Solar panels: stick down or rigid?

[gabble]

I’ve tried both flexible and rigid solar panels. Both have been ‘ok’. I like a traditional looking boat as much as possible so the angled panels don’t really appeal. But I can see why people have them, particularly with the yield benefits from angling.

 

So, do I reinstall some pretty discreet rigid panels close to roof, or invest in some adhesive-to-the-roof flexible jobbies. 
 

Any experience of the durability of the stuck down kind as fitted to the electric boats? Roof rust? What happens when you need to paint?

I have a vague idea rigid panels will help with heat in the summer. Nonsense?

 

gabble

 

[Mike Coombes]

I have made up mountings and fitted a 400W solar array on our last boat, a 12.5 metre Motorsailer. Five years use no problems whatsoever. The pic shows the 1 metre square 200W panels fitted on 3 inch tube risers on the Pilot House roof. They experienced gusts in excess of 90 MPH on occasion. M6 S/S cap screws, penny washers with the tube made from 'speedfit' plumbing tube. The two panels can be clearly seen behind the dinghy which is stored on the Pilot House roof. Click to expand the pic.

 

Last week I drilled and tapped 12 M5 threaded holes to affix two 200W flexible panels to the roof of our narrowboat.They will be screwed down onto 3mm x 12mm butyl tape, the screws sealed with the same stuff. Never had Butyl tape sealing fail yet, but never used it over such long edges.

 

As you point out, aestetics has its cap in the ring.

 

If they require coming off, six security screws on each panel, quick release cable connectors and butyl tape edge seals.  Butyl tape is not an adhesive, so they will come off easily should the roof require attention. Residue cleans off wth White Spirit.

 

On a leisure narrowboat with a nice shape, flexible for me!

[hoopdriver]

I have the stick down panels - 4 x 150w - and they’ve worked very well for me so far. They are three years old and no issues at all. I know that angled ones get better yield but I’ve not really suffered - these charge my 330ah lithium battery just fine. And I do like the aesthetics. For me, definitely worth it

[Tony Brooks]

1 hour ago, gabble said:

I’ve tried both flexible and rigid solar panels. Both have been ‘ok’. I like a traditional looking boat as much as possible so the angled panels don’t really appeal. But I can see why people have them, particularly with the yield benefits from angling.

 

 

I think this is debatable for year round use. On overcast days it is said that flat panels give better yields than angles ones because it uses light scattered from the clouds and that tends to come in random directions. In any case to maximise the output the angle of elevation needs to change by the hour throughout daylight and also the angle across the roof to track the sun. I think we have/had members who have tested both flat and angled and concluded the angling is not really worth it for much of the time.

[David Mack]

21 minutes ago, Tony Brooks said:

In any case to maximise the output the angle of elevation needs to change by the hour throughout daylight and also the angle across the roof to track the sun.

Depending on the orientation of the boat, you may need to vary the orientation of the panels along the roof, and not all variable angle mounts allow this.

[IanD]

21 hours ago, gabble said:

I’ve tried both flexible and rigid solar panels. Both have been ‘ok’. I like a traditional looking boat as much as possible so the angled panels don’t really appeal. But I can see why people have them, particularly with the yield benefits from angling.

 

So, do I reinstall some pretty discreet rigid panels close to roof, or invest in some adhesive-to-the-roof flexible jobbies. 
 

Any experience of the durability of the stuck down kind as fitted to the electric boats? Roof rust? What happens when you need to paint?

I have a vague idea rigid panels will help with heat in the summer. Nonsense?

 

gabble

 

I have the bonded-down 160W semi-flexible panels (x13, properly fitted) on a series hybrid boat, and they started to delaminate during the second winter -- I know several other boats have had the same problem, including from other boatbuilders. OTOH some people have reported no such problems even after 5 years, so this may be a batch problem.

 

However though the supplier will supply FOC replacements under guarantee (3 years at purchase) they will only guarantee the replacement panels for 12 months... 😞 

 

On the principle of once bitten twice shy (plus the lousy guarantee) I'm going to get them swapped for rigid*** panels, which is a major PITA (the boat has to go back to the boatyard) and means the roof will no longer be walkable on -- which TBH I've only done a few times since getting the boat in 2023, so I'm willing to give this up to remove the chance of future panel failures.

