Which solar panels?

Doing a major refit trying to get our new to us NT42 up to Bristol. Currently has 2 house size solar panels mounted on the boat deck. The boat deck isn’t used as the boat came with a Freedom lift so space isn’t a problem other than needing a walkway to the flybridge. The panels work but are around 10 years old. Can’t find anything to identify brand on them. Associated wiring and accessories are in good shape and functional. The panels are coming up due to other work being done so if they’re going to be replaced it’s a good time to do it.

Is it worth replacing the panels?
If so with what brand?
Currently the panels are mounted a few inches off the deck. There’s green growth under them and access to clean that off is difficult. Is it worth eating the decrease in output going to semi flexible panels? Other choice is to mount them higher allowing storage space under for light things like fenders, SUPs, kayaks and such. Raising the weight isn’t a problem as even at 30-50lbs a panel weight is much less than a crane, dinghy and engine.

What would you do?

I wouldn't be too picky about brand. Out of any brand sold by a decent solar dealer, I'd pick based on price, availability, and size (some will be a few inches different than others, even in a similar power range).

When I installed my panels last year, I went with a pair of 410w panels from Trina Solar (TSM-410-DE15H(II)). They were only about $200 each and perform great. I debated spending a bit more to get a different brand's 440w panels, but they were a little wider, so I decided the reduced walkway to the windshields wasn't worth the few extra watts.

While I've never done solar panels, I'm of the mindset that you either seal something to the deck / mounting surface or you provide easy access to deal with the surface under the panels. I like the idea of storage underneath as that should give you complete access to seal a leak or whatever without removing the panel(s). If the panels get installed as the existing panels, I would want enough slack or routing in the power cables so that the panel can be moved without disconnecting the cables.

Ted

I would opt for raising it up a bit for storage and access underneath.

O C Diver said:

While I've never done solar panels, I'm of the mindset that you either seal something to the deck / mounting surface or you provide easy access to deal with the surface under the panels. I like the idea of storage underneath as that should give you complete access to seal a leak or whatever without removing the panel(s). If the panels get installed as the existing panels, I would want enough slack or routing in the power cables so that the panel can be moved without disconnecting the cables.

Ted

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I agree on the mounting logic. With solar, elevating the panels and providing a way to detach the mounts (for when you decide the deck under them really needs cleaning) is better. More airflow under the panels keeps them cooler and improves performance. I also agree on leaving some slack in the cables, but also make sure you can get to the MC4 connectors to unplug them if you need to move the panels entirely out of the way.

Mine have the mounts built in 2 pieces, so you can either unbolt the panels from the mounts or split the mounts in half to remove. And the frames are 2 inches off the deck, so it's easy to rinse under there without removing the panels.

So I’m hearing replace them?

Hippocampus said:

So I’m hearing replace them?

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I'd probably upgrade being that you're pulling them off anyway. You can almost certainly get more power output for a given amount of space with new panels and modern MPPT controllers.

So replace them. They’re standard size house panels.

Replace with which ones? Have a vote for Trina Solar (TSM-410-DE15H(II)). ?others to consider?

To be honest, I picked mine based on finding a couple of solar retailers that deal in individual quantities and going through their catalogs. Then I picked based on physical size, output, price, and a quick search to confirm the brand has a decent reputation.

It looks like the panels I got are not currently available, at least from the retailer I bought from. But there are a lot of panels out there in the 400w ballpark.

More importantly, measure the space you've got and figure out the maximum length and width of panel you can accommodate. That may narrow down your options a bit or point you to a slightly higher or lower output range based on what will fit.

I have looked at solar panels until my eyes are spinning. Unfortunately, my energy audit, cruising style, and location don't make a solar investment a slam dunk. One of the contenders would be flexible panels. If the mounting surface is smooth and if it is slightly curved and if occasional temporary removal was required and if 200W was sufficient, I would look into something like this kit.

I've had a 100W flexible panel mounted with Ykk Snads on the cabin top of another boat for several years. The dome-style plastic Snads are just a little dimple on the deck if the panel is removed, hardly noticeable even with bare feet.* I'm sure that there are testimonials on the net about the holding power of Snads. With 6 Snads on a 100W panel, you'll likely have other deck hardware blow/wash away long before the panel is an issue.

