Solar Panels comparison

[Landsil]

Hi,

I'm in the research and money saving phase of getting a narrowboat.

 

I was really confused by all the solar panel options, what they mean, how they compare and how bad it will be if I go with flexible ones.

So I've made a simple comparison, basically a fancy spreadsheet.

 

I hope someone will find it useful, please feel free to let me know and suggestions for improvements. 

 

TL;DR:

1. Bigger frame panels provide more power per m² and more power per £ spent on them.
   1. This is not true for flex panels to such a degree.
2. Power per £ is significantly better in frame models.
3. Frame vs Flex power per m² is about the same (if we ignore angle).

 

TODO:

Researching and adding a graph of expected efficiency in UK per month (shade/sun) for flat roof and calculation of gains if someone aims panel twice a day.

Adding top down view of boats of different seizes with example roof coverage and possible power gain per type/month.

 

Have a great weekend everyone.

[Jen-in-Wellies]

Welcome to the forum.

One factor that should remove flex panels from your comparison entirely is lifespan. Flexi panels can only last a few years fixed to a steel roof, based on reported experience. The heat from the roof kills them and before it does that it significantly reduces their power output. Solar panel output drops with temperature. Rigids are usually a short distance above the roof and have cooling air available on both sides. No one really knows how long framed silicon cells last, but multiple decades.

A big contribution to the lower cost/W of big panels is that they are now made in huge numbers for buildings, so economies of scale kick in. Smaller panels are a more niche market and the price per W is higher as a result.

I'd suggest you are rather over thinking this!

 

[TheBiscuits]

 

Flexi panels cost a lot more per watt, if they are mounted on a roof they will cause rusting underneath and they will fail much earlier than you expect.  If they are on a curved roof they will also have less of the panel in direct sunshine in winter when it's most critical so are effectively even smaller.

 

The correct amount of rigid solar panels to fit depends on your available roof space and the size of your wallet.  On a narrowboat you are more likely to run out of room than pound notes unless you go for crazy expensive panels.  Don't bother with bifacial ones unless you can mount them three feet above the roof .

 

These opinions are for liveaboard use, obviously.  If you just want to keep batteries alive during winter on a leisure boat pretty much anything will do if there's no power being used for 6 months.

 

 

 

 

Crossposted with Jen.  Great minds and all that.

[Jen-in-Wellies]

Go too big on panel size and you increase the risk of them being taken out by arched bridges and tunnels. Also removes the option of walking on the roof, which can be handy when you are single handing a boat.

Keeping the panels clean is the easiest thing you can do to get good output. Removing dirt, Saharan dust storm sand, bird cr@p regularly.

 

[frangar]

I’m really happy with my CIGS flexi panels. They work really well on cloudy days too. They are designed for metal seam roofs on buildings so can put up with high surface heat…they also have a bitumen adhesive backing so hopefully seal better against water underneath…been fitted 18 months so far with no issues. I will admit they were more expensive than rigid panels but being long and thin fit my roof space well. I also didn’t want the boat to look like a floating solar farm! 

[matty40s]

Did you get Unisolar ones, or a new version. 

Following the roof repaint, I want to go this route in the spring having had 2 rigid panels on top for the last 7 years.

[frangar]

4 minutes ago, matty40s said:

Did you get Unisolar ones, or a new version. 

Following the roof repaint, I want to go this route in the spring having had 2 rigid panels on top for the last 7 years.

Went for the Miasole ones from Midsummer energy

 

https://midsummerenergy.co.uk/buy/flexible-solar-panels/miasole-125W-CIGS-flexible-solar-panel

 

Fitted 2 wired in parallel which has proved to be able to enable us to moor up for a a week or so when boating in the summer without any engine running and powering all the usual stuff on a modern live aboard  which was what I hoped..I have a hook up when back on the mooring for winter.

 

I find the curve of the roof means that they are slightly angled so pick up well...also seem to cope with shading from trees etc

 

They are running through a Victron Smartsolar 100/20 MPPT controller

 

I would say that I prepared the roof well before fitting....and be careful when fitting as I wouldn't fancy getting them back up in once piece!.

 

I see they now do UK made CIGS panels too...but at a greater cost....they seem to be slightly differing dimensions so one might fit the roof better than the other.

[David Mack]

The spreadsheet shows that framed panels of around 300W and upwards are much of a muchness on a per metre squared basis, so just buy the ones that fit your roof and are available at a reasonable price. Bimble sell used panels which are significantly cheaper than the quoted prices and just as good.

If you install as many panels as will reasonably fit on your roof you will have more than enough power for the summer and still not enough in winter (if you are a liveaboard). So angling the panels is hardly worth it. Stick with flat mounted panels which are better looking, easier to boat with, less vulnerable to wind and generally less hassle all round.