 

*** two rows of 1050mm x 580mm 120W panels (9 down each side of the roof) to avoid the protruding flat panel eyesore... 😉 

[wakey_wake]

3 minutes ago, IanD said:

[...] I'm going to get them swapped for rigid*** panels, which is a major PITA (the boat has to go back to the boatyard) and means the roof will no longer be walkable on -- which TBH I've only done a few times since getting the boat in 2023, so I'm willing to give this up to remove the chance of future panel failures.

 

I always thought running erm striding carefully across the roof was an essential part of narrowboating?

Isn't all that lovely open space on a widebeam useful for something?

 

The puzzle of whether to lay mine width-ways with gaps to hop over, or lengthways with a gangway up the side, is partly why I still only have one or two (flexible) on taxi-magnets.

 

22 minutes ago, IanD said:

they started to delaminate during the second winter -- I know several other boats have had the same problem, including from other boatbuilders. OTOH some people have reported no such problems even after 5 years, so this may be a batch problem.

 

Seems like one should assume solar panels may need replacement before the paint does.

[IanD]

19 minutes ago, wakey_wake said:

 

I always thought running erm striding carefully across the roof was an essential part of narrowboating?

Isn't all that lovely open space on a widebeam useful for something?

 

The puzzle of whether to lay mine width-ways with gaps to hop over, or lengthways with a gangway up the side, is partly why I still only have one or two (flexible) on taxi-magnets.

 

 

Seems like one should assume solar panels may need replacement before the paint does.

When the boat was built I got crosswalks a couple of feet wide left between the panels at bow, centre and stern, but the only one that ever really got used was the stern one (which will still be there). The semi-flexible panels were also walkable on along the roof, but I've only done that a handful of times. So having very rarely used this facility in practice I'm not too worried about losing it... 😉 

 

(I have climbed up onto the roof at the stern a few times to get to a lock ladder, but since the rigid panels will be well in front of the slide this will still be possible)

 

[blackrose]

On my boat on sunny winter days, angling panels towards the sun produces 3x the yield of flat panels.

 

But I don't really understand the OP's question in its entirety? Rigid vs flexible I understand and I'd go for rigid. Ask Ian D. He used to swear by flexible panels but recently said they weren't performing and changed his mind. 

 

Unless I misread it, the second part of the OP's question seemed to be debating flat panels vs angled? Well my answer is both: flat in summer, angled in winter when the sun is out. 

 

 

[Ian_C]

23 hours ago, gabble said:

I’ve tried both flexible and rigid solar panels. Both have been ‘ok’. I like a traditional looking boat as much as possible so the angled panels don’t really appeal. But I can see why people have them, particularly with the yield benefits from angling.

 

So, do I reinstall some pretty discreet rigid panels close to roof, or invest in some adhesive-to-the-roof flexible jobbies. 
 

Any experience of the durability of the stuck down kind as fitted to the electric boats? Roof rust? What happens when you need to paint?

I have a vague idea rigid panels will help with heat in the summer. Nonsense?

 

gabble

 

Has anyone considered mounting solar panels on the sloping sides of the boat leaving the roof clear for other uses, I realise the electrical output would be reduced but does anyone have an idea of how much the reduction would be?

[blackrose]

1 minute ago, Ian_C said:

Has anyone considered mounting solar panels on the sloping sides of the boat leaving the roof clear for other uses, I realise the electrical output would be reduced but does anyone have an idea of how much the reduction would be?

 

There was a discussion on that topic a couple of years ago. On sunny winter days assuming that side of the boat was perpendicular to the sun the yield would be good, but in spring and summer it would be a crap apart from mornings and evenings maybe.

[Ian_C]

16 minutes ago, blackrose said:

 

There was a discussion on that topic a couple of years ago. On sunny winter days assuming that side of the boat was perpendicular to the sun the yield would be good, but in spring and summer it would be a crap apart from mornings and evenings maybe.