The flexible panels will have to be modified with appropriate receiving snaps attached. Not difficult. The center of the panel will need something like plastic furniture bumpers stuck underneath in a couple of places to keep an airspace for best panel performance.


*I don't allow bare feet on deck. Maybe I'm a Grinch, but I've seen too many foot injuries. Nothing ruins a cruise like a trip to the emergency room.

I am not sure the electric producing ability of a sq ft of panel has changed much in 10 years to make changing worthwhile.

There doesn't really seem to be a "standard" size, they vary an inch or two or more between manufacturers. That makes replacement more difficult depending on how they were mounted.

NO WAY would I go semi-flexible if it can be avoided. The semi flexible ones do not last very long, the manufacturers know this and that is why they will not warrantee them longer than a year or two. Rigid ones routinely last 10 - 20 years. I have 6 delaminated semi flexible ones I'll sell you cheap....

If you can keep some space under them, they will stay cooler, and temperature is a big factor in output.

Consider replacing them, or not…it’s your choice to make, one way or the other, depending on your budget. You could do a “test” to determine their possible voltage and amperage. Consider putting them on Craigslist, or Kijiji, rather than throwing them out. Someone else would be happy to have them, rather than having them end up in the landfill.

Mounting: I created brackets out of angle aluminum and glued them to the deck with 3M 4200. I was pleased with that. However the mistake I made was not providing sufficient clearance to clean under them. It’s a bit of a struggle to walk around them. Of course you want to maximize the output for the available space and it’s a trade off: maximizing panel size or safety to move around them.

Jim

Consider upgrading the mounts and use the same panels until you have a reason to change them. If you use rail-style mounts, there is some adaptability to accommodate different size panels within reason. I'll try to post a couple pics of what we did to make it more clear.


Another option is to put off this project until you've used the boat enough to have a clear picture of your power generation vs. usage and then change panels if necessary. It could be that just a change of fasteners on the existing mounts would make them easy to raise for cleaning underneath. I do agree that you should avoid mounting directly on the deck.

We went 2nd hand 250w panels made by a Tier 1 company
6 mth old and 9.5 years of warranty remaining
Available on sites like Gumtree (craigs list?), facebook marketplace for around $60 each

Hippo, check out this thread for one mounting method. I don't want to clutter up your thread with pics, etc. but the system might be worth a look for you:

https://www.trawlerforum.com/forums/s4/solar-panel-mounts-hard-top-61123.html#post1057638

I think I'd start by exploring different shaped panels to see how many more watts I could get out of the space. Unfortunately it's a tedious process since dimensions vary widely. If the current space is filled pretty well, my guess is that it won't be much of an improvement to swap panels, and that your efforts will be better spent of other projects.

Interesting article on solar efficiency. Several brands are mentioned at the end

https://www.cleanenergyreviews.info/blog/most-efficient-solar-panels

Surprised no one has mentioned looking at backside of panels to read the spec tag on the panel. The system was matched with a controller that needs to be taken into consideration. MPPT controllers have come a long way in 10 years, and the existing panels have likely lost at least 10% efficiency from new. I agree that replacing now makes sense - this is relatively inexpensive kit and easily replaced (except for revised mount)

Most house sized panels are in the range of 2m x 1m plus or minus a wee bit. Nominal 12v panels used on many boats and RVs vary widely.

Goof luck

Peter

So VHB tape is a no-no? Seems easiest way to do it and no breaching of the skin of the deck. Wouldn’t think there’s enough space underneath to allow growth but also not enough space for ventilation.
Thanks Guy for the link to the other thread. TT that seems a great mounting idea. Was think of using Al tubing to do something similar but also allow tilting to improve performance. Lots of places we go the tides are minimal and wind blows from the same direction. Have noted getting the right angle for season and locale makes a lot of difference in output. Possibly more than 19% v 22%.
We’re starting with a fresh unpunctured deck and lots of space so any mounting system is in play. Was thinking about a long angle held down with VHB tape. Then tubing on nuts and bolts ascending from that. Several at a diagonal to achieve rigidity. Given electrically isolated and level of loading (including wind) Al would serve while avoiding weight and maintenance of stainless. Panels on clamps with one side on rods allowing full tilt or partial to allow access and change in angle.

