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Thread: Solar kayak

  1. #1
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    Default Solar kayak

    Preparations for an upcoming solar boat race.

    My 18ft kayak will get two small amas for stability.

    200W, 18V solar panels. 18V brushed motor from a cordless drill including its reduction gearbox. No-load 2200rpm.

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    Last edited by whiskeyfox; 11-12-2018 at 05:43 AM.

  2. #2
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    Default Re: Solar kayak

    Motor assembly


  3. #3
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    Default Re: Solar kayak

    Cool!

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  4. #4
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    Default Re: Solar kayak

    I hope you get a sunny day for the race.

  5. #5
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    Default Re: Solar kayak

    Nice! Is the race course regular / straight enough to make tilting the panels for the best sun angle worthwhile?
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  6. #6
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    Default Re: Solar kayak

    Quote Originally Posted by Thorne View Post
    Nice! Is the race course regular / straight enough to make tilting the panels for the best sun angle worthwhile?
    We will be doing laps around an irregular closed course. My amas are low volume, so if I need to I can always heel a little one way or another.
    The bulk of the race will be on either side of midday, so the sun should be almost directly above.
    My entry will be the runt of the litter, the other teams will no doubt use the maximum allowable power, i.e. 4x 320W panels. Hopefully in the future there will be a separate race or class for smaller, low powered entries.

    If my setup works I am certain that it will be the only one that will see regular practical use until next years race. 4 x 50W panels are a good deal more portable than even a single 320W panel!

    http://solarboatrace.co.za/

  7. #7
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    Default Re: Solar kayak

    Nice job, and clever. Are the threads of the drive shaft running inside of the seal?

  8. #8
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    Default Re: Solar kayak

    Quote Originally Posted by Gib Etheridge View Post
    Nice job, and clever. Are the threads of the drive shaft running inside of the seal?
    No, the threads start just outside the seal.

    Dunk test tomorrow, fingers crossed!

  9. #9
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    Default Re: Solar kayak

    If I am to be the slowest, at least I will do it in style!

    20181112_155152.jpg

  10. #10
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    Default Re: Solar kayak

    Dunk test done and splashed (dusted just doesn't sound right...).

    Thermocouple taped to motor. The reading is very unsteady while running, must be eddy currents throwing the voltage around. It settles at around 45 deg-C just after disconnect.

    No-load current around 1.5A. A bit lower than what I was expecting, especially with the added friction of the gearbox and seal.
    No-load voltage was very unsteady, jumping between 15 and 19V. Panel open circuit voltage was 20.8V with a thin layer of high altitude cirrus clouds in front of the sun.

    Full load (i.e. 8x3.8" APC prop) current was 4A, also lower than expected. In full sun the current should be around 11A at 18V with four x 50W panels.
    Static thrust was too much for the prop. The blade flex and twist must have reduced the load on the motor. I never measured the full load voltage.

    *Edit: The flex in the photo is in the wrong direction, it must be as a result of hitting the side or bottom of the cooler, not as a result of thrust.

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    Last edited by whiskeyfox; 11-13-2018 at 06:49 AM.

  11. #11
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    Default Re: Solar kayak

    Very cool.

  12. #12
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    Default Re: Solar kayak

    My favorite part is still your voice! Hahaha. You sound so cool.

    This motor is awesome. Awesome.

    Thanks for sharing it.

    Peace,
    Robert

  13. #13
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    Default Re: Solar kayak

    Excellent, thanks for sharing. Although those amas look way overbuilt and clunky. A nice curved laminated board might be the shot.

  14. #14
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    Default Re: Solar kayak

    Race day tomorrow. Sunny with a 20kt South-Westerly.
    Fortunately the channels are lined with large homes and the wind will be at an angle to the longer straight stretches.

    20181116_153318-2.jpg

  15. #15
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    Default Re: Solar kayak

    Quote Originally Posted by whiskeyfox View Post
    Race day tomorrow. Sunny with a 20kt South-Westerly.
    Fortunately the channels are lined with large homes and the wind will be at an angle to the longer straight stretches.

    20181116_153318-2.jpg
    Sweet! Youíll look like some Waterworld bad guy, or some other post apocalyptic pirate type. Hehehe.

    This is just the coolest thing. Thanks so much for sharing.


    Peace,
    Robert

  16. #16
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    Default Re: Solar kayak

    Ahhh, the a amas, or the arms that hold them, are well hidden. Good luck! I saw a solar cargo bike the other day. Tres cool.

  17. #17
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    Default Re: Solar kayak

    Well the sun surely did not disappoint but both prop blades parted mid-span before I even reached the start line.
    The replacement prop was a 3 blade 5"x5" which pulled the voltage down to 14V. I trimmed off about 1/4" on each blade and got the volts up to 16 and continued like that for 3 hours.

