Wind turbines get bigger and bigger

[Bob Brown 1Participant @bobbrown1]

You only have to look to France to see a country that has invested heavily in Nuclear with over 75% generated http://www.gridwatch.templar.co.uk/france/

Edited By Bob Brown 1 on 06/04/2018 12:35:30

[BazyleParticipant @bazyle]

On another forum I just learned that some Americans are using corn as central heating fuel. A form of solar capture made possible by high farm subsidies apparently like ethanol production but it just seems wrong. Like the solar farms along the M4 on prime agricultural land which thus also has the best weather conditions for collecting subsidy.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Roger B on 06/04/2018 08:28:53:

…

… but I do like to find the facts not follow the dogma.

Best regards

Roger

But Roger! In an earlier post you treated us to a link to 'American Thinker'. Did you not notice that their material is strong on dogma and weak on facts? I thought the site interesting and thoroughly untrustworthy. Their explanation of what went wrong at Enron is certainly different to the facts as I understand them.

I sympathise with your desire for facts though. It's just that I also think we have be extremely careful selecting them. Even engineers (who should know better) often fall into the trap of cherry picking evidence to suit an emotional opinion. We're all human…

Dave

[MikeParticipant @mike89748]

Duncan: you mention the fact that pylons are ugly, which they are. At my home village on the Moray Firth two cables come ashore – one from the offshore Beatrice wind farm, and the other from wind farms in the northern isles. Before the electricity is fed into the national grid, it makes its first ten miles of its journey as DC through buried cables – apparently because DC does not suffer the same voltage drop as does AC over long distances. I confess to being a complete idiot as far as electricity is concerned, but is this the future of power transmission? The two cables should be operating soon.

[Roger BParticipant @rogerb61624]

Dave, I agree that the American Thinker has it's own agenda, but they will post pictures of abandoned wind turbines which the pro renewables sites tend not to due to their own agendas. You have to gather information wherever possible and try to determine it's validity.

Best regards

Roger

[Jon GibbsParticipant @jongibbs59756]

I think the advantage of the DC cabling onshore is that there is then just one DC/AC inverter needed to synchronize with the national grid rather than one per turbine and it's on-shore for easier maintenance.

I see no reason why DC of the same voltage as AC (RMS) would be more or less efficient to route via cable.

I would assume that each turbine will still generate AC which is then voltage converted and rectified to produce a near constant voltage DC.

[larry PhelanParticipant @larryphelan54019]

On the subject of windmills.pylons.AC,DC,ect , I was led to believe that AC was easier to transmit over long distances than DC and that cables underground suffered from voltage drop.

No doubt there is someone out there who can correct me on this [no sweat,I have been corrected many times before ] I can see that putting them underground would be more expensive,and troublesome,no matter what they are,but why go to the bother of changing from AC to DC and then back again to AC.

As regards the pylons,no-one wants them anywhere near them,but how many of these same people would like to go without their light,heat,TV,electric blankets,ect,ect,and go back to the oil lamp and the candle ? Not too many I suspect. You can,t have your loaf and eat it.

PS Forgot to ask this–can DC be stepped up and down by means of a transformer,like AC,or is this a different matter ?.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by larry Phelan on 06/04/2018 17:33:00:

PS Forgot to ask this–can DC be stepped up and down by means of a transformer,like AC,or is this a different matter ?.

.

Short answer is : No it can't … and the different matter involves first chopping-up the DC to make AC

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Whole bunch of pros and cons for AC and DC. Which is best depends on the circumstances.

It's more efficient to generate AC than DC and AC can be easily transformed up and down to suit the customer. This is important because energy losses are much lower in high voltage systems. It pays big time to increase volts to transfer energy over distance and drop it down to much safer (but wasteful) levels so people can use it without frying themselves. Powering your telly off 33,000Vac would be quite exciting.

AC has several disadvantages; electronics, electroplating, and many other processes need DC. Before inverters almost all high power variable speed motor (trains and lifts etc) had to be DC because it could be controlled. Most seriously, the current reversals in an AC cable are resisted by the wire, causing energy to leak and the flow to be impeded. The effect is small at 50Hz but it causes serious losses over long distances. One way of reducing the effect is to space the cables further apart, which is best done by hanging the wires off pylons. Another plus for pylons is that it's only necessary to insulate the cables at suspension points and air helps keep the wires cool. A buried cable brings the conductors very close together so their impedance rises, they have to be very well insulated throughout, and they're difficult to keep cool, ie less power can be transferred. On the other hand they're protected from the weather and they don't fall on people.

AC Cable losses become serious in overhead lines at about 500 miles. Underground AC cables become inefficient over much smaller distances, say 10 miles. Beyond those distances it rapidly becomes more efficient to convert the AC to extremely high voltage DC. DC current flows steadily in one direction and there are no reversals to impede the flow. It's not easy though: high voltage AC/DC conversions require techniques far more expensive than a simple robust transformer. For that reason you tend to find high voltage DC transmission used only for very long overland runs and for underwater lines such as the power feed between England and France.

Dave

[not done it yetParticipant @notdoneityet]

The high voltage transmission cables (HVTC) are all DC. One can transmit power better for any given voltage using DC because the voltage remains constant, as well as the current. To transmit the same power by AC single phase for a start the peak voltage will be 1.414 times that of the DC and the current would need to peak higher by a similar amount. This is to counteract the times when the voltage is zero for the AC.

