Naked Science Forum

Non Life Sciences => Technology => Topic started by: topspeed3 on 09/12/2019 09:58:28

Title: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 09/12/2019 09:58:28
Have you ever tought about it ?

There is at least 12% more efficient turbines available than Betz Limit allows for a propeller.

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Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 09/12/2019 12:46:27
Here where I am referring to: https://iopscience.iop.org/article/10.1088/1742-6596/753/2/022056/pdf

In
case of VAWTs, first approaches to estimate the power output were presented by Shankar [2] and
Strickland [3]. In comparison to experimental data, their momentum based models suffered from
an overprediction of the power output. Slight improvements could be identified by Strickland
[3] using a multiple streamtube approach, whereby Lapin [4] proposed to represent the rotor
as two halves. Using an analytical double actuator disk approach, Newman [5] determined a
maximum power coefficient of 0.64, which is 8% above the classical Betz value. For a very large
number of discs he derived that the maximum power coefficient tends to a value of 0.66, i.e.
12% above the Betz limit [6]. Loth and McCoy [7] extended the analytical double actuator disk
approach by replacing the two straight actuator disks by two semi-cylindrical actuators. For
the velocity distribution along the cylinder halves a cosine-type formulation was selected. This
closed-form approach led to a maximum power coefficient of 0.617, hence 4% above the Betz
limit. Furthermore, considering the blade incident angle in each position to be influenced by
streamline curvature, blade camber, and the attachment point of the blade Loth and McCoy
derived a value of 0.610 as the maximum power coefficient, which is 3% above the Betz limit.
To overcome the drawbacks of streamtube models, e.g. their assumption of a one dimensional
flow Madsen et al. [8] used an extended actuator cylinder flow model. For the ideal case of an
uniform rotor loading they determined a power coefficient, which is 5% above the classical Betz
value.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 09/12/2019 14:00:17
There are several problems associated with VAWTs. The most fundamental is that whilst half of the blades are moving downwind at any time, half are moving upwind, so you need a feathering mechanism for each blade to maximise efficiency. This adds complexity and noise, and compromises reliability. In comparison, a HAWT can be efficient over a wide range of windspeeds with only one moving part.

Wind speed increases rapidly with height. The topmost tip of a HAWT blade is at almost twice the height of the tower, so generates more power per unit deadweight than a VAWT.

The support tower induces downstream eddies and turbulent flow. about 30% of VAWT blades are in the turbulent region, whereas HAWT blades are all upstream and all are producing power all the time. Eddies can be destructive  at high windspeeds.

Propellors replaced paddles on steamships many years ago, for very good engineering reasons.   
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 09/12/2019 17:00:40
There are several problems associated with VAWTs. The most fundamental is that whilst half of the blades are moving downwind at any time, half are moving upwind, so you need a feathering mechanism for each blade to maximise efficiency. This adds complexity and noise, and compromises reliability. In comparison, a HAWT can be efficient over a wide range of windspeeds with only one moving part.

Wind speed increases rapidly with height. The topmost tip of a HAWT blade is at almost twice the height of the tower, so generates more power per unit deadweight than a VAWT.

The support tower induces downstream eddies and turbulent flow. about 30% of VAWT blades are in the turbulent region, whereas HAWT blades are all upstream and all are producing power all the time. Eddies can be destructive  at high windspeeds.

Propellors replaced paddles on steamships many years ago, for very good engineering reasons.   


I would like to agree, but I cannot.

ANEW in Poland claims they convert wind power into electricity at 65-70% efficiency...way beyond the Betz's Limit.


Also my own prototypes with a secret pitch control system are able to sustain 300 G forces while rotating at 920 + RPM at 10 m/s wind....while creating power.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 09/12/2019 17:28:10
920 rpm limits you to a maximum rotor diameter of about 7m if the tips do not exceed the speed of sound (340 m/s). However with a horizontal paddle as illustrated you lose efficiency if the tips exceed about 1.3 times windspeed, so for a tip speed of 13 m/s at 920 rpm ( 10 m/s windspeed) you are limited to a rotor diameter of 0.3 m, which won't generate a lot of power.

The power generated by a single tower is related to the effective swept area of the rotor. With a HAWT this is  a maximum of πh2 but with a VAWT it is about 0.6 rh where h is the height of the tower and r is the radius of the VAWT rotor.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 09/12/2019 19:34:08
920 rpm limits you to a maximum rotor diameter of about 7m if the tips do not exceed the speed of sound (340 m/s). However with a horizontal paddle as illustrated you lose efficiency if the tips exceed about 1.3 times windspeed, so for a tip speed of 13 m/s at 920 rpm ( 10 m/s windspeed) you are limited to a rotor diameter of 0.3 m, which won't generate a lot of power.

The power generated by a single tower is related to the effective swept area of the rotor. With a HAWT this is  a maximum of πh2 but with a VAWT it is about 0.6 rh where h is the height of the tower and r is the radius of the VAWT rotor.

I recall that this had TSR of 5.