Thank you for your observation, I guess that winter time is when good yield is invaluable so perhaps a mixture of roof and wall mountings would suit.

[wakey_wake]

5 minutes ago, Ian_C said:

Has anyone considered mounting solar panels on the sloping sides of the boat leaving the roof clear for other uses, I realise the electrical output would be reduced but does anyone have an idea of how much the reduction would be?

Yes I've done that, but (as above) temporarily with taxi magnets. This was for a short stay, and I was trying to eke out what sun there was to avoid burning diesel.

 

In midwinter when it's not cloudy, it may be the best yield available for most of the day.

By the time solar is actually useful in the season, that early gain is probably insignificant?

 

There are websites which will make these predictions but I've not tried them.

 

This January gone, I could have really benefited from 3x 130W on the side and not bothered with any horizontal. (Boat pointing North)

When it comes to installing some bolt holes I may well put some in both sides as well as the roof, but first I want a nice dome-head bolt + waterproof washer solution to fill the holes and not protrude much.

 

The idea of drilling holes in a nice waterproof superstructure does not sit well with me. 🐔

Don't ask me to cut a fishing hole in the baseplate, like the folks with huts on the ice do. 🤣

 

 

18 minutes ago, blackrose said:

On my boat on sunny winter days, angling panels towards the sun produces 3x the yield of flat panels.

[...]

Well my answer is both: flat in summer, angled in winter when the sun is out. 

I also concluded there are two modes for solar panel arrangement -

 

When I am on the boat, I want optimum harvest. I'm around to adjust for prevailing weather, whether to adjust sun tracking angle during the day or lash things down for wind.

 

Otherwise, flat is safer and I'm grateful for the 5~10% of nominal panel output. It keeps the power budget positive.

