Windmill Power output at specific size

[Generator]

Hello, it would be nice to list windmill sizes and power output you get under the fully loaded conditions at different wind speeds. Feel free to respond with your Windmill size, Power output when fully loaded and number of blades. Add extra columns you want.


         Windmill Diameter                       Power O/P under load                        Number of Blades                              Wind Speed     Volt Generated (V under load)
1]      8 ft                                             2000 Watt                                        16                                                    13 m/s            200 Volt (110 Volt)

[SparWeb]

I suppose I could put some numbers together. 
It's more important to include yearly energy production, measured by some reputable source.
Do you have that?

[clockmanFRA]

Depends what your future outcome is. ....

Do you want max output at any cost.

Do you want a machine that over a couple of years commits su..ide and disintegrates/ wears out because of insufficient materials.

I started in 2007 after extensive research.  I decided that 'Hugh Piggotts' & Dan 'Bartman's design' was a very well designed and proven Wind Turbines.

I have and seen small wind turbines from China just turn up their toes a few years later after install. 

I have 3off Hugh Piggotts design 12 footers (3.7m) diameter,  3 blades, at a build cost of $1200 each.  Each runs directly to a 48vdc large battery bank with diversion controllers.  There design is the sweet spot between wind speed and loading and generation speed, what i would call the perfect 'MACHINE'     and reaches my philosophy of 'KEEP IT SIMPLE', 'MAKE IT ROBUST', and importantly, 'KEEP IT COST EFFECTIVE'.

Yes, i have seen 3kW on each of mine for a brief second until they automatically turn from the wind, but in general i call them 1kW machines.  With a little maintenance each year they have been up 12 years, and probably get another 10 years.

Output figures in my experiences for most commercially manufactured domestic wind turbines i have seen in the last 10 years are grossly over exaggerated.

The below tables are from Hugh Piggotts book, and are about correct.     Thanks Hugh.

[bigrockcandymountain]

Yes, kwh per month and cost are the important things.  And production at 13 m/s is pretty meaningless. 

I make 1000w with my 13' dia at somewhere around 8 or 10m/s.  After that it furls but i do see peaks over 2kw.  More importantly, at 5m/s it makes around 400w.  There is where you make the power.

It does around 400 kwh per month in the winter months here which is a good location and very windy.  My #1 design parameter was robust, not performance or efficiency. 

[Generator]

Thank you All.

I mean to compare the maximum output at particular windspeed and not average over the period [I understand we always don't have wind flowing] . I'm asking this because at particular speed e.g. 13 m/s or 8 m/s how much your windmill model generates. That way I can compare it with my model. Also I wanted to know the output under fully loaded condition, so we know the Windmill actually delivers under load.

I measure my Windmill performance by towing behind truck, no wind here and no tower either. The purpose of this comparison is to claim that whether my model makes 20% or 200% more power than existing windmill models.

I suppose I could put some numbers together. 
It's more important to include yearly energy production, measured by some reputable source.
Do you have that?

[Generator]

Yes, I understand the robustness aspect. And also average energy production per month. But my purpose of these numbers are for comparison, so I can claim that my windmill model makes more or less energy than existing models.

Manufacturers do give number on their Nameplate, but we never get that much power from the windmill. e.g. I got $100 worth 1m windmill online, it said its rated 400W. When I ran it for up to 13 m/s, I got only about 40 watt at max... so I'm really interested to know why they rate it as 400watt. 

Yes, kwh per month and cost are the important things.  And production at 13 m/s is pretty meaningless. 

I make 1000w with my 13' dia at somewhere around 8 or 10m/s.  After that it furls but i do see peaks over 2kw.  More importantly, at 5m/s it makes around 400w.  There is where you make the power.

It does around 400 kwh per month in the winter months here which is a good location and very windy.  My #1 design parameter was robust, not performance or efficiency.

[MagnetJuice]

But my purpose of these numbers are for comparison, so I can claim that my windmill model makes more or less energy than existing models.
-----------
I have 8 ft ducted windmill with 16 blades.

Please give us more details about the Windmill that you are testing.

Some pictures will be very useful too.

Ed

[Generator]

It's simple ducted wind turbine. Same as you can see here youtu.be/PTnjTeutBtc
Only thing is I have 16 blades in it and diameter is 8 ft.

