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    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 22nd 2017 edited
     
    Heard this on the news on way home from work last night:

    http://www.bbc.co.uk/news/business-39668889

    I have made a chart of the domestic fuel mix from GridWatch (http://www.gridwatch.templar.co.uk/download.php)

    I tripped out the interconnects, Oil generation, OCG, Pumped and Other, as they were either so tiny or not really relevant to domestic generation (who knows what the Dutch are really burning).

    Easy enough to look those figures up if you want to as they are part of the download.

    Now the really interesting thing is the solar production. It can now peak at nuclear levels, though the yield over a day is a lot lower. Due to the high pressure over the UK at the moment we have had pretty clear skies, and wind production is down.

    Gas still makes up the lion's share of our generation, not ideal environmentally and politically, but so much better than coal.

    What did occur to me is that if we can continue down this low carbon route, and there is no reason why we cannot do so for the next decade (there are technical limitations eventually), we may need to rethink our house building from an emissions viewpoint (that DER, TER stuff).

    There is still a good argument to reduce usage because of cost (Gas is about £40/MWh, Nuclear about £95/MWh, Solar and Wind about £150/MWh), but it shows that with a serious reduction in usage the price need not be prohibitive (maybe a 25% rise in overall electricity costs, I would need to look at figures a bit more on that to get a truer picture).

    Now the 'Spot the Coal line' chart.
      GB Grid demand and generation.jpg
    • CommentAuthorEd Davies
    • CommentTimeApr 22nd 2017
     
    Posted By: SteamyTeaNow the really interesting thing is the solar production. It can now peak at nuclear levels, …
    Apparently there's as much “industrial-scale” PV (fields of it, etc) as domestic in the UK now. Just from a chart I saw during idle browsing so not absolutely sure but a bit of a surprise, anyway. That's happened quietly.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 22nd 2017
     
    Posted By: SteamyTeawe may need to rethink our house building from an emissions viewpoint (that DER, TER stuff)
    I can guess what you mean by that ... but spell it out?
    •  
      CommentAuthorfostertom
    • CommentTimeApr 22nd 2017
     
    Posted By: Ed DaviesThat's happened quietly
    and horribly conspicuously esp in renewable-mad Cornwall. Ugliest thing, esp compared to the grace of turbines.

    The Switch estimates that by 2035, with plateauing world energy demand (incl continuing rapidly falling demand in the developed 'west' and China), the world will need (and quite feasibly attain) 0.25% to 0.5% coverage of its land area with PV, to supply the entire demand.

    However in cloudy UK, that would be crudely 16% of its land area, some of it on urbanised roofs/walls, and reduced a bit by wind, tidal, hydro, biomethane etc (limited potential compared to that total demand, even in this most-favoured island and seas) - that's before probable doubling of PV efficiency on the way. Anyway, at continually declining cost, approaching trivial pocket-money (while the costs of the nuclear alternative show no sign of economies of scale etc but continue to increase rapidly with each added complication, safety measure and decommissioning projection).

    However, it's complete madness to put that PV on prime farm land, incentivising its withdrawal from agriculture. Only in a west temporarily hooked on the myth of globalised-everything, air-mileing bulky low value foodstuffs around the planet. That sooner rather later will cave in and UK, let alone Europe will have to return to localised food-self-sufficiency. Trouble is, those PV farms are phemomenally trouble-free, low maintenance, will last 'forever', so they're here for keeps, eating up vital farmland (unlike the turbines)
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 22nd 2017 edited
     
    Posted By: fostertomHowever, it's complete madness to put that PV on prime farm land
    That tends not to happen though. Most of Cornwall is grade 3b and 4 agricultural land. So not prime agricultural land. Crops still pay better than PV to a farmer.
    We can also replace horticultural crops for PV easily. May even help reduce my hayfever.


