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Dunworkin

Solar Panels

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Dear all,

 

happy new year!

 

Whilst not wishing to reignite any old, and much debated hot potatoes, I would appreciate the wisdom of Solomon on Solar panels. We are looking to fit solar to our 58 foot boat this spring. We’ve been advised that the semi flexible panels, glued to the roof would be the best option, but have more recently been cautioned that the best set up is one that allows air to reach both sides of the panel, suggesting the traditional A frame set up is best.

 

I would appreciate any advise or thoughts on this as we don’t want to make a costly mistake.

 

many thanks

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You can't point a sticky panel at the sun, makes a big difference to the output when the sun is not too bright which is most of the time in UK

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I set a budget, decided on battery bank, and worked back from there, in my case I wanted as much bang for my buck as practical. Bought a kit from Bimble, thus getting controller 40 amp matched to 550 watts of solar to feed the leisure batteries. The tilting, slotted s/s brackets are quite expensive, but are more efficacious than flat/flexi. I also think they are tried and tested, and cheaper!

Edited by LadyG

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Do not fit semi flexible panels, they do not last long on boat tops and will destroy the paint underneath.

Either splash out on amorphous roll on ones, or use rigid monocrystalline panels for most oomph for size.

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13 minutes ago, matty40s said:

Do not fit semi flexible panels, they do not last long on boat tops and will destroy the paint underneath.

Either splash out on amorphous roll on ones, or use rigid monocrystalline panels for most oomph for size.

I agree.  You will get better results and more for your money from rigid panels.

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Tilting mounts enable you to angle the panels, but are not much use if the panels tilt sideways and the sun is directly ahead or astern. To make the most of them you will have to readjust the panels through the day. Tilted panels increase the airdraft, may be a problem at low bridges and are more likely to catch ropes when boating.

Flat mounted rigid panels avoid most of these disadvantages. True, you will never get the full nominal panel output, but just double up on the panels to compensate.  Tracer solar controllers (and maybe others) allow the use of more nominal capacity than the controller rating, and simply limit the output. So you could fit (say) two 240W panels to a 20A controller, and still generate up to 240W on a bright day (without damaging the controller).

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Horizontal panels work better at capturing diffuse light when it's cloudy. Depending on your circumstances, it may be important to optimise for crappy cloudy weather rather than for bright sunlight. The derating of panels when they get hot may also be unimportant if you want to optimise for winter days when it's cold. The Vetus calculator is useful for designing a system and you can enter your choice of panel parameters.

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Thanks for your replies. We had originally ruled  out the tilting panels on cosmetic grounds, but have been a bit bothered recently about what happens if you need a repaint on the roof, Andy what happens if they were to peel away etc.  The air draft has been suggested as a major advantage of the tilting panels, but then equally people seem keen to suggest that we go down the flat, stick on route.

 

i think that on reflection, taking in to account the “bang for your buck” argument, we may stay safe and go with the A frame mounting. We aren’t live aboard, and so will really only be looking to the sun during the warmer months.

 

 

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How can an A frame sticking up give more air daft that little brackets mounting the panel horizontally on the roof? I know of few experienced boaters who advise stick on panels for canal boats. Yachts  where there are ropes, sheets and lines waving about that could easily get trapped under a bracketed panel yes, but not narrow boats or even cruisers.

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What about mounting a big panel, the centre of  which upon a big football, it could then be tilted anyway, which way. Better than my plan of growing Sunflowers and mounting lots of small panels on them just below the flower which always swivels to track the sun. :closedeyes:

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15 minutes ago, bizzard said:

What about mounting a big panel, the centre of  which upon a big football, it could then be tilted anyway, which way. Better than my plan of growing Sunflowers and mounting lots of small panels on them just below the flower which always swivels to track the sun. :closedeyes:

I believe this plan was used a few years ago by a member who then became an a member with a wide beam on the K&A.

The problem with swivelling and tilting panels is you spend all day going back and moving them to track the sun

 

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6 minutes ago, matty40s said:

 

The problem with swivelling and tilting panels is you spend all day going back and moving them to track the sun

 

I'm sure the electronics wizzards could come up with a means to automate this. But it would probably use more power than it generates!

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1 minute ago, David Mack said:

I'm sure the electronics wizzards could come up with a means to automate this. But it would probably use more power than it generates!

It seems to be worth the effort for sunflowers.

  • Haha 1

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31 minutes ago, David Mack said:

I'm sure the electronics wizzards could come up with a means to automate this. But it would probably use more power than it generates!

It’s not particularly difficult or expensive but it is somewhat bulky and inevitably a bit fragile. 

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I’m thinking of mounting semi flexible panels using magnetic tape in a herringbone pattern on the back. That way there’s a gap to allow water to drain and provide some insulation from the steelwork. They can also be taken off in the winter for paint purposes if required. 
 

I too don’t like the look of solid panels and I’m not keen on having them sticking up to catch ropes etc on. 

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I think that the regular adjustment won’t be a deal breaker...when we are out cruising we’ll have plenty of opportunity to keep an eye out and the more I read the less attractive the semi flex panels are becoming. 

 

If i understand the advice correctly, the horizontal panels that are raised, but run parallel to the roof maybe a sound compromise?

 

many thanks

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8 minutes ago, Dunworkin said:

If i understand the advice correctly, the horizontal panels that are raised, but run parallel to the roof maybe a sound compromise?

 

If I were putting panels on my nb, which I'm not, I'd be tempted to put them into a wooden surround (like a roof box) with a snug fit. That would avoid snagging of ropes etc and could hide a hinge mechanism to tilt them (in two axes if your imagination runs that far).

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I didn't like the idea of gluing flexible panels to the roof and favoured rigid panels. But also did not really want to drill into the roof to fit brackets.

So I have made up brackets for each corner of the panels with magnets. Its a surprisingly solid fixture. It is also possible to tilt the panels by lifting one side and propping with a short length of timber.

 

Edited by Big Bob W
  • Greenie 1

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It’s amazing isn’t it...how many different solutions other boaters have come up with....I really like the magnet idea which saves holes in the roof. Presumably though there will have to be some holes to connect the cabling between the panels and the electronic that will live in the engine room?

 

Also, does the magnetically approach heighten the risk of theft?

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2 minutes ago, Dunworkin said:

It’s amazing isn’t it...how many different solutions other boaters have come up with....I really like the magnet idea which saves holes in the roof. Presumably though there will have to be some holes to connect the cabling between the panels and the electronic that will live in the engine room?

 

Also, does the magnetically approach heighten the risk of theft?

Initially I was a bit concerned on the security aspect of the magnetic mounts but unless you look rally closely, the mounts look as though they are screwed on. The cables route into the boat through one of the mushroom vents.

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11 minutes ago, Big Bob W said:

Initially I was a bit concerned on the security aspect of the magnetic mounts but unless you look rally closely, the mounts look as though they are screwed on. The cables route into the boat through one of the mushroom vents.

Many thanks...that really does offer some food for thought...I feel a wee dram or 2 coming on this evening as I mull over what’s best for us....????

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Get a good MPPT controller not the Tracer/EPever although they work fine on a sunny day they do not perform well in poor light shady conditions.   Wire the panels in parallel, which may mean thicker cable, because then when one little bit gets a shadow or a rope across it you only reduce the output from that panel not all of them.  Have fat cables to the battery from the controller to avoid volt drop.  Although not required a fuse or switch, between the panels and controller allows you to switch off the power to work on the system, otherwise you have to do it at night or cover the panels up.

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