For North Europe / UK - Solar panel to maintain house bank with fridge unit.

[Refueler]

Portable panels are all very well, but to top up a battery after a sail, you need panels fitted when you've gone home.
Also, we do catch some power while sailing in overcast, even drizzle conditions.
Our fixed panel was working while beating into 20knots true yesterday.
Also you need to consider where the wiring will run.
The other thing is, we don't really have great storage space for temporary panels.
We don't want something to fff with on sunny days, we want a permanently fitted solution that's working as best it can by default.

Agree ... of course best if fixed etc.

But I am considering also - many feet around the deck when racing the boat .. as well as keeping things clear ...

When shes tied up .. I don't think using portable would be a problem. A folding set could easily be rigged across the deck in front of mast or over the boom. Pal of mine has fixed his flexi to the top surface of his sprayhood ...

 

[lustyd]

Portable panels are all very well, but to top up a battery after a sail, you need panels fitted when you've gone home.

Being portable doesn't stop them remaining fitted. Ours usually live on the coachroof, but when at anchor I often move them about for better sunshine and have MC4 extension leads for this purpose. You can't see in the picture easily but they have strips of UPVC window cloaking attached with plastic clips along the sides which prevent too much bending. The Renogy panels have holes along them which were perfect for this mounting, and then the end holes just have 5mm bungee with hooks at the end to secure the panels. Originally this was going to be temporary but it's turned out to be so useful I'm keeping the setup. I can mount them on the side of the boom, guardrails, foredeck, coachroof or pushpit/swim platform depending on sun.

 

[Refueler]

Lustyd ... exactly what I was thinking .... just because portable - does not mean any problem.

I'm looking at maybe like this - with built in stand :

100W 12V faltbares tragbares solarpanel für Powerstation Wohnmobil Camping | eBay

or as you have flexi panel with fixing holes ...

 

[dunedin]

……

However, your project needs a realistic approach to achieve its goals. I think you will be surprised how much impact the shadow of the boom and sails will have on the overall output for a solar panel on the companionway hatch. Even the tiny shadows from the two sheets shown in post # 12 will have a noticeable effect. This is especially true in the areas you plan to sail. These locations have long solar days resulting in a reasonable total solar output, but the sun angle is relatively low. This exaggerates the size of shadows. Hopefully, you can push these shadow sources out of the way at anchor, but when sailing the effect will be significant.

……….

Is this view of minor shadows based upon actual measurements or on assumption?
I must admit I have not specifically measured the loss of power from the shadow of a sheet, but equally our panels on the sprayhood plus roving panel seem to work fine without being paranoid about tiny shadows.
Wiring in parallel rather than serial helps. And we tend to move the boom to one side to reduce the huge shadow of the boom and stackpack, which otherwise would be an issue. But otherwise we just leave the long days up North to do their work - and of course cooler air is better for solar panels.

 

[lustyd]

Is this view of minor shadows based upon actual measurements or on assumption?

It's a well known solar panel issue. A small shadow on one cell will effectively remove the string from operation. It's why there are two bypass diodes on most panels, so that you generally only lose half a panel.

 

[dunedin]

It's a well known solar panel issue. A small shadow on one cell will effectively remove the string from operation. It's why there are two bypass diodes on most panels, so that you generally only lose half a panel.

Well known in theory, and certainly for large areas of shadow, but with quality panels have never noticed something as small as a sheet (the rope type!) impacting output in practice, as one poster implied.

 

[lustyd]

We certainly get a drop if a rope shadows in a certain way. If it's raised away from the panel it doesn't drop as much, but it will drop since every cell outputs the same as the lowest one in the string. Any hard shade directly against the panel will effectively drop the string of cells being shaded, so . It's not a quality thing so much as a type of shade kind of thing.

 

[noelex]

Is this view of minor shadows based upon actual measurements or on assumption?
I must admit I have not specifically measured the loss of power from the shadow of a sheet, but equally our panels on the sprayhood plus roving panel seem to work fine without being paranoid about tiny shadows.
Wiring in parallel rather than serial helps. And we tend to move the boom to one side to reduce the huge shadow of the boom and stackpack, which otherwise would be an issue. But otherwise we just leave the long days up North to do their work - and of course cooler air is better for solar panels.

Shadows are unavoidable on a yacht, but they have more effect on the output than you would assume from the percentage area.

This does not mean you cannot harvest useful output from panels subject to shadowing, but when estimating the likely output, the amount and type of shadow needs to be taken into account as an important factor. This is especially true in the OP’s case as he is considering installing a panel on the companionway hatch.

As you point out, parallel is better than series connection, but best of all, especially if the panels are subject to shadowing or disparate conditions, is one controller per panel. This allows the maximium power point to be adjusted for each panel rather than relying on an compromise. The biggest drawback for most boats is greater wiring complexity and cost. This means it is not always the sensible choice.

