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Old 10-09-2013, 16:55   #1
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Solar panels et al

Maybe its an age thing, but whatever I try to do now on this darned boat turns out to be a problem, probably because I over-think the issue instead of just getting on with it.
I want to put 45 watts of solar panels on the boat and the H28 being a small vessel, have opted to erect a pole at the stern with the panels on it. I have checked the sun altitude/azimuth charts for the NZ summer and conclude that the ideal angle for the panels is 30 degrees. If I install them at that angle then I need to be able to rotate the pole. If I'm going to build a mechanism to rotate the pole then I might as well build it so that the panel angle is adjustable as well....and so it goes on... and on..
In real term usage is there any significant benefit in being able to manually track the sun or should I just mount the panels flat and leave it at that?
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Old 10-09-2013, 17:01   #2
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Re: Solar panels et al

Perfect is the enemy of good - Wikipedia, the free encyclopedia

I used $10 radio shack TV-VCR cable to run from my SSB antenna tuner to the insulated back stay. Zip ties hold it on at the backstay. If I were to ask on here whether I should do that, I would get a 20 page thread telling me it's stupid for a variety of reasons.

It works fine for what I need and I have bigger fish to fry.
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Old 10-09-2013, 17:01   #3
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Re: Solar panels et al

Quote:
Originally Posted by Chrisc View Post
In real term usage is there any significant benefit in being able to manually track the sun
Yes.

Quote:
Originally Posted by Chrisc View Post
or should I just mount the panels flat and leave it at that?
Yes.

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Old 10-09-2013, 17:04   #4
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Re: Solar panels et al

Quote:
Originally Posted by rebel heart View Post
I used $10 radio shack TV-VCR cable to run from my SSB antenna tuner to the insulated back stay.
Thread drift:

Really? You have an 18 gauge component video cable with vinyl insulation connecting your coupler to your antenna? I can't even imagine how you made the connections.

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Old 10-09-2013, 17:05   #5
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Re: Solar panels et al

forget abut being able to tip the panel and just install a larger flat fixed panel and be happier in the end
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Old 10-09-2013, 17:06   #6
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Re: Solar panels et al

Quote:
Originally Posted by colemj View Post
Thread drift:

Really? You have an 18 gauge component video cable with vinyl insulation connecting your coupler to your antenna? I can't even imagine how you made the connections.

Mark
No, the crappy coax stuff. RG... 8? I'm old enough to remember VCR's... I'm pretty sure there were models with coax.
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Old 10-09-2013, 17:25   #7
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Re: Solar panels et al

I got a 'you beaut' deal on 3 x 15watt panels and a regulator, so equipment is a given. Our particular scenario is :

We spend 2 - 3 months full time on the boat over summer.
Electrical consumption 18 - 20 amps/day.
Engine hours approximately 30 min/day.
85 amp alternator charging through some sort of BEP smart charger.
House battery 100a/h.

On the above the question is do I need to optimise the panel output by sun tracking (complicated) or will mounting flat (simple) cut it?
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Old 10-09-2013, 17:34   #8
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Re: Solar panels et al

Don't over think it, really. If you want to really maximize, make sure you don't have any shadows on it. Flags, stays, antennas, topping lift, etc.
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Old 10-09-2013, 17:53   #9
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Re: Solar panels et al

Yes, I think you are right.
Undoubtedly, pointing the panels directly at the sun will produce a higher yield but this is a theoretical gain unless one is prepared to sit on deck and constantly tweak the angles.
Purely for my own edification, what I would like to know is, what is the angular range at which panels are most effective, ie at what angle does the panel's output really start to decline because light is reflected by the glass rather than absorbed through it?
I know, rather pointless but just interested, that's all.
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Old 10-09-2013, 18:11   #10
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Re: Solar panels et al

Quote:
Originally Posted by Chrisc View Post
I got a 'you beaut' deal on 3 x 15watt panels and a regulator, so equipment is a given. Our particular scenario is :

We spend 2 - 3 months full time on the boat over summer.
Electrical consumption 18 - 20 amps/day.
Engine hours approximately 30 min/day.
85 amp alternator charging through some sort of BEP smart charger.
House battery 100a/h.

On the above the question is do I need to optimise the panel output by sun tracking (complicated) or will mounting flat (simple) cut it?
In the summer my 48-watt solar panel laid flat on my Bimini top produced about 1 amp in the morning (7-10) and evening (5-8) and 3 amps during the middle of the day (10-5). That's about 27 amp-hours per day.

If you tilt your panel towards the sun in the morning and evening hours you can pick up an additional 12 amp-hours, but it sounds like you would be OK with a flat panel for the summertime.

Fabbian
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Old 10-09-2013, 22:48   #11
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Re: Solar panels et al

Thanks for the replies.
I have been thinking it over - I have a lot of S/S offcuts and plastic bushing material; I can weld stainless; I have an engineering lathe and most importantly I have the time and the inclination.
So, I will build the pole for my panels to be fully directional but able to be locked with the panels horizontal should frequent adjustment prove to be a pain in the bum. That way must surely be the best of both worlds :-)
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Old 10-09-2013, 23:44   #12
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Re: Solar panels et al

Well remember too that the boat moves. So any particular angle you get dead right will change as the vessel pitches or rolls, or when you trim it wrong.
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Old 11-09-2013, 00:24   #13
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Re: Solar panels et al

Yes, I agree.
Any gains made with directional panels would be lost by the boat's motion in a seaway. But we are just coast-hoppers now. 3 or 4 hours a day sailing from one sheltered anchorage to the next. It is at anchor where I can see that we may derive some benefit from adjustable panels.
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Old 11-09-2013, 01:09   #14
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Re: Solar panels et al

At anchor your boat will swing, so any angle will quickly become non-optimum. In a slip an adjustable angle will give some improvement.

The amount of power loss is basically the cosine of the angle error. If your panels are pointing 20 degrees away from the sun, the power will be Cos(20) or 94% of what you would get with zero pointing error. From what I've seen, very few people with adjustable panels actually bother to adjust them. Mine are fixed and flat.
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Old 11-09-2013, 01:50   #15
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Re: Solar panels et al

Here in the tropics of Oz our daytime winds are predominantly onshore south easterlies, then during the night till mid morning we have a land breeze from the west. So while on the pick having the ability to tilt our davit mounted panel over 45 degrees allows us to nearly double our daily Amp hours with very little effort in the morning & afternoon.

Definitely worth the little extra effort when building the frame for the panel.



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