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Old 11-09-2012, 04:24 AM   #1
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Default Flexible solar panels on coachhouse roof?

Hi,

Has anyone had any experience with mounting and using flexible solar panels somewhere like on a coachhouse roof? My coachhouse roof area is quite large, and although it's under the boom seems ideal for solar panels, the only problem being that I have to walk on them periodically to pack and unpack the mainsail.

Here is an example of one I'm looking at:

1X100W Semi Flexible solar panel-in Solar Cells, Solar Panel from Electrical Equipment & Supplies on Aliexpress.com
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Old 11-09-2012, 04:38 PM   #2
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Two things: "under the boom seems ideal" ...NOT

Under NOTHING is ideal. Output of most panels is severely reduced when even partial shading occurs. Kind of the "weakest link in the chain" effect. Cells are arranged in strings and any "unlit" cell gates the output of the whole string. Different materials like mono- vs. polycrystalline silicon etc. have differing susceptibility to shade or cloudy conditions, but they ALL have it. "Shade-tolerant" is marketing speak oxymoronese. Yes, they won't self-destruct with shade but don't expect much output either.

Item two: roll-up panels have a hard time getting rid of the heat, the price to pay with a dark surface. Good installation will promote easy ventilation, i.e. off-the-roof mounting at an angle, so that wind, convection and radiation can dissipate the heat.

Reason why: high temperature reduces output substantially.

Price is maybe item 3: The "walk-on" styles seem to have not only much lower efficiencies but cost-per-watt is much higher. You might be better off with rail-mounted panels. Even mounted vertically they pick up a lot of sea-reflections, unlike on land where that is a no-no. ( OK, nix the N & S pole ) Shading is not an issue on the rails but yes, one side is always likely to be a poor performer. Mine sit at 45 deg. near the stern and often still run >80% of max. theoretical output over at least a few daylight hours. Others mount them on top of the davits. Windage and weight aloft can become issues, but you are likely an "anchoring cruiser" anyway. Right?

Now, if Mama still likes it, go right ahead with plan A. You will have less windage and the whole shebang will be out of the way. Plus, you can dance flaming flamenco zapateados on your coach roof... and now that is one thing I cannot do with my install.

Ivo on s/v Linnupesa
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Old 11-10-2012, 05:11 AM   #3
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I already have one overhead panel, it's getting upsized but still needs extra capacity. There's no way I can mount anything else aloft without taking some things down (little things, like the mast or the boom, surely nobody needs those ...)

Mounting on the rails seems interesting -- by that you mean vertically along the guard rails, between the stanchion posts? I've never seen this done. With flexible/removable panels it might be an option, but not with the aluminium backed panels.

I figure that with 2 panels on the coachhouse roof under the boom, at least one will generate some energy since the shadow can't be in both directions at once.

I have no intention of dancing on the coachhouse roof (that's what the foredeck is for) but mounting glass topped panels up there is not an option because I do need to stand up there to unpack or repack the main.

I have no davits, that would get in the way of the windvane. If I did then I'd probably mount panels up there.
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Old 11-12-2012, 05:43 AM   #4
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Smile Mounting solar panels to stanchions

Stanchion mount in my own case consists of a horizontal stainless steel tube continuing from the rear pulpit above the lifelines to the next stanchion forward. This tube is a fixed axis on which two plastic tube clamps swivel. These clamps in turn are bolted to two aluminum angle bars that are attached cross-wise to the rear of the panel. U-bolts fix the tube to the stanchions. The panels fit lengthwise and can be tilted in- or out-board. In practice, they sit at 45 deg almost all the time.

The 1.25" wide ( a side ) angle bars are very sturdy and add rigidity. Holding the panel either near horizontal or at a 45deg. inclination is by two telescoping tubular struts. The lower strut end is deck mounted to more L-shape aluminum, the other end is attached to the OUTER side of the aforementioned cross-bar. Slits and hose clamps take care of adjustment and through-bolts hold the end attachments.

When under way in open water the panels are at 45 deg. At a pier or docking in tight quarters they can be brought into a near-vertical position, outside the lifelines. ( or they stick out a bit and are asking for trouble ) In very high winds I prefer them more horizontal, to reduce windage.

I've seen others mount their panels vertically without scope for any adjustment. The tiltable option allows a bit more efficiency. Horizontal panels utilize the higher noon sun angles more effectively and provide better daily output. It is true the panels impede walking space somewhat but then again they provide most of my daily power needs, quietly too.

I hope this info helps.

Ivo s/v Linnupesa
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Old 11-12-2012, 06:39 AM   #5
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Thanks Ivo, that's extremely helpful. I might look at mounting a couple aft, either side of the pushpit, and a couple of flexible ones forward. I was looking at getting some netting around the guardrails anyway, to assist keeping the ship's cat on board, so some flexible panels mounted outside of the netting wouldn't get in anyone's way.
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Old 11-12-2012, 10:09 AM   #6
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If mounting on a solid surface, such as a coach house roof, it is best to use solid panels and mount them clear of the surface on brackets. Putting the amorphous panels direct onto the roof is akin to painting the roof black. Okay in colder climes, but in tropical waters, it will radiate a lot of heat into the cockpit.
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Old 11-12-2012, 10:36 AM   #7
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Quote:
Originally Posted by Auzzee View Post
If mounting on a solid surface, such as a coach house roof, it is best to use solid panels and mount them clear of the surface on brackets. Putting the amorphous panels direct onto the roof is akin to painting the roof black. Okay in colder climes, but in tropical waters, it will radiate a lot of heat into the cockpit.
I don't think that's really going to be an issue, the coachhouse roof is a 5cm + thick chunk of wood. Getting anything to radiate through it is going to be hard.

Nonetheless I think I've decided on the stanchion mount option as suggested by Ivo. I might get a local solar tech to take a look anyway.
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Old 11-12-2012, 03:48 PM   #8
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Delatbabeloosa, your matey Auzzie has a very valid point about the heat.

Even with a 2" thick roof, it'll work it's way through or store the Btu's for an uncomfortably warm night. Apart from that, check the spec sheet of the panels for their derating per deg. of heat rise. Then consider the panel surface to get too hot to touch. Easily 150deg. F or more is just my WAG, especially if a thick "walk-over" coating is applied.

You mentioned your Pussy-gato aboard: Cat on a hot tin roof comes to mind.

If $'s are no object, many small panels will be more effective at dealing with partial shade. The "but" is the extra wiring and mounting hassles you'd get. The "commercial" racers all go for the flex panels but then those Ellison-tykes don't count their change either.

Ivo
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