Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.
Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
 Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




Politics: Is Hinkley C dead?

Bottom of Page

301 to 330 of 376

  1. <
  2. 1
  3. ...
  4. 5
  5. 6
  6. 7
  7. 8
  8. 9
  9. 10
  10. 11
  11. 12
  12. 13
  13. >
    • CommentAuthorEd Davies
    • CommentTimeAug 10th 2016
     
    The point about CH, though, is that there was a large change in society's expectations without some Grand Plan made by a Great Leader but instead by step-by-step developments made by lots of people: engineers developing technologies, salesmen, architects and installers pushing them out and individuals buying systems and having them installed.
    • CommentAuthorringi
    • CommentTimeAug 10th 2016
     
    Before "north sea gas" gas cost too much for heating. Even with coal most households could only afford to heat one room. I expect the reduction in the cost of food has a lot to do with ch becoming common.
    • CommentAuthorbillt
    • CommentTimeAug 10th 2016
     
    But virtually nothing is done by Grand Plans and Great Leaders. Even the UK electricity distribution system largely evolved piecemeal. The CEGB is the nearest to a Grand Plan, but that still developed bit by bit and over many years. It didn't spring fully formed from one man's inspiration.

    Posted By: ringiBefore "north sea gas" gas cost too much for heating. Even with coal most households could only afford to heat one room. I expect the reduction in the cost of food has a lot to do with ch becoming common.


    Small CH systems were starting to become popular before the natural gas conversion in the UK. In fact, there wasn't any immediate change in gas pricing due to the changeover.

    I think only heating one room was as much due to the mess and labour involved in keeping open fires going as it was to cost. Of course the much better efficiency of a CH system meant that the running costs weren't that much greater than that of heating one room.
    • CommentAuthorfinnian
    • CommentTimeAug 10th 2016
     
    The issue of PV inverters disconnecting too soon is already being dealt with (at least in Australia): the standards were updated, but it looks like it wasn't actually a problem anyway. I think the moral of the story is that it is easy to come up with 'difficulties' with distributed generation but many of them are pretty easily resolved.

    https://www.aemo.com.au/Media-Centre/-/media/43BE01476E2D4992A3BDA2DA2E1A14A4.ashx

    "Small-scale PV generating systems are connected to the network via inverters that provide an electronic interface to the power system. The technical properties of these inverters were historically set by Standards Australia in AS 4777–2005 Grid Connection of Energy Systems via Inverters. This version of the standard predated expectations of the mass uptake of PV systems, and therefore did not necessarily have the required specifications to ensure high penetration would have minimal impact on the power system.
    A revised standard (AS/NZS 4777.2–2015) was published on 9 October 2015. It sets requirements for future installations of inverter-connected generation, but does not enforce any retrofitting of requirements to existing installations. Among other requirements, the new standard ensures compliant inverters will not disconnect for frequencies in the range of 47 Hertz (Hz) – 52 Hz, minimising any negative impact during frequency disturbances."

    Actually if you look at figure 8 you can see that inverters charging and generating actually improve stability for large frequency disturbances by throttling their output.
    • CommentAuthorfinnian
    • CommentTimeAug 10th 2016
     
    See also section 5.1.2 which explains why inverters are actually pretty good at this stuff.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 10th 2016
     
    I am not sure because I was not looking at the Australian grid network when I was there. But don't they have more of a radial design than ours so can be a lot more fault tolerant.

    As for the cost of updating the national grid network, think it was about £31bn and we are being charged £12/year towards the cost, so raising something like £0.75bn/year towards it.
    • CommentAuthorfinnian
    • CommentTimeAug 10th 2016
     
    I can't see how network topology is obviously related to the frequency response of the grid, but maybe I'm missing something.

    Another thing that is promising the using demand response to stabilise the grid (and provide
    short term storage):

    www.dynamicdemand.co.uk/pdf_fridge_test.pdf

    There are synchronous spinning things on the load side too.
    • CommentAuthorEd Davies
    • CommentTimeAug 10th 2016
     
    Thanks Finnian, interesting read. E.g., that the Australian grid can separate and continue to operate as more than one grid. Given the size of the country that makes a lot of sense, of course.

    I think the motivation for the G59/2 revision to ramp down generation rather than switch off abruptly as the frequency goes out of the normal range came mostly from Germany where there was a fear that if the grid was struggling a bit, so frequencies were low, then all the PV dropped out in one go this could result in a catastrophic collapse.

    Still, this is all about inverters being well behaved at the edge of the network rather than the slightly separate issue of them carrying out the stabilizing function in the core, instead of rotating machinery.
    •  
      CommentAuthordjh
    • CommentTimeAug 10th 2016
     
    Posted By: Ed DaviesStill, this is all about inverters being well behaved at the edge of the network rather than the slightly separate issue of them carrying out the stabilizing function in the core, instead of rotating machinery.

    The Australian document does point out how they help with stabilisation, as Finnian said.
    • CommentAuthorCWatters
    • CommentTimeAug 10th 2016
     
    So we could spend the saving on windmills with a strike price way over £140MWh...


