wind turbine redesign?

Kevin O. Pulver_2

Have you guys seen it? Go to youtube and search windmill destruction or something like that. It was in Denmark if I remember correctly, and even at slow motion speed, you can't really believe how fast everything happens.
One blade comes apart (they're hollow you know) number two hits it and self destructs, number 3 appears to shear off at hub purely from shock, head twists about 90 degrees, and tower hits the ground- all faster than you can snap your fingers. Watch it! Someone stated above that as things increase in size the stresses increase exponentially. Doubling the size might increase stress 8 times for example.
Dempster and Aermotor windmills with a 6 or 8 foot fan can easily last 100 years pumping water for the cows, but a local employee of the electrical utility told me that 10 years is a long time for some of those big boys. Kevin

nicholas bonham-carter

wind turbine redesign?

re dans news letter and the 4 minute video

http://www.doobybrain.com/2008/05/22/time-lapse-video-of-wind-turbine-construction/

i don't understand why the heavy generator is always placed at the top of the tower.surely some sort of mechanical drive linkage could transfer the rotational power from the blades to the ground where it would then turn the genset [or why not a commpressor as well for a heat pump setup?]
valmont ind. west of us here has a self-erecting wind turbine which is a real work of art,but the strength of the tower would not permit the addition of more machinery which could be driven by the wind.--nbc

DanHolohan

Good point

and I think the newer designs are going to change this, especially with the ocean-based turbines, such as the one's I showed last week in the eBlast.

Thanks for reading me.

Roland_15

Wind Power

I'm no expert, but, I'd think a driveshaft arrangement might be too heavy considering the length and torque involved. There could be the danger of destructive resonance to consider. Although, if the driveshaft were made of a composite material, it might address these issues.

Also, a considerable amount of power is lost due drivetrain friction. Think of how much HP is lost in a rear-wheel drive car with the differential and transfer cases.

jp_2

mechanical losses

I agree the mechanical losses and problems transferring that much power that distance could create lots of problems.

if they were compressors they would be very limited point of use only devices. no practical way to transport compressed air. already in place electrical transmission.

the heavy generators could be part of the overall design for mechanical balance and harmonic balancing.

Unknown

What is an eblast, and how do I get the news letter ?

Ted_5

hydrolics is one way

I have heard of to transfer from the blades to the ground. I agree, you will give up energy to do this. Just like a heat exchanger, it cannot transfer 100% of the energy across!

Ted

jp_2

still lots of losses in hydraulics

you'd need a pump at one end and a motor at the other, still lots of losses compared to a generator right at the propeller.

Charlie from wmass

actually

rear drive cars are more efficent for equal size cars and engines than front drive cars. but that is more due to car design and torque wasted through the CV joints. this is why race cars are rear wheel drive , it is more fuel efficent. Front drive is popular due to the added traction gained in small cars by placing the engine over the driving wheels. this is why porsche and others put engines in the back and drive with the rear wheels. Mid engine is even better but hard to fit passengers.

Unknown

Mechanical transfer of wind energy is nothing new, In-fact that how it all started with mills and pumping.

The reciprocating action of a traditional water pump seems a natural application for mechanical energy transfer.

As far as the drive train losses for an automobile how significant is this really? I'm thinking that friction losses end up as heat and perhaps sound to an insignificant extent. When my wife gets home from the ridiculous kid activity driving spree that she is currently engaged in I plan to check those CV joints. I don't think they are going to be much above ambient. I can't imagine that a well lubricated CV presents significant energy transfer issues.

I would agree that a front-wheel drive vehicle may actually have more drive-train losses but, as percentage of consumed energy I'm thinking this would be insignificant. Interesting question.

Charlie from wmass

Ureeekaaa

I figured it out it is to counter balance the props. they catuall weigh a lot and if you balance the load the tower can be engineered to closer specs. If the turbine was at ground level the tower would want to lean over towards the prop side. and then would need cables out from the top to counter the weight. but if it is balanced it will pivot in the wind so it always points into the wind.

J.C.A._3

Hey Charlie....

Porsche also makes front engined vehicles. One way they deal with the weight and power distribution (balance!) is by putting the transmission at the rear.

It makes for a better balanced package, and a better handling vehicle.(48/52 ain't bad when handling becomes a chore!)

Now my thought....Why not make a windmill/Turbine wheel in the horizontal position and hook a drive up to it directly to the ground...in the same orientation?

