David Woolley <david@ex.djwhome.demon.invalid> wrote:
> On 03/01/2023 11:09, Spike wrote:
>> If you run the gas/oil-fired plants all the time, there are two benefits:
>>
>> 1) they can be run in the most efficient mode, rather than at a very
>> inefficient part throttle and having considerable fire-up costs and wasted
>> heat at shutdown,
>
> My understanding is that gas based plant is used precisely because it
> can be run up and down quickly. It's too expensive for base load use.
> One is typically talking about gas turbine, where the main useful heat
> content is in the gas itself, not in large quantities of water and heat
> exchangers.

Gas turbine-powered generators are ‘quick’ to start up (~45 minutes)
compared to a coal-fired power station (several days?).

During fire-up the turbines are very inefficient, from ~0% for the first 5
minutes, to 25% to about 45 minutes, when the second part of the
combined-cycle kicks in at about 60% efficiency.

The combined-cycle gas turbine (CCGT) uses ‘waste’ heat from the turbine to
provide steam pressure to run a second generator, thus improving the
overall efficiency of the system.

With 60% efficiency, each GW of power output uses 1/0.6=1.67GW of gas.

Interestingly, if a 1GW CCGT was replaced by a 1GW wind farm, real-world
data suggests the latter, over a year, would produce an average of 0.36GW,
leaving 0.64GW to be supplied by the CCGT in an intermittent regime of
stop/start and throttled-back running in which it might be only 40%
efficient.

So over the year the CCGT will use 0.64/0.4=1.6GW of gas, which is the same
as if it ran in efficient mode and the wind farm didn’t exist, the latter
having cost money and materials to no real effect.

--
Spike

On Tuesday, 27 December 2022 at 08:52:38 UTC, MB wrote:
> On 26/12/2022 20:22, wrights...@aol.com wrote:
> > Modern coal mining is largely automated.
> Once it is installed.
The tunnelling etc is done by machines.
Bill

On Sunday, 1 January 2023 at 09:48:35 UTC, Jim Lesurf wrote:

> > Winds finally up and blowing a good 'un today t keeping the gas
> > consumption low lets hope that carries on for a while at least.
> Yes. Despite the variability, every kWh from wind, etc, is one we didn't
> need gas for.
> Jim

So there's generating machinery sitting around doing nothing.
Bill

On 05/01/2023 16:29, wrightsaerials@aol.com wrote:
> So there's generating machinery sitting around doing nothing.

That predates renewables. There has always been excess capacity for
periods of peak demands, including commercial breaks.

On Thu, 5 Jan 2023 16:44:14 +0000, David Woolley
<david@ex.djwhome.demon.invalid> wrote:

>On 05/01/2023 16:29, wrightsaerials@aol.com wrote:
>> So there's generating machinery sitting around doing nothing.
>
>That predates renewables. There has always been excess capacity for
>periods of peak demands, including commercial breaks.

We might expect this effect to diminish as more people move to online
streaming of TV programmes on demand, rather than everybody watching
the same broadcasts at the same time.

Rod.

On 05/01/2023 16:44, David Woolley wrote:
> That predates renewables. There has always been excess capacity for
> periods of peak demands, including commercial breaks.

That is when the pump storage stations are valuable, they can start very
fast or if it is expected they might be needed then they can kept
turning over ready for a much quicker start.

On Thursday, 5 January 2023 at 16:44:16 UTC, David Woolley wrote:
> On 05/01/2023 16:29, wrights...@aol.com wrote:
> > So there's generating machinery sitting around doing nothing.
> That predates renewables. There has always been excess capacity for
> periods of peak demands, including commercial breaks.
But the extent of it is now far more.
Bill