Greg Gibbes hydro turbines using axial flux alternators

Greg sent me some photos of the hydros he is building using axial flux alternators to provide direct single-phase AC for sites in Papua, Indonesia. Here is some information. Greg’s email is greg.gibbes@gmail.com

These are single phase units, 240VAC, 50Hz.

The first model (I made 6 units about 6 years ago) had magnets secured with a Stainless steel band and fibreglass epoxy. magnets are 60mm diameter. It is capable of up to 2.8kW (1000RPM).  Measured efficiency was around 93%.

I started on 18 “Mark 2 machines” about 4 years ago, but life intervened and they have been on hold since.  I’d be happy make a little report with a few more details if you think people would be interested.

The second model is still under construction, but utilises aluminium magnet keepers for more positive magnet security and better cooling air flow.  I also did a bit of coil shape optimisation (magnetic field computer simulation).  I have a 6 pole (1000RPM) and 4 pole(1500RPM) version.  I calculate that these machines will be capable of 4~6kW maximum, partly due to larger magnets and lower coil resistance, but mainly due to better cooling.

My Mark 1 machines had both pelton and turgo turbine options.  I used an Eco-innovation plastic pelton wheel for the high head sites, and two sizes of turgo turbine for lower head sites.  I bought the buckets from energieag@libero.it in Italy.   My Mark 2 machines will also use three different turbine diameters to accommodate different head sites, but they will be turgo turbines only.  I am thinking to make my own turgo buckets, possibly by 3D printing…

I went with circular magnets thinking they would give more sinusoidal voltage.  Below is the design coil dimensions of my Mark 2, 6-pole generators.  The magnets on this machine will be 70mm diameter running at a pitch circle of 88mm.  According to the simulation, this gave the best compromise between high magnet flux capture and low copper volume with good sinusoidal waveform.  I haven’t actually built one to test yet though.


The machines are regulated with an electronic load controller (dump load controller).  The ELC I am using regulate frequency (eg 50Hz).  Voltage seem fairly stable as long as frequency is well regulated.  (I am working on my own ELC actually, due to shortcomings with some commercial ones we have tried)

Hope you get some joy out of seeing the work of a fellow renewable energy enthusiast!

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Bench testing of Kragten axial alternator

Adriaan Kragten has tested one of his small alternator designs and published results showing it is compatible with a 1.02m diameter rotor for a low power wind turbine.

A new chapter 6, “Generator measurements”, has been added to public report KD 678. A teacher of a technical school has built the 8-pole generator of the VIRYA-1.02 and I have measured this generator on my test rig for a 12 V battery load. The torque level of the generator appeared to be lower than expected but the matching in between rotor and generator is still acceptable. The maximum electrical power for the rated wind speed of 8 m/s is about 24 W.

Email from Adriaan
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Arduino-based controller project for the recipe 1800 turbine

Philippe wrote to me with this link:

Hi, I have my own Piggott wind turbine for 2 years, a 180cm 350W. I had some trouble about the way a regulator adapts energy to a battery charger or a injector. So I made my own regulator, which is a real MPPT for wind turbine and costs less than 50€. May be you will be interested, so here is the link : 

https://create.arduino.cc/projecthub/philippedc/a-wind-turbine-mppt-regulator-with-an-arduino-uno-783462

Best regards, Philippe.

Here is the manual at Github philippedc/Arduino-Uno-Wind-Turbine-MPPT-Regulator

 There are many regulators on the market. However they are mostly adapted for solar panels only, and if the curve of delivered power is similar, the way to regulate is different – to resume solar panels use buck converter, wind turbines use boost converter. Many are not MPPT, the PWM regulators are very less efficient than MPPT, and also specific wind turbine MPPT regulators are very expensive. 

So, It can be a very good project to self-build our own regulator, after having been built our own Piggott wind Turbine  

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Workshop in Enniskeen Co Cork


I strongly recommend this workshop with Jimmy and Miriam who I have worked with many times in the past.
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Alternative winding for K645 stator

Adriaan writes: “I have added a new chapter 6 to report KD 645 in which a 10-pole PM-generator is described using the housing and shaft of an asynchronous motor frame size 80. This generator has a stator with no iron in the coils. The tittle of this new chapter is: “Alternative winding with 15 coils”. The original winding is a 1-layer winding with six coils which are laid in twelve outside grooves milled in the Delrin stator bush. The alternative winding has fifteen coils which are laid in thirty, 8 mm holes which are drilled in the Delrin stator bush but this requires a totally different way to lay the winding. De Delrin bush is much stiffer for holes than for grooves so it can be pressed in the aluminium motor housing. I think that more copper can be laid in 30 holes than in 12 grooves and so the winding is more effective. I picture of the original winding is given in figure 1 of KD 645. A picture of the alternative winding is given in figure 3 of KD 645.

