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reflections on base load, dispatchable energy and SA’s current situation

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just to restate the point that SA’s power outages are due to transmission/distribution lines being damaged, nothing to do with renewable energy

Canto: So now we’re going to explore base load. What I think it means is reliable, always available energy, usually from fossil fuel generators (coal oil gas), always on tap, to underpin all this soi-disant experimental energy from solar (but what about cloudy days, not to mention darkness, which is absence of light, which is waves of energy isn’t it?) and wind (which is obviously variable, from calm days to days so stormy that they might uproot wind turbines and send them flying into space, chopping up birds in the process).

Jacinta: Well we can’t think about base load without thinking about grids. Our favourite Wikipedia describes it as ‘the minimal level of demand on an electrical grid over a span of time’. So the idea is that you always need to cover that base, or you’ll be in trouble. And an electrical grid is a provision of electrical service to a particular community, be it a suburb, a city or a state. 

Canto: Right, I think, and what I like about Wikipedia is the way it sticks it to the back-facing thinkers, for whom base load always means provision from traditional providers (coal oil gas). 

Jacinta: Yes, let’s rub it in by quoting Wikipedia on this. 

When the cheapest power was from large coal and nuclear plants which could not be turned up or down quickly, they were used to generate baseload, since it is constant, and they were called “baseload plants.” Large standby reserves were needed in case of sudden failure of one of these large plants. Unvarying power plants are no longer always the cheapest way to meet baseload. The grid now includes many wind turbines which have such low marginal costs that they can bid lower prices than coal or nuclear, so they can provide some of the baseload when the wind blows. Using wind turbines in areas with varying wind conditions, and supplementing them with solar in the day time, dispatchable generation and storage, handles the intermittency of individual wind sources.

Canto: So the times are a-changing with respect to costs and supply, especially as costs to the environment of fossil fuel supplies are at last being factored in, at least in some parts of the world. But let’s keep trying to clarify terms. What about dispatchable generation, and how does it relate to base load?

Jacinta: Well, intermittent power sources, such as wind and solar, are not dispatchable – unless there’s a way to store that energy. Some renewable energy sources, such as geothermal and biomass, are dispatchable, but they don’t figure too much in the mix at present. The key is in the word – these sources are able to be dispatched on demand, and have adjustable output which can be regulated in one way or another. But some sources are easier, and cheaper, to switch on and off than others. It’s much about timing; older generation coal-fired plants can take many hours to ‘fire up’, so their dispatchability, especially in times of crisis, is questionable. Hydroelectric and gas plants can respond much more quickly, and batteries, as we’ve seen, can respond in microseconds in times of crisis, providing a short-term fix until other sources come on stream. Of course, this takes us into the field of storage, which is a whole other can of – what’s the opposite of worms?

Canto: So this question of base load, this covering of ‘minimal’ but presumably essential level of demand, can be a problem for a national grid, but you can break that grid up presumably, going ‘off grid’, which I’m guessing means going off the national grid and either being totally independent as a household or creating a micro-grid consisting of some small community…

Jacinta: Yes and this would be the kind of ‘disruptive economy’ that causes nightmares for some governments, especially conservative ones, not to mention energy providers and retailers. But leaving aside micro-grids for now, this issue of dispatchability can be dealt with in a flexible way without relying on fossil fuels. Energy storage has proven value, perhaps especially with smaller grids or micro-grids, for example in maintaining flow for a particular enterprise. On the larger scale, I suppose the Snowy 2 hydro project will be a big boon? 

Canto: 2000 megawatts of energy generation and 175 hours of storage says the online ‘brochure’. But the Renew Economy folks, who always talk about ‘so-called’ base load, are skeptical. They point to the enormous cost of the project, which could escalate, due, among other things, to the difficulties of tunnelling through rock of uncertain quality. They feel that government reports have over-hyped the project and significantly downplayed the value of alternatives, such as battery electric storage systems, which are modular and flexible rather than this massive one-off project which may be rendered irrelevant once completed. 

Jacinta: So let’s relate this to the South Australian situation. We’re part of the national grid, or the National Energy Market (NEM), which covers SA and the eastern states. This includes generators, transformers (converting low voltage to high voltage for transport, and then converting back to low voltage for distribution), long distance transmission lines and shorter distance distribution lines. So that’s wholesale stuff, and it’s a market because different companies are involved in producing and maintaining the system – the grid, if you like.

Canto: I’ve heard it’s the world’s largest grid, in terms of area covered.

Jacinta: I don’t think so, but it depends on what metric you use. Anyway, it’s pretty big. South Australia has been criticised by the federal government for somehow harming the market with its renewables push. Also, it was claimed at least a year ago that SA had the highest electricity prices in the world. This may have been an exaggeration, but why are costs so high here? There are green levies on our bill, but I think they’re optional. Also, the electricity system was privatised in the late 90s, so the government has lost control of pricing. High-voltage transmission lines are owned by ElectraNet, part-owned by the Chinese government. The lower voltage distribution lines are operated by SA Power Networks, majority-owned by a Hong Kong company, and then there are the various private retailers. It’s hard to work out, amongst all this, why prices are so high here, but the closure of the Northern coal-fired power station in Port Augusta, which was relatively low cost and stable, meant a greater reliance on more expensive gas. Wind and solar have greater penetration into the SA network than elsewhere, but there’s still the intermittency problem. Various projects currently in the pipeline will hopefully provide more stability in the future, including a somewhat controversial interconnector between SA and NSW. Then there’s the retail side of things. Some retailers are also wholesalers. For instance AGL supplies 48% of the state’s retail customers and controls 42% of generation capacity. All in all, there’s a lack of competition, with only three companies competing for the retail market, which is a problem for pricing. At the same time, if competitors can be lured into the market, rather than being discouraged by monopoly behaviour, the high current prices should act as an incentive. 

