WHY ARE WINDMILL BLADES IN VERTICAL PLAIN?

With the blades in a horizontal plane you would have the moment in one direction cancel out most of the moment in the other direction.

There were some horizontal designs in the past but they did not last long because they were almost based on PM.

Then of course the one side can be shielded but . . .

How about this one? I have always liked the design, does seem to have a large footprint.

Drew

They are not as efficient. But they do exist. Courtesy of WIKI:

Wind mostly blows horizontally, rather than up or down. It helps to make the blades perpendicular to the wind direction....

Cos they is asier to make i think.

http://en.wikipedia.org/wiki/Vertical_axis_wind_turbine

http://www.talentfactory.dk/en/tour/design/horver.htm

I have not a picture to copy here but there is other type with elements distributed as in the Lynlynch picture but not with spherical cups: with sails attached in same way.-

Thanks fro so many who have participated. But at the end I could not find nay conclusive evidence against using verticle shaft. Comment by Hendrik end with BUT... meaning, it could be acheived - may be it is possible.

The photo pasted by lynlynch of cups (and some doubt Hendrik has can be solved by - NOT having all cups in one single horizontal plain. That way - one cup is not in the shadow (for wind force) of the other. Suitable static guides could be placed to direct the wind towards specific side of the wane..The cups / blades could be distributed vertically in different horizontal plains.

Why I raised this issue is - I felt that all cups or blades will be under same gravitational force. So effect of gravity is removed and this could improve efficiency to soem extent.

Eevn if is verticle axis- it can still be mounted on taller tower. Number of blades or wanes can be increased, and adding wind directors/ guides.

I only felt that the work done is insufficnet to conclude that vertcle shaft is ineficient.

Did you look at the link I provided. I see that the picture I put is gone, I will try again. I found it on wikipedia where there is a bunch of good info on this type. I found it by searching egg beater windmill.

Drew

The link is still there. That little blue square is all that's visible but as you move your cursor it will change to indicate that there is information there.

Sometimes if you click on the original image and open it and paste the copy of the second image it will stay with you.

Cheers.

There is hot debate between proponents of the Vertical Axis Wind Turbine, (Vawts) and some proponents of Hawts (Horizontal...) - most opt for Hawts, hundreds of companies all over the world. With Vawts there are several arguments against, - 1/- the best wind is up higher, 2/- part of the Vawt blade is coming back into the wind, 3/- It seems to take a lot more material to build a vawt. Having said that there are still companies bringing out vawts, mainly concentrating on urban areas where the wind is very erratic, (but unfortunately not very strong). For further info, Paul Gipe is excellent, discusses also Vawts etc, http://www.wind-works.org/books/WindEnergyBasicsRevised.html Cheers, Geoff Thomas, Advanced Wind Technologies, Australia.

good day

the problem i have with vertical shaft wind-wheels is that the area on the left would always be equal to the area on the right therefore canceling out some of the power.

The blades can be designed to create a difference and it does work.

One can mount a plate on a bearing and by just bending the edges in different directions it will rotate.

I did experiment with vertical shaft wind-wheels some 40 years ago but found that the power output on a normal horizontal shaft wind-wheel exceeded the power for a vertical shaft wheel using about the same area (and cost) of blades.

Another advantage of the horizontal shaft wheel was that one could tilt it out of the wind direction in strong winds.

Forgive me if I am misunderstanding your question, but windmills of the Dutch windmill and the present wind powere generator windmills, are configured to face the wind from which they derive their propulsion. The wind usually flows across the planet rather than in updraft or downdraft conditions. For the same reason, propeller driven aircraft tend to move in the direction of thrust of the propeller blades. Conventional ones generally move forward and vertical take-off and helicopters can move vertically. There are some windmills, like the Darieus which rotate about a vertical axis. They are less efficient than the types generally seen in current power generation applications.

In respect of the use of guide vanes and deflectors, these have the tendency to reduce available thrust to the windmill blades as the velocity vector reduces imparting directional change to the airstream. As a consequence even less efficiency could be expected. It is not so much to do with speed but the torque able to be generated from the force on the blades.

But if I'm on the wrong track re your question could you clarify the question please.

My understanding about air crafts and helicopters is the jet engine or propeller engines just ensure air to flow at high speed and it is the wings (air crafts) which give upward thrust or downward thrust - for ascending or descending. In the case of helicopters- the

Propeller blades are tilted for the same function.

Blades in vertical axis windmill are still perpendicular to the direction of the wind. You are also right that it is not the wind speed, but the torque generated. To have higher torque, one has to have higher radius. What I noticed about Darieus designs from the links given by various people is - it does not seem to have same aerodynamically designed number of blades - like in the case of horizontal shaft.. Again blades in horizontal plain does not mean - all are in a single horizontal plain which would cause shadow problems as mentioned earlier.