Seems to me that if the wind will turn it facing into the wind....they could cut out the whole "gimble/turning" bits at the top of a tower.

I know it would most likely not be as efficient as a vertical spinner...but it would save a whole lot of money in repairs and insurance if no one had to climb a tower to fix a problem with the stator. Just thinking out loud.

Part B...Why isn't there a stator around the blades now...increasing the output further?
Little magnets inducing yet MORE current into the supply...Chris

nicholas bonham-carter

vertical blades

i have also seen vertical blades on some wind turbines-maybe that configuration would lend itself to lower genset placement.
when i spoke of a compressor i meant a freon compressor for a heat pump--nbc

Glen

not just mass -

but the method of energy transfer; some are direct drive, some single stage gear box some with multi stage gearbox. Add in the idea of the mass of variable pitch rotors up to 116 meters in diameter and the torque is substantial (rotor tip speed of 75 - 85 meters/sec). Not sure what the losses could be - but I think the euro engineers that lead the way on this technology have that already figured out. Both in the extra costs of production and energy losses.

Steve Ebels_3

Supposedly......

The largest windmills in the world are going up about 10 miles from my house. After looking at the blades, (I should take pictures)I can see why they want direct coupling to the output shaft. The tower is going to be 300' tall so picture the type of shaft and support that length needed to transfer
roughly 5500 horsepower. At least one right angle gear box at the top of the tower would be needed and it alone would be a serious piece of equipment. Now think of the flex in a 300' long shaft with probably close to 20,000 lb.ft. of torque on it.......... Much easier and less expensive to transfer electrical energy than it is mechanical.

The Mrs. and I detoured on our way home a couple weeks ago to see what kind of progress they are making and they have the mounting base complete and the 3 blades are on site.
I paced off the blades at 48 which has to be close to 145-150'. They are about 12' wide and I could drive my F-250 into the root of the blade and use it for a garage. Huge would be a valid term. It's difficult to imagine them swinging away up in the breeze. The are just enormous.

The footing or foundation for the tower is itself off the scale of anything I have ever been around other than a skyscraper. Steel I-beams were driven into the ground 125' and then they poured 600 cubic yards of concrete on them to form the base. There are over 90 2"x12' threaded rods in the concrete that the actual tower base will bolt to.

I heard a couple weeks ago that the crane needed to erect the tower will be arriving in pieces on 40 semi trailers. The blades were delivered at night to avoid traffic on trailers that steered on each end.

nicholas bonham-carter

wind turbine improvement

when i hear about the huge cranes needed to to erect these monster wind turbines it makes me think that my idea of putting the machinery at the base has even more justification.i am sure that the engineers who have designed these giants have the best of intentions but it looks like a bad design to me.i am sure that there would be no problem in transfering the rotation down to the ground with minimal loss.
let us all experiment in our back yards with this and see if it is better up or down!!--nbc

jp_2

steve makes good points

one of which is 5500 hp.

think of your trucks 200 Hp and the drive shaft it uses.

now multiply that by 27 times. then think of all the necessary supports for that 300ft drive shaft. then think about the inertia involved. then consider the balance problems of a 300 ft long drive shaft.

great that you want to build a backyard model, Iam all for that. but its not easy to then assume something 1000 times larger will work that same.

with what it takes to design such a machine, i doubt someones going to say, "boy, why didn;t we think about that?"

J.C.A._3

RE: the last statement....

My thoughts exactly. The reason I brought it up is because I don't bounce like I used to. If something to fix were on the ground, I think I'd be far more interested in repairing/servicing it.

Climbing towers just doesn't seem all that friendly to me anymore. 20 years ago, I would have been the first up the ladder, not so much now. Chris

nicholas bonham-carter

belt drive?

how about belt or chain drive from blade spindle to ground mounted genset--nbc

jp_2

can't agree more JCA

I do not bounce as well as I once did, even though I weigh the same as 20 yrs ago, old guys don't bounce!

but with those horse powers i can see where the generators gotta be up there.

there are several designs of the vertical nature, not sure they can deliver the same output though.

Unknown

If we shift axis the structure must be able to resist these forces in addition to resisting the force of from the wind etc. I have a feeling that this is a fairly mature technology and that the designs we are seeing represent the state of the art.

Every so often the average joe has an idea nobody has thought of before, but I have a sense that wind power is a fairly well examined subject. To bad our country is not taking a more leading in this and other alternative energy development.

