Permaculturing in Portugal

One family's attempts to live in a more planet-friendly way


Finally! After a lot of trial and even more error over the last 2 years, it looks like we have the hydro generator we need for this site. As I write, it’s contributing power to the batteries, something that none of the previous generators have managed to achieve. Not a lot, because of the present meagre flow of water – for the second winter in succession there has so far been very little rain – but the wheel IS contributing for the first time.

Not only that, but it’s a supremely funky addition to our power generation capacity and is also, like the water wheel, proudly made in Benfeita! (Benfeita means ‘well made’.)

Hugh Piggott design axial flux alternator

The axial flux alternator on the back of João’s quad bike in its green and orange paintwork

Following our experiences, sometimes disastrous, with 3 other permanent magnet alternators/generators we were already thinking along the lines of making one since it was clear off-the-shelf solutions weren’t appropriate for the marginal nature of this site. I was consequently more than excited to hear another local friend was going to be experimenting with making Hugh Piggot design axial flux alternators.

João completed the first one before Christmas and after a coat of epoxy paint, it came here for testing today. This is a high voltage version (many configurations are possible) of the 1kW nominal power rating specification. It has very low cut-in speeds which is exactly what we’re wanting when flow rates here are low. Coupled with an MPPT charge controller which can convert excess voltage into amps, the alternator is able to produce a useful input when most others would fail.

Hugh Piggott design axial flux alternator

João and his alternator

Hugh Piggott design axial flux alternator

Different sprockets for gearing which Wayne created mounting plates for over the weekend … and Wayne’s breakfast roll

Hugh Piggott design axial flux alternator

Siting the alternator

Hugh Piggott design axial flux alternator

In position before drilling out bolt holes on the mounting framework

Hugh Piggott design axial flux alternator

Mounted, braced, connected and with chain fitted ready to go

Hugh Piggott design axial flux alternator

Water turned back on

Hugh Piggott design axial flux alternator

Alternator running

At the moment we have it on a 3:1 gear ratio which slows the wheel down quite a lot under load. The resistance creates some splash-back which equates to power loss, so we might need to adjust the delivery chute. There’ll be a lot more fiddling with different sprockets and the charge controller tomorrow to find the ideal ratio and settings, but what we could really do with is RAIN. The current weather forecast though is predicting temperatures in the low 20s by the end of the week and no rain before next Wednesday …


January 8th

3:1 proved the optimum gear ratio of those we had available to test. We figure the splash-back is going to be pretty inevitable when we only have 1 litre per second of flow to drive the wheel. These are summer flow levels, when it was never envisaged making use of the wheel anyway since we have more than enough solar capacity for our needs once the sun reappears from behind the hill to the south.

At these flow rates, the wheel is making around 21W after the charge controller has transformed the voltage – 0.5kWH in 24 hours. Around 20% of the power we could expect from ‘normal’ winter flow levels. This may sound paltry, and it is, but to me it’s vindication of the decision to stick doggedly by the wheel against the advice of hydropower experts on various internet forums who, pretty much without exception, all advised the installation of a turbine. Why? Because having run our data through the online calculator for the output of one of the more efficient turbines available, we would be making no more electricity with a turbine. The wheel is as efficient. It just needed the right alternator.

But our present flow rates highlight a different problem to address.

This is the second year in succession the winter rains have failed to materialise, so I am now considering how best to optimise what we can produce from the water even at these low levels. We can make 1.3kWH from the 1 hour 50 minutes of sun the solar panels get at winter solstice (if the sun is shining). If I can double that from the hydro component even at 1 litre per second, then we can limit the use of our propane generator to cloudy days only, which are not that common without rain as well. To do this, the only option open to us is to increase the head, so the next project is to re-site the wheel another 6-7m lower in the barroco and lay 150mm plastic guttering into the stream bed. This will channel the entire flow at these low volumes into the wheel chute with the minimum of friction, but still leave the system open to cope easily with the torrents of water, mud, debris and rocks which fly down this channel after a heavy downpour.