Next will be bigger and better...by far...with systems that allows me to measure output fairly precisely.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 10/12/2019 00:26:01
Now I've watched the video I have a slightly different view - the active blades are of course vertical, not horizontal, so the limiting speed is higher.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 10/12/2019 06:04:22
Now I've watched the video I have a slightly different view - the active blades are of course vertical, not horizontal, so the limiting speed is higher.

ANEW blades are not articlualting...but the McDonnell Aircraft Giromill in 1978 was such a device.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: Petrochemicals on 10/12/2019 07:25:50
I would say mechanical stability and reliability. The propellors are largley toward the centre  in weight, the blades are all forward and into the wind simultaneously so are being loaded at the same time, the force will be constant and fairly uniform. The other sort have forces acting one way then the other, varying ammounts each way.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 10/12/2019 09:48:57
I would say mechanical stability and reliability. The propellors are largley toward the centre  in weight, the blades are all forward and into the wind simultaneously so are being loaded at the same time, the force will be constant and fairly uniform. The other sort have forces acting one way then the other, varying ammounts each way.

Do you think this is the reason no attempts have been made towards this very efficient design ( H-Darrieus ) ?
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 10/12/2019 10:51:19
Yes. The cyclic fatigue loading on a fixed-pitch VAWT blade of any design is much greater than on a HAWT, and the only way to reduce it is to introduce cyclic variable pitch. This works for a helicopter where you have no alternative, but the additional complexity and/or reduced service life mitigate the economics of a VAWT. 

The advantage of a VAWT is its tolerance of gusty winds, variable wind direction, and close siting with other turbines. This suggests that VAWTs are potentially advantageous for inland sites where maintenance is less of a problem than offshore. 

A modern HAWT is basically a big glider wing, the aerodynamics and structural engineering of which has benefitted from enormous R&D in the aviation industry.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 10/12/2019 12:38:44
Yes. The cyclic fatigue loading on a fixed-pitch VAWT blade of any design is much greater than on a HAWT, and the only way to reduce it is to introduce cyclic variable pitch. This works for a helicopter where you have no alternative, but the additional complexity and/or reduced service life mitigate the economics of a VAWT. 

The advantage of a VAWT is its tolerance of gusty winds, variable wind direction, and close siting with other turbines. This suggests that VAWTs are potentially advantageous for inland sites where maintenance is less of a problem than offshore. 

A modern HAWT is basically a big glider wing, the aerodynamics and structural engineering of which has benefitted from enormous R&D in the aviation industry.


How come I see this the other way round ?

As the wings are straight in a VAWT it is more like an aeroplane.

HAWTs in my opinion only inherit the known bad virtues of an aeroplane propellor.

And the precession makes them hard to keep in the wind:
Here is a aeroplane model in a wind:
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 10/12/2019 14:49:34
Great video - thanks!  All you need now is a decent mountain, a steady wind,  and some way of extracting the energy as electricity! However as a slightly mad glider pilot, I'm sort of tempted to try it with a fullsize machine.....
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 10/12/2019 17:40:51
No problem alancalverd...and you are most welcome...beware of the G-forces !

I have worked on the final pieces of my third prototype...the wings of it.

Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 13/12/2019 16:19:47
How I see the efficiency per invested money goes in this is as follows:

1. System is easy to build as there is no need for double curved surfaces.
2. The contraption can be made outa steel ( 310 )..thus lasts a century or two.
3. Delivers always twice more than a propeller type HAWT.
4. Operating window is much larger than in a HAWT....delivers 30+ times more electricity to grid in a hard wind.

Not only do I think this is a better wind turbine...but I think it can be the solution to fight the global warming succesfully
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 14/12/2019 00:20:23
Double curves are no problem. Your wing seems to have a curved aerofoil anyway (but full marks for fine woodworking!) Adding tip washout or even constant alpha along the span of a propeller is not a problem

Aluminum lasts better than steel. Quieter, too.

Your feathering mechanism has to work though its entire range for every blade on every revolution. With a HAWT you can use constant pitch or simply adjust the pitch slowly to max power as the wind strength varies.

Money talks. Savonius rotors have been around for centuries and various other VAWTs are available, but when it comes to large scale generation, investors seem to go for HAWTs

Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 20/12/2019 11:29:50
Double curves are no problem. Your wing seems to have a curved aerofoil anyway (but full marks for fine woodworking!) Adding tip washout or even constant alpha along the span of a propeller is not a problem

Aluminum lasts better than steel. Quieter, too.

Your feathering mechanism has to work though its entire range for every blade on every revolution. With a HAWT you can use constant pitch or simply adjust the pitch slowly to max power as the wind strength varies.

Money talks. Savonius rotors have been around for centuries and various other VAWTs are available, but when it comes to large scale generation, investors seem to go for HAWTs



Investors go for HAWTs as there isn't a working H-Darrieus with naturally ( long lasting ) articulating pitch control at the market place. It also has to be tested and analysed before it ever can enter the market.

