New blades capture 99% of next to no power in the city

Screen Shot 2017-01-19 at 13.54.23

An article has just come out in Engineering and Technology  describing how new super-efficient blades are going to make it viable to put wind turbines in the city.

“Small wind turbines (like the one pictured above) are often installed in urban and semi-urban areas. However, these locations are challenging as they require turbines that work at variable, often low, wind speeds while running smoothly and producing little noise. These conditions directly affect the technical requirements for wind turbine generators.”

This shows a profound misundertanding of the problem.  The reason why small wind turbines do not work in the city is not for lack of clever gimmicks such as ducting shrouds and fancy analysis. The reason is that there is hardly any energy there to capture.  Improving the efficiency is not the solution.  Capturing a higher % of next-to-nothing will still produce next-to-nothing.

This sort of article is misleading because it suggests that the reason why small wind turbines have not worked in the urban environment is lack of development of the technology.  Actually the reason is that this is the wrong application of the technology.  The technology is mature but in order to work it needs a proper wind resource.  This is not available in the city.  This article with its apparent engineering background lends legitimacy to misinformed people who buy and sell equipment that purports to usefully generate power in the city.  This is a waste of resources that also gives renewable energy a bad name.

Posted in Rooftop madness, UK small wind scene | 2 Comments

Secondhand wind turbine stuff

Joff in Cornwall still has some secondhand stuff available.  I posted about this in 2014 here.  Some of that excellent stuff remains and he is keen to give it to a good home:

A couple of years ago, with your help I did manage to sell a few parts of my broken Eoltec turbine.  So thanks for your help with that.   Time has passed,  the financial loss is more distant, and I’ve been lazy about shifting the remaining parts. 

But now  it’s time to get rid of the rest.  Obviously demand is not high,  but the parts may be of some use to somebody and I’m not asking for any money.

What I still have left is;   a 12m galvanised tower,   2  Aurora invertors and various bits of switch gear and a transformer.

I’d be grateful if you could put the word around again.

Contact me or comment here and I will pass your enquiry on to Joff.

Posted in stuff on offer | 3 Comments

Workshop selfie video winding a coil

I don’t put enough of the stuff that goes on in my own workshop onto this blog so here is a workshop session where I am winding a coil for a repair for a big machine, and I talk through the process a bit as I go.


Posted in construction, my own projects, Video links | Leave a comment

Eolocal video

Here is a nice video from Eolocal in Argentina:


Posted in Video links | Leave a comment

What is it about Vertical Axis?

It has been a while since I posted about vertical axis, but I can’t help noticing that everybody wants to do it, and they keep asking me for help.  I get emails, and people put comments on this blog.  They all think there is some advantage to using a vertical axis turbine.  I don’t know what advantage there can be.  Please help me understand!

“VAWTs don’t need towers.”  Hmm.  Why don’t they need towers?  Can they work in places where there is no wind?  The reason we put wind turbines on towers is because wind turbines need wind.  In spite of what you may read on the internet, modern wind turbines are pretty efficient already, and do not need to be re-invented.  What they mostly lack is wind.  A 10% increase in windspeed gives 33% more energy.  How to get more wind?  Use a tall tower.  Windspeed increases with height.  There is no useful wind in a backyard or under a tree.  The only reason that VAWTs do not need towers is that they are not wind turbines for producing energy.  They are just greenwash ornaments for architects to use to tick boxes about footprints.  Performance claims for VAWTS are invariably inflated.  Pretty often they use more energy than they generate.  It takes power to motor a VAWT up to speed and this is a waste in a lot of places because they do not have a tower, so they will never see a proper wind.

“They are silent in operation”  OK I admit I have never actually heard one running.  But the noise most people notice from small wind turbines is alternator whine and I see no reason why being vertical would change that.  For me it’s music anyway.  Blade noise depends on speed of movement and is mostly white noise that is easily masked by other sounds.


Windside Savonius turbines made in Finland are very beautiful.

I will admit that Savonius rotors turn so slowly that they could be silent.  That’s a lovely looking type of VAWT but so slow and inefficient that the energy it makes is very expensive.  They turn at low rpm and so they need a heavy alternator which is expensive.  That’s one reason why modern HAWTs have fast-running blades.

I’d love to see them around the place but in reality solar is so much cheaper that they would only be ornaments.

“They don’t kill birds.” In forty odd years of living and working under small wind turbines I have only seen two dead birds.  A lot more have been killed by the flying into the window of my office.  Not to mention my cat…  Anyway why should birds be less likely to be killed by a VAWT?  Because they stand still mostly?

“They are more efficient than HAWTs.” There is no way that a VAWT can be more efficient than a HAWT.  The blades spend about half their time moving in the wrong direction for a start.  I have never seen evidence of higher efficiency and I have never heard any expert give a reason why they should be more efficient.  For some reason VAWT manufacturers are even more prone to exaggerating performance than HAWT manufacturers.  Don’t believe either of them!  Look for independent test data.  Good luck with finding a VAWT that has been independently tested and comes with a performance report from NELSWCC or NREL etc.  Well to be honest the Quiet Revolution shown above has been tested but the results are secret and the turbine is no longer listed as MCS approved.  More about QR..

“You are obviously biassed against VAWTs and your mind is closed to new ideas.” This is what people say to me.  It’s true that I have never seen the point of VAWTs but my mind is open.  I really hope to hear from people who have owned VAWTs and produced a lot of energy and the blades did not fall off, and they are happy.  Please get in touch with me!  I need educating.  All I ever see is bad news, and the same old misleading hype.  Lets get some good news out there!