    Posted By: fostertom
    Posted By: SteamyTeawe may need to rethink our house building from an emissions viewpoint (that DER, TER stuff)
    I can guess what you mean by that ... but spell it out?
    We would need a new metric if we could heat and power our homes on a low carbon basis.
    Inflation linked £/m^2.year could be used, but I am sure there are other suitable examples.
    • CommentAuthortony
    • CommentTimeApr 22nd 2017
     
    What is this news covering up? A big coal fired power station has been converted to burn biomass which is highly polluting, produces CO2 in large quantities, and though called renewable energy the scale of the operation would seem not to be sustainable to me.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 22nd 2017
     
    Posted By: tonyA big coal fired power station has been converted to burn biomass which is highly polluting, produces CO2 in large quantities
    I wondered about this too. And then there was possibly spinning and hot spinning reserves. Not as though you can just stop shoveling fuel and then light it up 20 minutes before you need the power.

    Still a good achievement for the country, albeit on a day with nearly half the winter demand.
  1.  
    Posted By: Ed DaviesApparently there's as much “industrial-scale” PV (fields of it, etc) as domestic in the UK now. Just from a chart I saw during idle browsing so not absolutely sure but a bit of a surprise, anyway. That's happened quietly.


    There are four possibly five commercial arrays within a ten mile radius of where I live. Some have sheep grazing around them. I don't see anything unpleasant about them and prefer them to wind turbines which have the potential for annoyance by noise and flicker in the more built up SE of England.
    • CommentAuthortony
    • CommentTimeApr 22nd 2017
     
    My objection to solar is that it only works part of the day and never at night.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 22nd 2017 edited
     
    and barely in winter - but all of that rapidly becoming no-problem, either to the grid, or to reserving own-generated power till needed whether grid-connected or off-grid.
    • CommentAuthorEd Davies
    • CommentTimeApr 22nd 2017 edited
     
    Only a 2.7:1 ratio summer (April, best month) to winter (December, worst) for 70° inclination south-facing panels in Plymouth.

    Still, until gas is getting seriously curtailed it's not a problem. We'll need a mix for a long time: wind, PV, at least the existing nuclear, storage and a bit of gas.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 22nd 2017
     
    Once serious PV excesses arise, it'll be used large-scale to make hydrogen for Rasas Mirais and buses, and liquid or gas fuels as energy-store for night/winter distributed through the existing distribution network.

    One idea that's crazy at first sight, makes some sense on consideration - pulling significantly beneficial amounts of CO2 out of the atmosphere - but converting the C to liquid fuel as above, releasing O2 - only to burn/re-oxidise the fuel soon enough to the same amount of CO2 as was extracted.
    Crazy?
    Or a carbon-neutral way of smoothing the PV supply, so we can 100% rely on the latter sooner?
    That is, carbon-neutral similar to how biomass burning is allegedly carbon-neutral but isn't really once the accompanying production/distribution carbon costs are figured in.

    What does the team think?
    • CommentAuthortony
    • CommentTimeApr 22nd 2017
     
    Storage is very inefficient, we can never 100% rely on PV it doesn't generate at night etc

    I am all for 100% clean renewable energy reducing use. Then use tidal and an Iceland interconnector for geothermal electricity.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 22nd 2017
     
    Posted By: tonyStorage is very inefficient, we can never 100% rely on PV it doesn't generate at night etc
    What if storage cd be made very efficient on a large scale, principally by eliminating, on burning/re-oxidising/fuel cell etc, any intermediate stage of conversion to mechanical work? That is, the irreducible Carnot inefficiency of spinning turbines/generators.
    • CommentAuthorEd Davies
    • CommentTimeApr 22nd 2017
     
    Posted By: tonyStorage is very inefficient
    Depends on what sort and how it's done.

    we can never 100% rely on PV it doesn't generate at night etc
    Of course not, we need a mix. Wind and PV tend to complement each other quite well - it tends to be more windy when it's less sunny.

    Then use tidal and an Iceland interconnector for geothermal electricity.
    Tidal and Icelandic interconnectors can play a useful niche role but just aren't going to produce anything like enough on their own. Europe needs something in excess of 3000 GW of generation assuming we want to get rid of fossil fuels for all uses, not just electricity.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 22nd 2017
     
    Posted By: tonyStorage is very inefficient, we can never 100% rely on PV it doesn't generate at night etc
    But we can predict that, and the day ahead production pretty well these days.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 22nd 2017
     
    Posted By: fostertomOnce serious PV excesses arise, it'll be used large-scale to make hydrogen for Rasas Mirais and buses, and liquid or gas fuels as energy-store for night/winter distributed through the existing distribution network.
    At an efficiency cost
    https://en.wikipedia.org/wiki/Electrolysis_of_water (as Ed points out).

