Mmm, not sure. Does that mean if the panel is 25dec from perpendicular you only get abt 40% of max?
Yes that is the general drift of it.
I also observed in previous years when I had loose portable panels that in strong sunlight the panels get very hot flat on the ground and the output is noticeably reduced by this effect. So when I played with them I got noticeably more current by angling the panels 'a bit' and allowing them to cool by the convection effect. Sorry no actual figures to quote. But I did make some stands to hold them at an angle after that.
Jaahn
Thanks Jaahn,
Good to put a number to it even if it is approximate.
I must admit I'm a little surprised that only 25dec reduces the effective efficiencies so much. ( not questioning your numbers) Panels on van roofs must have a pathetic out put during winter in Vic.
It explains my observations.
Edit: perhaps the most informative bit of info I have gor from the forum in months.
Thx again jaahn.
-- Edited by oldbloke on Sunday 12th of June 2022 07:38:40 PM
Whenarewethere said
08:21 PM Jun 12, 2022
Just sketch on the back of an envelope any angle you want, divide the angled width of the parallel lines by the width of the overhead sun, then multiply by watts.
Or on your smartphone calculator: Panel Watts sin angle = Watts you will get.
Jaahn said
08:05 AM Jun 13, 2022
Hi oldbloke
Thanks for the kind comment. The theory says the output does fall as the panels get hot. My experience years ago camping with a couple of panels, is that flat on the ground they do get very hot. In full sun in summer you can hardly put your hand on them. At my house the solar output is best on a clear sunny day with a light breeze which keeps the panels cool.
If you fit panels to a caravan roof then it has always been recommended to leave a 50mm gap to allow cooling air to circulate under them. So glueing flexible panels direct to the roof is not so good. They might not suffer as much as glass panels though. But some people have had poor experiences with flexible panels which can have a short life, even thought they are more expensive.
"Most solar panels have a temperature coefficient of around -0.3% / °C to -0.5% / °C. For example, SunPowers solar panels all have a temperature coefficient of -0.37% / °C.
What this means is that for every 1°C above 25°C, SunPowers solar panels decrease in efficiency by 0.37%. So, if your panels are at 35°C (95°F) and have an overall efficiency of 17%, then their true efficiency at that temperature will be closer to 16.4%."
I do believe that caravans with flat panels on the roof do struggle to get enough power down south. Made worse by trees and other shade factors like camping down near the river and similar nice places. Extra portable panels with long cables are one answer to that. Most just use gennies. Mike has talked about his answers. This year has been bad with the lack of sun also.
Jaahn
-- Edited by Jaahn on Monday 13th of June 2022 08:12:27 AM
swamp said
08:26 AM Jul 6, 2022
hi Having a camper with MPPT and a combo of 200w fixed /roof and 200w portable totalling 400watts works for most of my situations . Wired in parallel to allow for shade . Large cabling . Using 1 or 2 agm 120ah . Following the sun is not a problem .
Remember the PSH [peak sun hours ] in southern states can halve in colder months therefore you need at least double the size of wattage required in Vic or Tazzy .
So angle the panels or have xtra panels whatever floats your boat . I Vote for xtra wattage
-- Edited by swamp on Wednesday 6th of July 2022 08:28:41 AM
TimTim said
12:03 AM Jul 30, 2022
I have never tested any of my solar my solar panels in relation to the sun angle except for being flat and directly facing the sun. Interestingly i came across this video of Will Prowses in which he testes solar panels at different angles. The results show very little difference in output between 10 and 40 degrees and in looking at the figures I would say very little difference between 0 and 40 degrees.
-- Edited by TimTim on Saturday 30th of July 2022 01:47:41 AM
I have never tested any of my solar my solar panels in relation to the sun angle except for being flat and directly facing the sun. Interestingly i came across this video of Will Prowses in which he testes solar panels at different angles. The results show very little difference in output between 10 and 40 degrees and in looking at the figures I would say very little difference between 0 and 40 degrees.
-- Edited by TimTim on Saturday 30th of July 2022 01:47:41 AM
Too much over thinking these days about solar panel angles for caravans.