But my purpose of these numbers are for comparison, so I can claim that my windmill model makes more or less energy than existing models.
-----------
I have 8 ft ducted windmill with 16 blades.

Please give us more details about the Windmill that you are testing.

Some pictures will be very useful too.

Ed

[SparWeb]

The purpose of this comparison is to claim that whether my model makes 20% or 200% more power than existing windmill models.

Okay...

Windmill Diameter                       Power O/P under load                    Number of Blades                              Wind Speed     Volt Generated (V under load)
1]      8 ft                                             2000 Watt                                        16                                                  13 m/s              200 Volt (110 Volt)
2]      0.5 ft                                          6000 Watt                                         6                                                   13 m/s              460 Volt (230 Volt)

Mine makes 200% more than yours!

Proof:

[SparWeb]

Hey, Generator,
You're new here, and you may not get the joke.
We've been down this road before with others.
What you're writing is nothing new.
Just because you have a generator that pumps out kilowatts doesn't mean it will do it with any wind.
Sorry, but nature doesn't do you favours.


I know I know - you want to say that the Watts matters.
Yeah, it does... it gets people to buy stuff that doesn't work.
We smell the money incentive in the stuff you're writing.
We don't like the smell of snake oil.
And we call people out on it when we do.

[Adriaan Kragten]

Comparing windmills on the basis of the maximum power at very high wind speeds is completely useless as very high wind speeds happen only during a very low number of hours per year. What matters is the Pel-V curve which gives the electrical power as a function of the wind speed. Another very important figure is the wind speed distribution for the site where the windmill is placed. The wind speed distribution gives the number of hours per year for which the wind speed is within certain intervals. If you live in an area for which the wind speed distribution has a maximum for wind speeds in between 3 and 4 m per second, it is important that you select a wind turbine which has a high power for that low wind speeds. If you select a wind turbine which has only a high power at very high wind speeds, it may generate almost nothing at low wind speeds and the yearly output will be very disappointing. Information about this subject is given in the last chapters of my free public report KD 35.

[Generator]

Thank you for your comments Mr Adrian.

At the moment, My point is not to evaluate windmill for long term performance. My aim is to measure the output of Wind turbine and compare it with other wind mills. I understand wind doesn't flow all year long [or day]. What I'm saying is, let's say you have windmill of 8 ft diameter, it generates 100 Watt at 6 m/s wind speed under load (Without load it can generate 48 volts, but as soon as its loaded, it may give you only 24 volts or less). Now, if XYZ's windmill generates 1000 watt at 6 m/s wind speed, so doesn't it mean XYZ's windmill design generates 10 times more power than your windmill? So my aim is to compare the performance of Windmill for that particular wind speed only. Not for Year round performance. I haven't done anything special or extraordinary. I just added 16 blades instead of using 3 blades and also added shroud (total 8 ft diameter including duct, so actual blade diameter is only 5 ft). I also use 48 Volt generator, which is available in market and I have got 210 volts out of it. Under fully loaded condition I get around 110 volts from that generator at higher wind speeds.   

Comparing windmills on the basis of the maximum power at very high wind speeds is completely useless as very high wind speeds happen only during a very low number of hours per year. What matters is the Pel-V curve which gives the electrical power as a function of the wind speed. Another very important figure is the wind speed distribution for the site where the windmill is placed. The wind speed distribution gives the number of hours per year for which the wind speed is within certain intervals. If you live in an area for which the wind speed distribution has a maximum for wind speeds in between 3 and 4 m per second, it is important that you select a wind turbine which has a high power for that low wind speeds. If you select a wind turbine which has only a high power at very high wind speeds, it may generate almost nothing at low wind speeds and the yearly output will be very disappointing. Information about this subject is given in the last chapters of my free public report KD 35.

[Generator]

 

I got it when I saw the picture. All I'm trying to do is get the output from Windmill at particular speed [6 m/s or more]. The reason is I don't want to spend more money in making another Propeller as you guys have already done it numerous times.

The purpose of this comparison is to claim that whether my model makes 20% or 200% more power than existing windmill models.

Okay...