    Primary energy use in Europe is about 182,24,210,000 MWh/year (1567 Mtoe/year), to do this with 100% reliable electrical generation would require 20,80,389 MW, but this only a mean, to allow for peaks and unusual demand, it could easily be double.
    There are some efficiency gains to be had i.e. heat pumps and electrical vehicles, but grid losses would counteract to a certain extent unless we develop a room temperature superconductor that is cheap.

    Ed, check my sums, here is the source:
    http://www.eea.europa.eu/data-and-maps/indicators/primary-energy-consumption-by-fuel-6/assessment
    •  
      CommentAuthorfostertom
    • CommentTimeApr 22nd 2017 edited
     
    Posted By: Ed Davieswe need a mix. Wind and PV tend to complement each other quite well
    Even in highly favoured UK island/seas, the potential of wind (also tidal/wave etc) is much smaller than the UK PV potential, so these won't be able to help balance the PV forever.
    In addition, PV price will continue to fall dramatically, much faster than the others (shortly overtaking the cheapest wind), so will leave them behind in installed capacity/production.
    Maybe even kill them off, except as an expensive but necessary on/off switchable balancing facility, comparable to ticking-over gas turbines.
    • CommentAuthorEd Davies
    • CommentTimeApr 22nd 2017
     
    Posted By: SteamyTeaPrimary energy use in Europe is about 182,24,210,000 MWh/year (1567 Mtoe/year), to do this with 100% reliable electrical generation would require 20,80,389 MW,
    The commas in those numbers are very confusing. It's too late tonight for me to work forward from tonnes of oil.

    Also, it's really final energy use we need to be working back from.

    I got the 3000 GW from 750 million people with 4 kW each. That's a bit less than currently but not the big negawatts we'd be needing to get down to for the 2000 W society.
    • CommentAuthorCWatters
    • CommentTimeApr 23rd 2017
     
    I'm not sure if much coal is used for spinning reserve. Around here they are quietly adding diesel generators to wind farms. I read somewhere that gas plants can also start fast enough.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 23rd 2017
     
    Posted By: fostertomPV price will continue to fall dramatically
    They can't drop much more, they are almost as cheap as glass, and that is a major component of them.
    Installation costs may come down a bit, but in the UK, other costs get added in i.e. planning, ground rents, grid connection.

    There is also the price per installed MW and the price per MWh generated, these vary a fair bit between technologies.


    Posted By: Ed DaviesThe commas in those numbers are very confusing
    Odd how that happened. I am half blind by bedtime :sad:
    •  
      CommentAuthorfostertom
    • CommentTimeApr 23rd 2017 edited
     
    Posted By: SteamyTeathey are almost as cheap as glass
    The glass is next thing to go, also rigid frames/backing board - thin films coming to market soon. Which need supporting yes e.g. by fritting onto window glass or other surface that's needed anyway.

    And Tesla announced PV integrated into traditional roofing tiles/slates - a new breed without the cost penalty of previous similar efforts - and now sheet-roofing which can be effectively cut and fitted, as is needed in real-world roofing.

    These give a fresh boost to building-fitted PV, which needs to re-catch-up with commercial ground-hogging installations. Every square inch of urban surface needs to be fitted a) because it supports the semi-autonomous 'use your own' sector and b) to cover less of our farmland - which we're going to need again some time soon.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 23rd 2017
     
    I heard the other day that with modern farming (make of that as you will), the UK can feed half a billion people.
    Saying that we need all this land just for agriculture seems to me to be plain wrong.
    Another myth that needs busting.
    A basic calculation using 0.25% efficiency for food crops, 950 kWh/m^2 of solar energy and 70 million people in the country, we should be able to feed them from a land area (purely on a calorific value of 2 kWh/(day.person)) on an area of 6 km^2.

    I am sure someone will come along and show me the error of my ways.
    • CommentAuthorEd Davies
    • CommentTimeApr 23rd 2017
     
    It's meat that takes up a lot of the space, I think. Both for the actual animals and for growing winter feed.