 

~~~ join?

 

42 minutes ago, blackrose said:

 

Are the black stoppers some special PV mounting widget that came with the kit and attach to the roof, or just a nice matched set of door stoppers that you push into place for flat mode?

 

Also when the wind rattles the panels, do the steel pins damage the aluminium? I would have wanted faying surface bolted together, but hinge pins are surely easier.

[Rob-M]

14 hours ago, IanD said:

When the boat was built I got crosswalks a couple of feet wide left between the panels at bow, centre and stern, but the only one that ever really got used was the stern one (which will still be there). The semi-flexible panels were also walkable on along the roof, but I've only done that a handful of times. So having very rarely used this facility in practice I'm not too worried about losing it... 😉 

 

(I have climbed up onto the roof at the stern a few times to get to a lock ladder, but since the rigid panels will be well in front of the slide this will still be possible)

 

Don't single hand to Stone, one of the locks the ladder is near the top gate so I couldn't get to it from the roof of our boat even though we only have two panels on the front half of the roof.  I had to through the centre line up and then  reverse part way out of the lock to get off the boat and pull it back in to the lock.

[Mike Todd]

Much depends on what you want from solar panels on the boat. If your aim is to be as off grid as possible then the maximum number, regardless of appearance and roof space usage, is the way to go. I have seen extreme cases with panels covering almost all of the roof as well as the cab sides.

 

Unless you are prepared to compromise conventional appearance to this degree then solar is unlikely to eliminate the need of alternate energy sources for heating, including cooking and hot water. For those who mainly cruise daily and/or moor away from habitation, then the main engine or separate generator is mandatory.

 

However, on both our present boat (9 years old now) and its predecessor (9 years with us) we have had a couple of surface mounted panels which were/are mainly aimed at a kind of trickle charger to keep batteries topped up when boat unattended (However much you switch demands off there should always be a chance for the bilge pump to activate and usually in circumstances where a flat battery would be highly unwelcome)

 

In both cases the decision to surface mount was based on our boating habits which make extensive se of the roof, mainly around locks. As one of us grew less able to work lock paddles with total confidence, it was important to us that if I was the steerer then I could exit from an empty lock to help out. This meant using the roof to access the (modern) ladders - I have never been agile enough to leap up onto the lock edge from a roof - but admire those who can! We also bult in a suitable step (one convenient to use up and down) to get from stern deck to roof. 

 

Last year, 'tother one broke an arm early in the season and whilst it was still mending the ability to almost single-hand was invaluable - initially she was only able to contribute steering a boat from the lock landing into the lock and vice versa.

 

At this stage I do not yet know how our previous strategy (smallish surface mounted panels) might be impacted with a different battery technology offering larger capacity, but I suspect we would still prioritise the 'top up' faunctionality.

 

When we had Alchemy re-painted a could of years ago, the boatyard found that they could not remove the original panels intact (I am unsure of just how they were secured in position but I think it was a combination of pop rivets and strong sealant/adhesive. In any event, replacements were needed.

 

Bottom line - as always, it is first important to determine what you want to achieve as a good solution for one may be quite wrong for anther.

[Up-Side-Down]

When I installed my four 440W rigid, bi-facial panels on the roof of my narrowboat, I wired panels 1 & 3 through one Victron MPPT controller and panels 2 & 4 through another identical controller. This was so that I could conduct a series of comparative trials, like for like.

 

In comparing angled and flat mounted panels, the angled panels had a 7.4% increased output over the flat ones. I used the theoretical ideal angle for my Edinburgh latitude.

 

I also compared panel output from a pair angled at the theoretical ideal angle against a pair angled at a stupid angle and found that the ideal angle produced a 6.2%  improvement.

 

These trials were conducted over three month periods and the only comment I would add is that, being in Scotland, my solar gain is probably far more reliant on indirect sunlight than, say, a boat moored on the K&A. 

 

[Mike Coombes]

3 hours ago, Mike Todd said:

Much depends on what you want from solar panels on the boat. If your aim is to be as off grid as possible then the maximum number, regardless of appearance and roof space usage, is the way to go. I have seen extreme cases with panels covering almost all of the roof as well as the cab sides.

 

Unless you are prepared to compromise conventional appearance to this degree then solar is unlikely to eliminate the need of alternate energy sources for heating, including cooking and hot water. For those who mainly cruise daily and/or moor away from habitation, then the main engine or separate generator is mandatory.

 