    Offshore wind seems to be getting cheaper rapidly...

    http://www.twobirds.com/en/news/articles/2016/global/offshore-wind-in-the-netherlands-borssele-tenders-in-rapid-succession

    "Offshore wind in The Netherlands"

    "Dong Energy won the tender with an average bid strike price, excluding transmission costs, of 72.70 EUR per MWh during the first 15 years of the contract."

    72 Euro is about £63.
    • CommentAuthorEd Davies
    • CommentTimeAug 10th 2016
     
    Posted By: djhThe Australian document does point out how they help with stabilisation, as Finnian said.
    Yes, they (inverters and chargers to the new standard) help with stabilization when there are relatively big disturbances but they don't provide the basic frequency control for routine operation, yet, as this sentence in 5.1.2 implies:

    This information will be important if, in future, battery storage and PV systems were to provide
    frequency control services or other market benefits.
    That is, they're not currently used as a replacement for rotational stabilization of frequency except as an assistance when things are a already going a bit wrong. Inverters like the Sunny Island (Eigg and Paul Camilli use those or ones like them) do control the (local) grid frequency whereas the PV inverters and chargers described in that document only respond to it in a way which makes that control easier.
    •  
      CommentAuthordjh
    • CommentTimeAug 10th 2016
     
    The IES characteristics required in AS/NZS 4777.2–2015 will become increasingly significant for control of power system frequency, particularly given the potential for many thousands of MW of PV generation and battery storage capacity to be connected via inverters compliant with AS/NZS 4777.2–2015. In particular, the response of these IES to frequency disturbances will be:
    * Much faster than governors on any conventional generating plant.
    * Available to respond to high frequency whenever PV or battery storage systems are generating.
    * Available to respond to low frequency whenever battery storage systems are charging.

    Effectively, these inverters have the potential to provide an extremely rapid Contingency Frequency Control Ancillary Services (FCAS) response to frequency disturbances in the future. Contingency FCAS is an instrument AEMO utilises to manage the power system frequency during a frequency disturbance.
    • CommentAuthorringi
    • CommentTimeAug 10th 2016
     
    They can't respond to low frequency whenever PV systems are generating!
    • CommentAuthorfinnian
    • CommentTimeAug 11th 2016
     
    1) That standard does not require the distributed grid-connected inverters to respond to small frequency disturbances, so the assumption is that they don't.

    2) The bit in 5.1.2 is talking about the potential for inverters to provide stability services, not what current distributed grid-connected inverters do. Note that the inverters are regarded as a potential asset; possibly they are thinking ahead to future standards.

    Ringi, I can't quite figure out what your sentence means.
    • CommentAuthorEd Davies
    • CommentTimeAug 11th 2016
     
    DJH, the key words in your quote are “contingency” and “ancillary”. Yes, the inverters help make frequency control easier, particularly in extreme cases, but they don't *currently* provide the basic control which is *currently* provided by rotating machinery. If you had a network with just PV inverters of the sort currently installed (even if they were all to the newer standard) the system would likely be unstable. Maybe adding chargers which respond as described there would make it less unstable, I'm not sure. Still, it'd all be pretty wobbly as nothing is really directly controlling the frequency as such.

    And, you wouldn't have the tight frequency control which we expect. For example, you wouldn't have a cumulative average of 50×86'400 cycles in 24 hour periods so that electric clocks don't gain or lose too much.

    Their behaviour is quite unlike, say, the Sunny Island which will push or pull on the phase to keep its local grid frequency correct to whatever nominal frequency its settings indicate (50 or 60 Hz) plus or minus the small amount it uses to signal battery state to other inverters.
    • CommentAuthorEd Davies
    • CommentTimeAug 11th 2016
     
    Posted By: ringiThey can't respond to low frequency whenever PV systems are generating!
    Posted By: finnianRingi, I can't quite figure out what your sentence means.
    I think he means that if the frequency is low, signalling a shortage of generation for current demand, PV systems can't respond to correct the situation by producing more as they presumably are already producing as much as they can.

    This contrasts with battery charger/inverters which can respond by reducing their charge rate or by outputting more AC electricity when the frequency droops.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 11th 2016
     
    10 minutes with Excel shows what happens if you have phases out just a little bit (1 Hz).
    It will wreck your power factors somewhat.
      Power Cycles.jpg
    • CommentAuthorfinnian
    • CommentTimeAug 11th 2016
     
    Well, if you are in a situation where PV supply isn't generating enough power to match demand you have a more basic issue which isn't going to be fixed by being clever with inverters (which is why I keep saying that storage is the real issue).