And avoid stick on - more expensive to buy, much shorter life, and your cabin roof will rust underneath them (unless you have a fibreglass roof).

Edited December 3, 2021 by David Mack

[frangar]

Just now, David Mack said:

 

And avoid stick on - more expensive to buy, much shorter life, and your cabin roof will rust underneath them (unless you have a fibreglass roof).

There are differing versions of stick on though....I agree about the ones that are aluminium or fibreglass backed but the CIGS panels are made very differently and have a thicker adhesive so flex more and can take up roof imperfections better....I thought long and hard before fitting mine but Im very happy so far. 

[Jen-in-Wellies]

45 minutes ago, frangar said:

There are differing versions of stick on though....I agree about the ones that are aluminium or fibreglass backed but the CIGS panels are made very differently and have a thicker adhesive so flex more and can take up roof imperfections better....I thought long and hard before fitting mine but Im very happy so far. 

Hope this continues. You've done your research. It isn't possible to know for sure for the panels you have will last until quite a few more years have passed. If some one is considering the various flexi panels around, then there is a potential risk that they could lose the entire investment in only a few years and that needs to be taken in to account. Rigid panels are known to be good for decades plus time frames. Two of the 80W panels on my boat are now 14 years old. Accidental damage aside, they should be good for at least a decade more.

 

Jen

[Tony Brooks]

It is not just heat causing problems for flexible panels. They also seem very prone to delaminating with a few years.

[matty40s]

34 minutes ago, Jen-in-Wellies said:

 Two of the 80W panels on my boat are now 14 years old. Accidental damage aside, they should be good for at least a decade more.

 

Jen

One of my 240w panels was free as the glass face was completely shattered at the house installation stage and the fitter just wanted it out of his garage. I fitted it 7 years ago and didnt do anything to look after it, it works perfectly!!!

[frangar]

3 minutes ago, matty40s said:

One of my 240w panels was free as the glass face was completely shattered at the house installation stage and the fitter just wanted it out of his garage. I fitted it 7 years ago and didnt do anything to look after it, it works perfectly!!!

Why are you wanting to change to flexible out of interest? 

[Landsil]

Thank you to everyone who took time to have a look.

 

I will check the tread every few days and update the page as new suggestions are added.

 

For now I will add notes about heat, reminder about impossible maintenance under flexi panels.

It's aimed at totally new people so reminder about cleaning is also great.

 

I'm interested in you saying flexi panels are physically breaking. I was under impression that can be walked on?

My personal plan was to eat the cost if I can in exchange for smooth roof that I can walk on when I need to.

Our initial plan was to have it very low to fit everywhere as we travel.

[IanD]

Flexi panels are at least 5x more expensive per watt, and definitely more prone to things like delamination, especially the cheaper ones. Getting hot isn't a problem for the PV inside the panel and any drop in output is only a few percent at most, and the flexi panels which use thinned mono cells have about the same output per square metre as rigid ones.

 

I wouldn't recommend flexi panels for a DIY fit, or even many boatbuilder fits -- the best way to get long life and good immunity to damage/leaks/rusting is to use (even more expensive) panels which include a semi-rigid core (e.g. aluminium) with rear connections, and use specialist methods (e.g. vacuum bonding) to bond them directly to a rigid steel roof over their entire area -- which then allows walking on them, but not with stilettos or hobnail boots. I know of one builder who does this (Finesse) who together with the panel supplier feels confident enough to offer a 10 year guarantee, I don't know about the others.

 

A roof-full of flexi panels costs something over £3000, OK if you're having a new boat built (maybe 2% of the total cost) but too expensive for most people, and they don't make sense from the money-saving point of view -- you've got to be willing to pay the extra for other reasons.

 

Go for flat panels, buy on cost per W and efficiency (Bimble have a comparison table), and flat mount as many as you can fit on the roof, preferably leaving enough room to walk down the sides so not much over 1m wide -- bear in mind that if you do this and overbalance and step on a panel it'll kill it, unlike flexi panels. They won't look as nice as flexi panels but they'll only be about 3" high which won't impact clearance to bridges and tunnels.

Edited December 3, 2021 by IanD

[BEngo]

Two boaters at our mooring fitted (diy) flexible solar panels.  Neither set was still working at two years old. Neither boater used the panel area for walking on.

 

Look at the guarantee for flexible panels and compare it with the guarantee for  framed rigid panels.  Typically the framed panel is warranted to be good  for 80% of new output after 25 years. Flexible panels tend to be guaranteed for 12 months.  

 

N

 

[IanD]

4 minutes ago, BEngo said:

Two boaters at our mooring fitted (diy) flexible solar panels.  Neither set was still working at two years old. Neither boater used the panel area for walking on.