However, on both our present boat (9 years old now) and its predecessor (9 years with us) we have had a couple of surface mounted panels which were/are mainly aimed at a kind of trickle charger to keep batteries topped up when boat unattended (However much you switch demands off there should always be a chance for the bilge pump to activate and usually in circumstances where a flat battery would be highly unwelcome)

 

In both cases the decision to surface mount was based on our boating habits which make extensive se of the roof, mainly around locks. As one of us grew less able to work lock paddles with total confidence, it was important to us that if I was the steerer then I could exit from an empty lock to help out. This meant using the roof to access the (modern) ladders - I have never been agile enough to leap up onto the lock edge from a roof - but admire those who can! We also bult in a suitable step (one convenient to use up and down) to get from stern deck to roof. 

 

Last year, 'tother one broke an arm early in the season and whilst it was still mending the ability to almost single-hand was invaluable - initially she was only able to contribute steering a boat from the lock landing into the lock and vice versa.

 

At this stage I do not yet know how our previous strategy (smallish surface mounted panels) might be impacted with a different battery technology offering larger capacity, but I suspect we would still prioritise the 'top up' faunctionality.

 

When we had Alchemy re-painted a could of years ago, the boatyard found that they could not remove the original panels intact (I am unsure of just how they were secured in position but I think it was a combination of pop rivets and strong sealant/adhesive. In any event, replacements were needed.

 

Bottom line - as always, it is first important to determine what you want to achieve as a good solution for one may be quite wrong for anther.

 

My experience of 5 seasons on a 12.5 metre Motorsailer with 400W of rigid solar proved conclusively that while on board the Solar kept the 440AH House Bank able to run two fridges-big ones, but keel cooled, so more efficient-a Dometic 40 litre freezer box 24/7, may through September in the British Isles. We were often aboard 4-5 months at a time. The batteries were high quality 'Lifeline' spiral wound AGM's. We had a Westerbeke 8KW Genset. This was rarely used once we had the Solar and Inverter, mostly for heating the calorifier for the morning shower.

 

I am in the process of fitting 400W of flexible solar panels to our narrowboat. I hope that this will keep the fridge and Dometic freezerbox going this summer.

 

We have a Bluetti 180 as a high power source, so wont be taking much through the inverter for things like the toaster, flat grill and electric kettle.

 

This recharges quickly and has proved a good investment so far.

 

As far as your comment re fixing goes, I have drilled and tapped the roof M5 for the six reinforced holes in each panel. Security screws, penny washers and butyl tape will seal these screws, Butyl tape will be used all around the edges of the panels to -hopefully-stop water getting under them. Butyl tape has not failed me as an effective and reliable sealer yet, even in places where green water was regularly taken aboard when well offshore in heavy conditions. Remember, a cubic metre of water weighs one ton and has a great penetrating effect when sailing at five knots!

[wakey_wake]

6 hours ago, Mike Todd said:

Much depends on what you want from solar panels on the boat. If your aim is to be as off grid as possible then the maximum number, regardless of appearance and roof space usage, is the way to go. I have seen extreme cases with panels covering almost all of the roof as well as the cab sides.

This sounds remarkably similar to my "two modes - when I'm onboard and when I'm not" 😁 except that while I had a perpetual shoreline, I could find more urgent things to do than batteries and solar charging; except while I fretted that someone else would trip the upstream breaker and not reset it for me.

 

 

7 hours ago, Mike Todd said:

[...] I could exit from an empty lock to help out. This meant using the roof to access the (modern) ladders - I have never been agile enough to leap up onto the lock edge from a roof - but admire those who can! We also bult in a suitable step (one convenient to use up and down) to get from stern deck to roof. 

Leaping in locks, especially single-handed, seems like a high risk activity. I do scamper more than some people, but it has to be at the front of one's mind: if you miss the boat, there is nobody to pull you out and you will probably die trapped between boat and lock wall. 😬

 

I find it easy to mount the roof from the gunnel, but dismounting safely is much harder. Improved arm strength may be the answer here?

At the stern it's easy both ways, via the open sliding hatch or with the tiller bar as support.

From the welldeck I almost never access the roof either way because the canopy is in the way. I would appreciate photos of designs that make it easier.

 

There are flip-out steps fore and aft but they're only good for making bruises and holes in trousers 😞 so I don't use them.