Windmill Diameter                       Power O/P under load                    Number of Blades                              Wind Speed     Volt Generated (V under load)
1]      8 ft                                             2000 Watt                                        16                                                  13 m/s              200 Volt (110 Volt)
2]      0.5 ft                                          6000 Watt                                         6                                                   13 m/s              460 Volt (230 Volt)

Mine makes 200% more than yours!

Proof:
(Attachment Link)

[Mary B]

Ducted mills have been discussed and tried and failed. 16 blades is just ridiculous... unless you want to pump water...

[Bruce S]

I'm curious enough to want to see a pic of the 16 blade ducted system  .

Bruce S

[MagnetJuice]

Generator,

I think that your desire to modify and test a particular Windmill design to try to improve it is commendable. A lot of us do that from time to time.

In my opinion, the way that you are approaching the members of this Forum is less than commendable.

When you make statements like this:

"But my purpose of these numbers are for comparison, so I can claim that my windmill model makes more or less energy than existing models."

"The purpose of this comparison is to claim that whether my model makes 20% or 200% more power than existing windmill models."

Those statements are not helpful.

You are trying to get members of this Forum to give you data so you can prove or claim that your Windmill is better than their Windmills. With that approach, I think you will get hostility and rejection from the members here.

I think that a better way to do it would be to tell us what you are doing.

Tell us what Windmill you have and show some pictures. Tell us the modifications that you have made to it, the tests that you have conducted and the results that you have obtained.

Give us some real numbers of the data that you have collected.

If you spend some time reading some of the posts here, you will discover that we are a Renewable Energy community that is interested in building things, sharing what we have learned and helping others when they ask for help.

I wish you success in your modifications and testing.

Ed

[Adriaan Kragten]

If you want to compare different rotors, you should compare the Cp-lambda curves as then you can compare rotors with different diameters. If you want to compare different generators, you should compare the efficiency-n curves for a certain load. So for an honest comparison of two different windmills, you should compare the product of the Cp times the generator efficiency. The Cp of the rotor at high wind speeds is strongly influenced by the safety system which limits the rotational speed and thrust at high wind speeds. So windmills without a safety system can produce a very high power at a wind speed of 13 m/s but they will crash at a wind speed of about 20 m/s. About 30 years ago, more than 10 people have built their own windmill in my region and we visited each others windmills. Only my windmill had an automatic safety system. After about three years all windmills except mine were damaged and some very dangerous accidents have happened!

The idea that the power of the rotor at a certain wind speed (so the Cp) can be increased by taking many blades, is a beginners mistake. Increase of the number of blades B has a positive influence of the maximum theoretical Cp but this influence is only large for values of B smaller than 3. The difference in between B = 3 and B = 6 is almost negligible. For a certain rotor diameter, design tip speed ratio and lift coefficient, you need a certain product of B * c (c is the chord). So if you compare a similar 3-bladed rotor with a 6-bladed rotor, the 6-bladed rotor will have half the chord. But this also means that the Reynolds value at a certain wind speed will be half and this has a very unfavourable influence on the aerodynamic characteristics of the used airfoil at low wind speeds resulting in a higher drag/lift ratio. The final effect is that the increase of the Cp because of using more blades is smaller than the decrease of the Cp because of a higher drag/lift ratio. Another disadvantage of taking many blades is that the blades become very slender and that the bending and torsion stiffness become that low than the blade becomes very sensible to flutter at high wind speeds. These effects are explained in detail in chapter 4 and 5 of KD 35. So I strongly advise to study KD 35 first and to design wind turbine rotors afterwards.

It is possible to increase the maximum Cp by using a ducted rotor. However, for a Cp higher than the Betz limit, the duct must be very large. The extra costs of such a duct are much higher than the extra cost of taking a larger rotor diameter. Another disadvantage of a duct is that the duct works as a vane and that therefore it isn't possible to limit the rotational speed and thrust by turning the rotor out of the wind. So you need a rotor with a pitch control system and that might be too complicated and expensive for a small wind turbine.

[Generator]

Thank you MagnetJuice, I appreciate your honest response and apologize for not posting the pics before asking the questions. However I did mention that it is simple Shrouded windmill with 16 blades. I'm not able to post the Links in this forum, so I did post the Youtube URL which was youtu.be/PTnjTeutBtc [I think you might have missed to view it]

Also I'm not trying to boast that My Windmill makes more power {I have seen 3 blade windmill making 3 kw made by James Biggar youtube.com/watch?v=ocVLS-0yDU8 Not sure whether it is under load}. I haven't invented anything or did anything out of the world. It's just experiment [out of curiosity] by adding more blades along with shroud.

