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capacitors, supercapacitors and electric vehicles

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from the video ‘what are supercapacitors’

Jacinta: New developments in battery and capacitor technology are enough to make any newbie’s head spin.

Canto: So what’s a supercapacitor? Apart from being a super capacitor?

Jacinta: I don’t know but I need to find out fast because supercapacitors are about to be eclipsed by a new technology developed in Great Britain which they estimate as being   ‘between 1,000 and 10,000-times more effective than current supercapacitors’.

Canto: Shite, they’ll have to think of a new name, or downgrade the others to ‘those devices formerly known as supercapacitors’. But then, I’ll believe this new tech when I see it.

Jacinta: Now now, let’s get on board, superdisruptive technology here we come. Current supercapacitors are called such because they can charge and discharge very quickly over large numbers of cycles, but their storage capacity is limited in comparison to batteries…

Canto: Apparently young Elon Musk predicted some time ago that supercapacitors would provide the next major breakthrough in EVs.

Jacinta: Clever he. But these ultra-high-energy density storage devices, these so-much-more-than-super-supercapacitors, could enable an EV to be charged to a 200 kilometre range in just a few seconds.

Canto: So can you give more detail on the technology?

Jacinta: The development is from a UK technology firm, Augmented Optics, and what I’m reading tells me that it’s all about ‘cross-linked gel electrolytes’ with ultra-high capacitance values which can combine with existing electrodes to create supercapacitors with greater energy storage than existing lithium-ion batteries. So if this technology works out, it will transform not only EVs but mobile devices, and really anything you care to mention, over a range of industries. Though everything I’ve read about this dates back to late last year, or reports on developments from then. Anyway, it’s all about the electrolyte material, which is some kind of highly conductive organic polymer.

Canto: Apparently the first supercapacitors were invented back in 1957. They store energy by means of static charge, and I’m not sure what that means…

Jacinta: We’ll have to do a post on static electricity.

Canto: In any case their energy density hasn’t been competitive with the latest batteries until now.

Jacinta: Yes it’s all been about energy density apparently. That’s one of the main reasons why the infernal combustion engine won out over the electric motor in the early days, and now the energy density race is being run between new-age supercapacitors and batteries.

Canto: So how are supercapacitors used today? I’ve heard that they’re useful in conjunction with regenerative braking, and I’ve also heard that there’s a bus that runs entirely on supercapacitors. How does that work?

Jacinta: Well back in early 2013 Mazda introduced a supercapacitor-based regen braking system in its Mazda 6. To quote more or less from this article by the Society of Automotive Engineers (SAE), kinetic energy from deceleration is converted to electricity by the variable-voltage alternator and transmitted to a supercapacitor, from which it flows through a dc-dc converter to 12-V electrical components.

Canto: Oh right, now I get it…

Jacinta: We’ll have to do posts on alternators, direct current and alternating current. As for your bus story, yes, capabuses, as they’re called, are being used in Shanghai. They use supercapacitors, or ultracapacitors as they’re sometimes called, for onboard power storage, and this usage is likely to spread with the continuous move away from fossil fuels and with developments in supercaps, as I’ve heard them called. Of course, this is a hybrid technology, but I think they’ll be going fully electric soon enough.

Canto: Or not soon enough for a lot of us.

Jacinta: Apparently, with China’s dictators imposing stringent emission standards, electric buses, operating on power lines (we call them trams) became more common. Of course electricity may be generated by coal-fired power stations, and that’s a problem, but this fascinating article looking at the famous Melbourne tram network (run mainly on dirty brown coal) shows that with high occupancy rates the greenhouse footprint per person is way lower than for car users and their passengers. But the capabuses don’t use power lines, though they apparently run on tracks and charge regularly at recharge stops along the way. The technology is being adopted elsewhere too of course.

Canto: So let me return again to basics – what’s the difference between a capacitor and and a super-ultra-whatever-capacitor?

Jacinta: I think the difference is just in the capacitance. I’m inferring that because I’m hearing, on these videos, capacitors being talked about in terms of micro-farads (a farad, remember, being a unit of capacitance), whereas supercapacitors have ‘super capacitance’, i.e more energy storage capability. But I’ve just discovered a neat video which really helps in understanding all this, so I’m going to do a breakdown of it. First, it shows a range of supercapacitors, which look very much like batteries, the largest of which has a capacitance, as shown on the label, of 3000 farads. So, more super than your average capacitor. It also says 2.7 V DC, which I’m sure is also highly relevant. We’re first told that they’re often used in the energy recovery system of vehicles, and that they have a lower energy density (10 to 100 times less than the best Li-ion batteries), but they can deliver 10 to 100 times more power than a Li-ion battery.

Canto: You’ll be explaining that?