I am happy to help people who are building VAWTs by suggesting how they can make their own alternators.  I do get a lot of enquiries about this.  One thing I do ask is please could you find out the range of rpm and power in relation to windspeed?  You will need to know the “tip speed ratio” and the “power coefficient” of the turbine.  Then we can determine the output of the turbine in watts and its best rpm at each of a range of windspeeds and go to work.  Nobody who asks me seems to have a clue about these facts.  Again – I need educating!  Please VAWT builders do find out the performance parameters of the design based on past experience.  VAWTs have been built for a hundred years and more.  There must be some data out there.  Please could people learn from the disastrous history of the vertical axis wind turbine, and then go forward with eyes open to the  realities?

Early Darrieus turbine of the “egg beater” type

“What’s wrong with vertical axis?” I almost forgot to say so I am glad you asked me that.  OK so there’s not much wrong with the Savonius rotor except that it’s grossly inefficient and runs much too slowly for generating electricity, but it is rugged and simple and a lovely thing to look at.   When we look at high speed VAWTs of the “Darrieus” type then it’s important to understand the issues there.

It’s interesting that the wikipedia page for the Darrieus does not mention the most important word in connection with this turbine type which is fatigue.   The blades are subject to reversing lift forces in every single revolution and that amounts to a fatigue machine that ultimately breaks the blades or their fixings.  The ones that do not have helical blades also put horrible fatigue loads into the supporting structure (if there is one) so it is impossible to design a suitable tower.  I am told that these are “just a materials problem” but you’d better solve that because it is the death of most VAWTs.  Oh, and even the electrical network has to deal with pulsating power coming in.

Also the Darrieus design is not self starting so you will need to figure out a way to start it up.  Although it can start in turbulent conditions when you least expect it so if you want to keep it stopped you’d better have a brake.  You are going to need that brake in strong winds because there is no effective pitch control system that is not going to wear out.  Maybe you can use a big alternator and stall it so long as the wind does not get too strong.

What else is wrong?  Cantilevered loads on the bottom bearing can be an issue.  It’s probably worth using guys to the top of the machine.

I think there were a few more issues that I forgot.  But then I completely forgot the entire  list of reasons for doing this in the first place.  Can somebody tell me?  Why vertical axis?  I simply don’t get it.

Posted in Vertical axis wind turbines (VAWTs) | 26 Comments

Windempowerment maintenance manual for Recipe Book turbines


have published a Maintenance Manual for my wind turbine designs,
in free PDF download format.
(Donations are also welcome.)

Particular thanks to Gael Cesa
of Tripalium in France
for all his hard work on this.

Posted in Books, construction | 1 Comment

Tashi’s Turbine on PBS

Latest news: This broadcast will also be live on Facebook here.

The film Tashi’s Turbine will have it’s broadcast in the United States on PBS on November 13th 10pm EST.

Tashi’s Turbine – Documentary 

Set in the grasslands of the Himalayan Mountains, Tashi’s Turbine is an uplifting tale of a small village’s attempt to harness renewable, sustainable energy — the power of the wind.

Friends Tashi and Jeevan journey from Kathmandu to Namdok with hopes of building a stronger Nepal, one wind turbine at a time. Their first site is a remote village that previously relied exclusively on flickering candlelight. As Tashi and Jeevan work with the villagers, the elements and landscape bring unforeseen difficulties for installing a turbine — increasing the struggle to realize the community’s vision of power created by windy nights.


Posted in construction, developing world, People, Video links | Leave a comment

Jimmy winds a coil for a grid tied machine

Thanks to Jimmy of Eirbyte for this nice video

Wind turbine coil winding with counter from Eirbyte on Vimeo.

Posted in construction, Video links | Leave a comment

WindEmpowerment Maintenance survey

Have you answered the survey yet?

Dear Small Wind Turbine User,

The main problem of small wind turbines is their maintenance needs. They require a lot of care and it’s much more fun to build the wind turbine than to maintain or fix it.
To our knowledge maintenance failures and their consequences are known only locally and rarely shared. To help with that issue we want to
to facilitate the maintenance operation by having a quantitative feedback of your maintenance experience with your small wind turbine through the questionnaire below.

This questionnaire will take around 30 minutes of your time. It’s divided in 4 parts :

  • User data/ user experience
  • General information about your system
  • General information about your maintenance
  • Failures causes and consequences.

You can start it, leave it on side (by registering it) and finish it later on. 

There are 41 questions in this survey.

You have until 28th to add your data 🙂

Posted in construction | Leave a comment

Interesting tower for 2.4m machine at Tempelhof Berlin

Thanks to Windrad THF for these pics of a nice 2.4m diameter recipe book turbine at Tempelhof.  Here is a link to the video of the erection process.


This video is a fast forward and plays 8 times as fast than the original!

The tower was developed 3-4 years ago at the University of Applied
Sciences in Berlin. In fact, the vimeo stuff shows the original uni

The wind turbine tower was being installed at the Technical University of Berlin (HTW). In the end, the height of the turbine is 10 meters. When the “moving leg” falls into position in the end, there are some white pieces falling off, which is just snow…

The tower is made of wood and steel pieces and follows very simple structural principles. Its design has been developed by students of the Civil Engineering department in cooperation with the department of Renewable Energy Systems. The “structural inspection-report” has already been successfully passed, which was the very condition in order to get the building permit.

More info:
English version here

Posted in construction, People | Leave a comment