'Is global warming happening?' Poll discussion/results

ZTD

sharkmark wrote: »

If I was a cynic I would say that you work for an oil company as this is your first post

Hey! That's a new one! Still an ad hominem attack, but a different flavour.

sharkmark wrote: »

- however I shall not accuse you of this as it's probably not true...when the floods of Herefordshire come knocking at your door I'd be interested to see if you change your attitude....?

Well the recent floods are an interesting thing. For example this:


Why did they build it there - up on top of the hill? Why did they not build it on the flood plain like the modern housing estates? After with it being built in the 1100's, they must have had some inkling that this sort of thing would happen. They must have learned their lessons from "Ye Olde Globale Warminge".

Or just perhaps they knew why flood plains are called "Flood Plains". Unlike "Meadow View" or other crap housing estate names - it's a warning, not an advert.

ZTD

magyar wrote: »

ZTD, I think we're talking at cross purposes here.

The 15% overcapacity is the amount of capacity available on the network. The amount that's actually operating is what will vary between winter and summer (for obvious reasons).

No plant is 100% reliable, so you always need back-up for it. The operating overcapacity is nothing to do with demand forecasting, it's to do with the largest plant that might drop out. Until we end up developing wind farms on the scale of large power stations (and some proposed offshore ones are that size) then this will not change.

Yes, no plant is 100% reliable, and yes, we might lose Drax or something similar. But, and this is the big but - losing powerstations is a statistically independent event. If we lose Drax, the chances of losing Sizewell B are no different to what they were before, and indeed the chances of losing both are statistically tiny (the product).

Wind power is different. If one turbine doesn't turn because there's no wind - the chances are the one next to it isn't turning either. It is quite possible for the whole country to have no wind (big high-pressure over the top).

So it's not the fact that a farm may be "out" that's the problem - you're right that there's spare capacity for individual failures. The problems is that they *all* might be out.

Big high pressure over the whole country - very hot - fans&air-conditioning going - high load on the grid - no turbines going. You're heading towards your capacity, and 20% (target) of your generating capacity is down.

That's where you need your non-green backup. Even then - there can be no failures.

The other problem also being high wind - how well they cope with that, before needing to be "feathered". But I can't find much detail on that.

magyar

ZTD wrote: »

The other problem also being high wind - how well they cope with that, before needing to be "feathered". But I can't find much detail on that.

Working from back to front, the turbines pitch the blades to control power up to about 25m/s wind speed. Above that, they apply brakes. I've never seen a whole site taken out this way, it's usually only a couple of turbines.

Of course you're right, if a high-pressure zone sits on the UK, it would reduce the output dramatically compared to a windy day. But the point is that never happens suddenly. A modern CCGT can go from stationary (not spinning) to full load in under an hour, and forecasting is far more accurate than that (you'd probably have several days warning of that). But that's a worst-case scenario, in practice the winds around the UK are very, very rarely that low.

ZTD

magyar wrote: »

Working from back to front, the turbines pitch the blades to control power up to about 25m/s wind speed. Above that, they apply brakes. I've never seen a whole site taken out this way, it's usually only a couple of turbines.

Remember him?


How many turbines would still generate power through that?

magyar wrote: »

Of course you're right, if a high-pressure zone sits on the UK, it would reduce the output dramatically compared to a windy day. But the point is that never happens suddenly. A modern CCGT can go from stationary (not spinning) to full load in under an hour, and forecasting is far more accurate than that (you'd probably have several days warning of that).

So maybe you have several days warning. But the question is - what are you going to do about it? You either have the spare capacity to cope or you don't. You've either built that non-green powerstation a decade ago, or you haven't.

And it's going to last for days. Obviously with no wind to send it anywhere, it's just going to sit there...

magyar wrote: »

But that's a worst-case scenario, in practice the winds around the UK are very, very rarely that low.

It's not a worst case scenario. In a year with better weather, it is actually reasonably likely to happen.

A worst case scenario is that happening co-incident with a failure somewhere.

magyar

ZTD wrote: »

Remember him?


How many turbines would still generate power through that?

Virtually all off of them. The wind speed above which they'd have to shut down is a sustained wind of over 70mph, so again the chances of it happening simulataneously across the country are inconceivable.

ZTD wrote: »

So maybe you have several days warning. But the question is - what are you going to do about it? You either have the spare capacity to cope or you don't. You've either built that non-green powerstation a decade ago, or you haven't.

Where did I say we wouldn't have conventional power stations? In fact, quite the opposite, I pointed out we still need a mix of gas, coal and nuclear stations.

envirobabe

Semantics and shooting the messenger are all good fun, but where is the evidence base for all your wild GW theories? All I see are a bunch of loosely related facts, many of questionable scientific validity, stuck together to present a theory. When those involved rely on the theory for their income, fame and kudos, and those who disagree are sidelined, my bs detector is activated. In 10 years time we will all wonder at how gullible many were.

rumfield

It wasn't long ago oxen were roasted on the frozen Thames. It's warmed up a lot since those days. Was man responsible? He had no cars or aeroplanes, he was sparser on the ground and the rain forests were in tact. No, man is not to blame - it is one of many natural cycles - but it's being hyped-up for political ends.
Even Bush has twigged now - he was a bit slow (really?) to get on the 'band wagon' but Tony finally put him right.
Rumfield

ZTD

magyar wrote: »

Virtually all off of them. The wind speed above which they'd have to shut down is a sustained wind of over 70mph, so again the chances of it happening simulataneously across the country are inconceivable.

It doesn't need to happen all across the country.

Firstly it only needs to happen to a significant cluster of your turbine base - which are not evenly spread throughout the country. I can't remember the Kensington and Chelsea wind farm for example.

