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Forums > Sailing General

Mounting Solar Panels

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Created by keensailor > 9 months ago, 27 Apr 2013
keensailor
NSW, 701 posts
27 Apr 2013 9:10PM
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hi
does anyone have any suggestions on mounting solar panels on pushpits or deck. And any off the shelf brackets that are good.
cheers

Ramona
NSW, 7637 posts
28 Apr 2013 8:52AM
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I have a 40 watt panel fitted vertically each side of the pushpit on home made SS brackets. Top edge is about the same as the top rail. I sail with a windvane and the panels don't interfere.

MorningBird
NSW, 2674 posts
28 Apr 2013 11:51AM
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Graham, could you show a photo of your solar panel mounts?

keensailor
NSW, 701 posts
28 Apr 2013 6:31PM
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looks like I will go down the batwing mounting style like the attached photo. Does anyone know where to get the black tubing brackets shown in photo.

Ramona
NSW, 7637 posts
28 Apr 2013 6:52PM
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keensailor said...
looks like I will go down the batwing mounting style like the attached photo. Does anyone know where to get the black tubing brackets shown in photo.




Bias or Whitworths.

Ramona
NSW, 7637 posts
28 Apr 2013 7:22PM
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[URL=.html] [/URL]


This is about the best I can do John. The panels are fixed in position with SS tubes with black plastic rail fittings on the ends. Panels are not quite vertical and are set parallel with the centreline.

HaveFun
NSW, 201 posts
28 Apr 2013 9:31PM
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Pardon my ignorance here but I understand the irradiance from the sun (and hence) solar power output to be maximum at solar noon when the sun is directly overhead. So with the panels mounted close to vertical as in the picture how much power is produced? I am not being critical I just want to know if the system works and, presuming it does, how much power?

cisco
QLD, 12346 posts
29 Apr 2013 12:26AM
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If you have a pole mounted one corner of your transom with a vertical axis swivel that allows as close to but not more than 359 degrees of swing, atop of which you have another swivel with a horizontal axis that allows as close to but not more than 179 degrees of swing, you will have an ideal place to mount a solar panel or two.

The swivels need to be able to be clamped at any degree of their angular range.

Sorry I can't post a picture of the set up as I have only ever seen it on one yacht about 15 years ago. It was a Kelt 39 (now called Feeling 39s).

The pole needs to be of sufficient height so that you don't gouge your scalp on the corners of the solar panels.

This set up allows adjustment of the panel/s to receive the sun's rays at 90 degrees almost anytime of day regardless of heel angle of the yacht.

Another benefit is that it allows the panel to "feathered" when the weather gets up.

Now that we have this set up on one side of the transom the yacht looks and is a tad unbalanced.

We could do the same on the other side, but why would you?? Far better if on the other side we have a pole with a wind generator sitting atop it set at sufficient height so that the blades don't chop you ears off. Just as it was on the Kelt 39.

So here we have a system that gives electricity under just about any scenario, be it at the marina, at anchor or under sail.

When the wind's a blowin' and the whips a'crackin it is usually overcast, so feather the panel and free the prop.

When the sun's a shinin' and there's barely a breeze, feather the prop and free the panel.

The whole set up looks a lot neater than these huge gantries that are so common on the back of yachts these days. For cockpit shade under sail a foldable bimini is the way to go.

cisco
QLD, 12346 posts
29 Apr 2013 12:38AM
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HaveFun said...
Pardon my ignorance here but I understand the irradiance from the sun (and hence) solar power output to be maximum at solar noon when the sun is directly overhead.


You almost have it. No matter the intensity of the solar rays, the maximum absorbtion of the energy happens when the solar panel array is at 90 degrees to the direction of the solar rays.

If at noon the sky is overcast...........it is like kissing your sister...........if at 2 pm it is clear skies............you can make love again if you angle it right.

