Optimal winter angle for cloudy days without sun

[m0onspell]

From what I am seeing most of the people reagard more perpendicular angle like 60 degrees as the most optimal tilt for the winter. The reason being is that the sun is low during the winter.
So they're orienting towards the sun. Which should make sense, right? But the thing is that in my area most of the time there is no sun in the winter. Cloudy days, sky is like a concrete, I am sure you know what I mean. There may be a few sunny days in a month.
So I also found that quite a few folks are setting their panels to zero degree angle and even showing some figures claiming that such an angle is the most optimal for cloudy winter days. The reason is because panels are able to absorb more of the ambient light.
Which makes sense to me. It is worth mentioning that my array will be ground mounted. I want to optimize for the winter exclusively and I don't really care about the effectiveness of my panels during rest of the year. So during cloudy days when the total output is very low, those additional 30% would really matter to me. On rare occasions of a sunny day I think I'll still be able to charge my batteries, even though it may be slower than if my panels were set to a perpendicular angle.
But then there's another factor: snow. If you set to zero degrees, you'll probably have to clean your panels all the time, because the snow just won't come off. Perpendicular angle has a clear advantage here.
So that leads me to a conclusion that something like 10-20 degrees would be the most optimal angle for the scenario I described. Since the snow should be able to come off by itself easier than if it is 0 degree (although tbh I am not sure how much tilt is minimum required for the snow to come off). And the angle is pretty flat, so the panels should be able to absorb more of the ambient light.
Would appreciate your thoughts.

 

[SeaGal]

Yep - agree with all that. My ground mounts are 15 degrees on Renusol tubs. Don't get much snow here, but the 15 degrees is enough to keep them clean with the rain washing any debris off (leaves / dust etc). Mine are E-W mounted and on a dull cloudy day, get same output from either side, irrespective of what time of the day it is.

 

[garetwo]

So that leads me to a conclusion that something like 10-20 degrees would be the most optimal angle for the scenario I described. Since the snow should be able to come off by itself easier than if it is 0 degree (although tbh I am not sure how much tilt is minimum required for the snow to come off). And the angle is pretty flat, so the panels should be able to absorb more of the ambient light.

Could you set up one panel and monitor its voltage output while one day have it at 0 degrees, then next some number more? What a neat conclusion! Thanks for sharing it.

 

[45North]

Best winter tilt is latitude +15 deg.
I don't know where you are but for me that would be 45 + 15 = 60 deg.
For cloudy days you need to add more battery storage to create more days of autonomy.

 

[SeaGal]

Could you set up one panel and monitor its voltage output while one day have it at 0 degrees, then next some number more?

If you wanted to measure it, I'd say set up several panels at different angles and measure at the same time. Then you would be measuring output for identical luminescence. If you do it over multiple days the chances are that the luminescence will vary more than the angle;s effect.

 

[Zwy]

From what I am seeing most of the people reagard more perpendicular angle like 60 degrees as the most optimal tilt for the winter. The reason being is that the sun is low during the winter.
So they're orienting towards the sun. Which should make sense, right? But the thing is that in my area most of the time there is no sun in the winter. Cloudy days, sky is like a concrete, I am sure you know what I mean. There may be a few sunny days in a month.

Mark it down on a calendar. It might surprise you.

If you use JRC for computing panel output, it is derived from real data and not necessarily theoretical data.

So I also found that quite a few folks are setting their panels to zero degree angle and even showing some figures claiming that such an angle is the most optimal for cloudy winter days. The reason is because panels are able to absorb more of the ambient light.

In cloudy conditions, yes. But the panels will be severely limited for days of peak power.

Which makes sense to me. It is worth mentioning that my array will be ground mounted. I want to optimize for the winter exclusively and I don't really care about the effectiveness of my panels during rest of the year. So during cloudy days when the total output is very low, those additional 30% would really matter to me. On rare occasions of a sunny day I think I'll still be able to charge my batteries, even though it may be slower than if my panels were set to a perpendicular angle.
But then there's another factor: snow. If you set to zero degrees, you'll probably have to clean your panels all the time, because the snow just won't come off. Perpendicular angle has a clear advantage here.
So that leads me to a conclusion that something like 10-20 degrees would be the most optimal angle for the scenario I described. Since the snow should be able to come off by itself easier than if it is 0 degree (although tbh I am not sure how much tilt is minimum required for the snow to come off). And the angle is pretty flat, so the panels should be able to absorb more of the ambient light.
Would appreciate your thoughts.

Believe me, 10-20 degrees compared to 0 degrees won't make any difference when it comes to snow. It won't slide off.

 

[littleharbor2]

Could you set up one panel and monitor its voltage output while one day have it at 0 degrees, then next some number more? What a neat conclusion! Thanks for sharing it.

Voltage is meaningless. You can get full open circuit voltage indoors, under a lightbulb. It's the amount of current you can get flowing that matters.

 

[garetwo]

Voltage is meaningless. You can get full open circuit voltage indoors, under a lightbulb. It's the amount of current you can get flowing that matters.

So I should monitor current flow? To do that would you use a battery? Sorry, The correct question is, how can I see what angle produces the most current flow when using one panel as a test? Thanks LittleHarbor2.

 

[garetwo]

Best winter tilt is latitude +15 deg.
I don't know where you are but for me that would be 45 + 15 = 60 deg.
For cloudy days you need to add more battery storage to create more days of autonomy.

But is that tilt specific to "seeing" the sun? If the light is disbursed due to complete cloud coverage, or in this case some neat concrete sky, could that reflected light be better caught as m0onspell asked?

 

[littleharbor2]

So I should monitor current flow? To do that would you use a battery? Sorry, The correct question is, how can I see what angle produces the most current flow when using one panel as a test? Thanks LittleHarbor2.