I don't have extensive testing data like you guys have. I have done simple testing like towing windmill at 3 different speeds and measure the output with and without load. I don't even know the Cp, Reynolds number and other factors as Adrian mentioned.

I'll try to get the complete results at different wind speeds, when I get chance [maybe couple of weeks]. I'm about 1000 miles away from where the Windmill is.   

Generator,

I think that your desire to modify and test a particular Windmill design to try to improve it is commendable. A lot of us do that from time to time.

In my opinion, the way that you are approaching the members of this Forum is less than commendable.

When you make statements like this:

"But my purpose of these numbers are for comparison, so I can claim that my windmill model makes more or less energy than existing models."

"The purpose of this comparison is to claim that whether my model makes 20% or 200% more power than existing windmill models."

Those statements are not helpful.

You are trying to get members of this Forum to give you data so you can prove or claim that your Windmill is better than their Windmills. With that approach, I think you will get hostility and rejection from the members here.

I think that a better way to do it would be to tell us what you are doing.

Tell us what Windmill you have and show some pictures. Tell us the modifications that you have made to it, the tests that you have conducted and the results that you have obtained.

Give us some real numbers of the data that you have collected.

If you spend some time reading some of the posts here, you will discover that we are a Renewable Energy community that is interested in building things, sharing what we have learned and helping others when they ask for help.

I wish you success in your modifications and testing.

Ed

[Generator]

Yes, one of the use case is Pumping water. Specially in underdeveloped countries. Where wind never goes beyond 25 - 30 mph and have unreliable power supply [or not at all].

Ducted mills have been discussed and tried and failed. 16 blades is just ridiculous... unless you want to pump water...

[Mary B]

They are STILL used for pumping water all over the USA! Some in places with VERY high winds like where I live(average 18mph, 60+ is common, 90+ 2-3 times a year).

[Generator]

Adrian, I'm unfamiliar with Cp, Reynolds numbers and other factors. Also I won't be able to measure those things. All I have done is only measure the output for 3 speeds with and without loads.
But I'll try to get better video and picture soon and post them. Currently I'm far from the windmill location but the windmill is based on this design youtu.be/PTnjTeutBtc .

I understand the Safety concerns and all those things but for now I'm just experimenting with it.

If you want to compare different rotors, you should compare the Cp-lambda curves as then you can compare rotors with different diameters. If you want to compare different generators, you should compare the efficiency-n curves for a certain load. So for an honest comparison of two different windmills, you should compare the product of the Cp times the generator efficiency. The Cp of the rotor at high wind speeds is strongly influenced by the safety system which limits the rotational speed and thrust at high wind speeds. So windmills without a safety system can produce a very high power at a wind speed of 13 m/s but they will crash at a wind speed of about 20 m/s. About 30 years ago, more than 10 people have built their own windmill in my region and we visited each others windmills. Only my windmill had an automatic safety system. After about three years all windmills except mine were damaged and some very dangerous accidents have happened!

The idea that the power of the rotor at a certain wind speed (so the Cp) can be increased by taking many blades, is a beginners mistake. Increase of the number of blades B has a positive influence of the maximum theoretical Cp but this influence is only large for values of B smaller than 3. The difference in between B = 3 and B = 6 is almost negligible. For a certain rotor diameter, design tip speed ratio and lift coefficient, you need a certain product of B * c (c is the chord). So if you compare a similar 3-bladed rotor with a 6-bladed rotor, the 6-bladed rotor will have half the chord. But this also means that the Reynolds value at a certain wind speed will be half and this has a very unfavourable influence on the aerodynamic characteristics of the used airfoil at low wind speeds resulting in a higher drag/lift ratio. The final effect is that the increase of the Cp because of using more blades is smaller than the decrease of the Cp because of a higher drag/lift ratio. Another disadvantage of taking many blades is that the blades become very slender and that the bending and torsion stiffness become that low than the blade becomes very sensible to flutter at high wind speeds. These effects are explained in detail in chapter 4 and 5 of KD 35. So I strongly advise to study KD 35 first and to design wind turbine rotors afterwards.