So is there still scope for improvement or do we take Darieus design as end of it and give up further work?

"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." -- Orville Wright

Dear Mr Divakar,

1. The engines create or generate thrust and have no relation with the 'drive to air' or 'driven by air'.

2. Your concept about propellers of helicopters is ok. But in case of 'wind mill' the 'wind flow' is the power which rotates the propellers coupled to generator.

3. The speed of the propellers is controlled within limits in all cases to avoid damage.

Regards.

I have looked at [Conventional] blade propeller style on horizontal shaft axis and vertical shaft axis Power Vane style for water & power generation. All conventional horizontal axis have to rely on turning the propeller into the direction of the wind to obtain maximum efficiency. The vertical shaft Power Vane is Omni-directional meaning it obtains maximum efficiency no matter the direction the wind blows from as in the outback of Australia. The Conventional Propeller style is also a blight on the people of the vacinity due to the shear harmonic drumming hum the propellers give off sending the populace "Nuts" and deminishing the tranquil life styles of semi and rural lifestyle. I have had the experience (Newcastle NSW) where I stayed on a job site which was extremely unsettlng to just work in the area let alone live with the constant noise. The wind farms have tried to embrace the clean energy at the cheapest cost and seem to have the attitude of 'To hell with those who don't want the destructrive noise'. At least, that is my take on the Monsters.

Hail to the quieter Vertical shaft wind power generators.

Thank you so much- at last I found someone giving practical experience and supporting vertical axis wind turbines. If there are minor shortcomings, it can always be overcome - or taken care of in future installations. I fully agree with you that many MNCs have that attitude of don't care fr pub;ic and use doctorates and make them publish papers in their favor etc etc.

Not sure if they have to make that noise. I saw a video of a helicopter who's blades had a flap that flipped up and down and eliminated the noise. Here is a link to the Popular Science article about it.

Drew

Dear Mr tecmate,

Thanks for your concern for public health. My practical experience in my childhood with folded paper helicopter is different. Most of the times the rotor with 03 blades, bearing on a stick showed following results.

1. As long as the stick is kept horizontal, the rotors moved in breeze or on running of the child. Same was the case with rotors with a fixed shaft and driven by water.

2. Whenever the stick was made vertical (thus the rotors in a horizontal plane), the rotors stopped moving (please avoid thinking of upward thrust and dislodgement which happened).

3. The children had no concept of 'angle of attack' or mathematical calculations for designing. Still the results were as good as (or better than) from an engineer (myself).

4. For the last 33 years (since I spent 17 years of my childhood and boyhood at my village in Uttarakhand and had no fans), my ceiling fans have been making more noise than my table fan at full speed.

Regards.

Hi rssahni,

I remember those, but it is easily explained

In the case of the stick being horizontal and the child running, the flow direction to the paper-folded blades causes a reaction roughly towards a plane at 90 deg to the inward flow direction. Your paper-folded windmill is in essence a rough creation of a reaction blade impeller. There will be a pressure differential either side of the blade. If you were to hold the stick vertical and run across the horizontal ground there is equal likelihood of the child rotating as the impeller rotating.

If the child were to jump high or jump from a cliff, with the stick vertical, the impeller would rotate. Held horizontal - nothing.

For your ceiling fans, they will be noisier than the table fan as the ceiling fans are usually a totally flat blade with no profiling, and from an aerodynamic point of view the least efficient of the axial fan variety. Compared with the table fan which is most likely to be a countoured blade, albeit crude but nonetheless a little more efficient. The ceiling fan is also more likely to suffer out-of-balance forces and subsequent noise. However your ceiling fan is probably providing a greater volume movement at greater penetration than your table fan.

Fitting the blades vertically is to avoid the turbulence caused by the blade on its own path. the vertical configuration provides different planes to all sections of blade and the lower blades provide a small thrust to upper one and creates the suction for the bottom one. In horizontal configuration, there will always be less wind and loss of thrust.

You may find this one enjoyable and helpful

http://www.youtube.com/watch?v=Zrp0RC3XTpw&feature=related

Thank you for that link to the You Tube which is quite self explanatory..

Perhaps we could contemplate a Savonius rotor with a horizontal axis, turned by a downstream vane to face the wind. The upper blade would receive higher velocity wind, while the lower returning blade would be resisted by lesser velocity wind nearer to ground level (and perhaps even shielded by a wall).

Posted 07 Apr 2010. Subsequent claims may be challenged.

http://www.generadoreolicowm.com/spain/index.htm

Thank you so much. The simplicity must be appreciated.

