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12:15 AM
@GlenH7 @TrevorArchibald thanks
 
 
3 hours later…
3:31 AM
Hi
 
Hey :)
This will be far more efficient than doing over the comments
 
@ashgetstazered @ashgetstazered good to see you here. Yup, should be easier than comments.
 
@EnergyNumbers Ah that's a clever way to keep track of conversations in a chat room
 
Happy to work with a UK example? Bahrain is fun too, but UK is hard enough according to David, so we can start there.
 
UK sounds good (especially considering it's his case study as well
 
3:35 AM
@ashgetstazered ok. UK land surface area is ~240 Gm2 (240 billion square metres, 240 thousand square km)
UK sea area (EEZ) is about three times that.
 
UK final energy demand is about 170 GW - taking this from DUKES 2015 (Digest of UK Energy Statistics)
NB this is one of the bits that David gets wrong (he puts it at ~180 KWh/p/d, which is ~450 GW.
I wrote a bit about this here: energynumbers.info/…
 
I'm skimming through the DUKES energy demand - are they talking about just electricity or all forms of energy? (i.e. transport, embodied energy in products used etc.?)
 
@ashgetstazered All forms of energy actually demanded in the UK. So electricity heating transport. It includes embedded energy on exported goods, but excludes embedded energy on imported goods.
 
Ahk. Wow he was way off... that's almost a factor of 3
 
3:40 AM
(We couldn't really generate the energy on imported goods anyway, because, well, they're imported. We couldn't generate electricity and ship it to to China)
 
Yep. Alright. So we've got 240k km^2 and need to supply 170GW
 
@ashgetstazered I get UK final energy demand from DUKES p14: primary demand is 201.4 mtoe, of which final energy demand is 67% and transmission and distribution losses are 1.5%
 
so in Dave's terms thats ~0.7W/m^2
 
@ashgetstazered So that's about one tenth of PV output according to David: so 10% of the UK with PV panels would do it on an annual average (but not on a seasonal average)
@ashgetstazered And as the UK has great offshore wind, it would be silly to ignore that, particularly as it generates more in winter, when more energy is consumed.
@ashgetstazered So in that case we've got ~1 million sq.km for 170 GW: so 8.5% of that at 2W per metre squared would do it. - that's 8.5% of land and 8.5% of seas spanned by wind.
(NB not USED by wind, just spanned by it - actual land use is a small fraction of that)
 
@EnergyNumbers: wait 10% of 240 thousand ~ 24000?
Where is ~1 million sq.km coming from?
@EnergyNumbers: Oh wait you're saying that's the total amount available. With you. Ignore my stupidity
 
3:48 AM
@ashgetstazered No worries - 1 million sq km for land + EEZ. So not LAND area, but surface area of UK land and seas.
And, of course, we can double things up: we can take an existing sheep farm, add PV and add wind, and get three times the use of the land, and we get 2W/m2 for the wind, and something between 5 and 10W/m2 for the PV.
 
@EnergyNumbers: Right!
So David's work is flawed because his assumptions to do with energy demand are way too high
@EnergyNumbers: While his numbers on the actual generation capacity is still sound?
 
@ashgetstazered Several reasons. That's one.
 
*are still sound
 
@ashgetstazered Sometimes. He often ignores sea surface area when considering total resource available, which is a bit odd given offshore wind, and possibilities in wave and tidal.
(UK offshore wind resource in particularly is extremely huge - I wrote a bit about it here: energynumbers.info/the-uk-is-the-saudi-arabia-of-wind-energy
 
This is brilliant!
 
3:51 AM
But for somewhere like Japan, offshore wind is interesting too, if we can crack floating offshore wind.
 
Both in maths/learning + general news for the world's energy future.
 
@ashgetstazered His numbers on resource per unit land area are ... mixed.
 
Are their oceans too deep?
 
@ashgetstazered Yeah, like many coasts, Japan's seabed drops down like a cliff, because it's at the edge of a continental plate.
(see also Norway)
 
@EnergyNumbers: Just looked up a map of tectonic plates. Norway isn't near an edge?
Are continental and tectonic plates different?
 
