point Piper, Sydney, for years. He now has an upgraded 14 kW rooftop solar array and a 14kWh battery storage system installed there, and, according to a recent interview he did on radio 3AW, he doesn’t draw any electricity from the grid, in spite of using a lot of electricity for security as Prime Minister. Solar PV plus battery, I’m learning, equals a distributed solar system. The chief of AEMO (the Australian Energy Market Operator), Audrey Zibelman, recently stated that distributed rooftop solar is on its way to making up 30 to 40% of our energy generation mix, and that it could be used as a resource to replace baseload, as currently provided by coal and gas stations (I shall write about baseload power issues, for my own instruction, in the near future).
Of course Turnbull isn’t exactly spruiking the benefits of renewable energy, having struck a Faustian bargain with his conservative colleagues in order to maintain his prestigious position as PM. We can only hope for a change of government to have any hope of a national approach to the inevitable energy transition, and even then it’ll be a hard road to hoe. Meanwhile, Tony Abbott, Turnbull’s arch-conservative bête noir, continues to represent the dark side. How did this imbecilic creature ever get to be our Prime Minister? Has he ever shown any signs of scientific literacy? Again I would urge extreme vetting of all candidates for political office, here and elsewhere, based on a stringent scientific literacy test. Imagine the political shite that would be flushed down the drain with that one. Abbott, you’ll notice, always talks of climate change and renewable energy in religious terms, as a modern religion. That’s because religion is his principal obsession. He can’t talk about it in scientific terms, because he doesn’t know any. Unfortunately, these politicians are rarely challenged by journalists, and are often free to choose friendly journalists who never challenge their laughable remarks. It’s a bit of a fucked-up system.
Meanwhile the ‘green religionists’, such as the Chinese and Indian governments, and the German and Scandinavian governments, and Elon Musk and those who invest in his companies, and the researchers and scientists who continue to improve solar PV, wind turbine and battery technology, including flow batteries, supercapacitors and so much more, are improving their developments and disrupting traditional ways of providing energy, and will continue to do so, in spite of name-calling from the fringes (to whom they’re largely deaf, due to the huge level of support from their supporters). It really is an exciting time not to be a dinosaur.