Canto: Are you suggesting that retailers are profiteering from our high prices?

Jacinta: I don’t know about that, but before the Tesla battery came online the major gas generators – who are also retailers – were using their monopoly power to engage in price gouging at times of scarcity, to a degree that was truly incredible – more so in that it was entirely legal according to the ACCC and other market regulators. The whole sorry story is told here . So I’m hoping that’s now behind us, though I’m sure the executives of these companies will have earned fat bonuses for exploiting the situation while they could. 

Canto: So prices to consumers in SA have peaked and are now going down?

Jacinta: Well the National Energy Market has suffered increased costs for the past couple of years, mainly due to the increased wholesale price of gas, on which SA is heavily reliant. It’s hard to get reliable current data on this online, but as of April this year the east coast gas prices were on their way down, but these prices fluctuate for all sorts of reasons. Of course the gas lobby contends that increased supply – more gas exploration etc – will solve the problem, while others want to go in the opposite direction and cut gas out of the South Australian market as much as possible. That’s unlikely to happen though, in the foreseeable, so we’re likely to be hostage to fluctuating gas prices, and a fair degree of monopoly pricing, for some time to come. 


Written by stewart henderson

November 26, 2018 at 11:37 am

the continuing story of South Australia’s energy solutions

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In a very smart pre-election move, our state Premier Jay Weatherill has announced that there’s a trial under way to install Tesla batteries with solar panels on over 1,000 SA Housing Trust homes. The ultimate, rather ambitious aim, is to roll this out to 50,000 SA homes, thus creating a 250MW power plant, in essence. And not to be outdone, the opposition has engaged in a bit of commendable me-tooism, with a similar plan, actually announced last October. This in spite of the conservative Feds deriding SA labor’s ‘reckless experiments’ in renewables.

Initially the plan would be offered to public housing properties – which interests me, as a person who’s just left a solarised housing association property for one without solar. I’m in community housing, a subset of public housing. Such a ‘virtual’ power plant will, I think, make consumers more aware of energy resources and consumption. It’s a bit like owning your own bit of land instead of renting it. And it will also bring down electricity prices for those consumers.

This is a really important and exciting development, adding to and in many ways eclipsing other recently announced developments in SA, as written about previously. It will be, for a time at least, the world’s biggest virtual power plant, lending further stability to the grid. It’s also a welcome break for public housing tenants, among the most affected by rising power bills (though we’ll have to wait and see if prices do actually come down as a result of all this activity).

And the announcements and plans keep coming, with another big battery – our fourth – to be constructed in the mid-north, near Snowtown. The 21MW/26MWh battery will be built alongside a 44MW solar farm in the area (next to the big wind farm).

 

South Australia’s wind farms

Now, as someone not hugely well-versed in the renewable energy field and the energy market in general, I rely on various websites, journalists and pundits to keep me honest, and to help me make sense of weird websites such as this one, the apparent aim of which is to reveal all climate scientists as delusionary or fraudsters and all renewable energy as damaging or wasteful. Should they (these websites) be tackled or ignored? As a person concerned about the best use of energy, I think probably the latter. Anyway, one journalist always worth following is Giles Parkinson, who writes for Renew Economy, inter alia. In this article, Parkinson focuses on FCAS (frequency control and ancillary services), a set of network services overseen by AEMO, the Australian Energy Market Operator. According to Parkinson and other experts, the provision of these services has been a massive revenue source for an Australian ‘gas cartel’, which has been rorting the system at the expense of consumers, to the tune of many thousands of dollars. Enter the big Tesla battery , officially known as the Hornsdale Power Reserve (HPR), and the situation has changed drastically, to the benefit of all:

Rather than jumping up to prices of around $11,500 and $14,000/MW, the bidding of the Tesla big battery – and, in a major new development, the adjoining Hornsdale wind farm – helped (after an initial spike) to keep them at around $270/MW.

This saved several million dollars in FCAS charges (which are paid by other generators and big energy users) in a single day.

And that’s not the only impact. According to state government’s advisor, Frontier Economics, the average price of FCAS fell by around 75 per cent in December from the same month the previous year. Market players are delighted, and consumers should be too, because they will ultimately benefit. (Parkinson)

As experts are pointing out, the HPR is largely misconceived as an emergency stop-gap supplier for the whole state. It has other, more significant uses, which are proving invaluable. Its effect on FCAS, for example, and its ultra-ultra-quick responses to outages at major coal-fired generators outside of the state, and ‘its smoothing of wind output and trading in the wholesale market’. The key to its success, apparently, is its speed of effect – the ability to switch on or off in an instant.

Parkinson’s latest article is about another SA govt announcement – Australia’s first renewable-hydrogen electrolyser plant at Port Lincoln.

I’ve no idea what that means, but I’m about to find out – a little bit. I do know that once-hyped hydrogen hasn’t been receiving so much support lately as a fuel – though I don’t even understand how it works as a fuel. Anyway, this plant will be ten times bigger than one planned for the ACT as part of its push to have its electricity provided entirely by renewables. It’s called ‘green hydrogen’, and the set-up will include a 10MW hydrogen-fired gas turbine (the world’s largest) driven by local solar and wind power, and a 5MW hydrogen fuel cell. Parkinson doesn’t describe the underlying technology, so I’ll have a go.

