Solar Race Boats

Discussion in 'Multihulls' started by bad dog, Apr 20, 2009.

  1. bad dog
    Joined: Apr 2009
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    Location: Broken Bay, Australia

    bad dog bad dog

    SOLAR POWERED RACE BOATS

    Anyone interested in racing solar powered boats? These don't necessarily have to be multihulls, but practicality usually determines that they are.

    I* have an International Solar Class boat, which in Australia at least, has been unbeaten for 7 years, and we want a bit more competition! (* actually not just I by any means, but my kids' old school, along with another ex-parent and current teacher, and whichever students put their hands up from year to year).

    The International Solar Class Rule is simple, with the following hull/size rules:

    Box rule: 6m long x 2.5m wide x 1.5m high.
    Power rule: PV panels with a total output of 480 watts maximum.
    Battery rule: this is where human politics stuck its bloody oar in and complicated things - there are two variants:
    Japanese battery rule ("pure" solar) - 28.8Ah in the form of 4 x 12v/7.2Ah batteries equal to Panasonic LC-P127R2P.
    US Rule ("big battery" rule) - 4 golf cart batteries. This rule is not favoured anywhere outside USA for obvious reasons - it ain't solar!

    The best boats have maximisers, and use T-Flux or or other efficient motors rather than trolling outboards.

    Hull forms tend to be catamarans, although ours is a trimaran.

    Events are held in Europe, Japan and the US. The Australian event started in Canberra (Lake Burley Griffin), and moved to the Olympic Regatta Centre at Penrith several years ago.
     
  2. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Interested- definitely.
    (I used to build solar race cars- http://en.wikipedia.org/wiki/Queen's_University_Solar_Vehicle_Team )
    The rule you describe would make for a fairly small boat, but one that could be developed and raced on a realistic budget. And trailerable. It's interesting to see the array restrictions defined in terms of maximum wattage- in solar car racing, the array has historically been restricted by overall dimensions and, more recently, by total collector area. This has had the effect of greatly favouring expensive triple-junction cells and arrays of MPPTs, resulting in extremely expensive arrays. The rule you describe would pretty much cap the array cost at five thousand bucks or so- you'd have to win on hull design and propulsion system efficiency, ie. things that come more from engineering than from finance.
     
  3. Guest625101138

    Guest625101138 Previous Member

    From the rules you have given I guess the fastest boats would be radio controlled.

    What is the length of the course or run time.

    Rick W
     
  4. bad dog
    Joined: Apr 2009
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    bad dog bad dog

    Matt - the array power limit is intended to drive efficiency gains rather than outright kW. ie, if your array can be made light, streamlined, tilting or whatever, to squeeze more boat speed then you get gains with more thought and a little more money maybe, rather than the law of diminishing returns on big guns.

    Would the uni be interested in coming to Oz? Probably a very bad year to raise the idea!

    Rick - forgot to add the rule that says all boats must be piloted! Otherwise you're dead right! It's one of the advantages of sticking with the school - I get to test the boat and have direct fun prior to the race, then I have vicarious fun with a lightweight teenager driving in the race. Mind you, you can't put an old head on young shoulders, and we've had a few hairy moments.

    Dick Clarke
     
  5. Guest625101138

    Guest625101138 Previous Member

    What panels are commonly being used? I would like to know dimensions, weight, cost and availability. A reference to a supply would also be helpful.

    Rick W
     
  6. bad dog
    Joined: Apr 2009
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    bad dog bad dog

    The most common would be monocrystalline in standard glass laminate - BP or similar. The weight/displacement/drag penalty is a factor, but a slippery hull makes it less so. We used BP monos in a lightweight fibreglass/clear aramid laminate, which weighed about 1/3 of the glass version.

    The 480w limit can be awkward to work with if you use the stated outputs from manufacturers, which are quoted in a totally unrealistic theoretical condition of 1000w/m2 solar radiation and 20°C - which only happens in Antarctica on a brilliant summer's day in a stiff sub-zero wind. See Collyn Rivers for a justified attack on this practice.
    http://www.caravanandmotorhomebooks.com/articles/solar_how_much_sun.htm

    The BP Solar website would be a good place to start for standard panels:
    http://www.bp.com/sectiongenericarticle.do?categoryId=9020466&contentId=7038093
    The simple approach here would be to use 6 x 80w polycrystallines.

    Kyocera make similar rated panels:
    http://www.kyocerasolar.com.au/products/kdmodule.htm

    But if you want a more commercial approach ask John Harrison at Australia Wide Solar:
    http://www.awsolar.com.au/

    We used 5 x 100w panels which were officially de-rated to a total of 480w because of the clear film over the top. The film is designed for long term protection in a marine environment. They were new in 2001, but last year we had to performa some surgery to re-solder a few cell connections. This is why the big manufacturers use glass! - and why the solar cars use nothing at all - they just keep maintaining their arrays.
     
