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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Grand Apagon - Electricity (not) in Spain
Date: Sun, 4 May 2025 15:42:17 +1000
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On 4/05/2025 4:30 am, john larkin wrote:
> On Sat, 3 May 2025 19:23:11 +0200, Jeroen Belleman
> <jeroen@nospam.please> wrote:
> 
>> On 5/3/25 17:12, john larkin wrote:
>>> On Sat, 3 May 2025 14:24:07 +0200, "Carlos E.R."
>>> <robin_listas@es.invalid> wrote:
>>>
>>>> On 2025-05-02 12:03, Martin Brown wrote:
>>>>> 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.
>>>>
>>>> Network grade batteries, none, I believe. There are plans for water
>>>> pump/generators. Some of the islands do have them.
>>>>
>>>> It seems that solar panels and wind farms mostly have the type of
>>>> inverter that follow the shape of the voltage already in the grid, with
>>>> detection to bail out if things go nuts. There is the suspicion that
>>>> this was at least part of the problem.
>>>>
>>>> But there is another type of inverters that force the shape, ie,
>>>> simulate inertia.
>>>
>>> Where do they get the energy from?
>>>
>>
>> To have a bit of margin to regulate, PV installations will have
>> to either run somewhat below the bleeding edge, or to store a bit
>> of energy in local batteries.
>>
>> Jeroen Belleman
> 
> Most run at the MPPT point, so have no reserve to save the grid.

They don't have to run at that point all the time, and can be designed 
to move away from it when necessary. The grid system can broadcast an 
instruction to do that, and the mobile phone system can instruct 
specific PV installations in specific localities to do that.

> And a lot of cloud cover or still wind will precipitate the very crisis 
> that needs reserve.

The system is designed to cope with that. The problem happens when the 
local fluctuations happen to combine in a way that the regular system 
can't cope with.

> It doesn't make sense to me for a multi-country grid to depend on "a
> bit of energy stored" in household batteries and inverters for
> emergency reserve power.

When 30% of roof-tops solar panels - as they are in Australia - and an 
increasing proportion these systems are backed up by Tesla Powerwalls 
and the like - it can be quite a bit of energy.

Back in 2008

https://en.wikipedia.org/wiki/Hot,_Flat,_and_Crowded

pointed out that electric car batteries in parked and notionally 
charging electric cars could serve as a very effective gird-scale battery.

> As the grids get greener, expect power to get less reliable and much
> more expensive. Hopefully the USA will use more NG, build more
> pipelines, and drill, baby, drill.

And the people who paid for the climate change denial propaganda you are 
parroting will keep on making a lot of money out of wrecking the climate.

-- 
Bill Sloman, Sydney