It is possible to increase the maximum Cp by using a ducted rotor. However, for a Cp higher than the Betz limit, the duct must be very large. The extra costs of such a duct are much higher than the extra cost of taking a larger rotor diameter. Another disadvantage of a duct is that the duct works as a vane and that therefore it isn't possible to limit the rotational speed and thrust by turning the rotor out of the wind. So you need a rotor with a pitch control system and that might be too complicated and expensive for a small wind turbine.

[Generator]

Interesting, because I didn't get chance to see one in person. Would love to. But don't you think if someone comes with better performance for same size windmill, there is market for it? Not sure people still buy Windmills for Water pumping or going Off grid, but in either case, if people see better returns for investment, they may start buying them again.

They are STILL used for pumping water all over the USA! Some in places with VERY high winds like where I live(average 18mph, 60+ is common, 90+ 2-3 times a year).

[MagnetJuice]

Generator, I want to welcome you to the Forum and I encourage you to stick around here, we like experimenters because that is how new discoveries are made.

Even if there are no discoveries or breakthroughs, we always learn something new and have fun doing it.

Failures are also good teachers, because it keeps others from trying things that don’t work.

You can post pictures anytime, and you will be able to post links after you have 20 posts.

Ed

[Adriaan Kragten]

Adrian, I'm unfamiliar with Cp, Reynolds numbers and other factors.

[/quote]

That's a lazy argument. When I started with wind energy, almost 45 years ago, knowledge was very difficult to obtain. So at that time, designing wind turbine rotors was a process of try and error. But if you spend a half day in studying my report KD 35, you have the required knowledge to design a wind turbine rotor according to the aerodynamic theory. So then you won't make fundamental mistakes and you will better understand discussions on this forum. The knowledge in KD 35 is given as simple as possible and is the result of a long period of development starting in 1926 by Betz who derived that the absolute maximum value of Cp is 16/27 = 0.59.

[Generator]

Ir. Adrian, I have tremendous respect for you. For your work and the way you have made it public. It's generations of the work put in your website/reports. It will take a little time for me to understand Reynolds number and some other concepts (I'm still reading your report). But let me share you my thought/doubts, which might be weird. I never had formal education in Aerodynamics and I didn't have anyone worthy to ask the questions to. Anyways, I'm happy to be in contact with you guys, who knows Wind Turbines inside out.

The theory you have or everyone learnt/evaluated is based on Propeller behavior in free flowing fluid. How votex is created, how speed affect the propeller rotation and things like that. If we change the propeller geometry to let's say vertical axis wind turbine or spiral or Archemedes wind turbine etc, do we still follow the same principles of Reynolds number, tip speed ratio, furling effects, blade stability/strength and so on? 

Here is one of the design from Netherland, just in case you have not seen it before...

thearchimedes dot com
thearchimedes dot com/images/pdf/AWM-Brochure%20Eng%20small.pdf

That's a lazy argument. When I started with wind energy, almost 45 years ago, knowledge was very difficult to obtain. So at that time, designing wind turbine rotors was a process of try and error. But if you spend a half day in studying my report KD 35, you have the required knowledge to design a wind turbine rotor according to the aerodynamic theory. So then you won't make fundamental mistakes and you will better understand discussions on this forum. The knowledge in KD 35 is given as simple as possible and is the result of a long period of development starting in 1926 by Betz who derived that the absolute maximum value of Cp is 16/27 = 0.59.

[Mary B]

Yes they apple to vertical designs also. And no vertical is as efficient as a horizontal axis wind turbine. Nature of the beast... on the VAWT you have upwind blades causing wind shadow of the downwind helping create drag(simplified explanation, other factors also play into it...)

[MagnetJuice]

The theory you have or everyone learnt/evaluated is based on Propeller behavior in free flowing fluid. How votex is created, how speed affect the propeller rotation and things like that. If we change the propeller geometry to let's say vertical axis wind turbine or spiral or Archemedes wind turbine etc, do we still follow the same principles of Reynolds number, tip speed ratio, furling effects, blade stability/strength and so on? 