Reducing friction losses and re-siting the wheel will allow us to effectively double our head. Double the head equals double the power. Plus a little bit extra for the fact that the alternator will be operating at greater efficiency once we can increase its rpm to comfortably within its operating range rather than right on the edge as it is now.

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  1. Ernesto Rodrigo January 3, 2012

    Hola, buenos días y en- hora-buena por vuestro proyecto. La cuestión es que me encuentro en la misma situación por la que ya pasasteis, y buscaba información sobre ese tipo de rueda , el alternador axial y su regulación para cargar a 24v.
    Con los datos que dáis: cuales han sido los resultados?… amperios…
    Tenéis algún documento que recoja planos y medidas?, os agradecería mucho cualquier información.
    Muchos ánimos y gracias.
    Ernesto, desde las montañas de Castellón, España.

  2. jody January 3, 2012

    Nice, I’d love to check it out sometime with a view to making one for our site. Hope we get rain but not looking promising – if the spring rains fail too it’ll get interesting.
    Happy new year x

  3. Quinta do Vale January 3, 2012

    Hey Jody – Happy new year! For sure. Come round any time. I’m usually here. At the moment we have barely 1 litre per second in a stream that runs between 3-4 litres per second in an average winter, so are working on increasing the head. In this area of the alternator’s operating range – right on the bottom end – a few extra rpm can make a big difference in power. As for the rains, if it’s anything like last year and May’s daily thunderstorms, we won’t get to test it properly until the panels are already producing all the power we can use …

  4. Quinta do Vale January 3, 2012

    Buenas tardes Ernesto. Todos los cálculos se realizaron sobre la base de 3-4 litros por segundo de flujo lo cual es típico en el invierno. Teníamos la intención de cosechar 100-200W continuos, lo que sería suficiente energía para satisfacer nuestras necesidades. Por el momento sólo tenemos 1 litro por segundo en el río. Cuando se ha obtenido de datos más sólida con volúmenes de agua menos marginal, lo voy a publicar, pero por el momento esto es sólo el segundo día tenemos el alternador funcionando y estamos experimentando.

  5. Rick January 14, 2012

    Hi Wendy

    Really pleased to see the set-up working. Great looking machine too. How about pulleys/drive belts instead of sprockets? Easy to change for flow variations and a pulley can be custom turned without much effort if need be. Quite easy to source it all from the auto industry as well.


  6. Quinta do Vale January 16, 2012

    Rick!! Good to hear from you. Yes the Hugh Piggott designs work and on just 1 litre per second of flow at that! And the green and orange epoxy paint is just so funky! I love it!

    We discussed drive belts rather than chains/sprockets fairly early on in the proceedings and Wayne felt they were unlikely to be robust enough for the application unless we paid megabucks for them. The seasonal flow range of this stream is mostly between 1-4 litres per second, so a single sprocket should actually cover us pretty well. The current 1:3 works best of the bunch at 1 litre per second and will prevent the possibility of exceeding the voltage capacity of the charge controller at the other end of the scale. The wheel maxs out around 100rpm, which equates to 300rpm for the alternator. The charge controller is rated to 250V and when UPS get their finger out and actually deliver the thing (should have been here last Friday) we’ll be able to start logging some decent data.

    We got 800W open circuit (200V 4A) last Friday when they emptied a tank up in the village above us and turned the stream into a temporary torrent!

    Have you been on that course yet?

  7. rick January 21, 2012

    Hi Wendy

    The course was cancelled, but the best would be just to get stuck in and make one. If there are any more planned, I’d like to see if I could make it out there. I’ll be working till late Feb and then will have some time off.

    Fair enough about the sprockets; what works, works. Are there any heat issues, not being cooled by wind?

  8. Quinta do Vale January 21, 2012

    João is planning a 48V one next and already has the parts on order. We’re going to test that here too, though the suspicion remains that the high voltage configuration will be the one with the lowest cut-in speed and consequently the best for our low volumes.

    We’ve got the new charge controller in now, but the voltage is just that wee bit too low for its MPPT algorithms to work with. The alternator was producing around 21W with the hydro setting on the MPPT charge controller I have for the solar panels, but that one’s only rated to 150V, so not capable of handling the upper end of the range, though it’s possible that if the 48V model works well then we could use that instead and swap the charge controllers over. All this fun and games yet to come!

