Re: Grand Apagon - Electricity (not) in Spain

On 3/05/2025 8:40 am, john larkin wrote:

On Fri, 02 May 2025 13:41:07 -0700, john larkin <jl@glen--canyon.com>
wrote:
 

On Fri, 2 May 2025 17:49:48 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
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Bill Sloman <bill.sloman@ieee.org> wrote:
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On 3/05/2025 12:43 am, john larkin wrote:

On Thu, 1 May 2025 11:24:13 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
>

Chris Jones <lugnut808@spam.yahoo.com> wrote:
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>

There is nothing magic about the current from a rotating generator that
cannot be exactly replicated by an inverter ...

>
Inertia.  Not magic but physics.   A store of energy that can be drawn
on instantly for several seconds.  Only an inverter with a massive
energy storage system could match that; domestic systems can't.

>
A boiler full of superheated water stores a lot of energy too. And
hydraulic steam valve actuators move fast.

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Not all that fast. 50Hz is probably more than they could track. 60Hz
would be even more difficult.

>
They have no problem at a few cycles per second, as London Transport
discovered in the early days of computers.
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London Transport was powered by Lotts Road Power Station.  The load was
mainly underground electric railways, trams and trolleybuses. but they
took the electricity supply for their offices from there too.  The first
computer they installed kept crashing and the problem was traced to dips
in the power supply rails.
>
After a lot of investigation, they discovered that the AC mains supply
had alternate (or perhaps every third) cycles much lower in voltage than
the others (and I think there must have been a timing error too).  The
power supply smoothing capacitors were unable to store enough energy to
tide them over the dips and the result was a regular dropping of the
'stabilised' supply rails.
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The fault was traced back to Lotts Road, where it was found that a steam
valve was constantly cycling due to an unstable control loop.  This
hadn't had any effect on the trams, so nobody had bothered to do
anything about it.
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Conclusion:
A tram stores more energy than a computer capacitor bank.

>
I used to design steamship throttle and boiler control systems [1]. A
steamship throttle valve hydraulic actuator is powered by low pressure
oil (from a standby gravity tank) and slews in a few seconds. But
serious high-pressure hydraulic actuators have multi-horsepower
outputs and bandwidths of hundreds of Hz.
>
A decent steam valve will nicely overlap the equivalent bandwidth of a
big generator's inertia. Field control can be made fast too.
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Control engineers would be better at desiging stable power systems
than greenie politicians.
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[1] Big ships are mostly diesels now.
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I was once stranded dead in the water in the Gulf Of Mexico/America,
with maybe 100 other guys, on a LASH ship sea trial, when the main
turbine steam valve actuator locked up and had to be disassembled and
redesigned.

  Of course a big generator can't sink power. If a few million people
are incentivized to have rooftop solar and to get paid to push it back
into the grid, and there's no way to stop them, things will get bad on
a sunny afternoon.

In Australia, the utilities cut the price they'd pay for excess current generated by a roof-top solar set-up very early on.
About 40% of new roof-top solar installation in Australia now include a Tesla Powerwall or a similar big battery, so the household can store excess energy until they need it. Not paying the utility rates for power that you use at night lets you pay off the whole installation over about seven years. Not dramatic, but well worth doing if you have the capital.
--
Bill Sloman, Sydney