@Mike Todd I would appreciate a photo of your stern deck step so I can steal the idea.

 

 

Back to solar,

 

I haven't measured in really heavy overcast (as in threatening rain) but my impression is that whole-sky overcast will give 10% of panel rated power but a little less if correctly angle to the sun. Presumably because by tilting, you miss out on the dull glare of clouds on the far side of the sky.

 

If I calculate for being "as off grid as possible" then I might reach 10 months/year by covering the boat, but that doesn't mean it's a sensible choice for me.

 

7 hours ago, Mike Todd said:

Bottom line - as always, it is first important to determine what you want to achieve as a good solution for one may be quite wrong for anther.

 

To some extent, "what I want to achieve" includes admitting that I don't know. 🤔

Therefore not making sweeping commitments of roof to more immovable objects, but preferring to make some M5 to M8 sized tappings or Rivkle® rivet nut inserts... without allowing water to seep in or to pool and freeze, and without making the kit more stealable.

 

Currently I'm thinking of through-holes, dome-heads and securing inside with a pair of locknuts. This would require cutting many holes in the lovely T&G cabin panels 😢 so I will start small.

 

 

5 hours ago, Up-Side-Down said:

[...] This was so that I could conduct a series of comparative trials, like for like.

 

I award 10 science points! 🥼 Redeemable at all good laboratories for not very much at all.

 

5 hours ago, Up-Side-Down said:

[...] being in Scotland, my solar gain is probably far more reliant on indirect sunlight than, say, a boat moored on [...]

 

I suspect that part of the value of panel on the cabin sides is to gather that indirect light during parts of the day when other panels have not yet woken up, or already gone to sleep. Another aspect of cabin-side panels is that they don't obstruct roof access, though to starboard they may catch more tree damage.

 

In this respect, I am leveraging the idea that flexible solar panels are cheaper than any kind of tracking mount,

i.e. instead of tracking the sun, just take what's available from any panel that can see it.

This logic leads to a boat plastered in semi-disposable dark blue rectangles...

 

4 hours ago, Mike Coombes said:

[...] with 400W of rigid solar proved conclusively that while on board the Solar kept [...]  two fridges-big ones, but keel cooled, so more efficient

 

Last I looked, fridges other than standalone mains seemed prohibitively expensive.

Is there a source or shortcut (noting legalities of f-gases) for heat pump units from cabinet to baseplate?

 

4 hours ago, Mike Coombes said:

We have a Bluetti 180 as a high power source, so wont be taking much through the inverter for things like the toaster, flat grill and electric kettle.

This recharges quickly and has proved a good investment so far.

 

I see the value of putting heavy loads on a separate inverter from the main one - I've just popped my 1kW EDECOA. Thread to follow when I get the lid off it.

 

The 3kW kettle is by far the most often used cooking device ☕ but I reduce its power with a Variac. Because I can, not because I would suggest anyone buys one for the purpose. I also have a 600W kettle but I don't like it.

 

Do you recharge the Bluetti directly from PV, perhaps allowing it to compete with another MPPT controller?

Or are you transferring the energy from the domestic bank and paying an extra 10% energy loss?

 

4 hours ago, Mike Coombes said:

As far as your comment re fixing goes, I have drilled and tapped the roof M5 for the six reinforced holes in each panel. Security screws, penny washers and butyl tape will seal these screws, Butyl tape will be used all around the edges of the panels to -hopefully-stop water getting under them.

 

Thank you for that.

I agree that butyl is good, I have some sealing a roof hole where I replaced a fitting with a plate + stud, through a bar with a nut on the inside. It worked so well I'm not likely to bother welding a plate in.

 

How do you layer them?

I would expect that the butyl would prevent the screw snugging up properly, or get squeezed out, and therefore it would come loose?

I also have no idea what the pull-out strength of M5 or M8 would be in a tapped 4mm roof. This doesn't fill me with confidence.

 

I was planning to stand the panels off from the roof enough for them to air-dry behind, maybe more like the @blackrose way. I know what water likes to do, so sealing them to the roof seems like a way to trap the water underneath?

[Mike Coombes]

4 hours ago, wakey_wake said:

This sounds remarkably similar to my "two modes - when I'm onboard and when I'm not" 😁 except that while I had a perpetual shoreline, I could find more urgent things to do than batteries and solar charging; except while I fretted that someone else would trip the upstream breaker and not reset it for me.

 

 

Leaping in locks, especially single-handed, seems like a high risk activity. I do scamper more than some people, but it has to be at the front of one's mind: if you miss the boat, there is nobody to pull you out and you will probably die trapped between boat and lock wall. 😬

 

I find it easy to mount the roof from the gunnel, but dismounting safely is much harder. Improved arm strength may be the answer here?

