Solar powered pontoon, question.

Discussion in 'Propulsion' started by shuller1458, May 29, 2014.

  1. shuller1458
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    shuller1458 New Member

    Hello, boat community. My name is Daniel. I have an idea to build a solar powered boat. Can some of you with a little bit more electrical knowledge help me out to get overall idea what I need.

    ok, here it is. The motor I will be using is Torqeedo 4.0R. here are some specs:

    Input power in watts 4,000W
    Nominal voltage 48V

    So if I want to run it at full power: How many solar panels I need?
    Do I need batteries as a buffer between motor and panels? What kind of battery bank I need?

    Thank you for help.
     
  2. gonzo
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    gonzo Senior Member

    You can expect about 8W per ft/sq. For 4000W you need 500 ft/sq panel. That will only work at noon.
     
  3. Rastapop
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    Rastapop Naval Architect

    That's too low, you can get 100-200 W per m^2. 150 W / m^2 is around double gonzo's numbers above.

    But you can expect only about 5 full hours of sunshine per day (effectively), and also you'd need 25 m^2 or so to supply 4000 W directly from the panels, so yes you will definitely need batteries.
     
  4. CDK
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    CDK retired engineer

    Hi Daniel,
    At full power your engine will draw approx 80 Amps from a 48 volts battery bank (4 batteries of 12 volts in series). If you choose 100 Ah types and discharge them to 50% you can run at full power for approx. 40 minutes on a cloudy day. A bit longer on a sunny day if you have a lot of solar panels, but you can not install enough panels to draw 80 Amps continuously because that would require 40 panels of 100 W each.
     
  5. gonzo
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    gonzo Senior Member

    Some manufacturers claim about 13W ft/sq, about 60% more than what I said. However, that is for a static installation with compensation for the sun's declination. That means it is not installed flat but so that the angle of incidence of the light is 0. In a boat that will never happen, unless occasionally withing the tropics.
     
  6. shuller1458
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    shuller1458 New Member

    Thank you for the replies. Well, the pontoon I will have will house 32 250w panels. So by my calculations it is 32*250w=8000W. And lets assume that loss is around 25%, so I still make 6000 continuous power, isn't it enough to power the 4KW motor continuously?
     
  7. gonzo
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    gonzo Senior Member

    Only at noon if the panel is tilted towards the sun. What is the size of the panels?
     
  8. shuller1458
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    shuller1458 New Member

    250w panel are 1.6m*1m or 64in*39in. I will have 32 of them.
     
  9. CDK
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    CDK retired engineer

    My fixed solar installation has southeast oriented panels at 60 degrees angle and an Amps gauge calibrated in % of peak power.
    100% I see only on exceptionally bright, windy days around noon, say between 11 and 1 o'clock. On hot summer days the needle touches 80% max. because the panels get hot, on normal sunny days it reaches 70%.
    From 6 to 11 AM the gauge climbs from 0 to 70%, from 1 PM to 6 PM it drops to near 0 again, so the average over a 12 hour period is between 30 and 35%.

    On a boat you may expect even worse figures unless you build an articulate system that tracks the sun in both direction and angle.
     
  10. gonzo
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    gonzo Senior Member

    Batteries as a buffer will give even worse performance. The solar panels don't produce enough energy for the motor, so the extra weight won't help at all. If the batteries are pre-charged, then the panels can extend the use of the boat. The extra expense, lack of performance due to weight and windage, don't seem to make it efficient.
     
  11. Paulc
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    Paulc Junior Member

    Have you considered wave power?

    I tried posting a video of my prototype but this site freezes at 97%
     

  12. Grey Ghost
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    Grey Ghost Senior Member

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