"A 385 km subsea power cable, billed as one of the world's largest, has come ashore in the UK this week"
"The cable reached shore at Ardneil Bay in North Ayrshire, Scotland as part of the £1bn ($1.25bn) Western Link HVDC project, which aims to transfer renewable power from Scotland's transmission network to consumption centres in England and Wales"
With the closure of Longannet and the forthcoming closure of Scottish nukes, I wonder if the current flow is going to stay one-way.
The project website says it's a 2.2GW capacity cable, which should draw down a lot more of the surplus wind power from Scotland, and save National Grid (and us) from paying the wind generators not to generate when there's more than the existing England - Scotland links can carry, so bringing the maximum capacity to 5.5GW, up from the 3.3GW estimated from the Mearns link you give.
Hmm... in 2015 we paid £90 million in constraint payments to UK wind generators not to generate (Figure 7 in Mearns' blog on the topic:
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). The Western Link is going to cost £1 billion. Plotting Mearns' data for 2012 - 2015, and assuming a quadratic increase in payments year by year (which may not be the case), means that we will have paid out a little over £1 billion in total in constraint payments by 2019. Even if we just continue to pay constraints at about £100 million per year, we will have paid for the Link in ten years.
On that basis I would say the Link is value for money.
There is 3.5GW of England & Wales to Scottish border transfer, this is not a single interconnector and is the current combined five feeder (4 x 400kV & 1 x
132kV) thermal limit, that is public knowledge to anyone who really needs to know.
This limit will increase to 4.4GW with current and ongoing transmission upgrades onshore, then to 6.6GW with the Western HVDC Link and ultimately to around 8GW by 2025 with further onshore transmission upgrades and the Eastern HVDC Link.
Interesting. Thanks. OOI does the 4 x 400kV feeder constitute four separate power lines, with pylons etc, or is it a single set of pylons strung with groups of four cables separated by spacers as in this pic
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? And what do they do to upgrade such a line; more cables, thicker cables or what?
That's a 475kV tower, there is 3 phases each side and they run in parallel for resilience. All power lines above 33kV run two parallel supplies but the 33kV and 66V on wooden poles may be separated by ~50 metres.
One pylon like that is two feeders, almost always operating at the same voltage, and if the image title is correct that'll be 400kV as is everything along the south coast.
Some have operated at 400kV on one side and 275kV on the other, but built with
400kV insulators and clearances. That was the case for around 20 years with the pylons strung alongside the A74 / M74 or whatever they are calling the road from Carlisle to Glasgow these days.
Each cluster of four conductors is one phase and historically most 400kV and
275kV lines were strung in that manner. Upgrading can be done with four conductors of a higher specification but since the mid 1990's double and more recently triple conductors can be used. The physical cross sectional area is not necessarily increased so there is the benefit of reduced wind loading with the advantages of significantly higher current ratings.
In my post earlier in this thread, I cast doubt on your suggestion that it would be cheaper to pay them not to generate. If the Eastern link is going to cost the same as the Western link, say another billion, to which is added another great chunk of cash for upgrading the overland links down the middle, then I think you were right!
By such clueless comment one can only assume you know absolutely nothing about resistance, a property that varies depending on the material used for the conductor.
Not all conductors are the same even if they look like that from the ground.
One billion quid for an asset with a 60-75 year life, that can transfer around
650 million quids worth of electricity (assuming £35/MWh) per annum is fantastic value for money if you look at the wider picture.
It very significantly increases grid resilience in a number of areas, all but eliminates constraint payments North of the border, which it should be noted are consistently and significant higher in monetary value across the UK for gas fired generation than they are for 'renewables' and it also enables the future UK-Norway interconnector to operate without constraint.
While the Eastern HVDC link may also be deemed 'expensive' being of a similar cost the onshore transmission system improvements are considerably cheaper as much of the work is simply conductor restringing.
Grid upgrades and expansion are, by their very nature, examples of proper well thought out long term infrastructure thinking, something sadly absent from much of the UK and Europe.
Well let's say at cost of capital 7.5%, lifetime 70 years, O & M 5%, that cable needs to generate £139m a year just to break even.
The opportunity cost is between paying ~£2bn for the renewable electricity because it doesn't cost £35/MWh. Its AT LEAST £100/MWh... plus £139m, to get it to the UK, where it will offset a mere billion of fossil energy that doesn't have to have a grid surcharge slapped on top..
versus paying the ~2bn to not generate the electricity, and not paying the £139m. But instead paying a £650m to get some reliable fossil electricity.
Well its marginally worthwhile, except that of course the electricity is NOT going to fully utilise that grid link is it Only about 20% of the electricity it COULD take WILL be taken because the rest of the time the wi9ndymills aren't spinning.
So that means it has to charge £139m for £200m worth of juice: way more expensive than locally sourced gas
Which is why its cheaper in times of high wind to pay the scottish windfarms (and gas sets) not to generate.
For those wondering why four cables are run with spacers for each "conductor", it is because the peak electric field strength is lower than it would be for a single cable (i.e. a set of four behaves like a "fatter" single conductor). Because of this, the corona losses are lower. It starts to become more of an issue at 400 kV or more. ISTR that long distance lines overseas run at up to 1 MV.
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