# Wind turbine placed on a barge, stability calculation

Discussion in 'Stability' started by helleik, Aug 8, 2016.

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### helleikNew Member

Hello

I am currently writing my MSc thesis where I'm looking at renewable energy solutions for the salmon farming industry in Norway.

One solution is to place a wind turbine on the excising feed barge that all salmon farms have. (See attachments for info on a typical feed barge) The question is then, how big could the wind turbine be without causing the barge to become unstable?

I have found some information on stability calculations: http://hawaii-marine.com/templates/barge_trim_list_stability.htm However, I have a hard time doing the calculations, as my field is electrical engineering. Also I think my fleet specifications are missing many of the required parameters.

Is there any simple calculations I can do to prove that a certain wind turbine size would not make the barge unstable?

A relevant wind turbine could be a 100kW turbine, with a tower height of 30m. The weight of a turbine like this would be 7.5 tons, and the rotor diameter 25m. My plan for calculating the sideways forces on the wind turbine is to simplify and look at the rotor as a disk.

Does anyone have any inputs of how a problem like this could be solved?

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### mudsailorJunior Member

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### daiquiriEngineering and Design

Helleik,
It is not a particularily difficult problem. For sure it should not be a difficult problem for someone who has arrived to the point of writing a MSc thesis.

You need to find and review the technical literature which treats the following issues:
1) Design of wind turbines with actuator-disc model.
2) Theory of gyroscopes
3) Stability of barges
It is a research you have to do by yourself, that's the point of writing a research thesis. Don't rely on the info given by random persons in an internet forum, because you will have to include a list of reference papers at the end of your work. Declaring "www.boatdesign.net" as a reference is not appropriate, with all due respect to this forum.

Just few more hints for you:
1) The actuator-disc model (ADM) will give you a V_wake/V_inf ratio for an aerodynamically optimum turbine. This is not necessarily the economically optimum turbine. You should investigate the difference between the two concepts.
2) The V_wake/V_inf ratio for the Betz efficiency from the ADM equals 1/3. The optimum V_wake/V_inf ratio for real turbines will be in that ballpark, but the actual efficiency is 55%-65% of the Betz value.
3) Barges are wall-sided hull forms. Check out what it means for you.
4) Although relatively small, gyroscopic effects should be investigated too, in order to verify and demonstrate that they are small indeed.

Once you have put together the knowledge gathered through studying these subjects, you will be able to create a step-by-step procedure for the required calculations.

Cheers

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### Mr EfficiencySenior Member

Is it really that simple ? The effect of big seas would seem to complicate matters.

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### daiquiriEngineering and Design

But it is intended for salmon farms, and it is a barge.
Hence it will work in sheltered waters, as I understand it.

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### DouglasEaglesonJunior Member

Comment on Wind Mill Technology

I am interested in resurrecting wind mills as opposed to wind turbines.

I have a blog: http://douglaseagleson.blogspot.com

Scroll down to the wind mills post.

wiki makes the comment that wind turbine theory is complex. My design is a literal constant airfoil wing on extension struts. It is not the constantly changing airfoil section of modern wind turbines.

My comments purpose is to encourage the reader to think. Before a real wind farm is made I believe the experimental comparison between turbines and mills is completed.

thanks doug

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### gonzoSenior Member

Constant airfoils are only used in elementary school science projects. Their efficiency is very low, so they are a waste of time and money to scale up. I agree that you can do a first approximation not considering any waves. The calculations for the forces is the same as that for wind turbines installed on shore. They are easily available for many engineering texts and other published data. You can then use that input to calculate heeling angles on the barge. The stability problem can be lessened by installing a vertical shaft that drives a generator installed on the barge's deck. However, there will be some gearing losses of about 3% or so.

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### DouglasEaglesonJunior Member

on my blogspot I mentioned the concept of the required number of blades. It is obvious that for cost efficiency the number of blades is to be maximal. What this means is that if a turbine designer selects a two blade turbine they are wowfully incompetent.

If they want to sell a lot of towers and generators then use two if the buyer will accept

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### gonzoSenior Member

I can't really understand your sentences. What does it mean that :"It is obvious that for cost efficiency the number of blades is to be maximal"; the maximum would be infinite, or a circle. Further, turbines can not be incompetent, only people can. Are you familiar with the maximum power a turbine can generate according to Betz's law or the aerodynamics of revolving foils?

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### philSweetSenior Member

Douglas, the 19th century called, they want their machine back.

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### philSweetSenior Member

Okay, a bit more seriously, the blade tip power system can work well with a high blade count.

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### gonzoSenior Member

They are used to limit the diameter, but they are not very efficient. The blades interfere with each other. The design of blades has evolved to the point that there are only small refinements being made. Some approaches, like dynamic camber controls, can provide more efficiency over a larger range of wind speeds.

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