Ramona
NSW, 7637 posts
29 Apr 2013 9:30AM
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HaveFun said...
Pardon my ignorance here but I understand the irradiance from the sun (and hence) solar power output to be maximum at solar noon when the sun is directly overhead. So with the panels mounted close to vertical as in the picture how much power is produced? I am not being critical I just want to know if the system works and, presuming it does, how much power?



They produce pretty much the same power as if they were at 90 degrees to the sun. Experiment with a test meter and see. I followed the example of one of the other local boats who set his up so that they tilted up to the horizontal position when at anchor. He found there was no practical advantage to this and now leave them at the vertical position.
What most people don't realise is that solar panels are heat sensitive and once they get to a certain temperature [can't recall what it is of the top of my head but think its about 27c] they produce less power. Placing a black surface at 90 degrees to the midday sun in summer will actually produce less power!
My yacht is actually used for sailing and nothing is added that will slow it down, certainly not air brakes or any added weight in the ends if it can be avoided. When the yachts heeled obviously the panels are pointing higher or lower but watching the regulator they always show a charge. The yacht is on a swing mooring in a tidal estuary and battery power is never a problem.

cisco
QLD, 12346 posts
29 Apr 2013 11:39AM
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^^^I stand corrected.

Ramona
NSW, 7637 posts
29 Apr 2013 6:53PM
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[URL=.html] [/URL]

Out sailing today so took a photo of one panel. Later in the day, about 1330 I was sailing with the sun right over the stern at about 80 degrees, sun was only directly on the alloy frames. Both panels showed 13.4v, one battery was 13.4 and the other one that was in use 13.2v, laptop and stereo running.

MorningBird
NSW, 2674 posts
29 Apr 2013 7:23PM
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Interesting. On a hot day my 40w panel puts out over 15v.

My understanding of electrics isn't good, see my other post, but my understanding is it isn't the voltage from the panel that counts, it is the current.

I can have a reasonable voltage coming from my panel but the current output is very low, say 0.8 amps. On a good day with the panel pointing at the sun the voltage is way up over 15v and it puts out between 2 and 2.5 amps. A 40w panel has a max current of 3.33 amps (40 divided by 12). My panel is 25 years old so that is pretty good in my books.

LooseChange
NSW, 2140 posts
29 Apr 2013 9:46PM
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MorningBird said...
My understanding of electrics isn't good, see my other post, but my understanding is it isn't the voltage from the panel that counts, it is the current.


Your understanding is spot on regarding the output from the panels, it is indeed the wattage. Voltage is the measure of electrical pressure and wattage is the amount of juice that is flowing.

keensailor
NSW, 701 posts
30 Apr 2013 3:45AM
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Ramona said...
Out sailing today so took a photo of one panel. Later in the day, about 1330 I was sailing with the sun right over the stern at about 80 degrees, sun was only directly on the alloy frames. Both panels showed 13.4v, one battery was 13.4 and the other one that was in use 13.2v, laptop and stereo running.


Thanks for the photos, thats great!

cisco
QLD, 12346 posts
30 Apr 2013 6:54AM
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Ramona said...
[URL=.html] [/URL]

Out sailing today so took a photo of one panel. Later in the day, about 1330 I was sailing with the sun right over the stern at about 80 degrees, sun was only directly on the alloy frames. Both panels showed 13.4v, one battery was 13.4 and the other one that was in use 13.2v, laptop and stereo running.


Seems to defy logic but I guess the figures don't lie.

How much bark have those two long bolts taken off so far?

Charriot
QLD, 880 posts
30 Apr 2013 8:30AM
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Sure the current is what counts.
Low current is not always related to solar cells but the overcharge regulator
starts limiting when batteries are close to full charge.

The best way how to understand your panel is before the installation
Connect the globe / say 40 W panel 15-25 watts globe/ directly
to the panel and move panel around, different angels - shade atc.