It’s all about electrolysis, the production of hydrogen from H2O by the introduction of an electric current. Much of what follows comes from a 2015 puff piece of sorts from the German company Siemens. It argues, like many, that there’s no universal solution for electrical storage, and, like maybe not so many, that large-scale storage can only be addressed by pumped hydro, compressed air (CAES) and chemical storage media such as hydrogen and methane. Then it proceeds to pour cold water on hydro – ‘the potential to extend its current capacity is very limited’ – and on CAES ‘ – ‘has limitations on operational flexibility and capacity. I know nothing about CAES, but they’re probably right about hydro. Here’s their illustration of the process they have in mind, from generation to application.

Clearly the author of this document is being highly optimistic about the role of hydrogen in end-use applications. Don’t see too many hydrogen cars in the offing, though the Port Lincoln facility, it’s hoped, will produce hydrogen ‘that can be used to power fuel cell vehicles, make ammonia, generate electricity in a turbine or fuel cell, supply industry, or to export around the world’.

So how does electrolysis (of water) actually work? The answer, of course, is this:

2 H2O(l) → 2 H2(g) + O2(g); E0 = +1.229 V

Need I say more? On the right of the equation, E0 = +1.229 V, which basically means it takes 1.23 volts to split water. As shown above, Siemens is using PEM (Proton Exchange Membrane, or Polymer Electrolyte Membrane) electrolysis, though alkaline water electrolysis is another effective method. Not sure which which method is being used here.

In any case, it seems to be an approved and robust technology, and it will add to the variety of ‘disruptive’ and innovative plans and processes that are creating more regionalised networks throughout the state. And it gives us all incentives to learn more about how energy can be produced, stored and utilised.

Written by stewart henderson

February 14, 2018 at 4:50 pm

more on Australia’s energy woes and solutions

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the SA Tesla Powerpack, again

Canto: So the new Tesla battery is now in its final testing phase, so South Australia can briefly enjoy some fame as having the biggest battery in the world, though I’m sure it’ll be superseded soon enough with all the activity worldwide in the battery and storage field.

Jacinta: Well I don’t think we need to get caught up with having the biggest X in the world, it’s more important that we’re seen as a place for innovation in energy storage and other matters energetic. So, first, there’s the Tesla battery, associated with the Hornsdale wind farm near Jamestown, and there are two other major battery storage systems well underway, one in Whyalla, designed for Whyalla Steel, to reduce their energy costs, and another smaller system next to AGL’s Wattle Point wind farm on Yorke Peninsula.

Canto: Well, given that the federal government likes to mock our Big Battery, can you tell me how the Tesla battery and the other batteries work to improve the state?

Jacinta: It’s a 100MW/129MWh installation, designed to serve two functions. A large portion of its stored power (70MW/39MWh) is for the state government to stabilise the grid in times of outage. Emergency situations. This will obviously be a temporary solution before other, slower reacting infrastructure can be brought into play. The rest is owned by Neoen, Tesla’s partner company and owner of the wind farm. They’ll use it to export at a profit when required – storing at low prices, exporting at higher prices. As to the Whyalla Steel battery, that’s privately owned, but it’s an obvious example, along with the AGL battery, of how energy can be produced and stored cleanly (Whyalla Steel relies on solar and hydro). They point the way forward.

Canto: Okay here’s a horrible question, because I doubt if there’s any quick ‘for dummies’ answer. What’s the difference between megawatts and megawatt-hours?

Jacinta: A megawatt, or a watt, is a measure of power, which is the rate of energy transfer. One watt equals one joule per second, and a megawatt is 1,000,000 watts, or 1,000 kilowatts. A megawatt-hour is one megawatt of power flowing for one hour.

Canto: Mmmm, I’m trying to work out whether I understand that.

Jacinta: Let’s take kilowatts. A kilowatt (KW) is 1,000 times the rate of energy transfer of a watt. In other words, 1000 joules/sec. One KWh is one hour at that rate of energy transfer. So you multiply the 1000 by 3,600, the number of seconds in an hour. That’s a big number, so you can express it in megajoules – the answer is 3.6Mj. One megajoule equals 1,000,000 joules of course.

Canto: Of course. So how is this working for South Australia’s leadership on renewables and shifting the whole country in that direction?

Genex Power site in far north Queensland – Australia’s largest solar farm together with a pumped hydro storage plant

Jacinta: Believe me it’s not all South Australia. There are all sorts of developments happening around the country, mostly non-government stuff, which I suppose our rightist, private enterprise feds would be very happy with. For example there’s the Genex Power solar, hydro and storage project in North Queensland, situated in an old gold mine. Apparently pumped hydro storage is a competitor with, or complementary to, battery storage. Simon Kidston, the Genex manager, argues that many other sites can be repurposed in this way.

Canto: And the cost of wind generation and solar PV is declining at a rate far exceeding expectations, especially those of government, precisely because of private enterprise activity.

Jacinta: Well, mainly because it’s a global market, with far bigger players than Australia. Inputs into renewables from states around the world – India, Mexico, even the Middle East – are causing prices to spiral down.

Canto: And almost as we speak the Tesla gridscale battery has become operational, and we’ve gained a tiny place in history. But what about this National Energy Guarantee from the feds, which everyone seems to be taking a swing at. What’s it all about?

Jacinta: This was announced a little over a month ago, as a rejection of our chief scientist’s Clean Energy Target. Note how the Feds again avoid using such terms as ‘clean’ and ‘renewable’ when it talks or presents energy policy. Anyway, it may or may not be a good thing – there’s a summary of what some experts are saying about it online, but most are saying it’s short on detail. It’s meant to guarantee a reliable stream of energy/electricity from retailers, never mind how the energy is generated – so the government can say it’s neither advocating nor poo-pooing renewables, it’s getting out of the way and letting retailers, some of whom are also generators, deliver the energy from whatever source they like, or can.

