Biggest Solar Panels...

[s/v Jedi]

Originally Posted by Pete7

Well not the greatest photos, but what started out as a second hand rib frame to support 150w of solar. This had to be strengthened for the 3 x 300w panels we now have. Have to admit, I didn't envisage mounting 600w when we bought the rib frame 6 years ago.

The extra supports worked and the frame is much more rigid even with 34kgs of panels. I used 3/4" support bars rather than one inch to keep the weight and cost down.

Panels join to the tube frames with pipe clamps, though the clamps Sailing Harry linked to above would be nice. The pipe clamps came with mild steel parts which were replaced with S/S.

Not sure how much bigger we can go. 2 x 400w Hyundai shingledmight be possible. They will be close to the maximum width of the yacht and I need to take into account rafting alongside another yacht is common practise in Europe.

Pete

I don’t like a solar array almost at the width of the stern, because the aft end often overhangs and you risk hitting it against high pilings, sea walls etc. especially when maneuvering.

Have a look at the sliding designs. I am going back from 3 panels wide to only two (albeit a bit wider panels that we can comfortably fit when there’s only two) but two additional panels underneath that can slide out when at anchor or even sailing in light conditions, doubling power.

[Pete7]

Originally Posted by s/v Jedi

I don’t like a solar array almost at the width of the stern, because the aft end often overhangs and you risk hitting it against high pilings, sea walls etc. especially when maneuvering.

Have a look at the sliding designs. I am going back from 3 panels wide to only two (albeit a bit wider panels that we can comfortably fit when there’s only two) but two additional panels underneath that can slide out when at anchor or even sailing in light conditions, doubling power.

Yes, the width is my concern too, particularly as we do locks and harbour walls in addition to rafting. Oh and the back stay is offset 95mm to starboard at the stern so you can access the swim platform easier, so the panels have to be offset too.

The cassette idea is interesting, but a lot of work to go from were we are now to a cassette solution and its more weight higher up. Tricky on a 31ft yacht. Semi flexible panels hanging from the guard rails is another simpler and lighter option for us.

Pete

[s/v Jedi]

Originally Posted by Pete7

Yes, the width is my concern too, particularly as we do locks and harbour walls in addition to rafting. Oh and the back stay is offset 95mm to starboard at the stern so you can access the swim platform easier, so the panels have to be offset too.

The cassette idea is interesting, but a lot of work to go from were we are now to a cassette solution and its more weight higher up. Tricky on a 31ft yacht. Semi flexible panels hanging from the guard rails is another simpler and lighter option for us.

Pete

The cassettes are actually very little work to build (two extruded angle profiles, a set of sliders and a set of fillers of the same width as the sliders for the upper fixed panel. Of course the weight more than doubles, but you could easily double your capacity that way.

[rslifkin]

Originally Posted by Pete7

Yes, the width is my concern too, particularly as we do locks and harbour walls in addition to rafting. Oh and the back stay is offset 95mm to starboard at the stern so you can access the swim platform easier, so the panels have to be offset too.

The cassette idea is interesting, but a lot of work to go from were we are now to a cassette solution and its more weight higher up. Tricky on a 31ft yacht. Semi flexible panels hanging from the guard rails is another simpler and lighter option for us.

Pete

Based on what you've got now, could you extend forward and make a bimini of sorts out of panels? As long as you can keep them under the boom, it looks like you should have space.

[Rohan]

Originally Posted by sailingharry

I have individual amp meters on each of my charging sources. As a result, I could see how little my wind (D400) was making and how much it was costing my solar. I no longer have my wind generator! It is very difficult to mount a wind generator such that it does not shadow your solar, and in winds less than 15 knots, it makes very little electricity.

Wind generators produce much less than solar - during the day. But unlike solar they can run 24 hours. On a typical day with solar I probably get 8 useful hours only.

But yes, it's better on larger boats because on smaller ones there's usually no good place to put it. It will either interfere with the solar panels or with the sails.

[Grith]

I note in comments here statements that the very large panels are more efficient than smaller panels. Has someone got an explanation for that? I understand they may be more cost efficient and don’t have some minor extra edge losses but why otherwise so much more efficient?
I found having multiple smaller 180w panels (5of) was much easier to mount in my small 28 foot yacht application and allows their relatively easy removal and to stow below if projected extreme conditions dictated this precaution.
It also allows changing series and parallel configurations very easily to cope with partial shading issues and also tilting of 2 of the panels to follow the sun at anchor.
I would have thought dealing with and mounting very large single panels relatively difficult on anything but fairly large yachts and catamarans.
I like the fact I can unload the weight and windage of my Bimini and targa bar panels relatively easily in adverse conditions due to their smaller manageable size.
PS I have Canadian solar panels fitted on my homes roof and the installer miscalculated the number that would fit leaving me with two spare 370w panels. Even these were too unwieldy to fit to my yacht and I installed them on my green house roof were they power charging my EcoFlow powerbank which powers my house rainwater pump and river water reticulation pump as well.
These panels were just too large to efficiently mount on my yacht despite already owning them and not previously having a use.