 

Look at the guarantee for flexible panels and compare it with the guarantee for  framed rigid panels.  Typically the framed panel is warranted to be good  for 80% of new output after 25 years. Flexible panels tend to be guaranteed for 12 months.  

 

N

 

Which is true for low-cost DIY flexible panels, which is why they're a bad idea. It's not necessarily true for professionally-installed semi-flexible mono panels, but these are *very* expensive, as I said...

[matty40s]

1 hour ago, frangar said:

Why are you wanting to change to flexible out of interest? 

The large flat panels are functional but ugly, and we probably dont need as much power capability as we used to when CC ing.

[IanD]

12 minutes ago, matty40s said:

The large flat panels are functional but ugly, and we probably dont need as much power capability as we used to when CC ing.

You'd better have deep pockets then -- for comparison 6x 325W rigid panels like this (pretty much a roof-full) will cost £690 inc VAT:

 

https://www.bimblesolar.com/ja-325w-halfcell

 

12x reinforced semi-rigid 160W panels like this will cost £3700 inc. VAT, just over 5x more expensive:

 

https://www.photonicuniverse.com/en/catalog/full/438-160W-Black-Reinforced-semi-flexible-solar-panel-with-round-rear-junction-box-and-3m-cable-with-durable-ETFE-coating.html

 

But if you want them to be really durable you need to be extremely careful about how they're fitted, and I doubt that you can do a DIY job which would give maximum reliability (e.g. vacuum bonding to steel roof).

 

Obviously a smaller array will cost proportionally less, but the DIY reliability/fitting issues still remain.

Edited December 3, 2021 by IanD

[frangar]

3 minutes ago, matty40s said:

The large flat panels are functional but ugly, and we probably dont need as much power capability as we used to when CC ing.

Fair enough! I deffo agree with the ugly bit. I have fitted mine so I could get another pair if I felt the need but they are working just fine for us at the moment. 
 

To others saying flexibles have issues I think you need to realise there is a large difference between CIGS panels and what people traditionally mean by “flexible” both in physical construction and output….yes they are expensive but as ever you get what you pay for…they also have a 5yr warranty for construction and 25yr warranty on output. 

Just now, IanD said:

You'd better have deep pockets then -- for comparison 6x 325W rigid panel like this (pretty much a roof-full) will cost £690 inc VAT:

 

https://www.bimblesolar.com/ja-325w-halfcell

 

12x reinforced semi-rigid 160W panels like this will cost £3700 inc. VAT, just over 5x more expensive:

 

https://www.photonicuniverse.com/en/catalog/full/438-160W-Black-Reinforced-semi-flexible-solar-panel-with-round-rear-junction-box-and-3m-cable-with-durable-ETFE-coating.html

 

But if you want them to be really durable you need to be extremely careful about how they're fitted, and I doubt that you can do a DIY job which would give maximum reliability (e.g. vacuum bonding to roof).

Again what you are quoting as Flexible are the older tech….perhaps you might care to listen to those of us that actually have them…but as you seem to have banned most you might be in an echo chamber. 

[Tony Brooks]

2 minutes ago, frangar said:

Fair enough! I deffo agree with the ugly bit. I have fitted mine so I could get another pair if I felt the need but they are working just fine for us at the moment. 
 

To others saying flexibles have issues I think you need to realise there is a large difference between CIGS panels and what people traditionally mean by “flexible” both in physical construction and output….yes they are expensive but as ever you get what you pay for…they also have a 5yr warranty for construction and 25yr warranty on output. 

 

so did the flexibles that delaminated - - - -  until they tried to claim and then it was not a manufacturing fault so it must have been misuse/installation problem.

[matty40s]

13 minutes ago, frangar said:

Fair enough! I deffo agree with the ugly bit. I have fitted mine so I could get another pair if I felt the need but they are working just fine for us at the moment. 
 

To others saying flexibles have issues I think you need to realise there is a large difference between CIGS panels and what people traditionally mean by “flexible” both in physical construction and output….yes they are expensive but as ever you get what you pay for…they also have a 5yr warranty for construction and 25yr warranty on output. 

Again what you are quoting as Flexible are the older tech….perhaps you might care to listen to those of us that actually have them…but as you seem to have banned most you might be in an echo chamber. 

I refused to fit any more of those semi flexible ones about 5 years ago after repeated failures of solder joints between cells on more than one boat. 

The old Unisolar ones are still viable years on, I did try to buy some off a member on here on 2 separate occasions but 1st time Covid prevented pick up from his marina and 2nd time he just ignored me. 