Canto: So they’re putting the onus on retailers. How so?

Jacinta: The Feds are saying retailers will have to make a certain amount of dispatchable power available, but there is one ridiculously modest stipulation – greenhouse emissions from the sector must be reduced by 26% by 2030. The sector can and must do much better than that. The electricity sector makes up about a third of emissions, and considering the slow movement on EVs and on emissions reductions generally, we’re unlikely to hold up our end of the Paris Agreement, considering the progressively increasing targets.

Canto: But that’s where they leave it up to the private sector. To go much further than their modest target. They would argue that they’re more interested in energy security.

Jacinta: They have a responsibility for providing security but not for reducing emissions? But it’s governments that signed up to Paris, not private enterprises. The experts are pointing this out with regard to other sectors. More government-driven vehicle emission standards, environmental building regulations, energy efficient industries and so forth.

Canto: And the Feds actually still have a renewable energy agency (ARENA), in spite of the former Abbott government’s attempt to scrap it, and a plan was announced last month to set up a ‘demand response’ trial, involving ARENA, AEMO (the energy market operator) and various retailers and other entities. This is about providing temporary supply during peak periods – do you have any more detail?

Jacinta: There’s a gloss on the demand response concept on a Feds website:

From Texas to Taiwan, demand response is commonly used overseas to avoid unplanned or involuntary outages, ease electricity price spikes and provide grid support services. In other countries, up to 15 per cent of peak demand is met with demand response.

Canto: So what exactly does it have to do with renewables?

Jacinta: Well get ready for a long story. It’s called demand response because it focuses on the play of demand rather than supply. It’s also called demand management, a better name I think. It’s partly about educating people about energy not being a finite commodity available at all times in equal measure…

Canto: Sounds like it’s more about energy conservation than about the type of energy being consumed.

Jacinta: That’s true. So on extreme temperature days, hot or cold – but mostly hot days in Australia – electricity demand can jump by 50% or so. To cope with these occasional demand surges we’ve traditionally built expensive gas-based generators that lie idle for most of the year. For reasons I’m not quite able to fathom, at such extreme demand times the ‘spot price’ for wholesale electricity goes through the roof – or more accurately it hits the ceiling, set by the National Energy Market at $14,000 per MWh. That’s just a bit more than the usual wholesale price, about $100/MWh. Demand management is an attempt to have agreements with large commercial/industrial users to reduce usage at certain times, or the agreements could be with energy retailers who then do deals with customers. Of course, bonuses could be handed out to compliant customers. The details of how this offsets peak demand usage and pricing are still a bit of a mystery to me, however.

Written by stewart henderson

December 9, 2017 at 9:07 pm

an assortment of new technology palaver

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I like the inset pic – very useful for the Chinese

Western Australia lithium mining boom

I’m hearing, better late than never, that lithium carbonate from Western Australia is in big demand. The state already provides most of the world’s lithium for all those batteries used to run smart devices, electric vehicles, and large-scale storage batteries such as South Australia’s Tesla-Neoen thingy at Jamestown (now 80% complete, apparently). Emissions legislation around the world will only add to the demand, with the French and British governments planning to ban the sale of petrol and diesel vehicles by 2040, following similar plans by India and Norway, and the major investments in EVs in China. Australia’s government, of course, is at the other end of the spectrum re EVs, but I’ve no doubt we’ll get there eventually (we’ll have to!). Tesla, Volvo, Nissan, Renault, Volkswagen and Mercedes are all pushing more EVs into the marketplace. So now’s the time, according to Money Boffins Inc, to buy shares in lithium and other battery minerals (I’ve never bought a share in my life). This lithium mining boom has been quite sudden and surprising to many pundits. In January of this year, only one WA mine was producing lithium, but by mid-2018 there will be eight, according to this article. The battery explosion, so to speak, is bringing increased demand for other minerals too, including cobalt, nickel, vanadium and graphite. Australia’s well-positioned to take advantage. Having said that, the amount of lithium we’re talking about is a tiny fraction of what WA exports in iron ore annually, but it’s already proving to be a big boost to the WA economy, and a big provider of jobs.

battery recycling

Of course all of this also poses a problem, as mentioned in my last post, and it’s a problem that the renewable energy sector should be at least ideologically driven to deal with: waste and recycling. Considering the increasing importance of battery technology in our world, and considering the many toxic components of modern batteries, such as nickel, lead acid, cadmium and mercury, it’s yet another disappointment that there’s no national recycling scheme for non-rechargeable batteries. Currently only lead acid batteries can be recycled, and the rest usually end up in landfill or are sent to be recycled overseas. So it’s been left to the industry to develop an Australian Battery Recycling Initiative (ABRI), which has an interesting website where you can learn about global recycling and many other things batterial – including, of course, how to recycle your batteries. Also, an organisation called Clean Up Australia has a useful battery recycling factsheet, which, for my own educational purposes I’m going to recycle here, at least partly. Battery types can be divided into primary, or single-use, and secondary, or rechargeable. The primary batteries generally use zinc and manganese in converting chemical to electrical energy. Rechargeable batteries use a variety of materials, including nickel cadmium, nickel metal hydride and of course lithium ion chemistry. Batteries in general are the most hazardous of waste materials, but there are also environmental impacts from battery production (mining mostly) and distribution (transport and packaging). As mentioned, Australian batteries are sent overseas for recycling – ABRI and other groups are trying to set up local recycling facilities. Currently a whopping 97% of these totally recyclable battery units end up in landfill, and – another depressing factoid – Australia’s e-waste is growing at 3 times the rate of general household waste. So the public is advised to use rechargeable batteries wherever possible, and to take their spent batteries to a proper recycling service (a list is given on the fact sheet). The ABRI website provides a more comprehensive list of drop-of services.

