Solar panel mounting (on roof)

[Johny London]

The panels I've got are about 1500x700mm, so centrally mounted lengthways I can still walk past them on each side - though the roof is curving away at the edges and it's not as good as walking in the very middle - but I'll use some of that grippy stuff (either sand or the strip) to make the walk ways safer.

Being single handed I really need access and not have ropes etc getting caught up, otherwise I would have gone for wider, more powerful panels, but these are 150w anyway. two to start with, two more late, and if needed I can even get another two on.

I'm just waiting for that bracket seller to get back to me with the dimensions - I just want to check they are tall enough to cope with the curve of the roof.

[Jen-in-Wellies]

I found two centre ropes, one running down each side of the roof where necessary once it was populated with solar panels. That way you are not trying to flick a single rope from one side to the other and getting it caught on panels. On my boat I kept the central attachment ring and used fairleads on each handrail to direct the ropes. Other ways of arranging them may suit your boat better.
Jen

 

[Peter Reed]

Taxi  roof signs hold well at 70mph+ on motorways. One of these at each corner of a nb roof mounted panel,I'm pretty sure will suffice. https://www.deltataxisigns.com/product.php/2523067/

[Psycloud]

2 hours ago, Peter Reed said:

Taxi  roof signs hold well at 70mph+ on motorways. One of these at each corner of a nb roof mounted panel,I'm pretty sure will suffice. https://www.deltataxisigns.com/product.php/2523067/

They look good.  I wonder how they would hold through a textured roof finish?  Cheaper version on eBay http://www.ebay.co.uk/itm/2-of-Vehicle-MagPad1-super-strong-magnet-for-roof-signs-taxi-driving-school/182286353335

[rusty69]

5 minutes ago, Psycloud said:

They look good.  I wonder how they would hold through a textured roof finish?  Cheaper version on eBay http://www.ebay.co.uk/itm/2-of-Vehicle-MagPad1-super-strong-magnet-for-roof-signs-taxi-driving-school/182286353335

The pot magnets I used were 68kg pull (not sure they will be used at 70mph) .They have been on non textured roof for over 4 years. 

[Psycloud]

6 minutes ago, rusty69 said:

The pot magnets I used were 68kg pull (not sure they will be used at 70mph) .They have been on non textured roof for over 4 years. 

What diameter were yours please?

 

[rusty69]

38 minutes ago, Psycloud said:

What diameter were yours please?

 

100mm I think. The larger diameter gives a bit more scope for adjustment if you have a curved roof. 

 

Put some protection between magnet an roof to protect paint. 

Edited June 8, 2017 by rusty69

[jddevel]

Spoke to these people some time ago inquiring whether I could use magnets to fit pole/plank support on my sailaway roof. Some really powerful magnets.

https://www.first4magnets.com/100kg-and-over-strength-magnets-t188

[rusty69]

9 minutes ago, jddevel said:

Spoke to these people some time ago inquiring whether I could use magnets to fit pole/plank support on my sailaway roof. Some really powerful magnets.

https://www.first4magnets.com/100kg-and-over-strength-magnrets-t188

They certainly are powerful, maybe too powerful. 

I have used these 

http://e-magnetsuk.com/magnet_products/work_holding_magnets/pot_magnets/through_hole_mounting.aspx

 

Theres also a place near Berkhampstead on the GU that sells magnets 

[Bewildered]

19 hours ago, Jen-in-Wellies said:

I found two centre ropes, one running down each side of the roof where necessary once it was populated with solar panels. That way you are not trying to flick a single rope from one side to the other and getting it caught on panels. On my boat I kept the central attachment ring and used fairleads on each handrail to direct the ropes. Other ways of arranging them may suit your boat better.
Jen

 

The other reason for having two ropes and not flicking one from side to side over the panels is because the ropes get wet and dirty and end up leaving tracks all over the panels. This means you need to clean your panels more often in order to get the best out of them.

[Bewildered]

23 hours ago, Señor Chris said:

How do you fix the boxes to the roof?

I would have thought the decking on its own is heavy enough to hold down panels. Unless of course you are silly enough to leave the panels propped up at 45 degrees in high winds. Most people use the roof boxes to store logs and coal. Best not to build them with too much of an air gap under the sides to let the wind in though.