Those are very good questions and the answers are not clear yet. I think that it is going to take a lot of experimentation and testing to find answers to them. I am glad that you are doing some testing on a ducted turbine.

In this video, Professor Visser sheds some light on the ducted turbines and talks about the work that he has been doing.

https://www.youtube.com/watch?v=EXxA-RkwuRY

For the moment, I am concerned about the way that you are testing turbines.

I believe that towing a turbine on a trailer behind a vehicle is not the best way to do it.

The vehicle in front of the turbine is creating disturbances in the wind flow that are unpredictable. The turbine could either be in a wind dead zone or be exposed to exaggerated wind speeds like a jet stream.

The results that you get could be inaccurate and misleading.

That could explain why the smaller turbine that you tested only produced 40 watts.

Look at this video and you can see what I am talking about.

https://www.youtube.com/watch?v=pplOtFq_2PY

Ed

[Generator]

Yes I understand the turbulence created when we Tow the windmill, but we used smaller vehicle (off road 4 wheeler to tow) and kept the Small Wind Turbine at 10 ft higher position, so no turbulence is affecting its performance.

For the bigger windmill I have, it surely gets some disturbance / turbulent wind flow because of the vehicle in front of it, but the distance between mill and vehicle is about 8-10 ft away so I assume it gets about 80% good wind flow.

I have gone through the Clarkson video and their performance claims. Unfortunately that windmill was not adapted by customers even it claimed twice better performance than existing turbines. So sometime I wonder, even if we build wind turbines, which can generate 2-3-4 times more power than traditional windmills, do we have customers, who will buy it? Because I think Clarkson Windmill has got Zero commercial customers and they have launched it 2-3 year back.

This raises another concern "Is there customer for Wind Turbine, even if we make 2 or 4 times more power than existing windmills, which can work in 1 m/s to 3 m/s wind speeds?"

For the moment, I am concerned about the way that you are testing turbines.

I believe that towing a turbine on a trailer behind a vehicle is not the best way to do it.

The vehicle in front of the turbine is creating disturbances in the wind flow that are unpredictable. The turbine could either be in a wind dead zone or be exposed to exaggerated wind speeds like a jet stream.

The results that you get could be inaccurate and misleading.

That could explain why the smaller turbine that you tested only produced 40 watts.

Look at this video and you can see what I am talking about.

Ed

[SparWeb]

Hi Generator,
I can't help but notice, you are asking questions rather than doing the work.  This site is committed to DIY which means Do It Yourself. 
We can help you and guide, you but the ratio of effort needs to be 99% yours / 1% ours for you to really be successful.

I spent years self-teaching so that I could do the math to understand the aerodynamics because I wanted to know.  Now that I've done it I know what a specious claim looks like and I can build my own WT's with confidence that I'll get good performance.  If you want this level of knowledge, you must do the work. So has Adriaan, and some others who frequent this site, who are willing to share info and resources.  But don't make it a drag for us assuming you can ask 100 questions, expect 100 answers, all for free.  DIY is not spoon-feeding. Not when the information you need is easy to find and has already been pointed out to you.

[clockmanFRA]

Yes, SparWeb,

These last few years i have seen a lot of highburbly waffle on renewable energy subjects, where a certain type of person believes he can solve an issue without actually doing it, and very importantly to this person he can make money at it by teaching others.

In my opinion, 'Mining for information' for eventual comercial explotation by the Miner is getting worse.

On another forum i frequent there has been some questions asked about Lithium battery packs for off gridders. 2 members replied that have true EMPERICAL evidence with some real good working points that even i had to copy down for my possible Lithium pack one day.   

Anyway, the original poster turned out to have created a comprehensive Solar Web site in the Wikipedia format, and then informed me that he was selling small off grid system's to the developing World.

   Looking closely at his web site there was the standard stuff all quoted from normal sources, so nothing new.   However he asked me my opinion on his site, i replied that there was no mention of AC Coupling. 

 There was no knowledge on the subject and he replied " Far to complicated and i only deal with supplying the developing World". 

So Yes 'SparWeb', always a difficult call to know when your being taken for a ride, by folk climbing on the backs of others who actually want to try to help.   

