Flexible solar panels

[Highwaygirl1078]

Has anyone tried the flexible solar panels that adhere to the roof with an adhesive as opposed to brackets? I’ve just started looking into them so know nothing about cost, companies, installation etc. I’m just at the beginning of my fact finding mission. Thanks!

[Sehnsucht]

I just asked my fleet's maintenance department about the ones installed on our trucks and they referred me to the brand we use, Bergstrom. I googled it and they have solutions for a variety of applications including motorcoach and RV. Feel free to check it out. I plan to do more research on these myself as it seems like this should be a pretty ideal solution for the curved skoolie roof.

[Danjo]

There’s a member on this site that did the entire roof of their 40 footer. I asked them and they said if they were to do it again that they would have made an air gap. I was originally going to do this because I thought that flat panels on the dome of my Thomas would stand off the roof too much and make it like a wing. So for a long while I burned way too many cycles figuring out the best way to make them stand off. Then I read a lot of lackluster reviews and then I got up there with a. Straight edge and found that with the height of low profile unistrut a flat panel wouldn’t stand off too much. So this is what I got

[Sehnsucht]

I recall a member reply to a similar topic and the reason as I recall for standing them off the roof was that they seemed to generate a lot of radiant heat from all sides so the air gap reduced the transfer of this heat against the metal roof of the bus. I am not aware of any such unwanted heat buildup with the systems we install on semis but there could be two possible explanations: one is that the sleeper cab roof is fiberglass and the other is that the peel-and-stick panels don't have a lot of metal frames and glass exteriors which I can imagine would get quite warm under direct sunlight anyways. I too suffer from over-analysis paralysis and I started wondering if a novel solution to the too-hot-to-handle solar panel issue might be to go ahead and stand them off and then pump a closed circuit of water or similar heat absorptive fluid through metal pipes beneath the hot panels, then cycling through a water heater where that otherwise unwanted heat can warm potable water for sink and shower. In closed circuit mean to say not the engine coolant system because that would seem counterproductive and I don't propose pumping the usable water through pipes exposed to the exterior of the vehicle. Also, since such a system is only feasible when the sun is shining anyways then the pump to move this fluid from roof to tank would be solar powered as well, eliminating the parasitic energy consumption of a pump driven by the engine or house batteries. A backup water heating solution should not be excluded however for those days and seasons when insufficient solar capture would leave you without hot water. Just some thoughts I think as I ply the highways.

[Iceni John]

Standard PV panels have a 25-year performance warranty. How long (if any) warranty do flex panels have? The general consensus of opinion is that flex panels simply don't last very long.

[Frqnt-Flyr]

I have a couple on my bus. They seem to work ok. Honestly I don't know enough about solar to be able to say much about them. The most I have seen the charge controller putting into the batteries is about 3 amps.

https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Danjo]

Originally Posted by Iceni John

Standard PV panels have a 25-year performance warranty. How long (if any) warranty do flex panels have? The general consensus of opinion is that flex panels simply don't last very long.

I was going to buy Renogy flexible panels. I called them up and was told the flexible panels carry the same 25 year warranty as the rigid ones. The guy also said that they don’t generate more RMAs for flexible panels.

[kazetsukai]

These might work better for our shorty build. If the body was sheet metal I'd just use strut like the big one, but I fear doing anything to fiberglass.


I'll poke around on YouTube to see how these do in hail...

[Skoolmee]

Originally Posted by Sehnsucht

I recall a member reply to a similar topic and the reason as I recall for standing them off the roof was that they seemed to generate a lot of radiant heat from all sides so the air gap reduced the transfer of this heat against the metal roof of the bus. I am not aware of any such unwanted heat buildup with the systems we install on semis but there could be two possible explanations: one is that the sleeper cab roof is fiberglass and the other is that the peel-and-stick panels don't have a lot of metal frames and glass exteriors which I can imagine would get quite warm under direct sunlight anyways. I too suffer from over-analysis paralysis and I started wondering if a novel solution to the too-hot-to-handle solar panel issue might be to go ahead and stand them off and then pump a closed circuit of water or similar heat absorptive fluid through metal pipes beneath the hot panels, then cycling through a water heater where that otherwise unwanted heat can warm potable water for sink and shower. In closed circuit mean to say not the engine coolant system because that would seem counterproductive and I don't propose pumping the usable water through pipes exposed to the exterior of the vehicle. Also, since such a system is only feasible when the sun is shining anyways then the pump to move this fluid from roof to tank would be solar powered as well, eliminating the parasitic energy consumption of a pump driven by the engine or house batteries. A backup water heating solution should not be excluded however for those days and seasons when insufficient solar capture would leave you without hot water. Just some thoughts I think as I ply the highways.

Do you envision any freezing issues in the closed loop if you visited areas with freezing temps and had a day with no sun?

[Sehnsucht]

Originally Posted by Skoolmee

Do you envision any freezing issues in the closed loop if you visited areas with freezing temps and had a day with no sun?

Potentially yes which is why I do not think it's a good idea to pump the potable water to the roof. if it is a system like the engine cooling system which uses water and antifreeze or if it's some sort of oil-based system then I think that would be a safer solution. Also if it does spring a leak it will not the leaking the fresh water supply.

[john61ct]

Did not read the whole thread.

Avoid semi flex panels, only last a small fraction of framed panel lifespan, maybe average 3-4 years.

Too much heat to glue direct to roof, need a rigid (non flexing) aluminum plate with airflow below

[dzl_]

Solar panel performance is relative to temperature, as temperature rises power output decreases, as temperature falls power output increases.