[Johny London]

I've now mounted the panels - with the Z brackets which look very neat and had just enough height to cater for the roof curvature - though I did have to bend them all in a vice to get that slight extra angle so that they would sit really well. I stuck them with silicon and they seem very secure indeed, so I'll see how they get on. It's a very neat, low profile look and I'm happy.

Cables I just ran on the roof (can always look at trying to get them in through a mushroom and along in the ceiling later on I suppose) justa couple of gromets in the side of the hatch frame and in they come.

There is enough room to walk past them but I must get the grippy stuff as well as another centre line.

I've only seen 5-6 amps out of the (150w+150w) pair so far in the sunlight though Still it's keeping the beer cold.

[Jess--]

On 14/07/2017 at 16:59, Johny London said:

I've only seen 5-6 amps out of the (150w+150w) pair so far in the sunlight though Still it's keeping the beer cold.

that seems low for a 12v system (unless your batteries are already fairly well charged)

I get just under 10A from a single 140w panel into low batteries (reducing over time to 0 as the batteries charge)

[Debs]

We have not long got our boat but the first thing we did was put solar panels on the roof! We've had solid solar panels but we really like the ones we have now! Apparently, they are dimpled so that they catch the light, regardless of where you are. They can also be walked on so, not only do they lay flat on the roof but they catch the light , no matter where you're moored!

[Johny London]

18 hours ago, Jess-- said:

that seems low for a 12v system (unless your batteries are already fairly well charged)

I get just under 10A from a single 140w panel into low batteries (reducing over time to 0 as the batteries charge)

Yes it does seem low doesn't it? Today in bright sun the managed up to 6a at one point, but that was it - I would have pretty much expected the full 20a. I might have to investigate further - perhaps try running with one at a time to see if there is any difference in them. Or if anyone has any other ideas? Perhaps I've not got the charge controller set up correctly - it usually shows them at 13 or 14 v only. They are flat mounted but still.

I had hoped for better.

[WotEver]

3 minutes ago, Johny London said:

Perhaps I've not got the charge controller set up correctly - it usually shows them at 13 or 14 v only.

It is an MPPT controller? Those voltages sound more like PWM. 

[Jak]

Yes, that's not right. In bright sunlight I've seen almost 20a from a pair of 100w panels when testing them in my garden prior to fitting...

[Johny London]

Fixed! I connected one panel at a time and one gave 18v the other zero. I opened the waterproof connection box under the panel and found that neither flat wire from the panel was connected to its corresponding terminals!!! No attempt whatsoever had been made to connect them! I used a thick ish bit of wire as the connecting strips had been cut off too short, soldered up nicely. Obviously, these panels are completely untested. I will be writing to the supplier.

Now have lots of volts and a little current as it's cloudy and I was in any case running the engine so batts were up to 13v already. I expect good results tomorrow

[WotEver]

25 minutes ago, Johny London said:

Fixed!

Result!

[Johny London]

Today in bright sun I'm getting... (on my epever Tracer 20a controller)

PV      30v, 5.2a, 2kwh

Batt    13.1v, 12.5a, 25c

Load   0.1a, 0kw, 117, 2n

Does that sound ok? It's 2x150w panels so I would have hoped to see it maxing out at 20a but maybe the batteries aren't low enough to take the lot? I switched on a load (in the mains, not off the mppt controller) and it showed 14a to the battery. Will see what happens in the mid day sun.

 

 

[Chewbacka]

9 minutes ago, Johny London said:

Today in bright sun I'm getting... (on my epever Tracer 20a controller)

PV      30v, 5.2a, 2kwh

Batt    13.1v, 12.5a, 25c

Load   0.1a, 0kw, 117, 2n

Does that sound ok? It's 2x150w panels so I would have hoped to see it maxing out at 20a but maybe the batteries aren't low enough to take the lot? I switched on a load (in the mains, not off the mppt controller) and it showed 14a to the battery. Will see what happens in the mid day sun.

 

 

13.1V at 12.5A is about 165W which with the sun still a bit low in the sky (13:00 BST is peak time) doesn't sound to bad if your panels are mounted horizontally.  If the panels are tilted up it would help boost the output, but ONLY if the panels (or boat) is rotated to point the panels directly at the sun.