Jacinta: Yes, later. Another big difference is in charge-recharge cycles. A good rechargeable battery may manage a thousand charge and recharge cycles, while a supercap can be good for a million. And the narrator even gives a reason, which excites me – it’s because they function by the movement of ions rather than by chemical reactions as batteries do. I’ve seen that in the videos on capacitors, described in our earlier post. A capacitor has to be hooked up to a battery – a power source. So then he uses an analogy to show the difference between power and energy, and I’m hoping it’ll provide me with a long-lasting lightbulb moment. His analogy is a bucket with a hole. The amount of water the bucket can hold – the size of the bucket if you like – equates to the bucket’s energy capacity. The size of the hole determines the amount of power it can release. So with this in mind, a supercar is like a small bucket with a big hole, while a battery is more like a big bucket with a small hole.

Canto: So the key to a supercap is that it can provide a lot of power quickly, by discharging, then it has to be recharged. That might explain their use in those capabuses – I think.

Jacinta: Yes, for regenerative braking, for cordless power tools and for flash cameras, and also for brief peak power supplies. Now I’ve jumped to another video, which inter alia shows how a supercapacitor coin cell is made – I’m quite excited about all this new info I’m assimilating. A parallel plate capacitor is separated by a non-conducting dielectric, and its capacitance is directly proportional to the surface area of the plates and inversely proportional to the distance between them. Its longer life is largely due to the fact that no chemical reaction occurs between the two plates. Supercapacitors have an electrolyte between the plates rather than a dielectric…

Canto: What’s the difference?

Jacinta: A dielectric is an insulating material that causes polarisation in an electric field, but let’s not go into that now. Back to supercapacitors and the first video. It describes one containing two identical carbon-based high surface area electrodes with a paper-based separator between. They’re connected to aluminium current collectors on each side. Between the electrodes, positive and negative ions float in an electrolyte solution. That’s when the cell isn’t charged. In a fully charged cell, the ions attach to the positively and negatively charged electrodes (or terminals) according to the law of attraction. So, our video takes us through the steps of the charge-storage process. First we connect our positive and negative terminals to an energy source. At the negative electrode an electrical field is generated and the electrode becomes negatively charged, attracting positive ions and repelling negative ones. Simultaneously, the opposite is happening at the positive electrode. In each case the ‘counter-ions’ are said to adsorb to the surface of the electrode…

Canto: Adsorption is the adherence of ions – or atoms or molecules – to a surface.

Jacinta: So now there’s a strong electrical field which holds together the electrons from the electrode and the positive ions from the electrolyte. That’s basically where the potential energy is being stored. So now we come to the discharge part, where we remove electrons through the external surface, at the electrode-electrolyte interface we would have an excess of positive ions, therefore a positive ion is repelled in order to return the interface to a state of charge neutrality – that is, the negative charge and the positive charge are balanced. So to summarise from the video, supercapacitors aren’t a substitute for batteries. They’re suited to different applications, applications requiring high power, with moderate to low energy requirements (in cranes and lifts, for example). They can also be used as voltage support for high-energy devices, such as fuel cells and batteries.

Canto: What’s a fuel cell? Will we do a post on that?

Jacinta: Probably. The video mentions that Honda has used a bank of ultra capacitors in their FCX fuel-cell vehicle to protect the fuel cell (whatever that is) from rapid voltage fluctuations. The reliability of supercapacitors makes them particularly useful in applications that are described as maintenance-free, such as space travel and wind turbines. Mazda also uses them to capture waste energy in their i-Eloop energy recovery system as used on the Mazda 6 and the Mazda 3, which sounds like something worth investigating.

References (videos can be accessed from the links above)


Written by stewart henderson

September 5, 2017 at 10:08 am

How will the super-duper Tesla battery work? And more on the price of electricity

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Image: Thermo Fisher Scientific Inc.

I received an email the other day from the Australia Insitute. I don’t know how that happened, I’ve never heard of the organisation. Apparently it’s Australia’s most influential progressive think-tank (self-described) and apparently I subscribed to it recently while in a barely conscious state. All good.

Anyway the topic was timely: ‘Rising Energy Bills: Blame Gas’.

In a very recent post I quoted from a few apparently reliable sources on the reason for South Australia’s very high electricity prices. Unfortunately there wasn’t too much agreement among them, though at least none of them blamed renewable energy. But neither did any of them blame gas, though one did point a finger at wholesale pricing. The Australia Institute’s email put it thus:

Yesterday, we released the latest Electricity Update of the National Energy Emissions Audit for July 2017. The report revealed a stunning correlation between domestic electricity prices and gas prices — particularly in South Australia — despite gas making up only 10 percent of electricity generation.

So this is a subject I need to return to – in my next post. This post will focus on batteries and storage.

