h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: The Electric Mountain, Dinorwig UK - A958818
Author: Dolt - WHY am I reading about psychoanalysis, semiotics and structuralism? Just WHY?!? - U195965

This one fell out of Peer Review into the Flea Market a few months ago. It was scouted back then, so for the moment I've left it virtually unchanged and just modified the section on "Why".

The original article is A754698.

Looks good - I'll take a detailed look and be back in a while...

I agree - looks good.

Surely there must be some kind of statement about the futility of all this work to drop water down a hill and then pump it back up again - generating electricity so you can use electricity pumping it back later.

Maybe its just me

It does seem a bit futile, doesn't it? The sensible thing to do would be to turn off the big generators for the night when they're not needed. The problem with that is, the big generating stations fall to pieces more quickly if they keep being turned on and off every night.

And I wish could think of a way to rephrase that last sentence to avoid the obvious innuendo

Looked Good back then, still looking good right now. Just relax and wait...

HELL

Yup, still looking good. Is there a missing space when you say 'powerstations' towards the bottom of the first paragraph?

The only things I'd suggest are:
1) a link to the relevant page of the electric company's website:
http://www.fhc.co.uk/DIN.htm

and

2) possibly a little change of the title location-wise - I'm not certain of the precise classification that would be applied, but I'd recommend either "The Electric Mountain, Dinorwig, Gwynedd, Wales, UK" or just "The Electric Mountain, Dinorwig, Gwynedd, Wales".

Unless, of course, the county of Gwynedd has been replaced by something else under the last round of local government reorganisation...

As you've said, you can't just turn a traditional power station on or off...

Coal fired powerstations take days to shut down and re-start, and as for nuclear power stations... shut those down the wrong way and you get Chernobyl

Nice entry by the way!

"Is there a missing space when you say 'powerstations'..." Er, no? Not any more, at least

Extra space deleted, link added.

Re. the title, the example given in EditedGuide-Style suggests dropping "Wales" altogether, giving something along the lines of:

The Electric Mountain: Dinorwig, Gwynedd, UK OR

Dinorwig: The Electric Mountain, Gwynedd, UK

Whaddya think?

The brainwashed engineer in me would like to point out that the Chernobyl disaster was partly due to a reactor design peculiar to the USSR, and should be impossible to duplicate in any other reactor design (the cynic in me points out that no-one's ever explained to me the exact design differences that make such an incident impossible in British or American reactors).

Of course, the Chernobyl disaster was also due to rank stupidity on the part of the operators, which is much more worrying.

That's got to be one definite advantage of a hydroelectric plant... someone pushes the wrong button and a few million fish end up out of water...

With a nuclear plant someone presses the button and the same fish grow to 8 feet tall with legs and come looking for the operator who made the mistake...

Good one Whisky, like it!

The Electric Mountain: Dinorwig, Gwynedd, UK sounds good to me!

OK, title changed. I've also dropped the first section heading, which I thought unnecessary.

Good move - I thought of suggesting it but didn't want to seem too picky!

Dolt, I note you've changed the section on Why? but I think there's a problem there.

But first, I'd like to point out the incorrect use of 'majority' here:
>In the UK, the majority of electrical energy is supplied by large fossil fuel power plants, or by nuclear power stations.

-- 'The majority of' can only be used with a countable noun, which 'electrical energy' is not. Also, majority can mean anything over 50%, and I think you mean rather more than that. So, better would be 'most of the electrical energy'.

Also, while we're about it:
>The demand for electricity varies through the day - far less power is used during the night hours as during the day.
-- should be 'than during the day'.

>While it is possible to match this variation in demand by varying the output of the large power plants, to do so is uneconomical. It would be much better if the excess electricity generated at night could somehow be stored for use during the day.

The situation is rather more complex than this suggests. There are two things you can do:
a) you can reduce the output of the large generators;
b) you can keep the big ones running and switch off the smaller ones.
You've got coal, oil, gas and nuclear powered stations (and hydro in Scotland). You've got large generators and smaller ones. You've got newer ones and older ones. You can also import and export electricity.

There's a tremendous variation in efficiency between different power stations. You have to do a linear optimization process to determine the best mix. The ideal, whenever you don't need everything running at full blast (whatever the time of day or season of the year), is to have as much as possible running as closely as possible to peak efficiency - ie the most efficient load factor for each plant.

The main reason that electricity is cheaper to _produce_ at night is that you can cut out the older, less efficient plant. But producing the stuff is no good unless you can distribute it, and the economics of electricity distribution are not the same as those of production or generation. Distribution as well as generation involves losses of different kinds, and the degree of loss is different for different load factors.

It all gets very complicated and I'm sure this would be outwith the scope of the entry (unless you think otherwise, of course!) It's probably safer just to say that electricity is cheaper to produce at night, for various complex reasons, and leave it at that.

The other point is that, of course, it isn't the electricity that is being stored at Dinorwig. Electricity generated during the day is not stored during the night, it's either consumed (ie sold) or wasted, and then replaced during the night.

I can't remember now, but I think I made similar comments when this entry came up some time ago. It was looking pretty good then, and it is now, I think, apart from these few but important points.



