National Grid and current loss

great unwashed

Can someone tell me how the Irish national grid works in terms of this:

there is x electricity demand from the population so we have to produce x+y electricity in case demand goes up suddenly. If our demand is 4 GW as a nation then we should try to produce 4.2 - 4.5 GW in case demand changes up or down.

What happens that extra electricity? Is there an overflow-pipe-like mechanism which earths the unused electricity? Or does the extra capacity stay in the grid like a battery?

Stoner

what happens is as follows, I may be corrected by someone with more up to date information , but this is essentially an economics questions so the theory is correct but the different fuel type could be added to or reduced.

Power is generated at its base load by using the cheapest fuel, ie we know that we require a minimum of X GW, so we invest heavily in a plant that can run on the cheapest fuel, for example in this country we worked out that we should spend on coal stations to power up the base load (note coal is hard to control, i.e bring back down).

coal was cheap but hard to control so we covered our base load with it.

to pick up the peaks we can use oil, followed by gas, oil being mid peaks and gas being the highest peaks.

Oil generators are cheaper then gas, but oil is dearer than coal, but the generators are cheaper then coal, but dearer then gas, LOL

what I'm saying is that the dearer the generating equipment , usually the cheaper the fuel, so a gas turbine could be very cheap, but gas is very dear, so you only use the gas for the peak times.

All generation plants have a life span, this is taken into account as the cost of the plant is important for obvious reasons, we try to do stuff like pump water up a mountain at night, this increases our basic entry level as we use less power at night so this brings up our nightly power usage and our daily power usage down, so we can generate more with coal and use the hydro power during the day.

Its all about the balance between the
cost of generation equipment
lifespan of the generation equipment
the cost of the fuel
and how easy it is to control the plant, in this example coal is the slowest and gas is the quickest, thats why you cant use coal in the peaks, and why gas has a good response to spikey demands.

Mix into this dodgy stats and info on what is the best fuel etc and dodgy fuel suppliers and you mess the whole thing up.

Generation companies all over the work spoof up the stats to back up where they get their supplies from. i.e. not using coal for enough generation so that more oil is required etc. and on top of dodgy deals etc you have human error.

Good engineering will get the balance right.

does that explain it?

dingding

Stoner, You are correct about the base load, however the problems with some of the other sources that you mention are not easy to start up quickly.

Ideally much of the non-base load is met by hydro power which can be brought up to speed quickly.

There was a scheme in Wicklow where water was pumped up and down between 2 lakes. The base load can be increased by the power required to pump the water up the hill, and the excess capacity can be used to meet surges.

Previously companies got cheaper exectricity if the signed up for a scheme that the load could be disconnedted in the case of a frequency drop, which is one of the symptoms of a severe network overload.

Also with the interconnector to Northern Ireland and onward to the UK and Europe via N Ireland has reduced teh reliance on some of these techniques. The peak loads are slightly different between ROI and NI, and also the electricity generated to allowed for surges to be shared between both companies.

Jnealon

great unwashed wrote: »

Can someone tell me how the Irish national grid works in terms of this:

there is x electricity demand from the population so we have to produce x+y electricity in case demand goes up suddenly. If our demand is 4 GW as a nation then we should try to produce 4.2 - 4.5 GW in case demand changes up or down.

What happens that extra electricity? Is there an overflow-pipe-like mechanism which earths the unused electricity? Or does the extra capacity stay in the grid like a battery?

If the demand is 4GW then the total generation would be around 4GW give or take a few MW for the losses on the transmission system. If there is more generation then demand then the frequency will rise and thats not good. There is no overflow pipe but there is an interconnector to the north which is connected to the UK.
There are generators that are on standby just in case another generator trips etc or the demand suddenly increases.
The generator in Turlough Hill is used at peak demand but it only lasts as long as the water flows from the top lake to the bottom lake