I disagree with the double curved aspect. Steel plated wings would last a lifetime or 2.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 24/12/2019 12:21:50
There are plenty of rapidly articulating pitch control mechanisms around. Every helicopter has at least one. But even with only 2 to 5 blades, and a fairly constant rotor speed, they are horribly expensive to build and maintain. Large propeller planes and windmills have pitch control but it's very slow-acting as it only has to match pitch to a constant airspeed. Even so, and after almost 100 years of military-budget R&D, it's the most unreliable part of the mechanism. 
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 26/12/2019 07:57:11
There are plenty of rapidly articulating pitch control mechanisms around. Every helicopter has at least one. But even with only 2 to 5 blades, and a fairly constant rotor speed, they are horribly expensive to build and maintain. Large propeller planes and windmills have pitch control but it's very slow-acting as it only has to match pitch to a constant airspeed. Even so, and after almost 100 years of military-budget R&D, it's the most unreliable part of the mechanism. 


Then they are not naturally articulating system like I have developed.

Anyway..the need for change is very real now: https://www.naturalnews.com/2019-08-26-wind-turbines-create-more-global-warming.html

Harvard claims the HAWT propellers cause more warming than coal burning.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 26/12/2019 10:04:08
Not sure what "naturally articulating " means, but it certainly involves moving parts, and is almost certainly more complicated than a gyrocopter swash plate, which only has to feather two blades at a fairly constant rate.

The "global warming" of windfarms is all about the quantity of fossil fuel required to mine, form and erect the materials to make them, including the massive concrete foundation for an offshore rig, and the extra kit needed to attach them to the existing grid. Short term, it may indeed be a climatological disaster. The turbulent loss, wind energy that is not turned into electrical energy, is indeed heat, as is the friction loss in the blades, but the difference between HAWT and VAWT is negligible.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 31/12/2019 05:07:06
Not sure what "naturally articulating " means, but it certainly involves moving parts, and is almost certainly more complicated than a gyrocopter swash plate, which only has to feather two blades at a fairly constant rate.

The "global warming" of windfarms is all about the quantity of fossil fuel required to mine, form and erect the materials to make them, including the massive concrete foundation for an offshore rig, and the extra kit needed to attach them to the existing grid. Short term, it may indeed be a climatological disaster. The turbulent loss, wind energy that is not turned into electrical energy, is indeed heat, as is the friction loss in the blades, but the difference between HAWT and VAWT is negligible.

Yes for the current systems...it is not much.

https://www.researchgate.net/publication/47438608_Potential_order-of-magnitude_enhancement_of_wind_farm_power_density_viacounter-rotating_vertical-axis_wind_turbine_arrays

I will inform you as my system has been fully tested.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 31/12/2019 10:10:35
Interesting article, and potentially useful in large desert areas. I always begin from a UK perspective: all the best land sites are already occupied, or protected habitats, or dangerously/uneconomically inaccessible, and there just isn't enough land area to generate more than 5% of the required power. So we need offshore windmills. No shortage of space or wind, but reliability and longevity are essential so the exposed  mechanism must have as few moving parts as possible, hence the 3-blade constant-speed propeller seems to be optimal.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 02/01/2020 09:41:47
Interesting article, and potentially useful in large desert areas. I always begin from a UK perspective: all the best land sites are already occupied, or protected habitats, or dangerously/uneconomically inaccessible, and there just isn't enough land area to generate more than 5% of the required power. So we need offshore windmills. No shortage of space or wind, but reliability and longevity are essential so the exposed  mechanism must have as few moving parts as possible, hence the 3-blade constant-speed propeller seems to be optimal.

Yes they seem to be. But if we rely on science the best solution is still on the drawing board....unfortunately.
Almost noiseless system that is heavily affected by the Newtons 1st...needs very little fuss with foundations for instance.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: Gutalin on 09/01/2020 07:38:43
This closed-form approach led to a maximum power coefficient of 0.618, hence 5% above the Betz limit.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 13/01/2020 12:45:43
This closed-form approach led to a maximum power coefficient of 0.618, hence 5% above the Betz limit.

Aachen study 2017 claims even 12% exceeding above the Betz limit is possible.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 13/01/2020 15:13:20
I repeat: efficiency isn't a problem, reliability is.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 15/01/2020 16:49:53
I repeat: efficiency isn't a problem, reliability is.

It can  be...for instance McDonnell Aircraft said their Giromill (1978) system was unreliable...due to few mistakes in manufacturing it.


Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 15/01/2020 22:53:32
Meanwhile, the 250-year-old HAWT windmill down the road from here continues to operate from time to time, though I understand that the applewood bevel gear has been replaced at least twice and some of the brickwork has been modified.
Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: topspeed3 on 17/01/2020 18:26:57
Meanwhile, the 250-year-old HAWT windmill down the road from here continues to operate from time to time, though I understand that the applewood bevel gear has been replaced at least twice and some of the brickwork has been modified.

250 is a lot.

Most VAWTS are 1000 years old.


Title: Re: Why not make efficient wind turbines instead of HAWT propellers?
Post by: alancalverd on 17/01/2020 18:49:22
Touche, mon ami!