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  #1  
Old 09-05-2012
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Question Overkill Solar?

I'm putting two 9.5' long solar panels (unisolar pvl-68) on each side of my mast on the cabin top for long distant cruising. They'll only set about 8" above the cabin roof and be strong enough to stand on.

I've already got the panels and much of the T-6 for this, so I'm doing it, but I'm asking myself if it's overkill....taking too much space in that area. Pretty risky to get on them in any kind of swell......
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Old 09-06-2012
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Re: Overkill Solar?

Electricity generation off the grid is like ammo. There is "enough" and "not enough" there is no such things as too much.

What's the worst that will happen? You can use electricity as to please, never conserve, and your batteries are always full and last years and years? Doesn't sound too bad to me!

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Old 09-06-2012
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Re: Overkill Solar?

If you find you have too much power, just buy a watermaker, that'll fix that problem pretty quickly.
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Old 09-06-2012
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Keep in mind shading....you'll likely only benefit from one panel or the other depending on where your sun is during the day.
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Old 09-06-2012
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Re: Overkill Solar?

Quote:
Originally Posted by 71Irwin32 View Post
I'm putting two 9.5' long solar panels (unisolar pvl-68) on each side of my mast on the cabin top for long distant cruising. They'll only set about 8" above the cabin roof and be strong enough to stand on.

I've already got the panels and much of the T-6 for this, so I'm doing it, but I'm asking myself if it's overkill....taking too much space in that area. Pretty risky to get on them in any kind of swell......
Keep in mind that armorphous panels require about 50% more surface area to do the same job a monocrystalline or polycrystalline panel will do in terms of output. Also mounting on either side of the spar is a location that will suffer from some pretty extreme shading and panel performance, even with armorphous panels, drops off rapidly with any sort of shading.

A bimini frame can be a much better location that suffers from considerably less shading and an array 1/3 the size can often out perform a significantly larger array when the location chosen is chosen to minimize the potential for shading.

I will let others chime in on safety....
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Old 09-06-2012
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Re: Overkill Solar?

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Originally Posted by sww914 View Post
If you find you have too much power, just buy a watermaker, that'll fix that problem pretty quickly.
Yes, I already have a watermaker that I'll be installing with the panels. That's specifically why I also purchased the panels. These panels in direct sun put out 4.2 amps each. The 90 psi pump for the watermaker requires 4.5 amps...the good news is I've installed 4, series 31 glass-mat 1100 amp batteries. Adding the wind generator should put me on easy street, unless of course, it breaks, but I'm only looking for 5 gallons per day, and the boat came with a 50 gallon water tank. If I've calculated reasonably well, the panels alone will fill the bill on sunny days, by themselves.




Quote:
Originally Posted by Maine Sail View Post
Keep in mind that armorphous panels require about 50% more surface area to do the same job a monocrystalline or polycrystalline panel will do in terms of output. Also mounting on either side of the spar is a location that will suffer from some pretty extreme shading and panel performance, even with armorphous panels, drops off rapidly with any sort of shading.

A bimini frame can be a much better location that suffers from considerably less shading and an array 1/3 the size can often out perform a significantly larger array when the location chosen is chosen to minimize the potential for shading.

I will let others chime in on safety....
Safety is my biggest apprehension, but these particular panels are tough as nails and will last. I did measure the loss from shading, it's fairly dramatic, thus the wind generator added next. Really, if you don't have wind for the wind generator, you might as well drop your sails and rely on the panels.

My old Irwin has a very long boom. It reaches only one foot or so shy of the end of the cockpit, so the panels would need to be over the transom.

I really intend on being able to set out in the middle of nowhere and enjoy the ocean, and not have to go anywhere. Fish, write, compose music.....what ever I feel like doing.
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Last edited by 71Irwin32; 09-06-2012 at 09:16 AM.
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Old 09-06-2012
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Re: Overkill Solar?

Are these panels in a location you might need to stand? If so, just throw some Interlux non-skid on there, and you will be good-to-go.
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Old 09-06-2012
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Re: Overkill Solar?

68 watts seems really BAD for the size your giving up when my tiny 24" pannel puts out 40 watts ?
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Re: Overkill Solar?

I didn't read very thoroughly the first time around.
So you have two 68 watt panels? That's it?
I have 3 200 watt panels and it's enough without the watermaker. With a fridge and a watermaker I may still need to run the engine.
I think you may have miscalculated something about your watermaker. They need about 1000 psi, not 90.
The watermaker I just bought draws 20 amps. Not 20 amps of 12v DC, 20 amps of 110v AC, so that will be 183 amps of 12v without factoring in any inefficiencies.
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Re: Overkill Solar?

What about mounting them vertically or nearly vertical on the cockpit rails/lifelines? I've seen this done and they act as lee cloths. It seems you would be giving up a lot in sun angle but you wouldn't have to worry about shading, or stepping on them.

I've seen it done often enough that there must be some good data our there on the losses from doing it.

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