I personally never use MPPT solar regulator, but tests shows, they use switch mode
circuit and they can use every bit from solar energy and convert to usable charge.

http://www.ebay.com.au/itm/15A-MPPT-Solar-Panel-Regulator-Charge-Controller-12V-24V-Auto-Switch-2-BOC-/360624277942?pt=AU_Solar&hash=item53f6e1c9b6&_uhb=1




Ramona
NSW, 7637 posts
30 Apr 2013 8:45AM
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I thought a "Tiffy" might notice the excess threads! They are on both panels and are used to prop the tips of my fishing rods, when I get around to it I will have to make a couple of plastic fittings to go over the threads. Apart from when I install the windvane blade before I leave the mooring I don't go near the panels.

The figures I quoted for the panels yesterday was with the sun shining on the alloy frames, the sun was more than 90 degrees from the front surface. With the sun shining directly on them they will read up to 17 volts. The measurements I gave were taken off the front terminals of the regulator. So with the panels charging each separate battery, the one panel in the shade was able to maintain a battery at 13.2 volts with a laptop with a max draw of 4 amps running. Doubt whether a laptop just running a nav programme would use anywhere near 4 amps and the stereo and radio would have little drain.

nswsailor
NSW, 1441 posts
30 Apr 2013 3:46PM
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Mmmmm,

I asked my expert and he said that a panel with the face away from the sun, he meant that case when a boat is moored pointing north, is the least efficient position. He also suggested that the panel [see photo above] with the sun on the BACK of it, may also make power! Go figure that one.

Most yachts I've seen with the above arrangement raise their panels to a horizontal position when the wish to charge the batteries.

Never heard of anyone leaving solar panels in the vertical position before. Must be really inefficient.

Charriot
QLD, 880 posts
30 Apr 2013 7:14PM
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Ramona please tell us voltage on the battery with some load on.

If voltage is from 12.6 V to 14.2 the battery is under charge.
If voltage is 11.6 battery has 50% capacity left.
If voltage is under 10.8 V stop using the bat. And start charging.

Safe available range would be from 12.6V down to 11V.

QLDCruiser
QLD, 160 posts
30 Apr 2013 10:21PM
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Sorry guys but the angle of the panel in relation to the sun makes a huge difference to its effectiveness. Why do you think all those house panels are mounted on the north-facing part of the roof?

Given the fact that most boats move around whether sailing or at anchor, my view is that horizontal is best, and as far aft as practical to minimise shading from sails and rigging - even minor shading can cut output almost to zero. Having the angle adjustable in 1 or 2 dimensions could lead to significant gains if you're on the spot to make the adjustment, but for any substantial panel size (ie over about 80W) it will be difficult to devise a mount that is robust enough to cope with high seas and winds.

I have a single 220W panel mounted flat on the bimini frame. I'd like a second one, but would then need a dedicated arch over the bimini, or substantial bimini reinforcement. My one panel doesn't cover our whole power needs, but it does mean we can go for 3-5 days without any other charging (unless it's overcast!).

Voltage tells you nothing about the panel's output, and not a lot about the state of charge. As others have mentioned, current (Amps) is the important measure of a panel's performance. Also be aware that your charge controller will probably be limiting the charging rate unless the battery is severely discharged. In this respect, AGM batteries are better because they can accept a higher charge current without the voltage rising too quickly.

Charriot, a fully-discharged lead-acid battery is about 11.8V. If you follow the battery-manufacturer's recommendations, you should avoid dropping below about 30-50% charged, ie around 12 to 12.2V for a fully-rested open-circuit battery.

MorningBird
NSW, 2674 posts
30 Apr 2013 11:14PM
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I'm with QLDCruiser on solar panel operation. Mine is tied down on the port side of the cabin top, to maximise charge on the mooring. I can easily move it to the stbd side when required, say when returning from Lord Howe.
The previous owner installed a regulator for the panel but I am not sure what type it is. The batteries don't cook and are always charged so I am assuming it is OK.
I am going to make a mount like Ramonas but with a hinged stay so I can swing it to the horizontal when moored/anchored and in benign conditions at sea. A mate with an S&S34 has an 80w panel fixed in position on each side of the cockpit. He lost one to a wave. Made a mess.