Consequently, the cable insulation for 400MV DC equivalent for a single phase AC would need to withstand 565 MV. Not an inconsiderable requirement. Would need to work out I^2 R losses, but should be equivalent, although the heat generated within a much more heavily insulated cable would downrate that cable. AC grid power is normally transmitted via 3 phase, but the same basic principles apply. Our Natinal grid, like others, uses uninsulated conductors – not very good for underground or underwater cables! – to keep losses due to temperature rise to a minimum.

Further problems would arise with synchronising the frequency between several different grids.

Edited: SOD started keying earlier than me – or does it more quickly!

Edited By not done it yet on 06/04/2018 18:42:10

[MikeParticipant @mike89748]

Thanks, SillyoldDuffer and not done it yet – I can understand that, although my knowledge of electricity is still abysmal. My late father, who spent his working lifetime in the electricity supply industry, must turn in his grave when I try to express opinions on the subject!

Edited By Mike on 06/04/2018 18:41:38

[Barnaby WildeParticipant @barnabywilde70941]

What really P's me off about wind turbines . . . Is that it's easy to see that it's all about £money & nothing whatsoever to do with 'saving the planet'.

That is, it's easy to see unless :

(1) You the one benefiting from the £subsidies.

(2) You not the one paying for those £subsidies.

(3) You caught the 'green' illness.

Will it ever be possible to get a bunch of people, with no ulterior motives, together, to work out the best way to convert energy into a convenient form?

[richardandtracyParticipant @richardandtracy]

With subsidy rates tumbling, it is no-longer about the subsidies. If you are stupid enough to rely on subsidies, you are basing a business plan on the word of a politician. Politician's words are worth the water they are written on. If there is a subsidy it needs to be the icing on the cake, with a sound business underneath. Subsidies can be withdrawn at a moment's notice – as they were for solar plants in the UK. The withdrawal of subsidies has not stopped solar farms, because they are economically viable without subsidies. There is a community funded one up the road from me, started after subsidy withdrawal, and most local residents are now getting cheaper power because of it, and the farm is still making money.

If it's all about making money, where is the harm in it. It's the way capitalism incentivises people. But relying on subsidies is the best way of destroying your business because it puts your business in the hands of those who have nothing to lose when the political wind changes.

Regards

Richard

[Martin DowingParticipant @martindowing58466]

Posted by richardandtracy on 06/04/2018 21:41:42:

With subsidy rates tumbling, it is no-longer about the subsidies. If you are stupid enough to rely on subsidies, you are basing a business plan on the word of a politician. Politician's words are worth the water they are written on. If there is a subsidy it needs to be the icing on the cake, with a sound business underneath. Subsidies can be withdrawn at a moment's notice – as they were for solar plants in the UK. The withdrawal of subsidies has not stopped solar farms, because they are economically viable without subsidies. There is a community funded one up the road from me, started after subsidy withdrawal, and most local residents are now getting cheaper power because of it, and the farm is still making money.

If it's all about making money, where is the harm in it. It's the way capitalism incentivises people. But relying on subsidies is the best way of destroying your business because it puts your business in the hands of those who have nothing to lose when the political wind changes.

Regards

Richard

 

Richard, I disagree with you. You are writting how things *should* work, unfortunately they are working entirely different and we are no longer living in capitalism.

Subsidies are extremely important for businesses now because they are one of last remaining lifelines for them.

So lets beging with our Western banking sector.

Do you really believe that it would still exist in current form without *subsidies* from taxpayer following Lehmann Brothers collapse?

Now look on all these European projects. There are subsidies, EU funds everywhere. Any green, less green and not green at all but politically well connected entity will get EU subsidies for some esoteric green projects.

The same holds true with entities promising innovation. There are countless subsidies there, owners and managers are getting rich enough to buy mansions, luxurious cars and porn star girlfriends but hardly any innovations are coming out of that. One time I wanted to buy an item from engineering company which is thriving on subsidies. Purchasing procedure was so complex that I have realized that I have incurred more cost on this company than any possible profit they could make by selling me ordered item. I have asked manager over the phone why it is so and he was surprisingly honest. I was advised that they are living off EU subsidies, they may not sell anything at all as long as they are keeping up with production of documents as required by Brussels and that it *is* their business model. I have asked "what then?" Answer was "Then we will be rich so we can close down or apply for grants in another project".

Doing business in an honest way is long time gone. Now we are left with fraud, ripoffs, corruption, subsidies etc. This is last show in town before lights go off.

Capitalism no longer exists.

Martin

Edited By Martin Dowing on 06/04/2018 22:25:11

[larry PhelanParticipant @larryphelan54019]

My thanks to Dave for explaining this in simple terms. You have cleared up quite a few points which I did not understand. There is much talk here about building "Super Pylons" to transmit power from one place to another,and of course,no-one wants them in their back yard [or even their area ] Everyone wants them underground,but the E S B says that this would not work due to too high losses and heat problems. I understand now what they mean.

The only time I ever came across D C was many years ago when I worked on a 4 High Rolling Mill which was driven by a huge D C motor,supplied by a Mercury Arc Rectifier. It looked like something out of Dr Who,or Star Track ! These days the only place I see it used is for operating the tram system in Dublin [750 V D C ]

I never knew about the problem of AC reversing in the lines,never stopped to think about it,but of course it must,it does it all the time,by it,s very nature. Sometimes one can,t see the wood for the trees.

Thank you again for taking the trouble to explain

[Author]

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