Solar Panels - horizontal or angled?

[joelhemington]

Originally Posted by Wotname

Which of the two solar panel arrangements in likely to be more effective in general.???

Both have the same area (3 sq m). Arrangement 'A' is completely horizontal (at rest) where as arrangement 'B' has 1.5 sq m horizontal and two 'wings' each 0.75 sq m) angled (fixed) say 45 degrees (or maybe 30 degrees) from horizontal.

Assuming a mono hull, aligned fore and aft as shown, no shading from rig etc, used both underway and anchored, used at any latitude from 0 to say 45 and each panel has its own MPPT charge controller.

The ability to angle the panels to directly face the sun will provide your maximum results. Mantus Marine makes a great product for this https://www.mantusmarine.com/mantus-rail-clamp/ The only downside is somebody will need to adjust the panels during the day. If not, it's better to just leave them mounted flat.

[Wander4Wonder]

Originally Posted by Off Trail

There is also large seasonal and latitudinal (?) variation in sun angle, so a lot depends on where you are. If you size the array and loads for year-round use, you will have lots of excess capacity in the height of summer, so small differences like this really won't matter at all.

For example, we have rail mounted tiltable panels and a bimini array. In winter, just one of the rail panels (depending on wind direction) will provide nearly all our energy while the bimini panels barely contribute because of the low sun.

If this is your case, you might want to think about making the two wings pivot. I made ours to only provide 0, 45, and 90 degrees which was a pretty simple proposition.

Dan

Here is a us based estimate of average sun hours by location. Obviously closer to the tropics the sun will beat down for more hours at a higher more even angle depending on the time of year.

Solar Insolation - Sun Hours Per Day

If i were to install an arch my ideal would be rigid or semi-rigid panels arranged on a slight curve with the ability to fold the outer panels up against the curve as needed but thats another moving and breakable part and no amount of fidgeting will yield 100% efficiency so while you cant ignore the effects of angle, time of year/day, and latitude you cant go ocd and dwell on every little aspect 100% of the time.

[AedanC]

I was shown this in a presentation really and I don't know it's provenance, it might provide some interesting discussion here. It's for Ireland (53 degrees North) and it seems to me to suggest that if you can't track the sun then you are better mounting panels horizontally.

[Wander4Wonder]

excuse the fingerpaint artwork...having looked at a lot of boats I am always struck by how aftermarket and codgy a lot of solar panels look. I get function over form and I get by default they may be a necessary evil in our power hungry, eco-responsible world but I've always seen like they look like some sort of waterworld refuse tubing and welding jobs. The ones that have struck me are the ones that balance the flow and hydro/aero dynamic lines of the boat, the function of providing power and shade and a platform for longterm cruising accessories and often a davit for tenders. The ones I've seen that are nicest (excluding cost considerations) are the ones that have a swept back view, are high enough to have some clearance when walking from the passerelle and the swim platform without adding some god awful windage inducing top heavy scaffolding yet take the details into consideration.

something like this:


with a slight indention from perpendicular to the deck (after a bit) or curve to a curved top with panels situated as best configured with a inner light tube for a handhold or a platorm to lash softgear if needed. The solar panels would sit lengthwise horizontal on these but I guess you could put temporary ones on the side too to increase power if needed those would be more horizontal

(the gear caddies shown were just a design idea I thought to myself, I don't know if they would be a trashy or windage inducing nightmare) but in the interests of useful ness could be used for hanging a hammock or something.

[explorer 3]

My preference would be B.
You will have a longer charging time overall. Starting earlier and ending later.
When the sun is overhead mid day, both arrangements should fully charge your battery banks.

[CassidyNZ]

So if I fit panels on brackets, I am able adjust them to face the sun. I do this in the morning. Two hours later the tide goes from ebb to flow so the boat flips around. I readjust the panels. Then there’s a wind shift and the boat flips around. So I adjust the panels. Then the sun passes overhead so I adjust the panels. The the tide changes back so I adjust the panels. Then the sea breeze fills in . . . . This goes on all day.

Seriously, I didn’t get into sailing to be a slave to my solar array.

My panels are all mounted flat and I have enough of them to recover all of my electrical expenditure and then some on most days. On days that I can’t (cloudy, raining, etc.) tilting them will make no difference anyway and the balance between production and consumption will be taken care of tomorrow.

That’s why I have batteries. YMMV. My sole on-going commitment to solar performance is once in a while checking that the panels are clean and cleaning them if required.