2015 registrations: Australia’s bar would be barely visible on this chart

EVs in Australia – a very long way to go

I recently gave a very brief overview of the depressing electric vehicle situation in Australia. Thinking of buying one? Good luck with that. However, almost all motorists are much richer than I am, so there’s hope for them. They’re Australia’s early adopters of course, so they need all the encouragement we can give them. Journalist Timna Jacks has written an article for the Sydney Morning Herald recently, trying to explain why electric vehicles have hit a dead end in Australia. High import duties, a luxury car tax and a lack of subsidies and infrastructure for electric vehicles aren’t exactly helping the situation. The world’s most popular electric car, the Nissan Leaf, is much more expensive here than in Europe or the US. And so on. So it’s hardly surprising that only 0.1% of all cars sold in Australia in 2015 were electric cars (compared with 23% and rising in EV heaven, aka Norway, 1.4% in France and 0.7% in the US). Of course Australia’s landscape’s more or less the opposite of compact, dense and highly urbanised Europe, and range anxiety might be a perennial excuse here. We have such a long way to go. I expect we’ll have to wait until shame at being the world’s laughing-stock is enough of a motivation.

Adelaide’s Tindo

I’ve been vaguely aware of Adelaide’s ‘green bus’ for some years but, mea culpa, haven’t informed myself in any depth up until now. The bus is called Tindo, which is a Kaurna aboriginal word meaning the sun. Apparently it’s the world’s first and only completely solar powered electric bus, which is quite amazing. The bus has no solar panels itself, but is charged from the solar panels at the Franklin Street bus station in the city centre. It’s been running for over four years now and I’m planning to take a trip on it in the very near future. I was going to say that it’ll be the first time I’ve been on a completely electric vehicle with no internal combustion engine but I was forgetting that I take tram trips almost every day. Silly me. Still, to take a trip on a bus with no noisy engine and no exhaust fumes will be a bit of a thrill for me. Presumably there will be no gear system either, and of course it’ll have regenerative braking – I’m still getting my head around this stuff – so the ride will be much less jerky than usual.

So here are some of the ‘specs’ I’ve learned about Tindo. It has a range of over 200 kilometres (and presumably this is assisted by the fact that its route is fixed and totally urban, so the regen braking system will be charging it up regularly). It uses 11 Swiss-made Zebra battery modules which are based on sodium nickel chloride, a type of molten salt technology. They have higher energy density, they’re lightweight and virtually maintenance free. According to the City of Adelaide website the solar PV system on the roof of the bus station is (or was – the website is annoyingly undated) ‘Adelaide’s largest grid-connected system, generating almost 70,000 kWh of electricity a year’. No connection to the ‘carbon-intensive South Australian electricity grid’ is another plus, though to be fair our grid is far less carbon intensive than Victoria’s which is almost all brown coal. South Australia’s grid runs on around half gas and half renewables, mostly wind. The regen braking, I must remind myself, means that when decelerating the bus uses no energy at all, and the motor electronically converts into an electrical generator, which generates electricity with the continued forward motion of the bus. There are many more specs and other bits of info on this Tindo factsheet.

the tides – a massive potential resource?

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A floating tidal turbine, Orkney islands, as seen on Fully Charged

A recent episode of Fully Charged, the Brit video series on the sources and harnessing of clean energy, took us again to the very windy Orkney Isles at the top of Scotland to have a look at some experimental work being done on generating energy from tidal forces. When you think of it, it seems a no-brainer to harness the energy of the tides. They’re regular, predictable, unceasing, and in some places surely very powerful. Yet I’ve never heard of them being used on an industrial scale.

Of course, I’m still new to this business, so the learning curve continues steep. Tide mills have been used historically here and there, possibly even since Roman times, and tidal barrages have been operating since the sixties, the first and for a long time the largest being the La Rance plant, off the coast of Brittany, generating 240 MW. A slightly bigger one has recently been built in Korea (254 MW).

But tidal barrages – not what they’re testing in the Orkneys – come with serious environmental impact issues. They’re about building a barrage across a bay or estuary with a decent tidal flow. The barrage acts as a kind of adjustable dam, with sluice gates that open and close, and additional pumping when necessary. Turbines generate energy from pressure and height differentials, as in a hydro-electric dam. Research on the environmental impact of these constructions, which can often be major civil engineering projects, has revealed mixed results. Short-term impacts are often devastating, but over time one type of diversity has been replaced by another.