3:55 AM
The North Sea is a bit of a freak as seas go: it used to be land that got flooded a few thousand years ago, so we've got absolutely vast tracts of shallow seas. There's a lake in the UK, Wast water, that's deeper (at its deepest point) than much of the North Sea.
@ashgetstazered Ooh, isn't it? I assumed it was, as the seabed off the North coast drops off really sharply. Sorry, my mistake. Yeah, thinking about it, there's no volcanic activity up there that I've heard of.
 
How interesting. What's the maximum depth that a fixed offshore wind farm can be built on?
 
@ashgetstazered good question. We don't know yet. 48m is still the deepest we've gone, because there's so much resource shallower than that. I think we expect to go deeper over the next 5 years: which foundation is optimal, is an open question at those depths.
 
@EnergyNumbers: I'm just going off the first few google images results hits for 'continental plates' so it's in no way definitive. Haha
 
@ashgetstazered resource per sq.m is tricky: currently, because surface area is not a constaint, no one designs a power station to optimise it.
 
Right. What are the problems currently faced with floating farms? Do they topple over?
 
3:59 AM
@ashgetstazered I think you're right.
@ashgetstazered It's just very early days - only a handful of full-scale prototypes have been put in the water. Partly because there's no economic imperative for it, with the possible exception of Japan. And because we're still doing so much learning by doing, simply for shallow offshore wind on fixed foundation.
 
@EnergyNumbers: With the North Sea wind resource - is there not a potential problem in having too much wind?
 
@ashgetstazered how do you mean? Having to curtail it because speeds are too high, or because total instantaneous generation would be too high?
 
@EnergyNumbers curtail it because the speeds are too high/will damage the turbine
 
@ashgetstazered That might be a problem in the Atlantic - particularly in hurricane territory. Not in the North Sea or Irish Sea - we've got quite a lot of fixed-foundation offshore wind out there already that does fine in the highest winds they get - they just get switched off, and the blades feathered into the wind, at wind speeds over 25m/s
 
@EnergyNumbers sorry that's what I meant - how localised are those high wind speeds? Is it possible that most/all of the offshore wind would have to be shut down simultaneously?
 
4:05 AM
In the Caribbean, there is at least one onshore wind turbine that's hinged at its base, that has to be folded down to the ground when hurricanes come. So they'd probably not be able to do much offshore wind there.
 
@EnergyNumbers for a UK example. Obviously I'm not talking about the entire world.
 
@ashgetstazered It would get shut down progressively, as the weather front moved across the seas: it typically takes 24-48 hours for a weather front to move across the UK
But if we put 9GW of wind capacity on Dogger Bank, as has been suggested, then that could go from max to zero in a few hours. I think the current plan is to build 1-2GW on Dogger, so not so much an issue.
Slew rates for high wind penetration are an interesting open question. Some people get anxious about the five-day lull, but that's easy to deal with. Steep slew rates will be a properly interesting challenge.
(slew rate = rate of change of power)
 
@EnergyNumbers So while the shut down would be progressive there could be potential for all of the offshore wind to be shutdown at the same time?
@EnergyNumbers that's actually what my research is about. But on a much smaller scale.
@EnergyNumbers smart-grid energy variability with high penetration of renewables etc. etc.
 
@ashgetstazered All in the North Sea, say. I haven't yet got the half-hourly generation figures for each UK offshore wind farm. I should get those over the next month.
 
@EnergyNumbers How common are five day lulls?
 
4:11 AM
@ashgetstazered Here's a model I made for looking at storage options with a high penetration of renewables: energynumbers.info/balancing
 
@EnergyNumbers you're obviously really knowledgeable about this! Is this what you do for work or is this an intense side-interest?
 
