Multiple smaller size solar panels or one large standard rooftop module ?

[umu]

We are planning to upgrade our solar panel installation.

The panels shall be mounted on the gantry which could fit either 3 smaller (100x67cm) 100w each panels or one large 330w rooftop panel (155x100cm).
Apart from the price point the higher system voltage/less drop on the cables and much less weight (more than 10kg less) are attractive.

But I am not sure if the large modules could be a problem due to "mechanical issues"
- mounted on two bars/4 points at the panel and wind load
- vibration and torsion of the boat/gantry

Any input in regards to or experience with mounting such rooftop size panels on the yacht very much appreciated!

 

[PabloPicasso]

Another factor is reliability. One panel, one issue = no power. If one of you're three panel breaks it's a reduction in power only.

 

[Norman_E]

Standard rooftop solar panels are typically 250 watts or more, and have an output voltage which is too high for anything other than an MPPT controller. They are also pretty big, and and typically weigh over 40 pounds. The size of them can make for difficult installation on a typical yacht gantry. I think the biggest panels most people mount on yacht gantries are 100 watt. I think two or more smaller panels are a better idea despite the lower cost per watt of domestic panels.

 

[umu]

Standard rooftop solar panels are typically 250 watts or more, and have an output voltage which is too high for anything other than an MPPT controller. They are also pretty big, and and typically weigh over 40 pounds. The size of them can make for difficult installation on a typical yacht gantry. I think the biggest panels most people mount on yacht gantries are 100 watt. I think two or more smaller panels are a better idea despite the lower cost per watt of domestic panels.

While being really large - making handling challenging - the footprint of the rooftop panel is smaller than the 3 smaller panels I am considering combined - even with its higher wattage of 335 Watt vs 3*100=300Watt.
Also the weight of the large panel is 20 pounds less than that of the 3 small combined.

 

[William_H]

As said the domestic type panels are usually 40 v open circuit compared to "12v" panels which are 20 v open circuit. So you need an MPPT type controller to convert 36 or so max power point voltage to your 14v needs. But domestic panels can be much cheaper than the "12v" recreational type panels.
Now around here solar PV systems to augment mains AC are very popular. Perhaps 1 in 5 houses have it. Our yacht club has 40kw on the roof. Anyway I understand that electricity authorities will not allow second hand panels to be installed. (connected to AC mains) So if a house gets demolished that has panels they are of no real value. It might just be worth enquiring of house demolishers if they ever see any old solar panels. Considering that a house might have 16 panels, any one of which can give 180 to 200w. olewill

 

[RichardS]

Personally, I went for the largest panel(s) I could fit in the space available.

I reckon that the cabling losses, weight gains, mounting complexity, expense etc all mitigate in favour of "going large" and outweigh the lack of failure redundancy.

If shading is a problem that would be the only factor which would make me re-consider as I could then play around with placement and serial/parallel configurations to minimise losses. If shading is not an issue these options are obviously of no interest.

Richard

 

[umu]

@Richard:
What size are the panels you fitted ?
How did you mount them ? Did you use the standard 4 mounting holes or some additional stiffening construction underneath?
Can flexing of the panels become a problem at that size ?

 

[RichardS]

@Richard:
What size are the panels you fitted ?
How did you mount them ? Did you use the standard 4 mounting holes or some additional stiffening construction underneath?
Can flexing of the panels become a problem at that size ?

Hi Umu

I didn't use house panels because I needed some flexibility to fit them to a curved hard bimini so was really addressing the multiple / single panel question.

I chose the largest semi-flexible panels which would fit on each side of the bimini which were 100W panels and I had room to fit 4 of that size. They are each 560mm x 1200mm x 3mm

I just mounted them with self-tapping screws in the holes in the outer edge but I was just screwing into fibreglass so fairly straightforward.

Richard

 

[De.windhoos]

wouldn’t 3 panels be more effective? I thought that shadow striking part of a panel affects the output of the total panel. Given that wouldn’t it be better to have multiple panels?

 

[umu]

wouldn’t 3 panels be more effective? I thought that shadow striking part of a panel affects the output of the total panel. Given that wouldn’t it be better to have multiple panels?

Definitely a point to consider.
However it would be mounted in such way that only the backstay may from time to time cast a shadow. Which (tried it with a boat hook across the old panels) has no significant impact.