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From: Martin Brown <'''newspam'''@nonad.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: Grand Apagon - Electricity (not) in Spain
Date: Fri, 2 May 2025 11:03:55 +0100
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On 01/05/2025 18:41, Bill Sloman wrote:
> On 2/05/2025 2:21 am, Liz Tuddenham wrote:
>> Bill Sloman <bill.sloman@ieee.org> wrote:
>>
>>> On 30/04/2025 7:59 pm, Liz Tuddenham wrote:
>>>> Bill Sloman <bill.sloman@ieee.org> wrote:
>>>>
>>>>> ... pumped hydro storage has the spinning
>>>>> turbines, but grid scale batteries have invereters, which can 
>>>>> reacta lot
>>>>> faster than any spinning turbine,
>>>>
>>>> I thought the stabilising effect of a spinning turbine was because it
>>>> *didn't* react quickly.
>>>>
>>>> The grid frequency begins to fall so energy from the moving parts is
>>>> converted to electrical power which is fed into the grid to increase.
>>>> the frequency.  This results in a loss of stored mechanical energy 
>>>> which
>>>> causes the turbine to begin slowing down - which is detected by the
>>>> control system and used to feed more water/gas/steam into the 
>>>> turbine so
>>>> its speed is returned to normal.
>>>>
>>>> The interface between the stored mechanical energy and the electrical
>>>> energy demand has an almost instant response and is inherently stable
>>>> without needing elaborate control algorithms.
>>>
>>> But it isn't actually doing anything.
>>
>> Yes it is, basic electrical engineering theory.
>>
>> In effect it is a constant speed generator connected to variable load;
>> increase the load and more electrical energy immediately flows into the
>> load, taking mechanical energy from the inertia of the moving parts.
>> They then begin to slow down and the much more heavily damped mechanical
>> regulator feeds in more energy to them from the primary source.
> 
> So it is completely passive. A big battery isn't a primary source but it 
> can provide enough DC current to let your grid scale inverter generate 
> exactly the AC output that you need.

There is a surprising amount of kinetic energy that can be stored in a 
flywheel or other rotating piece of big heavy machinery. The grid has 
adopted large scale solar PV and wind farms with some very flaky 
inverter technology whose interractions are not at all well understood.

One of the internal reports I was reading recently mentioned that they 
were thinking about funding a PhD to look into some of the complexities. 
It is pretty clear that the system is not well thought out.

> Why futz around with the rotating metal? It may entertain tourists, but 
> that's really all that it is good for.

Because it was always just there and now that it isn't the replacement 
inverters on many of the big installations are nowhere near good enough 
at simulating the required behaviour. They are too inclined to drop off 
and save themselves (much like nuclear plant also does). I suspect that 
Spain doesn't have a great deal of battery storage or pumped water.

Based on the time it went tits up it seems likely that it failed due to 
too much power being forced into the network and not enough load of last 
resort or exports to France down the one puny cable they do have.

UK's intermittent loads of last resort are also diminishing as steel 
works closed although it is never really sunny enough here to matter and 
wind turbines can be easily feathered (and paid handsomely to do SFA). 
There is really only the chloralkali plants at Runcorn left now.

Silly electricity prices based on the wholesale price for gas have 
pretty much destroyed aluminium and steel making in the UK. Scotland has 
a couple hanging on by their fingernails hoping for a reprieve.

-- 
Martin Brown