    I make it 21'516 km², still only about a tenth of the area of the island (Great Britain).

    >>> 2 * 70e6 * 365 / (0.25/100) / 950 / 1e6
    21515.78947368421

    I suspect you forgot that you need to feed people every day, not just on their birthdays, then slipped a decimal point somewhere.

    2 kWh/day is also likely a bit low: 100 watts is 2.4 kWh/day and converting US and French recommended intakes [¹] also give around 2.5 kWh/day. Still, with children, for round number arithmetic it's probably fine.

    [¹] https://en.wikipedia.org/wiki/Food_energy
  2.  
    Posted By: Ed DaviesIt's meat that takes up a lot of the space, I think. Both for the actual animals and for growing winter feed.

    Yes modern industrial agricultural tends to use prime agricultural land for meat production mostly because the animals are housed or yarded most or all of the time. Traditional agriculture uses low grade land for animal production. My cattle (a meat bread) are pastured on land unsuitable for any other type of agricultural production and the winter feed is produced on land that would not support cereal type production without significant artificial (oil/CO2 intensive) input. If I did not graze cattle (or sheep) on my pasture then the only alternative would be to leave it to return to the wild, which here would mean letting the deer and wild boar free access, which would increase their numbers due to increased habitat.
    • CommentAuthorCWatters
    • CommentTimeApr 23rd 2017 edited
     
    Posted By: Ed DaviesI heard the other day that with modern farming (make of that as you will), the UK can feed half a billion people.


    Google suggests you need between 0.07 and 0.5 Ha to feed one person but most of the references I found said that this assumes a vegetarian diet and at the lower end ignores soil degradation and erosion (eg not sustainable in the long term?).

    Google also says the UK is 24.2495 million Ha.

    So even if you could turn over the entire surface of the UK (every road, roof top, forest, solar farm etc) to food production that would only feed between 50 and 350 million people. UK population is currently 60 million ish.
    • CommentAuthorEd Davies
    • CommentTimeApr 23rd 2017 edited
     
    Actually, it was SteamyTea who posted “I heard the other day…”

    Edit to add: the easy mistake to make which results in quoting the wrong person is to select the text you wish to quote then click the quote link on another post, e.g., the next one. The selected text is quoted but the name is taken from the post of the quote link.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 23rd 2017 edited
     
    That's strange, CWatters, because
    http://www.telegraph.co.uk/foodanddrink/foodanddrinknews/8021327/Britain-least-self-sufficient-in-food-since-1968.html
    says 'British farmers were able to produce 78 per cent of all the food we ate ...'

    "Britain has not been fully self-sufficient since the eighteenth century. It imported large quantities of wheat, eggs and sugar during the Victorian era, growing an increasingly small proportion of what it ate until World War II, when millions of consumers followed the plea to "dig for victory". This self-sufficiency trend was immediately reversed after the war ended, however.

    Thanks to improvements in agricultural techniques and generous European Union subsidies, British farmers were able to produce 78 per cent of all the food we ate during the first half of the 1980s. It has been in decline since then."
    • CommentAuthorEd Davies
    • CommentTimeApr 23rd 2017 edited
     
    Posted By: CWattersUK population is currently 60 million ish.
    From the Wikipedia UK article:

    Population
    • 2016 estimate 65,110,000[4] (22nd)
    • 2011 census 63,181,775[5] (22nd)
    70 million's probably not that far off.
    • CommentAuthorEd Davies
    • CommentTimeApr 23rd 2017 edited
     
    Posted By: fostertomThat's strange, CWatters, because…
    I think that's consistent with what CWatters is saying.

    Suppose a third of the land is agricultural. That's 8e6 ha. That's feeding, in effect, 65e6 * 78/100 ~= 50e6 peeps. So that's 8 ha/50 peeps = 0.16 ha/peep which is, geometrically, pretty much in the middle of CWatters' 0.07 to 0.5 ha/peep.

    CWatters says 50 to 350 million people for all of the land so 50 million for a plausible amount of agricultural land is also consistent.

    Edit to add: On reflection, maybe I should have used 56e6 as the population rather than 65e6 a that was probably more current when 78% of food was being produced. But this is so broad brush anyway that I can't be bothered to update.
   
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