Added - Interesting to see what you get at 13:00 assuming it is sunny :-)

 - 

Edited July 17, 2017 by Chewbacka

[Johny London]

Yes, I'll post shortly, in the meantime, here is the picture of how the terminals were simply left unconnected on the faulty panel. The two flat silver bits needed to go to the very left and right terminals, they'd been cut off short and left floating!

[Johny London]

Again I saw 15a briefly, adding a 500w load (off the inverter not the load terminals) didn't really make much difference. Switching off the output to the load seemed to help a bit but basically its around 13.5a normally in full mid day sun - bit disappointing really. I would have expected the full 20a as the panels can deliver (?) 26a I think. Even though they are laid flat.

The next pair I get will be a different brand.

Edit to say that I'm planning on connecting them individually to compare outputs. I'll wait till there is not much sun as I thought I heard somewhere not to let them run unconnected?

That leads me to my question - could the panel that was unconnected internally have become damaged by being in the sun for a few days?

Or is it it that the batteries just wont draw as much as the panels could provide (that I'm only seeing about 13.5a) - I did try adding load but no different.

Edited July 18, 2017 by Johny London
more thoughts

[Chewbacka]

On 2017-7-17 at 14:17, Johny London said:

Again I saw 15a briefly, adding a 500w load (off the inverter not the load terminals) didn't really make much difference. Switching off the output to the load seemed to help a bit but basically its around 13.5a normally in full mid day sun - bit disappointing really. I would have expected the full 20a as the panels can deliver (?) 26a I think. Even though they are laid flat.

The next pair I get will be a different brand.

Edit to say that I'm planning on connecting them individually to compare outputs. I'll wait till there is not much sun as I thought I heard somewhere not to let them run unconnected?

That leads me to my question - could the panel that was unconnected internally have become damaged by being in the sun for a few days?

Or is it it that the batteries just wont draw as much as the panels could provide (that I'm only seeing about 13.5a) - I did try adding load but no different.

At this time of year the sun at it's peak is about 60 degrees above the horizon, which is 30 degrees below vertical.  This means that the effective area of a solar panel at mid day is reduced by the ratio of cosine 30 degrees - which is a reduction down to about 85%.  Now your panel pair rated output is 300W which at 12v is a current of 25A ignoring mppt controller losses, but as they are flat the panel collecting area is effectively reduced as explained to 85%.  So 300 x 0.85 = 255W which at 12v is 21A.   So your flat panels at mid day in June will not go above 21A at 12V and that assumes a perfectly cloudless sky etc, a bit of haze and it will reduce.  Obviously earlier or later in the day the sun is lower and so the panel output reduction is greater.  Flat panels can also get a bit grubby, and that can cause a significant reduction in output as well.

So you said you briefly saw 15A, but did not give a voltage, but if it was 13.5V, that would be 202W which doesn't sound too bad to me.

For your interest the sun at the end of September only rises to about 30 degrees above the horizon, which is 60 degrees below vertical, the cosine of which being 0.5, so the max output from your flat panels will be about 50% (so about 12.5A)  and that ignores the fact that sunlight now passes through a lot more of the atmosphere which further reduces the sunlight arriving onto your panels.

However tilting the panels to catch the sun better only works when the sun is directly in line, and of course it rises in the east and moves through 180 degrees before setting in the west, so again much of the time the sun will be at a glancing angle which effectively reduces the collecting area, and therefore power.

I did see a posh satellite dish that had a small panel on the back which tracked the sun in both the vertical and horizontal which would maximise the output, but obviously doesn't work if watching TV and could not manage a big panel, so probably an expensive toy.

Edited July 18, 2017 by Chewbacka

[stegra]

At Crick I spent some time chatting with a guy from the Electric Boat Association. He mentioned that many members had found that solar panels mounted on the hull sides averaged significantly higher outputs than horizontally mounted panels. This was accredited to the reflective effect of the water. The boat moored there with such panels looked hideous (My opinion, sorry; I would never do that to my boat).

However, this did get me thinking about the feasibility of using mirrors to increase the available light, rather than tilting the panels.