Recipe Book updates

I have been active updating my Recipe Book lately.

Check out the updates page for details

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11 Responses to Recipe Book updates

  1. Horacio says:

    Hi , the axial flux generator is good for generating at low rpm, but should we discard building a radial flux permanent magnet generator for low speed operation ? You ´ve chosen the axial flux for cost and easy construction reasons ?
    Thanks ,
    Horacio

    • admin says:

      You can make any permanent magnet alternator work well at low rpm. However the axial flux alternator with no iron in the stator is very efficient at low power (no iron losses), is easy to build yes and also it does not limit its current at high power like a radial flux alternator with a steel core. I like all of these things. Maybe when magnets become too expensive we will need to go back to radial flux with steel core.

  2. Peter French says:

    I am trying to design a small alternator 14 v 20 amp. 300 to 600 RPM with an aluminium outer ‘shell’ rotating with the permanent magnets mounted on the inner face of the rotor. Coils to be fixed on stator facing rotating magnets. I want to avoid laminated iron core if possible. Can this be done? Also , most important to avoid cogging which will prevent self start on thios appication. Can you proivide pointers to design?

  3. admin says:

    I could help with the design but it is fundamentally weak. The magnetic circuit has very high reluctance due to the lack of an iron or steel drum (aluminium is not suitable for magnetic pathway) and no core in the stator but again a long way for the flux to travel in there. So the result would be a bit of a waste of the very expensive magnets.

    I wonder why you do not consider using the designs that I have carefully crafted over years of research, experience and head scratching?

  4. TJ says:

    Due to poor wind conditions at our homestead we are thinking about using solar to power a Stirling engine to run a 20kw Axial Flux Alternator. Could you tell me the horsepower needed to spin that size alternator?
    Thank you,
    TJ

  5. admin says:

    Horsepower can be converted to watts. Then allow for the efficiency. Efficiency is high at the low powers (low winds is where wind is highly valuable energy for the battery) but less at high power (say 70% in some cases). What you get out depends on the watts you put in.

  6. John Bertl says:

    I will be building a banki crossflow turbine that will produce .75 hp at 425 rpms. I would like to use it to heat water. (I have a 3,000 gallons water storage pit and heat my house with in the floor radiant heat from hot water. I have a wood boiler and fire it up when the pit gets cold.) I am thinking of building your pm generator and letting it run wild ac to a resistant heater that would be in my 3,000 gallon water storage pit. The distance from the generator to the water pit would be 45 feet. Then I could use less wood to heat my house. My alternative would be to use an induction motor as a generator which I have and would be cheaper. I see the induction motor as not producing as much energy as your well designed generator, however, and would prefer your generator for the fun in building it.

    Would you please comment on what you would do if you were me. Which would be the better (more efficient) option and what wires size would you use to build your pm if that is the route to take (I’m thinking bigger than what is in your plans). I admire what you have accomplished and respect your opinion.

    • admin says:

      hi JOhn,

      An induction motor can be a good choice for a hydro where the output is AC. You can use the C-2C wiring to get a single phase output and play with capacitors to tune the speed of the turbine. But to do direct drive you would need to either use a very large number of poles or work at a very low frequency, so you’d probably use a belt drive and this is going to lose some power and need looking after.

      You can get 500 watts at 425 rpm using my ten foot turbine Recipe alternator. The efficiency at that speed would be over 90%. I’d recommend using about 100 volts to minimise losses but take care because the voltage could rise much higher if the turbine runs unloaded. This could be a hazard and the high rpm could also throw the magnets off if they are not well secured! Mostly these alternators work at less than 500 rpm.

      I’d suggest you try 140 turns of 15 gauge wire, and a 30 ohm 500 watt heating element on the DC side of the rectifier. But you can easily adapt this to higher or lower voltage by changing the number of turns. Fine adjustment of the speed (on load) is done by increasing the gap between magnet rotors to increase the rpm until you get the best power output.

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  8. Lenny says:

    Hugh, I am gathering the parts necessary to build one of your turbines and have the Kindle edition of the 2010 metric book. I also have the 2003 pdf version.
    I cannot get (if any) updates from the recipes page listed. Is there a new website or has the updates been turned off?
    Thank you,
    Lenny in Oklahoma USA

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