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

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 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!

About hugh

I live off-grid in NW Scotland and have spent my life playing with wind turbines. I also love small hydros. Hands on renewable energy is my thing and I like to learn and to share my experiences.
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1 Response to Greg Gibbes hydro turbines using axial flux alternators

  1. Kostas says:

    Hi Greg and Hugh,

    Thanks for posting, this is all very interesting!

    In 2013, I made pico-hydro installation using an axial flux permanent magnet generator, built as described in Hugh’s wind turbine manual, and driven by a plastic spoon turgo turbine. Here is a post and here is a video It has been spinning without any maintenance for 7 years, so I have found it to be very reliable.

    As it is a low power machine I don’t use an ELC, but use it in conjunction with a small battery bank and a 1.5kW inverter to get the power needed from the system.

    Also here are some tests at the NTUA, to use a powder iron core in such pico-hydros

    Finally, in 2016 we printed the spoons using a 3D printer and tested them in the lab for efficiency with good results

    I still have not installed them at the site to test them for long term durability, but given they are very cheap and easy to print, I would assume that they would be a good low cost and locally made alternative to plastic cups, although they might need to be replaced more frequently.

    Thanks again for sharing!

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