Flexible panels have no air gap behind them and get much hotter than conventional panels, this is one of the reasons the power output tends to be substantially lower per square foot. Also probably one of the reasons they last <1/5th the time that conventional panels do

[Sehnsucht]

Originally Posted by dzl_

Solar panel performance is relative to temperature, as temperature rises power output decreases, as temperature falls power output increases.


Flexible panels have no air gap behind them and get much hotter than conventional panels, this is one of the reasons the power output tends to be substantially lower per square foot. Also probably one of the reasons they last <1/5th the time that conventional panels do

Not to disagree with you but I read it was the other way around, that solar panels don't really hit their peak efficiency until they've warmed up. These solar farms that are popping up all over the place seem to have some sort of preheat system which is supposed to improve their output earlier in the morning before the sun has had a chance to warm up the panels naturally. It's probably this kind of nuanced public information that causes a lot of confusion for newbs to the solar 'sichiation'!

[john61ct]

No, colder is better for PV output efficiency, it's batteries that work better warm.

Takes a 2-min google first to stop spreading misinformation

[Sehnsucht]

Originally Posted by john61ct

No, colder is better for PV output efficiency, it's batteries that work better warm.

Takes a 2-min google first to stop spreading misinformation

Oh my! I took your advice and spent 2 minutes on Google where I learned that solar panels are actually CONTRIBUTING to global warming. That cinched it for me, I'm never going to install solar panels! It'll be good old reliable fossil fuels for me until the last drop of liquid dinosaur fossils is pumped from the earth and as a result the entire crust of the planet implodes like a cheap taco shell!

(offered as parody)

[ol trunt]

I'm not smart enough to see the parody--how about offering up a couple of web sites to help clarify your meaning.
Jack

[john61ct]

Or not, would be fine too.

[Sehnsucht]

It was humorous if not mildly sarcastic illustration that googling a topic is not necessarily the solution for dispelling common myths and misinformation. Google simply indexes and serves up content without regard to how accurate or honest it is. I actually DID find websites purporting the global warming ills of solar panels but that wasn't what I was looking for - rather I was looking for the article I read some months back about the pre-warming feature being incorporated into new solar panel farms in my area which I now wish I had bookmarked at the time. Alas I did not find it but there was a lot of information on both sides. The catch for someone trying to learn about a topic via Google is being able to discern which sources of information are legitimate and which are wacko conspiracy theory masquerading as informative. One only need consider the current global epidemic to understand how difficult it is to parse fact from fiction when the president of the United States starts advocating Lysol ingestion and he wasn't even Avant-garde - people were being told they could drink Clorox on the very first week and some were dumb enough to believe and do it!

In the case of the solar panels being more or less efficient with temperature it seems that there is an operating range which is most efficient. Obviously the solar potential is greater in summer but it's more because of the directness of the sun versus most of us probably experiencing the lesser solar opportunity in winter with the indirect sunlight even in otherwise sunny days. As to the pre-warming feature I recalled, this is likely relating to the potential snow accumulation on solar panels in winter States which could take hours to melt from sunlight during which time the panels cannot achieve output until they are unobstructed. So hopefully that clears that up.

[Danjo]

Originally Posted by Sehnsucht

It was humorous if not mildly sarcastic illustration that googling a topic is not necessarily the solution for dispelling common myths and misinformation. Google simply indexes and serves up content without regard to how accurate or honest it is. I actually DID find websites purporting the global warming ills of solar panels but that wasn't what I was looking for - rather I was looking for the article I read some months back about the pre-warming feature being incorporated into new solar panel farms in my area which I now wish I had bookmarked at the time. Alas I did not find it but there was a lot of information on both sides. The catch for someone trying to learn about a topic via Google is being able to discern which sources of information are legitimate and which are wacko conspiracy theory masquerading as informative. One only need consider the current global epidemic to understand how difficult it is to parse fact from fiction when the president of the United States starts advocating Lysol ingestion and he wasn't even Avant-garde - people were being told they could drink Clorox on the very first week and some were dumb enough to believe and do it!

In the case of the solar panels being more or less efficient with temperature it seems that there is an operating range which is most efficient. Obviously the solar potential is greater in summer but it's more because of the directness of the sun versus most of us probably experiencing the lesser solar opportunity in winter with the indirect sunlight even in otherwise sunny days. As to the pre-warming feature I recalled, this is likely relating to the potential snow accumulation on solar panels in winter States which could take hours to melt from sunlight during which time the panels cannot achieve output until they are unobstructed. So hopefully that clears that up.

Renogy told me the optimal operating temperature for their panels is 78F. I can imagine being able to fry an egg on directly applied flexible panel mid summer.

[dzl_]

No need to google anything, look on any solar panel datasheet or the sticker on the back.


Here is one example:








Pay attention to the value: Temp Coefficient of Pmax: : -.42%/*C


What this means is that

1. for every degree (Celsius) above 25*C, power output drops 0.42%
2. for every degree (Celsius) below 25*C, power output increases 0.42%

That means at 0*C/32*F your 80W panel will be producing a max of almost 90W and at 50*C/120*F your 80W panel will be producing a max of only about 70W.


Here is an article and here is another article on temperature and solar panels and a video from reputable seller.


I don't mean to kick a dead horse but I want to be very clear and nip this in the bud, it is very much accepted fact in the solar industry that PV panels perform better in cold conditions and perform worse in hot conditions. We don't need to complicate it.



The reference point for solar (called STC) is 25*C/77*F, your panels power (Watt) rating is at this temperature, as temps drop power will increase, as temps rise power will decrease.