Bels

to deal with your query about reactor design first, in the chernobyl plant, the damping control rods had to be individually inserted. this meant that once things got too far out of control, you didn't have time to put enough rods back in.

in just about every other design, the rods are mounted vertically, and in the event of an emergency they are let loose (in various different ways depending on design) and are then gravity fed back into the core very fast.

as the default is a shutdown mode, and it fails safe to this, most reactors shouldn't be able to blow up.

on the other point of generation, it is not generated cheaper at night, it is priced cheaper at night, because of the lower demand. however most of the efficient designs for large scale generators can't actually be turned off at all. What they do is run the generator at minimum load during the slack time and then turn it up to full blast during that silly peak just after the soap finishes and everyone turns their kettle on.

it is at this point that the stored power is most useful.

It is mainly a problem because of the current dominance of the big power station in the middle of nowhere model of generation. As you get more renewables being brought into the mix you will get a more distributed generation model, and much more flexibility in the control system.

Generated cheaper / priced cheaper.
That's a good point - are base load stations generating more cheaply than peak-load ones? I know that the distributors buy what they want from those operating companies who offer it cheapest, but station economics probably dictate that nukes and coal-fired stations have to keep going, and anything they can get for the electricity is worth having.

Is it worth pointing out that something along these lines is probably needed to make much more use of renewables (wind, wave, solar etc.) which are not directly controllable, and still be able to balance suppy and demand?

Gilgamesh, the most efficient load factor varies from one station to another depending on various factors, but for most it's going to be in the 70%-85% region.

xyroth -
>on the other point of generation, it is not generated cheaper at night, it is priced cheaper at night, because of the lower demand

It would make no sense to reduce the night price if you couldn't produce it cheaper at night. You also have to look at what sort of load you might be shifting from day to night. In the UK, for example, a common domestic use of night rate is for storage heaters. But the night discount for these has been reducing over the years, as has the definition of 'night', which is now down from ten or even eleven hours to a mere seven hours in most cases. The reason is that this type of load is not peaky - the heaters are turned on by a time-switch and stay on all night. The most expensive loads to service are those that peak at times of system maximum demand, which apart from public holidays means mostly the large peaky industrial loads in the middle of the day, in winter. Steel mills, oil refineries, large chemical works, etc. These are the loads you need to displace as much as possible, and that is done by premium pricing leading to techniques such as dual firing, automated maximum demand control, self-generation and so on.

Egad, sirs, you're making my head hurt

So Dinorwig was built to act as a peaking generator, to generate electricity when demand was high during the daytime. It can then draw power from the grid when demand is low to recharge the reservoir. Since recharging the reservoir uses more electricity than the station can generate, the recharging must be done at night when (for whatever reasons that are definitely outside the scope of this article) electricity is cheaper. The station is thus able to run without making a financial loss.

Does Dinorwig serve any purpose that is cannot also be served by modern gas turbines, which can also be used effectively as peaking units? If gas had been available as a fuel back in the seventies and eighties, would Dinorwig have even been built?

I think the theory behind Dinorwig is more along the lines of it being a gigantic rechargeable battery...

Due to the methods we use to generate electricity there is a lot of spare capacity at night, ok we could just turn off the generators, but the power sources behind them would still be running, so there's no real point.
So in effect, the battery is being charged during the night by 'free electricity', ready for use when needed during the day.

If Dinorwig were to be replaced by Gas Turbines then those turbines would use fuel, costing money, and we'd still have the problem of 'spare electricity' at night.

Ok, the station is not 100% efficient, it takes more electricity to charge the battery than it releases, but there again, the electricity is, to all intents and purposes, going to waste at night, so whatever percentage can be stored for use at peak times is an advantage.

some night time loads are not peaky, like those storage heaters, but that isn't why the pricing is different.

the national grid is obliged to buy electricity from anyone who wants to sell it, and there is a statutory minimum they must pay. this is irrelevant of when the seller happens to generate it.

This was put into place so that they couldn't buy electric really cheap from local suppliers at night, and force the large boiler type stations into having to shut down (because the design never considered this), and if you try and do a non-planned and quick shutdown the boiler tends to crack. this means that you have a minimum amount being generated at a fixed price, which matches the inflexible supply. so what happens is they turn their systems down to minimum load, and sell the rest to the national grid at the legally mandated price.

as mentioned by someone else, if this wasn't used, it would have to be wasted.

on a seperate point, renewables use an entirely different model of generation, distribution and storage. they work on a supply side model, where you have to generate when the energy is there, and you balance this out by having geographical dispersion and multiple types of generators with different characteristics.

for example:

tidal gives you peaks either twice a day or four times a day depending on the type of generator, but when moves with the tide times

solar gives you daytime supply, but varies with cloud cover and time of year.

wind power typically gives you more power when there is more wind, but varies by location.

otec (Ocean Thermal Energy Conversion) gives you a fairly constant supply, but is only available on the coast and near hot or cold streams.

biomass is more like conventional generation, but is designed to be demand driven, so it is much better as an intermittent demand supply.

biogas is also very usefull, and could be plugged into the standard gas supply tomorrow.

and there are other sources, but alternative energy is about a diversity of supply, combined with energy efficient usage.