I did a quick experiment placing two ropes above our port panel (the central and starboard panels acting as a control) in a similar orientation to the photo in post# 12 . The sun was still reasonably low at this stage. As you can see, the effect is noticeable, at least where you can compare the output to otherwise identical, but unshaded panels.

Don’t be too focused on the exact difference in this case. This is only one example. The results will vary considerably depending on where the shadows fall in relation to the bypass diodes, how big the shadow is in relation to the size of the panel, and if the panel is receiving direct or diffuse sunlight, to name just a few factors. Nevertheless, even a relatively small amount of shadowing does have some impact.

 

[lustyd]

parallel is better than series connection

This is very outdated advice. Panels have bypass diodes for this reason and serial will generally work better since the voltage is more likely to remain high enough to be converted to a charge. If you have a ~18V panel and one string is out then it runs only at ~9V which isn't enough to do anything in an MPPT. If you have two panels in serial and one is shaded you end up with 27V which is still plenty for charging through an MPPT. If both panels are partially shaded with serial you'll have 18V but with parallel you'll have 9V.

 

[dunedin]

Shadows are unavoidable on a yacht, but they have more effect on the output than you would assume from the percentage area.

This does not mean you cannot harvest useful output from panels subject to shadowing, but when estimating the likely output, the amount and type of shadow needs to be taken into account. This is especially true in the OP’s case as he is considering installing a panel on the companionway hatch.

As you point out, parallel is better than series connection, but best of all, especially if the panels are subject to shadowing or disparate conditions, is one controller per panel. This allows the maximium power point to be adjusted for each panel rather than relying on an compromise. The biggest drawback for most boats is greater wiring complexity.

I did a quick experiment placing two ropes above our port panel (the central and starboard panels acting as a control) in a similar orientation to the photo in post# 12 . The sun was still reasonably low at this stage. As you can see, the effect is noticeable, at least where you can compare the output to otherwise identical, but unshaded panels.

Don’t be too focused on the exact difference in this case. This is only one example. The results will vary considerably depending on where the shadows fall in relation to the bypass diodes, how big the shadow is in relation to the size of the panel, and if the panel is receiving direct or diffuse sunlight, to name just a few factors. Nevertheless, even a relatively small amount of shadowing does have some impact.
View attachment 179431

Thanks, interesting test. So yes a rope shadow does cause a noticeable difference. On the other hand the panel output is still 80% of the unobstructed ones. So explains my pragmatic view of not stressing and letting the long days make up the charge probably still valid.

 

[noelex]

If you have a ~18V panel and one string is out then it runs only at ~9V which isn't enough to do anything in an MPPT. If you have two panels in serial and one is shaded you end up with 27V which is still plenty for charging through an MPPT. If both panels are partially shaded with serial you'll have 18V but with parallel you'll have 9V.

You are correct (assuming ”12v panels”and strictly speaking you should include the voltage drop over the bypass diodes), but this is just one example where the current is near identical for both panels. Where series does particularly badly is if there is a current mismatch such as diffuse shadow over one panel. With series connection the current has to be identical throughout the circuit, so in this case the lower current produced by the panel in shade reduces the current of the panel in full sun. This does not happen with a parallel connection.

The bottom line is that mathematical modelling of series versus parallel connection is complex. It depends significantly on the location of the shadows in relation to the bypass diodes and both the extent and type of shadowing. You cannot draw a conclusion from a single example. In some situations series does best and in others parrallel. A weighted mean of all possible scenarios is needed and there is enormous number of permutations.

The best data comes from sailors that have tried both wiring methods. It would be great to have more data on this, but the majority report better total output with parallel connection. This is in contrast to domestic installations where shadows are not usually a factor and the higher voltage produced by series connection matches better with the required 230 or 110 voltage.

If you do decide to use series connection (perhaps because this is the easiest and cheapest system) it is worth adding additional bypass diodes around each panel especially with "12v panels". This is an inexpensive upgrade.

With larger arrays there is also the possibility of series and parallel connection. For example, with four panels two can be wired in series and then two pairs are wired in parallel. The best and worst of both options. However, the highest yield apart from a few unusual cases is with individual controllers for each panel. This is not always practical, but in some cases the cost is no greater than parallel connection so it is an option that is worth exploring, especially as it also provides valuable redundancy.

 

[Refueler]

'individual controllers for each panel'

But surely they will then be paralleled into the battery bank ... would not one controller cause others to default out as they see high voltage ?

 

[noelex]

'individual controllers for each panel'

But surely they will then be paralleled into the battery bank ... would not one controller cause others to default out as they see high voltage ?

This is not normally of practical concern. If the battery is kept at the correct charging voltage it does not matter if the output is 50/50 between the two controllers or if the output is 100/0. The battery is receiving the same current in both cases. If the voltage drops below the target voltage then both controllers will always contribute their maximum possible output.