@ashgetstazered maybe one or two a year. Funnily enough, the 30-day lull is a bigger problem if we consider wind only, but only happens in heatwaves, so as long as there's PV, it's an easier problem.
@ashgetstazered It's my living - I've been in the low-carbon sector for ~23 years.
@ashgetstazered And that's very kind of you to say so, thank you.
@ashgetstazered We've got a PhD student looking at the behavioural economics of smart grid demand-side response - is that something of interest to you, or are you at the technology end of things?
 
@EnergyNumbers with your model with a 60% wind & 40% solar split there is still 20% of demand that can't be met. even with 100GWh storage with 50GW in/out? What events are causing that?
Is there a 5 day/ 30 day lull in the data that the model is operating on?
@EnergyNumbers 23 years! Behavioural Economics? Is that to do with financial cost vs. change-in-comfort-level?
@EnergyNumbers I'm more looking at a control system to manage the variability/errors in forecasting.
 
@ashgetstazered It's about 5 years of generation. Yeah, for a wind/PV-only system, storage needs to be in the many-TWh range. As it happens, Europe already has clean storage in the range of ~100 TWh, in the form of (non-pumped) storage hydro.
@ashgetstazered Yeah, that sort of thing, as well as what sort of incentives do and don't work.
@ashgetstazered Ah, very interesting. I know Pierre Pinson's done a lot of work on examining what that gap is between forecasting and actual generation. And I think Mark o'Malley and others have looked at that too. What sort of controls are you looking at? Are you designing electronics, or control protocols, or machine-learning algos?
 
@EnergyNumbers Ahhh. My intuition was ~an order of magnitude out. Obviously need to read more! Haha
 
4:21 AM
@ashgetstazered That gap is just as likely to be a seasonal effect (low-ish output for two months) as a five-day lull. It's the subtle, slow weather systems that make for the interesting problems.
 
@EnergyNumbers Thanks for the names! It's still very early days but it's going to be to do with control protocols
@EnergyNumbers I'm trying to stay away from power quality management/that side of things
@EnergyNumbers as well as the really nitty-gritty algorithm development
 
@ashgetstazered Fair enough. It's a big field, and a PhD has to be focussed.
 
@EnergyNumbers for hydro-poor countries would biomass be a dispatcheable 'renewable' that could fill that gap?
 
Quebec Hydro have been doing trials to use wind turbines themselves, moderating their output, to manage high slew rates.
 
@EnergyNumbers how strong does a countries agriculture sector need to allow for a 'significant' biomass production sector?
 
4:24 AM
@ashgetstazered Biomass; or synthetic methane or hydrogen.
 
*need to be to allow for
 
@ashgetstazered Good question: if we're talking about just managing slew rates, then not much. Filling energy gaps, then a lot more. If a country has a coastal forest, then shipping biomass around the world is relatively cheap (in environmental and financial terms). Of course, we're then dependent on those forests being managed sustainably.
 
*country's
 
(ironic note, from a colleague: the coal industry was one of the first to concern itself with the sustainability of forest management)
 
@EnergyNumbers would the UK currently be able to fill energy gaps with biomass? (if it didn't have hydro)
Haha how interesting. I'm currently in Australia and there's a joke that's been circulating about how currently the Coal companies have better environmental policies than our government.
 
4:28 AM
@ashgetstazered I don't know, I'm afraid. Gail Taylor at Southampton, and others, are looking at UK options for biomass.
 
@EnergyNumbers fair fair. It's a pretty abstract question. In your opinion though would the UK be able to move to being 100% renewable generated while maintaining(/achieving?) energy independence?
 
@ashgetstazered It would be achieving, rather than maintaining energy independence. I don't know when the UK last was energy independent, but we now have imports of all the fuels we use: biomass, uranium, oil, gas, coal. The UK could be generation-neutral or have surplus generation easily, because of the massive scale of the offshore wind resource.
 
How interesting.
Thanks for taking the time to explain/share your knowledge. It is much appreciated. I will be reading the Energy Numbers blog!
 
So that's one kind of independence. But it's not energy autarky: interconnectors make high renewables penetrations SO much easier (ref Gregor Czisch's thesis of the early noughties, and lots of work by Gregor Giebel, Mark Barrett, and many others)
 
I've got to run to a meeting unfortunately.
I hope you have a lovely day!
 