    I only had time to create mountings for 3 panels. By chance I noted that the motor rpm did not change when a shadow fell on the rear panel, which turned out to be completely dead. I had been cruising on only 100W the whole time, less if you consider the reduced voltage! After swapping the dud for the spare, the panels were right on 18V, i.e. max power.
    The tide and wind made it difficult to quantify the difference in performance based on gps speed, which varied from near zero dead into the wind (the forecast was correct) to just over 3kts.
    I managed to complete four laps (1.7nm per lap) in 3 hours (moving time on gps), so average speed of 2.2kts. For comparison, the fastest lap of the boats with 1kW+ panels was 15min, giving 6.5kts average.

    I am very encouraged by the performance potential at such low power. The implications for portability and practical use are considerable. The small prop might even be a decent option if it sits behind a much smaller motor housing. More tinkering and fiddling to follow. This is a ton of fun.



  18. #18
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    Default Re: Solar kayak

    The replacement prop and a pic to show the difference in panel sizes.

    vlcsnap-2018-11-17-20h01m50s189.jpg

    20181117_105126-2.jpg

  19. #19
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    Default Re: Solar kayak

    Fascinating thread. There is something I really like about the idea of solar direct to motor - seems like it would give an elemental experience a bit like sailing.

  20. #20
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    Default Re: Solar kayak

    Cool. A great way to tinker with boats.
    -Dave

  21. #21
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    Default Re: Solar kayak

    Ok,.... now that is really cool!
    and you did a really nice job of putting it all together.

  22. #22
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    Default Re: Solar kayak

    DOPE! Which is to say, so frikking cool itís almost frozen!

    So glad it worked. Please update us when you update her, eh?

    Peace,
    Robert

  23. #23
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    Default Re: Solar kayak

    Quote Originally Posted by Clarkey View Post
    Fascinating thread. There is something I really like about the idea of solar direct to motor - seems like it would give an elemental experience a bit like sailing.
    Very much so. Especially if there are clouds and wind. It will require actively steering to avoid the "lulls" i.e. shadows.

    Just to give you and idea of how sensitive the motor is to change, I could clearly note the change in motor rpm as a flying gull cast its shadow over a panel.

    Optimising overall system performance can be made more engaging (like trimming sails) by introducing manual manipulation at each component in the energy chain that has variable efficiency. That would be the panels, the motor and the propeller. For every unique condition that affects speed such as illumination, wind etc, there would be unique combination of settings that yields best performance.

    Panel optimisation could be done with a manually adjustable buck converter (essentially a dc-dc transformer) to keep panel voltage at its max power point while delivering optimal voltage to the motor. So no "intelligent" electronic controls such as max power point tracking controllers.
    For that particular voltage the motor will have only one speed setting that yields best efficiency so a variable speed gearbox will be required.
    And for that particular prop speed and boat speed there will be an optimal propeller pitch, so that also needs to be adjustable.

    Since every adjustment has an effect on all other settings, it will require an iterative series of adjustments to actually optimise all variables. Then the wind shifts and you have to do it all over again, so it could keep you real busy if you let it!

  24. #24
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    Default Re: Solar kayak

    This is really neat. I find the construction of the motor quite clever. I also appreciate the simplicity of the setup - solar panels directly powering the motor. Yes adding a manual throttle and an adjustable dc-dc converter would be akin to sailing. Your tell tails would be amp volt and power meters.

    I've been tinkering with solar panels for a while but with batteries.
    http://www.willmarsh3.net/el/aps/elver_aps1.htm
    Will

  25. #25
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    Default Re: Solar kayak

    Has anyone experimented with surface piercing propellers in this contest? Theoretically, at least, there would be a big gain in efficiency -- both with reduced drag and less power loss to turbulence off the tip of the prop.
    -Dave

  26. #26
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    Default Re: Solar kayak

    Quote Originally Posted by Woxbox View Post
    Has anyone experimented with surface piercing propellers in this contest? Theoretically, at least, there would be a big gain in efficiency -- both with reduced drag and less power loss to turbulence off the tip of the prop.
    Not as far as I know, but it is on my to-test list.

    If nothing else it would help in weeds and simplify the drive-train.

  27. #27
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    Default Re: Solar kayak

    Quote Originally Posted by whiskeyfox View Post
    Very much so. Especially if there are clouds and wind. It will require actively steering to avoid the "lulls" i.e. shadows.

    Just to give you and idea of how sensitive the motor is to change, I could clearly note the change in motor rpm as a flying gull cast its shadow over a panel.

    Optimising overall system performance can be made more engaging (like trimming sails) by introducing manual manipulation at each component in the energy chain that has variable efficiency. That would be the panels, the motor and the propeller. For every unique condition that affects speed such as illumination, wind etc, there would be unique combination of settings that yields best performance.