[noelex 77]

In general the best solar energy energy extraction on a sailboat, in descending order of efficiency, is achieved connecting the panels:

One panel per controller.
Parallel connection.
Series connection.

[rslifkin]

Originally Posted by Grith

I note in comments here statements that the very large panels are more efficient than smaller panels. Has someone got an explanation for that? I understand they may be more cost efficient and don’t have some minor extra edge losses but why otherwise so much more efficient?

I think it's because there's a bigger market for the large panels used on houses, they get more R&D put into them. So the advantages aren't necessarily due to the size of the panels, but due to market demands prioritizing the big panels.

[s/v Jedi]

Originally Posted by noelex 77

In general the best solar energy energy extraction on a sailboat, in descending order of efficiency, is achieved connecting the panels:

One panel per controller.
Parallel connection.
Series connection.

Not at all in my experience. Series connection to a MPPT controller is by far the best option for arrays that don’t get bad shading, like the one we have on the stern arch.

If you have shading issues then a dedicated MPPT controller per panel is better, because the panels get different Maximum Power Points and thus each controller can get it exactly right for that panel and at the voltage it outputs.
Here it is extra important to get the big panels so that you get the high voltage.

The parallel connection is the worst option. You stack current so multiply resistance losses, you don’t get more voltage so no extended period of production and when a panel gets partially shaded you loose output of that complete panel instead of just part of it. Still, there are valid reasons when you must connect in parallel:

1 - when you have a PWM type controller instead of MPPT.
2 - when you have extreme old panels that lack bypass diodes (unlikely) or the diodes in your panels are missing or blown up.

Of course #2 can be fixed with new diodes.

About the statement that for a series string, with partial shading on one panel, the whole string is affected. That sounds bad but is absolutely fine and much better than the parallel connection. Here is what really happens:

Let’s say we have three panels of 45V, 8A in series. This means the array becomes 135V 8A = 1,080W. Each panel has three strings, three diodes. So each string is 45 / 3 = 15V

Now let’s say shading hits one string of one panel. The bypass diode of that string in that panel starts conducting. We lose the 15V voltage of that string, plus we have a 0,6V voltage drop over the diode that is a loss. The array becomes 119.4V (135 - 15 - 0.6) and 8A so we have 955.2W left.

Yes, the whole array is affected because voltage is lowered by 15V and the current from the unshaded part is affected by the bypass diode, which is wasting 8 x 0.6V = 4.8W of power as heat.

But is that bad? Let’s compare with the same panels connected in parallel. Let’s also assume there are no wiring losses and no reduced daily period. So we now have an array that is 45V 24A equals 1,080W. We get the shaded string so one panel reduces it’s output voltage to only 30V and can’t output current to the 45V input terminals at the controller. We are simply left with a 45V 16A array which equals 720W.

So shading in parallel doesn’t alter the array voltage but it does alter the amperage. In series you loose only the shaded string(s) which may not be the whole panel. You do get the additional loss of the diode but this is less than 5W.

In real life you don’t have this shading all the time. But no matter how you spin it, the series connection still outperforms even before considering other losses like in wiring or reduced period of production.

[Grith]

Hi s/v Jedi Thanks for your continued informative posts. I would like to ask a question about parallel verses series versus taking a panel out of series if permanently shaded whilst the yacht is in trailering mode.
Whilst my mast is down when the yacht is in trailering mode my central over Bimini panel of three has the mast sitting close on top of it. Previous photo in this thread.
I have taken to removing this panel from 4 180w panels connected in series as I feel this heavy shading degrades the output of all 4 panels.
Unshaded they can produce close to their rated 720w combined output on a regular basis on full sun days.
Whilst they are often showing 80-90v unshaded in full sun the strong shading of the mast when down on the central panel pretty much destroys the outputs of all of them producing fairly pitiful results.
Removing that central panel from the string actually improved the output by 30-50 percent. The central rear targa panel is under the top of the mast and is also effected but tilted down in winter here to a much lesser degree.
I have the capability to split the feed back into my yachts controllers into two with existing cabling and actually have three mppt controllers and three separate battery banks in my yacht. (too long to explain!)
Your thoughts and suggestions and those of other skilled readers would be appreciated.