Neoen, a French renewable energy company, is building a 315MW, 99 turbine wind farm near Jamestown in South Australia. Connected to this project will be an array of Tesla’s lithium ion Powerpack batteries. According to this ABC News article:

The array will be capable of an output of 100 megawatts (MW) of power at a time and the huge battery will be able to store 129 megawatt hours (MWh) of energy so, if used at full capacity, it would be able to provide its maximum output for more than an hour.

It will be a modular network, with each Powerpack about the size of a large fridge at 2.1 metres tall, 1.3m long and 0.8m wide. They weigh in at 1,200 kilograms each.

It will have just slightly more storage than the next biggest lithium battery, built by AES this year in southern California.

But Tesla’s 100 MW output would be more than three times larger than the AES battery and five times larger than anything Tesla has built previously.

I’m no electrochemist, but a nice scrutiny of these sentences identifies a clear distinction between output and storage. And the output of this planned battery is the pioneering aspect.

So here’s a very basic summary of how a rechargeable lithium ion battery works. Each battery (and they vary hugely in size) is made up of a number of cells, each a battery in itself. On opposite sides of the cell are conductive surfaces, aka current collectors, one of aluminium and the other of copper. Inside and joined to these surfaces are electrodes, the positive cathode and the negative anode. The cathode is made from a lithium metal oxide such as lithium cobalt oxide or lithium iron phosphate, which needs to have the purest, most uniform composition for maximum performance and longevity. The negative anode is made from graphite, a layered form of carbon. The layered structure allows the lithium ions (Li+) created by the current to be easily stored at and removed from the carbon surface. Between these electrodes, filling the cell, is an electrolyte fluid through which lithium ions flow from one electrode to the other, which charges and discharges the cell. Again the purity of this fluid is a vital factor (research is being done to come up with a form of solid electrolyte). Between the two electrodes is an insulating plastic separator, essential to keep the electrodes separate and prevent short-circuiting. This plastic membrane allows the lithium ions to pass through it. The battery is charged when the lithium ions have passed through the separator and become attached to and stored in the layered graphite of the anode. The battery is discharged by reversing the flow.

Lithium ion batteries are found not only in Tesla Powerpacks but generally in electric car batteries and many other devices such as my own iPhone and iPad. They’re lighter and have much less energy density than lead-acid batteries. The technology of lithium ion batteries is described in a number of useful online videos, of which the most comprehensive, I think, is a webinar from the American Chemistry Society (ACS), essentially an interview with Dee Strand, a lithium ion battery specialist and expert. Her talk also provides interesting ideas on how these types of batteries can be improved.

So a fully-charged cell has stored energy, and a discharging cell is producing output. There are variations in lithium ion battery technology, for example variations in the electrode materials, the electrolyte composition and the like, so we don’t know precisely what Tesla will be using for the South Australian battery system, but we have a fair idea.

In any case, there seems no obvious reason why this proven technology can’t be scaled up to meet the sort of need that was identified after last September’s state blackout. Now we just have to wait and see whether Musk will lose his bet regarding completion time come December.

Refs and info

Just type in ‘lithium ion battery’ in youtube



Written by stewart henderson

July 19, 2017 at 1:00 pm

What’s Weatherill’s plan for South Australia, and why do we have the highest power prices in the world? Oh, and I should mention Elon Musk here – might get me more hits

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just a superhero pic to rope people in

I’ve written a few pieces on our electricity system here in SA, but I don’t really feel any wiser about it. Still, I’ll keep having a go.

We’ve become briefly famous because billionaire geek hero Elon Musk has promised to build a ginormous battery here. After we had our major blackout last September (for which we were again briefly famous), Musk tweeted or otherwise communicated that his Tesla company might be able to solve SA’s power problems. This brought on a few local geek-gasms, but we quickly forgot (or I did), not realising that our good government was working quietly behind the scenes to get Musk to commit to something real. In March this year, Musk was asked to submit a tender for the 100MW capacity battery, which is expected to be operational by the summer. He has recently won the tender, and has committed to constructing the battery in 100 days, at a cost of $50 million. If he’s unsuccessful within the time limit, we’ll get it for free.

There are many many South Australians who are very skeptical of this project, and the federal government is saying that the comparatively small capacity of the battery system will have minimal impact on the state’s ‘self-imposed’ problems. And yet – I’d be the first to say that I’m quite illiterate about this stuff, but if SA Premier Jay Weatherill’s claim is true that ‘battery storage is the future of our national energy market’, and if Musk’s company can build this facility quickly, then it’s surely possible that many batteries could be built like the one envisaged by Musk, each one bigger and cheaper than the last. Or have I just entered cloud cuckoo land? Isn’t that how technology tends to work?

