What makes Solar panels suitable for marine environment

G

Guardamar

Active Member
Joined
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Location
NE England
www.randpsystems.co.uk
I know solar panels have been done many times, but I can't find what to look for that makes one more suitable than others for the marine environment. I regularly see expensive is best, but what for example is special that makes some better than others for handling the environment.

I am aware of issues of size in a limited space in a small boat like mine (26ft), and can work out suitable wattage.

As the engine gives very little charge (Bukh DV10 LME - no separate alternator etc), a solar panel would be a great help if going on even a few days trip away from shore power.
 
I assume that the aluminium frame and other parts are made from a grade that is suitable for marine use. I know of very few failures that might be attributed to corrosion, so it is probably not an enormous issue.
 
Shadow tolerant solar panels

Go for the shadow tolerant type - something like the Uni-Solar FLX11 or 32.
On a small boat you will find shadows from mast or rigging across the surface most of the day and the shadow tolerant types maintain output despite the individual circuit cells being crossed by shadows.
I would also recommend flexible - my panel is out of the way on top of the hatch cover in front of the sprayhood but even there it occasionally gets knelt on and one would not want a rigid metal framed one there to bash the knee caps. Useful output from the small one shown - weighs only 2 lbs, rated at up to 26 amp-hours per day, often more than the Windmill!
Pleiadesfullsail2.jpg


Robin
Pleiades of Birdham
MXWQ5
 
The last time I saw a solar panel comparison in one of the yottie mags, it was clear that rigid panels (the ones Vyv Cox referred to) offer more bangs for your buck. Yes, their output is more susceptible to halyard shadows than fully flexible ones, but the amount of Ah you get for each £ of outlay more than compensates. 'Semi-rigid' lay somewhere in between in terms of output per £. I'm sure a search on the articles archive page of this site would produce relevant feature articles.

Certainly BP Solar rigid panels stand up very well to the marine environment. Equally, as Pleiades suggests, siting them on a small boat is often more difficult. He's probably more concerned about how those lovely teak decks stand up....:D
 
Pleiades said:
- weighs only 2 lbs, rated at up to 26 amp-hours per day, often more than the Windmill!
Click to expand...

If you are talking about the 10 watt panel I think that your figures are a bit optimistic; that looks more like the weekly output.

But I do agree that the panels do provide useful topping up for a battery. Mine is mounted on a post at the stern where it is away from shadows and clumsy feet.
 
In my experience, some come with more substantial wires than others. One of my panels I wasn't happy with the effectiveness of the sealing around where the wires left the little diode case so I put a blob of CT1 around there to reinforce/waterproof better. The panels I have had (2 x 40W & 1 x 20W) have all been the cheaper end of the market available through ebay. Happy with them all, haven't had any problems with any of them but can't (yet) vouch for their longevity...
 
Solar panels

Oops, yes quite right Rigger, about 26 pamp hours per week - but still easily enough to run a bilge pump when boat is not in use and charge the batteries. The rigid units do kick out more but not if covered as mine is by the boom most of the time.

Cheers,
Robin
Pleiades of Birdham
MXWQ5
 
Thanks for replies. Looks like I shouldn't worry too much about corrosion or seawater / wind / shaking breaking down the panels.

My choices seem to be:
1. Get small wattage Amorphous flexible panel to just top up the batteries while I'm away (which is most of the year) as I could place it anywhere.
2. Get a bigger panel (say 30 or 50 W) - probably polycrystaline maybe semi flexible with regulator that will extend the time I'm able to cruise without shore power, given I only tend to use lights, VHF, log and Chartplotter (biggest user). Then my biggest issue is where to site it, as I don't have any areas that lend themselves to a large panel.

One question it raises. Is fire risk a problem. I tried a cheap small plug in panel (sold for charging cars) inside a side window to trickle charge, and it got so hot it almost burnt my hand to touch. It was placed between an acrylic side window and a curtain, but we are talking Spain in June. Even without the curtain it was scorching. I stopped using it in case it lit something, and I wasn't sure that panel would be OK outside. But if is gets that hot, is placing a better quality one direct onto GRP OK if not in a box that allows ventilation?
 
Guardamar said:
Thanks for replies. Looks like I shouldn't worry too much about corrosion or seawater / wind / shaking breaking down the panels.

My choices seem to be:
1. Get small wattage Amorphous flexible panel to just top up the batteries while I'm away (which is most of the year) as I could place it anywhere.
2. Get a bigger panel (say 30 or 50 W) - probably polycrystaline maybe semi flexible with regulator that will extend the time I'm able to cruise without shore power, given I only tend to use lights, VHF, log and Chartplotter (biggest user). Then my biggest issue is where to site it, as I don't have any areas that lend themselves to a large panel.
Click to expand...

I owned a 25 foot yacht several years ago and used a rigid 75w panel that stayed in the V-berth when sailing. At anchor, or when storing the boat, I pulled it up through the front hatch and clipped it in the Pulpit. The system worked well. Although the panel was not always out, the relatively large size meant it charged the batteries quickly for our electricity consumption. This idea may work for you maybe even with a smaller panel if your needs are very modest.

Guardamar said:
One question it raises. Is fire risk a problem. I tried a cheap small plug in panel (sold for charging cars) inside a side window to trickle charge, and it got so hot it almost burnt my hand to touch. It was placed between an acrylic side window and a curtain, but we are talking Spain in June. Even without the curtain it was scorching. I stopped using it in case it lit something, and I wasn't sure that panel would be OK outside. But if is gets that hot, is placing a better quality one direct onto GRP OK if not in a box that allows ventilation?
Click to expand...
Solar panels do need air flow if they get hot the output falls. The cell temperature is about 40 deg C even with ventilation.
 
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Solar panels - air gap underneath

I needed the semi flexible type because my panel is fitted on the sliding main hatch cover which is gently curved. But it is not stuck down - it is held by a screw at each corner through a reinforeced steel eyelet and there is therefore a full surface air/ water gap underneath it. I definitely would not recommend sticking it down. However it is to all intents and purposes a fit and forget item - maintenance free and no worries because it is connected to a regulator/charge controller (together with the wind mill). I would not leave the portable car accessory type models permanently fitted because of over overheating risk. This picture shows the mounting slightly more clearly.
Dawn096.jpg


Cheers
Robin
Pleiades of Birdham
MXWQ5
 
I installed the type discussed by Pleiades to my coachroof in 1996, using the same method. There is a slight air gap between it and the deck. It has never been removed or maintained in any way since and continues to perform well. There is slight evidence of delamination of the surface layer, which is cloudy in places, but otherwise all seems to be well. The boat has been in the Med for the past six or seven years, so the panel sees some high temperatures.
 
Guardamar said:
I assume air over just the outside of the panel is sufficient cooling, otherwise the panels that glue directly to the deck would be very inefficient, even if not dangerously hot.
Click to expand...

The bumf that came with my semi-flex panels advocated a small air gap beaneath the panels. As noelex wrote, this is because efficiency drops above a certain temperature, not because of any fire risk. They'll still work if directly bonded, just not quite so well at high temps. I've never heard of one spontaineously combusting.
 
IMHO there are two essential stages to creating a marine suitable solr panel.


1. Add a label to existing panel stating "suitable for marine use".

2. Double the price.
 
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