Re: Windmills in Winter ...

[Tim Lamb]

In message , tony sayer writes

Brinelling. Inadequately specified bearing if a static load does this.

Don't know about Locos but the trucks use spherical rollers; like beer barrels.

[Dave Plowman (News)]

Sounds like they need to do some research into the efficiency of gas turbines too then if they really do waste such an incredible amount of energy.

I don't know much about such heavy generating plant - but thought that gas turbines were used as an 'instant' solution to peak demand? Where a coal fired one can't react quickly enough?

[The Natural Philosopher]

There is work being done, and it helps BUT you cant get away from the fact that efficiency is not constant with load, and that getting a big set up to temperature uses energy that is totally lost every time you switch it off.

In generally that happens once a day at the moment with most gas sets as its uneconomic to run them overnight into the market price of electricity that pertains at that time.

Adding wind to that increases the number of stop start cycles to several a day, and forces a lot more CCGT to be on-line at part load - still suffering the same parasitic thermal losses from the plant - in order to be available for instant ramp up should the wind unexpectedly be less than it was forecast.

AND if you look at the data on BMreports you will see that the errors between forecast and out-turn are often out by several GW in a big wind situation. There are two reasons for that. First is the nature of the wind-speed/power curve, which is square law, so slight errors in forecasting make big differences in out-turn. Secondly, at a given windspeed operators will shut down farms to prevent turbine damage, and this happens suddenly and without warning.

To pass off these deficiences in wind generation as a problem with gas turbine designs is typical of the sanctimonious buck passing attitude of renewable energy aficionados, who see the rest of the grid and generating capacity as there t server their interest alone, and not those of the consumers or the nation at large.

IN short their, and your attitude appears to be, "If my technology makes a problem for your technology, that's not my problem, its yours".

And when the gas operators say 'well, f*ck you then, I am closing efficient plant and not building more, because it's making my operations unprofitable, as I can't get decent efficiency from my otherwise decent gas turbines" you will no doubt spin that into 'deliberate underinvestment and gouging by power companies".

Frankly, I am sick of the renewable movement disguising its pathetic inability to supply anything anyone want or needs into a burden to be placed onto the shoulders of others to sort out.

neither true. Gas turbines take at least 45 minutes to reach full power if they are combined cycle, and 15-20 minutes if open cycle.

Coal plant is able to be throttled back and because its so inefficient anyway, losing most of its energy as waste heat of one sort or another, it can respond pretty quickly - even to short term demands due to there being a lot of energy in a boiler full of steam you can tap temporarily.

Fast small fluctuations are handled by the pumped storage, and hydro gas will respond in tens of minutes, and coal in - for BIG changes, a matter of an hour or so provided the plant is up and running at all. AS can nuclear.

The reasons for the way things do respond are more economic than technical.

Short term shortfalls mean higher prices and its worthwhile spinning up gas for that, or dumping hydro.

Even if it wastes gas. Because maintenance on gas plants is less than on coal - they have lower fixed costs, so they are happy to sit idle and only fire up occasionally IF the price they can get justifies the poor efficiency they are getting.

The Hughes report showed exactly how this would all pan out with subsidised renewables driving efficient clean baseload gas off the grid and it being replaced with inefficient open cycle and diesel STOR sets that are cheap to build, but massively inefficient to run, but make economic sense if they don't run very much at all, and then into extremely expensive electricity shortfall periods.. The fact that they are massively emitting CO2 in comparison to a CCGT running baseload, doesn't bother the renewable crowd. They are not there to reduce CO2, but to make a guaranteed subsidised profit, after all.

[Dave Liquorice]

A single railway loco weighing say 100 tonnes will be supported on 12 bearings straight down.

The hub and blades of windmill weighing in at 40 odd tonnes are on a single bearing with the load offset.

[Chris J Dixon]

Actually, it can be a problem. There was an instance where a coach was left parked for an extended period near a test track, and the vibration transmitted from vehicles under test caused bearing damage.

Similarly, spare traction motors in storage need to be manually turned every so often as a precaution.

Chris

[tony sayer]

OK but of course windy mills are always running somewhere. Seriously is this just a poor design or lack of a suitable spec'ed part for the job or are they all at risk of bearing failure?..

[The Natural Philosopher]

everything about wind turbines is a hard engineering problem

Inherently unbalanced in several different ways, made worse by insect ice and dirt build up in the blades, and ground shear.

Utterly unpleasant conditions of variable temperature and humidity and at sea, salt spray..

Prone to massive torque surges when the wind gusts..

Far more like to run out of control than nuclear power station.

No one in their right minds would consider them an effective way to generate electricity...

[dennis]

ITYM two bearings, one at the rear end and one by the blades. The one by the blades will have a vertical force downwards the other may be up or down depending on the weight distribution.

The lateral force will probably be taken by a separate thrust bearing or two.

Not really any different to a train.

[dennis]

I think there is plenty of proof that they are effective. They just don't meet the requirements very well. They are also inefficient at saving carbon or providing reliable power.

[The Natural Philosopher]

there is seldom one at the rear end

I suggest you look at a few cutaways.

for example

Thrust bearings do not control lateral forces, only axial ones.

Completely different from a train.

[dennis]

Lateral with regards to gravity!

Well trains may lack the thrust bearings and just use the end of the axle.

[The Natural Philosopher]

I suspect they use normal taper bearing to control thrust as well as locate the axle. A cornering train exerts plenty of thrust.

Same as with a car front wheels.

you don't use a separate thrust bearing unless there are severe axial loads..

When you think about it a bearing morphs from straight to taper to thrust, and the angle of the races reflects the ratio of expected loading more or less.

[MattyF]

They certainly can get bu^^ered rails!

Needs more sand!

[Clive George]

How did that happen then? Thermite spill or something?

[MattyF]

If the train was stationary on a hill and one axle was rotating for a while, that does happen.

It seems to have happened in South Africa in 2009. Many locos have anti slip protection these days. Trains and trams often have a means of putting sand on the rails to avoid slippage.

[tony sayer]

Bloody hell!! whatever happened to the wheel?. I'd have thought the whole would have ended up welded together;!...

[news]

I think it might be to do with vibration. The rotor on the top of an AWACS aircraft always rotates when the aircraft is flying (and probably whenever the engines are running) - only slowly compared to when the radar inside is transmitting, but it rotates nevertheless. This is I understand to prevent bearing damage. Brinelling I believe the failure mode is called.

So a windmill not turning because there is no wind would probably be safe enough, but a rotor stopped when the wind is blowing could easily cause damage, I would have thought.

A parked ralway loco is unlikely to cause damage but install an oversized vibrator and things might be different.

[tony sayer]

Of interest...

A similar-looking kind of damage is called false brinelling and is caused by fretting wear. This occurs when contacting bodies vibrate against each other in the presence of very small loads, which pushes lubricant out of the contact surface area, and the bearing assembly can not move far enough to redistribute the displaced lubricant. The result is a finely polished surface that resembles a brinell mark, but has not permanently deformed either contacting surface. This type of false brinelling usually occurs in bearings during transportation, between the time of manufacture and installation. The polished surfaces are often mistaken for brinelling, although no actual damage to the bearing exists. The false brinelling will disappear after a short break-in period of operation

[Capitol]

Think I saw a program about recovering a locomotive from Turkey/India, where they said that they had to check the plain bearings were still round after being left standing for a few years. Anyway on the trip, one of the bearing shells actually fell out, but was recovered, reinserted and worked adequately for the rest of the journey. I would not be surprised if a plain bearing distorted slightly over years with static locomotive loadings of several tons on it.