Charlie from wmass

direct drive is best IMHO

due to a few reasons.
1. if the tried to drivethrough a right angle gear box the gears alone would be massive.
2. the torque back load from the generator would make the props walk out of the wind.TRy attaching two right angle gear boxes together with the out put of one in a vise, you can borrow a couple off the electricians right angle drill. then turn the shaft that is farthest from the vise. it will turn freely and the top right angle drive will pivot around. Now picture 5500 hp and god knows how much torque doing that. it would work if the gear boxes were locked together but then the whole tower would need to pivot to be facing into the wind.
3. the issues with friction loss on a 100 never mind a 300 foot drive shaft would be enormous.
4. wire can have volts and amps adjusted to allow different( read smaller) transmission of power. high volts give lots of amps through small wires. think 22o to a water heater v.s. 12 volt on your truck battery.
5. the counter ballance I mentioned earlier.
6. shape and design of turbine acts as a weather vane to aim into the wind.

Then again I might be all wet.

J.C.A._3

Like my earlier comment about the 50/50 balance.....

I can see that having the gen set high on the tower CAN counterbalance, and eliminate a whole bunch of "wobble"...were a drive train to be installed.That makes sense.

A wire or set of wires going to the grid WOULD make things a lot easier to deal with, and a bit less expensive than a pile of bearings and stays attached to a ground set generator.

Although I would still like to work on the ground, I'm sure there are a bunch of heavily testicalled guys willing to do the job.(May the Lord bless them!) I will now count myself NOT among them.I'm A-SCARED! Chris

Charlie from wmass

at least some guys will always opt for hazard pay positions. at least with wind turbines the guy in the trenches has the option for good pay. saftey first of course. I am not saying I am all that brave just different when you can put a $ sign to a job and not have a numbers man say "why does it cost so much?". one look at those towers and they will just say "cheaper then what I would charge to do that." on a home unit you had time to tinker with a gen down low would work fine. also a tower that can be lowered would work to keep you on the ground. maybe a collapsible tower would be a thing to engineer?

Steve Ebels_3

I never did bounce. Has nothing to do with getting old.

Steve Ebels_3

The problem with belts or chains.......

What happens if the head set on top of the tower does a couple 360* spins on the vertical axis due to changes in wind direction? You would have to have the generator mounted to follow. That in turn means output from the generator would have to be passed through some kind of a ring with movable contacts. Not good when you're handling that amount of current.

Greg_41

Working on wind

I had a chance to talk to a couple of techs that worked on and installed the big turbines, and except for getting up there, it's a large well lit mechanical room to work in. Just like working on some roof top units, it comes down to cranes and mechanical helpers when there's work to be done. Wind and hydro seem like you put it in right the last time, and let it rip. 300' towers need elevators, that's all.

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Constantin

Also consider...

Hey Steve, thanks for the informative post! I'd love to see a tower go up too sometime in my lifetime... Just some additional thoughts for folk advocating a generator in the base of the tower...

Just how often does the generator break down vs. the rest of the rig? If the rate of breakdown is no different (or less than the mechanical items) then having the stator integrated into the rotor makes a lot more sense than mechanically transmitting power down. Fewer parts = higher reliability, all things being equal.

Even if you managed to transmit the power to the base of the tower by mechanical means, you'd still have to climb the tower to inspect bearings, transmissions, etc. Thus, siting the power generation stuff elsewhere does not save you from a lot of stair climbing. Never mind the additional operating expenses, gearing losses, etc. of not going directly to electrical power at the rotor.

IIRC, the enabling technology here are IGBT and similar power transistors that have largely eliminated the need for complicated mechanical gearing systems as in yesteryear. Just as a homeowner can now hook up a SunnyBoy to grid-connect their PV system, the power electronics that are in these wind generators (at a much larger scale) take the power at whatever frequency it is generated at, and convert it to DC, then generate AC that matches the local frequency.

Having the generator up high may also buy you better cooling, since the windspeeds at the tip of the tower will be higher than at the base. Lower-temperature electronics are happier electronics and you may be able to generate more usable electrical energy this way (i.e. less power needed for cooling).

Vertical-axis turbines have been around for years, but it is my understanding that most/all of them are not as efficient as the horizontal-axis models when compared on a tower-height basis. IIRC, it has to do with the average windspeed, which increases a great deal once you go higher up. Not so much an issue with units sited on a cliff, a greater issue with units sited in rolling landscape. Boundary layers and all that.