Smart grids are a bit of a buzzword at the moment - and a bit scary.
The idea is that you use your electricity meter to tell you how much electricity you are using, and what the price is.
Sounds good - but mine is in the cupboard outside and I never go near it. I suppose that some people will though, which does make it worthwhile.
The second idea is that you can sell electricity back to the grid.
Well, that's a bit scary.
I'm not an electrical engineer but I know a few people who are worried by this. Remember that electrical production and consumption have to be ballanced - if they are not the grid speeds up or slows down from 50Hz, and damages electrical equipment.
It's going to be difficult with wind, wave and tidal - difficult, but manageable. Now put a wind turbine on every house in britain, and change the windspeed - what's electrical production going to do - how can you ballance that?
Yes, hypothetical, but valid - there needs to be a limit on how much electricity can be supplied to the grid, and a simple statement of "the grid must buy from anyone" is going to cause problems.
...so nice try Cameron, but no.
Showing posts with label grid stability. Show all posts
Showing posts with label grid stability. Show all posts
Friday, January 16, 2009
Wednesday, December 17, 2008
The grid code
I'm not sure if I've yet published a post explaining the grid code - so here goes.
Our grid is alternating current, with a frequency of 50Hz. This is done as it then becomes very easy to step up and down the voltages to transmit it accross the country at high efficiencies.
The easiest way of keeping the grid at 50Hz is to turn over a turbine 50 times a second. Ofcourse the turbine can be powered in many different ways - by wind, water, gas or steam.
The drag on the turbine from the generator must equal the power being applied to the turbine by the wind, water, gas, steam - this ensures that the grid is kept at 50Hz. Tollerances are on the grid of +/- 0.5Hz - to ensure the safety of electrical equipment.
This sounds very easy - but it must be remembered that the drag on the turbine is constantly changing as people switch things on and off. The grid ramps up and down once a day as everyone wakes up.
The power applied to the turbines must also ramp up and down once a day at the same time as the electrical demand.
Of course occasionally someone in eastenders gets shot, or we loose a football match - and a few thousand kettles are switched on. The power required when these grid surges happen can be huge:
These surges also always come very rapidly.
Now, when these surges (or other events happen) the national grid calls for more energy - yes, partly from stored water resevoirs, but in the first instance from fossil.
Coal power stations (along with gas) have to be able to increase their demand by 10% within 10s and hold it for half an hour:
...and that's the rub - as more renewables come onto the grid this instability is going to increase. Renewables and nuclear can't load balance in this way - they just run - it's not possible to get the wind to blow a bit faster just because a football match is on.
This is one of the reasons why we will keep fossil (such as coal) on the grid.
Our grid is alternating current, with a frequency of 50Hz. This is done as it then becomes very easy to step up and down the voltages to transmit it accross the country at high efficiencies.
The easiest way of keeping the grid at 50Hz is to turn over a turbine 50 times a second. Ofcourse the turbine can be powered in many different ways - by wind, water, gas or steam.
The drag on the turbine from the generator must equal the power being applied to the turbine by the wind, water, gas, steam - this ensures that the grid is kept at 50Hz. Tollerances are on the grid of +/- 0.5Hz - to ensure the safety of electrical equipment.
This sounds very easy - but it must be remembered that the drag on the turbine is constantly changing as people switch things on and off. The grid ramps up and down once a day as everyone wakes up.
The power applied to the turbines must also ramp up and down once a day at the same time as the electrical demand.
Of course occasionally someone in eastenders gets shot, or we loose a football match - and a few thousand kettles are switched on. The power required when these grid surges happen can be huge:
These surges also always come very rapidly.
Now, when these surges (or other events happen) the national grid calls for more energy - yes, partly from stored water resevoirs, but in the first instance from fossil.
Coal power stations (along with gas) have to be able to increase their demand by 10% within 10s and hold it for half an hour:
...and that's the rub - as more renewables come onto the grid this instability is going to increase. Renewables and nuclear can't load balance in this way - they just run - it's not possible to get the wind to blow a bit faster just because a football match is on.
This is one of the reasons why we will keep fossil (such as coal) on the grid.
Tuesday, December 9, 2008
Kingsnorth shutdown
On the 28th November someone managed to enter Eon's Kingsnorth power station, and switch off one of it's four turbines.
Not only is that pretty incredible, but it's also pretty crazy.
A few thoughts:
1) The complexity of the operation means that it was an inside job. No question. You don't climb an electric fence without first knowing that it's switched off. You can't find the control panel without first knowing where it is and how to unlock the box which (I'm assuming) contains it.
2) Where does all the steam go? These turbines are operating with steam pouring into them with huge temperatures and pressures. I would guess the only way to shut them down (without turning the boiler off) would be to vent the steam somewhere else - presumably outside. I'm assuming the steam went down a designated run-off to an emergency vent in a restricted area, but if anyone had been near that vent they would have been killed. End of. It's a testament to safety at Kingsnorth that this didn't happen.
