I am 71 years old now and in December 2017 I have ended the commercial activities for my engineering office Kragten Design. But I am still active and my website: www.kdwindturbines.nl will be maintained as long as possible. In the first half year of 2018 I have written five new free public KD-reports. Four of these reports give rotor calculations. At the menu “News” on my website you find a short description of the content of each report. At the top of the menu “KD-reports” there is the folder: “List free public KD-reports” and the folder “Sequence of KD-reports for self-study” which, I think, will be of great help for someone who wants to design a wind turbine.
Thanks Adriaan. This is a wonderful resource for students of wind turbine design. Here is a chart from KD35 showing the relationship between conversion “efficiency” and drag/lift ratio, over a range of tip speed ratios:
My friend Jamie is moving on from his off-grid house so I am posting details. This house is powered by a PowerSpout turbine and a PV array.
Knoydart, Mallaig, PH41 4PL
“No 2 Doune is in a small cluster of houses, one of four private dwellings, overlooking Doune Bay on the Knoydart peninsula. The house is in a spectacular setting, positioned against the hillside and with stunning views over the sheltered bay and the Sound of Sleat to Skye. ” More here.
ERNI e.V., www.erni-kollektiv.org together with the Dieter-Kaltenbach-Stiftung conduct a 6-day-workshop for a 2F HP Turbine from 23rd to 38th June in Lörrach, Germany.
Application is available here: https://www.kaltenbach-stiftung.de/kategorien/vhs-kurse/vhs-werken/2688-bau-einer-kleinwindkraftanlage/
Costs: 400€ for all 6 days
I got an email question today and it seems important enough to answer with a new post. Here is the question “How many amp of 14,15,17,18 and 20 awg wire for wind turbine. Can you give me any chart? Please!!!!! ”
If you are winding a stator according to my style – about 13mm thick coils with some glass cloth on the faces and plenty of wind blowing past it – then my rule of thumb is about 6A RMS current per sqmm of wire cross section. If the stator is star/wye connected, with a single wire in hand and all coils in series then the DC output will be about 22% higher than the RMS AC current.
The relationship between AC current in each phase and the DC output of the rectifier depends on the waveform. But the simplest way to think of it is to say that each wire carries the full DC current for 2/3 of the time, and is resting for 1/3 of the time. The result is that the rms AC current in each wire is root(2/3) = 0.82 times the DC current. In reality the wires share current some of the time, so the % is very slightly lower in relation to the DC. But this 0.82 is the worst case, and it is very close to the reality usually.
So maximum DC current should be about 1.22 x maximum allowed AC current as in the table.
So here is my answer:
It’s OK if the current surges way above this value in a gust, but this is the maximum sustained current I would design for, as a safe target. Your furling tail should prevent the machine from kicking out more than this on a continuous basis. If output is higher then make the tail lighter to reduce amps.
I used to teach blade design. I went to Wales to learn (more) about windpower on a course (in about 1989), but the guys there made me teach the session on blade design. They just announced that I would do that class and sat down. That was scary.
I kept on going back down there and helping with the courses for years, and so ten years or so later my blade design lecture got to be recorded in a PDF (which was a pretty novel thing at the time). You can find this PDF on my old website here.
Today I found out that the notes have been translated into Russian. That’s cool 🙂 I love the Russian language although I have not tried to understand it since I was at school. I am glad nobody is asking me to teach blade design in Russian(!), but if they did I would at least have the notes to make a powerpoint for the class.
(ERNI e.V., www.erni-kollektiv.org) together with the VHS Braunschweig conduct a 5-day-workshop for a 2F HP Turbine from 14th to 15th May in Braunschweig, Germany.
Application is available here: https://www.vhs-braunschweig.de/die-vhs-braunschweig/kurssuche/kurs/Workshop-zum-Bau-einer-Kleinstwindkraftanlage/nr/BMUB01/bereich/details/
Costs: 70€ for all 5 days
Information flier here
hello again from Wyoming.. The larger wind generator at 45 mph + winds is doing a whooping 150 to 200 amps. 24 volts battery bank.
Maybe would do more, but tail cuts out of wind after 45 or 50 mph winds.
The machine probably does 44 volts at a higher output. Battery bank voltage is 28.2. i guess the loss in the wire is the resistance.