There can occasionally be conflicts where the absorption time is counted down on one controller and not the other. This can, on rare occasions, result in slight overcharging. If you have the popular Victron controllers this issue does not occur, as the charging state can be automatically synchronised over Bluetooth.

 

[Refueler]

On my Primor 24 Mobo .. the two panels are connected to each other in parallel down to one controller .... have to check to see if its a dual output or not ....
Boat has two 90 A/Hr Lead Acids individually switched ... but parallel when both switches engaged.

 

[noelex]

On my Primor 24 Mobo .. the two panels are connected to each other in parallel down to one controller .... have to check to see if its a dual output or not ....
Boat has two 90 A/Hr Lead Acids individually switched ... but parallel when both switches engaged.

Parallel connection is a common and successful way to wire solar panels.

There is nothing wrong with this system, but an alternative is to have two smaller controllers, one for each panel. The output of these two controllers is then fed in parallel to the batteries.

The difference between these two systems is not enormous, but the total solar yield is greater with two controllers for most circumstances. This is because each solar panel is kept at its optimum maximum power point for the conditions it is experiencing. A single controller has to pick a compromise maximum power point. The advantage of multiple controllers particularly applies when the panels are sometimes experiencing very different conditions.

 

[B27]

It takes quite a lot of solar to deliver 4A on a grey day, especially if not all that solar is pointing the right way and some of it might be shaded.
so the battery delivers 4A on demand and the solar does what it can to replenish 'as and when' it can.
If you're moored not anchored, you'll be shaded by other boats sometimes, the banks or buildings maybe.
It's really a game of playing the probability, reducing the dependence on the engine.
I think we need enough battery capacity to run the fridge for however long the engine might be not used.
But if our fridge averages 1A on a hot day, then 24Ah of battery devoted to the fridge is not a big ask.

Heatwave conditions last year, my 50W panel probably yielded 30Ah per day in high summer, balancing the fridge as far as I could tell, we spent two days without running the engine and battery state was if anything slightly up afterwards.
Last weekend, more like 10Ah per day, so we were away for two days, the battery should have caught up by now., plus we used the engine for a few hours. With the weather being a bit grey, we chose more sheltered moorings and probably got more shade too.

 

[B27]

Being portable doesn't stop them remaining fitted. Ours usually live on the coachroof, but when at anchor I often move them about for better sunshine and have MC4 extension leads for this purpose. You can't see in the picture easily but they have strips of UPVC window cloaking attached with plastic clips along the sides which prevent too much bending. The Renogy panels have holes along them which were perfect for this mounting, and then the end holes just have 5mm bungee with hooks at the end to secure the panels. Originally this was going to be temporary but it's turned out to be so useful I'm keeping the setup. I can mount them on the side of the boom, guardrails, foredeck, coachroof or pushpit/swim platform depending on sun.

View attachment 179415

Personally, I wouldn't want that on the deck for racing or rough weather.
My boat is smaller so we have less deck area which isn't kind of needed for safe operation of the boat.
So on the grey windy days, such panels would yield zilch, if leaving harbour was on the cards.
For sure, you have a bigger boat, so much more deck area, and probably a higher threshold of what looks like 'rough weather'.

I have played around with extra, flexible panels, but the additional yield has looked disappointing, particularly in £ per Ah, when compared with my £40, 50W panel fixed on top a post at the back of the cockpit. Our number of days aboard per year is not huge, so there's less point throwing hundreds at it. People have to weigh it all up for themselves.

I'm considering a bimini/arch arrangement which would take maybe 150W. But TBH that's partly because I want more shade in the cockpit quite often.

 

[NBs]

Hi,

I have two portable and foldable panels 135W and 100W and a 560Ah lifepo4 battery bank.

The panels peak output is about 11A and often how about 7-8A.

I often have 2-3 days on the panels alone charging the batteries and on a sunny day I can collect more than I use, but on a semi cloudy day the output from the panels is not enough for my consumption, but the batteries fortunately have the capacity to survive several days without charging.

The difference between charging and discharging lead AGM batteries in real life is huge in the Lifepo4 batteries' favour.

My boating area is North Baltic sea...

 

[NBs]

Lustyd ... exactly what I was thinking .... just because portable - does not mean any problem.

I'm looking at maybe like this - with built in stand :

100W 12V faltbares tragbares solarpanel für Powerstation Wohnmobil Camping | eBay

or as you have flexi panel with fixing holes ...

Hi,
I have this panel and it is very handy because it comes with 4 support legs. I have tied about 60cm of 6mm rubber rope to the handles and I can tie it in several places on the boat and even strong winds are not a problem. The panel also produces well vs the price.

 

[Refueler]

Hi,
I have this panel and it is very handy because it comes with 4 support legs. I have tied about 60cm of 6mm rubber rope to the handles and I can tie it in several places on the boat and even strong winds are not a problem. The panel also produces well vs the price.

Thanks for reply ... I am considering two of the panels ... then I have more options ....