Charriot
QLD, 880 posts
1 May 2013 8:50AM
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These are general voltage ranges per cell:
Open-circuit (quiescent) at full charge: 2.1V
Open-circuit at full discharge: 1.95V
Loaded at full discharge: 1.75V




Ramona
NSW, 7637 posts
1 May 2013 8:58AM
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Charriot said...
Ramona please tell us voltage on the battery with some load on.

If voltage is from 12.6 V to 14.2 the battery is under charge.
If voltage is 11.6 battery has 50% capacity left.
If voltage is under 10.8 V stop using the bat. And start charging.

Safe available range would be from 12.6V down to 11V.



From my previous:
"the one panel in the shade was able to maintain a battery at 13.2 volts with a laptop with a max draw of 4 amps running. Doubt whether a laptop just running a nav programme would use anywhere near 4 amps and the stereo and radio would have little drain."

The laptop, HF and VHF plus the stereo is really the only load I have. No real point in having a battery under load higher than 13.2 volts. My yacht is for sailing. There is no way I would cart a pile of SS construction on the rear end with an enormous panel about that would have an excess of charging capacity.
With the previous owner this yacht did 5 Hobart races, 3 Lord Howe races with battery power only. Some of these races were up to 5 days long. I'm sure they only used the HF in Bass Strait and the laptop was only used for short periods. With no fridge and new technologies very little battery power is required.

QLDCruiser
QLD, 160 posts
1 May 2013 11:07AM
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Ramona,

You're right, refrigeration is the killer. But I like my beer cold, and ice in my scotch! Plus somewhere to put the fish. I couldn't entice my wife onto the boat without a fridge on board. It depends greatly on the quality of insulation, but the fridge/freezer on its own will draw least 50AH per day. It puts you into a different league as far as charging requirements go.

Charriot, OK I've seen that particular chart too. But it seems to be based on the "loaded" state, which is ambiguous as voltage will always depend on the current being drawn from the battery. How much current is "loaded"? Run a starter motor and even a fully charged battery will probably drop to 11V or so.

The best way is for the battery to be completely disconnected (ie no charge or discharge) for at least an hour - some say 24h. Then you can get a rough indication of state of charge, based on the following chart examples:

www.energymatters.com.au/components/battery-voltage-discharge/
batteryuniversity.com/learn/article/how_to_measure_state_of_charge
www.batteriesnorthwest.com/batteryschool.cfm?TID=5

Karsten
NSW, 331 posts
2 May 2013 1:43PM
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Charriot said...

e best way how to understand your panel is before the installation
Connect the globe / say 40 W panel 15-25 watts globe/ directly
to the panel and move panel around, different angels - shade atc.



Great tip Charriot.

In respect of horisontal vs vertical mount, it all depends on your energy budget and your priorities, doesn't it?

If you only need top-up charge, the most convernient mount may keep your bank topped up just fine.
If you run a fridge, TV, stereo etc. and draw heavily, and solar is your main re-charge, you may need to prioritise panel orientation and sacrifice deck space or pushpit convenience to get them facing the sun.

Personally I like the idea of being able to deploy more panels when needed at anchor, and take them off when sailing or when stormy weather approaches. So I tend to buy several smaller sized panels. Some of them I just spread around on deck when at anchor, with weatherproof electrical leads. When I move off, they go below.

I do like the idea of flexible panels that you can walk on so you don't have to sacrifice space. But I'm still looking for a robust flexible panel with a good reputation.

About a year ago I read about an an award given for a solar-generating paint. Could be applied to roofs etc, so must be pretty weather proof. Probably not commercial yet but when it comes, it could be an interesting option.



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"Mounting Solar Panels" started by keensailor