At the stern it's easy both ways, via the open sliding hatch or with the tiller bar as support.

From the welldeck I almost never access the roof either way because the canopy is in the way. I would appreciate photos of designs that make it easier.

 

There are flip-out steps fore and aft but they're only good for making bruises and holes in trousers 😞 so I don't use them.

@Mike Todd I would appreciate a photo of your stern deck step so I can steal the idea.

 

 

Back to solar,

 

I haven't measured in really heavy overcast (as in threatening rain) but my impression is that whole-sky overcast will give 10% of panel rated power but a little less if correctly angle to the sun. Presumably because by tilting, you miss out on the dull glare of clouds on the far side of the sky.

 

If I calculate for being "as off grid as possible" then I might reach 10 months/year by covering the boat, but that doesn't mean it's a sensible choice for me.

 

 

To some extent, "what I want to achieve" includes admitting that I don't know. 🤔

Therefore not making sweeping commitments of roof to more immovable objects, but preferring to make some M5 to M8 sized tappings or Rivkle® rivet nut inserts... without allowing water to seep in or to pool and freeze, and without making the kit more stealable.

 

Currently I'm thinking of through-holes, dome-heads and securing inside with a pair of locknuts. This would require cutting many holes in the lovely T&G cabin panels 😢 so I will start small.

 

 

 

I award 10 science points! 🥼 Redeemable at all good laboratories for not very much at all.

 

 

I suspect that part of the value of panel on the cabin sides is to gather that indirect light during parts of the day when other panels have not yet woken up, or already gone to sleep. Another aspect of cabin-side panels is that they don't obstruct roof access, though to starboard they may catch more tree damage.

 

In this respect, I am leveraging the idea that flexible solar panels are cheaper than any kind of tracking mount,

i.e. instead of tracking the sun, just take what's available from any panel that can see it.

This logic leads to a boat plastered in semi-disposable dark blue rectangles...

 

 

Last I looked, fridges other than standalone mains seemed prohibitively expensive.

Is there a source or shortcut (noting legalities of f-gases) for heat pump units from cabinet to baseplate?

 

 

I see the value of putting heavy loads on a separate inverter from the main one - I've just popped my 1kW EDECOA. Thread to follow when I get the lid off it.

 

The 3kW kettle is by far the most often used cooking device ☕ but I reduce its power with a Variac. Because I can, not because I would suggest anyone buys one for the purpose. I also have a 600W kettle but I don't like it.

 

Do you recharge the Bluetti directly from PV, perhaps allowing it to compete with another MPPT controller?

Or are you transferring the energy from the domestic bank and paying an extra 10% energy loss?

 

 

Thank you for that.

I agree that butyl is good, I have some sealing a roof hole where I replaced a fitting with a plate + stud, through a bar with a nut on the inside. It worked so well I'm not likely to bother welding a plate in.

 

How do you layer them?

I would expect that the butyl would prevent the screw snugging up properly, or get squeezed out, and therefore it would come loose?

I also have no idea what the pull-out strength of M5 or M8 would be in a tapped 4mm roof. This doesn't fill me with confidence.

 

I was planning to stand the panels off from the roof enough for them to air-dry behind, maybe more like the @blackrose way. I know what water likes to do, so sealing them to the roof seems like a way to trap the water underneath?

 

So far I have only charged the Bluetti through a 12v source with the main engine running for propulsion purposes, so no issues there. Once the Solar is installed I suspect, for convenience, I will continue the same regime.

 

As far as the panel fixing goes, my recently purchased panels have six reinforced holes, two at each end and two in the centre. I purchased a 10 metre length of 3x12mm black butyl tape. This will be placed along each long side edge and the ends in one continuous length, turning inside the mounting holes with a little extra piece making a circle around each hole. The torx security screws will be sealed with the butyl tape too. The butyl must be tight enough to hold the panels securely, but not so much the panels are distorted and squeeze the tape out. My roof is 5mm and the fixing holes were made with good tools and are adequate for the task. I have no reservations about my method of fixing and sealing from past experience, but a truism I use a lot is "True knowlege is the product of direct experience" so I reserve the right to let you know in future if it proves unsuccessful!

 

Refrigeration on serious yachts is far in advance of inland waterway vessels. Most, for efficiency, are keel cooled, extremely well insulated and are top loaders so the cold air does not escape when opened. Many have remote units made by Frigo boat or Adler Barbour and others. This allows the freezer plate to be fitted in a good place in the insulated box. As one would expect when cruising in out of the way places where supplies are hard to get, keeping food for extended periods is essential.

