Solar Panel demands - SailNet Community
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post #1 of 25 Old 02-21-2012 Thread Starter
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Solar Panel demands

Looking to add solar panels to my Beneteau 46. Anyone know what amount of amps would be sufficient to handle most electrical needs while in the tropics. No water maker or air conditioning as of yet on board.
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post #2 of 25 Old 02-21-2012
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You probably want to do a usage analysis. There are various forms and guides as to what various systems eg lights, radio stereo etc use. A major element is refrigeration, but that depends on size, insulation quality, and temperature maintained, eg freezer double it.
I know one person in a small boat managed with 80 watts, others may triple that or more.
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post #3 of 25 Old 02-21-2012
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usage budget is the best way to go, and BTW it will be quite difficult to run AC on panels, inverter and batteries for any more than a few minutes of use
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post #4 of 25 Old 02-21-2012
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I agree with the posts above re doing a useage budget, but rather than attempt to meet all your electrical needs with solar, why not figure out how many panels you can reasonable put on the boat and find other sources for whatever additional power you need (e.g. wind vane, genset or small gas powered generator).

Panels can be installed easily on dodger tops, quarter rails (you'll need more than lifelines to mount them on), and stern davits/arches (if you have them). Once you go beyond these locations the boat probably begin to look like a floating solar power station. I've seen a few and, believe me, it's not pretty.

In my experience, lights, fans (you'll need several in the Caribbean), frig/freezer, pumps and electronics (chartplotters, radios, computer, etc.) demand more than my small dodger-top, fixed-mount solar installation can deliver. On a sunny day at 10-20 degrees N we can generate 7 amps from two 50 watt panels for 4-6 hours a day -- hardly enough to run the boat, but certainly enough to cut down on engine/genset hours. We have a friend who has about 240 watts installed in two panels, P & S on the quarter rails. He, too, finds that the panels have significantly reduced, but not totally eliminated, generator hours.

Economics of panels are OK -- capital costs are high, but I've found the ammortized cost per amp hour delivered of the panel installation is roughly equal to the operating cost (fuel, oil, etc) of the genset.
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post #5 of 25 Old 02-21-2012
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I am a FT liveaboard in the Caribbean and have 400 watts of tiltable solar.

Runs the firdge lappie lights and on a good day am full up by early afternoon.
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post #6 of 25 Old 02-21-2012
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I have about 160 watts of solar panels on my boat, work great.

One question. Having been going through the boat and upgrading all the boat wiring and adding fuse protection where none existed. One thing I do not understand about solar panels is how you protect yourself against short circuit (and maybe fire) from the panels. Say you panels put out 120 watts at 12 volts (10 amps). Normally, from what I understand, you do not place a fuse between the panel and the charge controller. Even if you did place a fuse it would do no good(if the fuse were sized below 10 amps it would blow, if above 10 amps it would never blow even on a short circuit). So it seems you could have a short circuit in your wiring between the solar panels and the charge controler that might start a fire.

Or if shorted, do the panels not put out any amps?
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post #7 of 25 Old 02-22-2012 Thread Starter
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maximum amp hour needs

With my 46 Beneteau I am guessing most demand on electrical system is a full day of sailing using auto pilot, fridge, nav system, running lights etc. coud produce a 24 hour day that could potentially require 500+ amp hours. Does that audit sound way off?
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post #8 of 25 Old 02-22-2012
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It ain't an audit but the sky is limitless.
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post #9 of 25 Old 02-22-2012 Thread Starter
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wow thanks for that insight
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post #10 of 25 Old 02-22-2012
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Quote:
Originally Posted by jkzdad View Post
...Does that audit sound way off?
Yes. That's equivalent to about 6 kWh. Thats about what a 1200-1400 sq.ft. house uses.

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