With the new light weight panels available today just install more capacity and you will no longer need to worry about angles. Set and forget especially with Lithium batteries.
Additionally, you will create a cooler van with much of the roof covered.
Works for me.
Mike Harding said
12:16 PM Jul 30, 2022
I will speculate the incidence of bifacial solar panels used by the camping and nomad community is of the order of 0.0000001%
https://www.semprius.com/bifacial-solar-panels/
Mike Harding said
12:38 PM Jul 30, 2022
Dick0 wrote:
Too much over thinking these days about solar panel angles for caravans.
With the new light weight panels available today just install more capacity and you will no longer need to worry about angles. Set and forget especially with Lithium batteries.
You recently posted that you were camped near Longreach, Qld. In July in Longreach 800W of flat panel will produce 85kWh of energy.
I am near Stawell, Vic. In July in Stawell 800W of flat panel will produce 41kWh of energy.
However, if I set my panels at 65d and move them a few times during the day they will produce 81kWh of energy.
Statement of the ilk "Just buy more panels" are nieave, simplistic and fail to understand all the issues associated with solar harvesting in a mobile situation.
Dick0 said
12:41 PM Jul 30, 2022
Mike Harding wrote:
I will speculate the incidence of bifacial solar panels used by the camping and nomad community is of the order of 0.0000001%
https://www.semprius.com/bifacial-solar-panels/
And you would be correct.
Also, they are heavier so why would they be used, especially for caravans and portable applications.
Dick0 said
01:19 PM Jul 30, 2022
Mike Harding wrote:
Dick0 wrote:
Too much over thinking these days about solar panel angles for caravans.
With the new light weight panels available today just install more capacity and you will no longer need to worry about angles. Set and forget especially with Lithium batteries.
You recently posted that you were camped near Longreach, Qld. In July in Longreach 800W of flat panel will produce 85kWh of energy.
I am near Stawell, Vic. In July in Stawell 800W of flat panel will produce 41kWh of energy.
However, if I set my panels at 65d and move them a few times during the day they will produce 81kWh of energy.
Statement of the ilk "Just buy more panels" are nieave, simplistic and fail to understand all the issues associated with solar harvesting in a mobile situation.
Travelling to FNQ I had five days straight of wet and inclement weather, however, my batteries took on full charge by mere Daylight.
I stress again, I post here what works for me and do not, as you, offend and belittle others because you disagree with them.
Also, I do not tell others what they should or should not do, rather, suggest and recommend what works for me.
So, to you, everyone with whom you disagree is naïve, simplistic and lacks understanding.
Again, I stress what works for me...and it does work for me.
Mike Harding said
02:03 PM Jul 30, 2022
Dick0 wrote:
I stress again, I post here what works for me and do not, as you, offend and belittle others because you disagree with them.
You make assertive posts regarding a technical subject of which you have little knowledge. You look at a very narrow focus (ie. yours) associated with gathering solar energy and you assume your approach will suit everyone else - it won't! Then you get all grumpy when someone with good knowledge and qualifications contradicts you. I have spent a working life-time at the front edge of electronics and I *do* have some idea what I'm talking about. If I am wrong then come back to me with the facts and mathematics of *why* I am wrong and I'll change my position and be grateful to you for correcting me. That's engineering for you, it's not about pride.
This is a major issue with internet forums and it's usually why knowledgeable people (eg. Collyn Rivers) stop posting; we get fed up with people making definitive technical statement when they are really just presenting confirmation bias.
I may be an arrogant pr!ck but, electronically, I'm usually a correct arrogant pr!ck.
jegog said
02:31 PM Jul 30, 2022
Mike Harding suggested that there was something wrong with another's testing methodology when it returned a result that he did not expect - all, I suspect, without watching the utube video.
Had he watched the video he might not have made that comment.
My post in reply was to point out that there are many different types of solar cells with vastly different characteristics.
As for his comment re the usage of that type of panel by the grey nomad community, well I was not suggesting that the shown panels should be mounted on caravans, and as I just said, I was pointing out that there are many different types of solar cells.
However there may be readers who have a home, and having it pointed out that not all solar cells are the same might just be beneficial.