    SteamyTea, what makes you think that devices would draw current at 50Hz in a grid where 51Hz is being generated?
  19.  
    <blockquote><cite>Posted By: SteamyTea</cite>10 minutes with Excel shows what happens if you have phases out just a little bit (1 Hz).
    It will wreck your power factors somewhat.<div class="Attachments" id="Attachments_245600"><ul><div><img src="/newforum/extensions/InlineImages/image.php?AttachmentID=6422" alt="Power Cycles.jpg"></img></div></ul></div>


    </blockquote>http://www2.nationalgrid.com/UK/Services/Balancing-services/Frequency-response/Firm-Frequency-Response/FFR-Bridging/

    A little bit to simple Steamy there is a whole industry built around correction of frequency.
    • CommentAuthorringi
    • CommentTimeAug 11th 2016
     
    Posted By: Ed Davies
    Posted By: ringiThey can't respond to low frequency whenever PV systems are generating!
    Posted By: finnianRingi, I can't quite figure out what your sentence means.
    I think he means that if the frequency is low, signalling a shortage of generation for current demand, PV systems can't respond to correct the situation by producing more as they presumably are already producing as much as they can.

    This contrasts with battery charger/inverters which can respond by reducing their charge rate or by outputting more AC electricity when the frequency droops.


    Spot on there are 4 states that need correction but the standard only covers 3 of them. The standard also does not require battery charger/inverters to output when in low frequency, but could if it was more demanding.
    • CommentAuthorringi
    • CommentTimeAug 11th 2016
     
    Why do we need the frequency to be stable at all, if we don’t have any rotating generators……

    The frequency just seem to be used as a easy way to control the output of rotating generators and not have any real reasons to be stable other than to keep the rotating generators happy.

    But we will then just need to talk about keeping the voltage stable instead….
    •  
      CommentAuthorfostertom
    • CommentTimeAug 11th 2016
     
    Now it gets interesting - sounds more 'distributed', IP-y in philosophy. If it sounds right it prob is right.
    • CommentAuthorfinnian
    • CommentTimeAug 11th 2016
     
    I think there is actually a substantial amount of synchronous rotating machinery on the demand side anyway, so the frequency can't drift that fast.

    There are a bunch of modifications to how distributed inverters perform that would be helpful if you wanted to run the grid with them alone.

    The (current) inability of distributed inverters to restart from a zero-voltage condition is probably only a major difficulty if the whole of Europe goes dark and there is absolutely no utility scale generation.
    •  
      CommentAuthordjh
    • CommentTimeAug 11th 2016
     
    Posted By: ringiWhy do we need the frequency to be stable at all, if we don’t have any rotating generators……

    Posted By: finnianI think there is actually a substantial amount of synchronous rotating machinery on the demand side

    My parents used to have a clock on their mantelpiece that was powered by a synchronous motor. IIRC the electricity supply is guaranteed not only to be at nearly the right frequency but to contain the correct number of cycles over time to keep such clocks accurate. (i.e. the average is EXACTLY 50 Hz)
    • CommentAuthorringi
    • CommentTimeAug 11th 2016
     
    But way do we have to let history define what we do now, after all, most new equipment is designed on work on 50Hz and 60Hz, along with whatever it can get when used in the 3rd world.

    But keeping the frequency stable without any rotating generators is EASY, however the voltage will then become unstable.
    • CommentAuthorEd Davies
    • CommentTimeAug 11th 2016
     
    Posted By: ringiWhy do we need the frequency to be stable at all, if we don’t have any rotating generators……
    Alternatively, why do we need to have the frequency change at all? Currently it's a way in which rotating generation is controlled - if the frequency drops a bit/phase lags a bit the inertia in the generators which have inertia/power to hand pull it back or they rotate a fraction more slowly and their governors let a bit more steam in to correct.

    With a slightly less Victorian way of signalling perhaps we could say something like the negative to positive transition of phase 1 is synchronized to the beginning of GPS/Galileo/Glonass seconds plus an integral multiple of 20 milliseconds and be done with it.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 11th 2016
     
    Posted By: finnianSteamyTea, what makes you think that devices would draw current at 50Hz in a grid where 51Hz is being generated?
    Was really just showing that you do need to keep things in phase or you start to flatted the top and bottom of the curve.
    As I said earlier, it may be possible to design something with a DC backbone, though it probably has little, if any advantages in the UK.

    I like out very reliable national grid, start sticking an inverter in each house and you will quickly loose that reliability.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 11th 2016
     
    •  
      CommentAuthorfostertom
    • CommentTimeAug 17th 2016 edited
     
    While US builds its first
    http://www.fastcoexist.com/3062881/world-changing-ideas/americas-first-offshore-wind-farm-is-almost-ready
    UK approves another massive one, while Hinkley is in limbo (or hopefully better)
    https://www.theguardian.com/environment/2016/aug/16/hornsea-project-two-windfarm-second-phase-grimsby

    "... offshore windfarms will be on course to meet 10% of the UK’s electricity by 2020. Hinkley Point C ... was not expected to be constructed until the mid-2020s and even then would produce only 7% of the country’s power.
    • CommentAuthorringi
    • CommentTimeAug 17th 2016
     
    I still can't understand why we are not allowed large wind farms on the rig that overlooks the top of the M6. I was up Kinder Scout today, and the land towards the Sake Pass would also be good for wind farms.

301 to 330 of 376

  1. <
  2. 1
  3. ...
  4. 5
  5. 6
  6. 7
  7. 8
  8. 9
  9. 10
  10. 11
  11. 12
  12. 13
  13. >
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press