When testing panels for prospective customers in the past I would take my DVM, (meter), and set it for current. This requires you to switch the red lead to the other connection port on the meter, (see photo). Plug the test leads into the MC-4 connectors, tilt the panel and watch the meter. When you have the best reading you are at best tilt.

 

[m0onspell]

Could you set up one panel and monitor its voltage output while one day have it at 0 degrees, then next some number more? What a neat conclusion! Thanks for sharing it.

I think to make a solid conclusion you'd have to monitor it for more than one day since there's a lot of factors that could affect the results. But I think I could take my portable panel and measure the output on a cloudy day while the panel is flat vs perpendicular. Maybe I'll do it at some point and share with you guys, thanks.

Best winter tilt is latitude +15 deg.
I don't know where you are but for me that would be 45 + 15 = 60 deg.
For cloudy days you need to add more battery storage to create more days of autonomy.

I guess you've ignored everything I wrote, but that's fine. Thanks.

If you wanted to measure it, I'd say set up several panels at different angles and measure at the same time. Then you would be measuring output for identical luminescence. If you do it over multiple days the chances are that the luminescence will vary more than the angle;s effect.

Or at least like I mentioned: take a portable panel, measure at one angle, immediately turn to another one, measure, done.
ButI don't really have a reason not to believe those people that are saying that laying panels flat would produce more output duringa cloudy day, although I may check it. I also don't have a doubt that perpendicular is better for a sunny winter day. I guess I was more curious to know if there are any other factors that may affect the results and what's people experience in practice.

Mark it down on a calendar. It might surprise you.

If you use JRC for computing panel output, it is derived from real data and not necessarily theoretical data.

I think what you're saying is that although it may seem like there's no sun, it is still there, but maybe less visible, so orienting towards the sun is still a better option? Well, I don't know, that's why I've created this topic. But I've seen proofs that 0 degree produces higher output during a cloudy day. So at least that should've told me something. Then I guess the question should be how many days are cloudy in my area during the winter? I think most of them are pretty cloudy. So there you can see to which conclusion it leads me. I'll play with the tool you've mentioned, seen it before, but didn't have time to deep dive. Thanks.

In cloudy conditions, yes. But the panels will be severely limited for days of peak power.

If there's a sun outside, there'll be more than enough energy to power my needs. ~6.5Kw of panels even at 30% should charge 5KWh battery bank resonably fast. But there's no doubt that being able to charge faster is a significant advantage.

Believe me, 10-20 degrees compared to 0 degrees won't make any difference when it comes to snow. It won't slide off.

Well, by definition there can't be no difference. There should be some difference. The question is if it is enough or not. I don't know if there are recommendations for a roof angle. I think it may be worth looking into that.

 

[m0onspell]

Plug the test leads into the MC-4 connectors, tilt the panel and watch the meter.

... it blows a fuse on your meter. Been there.
I don't know if it is safe to do it for larger panels, but what I did I just shorted plus and minus cables of the panel and measured current with my clamp meter. Worked fine for a portable 140w panel.

 

[garetwo]

If you wanted to measure it, I'd say set up several panels at different angles and measure at the same time. Then you would be measuring output for identical luminescence. If you do it over multiple days the chances are that the luminescence will vary more than the angle;s effect.

I do think this would be a great test. At the same time, if I lived where it is -41 degrees and it is snowing....I don't even want to test one panel unless it was set up while it was at least above zero AND some great kid would go wipe it off. I do not know how you all do it!

 

[littleharbor2]

... it blows a fuse on your meter. Been there.
I don't know if it is safe to do it for larger panels, but what I did I just shorted plus and minus cables of the panel and measured current with my clamp meter. Worked fine for a portable 140w panel.

It would if you have a panel with more than 10 amps. Some of the newer high wattage panels exceed 10 amps. My meter has a 20 amp limit so I never have to worry. One thing for sure, Don't forget to move the red lead back into the other port before testing battery voltage. Had to replace many a fuse when Forgetting this.

 

[SeaGal]

Don't forget to move the red lead back into the other port before testing battery voltage.

LOL.. I've run out of fingers counting how many times I've done that

 

[Zwy]

Well, by definition there can't be no difference. There should be some difference. The question is if it is enough or not. I don't know if there are recommendations for a roof angle. I think it may be worth looking into that.

There will not be much difference between 0 degrees and 10 to 20 degrees.

 

[m0onspell]

There will not be much difference between 0 degrees and 10 to 20 degrees.

yeah guess I have to cope

 

[SamDeleted]

yeah guess I have to cope
View attachment 179346

Hahaha

I think it's already been said, some go almost dead vertical for snow

My 44kW vertical and bifacial set in Finland.

New to the forum, new to the solar energy. Have 63 Bluesun bifacial 700W N-type shingled panels, 22 old electric poles, shit load of underground cable, 51 x 6m 40x40x3mm marine grade aluminium, 2 Bluesun 15kW on-grid inverters, 2 Deye 15/12kW hybrid inverters, 30kW lead acid battery and 4 x 5kW...

diysolarforum.com

 

[SparkyJJO]

If we ever buy our little country homestead (if interest rates ever come down) I plan on building ground mount(s). And - because I live to overengineer things - maybe I should plan on putting a pivot and counterbalance so it is easy to set to winter vs summer angles, AND flat, AND put a switched heat strip on the panels to aid in thawing them out. Set it flat most of the time in winter, but on sunny days flip it to the ideal angle for direct sun, or to brush and melt off a snow layer. Hm. Why do I make my life so much more difficult by dreaming up these stupid ideas ?

 

[SamDeleted]

Then I guess the question should be how many days are cloudy in my area during the winter? I think most of them are pretty cloudy.

Data should be available online ,


I think this is the real question