Anyway, what’s happening in the Orkneys is something entirely different. The islanders, the Scottish government and the EU are collaborating through an organisation called EMEC, the European Marine Energy Centre, to test tidal power in the region. They appear to be inviting innovators and technicians to test their projects there. A company called ScotRenewables, for example, has developed low-maintenance floating tidal turbines with retractable legs, one of which is currently being tested in the offshore waters. They’re designed to turn with the ebb and flood tides to maximise their power generation. It’s a 2 MW system, which of course could be duplicated many times over in the fashion of wind turbines, to generate hundreds if not thousands of megawatts. The beauty of the system is its reliability – as the tidal flow can be reliably predicted at least eighteen years into the future, according to the ScotRenewables CEO. This should provide a sense of stability and confidence to downstream suppliers. Also, floating turbines could easily be removed if they’re causing damage, or if they require maintenance. Clearly, the effect on the tidal system would be minimal compared to an estuarine barrage, though there are obvious dangers to marine life getting too close to turbines. The testing of these turbines is coming to an end and they’ve been highly successful so far, though they already have an improved turbine design in the wings, which can be maintained either in situ or in dock. The design can also be scaled down, or up, to suit various sites and conditions.

rotors are on retractable legs, to protect from storms, etc

Other quite different turbine types are being tested in the region, with a lot of government and public support, but I got the slight impression that commercial support for this kind of technology is somewhat lacking. In the Fully Charged video on this subject (to which I owe most of this info), Robert Llewelyn asked the EMEC marketing manager whether she thought tidal or wave energy had the greatest future potential (she opted for wave). My ears pricked up, as wave energy is another newie for me. Duh. Another post, I suppose.

As mentioned though in this video, a lot of the developments in this tidal technology have come from shipbuilding technology, from offshore oil and gas technology, and from maritime technology more generally, as well as modern wind turbine technology, further impressing on me that skills are transferable and that the cheap clean energy revolution won’t be the economic/employment disaster that the fossil fuel dinosaurs predict. It’s a great time for innovation, insight and foresight, and I can only hope that more government and business people in Australia, where I seem to be stuck, can get on board.

fixed underwater tidal turbine being tested off the Orkney Islands

Written by stewart henderson

October 11, 2017 at 6:27 am

On electrickery, part 1 – the discovery of electrons

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Canto: This could be the first of a thousand-odd parts, because speaking for myself it will take me several lifetimes to get my head around this stuff, which is as basic as can be. Matter and charge and why is it so and all that.

Jacinta: so let’s start at random and go in any direction we like.

Canto: Great plan. Do you know what a cathode ray is?

Jacinta: No. I’ve heard of cathodes and anodes, which are positive and negative terminals of batteries and such, but I can’t recall which is which.

Canto: Don’t panic, Positive is Anode, Negative ICathode. Though I’ve read somewhere that the reverse can sometimes be true. The essential thing is they’re polar opposites.

Jacinta: Good, so a cathode ray is some kind of negative ray? Of electrons?

Canto: A cathode ray is defined as a beam of electrons emitted from the cathode of a high-vacuum tube.

Jacinta: That’s a pretty shitty definition, why would a tube, vacuum or otherwise, have a cathode in it? And what kind of tube? Rubber, plastic, cardboard?

Canto: Well let’s not get too picky. I’m talking about a cathode ray tube. It’s a sealed tube, obviously, made of glass, and evacuated as far as possible. Sciencey types have been playing around with vacuums since the mid seventeenth century – basically since the vacuum pump was invented in 1654, and electrical experiments in the nineteenth century, with vacuum tubes fitted with cathodes and anodes, led to the discovery of the electron by J J Thomson in 1897.

Jacinta: So what do you mean by a beam of electrons and how is it emitted, and can you give more detail on the cathode, and is there an anode involved? Are there such things as anode rays?

Canto: I’ll get there. Early experiments found that electrostatic sparks travelled further through a near vacuum than through normal air, which raised the question of whether you could get a ‘charge’, or a current, to travel between two relatively distant points in an airless tube. That’s to say, between a cathode and an anode, or two electrodes of opposite polarity. The cathode is of a conducting material such as copper, and yes there’s an anode at the other end – I’m talking about the early forms, because in modern times it starts to get very complicated. Faraday in the 1830s noted a light arc could be created between the two electrodes, and later Heinrich Geissler, who invented a better vacuum, was able to get the whole tube to glow – an early form of ‘neon light’. They used an induction coil, an early form of transformer, to create high voltages. They’re still used in ignition systems today, as part of the infernal combustion engine

Jacinta: So do you want to explain what a transformer is in more detail? I’ve certainly heard of them. They ‘create high voltages’ you say. Qu’est-ce que ça veux dire?

Canto: Do you want me to explain an induction coil, a transformer, or both?

Jacinta: Well, since we’re talking about the 19th century, explain an induction coil.

Canto: Search for it on google images. It consists of a magnetic iron core, round which are wound two coils of insulated copper, a primary and secondary winding. The primary is of coarse wire, wound round a few times. The secondary is of much finer wire, wound many many more times. Now as I’ve said, it’s basically a transformer, and I don’t know what a transformer is, but I’m hoping to find out soon. Its purpose is to ‘produce high-voltage pulses from a low-voltage direct current (DC) supply’, according to Wikipedia.

Jacinta: All of this’ll come clear in the end, right?

Canto: I’m hoping so. When a current – presumably from that low-volage DC supply – is passed through the primary, a magnetic field is created.

Jacinta: Ahh, electromagnetism…

Canto: And since the secondary shares the core, the magnetic field is also shared. Here’s how Wikipedia describes it, and I think we’ll need to do further reading or video-watching to get it clear in our heads:

The primary behaves as an inductor, storing energy in the associated magnetic field. When the primary current is suddenly interrupted, the magnetic field rapidly collapses. This causes a high voltage pulse to be developed across the secondary terminals through electromagnetic induction. Because of the large number of turns in the secondary coil, the secondary voltage pulse is typically many thousands of volts. This voltage is often sufficient to cause an electric spark, to jump across an air gap (G) separating the secondary’s output terminals. For this reason, induction coils were called spark coils.

Jacinta: Okay, so much for an induction coil, to which we shall no doubt return, as well as to inductors and electromagnetic radiation. Let’s go back to the cathode ray tube and the discovery of the electron.

