🚀 go-pugleaf

Bernard Peek wrote:
> In message <gpmjcr$aav$1@news.motzarella.org>, ~misfit~ 
> <misfit61nz@yahoo.com.au> writes
> 
> 
>>> There is nearly always surplus capacity on the grid during off peak
>>> times as because of the sheer size and mass of large turbine rotors
>>> it takes several hours to run them up, also most turbine failures
>>> occur during run down/up so engineers prefer to keep them under load
>>> anyway,
>>
>> I think you'll find that they like to keep them spinning, but not 'under
>> load', at least no more load than minimum.
> 
> They keep the rotors turning because if you leave them stopped they 
> start to bend under their own weight.
> 
> It doesn't take a lot of steam to keep the rotors turning so they don't 
> burn very much fuel. As soon as you draw any power from them they slow 
> down unless you turn up the steam pressure, which requires more fuel. 
> The generators that are under load are kept at a fixed 3600rpm by 
> adjusting the steam pressure; more load, more steam required. So the 
> fuel usage is mostly dependent on the load. If you cut down the amount 
> of electricity being drawn from the grid you cut down the amount of fuel 
> being used.
> 
> There is never any power that's not being used and increased load 
> immediately increases the amount of fuel being used. The systems are 
> automated so that when a generating set is put under load it slows down. 
> The slowdown triggers the steam valve to open more. Opening the steam 
> valve draws in more water. Drawing in more water cools the boiler. 
> Cooling the boiler triggers an increase in the fuel feed.
> 
> Some systems can respond to increased demand in less than a second. 
> Others take a lot longer. Slow systems like nuclear reactors are used 
> for base-load. Fast response systems are used for peak loads like 
> half-time at the cup-final.
> 
Nice explanation although from a 'not used' point of view there is always 
inevitable energy loss over the whole grid system which the generators see as 
'load'.