Solar advice: one big panel or 2 smaller panels?

[Copacabana]

I'm about to haul the boat for some painting and TLC. One of the projects is to upgrade my solar array. I currently have two 45w Siemens panels hooked up to an Outback 10a PWN controller. Output is not very impressive... I have a pretty low power demand on board (all LED, manual everything and an Engel fridge and normal electronics use). I figure I need to replace between 25ah and 50ah a day, depending on the fridge setting and use of gadgets.
My plan is to upgrade to either one big Canadian Solar 265w/30v panel or two 140w/18v panels. I will hook the panel(s) up to a 20a MPPT controller. The panel(s) will be mounted over the bimini. I have two backstays that pass on either side of the bimini which will probably cast a shadow on the panel(s) for part of the time during the day. The boom does not go over the bimini, so the shading will be just a backstay sometimes. My question is: would I be better off with the 265w/30 volt panel? I was thinking that the higher voltage output would deal better with partial shading as the MPPT controller will always have enough high voltage to transform into amps at 13.8v-14.4v. I'm leaning towards the one big panel for simplicity. Advice or comments? Thanks in advance.

[a64pilot]

I think power production wise, your better off with separate panels, plus they are slightly higher wattage anyway.
How much better? I don't know, but suspect it won't be all that much, depends on how much margin you will have. By that I mean if you can only just barely get by, then any shading will kill you, but if you make more than you need, what's a little loss due to shading, you still have enough.

[Cotemar]

My Vote would be for 1 large SunPower panel. Shading will not bother these panels.

Lightest, smallest most powerful panel with the most output at 21%

[Copacabana]

Originally Posted by Cotemar

My Vote would be for 1 large SunPower panel. Shading will not bother these panels.

Lightest, smallest most powerful panel with the most output at 21%

I'd love to use Sunpower, but I have to go with what's available here.
Anyone know if Canadian Solar are better than Yingli? Same price here...

[Copacabana]

Originally Posted by a64pilot

I think power production wise, your better off with separate panels, plus they are slightly higher wattage anyway.
How much better? I don't know, but suspect it won't be all that much, depends on how much margin you will have. By that I mean if you can only just barely get by, then any shading will kill you, but if you make more than you need, what's a little loss due to shading, you still have enough.

A64, I'm hoping either setup will provide more than enough power for my needs. I almost never use more than 50ah a day (and then very rarely).

[rom]

Originally Posted by Copacabana

I'd love to use Sunpower, but I have to go with what's available here.
Anyone know if Canadian Solar are better than Yingli? Same price here...

If you can't buy the sunpower there maybe you can buy the BenQ ? It is basically the same panel.

[Copacabana]

I'm not too worried about the efficiency of the panels as I have plenty of room for panels and low power needs.

[john61ct]

Originally Posted by Cotemar

large SunPower panel. Shading will not bother these panels.

I've never heard of such a thing, please explain, and ideally link to vendor docs.

[Paul L]

I prefer 2 smaller panels. If you ever have to prep for a hurricane, it is a lot easier to put smaller panels below.

[skipgundlach]

Originally Posted by Cotemar

My Vote would be for 1 large SunPower panel. Shading will not bother these panels.

Lightest, smallest most powerful panel with the most output at 21%

Originally Posted by john61ct

I've never heard of such a thing, please explain, and ideally link to vendor docs.

Well...

I'm not a rep nor anything other than an about-to-be new customer...

But...

Most modern panels have diodes which will split the input stream. Shading a cell only affects a portion of the entire panel; perhaps that's what Cotemar meant.

But...

Sunpower rigidly controls their distribution; I was fortunate to be allowed inside that chain, and the local outfit will be here tomorrow - assuming the replacement panels for what actually was shipped the first time actually arrive today - to do the installation.

Having a factory installation will preserve the warranty, albeit only 12 years on a moving platform (they do RVs as well).

However, the current residential frames have no mounting holes; the Gen3 frames, still used in the commercial versions (which is what is replacing those originally sent) do have those, and ground-strap holes.

The residential panels are intended only for mounting to a (non-moving, non-distorting - as would likely be the case aboard) frame with clips.

Here's what I'm getting: two fit in essentially the same real estate as my previous 3 making 370w when they were new:
https://us.sunpower.com/sites/sunpow...lar-panels.pdf
Note the frame in this one - no holes...

The commercial version is:
https://us.sunpower.com/sites/sunpow...lar-panels.pdf
The mounting holes are shown but not sited (no dimensions)...

This shows, pp 5-6, the mounting holes:
https://us.sunpower.com/sites/sunpow...n-guide-na.pdf

I'd post my various documents, but it's easier to just go to Sunpower's site, and look at the various items they have available.

I chose Sunpower for the efficiency; if real estate is not an issue, the lower efficiency panels will give you a lot cheaper watts, at the cost of a great deal more space needed (the efficiency ratings are solely a matter of how much sunlight per given area - a square meter I think is the industry standard - is converted into electricity; thus, Sunpower's typical more-than-21% efficiency will produce the same wattage per rating [say, 100w] in a much smaller footprint than a 15% efficient panel).

Once my installation is complete, I'll be doing a report, as well as providing referrals for both east and west coast folks; I've been at this (starting and ending dates, with a great deal of idle time in the middle) for 16 months...

L8R

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[a64pilot]

I have four Canadian Solar panels that seem to work well, but as I have no other experience with Solar panels, my opinion doesn't mean much. They seem well made if that helps.
I got them for .50c a watt I think it was, they were left overs from a large residential install.

[newhaul]

I would have to recomend the two panel install. Marginal increase in watt output . Most importantly redundancy if one panel stuffs it you will at least havee one panel providing some power . Next it will help mitigate shading issues. Lastly they are smaller and easier to handle for maintance and removal for storm prep if needed.
( yes there is some maintance on solar panels they must be cleaned and at least once a year apply a.good wax )

[buzzstar]

Originally Posted by newhaul

Most importantly redundancy if one panel stuffs it you will at least have one panel providing some power .

Does anyone disagree with redundancy? If so, why? [Please keep it separate from other related issues, thanks.] I, personally, think of it as a primary consideration since it is an option, but then when I did such things, I wore both a belt and suspenders (really!).

[a64pilot]

Price of two panels vs one?

You wax glass panels?
Why? would rain-x be better?

[skipgundlach]

Originally Posted by a64pilot

Price of two panels vs one?

You wax glass panels?
Why? would rain-x be better?

RainX is really only good on weathered or abraded stuff as windshields get over time. A new windshield will behave about as well as one which has been treated with RainX.

It's the same theory on how PoliGlow looks so good - it fills all the tiny scratches.

So, barring a particularly harsh environment, you won't have that wear on the glass - but wax might help keep it cleaner. And in fact, most manufacturers suggest washing them on some regular basis as well as having some tilt to allow rain to self-wash to a degree...

L8R

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