    Panel optimisation could be done with a manually adjustable buck converter (essentially a dc-dc transformer) to keep panel voltage at its max power point while delivering optimal voltage to the motor. So no "intelligent" electronic controls such as max power point tracking controllers.
    For that particular voltage the motor will have only one speed setting that yields best efficiency so a variable speed gearbox will be required.
    And for that particular prop speed and boat speed there will be an optimal propeller pitch, so that also needs to be adjustable.

    Since every adjustment has an effect on all other settings, it will require an iterative series of adjustments to actually optimise all variables. Then the wind shifts and you have to do it all over again, so it could keep you real busy if you let it!
    Thanks, that is a really great insight. What's next?

  28. #28
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    Default Re: Solar kayak

    Quote Originally Posted by Clarkey View Post
    Thanks, that is a really great insight. What's next?
    A sail!
    But only later.

    I need to test a few different prop sizes and attempt to build my own buck converter.

  29. #29
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    Default Re: Solar kayak

    Tested an 8"x4" propeller today. Still no electronics but I managed to do 7.2nm in 2h20min.
    That is 3.1kt average including all slow manoeuvres and a short stop. A 45% increase in speed equates to nearly three times the propulsive power of the little orange prop. And that is despite the large prop only running on partial panel voltage.

    The voltage read near zero with the motor running, so clearly a problem with either the meter or some of the connections. It showed the correct open circuit voltage though. As a result I have no idea how much power I was getting from the panels.

    A 1ft wind chop on the return leg had those little amas pitching like valve rockers. The front would submarine and the get flicked up, throwing spray everywhere. Is there an optimal position for placing the hinge axis relative to centre of gravity or centre of buoyancy? Photos of Meade Gougeon's sailing canoe as well as the B&B Expedition Canoe appear to have the hinge aft of "midships", but both have more volume aft and the amas appear to hang level.


  30. #30
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    Default Re: Solar kayak

    This is very cool. While I realize that the rules probably didn't allow a battery, I bet even a very small one would even out surges in voltage.

    Thanks for posting about it!

    PS "pitching like valve rockers" is a fantastic description!
    "If it ain't broke, you're not trying." - Red Green

  31. #31
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    Default Re: Solar kayak

    Quote Originally Posted by Garret View Post
    This is very cool. While I realize that the rules probably didn't allow a battery, I bet even a very small one would even out surges in voltage.

    Thanks for posting about it!

    PS "pitching like valve rockers" is a fantastic description!
    Now that the race is over I can add all the batteries I want. But since most off-the-shelf batteries come in 12 or 24V, my 18V setup will require wiring 3x 6V batteries in series or something. Most solar charge controllers are also set up for either 12V or 24V.

    I really wish I was able to get that loaded panel voltage today. I suspect that it would have been closer to 12V than 18V.
    I pounced on a Black Friday special for two 9A buck converters, a combination Volt+Amp meter as well as a small 5A MPPT controller. Controller is a big word for what I bought, it is really just an open circuit board but offers adjustable output voltage via variable potentiometer.

    The buck converters should allow me to run the motor efficiently at low voltage to turn even a 10" prop. They also offer constant current, constant voltage regulation on the output, so charging a 12V battery becomes an option.

    The little MPPT will only manage the current from a single panel, so it will be used to power a 3-cell brushless "solar assist" motor on the open Flywood canoe.

  32. #32
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    Default Re: Solar kayak

    Running directly of the panels does have its advantages.
    Other than simplicity and weight, it keeps you on your toes regarding efficient operation. If the motor caught a few strands of weed, the motor pitch lets you know. If you unknowingly cast a shadow on part of a panel, the motor pitch lets you know.
    By the time I invest in a battery, I am sure I will have an advantage in getting the most out of the system as a whole.

  33. #33
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    Default Re: Solar kayak

    I didnt realise the amas would be hinged. On a bigger trimaran they are rigid, would that not work better?

  34. #34
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    Default Re: Solar kayak

    Would you mind just clarifying the role of the buck converter? Is the idea to let let the panels input at whatever voltage they can manage (18-ish, I suppose) but manually adjust the output voltage to the motor down so that it receives more current? Would this work a bit like gearing? Perhaps running at a lower (motor) voltage heading upwind and higher down?

  35. #35
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    Default Re: Solar kayak

    Sailing tris and power tris are totally different animals. Getting the ama to stay on the surface to avoid the spike in drag that comes if the hull is driven under is important for high efficiency. The other approach is a cigar or fish-shaped hull that will cut through the waves cleanly. Sailing tris actually sail on an ama; it serves as the main hull when the boat is pushed hard.
    -Dave

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