KD 645 can be copied for free from my website: www.kdwindturbines.nl at the menu KD-reports.”

Adriaan would be delighted to hear from anyone who wishes to build prototypes. He has a lifetime of experience in the field of small wind turbine design but lacks facilities to do this practical testing at present.

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Wind turbine building in the UK in October

Jonathan Schreiber is coming to the UK in October to teach a workshop based on my 2F design.

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Bill’s perspective on domestic grid-connected hydro payback

Being off the grid I don’t need to worry so much about “payback” since I do not pay for mains electricity in the first place and the payback to me is immensely more than cutting my running costs. But I was reading the blog of Bill in Monmouthshire who has been running a PowerSpout for six years and has a lot of useful insights to share.

Bill points out that “there is a benefit unique to very small hydros operating 24/7. Putting out power at the relatively low level of 500 watts (+/- 300), the turbine’s output closely matches the base load demand of a property.  Base load is made up of that multitude of appliances which are ‘on’ all the time – from battery re-chargers to fridges, freezers, central heating pumps, computers and so on. Totted up their power requirement can typically be 400 watts. That translates over a day to an energy consumption of 10 kWh.”

Whereas solar PV generates great lumps of energy in the middle of the day when people are out at work (so the house demand is low), hydro carries the load 24/7, and meets your needs directly. Solar energy will mostly be exported to the grid (exceeding the demand) but hydro power is mostly available to use (without buying a battery).

His hydro turbine really does have impact on Bill’s electricity bill.

Actually the same logic applies to off-grid sites in fact. You probably want a battery to maximise your usage of the resource and allow you to run a normal home off a hydro that only produces half a kilowatt of power. But the battery can be much smaller than I need, with my wind and solar systems. I wish I could have a hydro but there is no suitable site near my house.

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New Facebook page

I have started a Scoraig Wind Electric Facebook page that will only be about renewable energy stuff. (My personal Facebook has some pics of wind turbines etc but also plenty of grandchildren and dogs etc so this will be a better page for people who are more interested in generating their own power from hydro, solar and wind energy.)

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Another document by Adriaan Kragten

Adriaan continues to add to the impressive list of reports that are free to download from his web site. These provide a valuable resource to students or designers working on small wind projects.

My newest report KD 672 can be copied for free from my website www.kdwindturbines.nl at the menu KD-reports. The title of this report is: “Use of the VIRYA-1 or the VIRYA-1.25AF for pumping of drinking water using a 12 V battery and a pump with a 12 V, DC motor”. Although the VIRYA-1 is a small wind turbine with a rotordiameter of only 1 m, it is big enough to pump a flow of water q of 200 litres per day against a height H = 17 m at a wind speed less than 3 m/s. I would like it if you mention the availability of this report in your log.

(email from Adriaan Kragten)
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Furling cable for shut-down

sent to me by: Dave & Mary Lahar, Northeast Kingdom, VT, USA

4.6 m (15’) axial with power furling

26 m (85’) guyed tower

The furling actuator is mounted in the base of the tower.  It is 12VDC, travels .46 m (18”) and is rated at 68 kg (150 lbs).  It has a built-in potentiometer feedback allows for position control.

The actuator pulls on a 4 mm dyneema line to furl the tail through a pivoting snatch block, like those used on many PTO tractor winches.  Dyneema is very strong, light-weight and has virtually no stretch.  A small sash weight keeps the line taught, and the tail is free to furl independently.

When the winds are predicted to be unusually high, or rough (or both), or when we have ample solar production we can easily shut things down manually.  This is by far the softest method – furl the tail, and close in the (resistive) load bank – now we’re ready for most anything that comes our way.

The furling actuator is also controlled by the charge controller whenever the input voltage gets above a user-selected pre-set.  It is a simple dry-contact relay action.

We originally had a small hand winch to operate the tail, and that worked fine.  This arrangement allows things to be controlled from the house.  When the wind gets unruly, as it regularly does, or the PV is ample for the loads, it is nice to be able to save the wear and tear on the turbine.  The actuator has been in place now for about two years and has worked very, very well for us.

Thanks again for all your inspiration and we hope this may be of use to some of your readers.

Sincerely, Dave & Mary

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