Canto: No, I need to continue this, as I’m hoping it’ll help us when we come to explaining transformers. Maybe. A key component of the induction coil was/is the interruptor. To have the coil functioning continuously, you have to repeatedly connect and disconnect the DC current. So a magnetically activated device called an interruptor or a break is mounted beside the iron core. It has an armature mechanism which is attracted by the increasing magnetic field created by the DC current. It moves towards the core, disconnecting the current, the magnetic field collapses, creating a spark, and the armature springs back to its original position. The current is reconnected and the process is repeated, cycling through many times per second.

A Crookes tube showing green fluorescence. The shadow of the metal cross on the glass showed that electrons travelled in straight lines

Jacinta: Right so now I’ll take us back to the cathode ray tube, starting with the Crookes tube, developed around 1870. When we’re talking about cathode rays, they’re just electron beams. But they certainly didn’t know that in the 1870s. The Crookes tube, simply a partially evacuated glass tube with cathode and anode at either end, was what Rontgen used to discover X-rays.

Canto: What are X-rays?

Jacinta: Electromagnetic radiation within a specific range of wavelengths. So the Crookes tube was an instrument for exploring the properties of these cathode rays. They applied a high DC voltage to the tube, via an induction coil, which ionised the small amount of air left in the tube – that’s to say it accelerated the motions of the small number of ions and free electrons, creating greater ionisation.

x-rays and the electromagnetic spectrum, taken from an article on the Chandra X-ray observatory

Canto: A rapid multiplication effect called a Townsend discharge.

Jacinta: An effect which can be analysed mathematically. The first ionisation event produces an ion pair, accelerating the positive ion towards the cathode and the freed electron toward the anode. Given a sufficiently strong electric field, the electron will have enough energy to free another electron in the next collision. The  two freed electrons will in turn free electrons, and so on, with the collisions and freed electrons growing exponentially, though the growth has a limit, called the Raether limit. But all of that was worked out much later. In the days of Crookes tubes, atoms were the smallest particles known, though they really only hypothesised, particularly through the work of the chemist John Dalton in the early nineteenth century. And of course they were thought to be indivisible, as the name implies.

Canto: We had no way of ‘seeing’ atoms in those days, and cathode rays themselves were invisible. What experimenters saw was a fluorescence, because many of the highly energised electrons, though aiming for the anode, would fly past, strike the back of the glass tube, where they excited orbital electrons to glow at higher energies. Experimenters were able to enhance this fluorescence through, for example, painting the inside walls of the tube with zinc sulphide.

Jacinta: So the point is, though electrical experiments had been carried out since the days of Benjamin Franklin in the mid-eighteenth century, and before, nobody knew how an electric current was transmitted. Without going into much detail, some thought they were carried by particles (like radiant atoms), others thought they were waves. J J Thomson, an outstanding theoretical and mathematical physicist, who had already done significant work on the particulate nature of matter, turned his attention to cathode rays and found that their velocity indicated a much lighter ‘element’ than the lightest element known, hydrogen. He also found that their velocity was uniform with respect to the current applied to them, regardless of the (atomic) nature of the gas being ionised. His experiments suggested that these ‘corpuscles’, as they were initially called, were 1000 times lighter than  hydrogen atoms. His work was clearly very important in the development of atomic theory – which in large measure he initiated – and he developed his own ‘plum pudding’ theory of atomic structure.

Canto: So that was all very interesting – next time we’ll have a look at electricity from another angle, shall we?

 

Written by stewart henderson

October 1, 2017 at 8:14 pm

what are capacitors?

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the shapes and sizes of capacitors – a screenshot taken from the youtube vid – What are Capacitors? – Electronics Basics 11

Jacinta: We’re embarking on the clearly impossible task of learning about every aspect of clean (and sometimes dirty because nothing’s 100% clean or efficient) technology – batteries, photovoltaics, turbines, kilo/megawatt-hours, glass electrolytes, powerwalls, inverters, regen, generators, airfoils, planetary gear sets, step-up transformers, nacelles AND capacitors.

Canto; Enough to last us a lifetime at our slow pace. So what, in the name of green fundamentalism, is a capacitor?

Jacinta: Well I’ve checked this out with Madam Youtube…

Canto: Professor Google’s co-dependent…

Jacinta: And in one sense it’s simple, or at least it sounds simple. Capacitors store electric charge, and the capacitance of a capacitor relates to how much charge it can hold.

Canto: So how does it do that, and what’s the purpose of storing electric charge?

Jacinta: Okay now you’re complicating matters, but basic to all capacitors are two separated pieces of conducting material, usually metal. Connected to a battery, they store charge…

Canto: Which is a kind of potential energy, right?

Jacinta: Umm, I think so. So take your battery with its positive and negative terminals. Attach one of the bits of conducting material (metal) to the positive terminal and you’ll get a flow of negatively-charged electrons to that terminal, because of ye olde law of attraction. This somehow means that electrons are repelled from the negative terminal  (which we’ve hooked up to the other bit of metal in the capacitor). So because the first strip of metal has lost electrons it has become positively charged, and the other bit of metal, having gained electrons, has an equal and opposite charge. So each piece of metal has the same magnitude of charge, measured in coulombs. This is regardless of the size and shape of the different metal bits.

Canto: But this process reaches a limit, though, yes? A kind of saturation point…

Jacinta: Well there comes a point where, yes, the accumulated charge just sits there. This is because there comes a kind of point of equilibrium between the positive battery terminal and the now positively charged strip of metal. The electrons are now caught between the attractive positive terminal and the positive strip.