Dick0 said
02:33 PM Jul 30, 2022
Mike Harding wrote:
Dick0 wrote:
I stress again, I post here what works for me and do not, as you, offend and belittle others because you disagree with them.
You make assertive posts regarding a technical subject of which you have little knowledge. You look at a very narrow focus (ie. yours) associated with gathering solar energy and you assume your approach will suit everyone else - it won't! Then you get all grumpy when someone with good knowledge and qualifications contradicts you. I have spent a working life-time at the front edge of electronics and I *do* have some idea what I'm talking about. If I am wrong then come back to me with the facts and mathematics of *why* I am wrong and I'll change my position and be grateful to you for correcting me. That's engineering for you, it's not about pride.
This is a major issue with internet forums and it's usually why knowledgeable people (eg. Collyn Rivers) stop posting; we get fed up with people making definitive technical statement when they are really just presenting confirmation bias.
I may be an arrogant pr!ck but, electronically, I'm usually a correct arrogant pr!ck.
My goodness, you even call yourself an arrogant pr!ck.
Mike Harding said
02:44 PM Jul 30, 2022
Dick0 wrote:
My goodness, you even call yourself an arrogant pr!ck.
Sure: arrogance is one of my personality failings.
How about you Dick0, what are your personality flaws? Or do you not have any?
Dick0 said
04:20 PM Jul 30, 2022
Mike Harding wrote:
Dick0 wrote:
My goodness, you even call yourself an arrogant pr!ck.
Sure: arrogance is one of my personality failings.
How about you Dick0, what are your personality flaws? Or do you not have any?
Time for you to take a Chill Pill and stop being personally abusive.
Mike Harding said
04:25 PM Jul 30, 2022
Thanks Dick0, you have answered my question.
TimTim said
03:44 PM Aug 1, 2022
There was nothing wrong with his simplistic test but depending on your location and panels you have you cant expect to have similar results.
Thanks Jaahn,
Good to put a number to it even if it is approximate.
I must admit I'm a little surprised that only 25dec reduces the effective efficiencies so much. ( not questioning your numbers) Panels on van roofs must have a pathetic out put during winter in Vic.
It explains my observations.
Edit: perhaps the most informative bit of info I have gor from the forum in months.
Thx again jaahn.
-- Edited by oldbloke on Sunday 12th of June 2022 07:38:40 PM
Just sketch on the back of an envelope any angle you want, divide the angled width of the parallel lines by the width of the overhead sun, then multiply by watts.
Or on your smartphone calculator: Panel Watts sin angle = Watts you will get.
Hi oldbloke
Thanks for the kind comment. The theory says the output does fall as the panels get hot. My experience years ago camping with a couple of panels, is that flat on the ground they do get very hot. In full sun in summer you can hardly put your hand on them. At my house the solar output is best on a clear sunny day with a light breeze which keeps the panels cool.
If you fit panels to a caravan roof then it has always been recommended to leave a 50mm gap to allow cooling air to circulate under them. So glueing flexible panels direct to the roof is not so good. They might not suffer as much as glass panels though. But some people have had poor experiences with flexible panels which can have a short life, even thought they are more expensive.
Here is some information on the loss of output VS temperature of the panel. https://www.solar.com/learn/does-solar-panel-temperature-coefficient-matter/
"Most solar panels have a temperature coefficient of around -0.3% / °C to -0.5% / °C. For example, SunPowers solar panels all have a temperature coefficient of -0.37% / °C.
What this means is that for every 1°C above 25°C, SunPowers solar panels decrease in efficiency by 0.37%. So, if your panels are at 35°C (95°F) and have an overall efficiency of 17%, then their true efficiency at that temperature will be closer to 16.4%."
I do believe that caravans with flat panels on the roof do struggle to get enough power down south. Made worse by trees and other shade factors like camping down near the river and similar nice places. Extra portable panels with long cables are one answer to that. Most just use gennies. Mike has talked about his answers. This year has been bad with the lack of sun also.