  7. marshmat
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    marshmat Senior Member

    Our last solar car had Sunpower A300s, fully encapsulated in SunCat Solar's laminate system. The resulting panels keep virtually all the efficiency of the bare cell, are only a couple of millimetres thick, and are very durable (you can't walk on them, and hailstorms will hurt them, but they can bend and take soft impact without damage). Gochermann has an even better cell encapsulation system. However, you must be prepared to shell out serious dollars for these laminates.
    We tried an array once with a conformal flow-coating to protect the cells- not something I would recommend. Not durable, and it tended to crack at the cell edges (thus water would get in and attack the solder joints).
     
  8. Guest625101138

    Guest625101138 Previous Member

    How difficult is it to remove the glass laminate from a large solar panel and replace it with something lighter but maybe higher maintenance?

    What would be the best replacement material combining low weight and acceptable life? I figure that a boat used every now and then could have covering on the cells to protect from elements when not needed and also the boat would be normally stored under cover.

    Has anyone here replaced the glass and able to provide step-by-step instruction?

    My preferred panels are 225W Sunpower. Any advice? I have not seen dimensions for the 300W units.

    That reference paper gives some upside on solar panels used on water owing to the reflection from the water surface. The panels near the shore give better than design rating!

    Rick W
     
  9. Boston

    Boston Previous Member

  10. bad dog
    Joined: Apr 2009
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    bad dog bad dog

    Rick, I have never heard of anyone delaminating a glass PV laminate, but hey - it's a big world out there, and I never thought anyone could actually enjoy opera, so anything's possible.

    Solar Sailor make up panels for their commercial craft, and I think that you can buy individual cells (wafers etched and all the little silvery bits printed in, but no connections beyond the cell) from BP if you have the right - er, connections. We did it in 2001, so why not again?

    Then you can lay them up on a foam sandwich panel or whatever - a longitudinally tilting array is a good way to maximise exposure without wind resistance.

    The other thing I have to dig up is some photos of a beeeyoootiful boat built by the staff at Incat in Tassie in 1998(?) - a sexy sophisticated cat with tilting panel - it was a joy to behold. I will get some photos of this - and our boat - loaded onto this laptop so youse can all see what I'm on about.
     
  11. marshmat
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    marshmat Senior Member

    Rick,

    Trying to re-encapsulate a sealed glass panel will most likely just result in a lot of damaged cells.

    If you want minimum weight and good durability without compromising efficiency, Gochermann or SunCat laminates are the solution of choice in the solar car world. Gochermann's system (by far the best) is most commonly used with multi-junction GaAs cells and is reported to cost in the range of eight to ten thousand dollars a square metre- if you provide your own cells. SunCat's system is much cheaper and works very well with the Sunpower A300 cell. Sunpower and SunCat used to have an agreement to distribute ready-to-use laminates of A300s for special applications such as solar racers; we picked up one car's worth in 2007 and as far as I know they're holding up well. I don't know if this combination is still available.

    We have tried about a dozen different home-made encapsulations for the little panels we use for the high school teams (these are about 1 kg cars and run on a slot-car-like figure 8 track). Nothing lasts. Either you use the rigid, watertight sealed glass units the manufacturers provide, or you laminate the cells so tightly that even if you bend them them, they won't crack. Anything in between just results in a lot of jagged shards of silicon, unless you are really insanely careful (like, orbital telescope assembly careful, or gallon of nitroglycerin careful). We did try one involving vacuum bagged, heat cured ETFE film that seemed promising and protected the cell OK, but tended to leave air bubbles that screwed up cell performance no end.
     
  12. yipster
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    yipster designer

  13. bad dog
    Joined: Apr 2009
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    Location: Broken Bay, Australia

    bad dog bad dog

    Amazing! (and great website too - thanks mate!) - and some guru techies here have just developed a solar cell paint that looks like having commercial efficiency
    http://www.abc.net.au/tv/newinventors/txt/s3008638.htm
    ... it just keeps getting more interesting!

    BTW, I'm in the planning stages of putting the race boat's panel, controller etc, and drive leg onto my old A class cat, with foam s/w hard deck and rails, to make a practical fishing/exploring/photography boat - or maybe a start boat for A-cat races! Stay tuned...
     
  14. redreuben
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    redreuben redreuben


  15. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Not trying to burst anyone's bubble, but rumours of paint-on solar collectors have been going around for a while... University of Toronto had news reports of something similar about five years ago. The media tend to hype it up far too much; there are all sorts of really interesting solar technologies that work under a microscope in a lab (and might eventually be developed into useful products) but are a long way from mass production. I'd really like to see these guys succeed, and I'd hate to see the media and any potential investors lose their perspective (and thus hurt the chances of success) before the technology is actually ready for deployment.
    By all means, go for it. Laminating is a lot of work and you WILL break cells at first, so start with the cheap stuff. Look up Hans Gochermann and (at a slightly cheaper price point) SunCat Solar to see the current state-of-the-art in cell lamination. Then try to figure out a way to do something similar on a more reasonable budget.... :)
     
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