I wouldn't mount them with VHB tape. I'm not sure if it would give a good enough bond, especially on a non-skid deck.

Personally, I made C brackets from 2 pieces of aluminum angle each (bolted together) and then glued them to the deck with 4000UV (contact area is 6 sq inches per bracket). The panels bolt to the top of the bracket. Strongest winds they've seen are ~40 kts and there's been no sign of anything moving. Only hole in the deck is where the cables come through.


I posted the picture of the installed panels earlier in the thread, so here's one of just the mounts on the deck without the panels:

I think mounting feet with 3M4000 or 4200 as Jim Cave and rslifkin did is a good approach. In retrospect I probably should have done the same, but didn't want to leave anything to chance so tapped and bolted mine in addition. If the boat is ever in hurricane winds, I don't want them coming off.

twistedtree said:

I think mounting feet with 3M4000 or 4200 as Jim Cave and rslifkin did is a good approach. In retrospect I probably should have done the same, but didn't want to leave anything to chance so tapped and bolted mine in addition. If the boat is ever in hurricane winds, I don't want them coming off.

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Honestly, the only reason I didn't bolt mine down was lack of access. I would have had to open up the stapled vinyl headliner in the salon and that's easier said than done.

"NO WAY would I go semi-flexible if it can be avoided. The semi flexible ones do not last very long, the manufacturers know this and that is why they will not warrantee them longer than a year or two. Rigid ones routinely last 10 - 20 years. I have 6 delaminated semi flexible ones I'll sell you cheap...."

Just an FYI on warranty from at least one company for recently purchased flexible panels. My recently received Renogy 175 watt (RNG-175DB-H) flexibles came with a 95% 5yr, 90%-10yr and, 80%-25yr output warranty and 5 yr mat'ls & workmanship.

My Unisolar flexibles were doing fine at +10 years. I did manage to lose one in a wind storm (it wasn't secured). The other I gave away when I bought a new (less) flexible. One issue with the flexibles is the inability to easily mount them so that they can be adjusted to sun angle. Not too important if you're in the tropics. But this time of year at 50 degrees north (brrr) the sun only rises about 25 degrees at noon.

Have you measured and monitored the output from your existing panels? The delta between your current performance and that achievable with new panels might help you decide if replacement is the way to go.
This year I replaced 6 old Coleman panels (2 of 6 didn't even work) with four new Renogy panels within the same foot print and it was a game changer.

Has anyone actually measured the output degradation for a rigid panel after 10 years or so? Do they really degrade in practice? My home panels are pushing 15 years now and I can't say I've noticed any difference, but also note sure I would unless it was really significant. When it's cold and the batteries are low, they still crank out a ton of power on a good sunny day. I'm thinking that replacement simply because of unknown output degradation over 10 years is unlikely to be much bang for the buck. Now if you can switch to larger and/or more efficient panels and measurably increase the nameplate rating, that might be worthwhile. But I have a hard time getting excited about power loss due to age.

Wils said:

Have you measured and monitored the output from your existing panels? The delta between your current performance and that achievable with new panels might help you decide if replacement is the way to go.

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This would be great, but I think very hard to do outside of lab conditions.

Here's a credible source on the subject of output degradation over time


https://www.nrel.gov/state-local-tribal/blog/posts/stat-faqs-part2-lifetime-of-pv-panels.html


It seems unlikely that your panels have lost more than 5% of their output.

Good to know. Thanks for the link

I wouldn't be comfortable with just relying on adhesives to mount a metal bracket to the deck with all the flexing from the boat while underway and flexing from heat expansion and wind. I would add well nuts ( marine grade waterproof) if access under the deck is an issue. Having room to store larger flattish items inder the panels also sounds like a winner and allows for cleaning also. I would use the existing panels , I seriously doubt they have lost enough output to warrant replacement. Look for info on replacement of commercial solar in the desert, that's a very harsh environment for panels. Commercial users replace at intervals from a cost/benefit analysis.
I sure you can find a myriad of places to spend the money saved using the same panels on a new to you boat.
Hollywood