[IanD]

For an example of what can go wrong with semi-flexible panels, here are pictures I took this morning of two boats built by the same builder in the same year (2023) with two different batches of the same panels from the same supplier.

 

The delamination is obviously a manufacturing fault, almost certainly some failure in process/quality control. I have been told that other boats and boatbuilders have also sometimes seen the same problem with these panels, which suggests it was *not* a one-off problem with one batch.  The problem is not even an entire bad batch, I have 13 panels all from the same batch (adjacent serial numbers), 2 are absolutely fine (like the first picture) and 11 have completely delaminated, the top protective film has lost adhesion and can be simply lifted off, as my hand shows... 😞 

 

OTOH I also know there are boaters out there with the same panels on boats more than 5 years old with no problems (and the other boat I photographed) -- and also boaters who have had similar delamination problems. I'm not willing to trust that the manufacturer has found out what the problem is (I believe they deny that one exists) and has fixed it (especially since they're only offering a 12 month warranty on replacements), and don't want to re-enter the good/bad panel lottery -- so am going to replace them with rigid panels even though this is a major PITA.

 

Edited March 27 by IanD

[Cheshire cat]

That looks like an attack of the giant slugs!

 

Have you previously named the manufacturer of the panels? I'm expecting to have to replace my ten year old panels when the boat is repainted next year.

[b00ke23]

13 minutes ago, IanD said:

For an example of what can go wrong with semi-flexible panels, here are pictures I took this morning of two boats built by the same builder in the same year (2023) with two different batches of the same panels from the same supplier.

 

The delamination is obviously a manufacturing fault, almost certainly some failure in process/quality control. I have been told that other boats and boatbuilders have also seen the same problem with these panels, which suggests it was *not* a one-off problem with one batch.  The problem is not even an entire bad batch, I have 13 panels all from the same batch (adjacent serial numbers), 2 are absolutely fine (like the first picture) and 11 have completely delaminated, the top protective film has lost adhesion and can be simply lifted off, as my hand shows... 😞 

 

OTOH I also know there are boaters out there with the same panels on boats more than 5 years old with no problems (and the other boat I photographed) -- and also boaters who have had similar delamination problems. I'm not willing to trust that the manufacturer has found out what the problem is (I believe they deny that one exists) and has fixed it (especially since they're only offering a 12 month warranty on replacements), and don't want to re-enter the good/bad panel lottery -- so am going to replace them with rigid panels even though this is a major PITA.

 

 

Not good. Are there any other Manufacturers of flat panels? 

[IanD]

14 minutes ago, Cheshire cat said:

That looks like an attack of the giant slugs!

 

Have you previously named the manufacturer of the panels? I'm expecting to have to replace my ten year old panels when the boat is repainted next year.

I don't know who the actual manufacturer/UK supplier is, but these are the panels -- multiple boatbuilders use them since they're a perfect size to fit across a narrowboat roof, are easy to mount and look good, and are supposed to be durable (see blurb below):

 

https://www.photonicuniverse.com/en/catalog/full/1144-160W-black-semi-flexible-fibreglass-solar-panel-with-round-rear-junction-box-and-3m-cable-with-durable-ETFE-coating.html

 

They have a 3-year warranty, but are only offering a 12-month warranty on replacement panels which doesn't exactly fill me with confidence... 😞 

 

First winter -- no failures. Second winter -- 5 bad panels with some delamination around the edges, 8 still good. Third winter -- 11 bad panels with delamination across the entire area, 2 still good... 😞 

 

7 minutes ago, b00ke23 said:

 

Not good. Are there any other Manufacturers of flat panels? 

Yes, but different sizes and won't drop-in as a replacement, there are holes cut in the roof for the rear junction boxes... 😞 

Edited March 27 by IanD

[Mike Coombes]

mmmm - I will let the forum know if I get any problems. I chose my ones after reccomendation from a fellow sailor who has used the same supplier, albeit for smaller panels, for his yacht with no issues. He walks on his too, something I shall not do.

[IanD]

6 minutes ago, Mike Coombes said:

mmmm - I will let the forum know if I get any problems. I chose my ones after reccomendation from a fellow sailor who has used the same supplier, albeit for smaller panels, for his yacht with no issues. He walks on his too, something I shall not do.

Walking on them doesn't seem to cause any problems, at least if they're securely bonded down to a nice rigid steel roof (and you're not wearing high heels or hobnailed boots...).

 

Mine were great for the first year, then the problems started to appear, then they fell apart last winter... 😞