Also sustained wind of over 70mph is not a super rare event for turbine farms as it is for London (for example), because they tend to build the farms in exposed areas where it's rather windy - for some unknown reason...

Though I'd be interested to know what happens when the wind gusts to silly speeds? Do they shut them down then? What's the maximum gust they can tolerate?

magyar wrote: »

Where did I say we wouldn't have conventional power stations? In fact, quite the opposite, I pointed out we still need a mix of gas, coal and nuclear stations.

My point was that for ever KWh of wind turbine, you'd need a KWh of coal/gas/nuclear - for those times when the wind didn't behave. You could get away with making only a fraction of the provision (maybe 80%) provided you were willing to run the risk of running out, and the country going dark - or at least dim.

Does that mean you agree with that?

magyar

ZTD wrote: »

It doesn't need to happen all across the country.

Firstly it only needs to happen to a significant cluster of your turbine base - which are not evenly spread throughout the country. I can't remember the Kensington and Chelsea wind farm for example.

No, but there are wind farrms in Kent, Cornwall, East Anglia, Yorkshire, Northumberland, all corners of Scotland, Cumbria, Wales and Cornwall (amongst others). Add to that the to get past about 10% coverage, most of the development would be offshore, and you very rarely get no winds offshore (if only down to sea breezes). Plus, offshore increases the spread across the country even further.

ZTD wrote: »

Also sustained wind of over 70mph is not a super rare event for turbine farms as it is for London (for example), because they tend to build the farms in exposed areas where it's rather windy - for some unknown reason...

No, it really is rare. Over the winter for example, a (windy) site in Scotland - I'm using specific data for a site near Inverness - only had a few half-hour periods where any turbines were down due to high winds.

ZTD wrote: »

Though I'd be interested to know what happens when the wind gusts to silly speeds? Do they shut them down then? What's the maximum gust they can tolerate?

I don't actually know that answer, but I'll find out if you're interested.

ZTD wrote: »

My point was that for ever KWh of wind turbine, you'd need a KWh of coal/gas/nuclear - for those times when the wind didn't behave. You could get away with making only a fraction of the provision (maybe 80%) provided you were willing to run the risk of running out, and the country going dark - or at least dim.

Does that mean you agree with that?

I assume you mean kW and not kWh (i.e. capacity, not generation). I would guestimate you needed about an extra 25-50% (per MW renewables installed, depending on the actual percentage installed). The 'no wind' events would primarily happen in the summer (and I still maintain they'd be very, very rare indeed) when of course you have loads of spare capacity anyway.

It's an interesting point that people - and I'm not including you here ZTD - often seem to forget we don't have CEGB planning all our power systems for us! But it means you need to think differently.

As to future capacity, I'm far more worried about the fact we will run out of existing conventional plant soon; most of our power stations are nearing end of life. Wind is probably a short-term measure; development of tidal and wave power will be Britain's best renewables answer, long-term.

ZTD

magyar wrote: »

No, but there are wind farrms in Kent, Cornwall, East Anglia, Yorkshire, Northumberland, all corners of Scotland, Cumbria, Wales and Cornwall (amongst others). Add to that the to get past about 10% coverage, most of the development would be offshore, and you very rarely get no winds offshore (if only down to sea breezes). Plus, offshore increases the spread across the country even further.

Yes, but I was talking more from the "high winds stop generation" aspect, rather than no wind at all. Wind power seem to be in rather a cleft stick - too little wind and it stops working, and too much and it stops working.

Probably too much is better as it brings down powerlines, so reducing demand.

magyar wrote: »

I don't actually know that answer, but I'll find out if you're interested.

I am interested in that. The definition of "sustained speed of Xmph" I saw was "10 minutes at Xmph or above". I would expect from that, 9 minutes of 70mph would just be a "gust" (or is there a "middle" term?). But I would also expect those 9 minutes would be rather demanding of the blades.

magyar wrote: »

I assume you mean kW and not kWh (i.e. capacity, not generation).

Well no - but the difference is thought provoking in itself. The turbines may be rated at X kW, but over an averaged hour you'd only get nX kWh (average) out of them (where n<1), depending on how good the site was. I assume you'd plan for the nX kWh.

magyar wrote: »

I would guestimate you needed about an extra 25-50% (per MW renewables installed, depending on the actual percentage installed). The 'no wind' events would primarily happen in the summer (and I still maintain they'd be very, very rare indeed) when of course you have loads of spare capacity anyway.

If you have 20% of your capacity wind power (EU target), then out of your 115% capacity only 92% would be working on a still day. Assuming no failures. Of course you may probably get a certain percentage of your wind-turbines working, (assuming a still but not a "no wind" day) but even they would only be operating very marginally.

You get high pressure in winter too. Leads to clear skies and extreme cold. Which then leads to high demand, and no power lines blowing down to ease the load.

Taking your figures from above, for every MWh wind, you'd need 250KWh non-green, which then would need 50KWh green (EU target), which (assuming wind) would need 10KWh non-green, which would then need...

Seems a bit recursive to me... But may be an opportunity to fudge/mix up capacity and generation definitions.

magyar wrote: »

It's an interesting point that people - and I'm not including you here ZTD - often seem to forget we don't have CEGB planning all our power systems for us! But it means you need to think differently.

As to future capacity, I'm far more worried about the fact we will run out of existing conventional plant soon; most of our power stations are nearing end of life. Wind is probably a short-term measure; development of tidal and wave power will be Britain's best renewables answer, long-term.

Tidal will be best because it's reliable. Wave is not so good. Mostly because it's wind power under a different name.

It's looking like the big-N is going to be the only game in town if you want non-carbon - at least for the medium term and shorter. But coal is going to be king at least for the foreseeable future.