Bifacial Solar Panels for yachts

[coopec43]

Originally Posted by GordMay

INDEED! My apologies.

The article, I linked, was discussing MONOfacial solar panels, installed on land.
Merely, an interesting aside, to the conventional [land based] "Latitude ± 15°” advice - not applicable to BIfacial panels, on boats.

No problem at all there (I think I understand the principles of Monofacial Vs bifacial)

Actually just this minute I came across this article which hopefully will sort out my confusion. If we mount the bifacial solar panel facing the sun we'd get direct solar rays hitting the panel front and we'd get reflected rays hitting the rear panel. I don't know how it works if you mount it "portraitly"

Maybe this artlcle will explain it?

Solar Panels: Overcoming Sunlight Issues

https://sustainablereview.com/solar-...nlight-issues/

[s/v Jedi]

Originally Posted by Wandering1

If you are going to pole mount panels, you must be thinking of really small panels? Pole mounts would have to by massive to support a large panel. Why not just mount on the guardrails? This is how we mount 720w of solar on our ketch.
We add an additional 200w of roving panel at anchor. The guardrail mounted panels can be tilted to point at the sun when sailing.
We regularly exceed the manufacturer’s rated peak output for our cheap 180w panels, not bifacial, by up to 15%. Next year, we will likely swap them for some new bifacial panels mounted in the same way, simply because these are getting old. I am not convinced by the hype of bifacial and reading some scholarly articles about performance, it would appear that a gain of about 4-6% is realistic. If I can buy bifacial for the same price then its still worth it

Saoirse (Beau & Brandy, YouTube) have two 350W panels mounted on two poles on their Pierson 35.

[Pete7]

Originally Posted by coopec43

Gord
I am so utterly confused.So far I've found they work well over water as water reflects the sun's rays well on to the back of the bifacial solar panel.

Sorry, but not completely true. Water absorbs sunlight rather than reflect, but you know that because the sea warms up during the summer (northern hemisphere). So you might get 5% reflection from the sea. Snow or white GRP on the other hand does a wonderful job of reflecting sunlight so you might see 15-25% reflection. LG had a brilliant website explaining the albedo effect. Unfortunately the Chinese effectively put them out of the solar business because their panels were made it Taiwan so not sure its still available.

On an arch like Jedi's bi-facials are worth doing because he probably has a 3m gap to the waterline so lots of space to collect reflected sunlight. Questionable on the roof of a house, certainly if it has dark Welsh slate or red concrete tiles.

Interesting program on the TV the other night showing farmers mounting panels vertically as a fence so bi-facial panels can absorb from both sides regardless of what the sun is doing. Since there is lots of sunlight in the summer some small losses because vertical panels aren't perfectly aligned is neither here nor there. However, in the winter with lower levels of sunlight having vertical panels does maximise collection for those of us in higher latitudes. The UK is 50 - 60'N.

[coopec43]

Originally Posted by Wandering1

If you are going to pole mount panels, you must be thinking of really small panels? Pole mounts would have to by massive to support a large panel. Why not just mount on the guardrails? This is how we mount 720w of solar on our ketch.
We add an additional 200w of roving panel at anchor. The guardrail mounted panels can be tilted to point at the sun when sailing.
We regularly exceed the manufacturer’s rated peak output for our cheap 180w panels, not bifacial, by up to 15%. Next year, we will likely swap them for some new bifacial panels mounted in the same way, simply because these are getting old. I am not convinced by the hype of bifacial and reading some scholarly articles about performance, it would appear that a gain of about 4-6% is realistic. If I can buy bifacial for the same price then its still worth it

I think my "Pole mounted" panels will actually be mounted on the guardrails like yours but I'd want them adjustable port/stbd and for/aft (That wouldn't be hard to do). As for wattage maybe x2 200W?

[coopec43]

Thanks for that Pete.

I found this article informative too. It covers the light spectrum and what solar panels use to convert to energy

https://www.thinkepic.com/solar/can-...nfrared-light/

[rslifkin]

I wouldn't go too crazy with making the panels adjustable unless it's easy to do. Unless you're really, really far north or south, pointing the panels straight up is often an acceptable compromise (especially during the summer). Getting some reflection off the water and deck onto the backside (which will be more effective with the panels flat) will help make up for some of the loss from not being angled optimally.

Even with our panels sitting almost flat, on a good day in mid summer I've seen a best daily output of 3.7 kwh from 820 watts of panels. Compared to most of the guidelines for what output to expect, that's pretty darn good.

[s/v Jedi]

Originally Posted by rslifkin

I wouldn't go too crazy with making the panels adjustable unless it's easy to do. Unless you're really, really far north or south, pointing the panels straight up is often an acceptable compromise (especially during the summer). Getting some reflection off the water and deck onto the backside (which will be more effective with the panels flat) will help make up for some of the loss from not being angled optimally.

Even with our panels sitting almost flat, on a good day in mid summer I've seen a best daily output of 3.7 kwh from 820 watts of panels. Compared to most of the guidelines for what output to expect, that's pretty darn good.

That’s 4.5Wh per installed W of panel. In other words it produced 100% of rated output for 4.5 hours that day.

My 1,800W bifacial array has a record of 9.03kWh which is 5 Wh per installed W of panel. But that’s up until now in the northern Bahamas so it will still get better in the summer.

[Wandering1]

Originally Posted by s/v Jedi

That’s 4.5Wh per installed W of panel. In other words it produced 100% of rated output for 4.5 hours that day.

My 1,800W bifacial array has a record of 9.03kWh which is 5 Wh per installed W of panel. But that’s up until now in the northern Bahamas so it will still get better in the summer.

I just had a look at my panel output. I have a lot smaller panels than you. 2x180w in series on each side of the boat plus some roving flexi panels50wx4. The starboard 360w set have peaked last week at 2.36kw so by my calculations that is 6.6Wh per W of installed panel. These are cheap mono panels tilted towards the sun

[rslifkin]

Originally Posted by s/v Jedi

That’s 4.5Wh per installed W of panel. In other words it produced 100% of rated output for 4.5 hours that day.

My 1,800W bifacial array has a record of 9.03kWh which is 5 Wh per installed W of panel. But that’s up until now in the northern Bahamas so it will still get better in the summer.

Exactly. Most guidelines I see for monofacial panels say to expect 3 - 4 WH per W on a good day, so getting ~4.5 sometimes is pretty good in my book.

[Jdege]

I've seen bifacial panels mounted vertically, aligned north-south. They get only reflected sunlight at noon, but generate more power in the morning and evening.

The arrangement yields no more energy in total, but it's peak power better matches usual household demand.

(And, being vertical, it doesn't need to have snow brushed off.)

[s/v Jedi]

Originally Posted by Wandering1

I just had a look at my panel output. I have a lot smaller panels than you. 2x180w in series on each side of the boat plus some roving flexi panels50wx4. The starboard 360w set have peaked last week at 2.36kw so by my calculations that is 6.6Wh per W of installed panel. These are cheap mono panels tilted towards the sun

That is very good. What controller and which location are you? I can’t tilt my array unfortunately…