OT: Underground utilities

It is much more expensive to bury a super-grid cable than than to install an overhead line.

I can't see that putting water pipes on pylons would be a good idea.

Yes, everyone knows that water conducts electricity, provided it isn't too pure.

They wouldn't need to expand the National Grid if they built all the wind and solar farms in centralised locations.

Why do people object to pylons disfiguring the environment when they seem to be very happy with ugly wind generators doing the same.

Not all of us are even remotely happy with the latter.

In any case they'd work just as well for their main uses, obtaining subsidies and payments for not operating, with just a low capacity grid connection for telemetry purposes. The amount of power they can intermittently generate is not that important.

Yes, we know, they keep telling us that. But is it more expensive than laying a pipeline underground?

Isn't there a German city where all utilities run in pipes above ground ?

The point is that that all happens outside the towns where all the Green voters live. Imagine if Hampstead Heath was covered in turbines taller than the Shard with pylons looping away to Peckham etc.

All going whup whup whump at 40dB above traffic nmise, by day, and impossibly loud by night

Maybe. Maybe not.

'Renewables' are a bloody waste of time and money. And about as eco friendly as the city of Brighton.

I get an attack of RenewableRage™ every time see a solar panel or a windmill...

Unfortunately in a decent wind the amount of power they can generate is extremely important, as it cuts into the profits of gas power stations and renders the whole grid extremely unstable

The net result is massively increased cost and massively reduced reliability

Yes.

A pipe - a simple plastic pipe for water sewage or gas, operates at relatively low pressure and is very cheap to manufacture

Three phase lines of 400kV are at high [electrical] pressure, and very expensive to manufacture, and have issues with inevitable capacitance to ground that overheads do not. Which is why we use HV DC on undersea links .

As it stands 33kV, 11kV and 400VAC three phase are all reasonably possible to put underground for urban distribution, but real distribution at 100kV AC+ is not . You need to go to DC, with the attendant expense of inverters and extremely massive cables.

That is not to say that it wont happen, but it is very expensive.

AIUI it's because air is a much better dielectric than whatever they wrap underground cables in. Two problems: risk of insulation breakdown and reactive losses because the cable is a giant capacitor to earth.

Air gaps measured in metres are just a better medium for dealing with those things than centimetres of sheathing.

Theo

In a nutshell this is indeed the case , but it is the *implications* of this that lead to the expense.

The cost to underground just a kilometre of 11KV three phase to get rid of a line over my garden was £30,000. Of which I paid nearly £20,000

(the rise in value of a property that doesn't have a cable over it's garden and house was at least 10 times that...)

The cable is/was about 50cm in diameter, per phase.

The digging was ultimately no worse than laying the new optical fibres was, but the cable was a lot more complex than stranded steel with copper wound round it.

I imagine it's both things. One is digging any kind of hole costs a lot more per metre than stringing up a wire and some lightweight-frame towers, although this kind of cable will need a bigger and deeper hole than laying optical fibres. But the other is the kind of HV power cable needed for burial is a lot more expensive than the cable you'd string between pylons.

Theo

Anglian are saying £1,000,000 per km for a 1m diameter pipe (ish). Overhead HV seems to be around the same (for a few GW).

Add salt to the water supply and use it to carry power? It's an interesting approach. Now we need a method of removing both salt and power before it reaches the domestic user.

Do they? Really? Strange.