[IanD]

38 minutes ago, Tony Brooks said:

 

so did the flexibles that delaminated - - - -  until they tried to claim and then it was not a manufacturing fault so it must have been misuse/installation problem.

Which it could well have been, depending on how they were installed. Or the panels weren't the kind of higher-quality semi-rigid ones that aren't as sensitive to this -- the truly "flexible" panels are much more prone to delaminating when stressed because there's nothing to stop them flexing, and it's this that tends to cause delamination and moisture ingress. CIGS panels have considerably lower output and are at least as expensive, but are promoted because they're "really flexible" -- it's not that they're newer or better, just different.

 

Unfortunately many of the flexible panel suppliers recommend all sorts of rubbish installation methods which are likely to lead to short lifetimes, and then claim it's not their problem as you say. The truth is that properly installing flexible panels to get good lifetime out of them is not quick or easy (or cheap), but people don't want to hear this so the manufacturers don't tell them, they say "easy to install"... 😞

 

Apart from poor choice of materials/manufacturing, what kills most "flexible" panels is actually flexing, so the key is to stop this happening. The semi-flexible panels use thinned monosilicon wafers (same material as rigid mono panels) laminated to an aluminium backing plate, they can't be bent to a smaller radius than several metres but this is enough for a curved narrowboat roof (thinned silicon is quite bendy). Once this is securely bonded down to a rigid curved roof (typically 4mm steel supported by cross-beams) it effectively becomes an integral part of the steel roof structure with negligible movement even when walked on -- but for this to work there have to be absolutely no voids or gaps between the panel and the roof, this has to be completely filled with glue, hence the use of vacuum sealing to pull the panel down onto the roof with uniform pressure across the entire surface until the glue dries.

 

Do all this (almost impossible for DIY) and the result will be long-lasting. Cut any corners or use more flexible panels (which is what most people do) and it won't be.

Edited December 3, 2021 by IanD

[frangar]

2 minutes ago, IanD said:

Which it could well have been, depending on how they were installed. Or the panels weren't the kind of higher-quality semi-rigid ones that aren't as sensitive to this -- the truly "flexible" panels are much more prone to delaminating when stressed because there's nothing to stop them flexing, and it's this that tends to cause delamination and moisture ingress. CIGS panels have considerably lower output and are at least as expensive, but are promoted because they're "really flexible" -- it's not that they're newer or better, just different.

 

Unfortunately many of the flexible panel suppliers recommend all sorts of rubbish installation methods which are likely to lead to short lifetimes, and then claim it's not their problem as you say. The truth is that properly installing flexible panels to get good lifetime out of them is not quick or easy (or cheap), but people don't want to hear this so the manufacturers don't tell them... 😞

 

Apart from poor choice of materials/manufacturing, what kills most "flexible" panels is actually flexing, so the key is to stop this happening. The semi-flexible panels use thinned monosilicon wafers (same material as rigid mono panels) laminated to an aluminium backing plate, they can't be bent to a smaller radius than several metres but this is enough for a curved narrowboat roof (thinned silicon is quite bendy). Once this is securely bonded down to a rigid roof (typically 4mm steel supported by cross-beams) it effectively becomes an integral part of the roof structure with negligible movement even when walked on -- but for this to work there have to be absolutely no voids or gaps between the panel and the roof, this has to be completely filled with glue, hence the use of vacuum sealing to pull the panel down onto the roof until the glue dries.

 

Do all this (almost impossible for DIY) and the result will be long-lasting. Cut any corners or use more flexible panels (which is what most people do) and it won't be.

You do realise both myself and Matty know a bit about boats and panels….but obviously you are the expert….🙄

[beerbeerbeerbeerbeer]

4 hours ago, frangar said:

I’m really happy with my CIGS flexi panels. They work really well on cloudy days too. They are designed for metal seam roofs on buildings so can put up with high surface heat…they also have a bitumen adhesive backing so hopefully seal better against water underneath…been fitted 18 months so far with no issues. I will admit they were more expensive than rigid panels but being long and thin fit my roof space well. I also didn’t want the boat to look like a floating solar farm! 

For what it’s worth I went for flexi panel too.  Dunno if it’s CIGS or not 🤷‍♀️
 

Like you I wanted something unobtrusive. Didn’t want anything to trip up over, catch bridges or look ugly.  Mine’s been on the roof for 3 years now and I haven’t noticed any deterioration in either it’s output or physical well being.
I took it off a year ago to inspect underneath and there were just dirty water marks which wiped off with a cloth. 
 
It’s a Baird 175W, think it cost £180. 
 

Perhaps a rigid panel that tilts is more productive but can’t be arsed with the hassle. Faffing with movable panels is a waste of drinking time. 

Edited December 3, 2021 by Goliath