3) On the 10-17th November the UK would have only had 1GW of spare electricity before many people would have suffered blackouts (this took out 0.5GW). This shut-down took place on the 28th November, close enough to this date to concern me about how much spare generating plant was available.
The irony is that it is the other coal and gas fired power stations which would have borne the brunt of the blip in the grid caused by this trip - so by tripping Kingsnorth the protester has increased UK CO2 emissions.
Ho hum.
Not only is that pretty incredible, but it's also pretty crazy.
A few thoughts:
1) The complexity of the operation means that it was an inside job. No question. You don't climb an electric fence without first knowing that it's switched off. You can't find the control panel without first knowing where it is and how to unlock the box which (I'm assuming) contains it.
2) Where does all the steam go? These turbines are operating with steam pouring into them with huge temperatures and pressures. I would guess the only way to shut them down (without turning the boiler off) would be to vent the steam somewhere else - presumably outside. I'm assuming the steam went down a designated run-off to an emergency vent in a restricted area, but if anyone had been near that vent they would have been killed. End of. It's a testament to safety at Kingsnorth that this didn't happen.
3) On the 10-17th November the UK would have only had 1GW of spare electricity before many people would have suffered blackouts (this took out 0.5GW). This shut-down took place on the 28th November, close enough to this date to concern me about how much spare generating plant was available.
The irony is that it is the other coal and gas fired power stations which would have borne the brunt of the blip in the grid caused by this trip - so by tripping Kingsnorth the protester has increased UK CO2 emissions.
Ho hum.
Thursday, July 24, 2008
Grid connections
You can't generate electricity unless you can plug your powerstation into the same bit of wire as your customers - that way they can absorb the energy that you're pumping out and your power station won't break.
The problem is that, in this country, there have been quotes of a 10 year lag in requesting, and being served by, a grid connection.
The trouble is that, by their nature, most renewable energy sources are miles away from the nearest bit of the grid that can carry the vast amount of power they are generating. This is particularly the case in scotland, where the energy has to be shipped down to london.
Additionally the grid has to be routed through areas of outstanding natural beauty, which requires planning permission (etc. etc. etc.).
As such getting grid connections to renewables can be very time consuming and very expensive.
Coupled with the looming energy gap it therefore makes sense not to always give priority to renewables for their grid connection - something that the EU would like to see. Conventional (coal and gas) power stations tend to be closer to the consumers, and traditionally stronger sections of the grid (where their power can easily be absoped and fed to consumers).
The government is doing the right thing - whilst there is much essential work to be done to connect in the renewables we don't want to put all of our eggs in one basket.
The problem is that, in this country, there have been quotes of a 10 year lag in requesting, and being served by, a grid connection.
The trouble is that, by their nature, most renewable energy sources are miles away from the nearest bit of the grid that can carry the vast amount of power they are generating. This is particularly the case in scotland, where the energy has to be shipped down to london.
Additionally the grid has to be routed through areas of outstanding natural beauty, which requires planning permission (etc. etc. etc.).
As such getting grid connections to renewables can be very time consuming and very expensive.
Coupled with the looming energy gap it therefore makes sense not to always give priority to renewables for their grid connection - something that the EU would like to see. Conventional (coal and gas) power stations tend to be closer to the consumers, and traditionally stronger sections of the grid (where their power can easily be absoped and fed to consumers).
The government is doing the right thing - whilst there is much essential work to be done to connect in the renewables we don't want to put all of our eggs in one basket.
Friday, July 11, 2008
Profit
What is role of private enterprise in keeping the lights turned on? Is it really their job, or is it the role of government.
Take the view, with Russia having all the gas (and having to pipe it a long way to get to us), that we don't want to rely overly heavily on gas power stations.
Think about our inability to store electricity (with more than a 2% round trip efficiency offered by pump storage) and you start looking at building coal power stations, the only remaining type of power station where the output can be changed on demand, to help smooth out renewables output and keep the lights on.
What if the government then insisted that all new coal stations were all "capture ready" (i.e. able to be retro fitted with CCS at minimum cost), or even that they were built with CCS technology.
What would industry do - would they build the CCS coal plant knowing it wasn't going to be that profitable, or would they build more and more gas plants - where they could use their money to make more profit than the profit they would make with the coal power stations.
Somehow I'm worried that they would choose gas, taking the view that its down to government, not industry, to keep the lights on.
Take the view, with Russia having all the gas (and having to pipe it a long way to get to us), that we don't want to rely overly heavily on gas power stations.
Think about our inability to store electricity (with more than a 2% round trip efficiency offered by pump storage) and you start looking at building coal power stations, the only remaining type of power station where the output can be changed on demand, to help smooth out renewables output and keep the lights on.
What if the government then insisted that all new coal stations were all "capture ready" (i.e. able to be retro fitted with CCS at minimum cost), or even that they were built with CCS technology.
What would industry do - would they build the CCS coal plant knowing it wasn't going to be that profitable, or would they build more and more gas plants - where they could use their money to make more profit than the profit they would make with the coal power stations.
Somehow I'm worried that they would choose gas, taking the view that its down to government, not industry, to keep the lights on.
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