[Adriaan Kragten]

The theory you have or everyone learnt/evaluated is based on Propeller behavior in free flowing fluid. How votex is created, how speed affect the propeller rotation and things like that. If we change the propeller geometry to let's say vertical axis wind turbine or spiral or Archemedes wind turbine etc, do we still follow the same principles of Reynolds number, tip speed ratio, furling effects, blade stability/strength and so on? 

[/quote]

The theory of Betz is valid for any kind of wind turbine. Betz even didn't specify the kind of wind turbine. He only assumed a devise which extracts energy from the wind and which has a rotor through which an air flow is possible. So also for a VAWT, the maximum power is generated if the wind speed in the rotor plane is reduced up to 2/3 of the undisturbed wind speed. Figure 4.1 out of KD 35 shows the expanding wake. If you would made a duct around the rotor with this shape, nothing will change. To realize a substantial increase of the mass flow, the duct must widen strongly after the rotor up to a diameter of about three times the rotor diameter and it must have a nice rounded inlet. Small ducts give no increase of the mass flow but only reduce the tip losses.

The load working on the blades of a VAWT like Darrieus rotor, is continuously changing and therefore these turbines are sensible for vibrations. Information about this subject is given in my public report KD 601.

The definition of the tip speed ratio lambda and Reynolds is valid for all kind of rotors but for Reynolds you have to take the relative wind speed felt by the airfoil.

For pure drag machines, there is no flow through the rotor and for such devices, you get the maximum power when the speed of the cup is 1/3 of the wind speed. The maximum Cp is very low. information about drag machines is given in my public report KD 416.

I am a mechanical engineer on HTS level (kind of bachelor) with the Dutch title ing. Ir. is the title when you have a university degree.

[Generator]

Thank you Ir Adrian. I think it is same as Er = Engineer. But in anyway, you know more than any Engineer or PhD person from the work I have seen.

I was building a bigger version on the wind turbine, but somehow stopped working on it for various reasons. One of it was same concern I raised in my last post. Even if we make better windmill, will people buy it?  I never completed it. But I'm thinking to restart the work again. Posting old picture of unfinished ducted turbine for reference. It's rusting since long and you can see Bamboo tree has grown inside it now [It will give you an idea of the size too].

Surely the purpose is to commercialize the Windmill, if it becomes successful. But in that case if it is not advisable to post or ask questions in this forum, then I won't bother you guys or waste your valuable time.

Sadly, the Only way for me to evaluate my windmill is then build multiple windmills and compare them side by side, if none of the member is willing to share their numbers.

The theory of Betz is valid for any kind of wind turbine. Betz even didn't specify the kind of wind turbine. He only assumed a devise which extracts energy from the wind and which has a rotor through which an air flow is possible. So also for a VAWT, the maximum power is generated if the wind speed in the rotor plane is reduced up to 2/3 of the undisturbed wind speed. Figure 4.1 out of KD 35 shows the expanding wake. If you would made a duct around the rotor with this shape, nothing will change. To realize a substantial increase of the mass flow, the duct must widen strongly after the rotor up to a diameter of about three times the rotor diameter and it must have a nice rounded inlet. Small ducts give no increase of the mass flow but only reduce the tip losses.

The load working on the blades of a VAWT like Darrieus rotor, is continuously changing and therefore these turbines are sensible for vibrations. Information about this subject is given in my public report KD 601.

The definition of the tip speed ratio lambda and Reynolds is valid for all kind of rotors but for Reynolds you have to take the relative wind speed felt by the airfoil.

For pure drag machines, there is no flow through the rotor and for such devices, you get the maximum power when the speed of the cup is 1/3 of the wind speed. The maximum Cp is very low. information about drag machines is given in my public report KD 416.

I am a mechanical engineer on HTS level (kind of bachelor) with the Dutch title ing. Ir. is the title when you have a university degree.

[Scruff]

So Yes ... always a difficult call to know when your being taken for a ride, by folk ...   

I get A BS-o-meter trip at the mention of "game-changing", "linch-pin", Tesla (corporate), "missing link", wind turbine ducting, rooftop turbines, on-shore vertical mounted Solar, mosts VAWTs, rebuttals like that's how it's always done / people are using it so QED.

AC coupling ain't hard. It was "invented" by back-feeding a low-frequency charger/inverter with a synchronised phase.
Controlling it is the difficult part.


Solar freakin' battery heaters bro!