[s/v Jedi]

Originally Posted by Grith

Hi s/v Jedi Thanks for your continued informative posts. I would like to ask a question about parallel verses series versus taking a panel out of series if permanently shaded whilst the yacht is in trailering mode.
Whilst my mast is down when the yacht is in trailering mode my central over Bimini panel of three has the mast sitting close on top of it. Previous photo in this thread.
I have taken to removing this panel from 4 180w panels connected in series as I feel this heavy shading degrades the output of all 4 panels.
Unshaded they can produce close to their rated 720w combined output on a regular basis on full sun days.
Whilst they are often showing 80-90v unshaded in full sun the strong shading of the mast when down on the central panel pretty much destroys the outputs of all of them producing fairly pitiful results.
Removing that central panel from the string actually improved the output by 30-50 percent. The central rear targa panel is under the top of the mast and is also effected but tilted down in winter here to a much lesser degree.
I have the capability to split the feed back into my yachts controllers into two with existing cabling and actually have three mppt controllers and three separate battery banks in my yacht. (too long to explain!)
Your thoughts and suggestions and those of other skilled readers would be appreciated.

When the mast shades the complete panel, and the panel has 3 bypass diodes, then you have three times the diode losses, but that doesn’t explain a 50% improvement when you take the panel out of the array.

So something is going on. The best cause of action is to test this. You can buy a specialized tester but I will describe how to do this with a multimeter.

Disconnect all panels. Now measure output voltage of each. The unshaded panels should have the Voc as per spec sheet. This means Voltage Open Circuit.

The shaded panel should have less or no voltage.

Now use the amperage setting of the meter. You must have a 10A terminal that you must move the red probe to. Make sure the panel Isc is less than what the meter can do. Now connect the probes to the panel leads, positive to positive and negative to negative. There can be a small spark because you are shorting the panel output. Note the amperages. In full sun they should approach Isc (means short circuit).

Now start connecting in series, with two panels, one shaded and one unshaded. Note that you get dangerous voltages, don’t do this if you’re not sure.

Measure Voc and Isc for the two again. You should get a lower Voc but the same Isc. If not, then the shaded panel has an issue with a diode. You can test that but need to know where the diodes are. Try to Google this.

Also, alternatively, you can add an extra bypass diode over the whole panel that gets shaded. This doesn’t solve the issue the panel has, but it fixes your problem with the mast and even better because you only have the loss of one diode. Simply connect it like in the diagram I attached above except not for just 4 cells but you whole panel.

So the side of the diode that has the band goes to the panel positive and the other side to the panel negative. The diode blocks the circuit so you don’t get a short, but once the other panels are connected in series it will divert the current around the shaded panel like in the diagram.

Remember that normally these bypass diodes only deal with a string of cells and the panel has three diodes. Now you deal with the whole panel so the reverse voltage rating of the diode must be higher than the panel Voc. Here is an option for panels with Voc lower than 45V: https://www.amazon.com/20-Pieces-15S.../dp/B079KK5KXN

[CaptainRivet]

Originally Posted by noelex 77

In general the best solar energy energy extraction on a sailboat, in descending order of efficiency, is achieved connecting the panels:

One panel per controller.
Parallel connection.
Series connection.

Would add one more:
High quality panel: a 500W renogy is much worse then 500W LG or longli...starting from top end power but more important is low light performance and shading performance.
Fully agree with bifacial panels one panel per controller is even more efficient. Regarding shading the bifacials are a gamechanger working with Diffusion light.

[michaeld]

Here is what works for us: three 175W panels in parallel. We get about 20A on a clear day.

[Seafarer7]

Originally Posted by s/v Jedi

But is that bad? Let’s compare with the same panels connected in parallel. Let’s also assume there are no wiring losses and no reduced daily period. So we now have an array that is 45V 24A equals 1,080W. We get the shaded string so one panel reduces it’s output voltage to only 30V and can’t output current to the 45V input terminals at the controller. We are simply left with a 45V 16A array which equals 720W.

S/V Jedi: interesting analysis and food for thought here (re: series being better than parallel). But doesn’t the quoted scenario above ignore the fact that the parallel panels are connected to an MPPT controller that constantly sweeps the voltage range searching for the sweet spot? ie: I would assume immediately after the shading event above the MPPT controller would drop from 45v to somewhere nearer to 30v if the total power output at 30v exceeds that at 45v. So even though the two unshaded panels wouldn’t be operating at their peak MPPT output at 30v, still the total output at the new 30v point would still be much more than 720w?

That is to say: after the shading event above, with a new 30v tracking point output: all three panels would be contributing power, with two unshaded panels operating somewhat below their rated maximum power (below 720w), and the shaded panel outputting 2/3rd of it power(~240w). Sum total of the three should be much better than the total removal of one panel that would occur if the MPPT controller continued to pin its intake voltage at 45v

[s/v Jedi]

Originally Posted by michaeld

Here is what works for us: three 175W panels in parallel. We get about 20A on a clear day.Attachment 277278

This immediately shows a different setup with panels angled differently. For optimal performance, the two panels that are aligned the same can be in series connected to one MPPT controller and the third panel aligned and pointed differently gets it’s own dedicated MPPT controller.