    We have a week of rain forecast from next Wednesday, so we’ll see what happens with some more water in the stream. No cooling issues so far, but then the alternator is only hovering around its cut-in speed. It’s not contained, so air flow will be reasonable. Will just have to see if its sufficient. I guess we could always make some fan blades to attach to the alternator side of the wheel and have it fan the alternator at the same time as generating power … :-)

  9. Tyler M February 2, 2012

    Looks like you have an excellent site and yes I agree a waterwheel can be just as good as a turbine and better in your application! I think your problem may be that you are trying to use it as a turbine (increasing velocity of the water with a longer chute) and aiming way too low. What you should instead try is a larger waterwheel, It looks like you could go with a wheel almost twice as large in the exact same location and I would urge you to go with a wheel as large as possible. If you look at the larger wheels they catch and hold the water rather than letting it splash past the wheel. This will give you more torque but require higher gearing ratios to maintain a proper generator rpm.

    Something else you were talking about which I believe is wrong is that you were losing power when the water was splashing back at low flow rates. That will actually increase power as you are reversing the flow of water not just stopping the water. In essence you have a sort of pelton or turgo wheel in an operational sense. If you want to stick with your setup (small diameter long chute) I would recommend you look at fabricating a banki turbine.

    Stick with the chain, it offers much lower friction at your speeds/power ratings with no risk of slipping.

    Good Luck!

  10. Quinta do Vale February 3, 2012

    Thanks for the comment. I’m aware a larger wheel would give us more torque, but at the sort of volumes we have in the stream at the moment, I believe we’re extracting about as much power as can reasonably be extracted under any set-up. A given volume of water with a given head has a fixed amount of power after all. Running the calculations for turbine yields doesn’t give us any more than we’re currently making, so there is no reason to fix what ain’t broke.

    Being as it’s a high head-low volume site, if we were to use the weight of water in the wheel as the primary motive force, we would lose the benefit of the head and end up with something that will barely move because there’s less than 1 litre per second flow right now. Our wheel is a kind of hybrid between a traditional water wheel driven entirely by the weight of the water in the buckets and a Pelton/turgo-type wheel (as you point out). The primary drive force is the incident velocity of the water, with a bit of extra benefit from the 0.75m or so the weight of the water in the buckets drops as it fills the wheel.

    What I meant about the splashback is that it’s a loss of efficiency. Yes, the water splashing back has transferred all its velocity to the wheel, but it’s escaping the bucket rather than making its weight available to add more drive to the wheel. We need to fine tune the incident angle of the water to minimise this and also to ensure higher flow rates don’t overshoot as much as they do at present.

    One of the main reasons for choosing a wheel over a turbine for this site is that the wheel is an open system whereas a turbine is a closed one. The flow in this stream varies from the present trickle to a howling torrent of mud and rocks and can move from one extreme to the other in the space of an hour. The wheel can handle that transition – and make the most of the available power at both extremes – effortlessly. A turbine operates within a much narrower range and requires much more extensive civil works to support.

    I’m not an engineer, but to me it seems the almost universal preference for turbines has as much to do with the fact that a closed system is inherently more controllable, predictable and transferable as anything to do with efficiency. It allows the technology to be mass-produced and installed in any situation that can deliver the operating parameters. I come at this from a slightly different perspective. I have a preference for open systems: ones that can function in the same ways and in symbiotic relationship with open natural systems, and for designing technology to fit a specific situation, rather than designing the situation to fit the technology. It’s an approach which I believe is ultimately more flexible, robust and efficient within its overall context, even if it has to sacrifice some specific efficiency, controllability, predictability and transferability.

    And bottom line is that every time I think of installing a closed system for generating hydropower here there is just this emphatic NO! on the level of pure gut instinct. I have to honour that!

  11. Tylerm February 3, 2012

    Fair enough but as an engineer I urge you to consider going to a larger wheel. You may not believe it but there is a considerable amount of energy lost due to friction in the chute (especially when the flow is low) which would be harnessed if you instead used a larger wheel. It would be more graceful and quiet too with a slowly spinning large wheel.