On TV, I occasionally see wind turbines, used to generate electricity for a household, mounted on the roof, and turning in the horizontal plane. However, they are not traditional "Dutch grist milling" designs; they look like vertical columns made by setting vertical blades in flat round "disks" at the top and bottom of the column, into which the vertical blades are attached. The two disks have a shaft running through their centers (using bearings I assume); that shaft is attached at the bottom to a generator (or gear box?), which is turned by the rotating disks/blades attached to it..

One clear advantage of this type of design is that it is NOT directional. That is, the wind can come from any direction, and affects the turbine blades equally no matter the direction. I don't know if or how this affects efficiency overall, but elimination of the need to keep the turbine facing into the wind has to be a big plus.

I remember now that I saw an advertisement for a show in which Ed Begley (the actor) and Bill Nye (the "science guy") are in a friendly competition to have the "most green", most energy efficient house. Ed Begley is shown on the roof of his house, standing next to one of these "windmill" generators, describing what it does to help reduce carbon emissions and thus, "global warming". Ed Begley announces that his rooftop windmill/generator cost $3,000, but he believes prices will come down quite a way over the next few years, etc. I have seen this type of generator elsewhere, as well.

I am as interested as the next guy/engineer in the quest for cleaner power, so I will make it a point to record where and when I see other examples in the future; I will share that info here if it seems appropriate at the time.

I think it is important to be able to "brainstorm" and talk about "wild ideas", and to think "outside the box". My best designs have come from doing so.

Dear Friends,

Following copied from 'wikipedia' may may be useful:

Horizontal axis (Wind turbine)

Advantages

• Variable blade pitch, which gives the turbine blades the optimum angle of attack. Allowing the angle of attack to be remotely adjusted gives greater control, so the turbine collects the maximum amount of wind energy for the time of day and season.
• The tall tower base allows access to stronger wind in sites with wind shear. In some wind shear sites, the wind speed can increase by 20% and the power output by 34% for every 10 metres in elevation.
• High efficiency, since the blades always move perpendicular to the wind, receiving power through the whole rotation. In contrast, all vertical axis wind turbines, and most proposed airborne wind turbine designs, involve various types of reciprocating actions, requiring airfoil surfaces to backtrack against the wind for part of the cycle. Backtracking against the wind leads to inherently lower efficiency.
• The face of a horizontal axis blade is struck by the wind at a consistent angle regardless of the position in its rotation. This results in a consistent lateral wind loading over the course of a rotation, reducing vibration and audible noise coupled to the tower or mount.

Disadvantages

• The tall towers and blades up to 45 meters long are difficult to transport. Transportation can now amount to 20% of equipment costs.
• Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators.
• Massive tower construction is required to support the heavy blades, gearbox, and generator.
• Reflections from tall HAWTs may affect side lobes of radar installations creating signal clutter, although filtering can suppress it.
• Their height makes them obtrusively visible across large areas, disrupting the appearance of the landscape and sometimes creating local opposition.
• Downwind variants suffer from fatigue and structural failure caused by turbulence when a blade passes through the tower's wind shadow (for this reason, the majority of HAWTs use an upwind design, with the rotor facing the wind in front of the tower).
• HAWTs require an additional yaw control mechanism to turn the blades and nacelle toward the wind.
• In order to minimize fatigue loads due to wake turbulence, wind turbines are usually sited a distance of 5 rotor diameters away from each other, but the spacing depends on the manufacturer and the turbine model.

Vertical axis design

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically.

Advantages

• A massive tower structure is less frequently used, as VAWTs are more frequently mounted with the lower bearing mounted near the ground.
• Designs without yaw mechanisms are possible with fixed pitch rotor designs.
• The generator of a VAWT can be located nearer the ground, making it easier to maintain the moving parts.
• VAWTs have lower wind startup speeds than HAWTs. Typically, they start creating electricity at 6 m.p.h. (10 km/h).
• VAWTs may be built at locations where taller structures are prohibited.
• VAWTs situated close to the ground can take advantage of locations where mesas, hilltops, ridgelines, and passes funnel the wind and increase wind velocity.
• VAWTs may have a lower noise signature.^{[citation needed]}

Disadvantages

• A VAWT that uses guy-wires to hold it in place puts stress on the bottom bearing as all the weight of the rotor is on the bearing. Guy wires attached to the top bearing increase downward thrust in wind gusts. Solving this problem requires a superstructure to hold a top bearing in place to eliminate the downward thrusts of gust events in guy wired models.
• The stress in each blade due to wind loading changes sign twice during each revolution as the apparent wind direction moves through 360 degrees. This reversal of the stress increases the likelihood of blade failure by fatigue.
• While VAWTs' components are located on the ground, they are also located under the weight of the structure above it, which can make changing out parts very difficult without dismantling the structure, if not designed properly.
• Having rotors located close to the ground where wind speeds are lower due to the ground's surface drag, VAWTs may not produce as much energy at a given site as a HAWT with the same footprint or height.

Regards,

RS Sahni