Jaahn
-- Edited by Jaahn on Monday 13th of June 2022 08:12:27 AM
hi
Having a camper with MPPT and a combo of 200w fixed /roof and 200w portable totalling 400watts works for most of my situations . Wired in parallel to allow for shade . Large cabling . Using 1 or 2 agm 120ah .
Following the sun is not a problem .
Remember the PSH [peak sun hours ] in southern states can halve in colder months therefore you need at least double the size of wattage required in Vic or Tazzy .
So angle the panels or have xtra panels whatever floats your boat . I Vote for xtra wattage
-- Edited by swamp on Wednesday 6th of July 2022 08:28:41 AM
I have never tested any of my solar my solar panels in relation to the sun angle except for being flat and directly facing the sun. Interestingly i came across this video of Will Prowses in which he testes solar panels at different angles. The results show very little difference in output between 10 and 40 degrees and in looking at the figures I would say very little difference between 0 and 40 degrees.
-- Edited by TimTim on Saturday 30th of July 2022 01:47:41 AM
Then I suggest there's something wrong with his experiment.
Not only does my experience show a difference but if you adjust angles in this calculator you'll also see one:
Solar calculator
As Sol was Fong of saying "Oils ain't oils".
A lot depends on the panel being used and it's mounting.
Too much over thinking these days about solar panel angles for caravans.
With the new light weight panels available today just install more capacity and you will no longer need to worry about angles. Set and forget especially with Lithium batteries.
Additionally, you will create a cooler van with much of the roof covered.
Works for me.
I will speculate the incidence of bifacial solar panels used by the camping and nomad community is of the order of 0.0000001%
https://www.semprius.com/bifacial-solar-panels/
You recently posted that you were camped near Longreach, Qld. In July in Longreach 800W of flat panel will produce 85kWh of energy.
I am near Stawell, Vic. In July in Stawell 800W of flat panel will produce 41kWh of energy.
However, if I set my panels at 65d and move them a few times during the day they will produce 81kWh of energy.
Statement of the ilk "Just buy more panels" are nieave, simplistic and fail to understand all the issues associated with solar harvesting in a mobile situation.
And you would be correct.
Also, they are heavier so why would they be used, especially for caravans and portable applications.
Travelling to FNQ I had five days straight of wet and inclement weather, however, my batteries took on full charge by mere Daylight.
I stress again, I post here what works for me and do not, as you, offend and belittle others because you disagree with them.
Also, I do not tell others what they should or should not do, rather, suggest and recommend what works for me.
So, to you, everyone with whom you disagree is naïve, simplistic and lacks understanding.
Again, I stress what works for me...and it does work for me.
You make assertive posts regarding a technical subject of which you have little knowledge. You look at a very narrow focus (ie. yours) associated with gathering solar energy and you assume your approach will suit everyone else - it won't! Then you get all grumpy when someone with good knowledge and qualifications contradicts you. I have spent a working life-time at the front edge of electronics and I *do* have some idea what I'm talking about. If I am wrong then come back to me with the facts and mathematics of *why* I am wrong and I'll change my position and be grateful to you for correcting me. That's engineering for you, it's not about pride.
This is a major issue with internet forums and it's usually why knowledgeable people (eg. Collyn Rivers) stop posting; we get fed up with people making definitive technical statement when they are really just presenting confirmation bias.
I may be an arrogant pr!ck but, electronically, I'm usually a correct arrogant pr!ck.
Had he watched the video he might not have made that comment.
My post in reply was to point out that there are many different types of solar cells with vastly different characteristics.
As for his comment re the usage of that type of panel by the grey nomad community, well I was not suggesting that the shown panels should be mounted on caravans, and as I just said, I was pointing out that there are many different types of solar cells.
However there may be readers who have a home, and having it pointed out that not all solar cells are the same might just be beneficial.
My goodness, you even call yourself an arrogant pr!ck.
Sure: arrogance is one of my personality failings.
How about you Dick0, what are your personality flaws? Or do you not have any?
Time for you to take a Chill Pill and stop being personally abusive.
Thanks Dick0, you have answered my question.
There was nothing wrong with his simplistic test but depending on your location and panels you have you cant expect to have similar results.
https://www.youtube.com/watch?v=c-auRHKq2-A