  12. Quinta do Vale February 3, 2012

    Trying to get my head round this, so bear with me … If we use a larger wheel, it’s harder to turn. What turns a big wheel is mass of water, not velocity. But the input we have to work with here is high velocity, low mass. Kind of analogous to high voltage, low amps. If we ultimately want to make the conversion to high amps, low voltage (which we do for battery charging) then it’s a case of deciding at what point in the generation process that conversion is made with the greatest efficiency while keeping the maximum flexibility inherent in the system.

    If we install a larger wheel without altering anything else in our set-up, then we’re creating more resistance which will surely result in more loss of drive mass from splashback? That seems to me to be likely to roughly equate to the present friction losses, resulting in no overall gain in efficiency.

    We can’t alter the delivery method of the water to the wheel without major civil works which, aside from being something that runs counter to my approach, would also alter the efficiency of this stream channel in doing what it was designed to do – act as a storm drain.

    Whereas if we make the volts to amps conversion at a point in the process where it’s more ‘contained’ (ie. in the charge controller), then we ought to have a higher level of efficiency?

  13. João February 5, 2012


    great job, really want to do something like that, i also live in Portugal ,where can you order or get the enameled wire and the neodymium magnets from?

  14. Quinta do Vale February 5, 2012

    Thanks João. Hugh Piggott lists some suppliers of parts for his plans under ‘Sources for stuff’ near the bottom of this page.

  15. João February 7, 2012

    Thank you, great link, very helpful.

  16. mark March 1, 2012

    Joao, you’ve done so well my friend – a great little device to have with interesting applications – very resistant to things like solar flares etc….

    Our project is gaining momentum which will be similar to the free energy device being tested by over 30 companies in south africa and due for release: – it starts about 16 minutes in. They are very brave. We will not be going public, but will make sure benfeita has access as soon as we complete the first prototype – 22kW :-)))) ( a lot of multi tasking and hard work going on :-)

    Love, Light, and all things Bright to you, Claire, the kids and the whole of benfeita!

  17. Don April 25, 2013

    Hello Wendy
    Awesome project and the scenery looks unbelievable considering I’m stuck on the praries in Canada. You have a good head on your shoulders and as an Engineer I think your doing everything right. We should never let engineering get in the way of common sense or practicality.

    As well this isn’t rocket science and nature has done all the hard work for us so all we have to do is transform this energy into something we can use. As such I would agree a bigger wheel is not the answer because you have a perfectly good one already made. One option may be an Arduino based MPPT regulator so you can set the voltage, current and power wherever you want it. The switching mosfets are cheap($3-4) and the whole thing should run under $50 for a capacity near the 1Kw range.

    I’m continually struggling with the same issues your seeing and most consumer products are useless when our parameters fall outside of their specs. In most cases I have found it way easier to just DIY and bypass the false claims and inferior quality altogether, it saves a lot of headaches down the road.

    In any case you have a good system with a few options, one could be to rewire the stator which I don’t like or use a converter to hit the required parameters. Power is power anyway we look at it and it is pretty easy to simply buck whatever voltage your at down to the voltage you want. Here were simply trading volts for amps, we run the gen at X volts then buck it down to Y volts to charge the batteries. The gen will have max efficiency at a given voltage so we run it there and the batteries will charge efficiently at a different voltage so we charge them there.

    I’m a big fan of intelligent design and have found the cheapest way to get more from less is in the control functions. The Arduino micro-controller rocks in this application because we can take a “dumb” water wheel/generator and have it act with something resembling intelligence . You can pick up an Arduino Uno clone off Ebay for about $14.

    This is way out in left field but Victor Schauberger had some very interesting insight into water.