I used the same magnet as you used on your 8ft turbine, 1/2″ x 1 ” x 2″ . And used 40 copper coils, 20 inner coils and 20 outer coils. 17 gauge wire, 150 turns. Resin thickness 3/4″. Inner coils are off set from outer coils, but magnets are in line so to make it smoother turning, and it was. Inner coils are together with 1 neutral ring. And outer coils are isolated from the inner coils with there own Neutral . It seems that the inner coils start to make power a little sooner than the outer coils. Same amount of magnates passing the coils on both inner and outer of the stater, but the inner coils are a little closer together than the outer coils because of diameter. But the volt is not much different, maybe 2 volts. I guess the phase lag is different than the other. But is seems to work good. SO 20 coils are hooked to a neutral and the other 20 coils are hooked to a neutral . 40 WIRES are a lot to hook up to the 20, 10 amp rectifier that are on a aulimum heat sink. I wish i would have used bigger rectifiers but i thought i it was only going to make MAX 120 amps. i was wrong. it makes much more.But thank God that they hold up Ok. With a RPM meter, a little hand held one that i have with a lazer and a sticker you put on it. At 90 rpms it produced 24 volts. Blades seem to work well with the gen. At around 5 mph it is making around 4 or 5 amps. Sometimes it takes 6 mph wind to start the turbine, but sometimes much less like 3mph.
With that much power, i was concerned about heat produced, so designed it so air flow can get through coils for better cooling.
In the middle of coils i used tapped wood block that was waxed, and screw to hold it in place. Then before i poured it, i put tape on top, so resin would not get in there, and leave a hold for more cooling on high out put. The small wood blocks must be tapped and waxed so they can be removed after screw is removed.
I got this from Kostas today:
OpenAFPM: An open source software tool for modelling and designing axial flux permanent magnet generators in wind electric systems
Update THERE WILL BE A WEBINAR ON 19th April where you can learn how to use the tool. More information here.
The OpenAFPM modelling tools can be used for designing Axial Flux Permanent Magnet (AFPM) generators for wind electric systems with the use of the open source finite element analysis software ‘Finite Element Method Magnetics’ (FEMM). This series of design tools have been developed by the Rural Electrification Research Group (RurERG), which is part of the Smart RUE (Smart grids Research Unit of the Electrical and Computer Engineering School) of the National Technical University of Athens (NTUA), in order to assist designers and practitioners involved with small scale wind electric systems.
The OpenAFPM tools series consists of three design tools named MagnAFPM, UserAFPM and OptiAFPM. The tool MagnAFPM can be used for designing a generator for a specific set of rotor blades and a specific set of permanent magnet dimensions. The tool UserAFPM can be used to validate the performance of a specific generator geometry by performing a finite element analysis using FEMM. The tool OptiAFPM uses the particle swarm optimization (PSO) to optimize the dimensions of the permanent magnets used in the generator design for a specific set of rotor blades, while minimizing the generator’s efficiency, cost and/or mass.
The creation of the online user interface of the OpenAFPM modeling tools has been supported by WISIONS as part of the project ‘Online Design Tools for Locally Manufactured Small Wind Turbines’.
Follow the link to visit the home page of the OpenAFPM tools and try them out!
There are several wind turbine construction courses happening around the world in March and April.
The Handy Village Institute is preparing for their third Homebrew Wind Turbine Workshop, with Dan Bartmann as guest instructor, March 19-24, 2018, near Saxapahaw, North Carolina 27253, USA.
Details and registration information: handyvillage.com.
500RPM are holding four classes in Buenes Aires on 3,4,10 and 11th March
Tripalium are holding 3 courses in April in France and Portugal and plenty more thereafter. The workshop in Portugal 16-20th April will be conducted at least partly in English.
V3 Power will be holding a workshop at CAT Sat 28th – Sun 29th April 2018
I try to keep my list of courses updated. Click the link for “courses calendar” in the black menu bar above.
I have been disturbed to learn that some emails sent to me have not arrived and my provider has not been able to explain or fix the issue yet. So if you are trying to get in touch and have not had a reply then it is possible your message has got lost, sorry.
I always reply to emails. If you get no reply then please try my gmail address which is scoraigwind”at”gmail.com. (Insert @ for “at”)
Please also mention to me if you have had problems with my usual
address, and if possible send me extra details, such as any failure messages you got back. Thanks.