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Sunday, 4 August 2013

Power bollocks

I was just reading Christopher Booker’s  article this morning in the Telegraph this morning.

We could soon be paying billions for this wind back-up

In it he explains the Bizarre thinking that to stop the lights going out the government is going to use all the backup diesel generators that exist in hospitals and other places that need to have an emergency supply of electricity.

The answer National Grid has come up with, only made possible by the latest computer technology and “cloud software”, is to hook up thousands of diesel generators, remotely controlled by the grid, to provide almost instantly available back-up for when the wind drops.

Personally speaking as an engineer that has spent most of his working life working with diesel generators, I think it is a disaster waiting to happen.

I don’t see how it could work.

1. All types of generators have a different “Characteristic”. Steam turbine generators, gas turbine generators, and diesel generators all respond differently to changes in load. All these generators have to supply power within a narrow frequency band either side of the grid frequency of 50 Hz. Usually within a maximum of + or - 3 Hz. How is your local hospital’s 1 Mw diesel set going to respond to the response of  a 2 Gw gas turbine. The danger is that unless the load sharing is precise (involving electronic governors these days), you could end up with a gas turbine actually “motoring” a diesel generator. In other words the DG is being driven electrically against it’s will. NOT A GOOD THING. It usually ends up with large lumps of diesel engine deciding to spread it’s self into it’s component parts. (I know. I walked past such a generator 5 seconds before it did it.). That’s your hospital fucked in the middle of winter when the wind turbines are not working.

2. All emergency generators are just that. They are arranged that if the mains power fails they are an autonomous entity.Just there to  supply the Hospital, public building, brothel, etc. Usually they are arranged that if the main supply circuit breaker drops out due to mains failure, the standby diesel generator will start and then close it’s emergency breaker onto the needed system.. QED. For safety reasons, the mains supply breaker and the emergency supply breaker are interlocked so that neither can be closed simultaneously. I’d love to know how they are going to load share between their patients and the grid?

3. As above. Does the hospital, if the rules change on electrical safety, save it’s patients or sell it’s Kws to the grid?

I feel that this is a cynical ploy by a government that has lost the plot on energy production to try and calm the average citizen, that the lights will remain on.

I have candles.

12 comments:

  1. Richard North (EU Referendum) has been covering this for some time, and it now transpires that several new companies have been set up specifically to exploit the lavish subsidy and standby payments on offer. So not only will broken conrods be flying past hospital beds, but over the English countryside as well.

    Perhaps someone will hold a competition to see whether they can travel further than a broken wind turbine blade in a gale...

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  2. Should the lights go out, then so will CCTV cameras & authorities' communications. The Duggan riots of 2011 will be a playground 'strop' in comparison.

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  3. While it may be the "ideal" specification/operating range, +/- 3Hz is much too narrow for the majority of power supplies. The actual range for most electrics and "household" electronics (which are adequately rectified for shabby power conditions) is about 10Hz (or between 40 to 70Hz generally), unless your talking about avionics, which need absolute precision, but avionics tend to run on "cleaner, more stable" three-phase power. I've seen and used plenty of generators perform under less-than-ideal conditions -- say, at 160% [over]load for hours and hours. It depends on the generator -- or as you say, "characteristic." I'd trust a diesel-powered generator over a petrol generator any day, by the way. Diesels can handle a greater load for longer periods, but they are somewhat slower to respond to changes in load.

    As for the supplying back into the grid whilst still supplying critical systems in a building such as a hospital, well, yes, some sort of governor/limiter would be vital, but I can't see how even that would function adequately in a lower power/brown-out situation. Any system that would be able to measure and redistribute the load from several generators within a city block also needs adequate power, which it wouldn't have I suspect. I agree this concept would likely fail spectacularly, particularly because few buildings in a typical city block have any kind of backup generator capable of fully supplying power for its own needs. Therefore each generator would need its own secondary governor to prevent overloading from requests from the grid. It could be done, but it would be prohibitively expensive and ultimately futile.

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  4. +/- 3Hz, no the synchronisation needs to be fractions of a Hz!

    The way the power company used to do it was expensive modems on leased lines as if they start doing switching at the big switching centres and it's not done at the precise moment of no power flow then they lose the contactors which have a very limited life and cost millions to fix and need large bits of the network to be isolated to actually repair them!

    Now BT have ceased the leased lines they had to do the comms another way and would have appreciated some notice from BT...

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    Replies
    1. Yes the frequency needs to be exact. What I meant is that the circuit breaker will drop out at a discrepancy of 3Hz.

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    2. A N Other Filthy Engineer7 August 2013 at 12:11

      Have a look at this:-

      http://www.dynamicdemand.co.uk/grid.htm

      It would appear that the National Grid starts getting serious problems if the frequency strays outside +2 to -1.5 Hz.

      Also the legal limit is + or - 1%, i.e. + or - 0.5 Hz. See here:-

      http://www.nationalgrid.com/uk/Electricity/Balancing/services/frequencyresponse/

      + or - 3Hz is way too wide a range according to the National Grid's requirements.

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  5. Smart meters!!!! British Gas already have a brainwashing exercise in place.
    Shut down everything (apart from the House of Commons bar) and all will be well until the wind blows again.
    It is just to easy to describe the thinking of those in power as stupid. It must be a deliberate policy to turn the lights out - the only question is why?

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    Replies
    1. It is just to easy
      Sorry - too

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  6. I'd heard about this expedient, but knew nothing about the technical details - until now!
    What do the engineers of the National Grid think about it? Do they have some (irreverent) website of their own, anyone know?

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  7. Whilst working at a fire station, they all have their own diesel back up gen, I saw a brand new gas powered CHP being installed in the boiler room. The people putting it in said a smaller CHP was being developed for households. Does anyone know if this would be suitable for use in a power cut, as a may chance my arm on one when the old boiler gives up? If it would be cheaper AND provide power when the wind doesn't blow, then I'm all for fracking.

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    Replies
    1. http://www.chpa.co.uk/micro-chp_190.html

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  8. My parents have one. Works well, better in winter when they need the heat on top of the hot water. Supplies enough for when the small number of electrical stuff is on idle/standby.

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