  18. Quinta do Vale April 27, 2013

    Hi Don. Yeah I’m totally with your way of thinking and it’s nice to have validation from an engineer like yourself when I’ve had so many tell me to just go get a turbine. As for Viktor Schauberger, yes, yes, and yes again! I’m following some of his simpler principles here already and in time I hope to get into the deeper stuff. The Arduino controller I haven’t heard of but it sounds interesting – especially at that price! If I can find them in Europe then it’s a possibility, though if we have to import from the ‘States then it gets more complicated. We’ve been experimenting with an MPPT controller – the Midnite Classic 250 which can handle anything up to 250V plus battery voltage, so 274V in our case. This winter we’ve had a lot more rain, so finally have enough water to play with. Unfortunately the guys had an off day the last time we hooked up the alternator. Neither of them had their brains in gear, so we’ve currently got 2 controllers out for repair. Playing with high voltages isn’t all plain sailing …

  19. Prajna September 7, 2015

    Hi Wendy, as another engineer, I’d like to add a further view that I hope you’ll find helpful if you are still not getting the best out of your hydro.

    It seems there is a misunderstanding about head and the turbine-addicted engineers and theorists are unlikely to be much help in relation to an old technology like water wheels.

    Water power, whether wheel or turbine based, depends on two quantities: head and flow. Your site has great head and variable flow. I believe you have made a great choice in opting for a wheel based system rather than a turbine in your situation and I agree with Tylerm that bigger is better, for the following reasons:

    A bigger wheel will give you more torque, whatever flow rate you have. Your wheel is overshot and is most efficient when it captures the greatest volume of water at the greatest radius from the axle. Really you are better off thinking in these terms when using an overshot wheel. The contribution from the push of water from the race is negligible compared to the torque generated by the weight of water in the wheel and even more so as the diameter of the wheel increases. Also it is easier to capture more water than to extract more pressure from the flow. Overshot is about capturing flow rather than pressure, is very efficient at converting it to power and is simple to engineer.

    Once you drop pressure out of the equation your race only needs to deliver water to the top of the wheel. That means you can pipe it almost level from the source and any excess can simply continue to flow down it’s current course. Your wheel doesn’t need to deal with the maximum flow from the source and the concomitant dirt and debris; they can be diverted.

    The bigger it is the more power it can generate from the least flow. Obviously there are constraints: increased size means increased costs in materials; there will be limits to what will fit in the space; etc.

    Personally, I think the hybrid wheel is a compromise rather than a way of extracting the most out of your situation. It isn’t a case of getting the best torque from the weight of water in the wheel and adding that to the most power from the pressure from the race. Instead it is a compromise where both lose something. If you were limited to running a small wheel then you are gaining by the pressure of the race against the wheel but you would gain more with a bigger wheel capturing more of the flow. Your head would be better employed in the radius arm of the wheel than in the race.

    Not sure I’ve explained well and I don’t know your site but I was surprised to see how small your wheel was, given that it is overshot and you have so much head.

    My feeling is that you should be able to do far better out of even 1litre/sec than you are. Given some time and study I could come up with some theoretical maximum power for that flow for various sized wheels. Indeed I had a copy of Molesworth’s Engineering Pocket Book that had tables for overshot and undershot wheels but I don’t have access to it at the moment.

    Over the winter I will be designing micro-hydro for our quinta, which, like yours has great head and small flow (summer). I’ll be building as tall a wheel as I can. I’ll let you know how it goes.

  20. Quinta do Vale September 7, 2015

    Thanks for the comment. I know what you’re saying, but it’s not really feasible in this context. The overshot wheel / impulse turbine hybrid may be a compromise, but having run it through a winter of normal rainfall, I now know it generates more power than I can use. So if it already makes more power than I can use, I don’t need more. :-)

    The tricky times are the winters when the rains fail, like 2010-11, 2011-12 and 2014-15. By February 2012, a month after this post was written, the stream was down to a bare trickle and stopped altogether that summer. Apparently it never had before. So the bottom line is that regardless of what I do with the hydro, there are going to be winters when there isn’t enough water to run it.

    So I have to weigh up the amount of time, money and effort spent on additional tinkering against the gains on these marginal flows. Last winter, when it didn’t rain between the beginning of November and the end of January, I used 2 bottles of gas on the generator to make up the shortfall on the solar and hydro combined. €50 or thereabouts. Maybe I could have saved that, but it would have cost me a lot more to do so. And with weather patterns becoming increasingly unpredictable, it’s a hard one to call.

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