4:32 AM
@ashgetstazered I don't write very often. Good chatting to you. Bye
 
 
13 hours later…
5:47 PM
It all comes down to power density: youtube.com/watch?v=E0W1ZZYIV8o
 
Hard to think of Power Density without Xkcd's take on logarithmic scales. That said, yes, there's the whole issue with night time and overcast weather.
 
@ashgetstazered funnily enough, surface area power density is pretty much irrelevant for just about every country in the world; for those places such as Monaco or the Vatican where it is a real constraint, they're not energy-independent now, and probably expect never to be.
 
SF.
@EnergyNumbers: I wouldn't be entirely sure about that. While the surface area of the solar power plants (concentrated or PV) is rather reasonable, hydroelectric require lakes of many kilometers square and these arouse many protests as people need to be resettled and ecosystems disrupted.
 
@SF. sure, there are always trade-offs (no silver bullets); my point is that at the national level, surface area is only a significant constraint on renewables penetration for a handful of peculiar corner cases.
 
@EnergyNumbers: That is wrong. Watch the linked TED talk. The UK would need to cover half it's land area to get anywhere near energy-independence with solar. I'd say that realistically means they're constrained.
 
5:47 PM
@ashgetstazered I did. Then I checked the real numbers. It turns out it's not a constraint at all. Wind spanning 10% of UK land and waters would be more energy per year than the entire UK uses. Even less is needed if combined with solar, biomass, wave, tidal and/or geothermal. Science is bigger and smarter than TED talks.
 
@EnergyNumbers While I agree TED talks are not the be all and end all. The guy giving the presentation (David MacKay) is the head engineering Professor at Cambridge(!). Not only that but he was also the Chief Scientific Adviser to the UK's department of energy. So I'd say he knows what he's doing. I think you're getting caught up with the maximum outputs and not taking into account variable/sub-max real-world outputs. He runs the real numbers using yearly outputs of various renewable plants. more info: withouthotair.blogspot.com.au/2013/11/…
@EnergyNumbers: if you're not keen on blogs either you can read his book (which has over a thousand citations on google scholar). He's kindly hosted for free: withouthotair.com/Contents.html Did I also mention he has over 43k+ citations on Google Scholar? H-index of 61?! So yes. I'd say his TED talk was pretty reliable.
 
@ashgetstazered I've read it: David's wrong about quite a few things. So put aside your appeal to authority, and do the maths yourself: think like an engineer, not an acolyte.
 
@EnergyNumbers: Fair enough. Do you have these calculations anywhere? Or available sources for the solar/renewable plant outputs that so vastly contradict his? The maths itself isn't complex, I've mostly found finding real-world data to be the problem. I'm asking genuinely. Very curious :)
 
@ashgetstazered happy to work through a calc in chat with you
 
Air
12 messages moved from Discussion on question by Stephen Collings: What are the disadvantages of concentrated solar thermal power? Moved comments start here and the continued conversation starts here (because of chat silliness).
 
Air
6:02 PM
Sorry for the ordering issue with the moved messages; I was expecting/hoping they would retain the timestamps of the comments, and get moved appropriately above the chat stuff.
In MacKay's defense, he does say he's doing back-of-the-envelope calcs and that they can be expected to be inaccurate, and he's delivering a message to a lay audience about limitations - a valuable message.
Oh, hah, I just saw the comments on your blog. Don't want to rehash that conversation. :)
I always love to see renewables come up as a subject for Q&A and chat - wish I had more time to engage in detail at the moment, but I've gotten quite busy. Cheers.
> That means, if you do want renewables to make a substantial difference for a country like the United Kingdom, on the scale of today's consumption, you need to be imaging renewable facilities that are country-sized – not the entire country but a fraction of the country, a substantial fraction.
^ I take that as the Big Point of the talk - so far. (Hard to listen to it while working at the same time, so I'm getting it in bits and pieces.)
 

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