Biggest Solar Panels...

[nelly]

Also, at least in my experience, what you put up there is going to have to come down... at some point. To clean off bird crap or to fix something.

So making it light is worth it. I used 3/16" thick aluminum tube to build my frame that holds the panels together, and I think it was overkill. I have two 200w panels and it is manageable, but just barely. Weight adds up fast.

I did lash this frame to the arch which I think is a good idea. Easier than bolting it down, and easier to remove, maintain, inspect. And my arch is aluminum so putting SS bolts there can be done (the arch does use SS hardware) but good to avoid IMO.

The two 200w panels work well, they mostly get me through with fairly heavy (autopilot) electronics + fridge + freezer, but sometimes I need a little more power. No AC or heavy inverter use.

[Rohan]

Originally Posted by HarrisonM

You are right about the radar shading the panels... I did not quite think of that... Uggggg

One advantage of having multiple smaller panels is that you can wire them in parallel, so if a shadow falls across one, it won't affect the output of the other panels.

If you don't have enough surface area for the solar panels you want, consider supplementing them with a wind generator.

[bdgWesternMass]

I don't see anyone else mentioning this so I will. The Canadian solar panels have such large outputs not necessarily due to efficiency but physical size.

It's possible that more smaller panels is a better approach as others have pointed out. A couple of quick reasons are

such a large flat panel will have less prime time sun
shadows on the panel will have a large effect
larger surface area more windage

resons more smaller could be better

smaller panels can be installed to at varying degrees to have exposure over the longer day
a shadow on one cell on one panel will have a smaller effect
less windage

[s/v Jedi]

No, the large panels put the others to shame, perform much better.

Shading problems occur when you put these in parallel. They must be put in series or a dedicated controller per panel.

These panels are actually multiple strings in series, so compare to multiple small panels. During partial shading, the diodes guide current around the shaded string.

[Rohan]

Originally Posted by s/v Jedi

Shading problems occur when you put these in parallel. They must be put in series or a dedicated controller per panel.

I think it's the other way around, isn't it? In series, then one shadow can block almost all the solar energy. In parallel, it will only block the panel that's shaded.

[nelly]

There are a few things to consider when choosing a parallel vs series installation:

In series, the output voltage will be the sum of all the panels, but the amps will be equal to the lowest outputting panel.

In series, if shade covers one panel it will impact performance of all the panels wired in series. But, higher voltages mean you can get away with smaller gauge wires.

Wired in parallel, it is the opposite: the voltages will equal the lowest of the array and the amps will be the sum of all output.

However, if you have 500w+ panels, why not size a controller per panel? I have 200w and size a controller for each. This is a little extra cost, but completely avoids the issue of wiring, and adds significant redundancy to the system.

[s/v Jedi]

Originally Posted by Rohan

I think it's the other way around, isn't it? In series, then one shadow can block almost all the solar energy. In parallel, it will only block the panel that's shaded.

No, that is a myth from 30 years ago when solar panels for boats were new. It is persistent, even though they have been putting in bypass diodes for decades.

When you have two large panels in parallel and one of them gets partial shading, triggering a bypass diode… then this partially shaded panel has a lower voltage and the other panel tries to dump charge into it. Even when that is blocked, the array will never perform because it has lost 50% output.

The same panels in series only lower output voltage for that single string, which may only be 1/3 of that panel and the rest just keeps on going.

[wholybee]

Multiple smaller panels are usually preferable. Redundancy, better performance in shading, and in parallel will be lower voltage. 50V panels introduce some safety concerns.

[s/v Jedi]

Originally Posted by odonnellryan

There are a few things to consider when choosing a parallel vs series installation:

In series, the output voltage will be the sum of all the panels, but the amps will be equal to the lowest outputting panel.

In series, if shade covers one panel it will impact performance of all the panels wired in series. But, higher voltages mean you can get away with smaller gauge wires.

Wired in parallel, it is the opposite: the voltages will equal the lowest of the array and the amps will be the sum of all output.

However, if you have 500w+ panels, why not size a controller per panel? I have 200w and size a controller for each. This is a little extra cost, but completely avoids the issue of wiring, and adds significant redundancy to the system.

You could do that but everything is designed for large series arrays. I have my stern arch array performing at 130% of rated output in the summer, at 120V DC output. My new array (hurricane destroyed the old one) will be 200V.

[nelly]

Originally Posted by s/v Jedi

You could do that but everything is designed for large series arrays. I have my stern arch array performing at 130% of rated output in the summer, at 120V DC output. My new array (hurricane destroyed the old one) will be 200V.

Nice!! You have a much bigger setup than I do. All the panels on my boat will not get to 120v haha. I suppose I could have ordered higher voltage panels...

15amp charge controllers are pretty cheap (<$120) from reputable brands, but yeah, in your case I figure they will add up fast - and you probably do not want a ton of them on board. In my case, I get by with two!

[s/v Jedi]

Originally Posted by odonnellryan

Nice!! You have a much bigger setup than I do. All the panels on my boat will not get to 120v haha. I suppose I could have ordered higher voltage panels...

15amp charge controllers are pretty cheap (<$120) from reputable brands, but yeah, in your case I figure they will add up fast - and you probably do not want a ton of them on board. In my case, I get by with two!

These big panels are 72 cells, 50V. I had 5 of the smaller 375W panels and still have an array of two. They are 60 cells, 40V each.

I hope to find bifacial 440W panels for the new array on the arch and there will be 4 of them.

Do you know Beau and Brandy on YouTube? They have two big panels on their really small boat

[nelly]

Originally Posted by s/v Jedi

These big panels are 72 cells, 50V. I had 5 of the smaller 375W panels and still have an array of two. They are 60 cells, 40V each.

I hope to find bifacial 440W panels for the new array on the arch and there will be 4 of them.

Do you know Beau and Brandy on YouTube? They have two big panels on their really small boat

I do not know them, but interesting setup! Glad it is working for them.

Do you have the arch built?

[bdgWesternMass]

Originally Posted by s/v Jedi

No, the large panels put the others to shame, perform much better.

Shading problems occur when you put these in parallel. They must be put in series or a dedicated controller per panel.

These panels are actually multiple strings in series, so compare to multiple small panels. During partial shading, the diodes guide current around the shaded string.

Nice.

Doesn't help with the other issues. There maybe cases where a single giant panel is preferable hardly a one size fits all solution.

[s/v Jedi]

Originally Posted by odonnellryan

I do not know them, but interesting setup! Glad it is working for them.

Do you have the arch built?

We had the arch built in 2003/2004. Here is a picture with the old array on top:

[Rohan]

Originally Posted by s/v Jedi

When you have two large panels in parallel and one of them gets partial shading, triggering a bypass diode… then this partially shaded panel has a lower voltage and the other panel tries to dump charge into it. Even when that is blocked, the array will never perform because it has lost 50% output.

Again, I think you have that reversed. In parallel, why would one panel dump charge into another one? They are all feeding power independently. It's in series that the power is running across one panel to another.

In my own experience, I wired my panels in series, didn't like the results I was getting, and this forum recommended I switch to parallel. The results were dramatically better.