[Ramona]

A lot will depend on whether you are using them on a sailing boat or just a boat that sits around at anchor or a mooring. Mono hulls tend to heel when sailing!
On my previous yacht I used two panels fixed vertically. One each side of the pushpit. I had originally intended to tilt them to the horizontal position at the mooring but found there was not much gain. On my present yacht there are two panels. Both horizontal, one on the cabin top and the other across the top of the pushpit where it is below the blade for the Aries windvane. I just use my yacht for sailing so the panels are at the ideal angle only occasionally!
The biggest enemy of solar panels is heat. Dark blue or black panels will soon get up to a temperature that causes losses. What the actual figures are these days I don't know. It used to be 27 degrees C. Panels are so cheap now you can mount them as wind breaks vertical alongside the cockpit or as in my case one is now the cover for the sliding hatch.

[kryg]

I would not have a flat solar panel layout as when it rains the water run off is poor . I have mine like a 7 to10 degree tent. Each of my two panels in my case is 360 watts. It gives excellent power and good shade cover under the helm. also when it rains. Another thing to keep in mind is unlike a house the boat and sun move around depending on the wind I would not do your drawing B. as you will lose 1/3 of solar panel benefit. See attached. Good luck with your project I found it is very important to get it right, both in wattage power, (PS double what you think you need) and installation.



Skoiern IV Kryg.

Originally Posted by Wotname

Which of the two solar panel arrangements in likely to be more effective in general.???

Both have the same area (3 sq m). Arrangement 'A' is completely horizontal (at rest) where as arrangement 'B' has 1.5 sq m horizontal and two 'wings' each 0.75 sq m) angled (fixed) say 45 degrees (or maybe 30 degrees) from horizontal.

Assuming a mono hull, aligned fore and aft as shown, no shading from rig etc, used both underway and anchored, used at any latitude from 0 to say 45 and each panel has its own MPPT charge controller.

[dkenny64]

it would seem there some information missing..
what % output do you need from the panels.

do you need 90% every day.. I would think you'll be need a complicated pointing setup
but what if you need 50%.. or 25%...

I put 800 watt of solar. mounted in style A. some is shaded by the boom..so of 8 panels I might have 6 in full sun.. in Dec in NC on an overcast day it still produced enough power to run all DC equipment..I don't have an inverter for AC..
-dkenny64

[Wander4Wonder]

Here is one that is angled a bit and hinged allowing adjustment of the outer panels



https://www.nauticexpo.com/cat/deck-...ls-UA-565.html

[Wotname]

Thank you all! The consensus appears to be KISS.

From several posts, I take note of providing enough slope for rain run off. From what I recall from roof and storm water plumbing (and roman history), the minimum slope for water to run off most surfaces is 3 degrees.

[Mike OReilly]

Originally Posted by Wotname

Thank you all! The consensus appears to be KISS.

From several posts, I take note of providing enough slope for rain run off. From what I recall from roof and storm water plumbing (and roman history), the minimum slope for water to run off most surfaces is 3 degrees.

Although I didn't mention it, my horizontal panels (3/4 of my wattage) are designed with a slight slope for rain run off. In my case I have plans to incorporate this into my rain collection system. I have yet to do this, but the panels drain pretty efficiently.

[CassidyNZ]

Just curious - how much rain can a totally flat panel with a 2mm lip around it, accumulate? And let’s be fair, water will only gather if the boat is motionless. Even the slightest roll on the boat would spill most of it.

Two panels on my radar arch tip slightly back but that’s just to stop them dripping on the deck above my bunk. The two on the roof are completely flat and I’ve not noticed any meaningful collection of water.

When the sun comes out, the panels warm up, the water evaporates and the panels are dry in no time. At night, who cares?

[Mike OReilly]

Originally Posted by CassidyNZ

Just curious - how much rain can a totally flat panel with a 2mm lip around it, accumulate? And let’s be fair, water will only gather if the boat is motionless. Even the slightest roll on the boat would spill most of it.

Yeah... I really don't think it's an issue on a boat, no matter what the angle. I built a slight angle into my panels so I could use them to collect rainwater, not because I thought it was needed.

[Wotname]

Originally Posted by CassidyNZ

Just curious - how much rain can a totally flat panel with a 2mm lip around it, accumulate? And let’s be fair, water will only gather if the boat is motionless. Even the slightest roll on the boat would spill most of it.

Two panels on my radar arch tip slightly back but that’s just to stop them dripping on the deck above my bunk. The two on the roof are completely flat and I’ve not noticed any meaningful collection of water.

When the sun comes out, the panels warm up, the water evaporates and the panels are dry in no time. At night, who cares?

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

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.