Solar Panels - horizontal or angled?

[akopac]

This has worked well for us. Mostly on the pacific side of the America’s. The davits are held in place horizontally by friction, but have a preventer line under way to keep them from swinging too far aft underway in case of a rogue wave or something. Like I said I don’t extend them underway except in mild conditions. That said panels are cheap (maybe hard to source some places if one broke). I made them bolt-on so the whole davit assembly could be removed for maintenance, or if I sold the boat and wanted to transfer them to another one. I made my own panel mounts from delrin rather than buy them and used some bolts myself. Even if somebody had a wrench it would probably be metric out of the states and at least they are not plastic wing nuts like the store bought ones. Durable and more or less theft inconvenient.

The friction cord angle adjustment has worked flawless for years and can be adjust far enough to face the panels upside down and forward. Be careful what kind of plastics you use as I have gotten some in MX called nilacera and it didn’t do well in the tropical sun.

Most of the time the boat faces North so all the panels are facing aft, but slightly out and angled about 45 or less. If I’m not lazy I’ll adjust them a couple times a day.

[flightlead404]

HelioWatcher | Automatic Sun-Tracking Solar Panel and Data Analytics

[CassidyNZ]

Originally Posted by Wotname

Well, the first question is straightforward - 2 litres per square metre of panel.

Yes, straightforward while the boat is motionless which in my case is very infrequently. The next question then is how much will 2mm of clean water affect the ability of a panel to produce energy?

Originally Posted by Wotname

Have you noticed any difference in dirt or salt built up between the sloped panels and the flat panels? I am speculating if some slight natural water flow aids in self cleaning.

I’ve not noticed any difference between sloped and flat but must say that I’m constantly surprised by how little cleaning our array needs. They seem to stay clean most of the time. Perhaps that’s a product of less airborne dirt where we live. My panels get a quick wipe maybe once every three to four weeks, less in summer when it doesn’t rain much. I can live with that.

And if “flowing” water had the ability to keep things clean, why do I need to wash my car after each rainy period?

[akopac]

I noticed in Northern Mexico I had to clean the deck and panels, but Southern Mexico and South it was more tropical and didn’t need to was then as much. Even off shore the desert dust carried.

[Wotname]

Originally Posted by CassidyNZ

Yes, straightforward while the boat is motionless which in my case is very infrequently. The next question then is how much will 2mm of clean water affect the ability of a panel to produce energy?
........

Dunno - speculative guess - some loss due to reflection and some gain due to cooling...

[Wotname]

Originally Posted by CassidyNZ

.............

And if “flowing” water had the ability to keep things clean, why do I need to wash my car after each rainy period?

Dunno - my car stays clean because I leave it out in the rain but perhaps cleanliness is in the eye of the beholder. YMMV .

[sailorboy1]

I have been able to see any performance lost on my flat mounted panels from dirt, dust, or evaporated water etc.

But i did clean them around a year ago.

I don't know how someone worried about such things would not just go insane on a boat.

[noelex 77]

Originally Posted by sailorboy1

But i did clean them around a year ago.

You must have very well trained birds in your region .

[sailorboy1]

Originally Posted by noelex 77

You must have very well trained birds in your region .

I have found birds only seem to like my boat if there are crappier ones around. Plus I have a theory that my panels are clean if i don't look.

[Mike OReilly]

I clean my horizontal panels on occasion. Bird poop, when it happens (not too often for me), dust, or salt after a rough passage. Most of the time a good rain keeps the panels clean, but a wipe down is sometimes warranted.

I've never tried to measure the effect of the dirt on solar input. It isn't pronounced, otherwise I would notice. But as with everything, local conditions vary and some places will be worse than others.

[LoudMusic]

I have no empirical evidence as to what is best, however ...

I think it is best to have them all in the same plane, near horizontal, with a slight tilt to allow for drainage. Due to the boat's nature of random orientation, having any significant tilt is surely to be in the wrong direction. Completely flat holds water (as is my dilemma). Manually adjusting requires additional hardware, frustration, and potential failure.

[Wotname]

Originally Posted by LoudMusic

I have no empirical evidence as to what is best, however ...

I think it is best to have them all in the same plane, near horizontal, with a slight tilt to allow for drainage. Due to the boat's nature of random orientation, having any significant tilt is surely to be in the wrong direction. Completely flat holds water (as is my dilemma). Manually adjusting requires additional hardware, frustration, and potential failure.

This sums up the collective thoughts in the past three pages and settles the question for me.

[AmzngGrace]

Speaking from the small contingent of sailors who just dont have alot going on on the boat that needs solar. I think its at least worthy to evaluate how much of the stuff on your boat you really need. The less you have, the less $, upkeep, headache and solar you need...
As an example, I know a guy who just has two shoebox sized panels in his windows on the sides of his boat. This seems to top off his batteries just fine. Granted he has really nothing else on the boat. This seems very relaxing to me IMHO.

[Mauruuru]

I can tell you as a former solar developer that in a sailboat application its not going to make enough of a difference to be trying to get an optimal angle. In a fixed roff or ground mount the optimal tilt angle would be based upon the lattitude.....the higher the lattitude the higher the angle. But if you don't have the capability to follow the sun you're going to loose on average 20-25% of the available energy. To get max output you need to both track and change the angle during the day an two axis tracking has never proven to be cost effective. On a boat even more so because of things like heeling angle, mast/boom shadowing etc......my advice don't overthink it. Solar has gotten so cheap, install a larger panel flat and be done.

[jalmberg]

We have adjustable panels, but after 4 years of experience, we have a rule that they be left flat. So many times we have tilted the panels towards the sun in the morning, only to have the tide reverse leaving them pointed in the wrong direction. Or we forget to flatten them out, so we lose the best of the mid-day sun. You might think you will adjust the panels 5 or 6 times a day to maximize power, but believe me, that’s not going to happen. Leaving them flat gets you 80% of available power. That’s the best human nature will allow.