In any case, the battery storage facility is designed to bring greater stability to the state’s power network, not to replace the system, so the comparisons made by Federal Energy Minister Josh Frydenberg are misleading, probably deliberately so. Frydenberg well knows, for example, that SA’s government has been working on other solutions too, effectively seeking to becoming independent of the eastern states in respect of its power system. In March, at the same time as he presented plans for Australia’s largest battery, Weatherill announced that a taxpayer-funded 250MW gas-fired power plant would be built. More recently, AGL, the State’s largest power producer and retailer, has announced  plans to build a 210MW gas-fired generator on Torrens Island, upgrading its already-existing system. AGL’s plan is to use reciprocating engines, which executive general manager Doug Jackson has identified as best suited to the SA market because of their ‘flexible efficient and cost-effective synchronous generation capability’. I heartily agree. It’s noteworthy that the AGL plan was co-presented by its managing director Andy Vesey and the SA Premier. They were at pains to point out that the government plans and the AGL plan were not in competition. So it does seem that the state government has made significant strides in ensuring our energy security, in spite of much carping from the Feds as well as local critics – check out some of the very nasty naysaying in the comments section of local journalist Nick Harmsen’s articles on the subject (much of it about the use of lithium ion batteries, which I might blog about later).

It’s also interesting that Harmsen himself, in an article written four months ago, cast serious doubt on the Tesla project going ahead, because, as far as he knew, tenders were already closed on the battery storage or ‘dispatchable renewables’ plan, and there were already a number of viable options on the table. So either the Tesla offer, when it came (and maybe it got in under the deadline unbeknown to Harmsen), was way more impressive than others, or the Tesla-Musk brand has bedazzled Weatherill and his cronies. It’s probably a combo of the two. Whatever, this news is something of a blow to local rivals. What is fascinating, though is how much energetic rivalry, or competition, there actually is in the storage and dispatchables field, in spite of the general negativity of the Federal government. It seems our centrist PM Malcolm Turnbull is at odds with his own government about this.

So enough about the Tesla-Neoen deal, and associated issues, which are mounting too fast for me to keep up with right now. I want to focus on pricing for the rest of this piece, because I have no understanding of why SA is now paying the world’s highest domestic electricity prices, as the media keeps telling us.

According to this Sydney Morning Herald article from nearly two years ago, which of course I can’t vouch for, Australia’s electricity bills are made up of three components: wholesale and retail prices, based on supply and demand (39% of cost); the cost of poles and wires (53%); and the cost of environmental policies (8%). The trio can be simplified as market, network and environmental costs. Market and network costs vary from state to state. The biggest cost, the poles and wires, is borne by all Australian consumers (at least all on the grid), as a result of a massive $45 billion upgrade between 2009 and 2014, due to expectations of a continuing rise in demand. Instead there’s been a fall, partly due to domestic solar but in large measure because of much tighter and more environmental building standards nationwide as part of the building boom. The SMH article concludes, a little unexpectedly, that the continuing rise in prices can only be due to retail price hikes, at least in the eastern states, because supply is steady and network costs, though high, are also steady.

A more recent article (December 2016) argues that a rising wholesale price, due to the closure of coal-fired power stations in SA and Victoria and higher gas prices, is largely responsible. Retail prices are higher now than when the carbon tax was in place in 2013.

This even recenter article from late March announces an inquiry by the Australian Competition and Consumer Commission (ACCC) into retail pricing of electricity, which unfortunately won’t be completed till June 30 2018, given its comprehensive nature. It also contains this telling titbit:

A report from the Grattan Institute released earlier in March found a decade of competition in the market had failed to deliver better deals for customers, with profit margins on electricity bills much higher than for many other industries.

However, another article published in March, and focusing on SA’s power prices in particular (it’s written by former SA essential services commissioner Richard Blandy), takes an opposing view:

Retailing costs are unlikely to be a source of rapidly rising electricity prices because they represent a small proportion of final prices to consumers and there is a high level of competition in this part of the electricity supply chain. Energy Watch shows that there are seven electricity retailers selling electricity to small businesses, and 12 electricity retailers selling electricity to households. Therefore, price rises at the retail level are likely to be cost-based.

Blandy’s article, which looks at transmission and distribution pricing, load shedding and the very complex issue of wholesale pricing and the National Energy Market (NEM), needs at least another blog post to do justice to. I’m thinking that I’ll have to read and write a lot more to make sense of it all.

Finally, the most recentest article of only a couple of weeks ago quotes Bruce Mountain, director of Carbon and Energy Markets, as saying that it’s not about renewables (SA isn’t much above the other states re pricing), it’s about weak government control over retailers (could there be collusion?). Meanwhile, politicians obfuscate, argue and try to score points about a costly energy system that’s failing Australian consumers.

I’ll be concentrating a lot on this multifaceted topic – energy sources, storage, batteries, pricing, markets, investment and the like, in the near future. It exercises me and I want to educate myself further about it. Next, I’ll make an effort to find out more about, and analyse, the South Australian government’s six-point plan for our energy future.

References and more reading for masochists

Written by stewart henderson

July 14, 2017 at 10:55 am