Canto: Torn between two lovers, I know that foolish feeling.

Jacinta: So now if you remove the battery, so breaking the circuit, that accumulated charge will continue to sit there, because there’s nowhere to go.

Canto: And of course that accumulated or stored charge, or capacitance, is different for different capacitors.

Jacinta: And here’s where it gets really complicated, like you know, maths and formulae and equations. C = Q/V, capacitance equals the charge stored by the capacitor over the voltage across the capacitor. That charge (Q), in coulombs, is measured on one side of the capacitor, because the charges actually cancel each other out if you measure both sides, making a net charge of zero. So far, so uncomplicated, but try and get the following. When a capacitor stores charge it will create a voltage, which is essentially a difference in electric potential between the two metal strips. Now apparently (and you’ll have to take my word for this) electric potential is high near positive charges and low near negative charges. So if you bring these two differently charged strips into close proximity, that’s when you get a difference in electric potential – a voltage. If you allow a battery to fully charge up a capacitor, then the voltage across it (between the two strips) will be the same as the voltage in the battery. The capacitance, Q/V, coulombs per volt, is measured in farads, after Micky Faraday, the 19th century electrical wizz. I’m quoting this more or less verbatim from the Khan Academy video on capacitors, and I’m almost finished, but here comes the toughest bit, maths! Say you have a capacitor with a capacitance of 3 farads, and it’s connected to a nine volt battery, the charge stored will be 27 coulombs (3 = 27/9). 3 farads equals 27 coulombs of charge divided by nine volts, or 27 coulombs of charge is 3 farads times 9 volts. Or, if a 2 farad capacitor stores a charge of 6 coulombs, then the voltage across the capacitor will be 3 volts.

Canto: Actually, that’s not so difficult to follow, the maths is the easiest part for me… it’s more the concepts that get me, the very fact that matter has these electrical properties…

Jacinta: Okay here’s the last point made, more or less verbatim, on the Khan Academy video, something worth pondering:

You might think that as more charge gets stored on a capacitor, the capacitance must go up, but the value of the capacitance stays the same because as the charge increases, the voltage across that capacitor increases, which causes the ratio to stay the same. The only way to change the capacitance of a capacitor is to alter the physical characteristics of that capacitor (like making the pieces of metal bigger, or changing the distance between them).

Canto: Okay so to give an example, a capacitor might be connected to an 8 volt battery, but its capacitance is, say, 3 farads. It will be fully charged at 24 coulombs over 8 volts. The charge increases with the voltage, which has a maximum of 8. The ratio remains the same. Yet somehow I still don’t get it. So I’m going to have a look at another video to see if it helps. It uses the example of two metal plates. They start out as electrically neutral. You can’t force extra negativity, in the form of electrons, into one of these plates, because like charges repel, and they’ll be forced out again. But, according to the video, if you place another plate near the first, ‘as electrons accumulate in the first metal plate, they will repel the electrons in the second metal plate’, to which I want to respond, ‘but electrons aren’t accumulating, they’re being repelled’. But let’s just go with the electron flow. So the second metal plate becomes depleted of electrons and is positively charged. This means that it will attract the negatively charged first metal plate. According to the video, this makes it possible for the first plate to have more negative than positive particles, which I think has something to do with the fact that the electrons can’t jump from the first plate to the second, to create an equilibrium.

Jacinta: They’re kind of attracted by absence. That’s what they must mean by electric potential. It’s very romantic, really. But what you’ve failed to notice, is that a force is being continually applied, to counteract the repulsion of electrons from the first plate. If the force no longer applies then, yes, you won’t get that net negative charge in the first plate, and the consequent equal and opposite charge in the second. My question, though, is how can the capacitance increase by bringing the plates closer together? I can see how it can be changed by the size of the conducting material – more electrons, more electric potential. I suppose reducing the distance will increase the repulsive force…

Canto: Yes, let’s assume so. Any, a capacitor, which stores far less charge than a similarly-dimensioned battery can be used, I think, to briefly maintain power to, say, a LED bulb when it is disconnected from the battery. The capacitor, connected to the bulb will discharge its energy ‘across’ the bulb until it achieves equilibrium, which happens quite quickly, and the bulb will fade out. If the capacitor is connected to a number of batteries to achieve a higher voltage, the fully charged capacitor will take longer to discharge, keeping the light on for longer. If the metal plates are larger, the capacitor will take longer to charge up, and longer to discharge across the LED bulb. Finally, our second video (from a series of physics videos made by Eugene Khutoryansky) shows that you can place a piece of ‘special material’ between the two plates. This material contains molecules that change their orientation according to the charges on the plates. They exert a force which attracts more electrons to the negative plate, and repel them from the positive plate, which has the same effect as increasing the area of the plates – more charge for the same applied voltage.

Jacinta: An increase in capacitance.

Canto: Yes, and as you’ve surmised, bringing the two plates closer together increases the capacitance by attracting more electrons to the negatively charged plate and repelling them from the positively charged one – again, more charge for the same voltage.

Jacinta: So you can increase capacitance with a combo of the three – increased size, closer proximity, and that ‘special material’. Now, one advantage of capacitors over batteries is that they can charge up and discharge very quickly. Another is that they can endure many charge-discharge cycles. However they’re much less energy dense than batteries, and can only store a fraction of the energy of a same-sized battery. So the two energy sources have different uses.

Canto: Mmmm, and we’ll devote the next post to the uses to which capacitors can be put in electronics, and EVs and such.

 

Written by stewart henderson

August 28, 2017 at 6:27 pm