how to do solar on a sailboat that has limited space and shading issues @48vnom

[Ohms_Cousin]

I wish to put PV on my sail boat. My Boat/inverter system is 48v (Victron). Because space is very limited on a sail boat I can only manage a total of 4 panels with possibly 2 extra down each side mounted vertically - so if did that it would be 8 panels in total - (but not sure if that is a good idea or not to side mount like that - some do it, others say avoid it).

The issue is I dont want to run the string in series due to shading issues (boom/mast/rigging wires/sails when under way). Parallel is not much use to me in this scenario as I need to get the voltage at least 5v above battery voltage which in this case is 61v min (battery is 56v fully charged) - panels are around 40v each (not selected the panels yet but they all seem to be in the 38-45v range per panel).

So if I go with a Victron 100/20 48v MPPT I would *have to* run the string in a series config to get the voltage I need.

If I do put panels along the side grab rails they would have to be much smaller panels then I would want for mounting over the stern awning. I would like 600w+ x 2 permenatly fixed to the stern awning and a further 2 600w+ on a rail system that slides out to reveal the 2nd PV panel under the permenatly mounted one.

For the side mount panels I would need to go down to a 300/400w panel in order to fit the area for mounting better.

So what a mess.....!! 2 x 600w panels - one facing slightly East and one facing slightly West that are permanently mounted to the awning, 2 x 600w that slide out on rails from under the main 600w panels and 2 x 300w panels down each side of the boat - so again 2 x 300w facing east and 2 x 300w facing west.

Even if I were to favor an MPPT per panel to overcome the shading/orientation issues there is the problem that one panel is not high enough in voltage to start the MPPT.

So how to do this ?

 

[Bop]

If I had been installing it from scratch, I would have steered clear of the 48v gear to begin with and stayed at the voltage of the aux motor alternator/ starting system (usually 12v on sail boats, although many ex trawlers etc use 24v)

Which is why it is better to plan these things out from the beginning...
As it is, you now have the 'sunk cost' issue to deal with....

Series arrays 'can' handle shadowing, yes they have losses, but not much different to parallel panels

The 'best' solution imho is either go for higher voltage panels (some brands/models can have single panels up to 80v Voc- Stion make smaller panels around the 130-150w range that run at 80v Voc, or the Aussie made Sliver make a 90v Voc 145w panel, so a search for any of the higher voltage panels that many are unaware of will open up a range of options you were previously unaware of...) These allow a single panel with voltage high enough to start the MPPT up (remembering that they normally need about 5v above the battery voltage to actually get into the more efficient MPPT regime, below that they stay in PWM mode and you lose output) or use small series strings (say 2 38v-45v Voc panels in series) then parallel those series pairs...

There are 'boost' MPPT controllers around (often used for 48v golf carts and the like for their solar roofs) but in boost mode- their efficiency is rather poor... best avoided imho

https://www.originenergy.com.au/wp-content/uploads/Sliver4500_Panel_Specifications.pdf

 

[Ohms_Cousin]

If I had been installing it from scratch, I would have steered clear of the 48v gear to begin with and stayed at the voltage of the aux motor alternator/ starting system (usually 12v on sail boats, although many ex trawlers etc use 24v)

Which is why it is better to plan these things out from the beginning...
As it is, you now have the 'sunk cost' issue to deal with....

Series arrays 'can' handle shadowing, yes they have losses, but not much different to parallel panels

The 'best' solution imho is either go for higher voltage panels (some brands/models can have single panels up to 80v Voc- Stion make smaller panels around the 130-150w range that run at 80v Voc, or the Aussie made Sliver make a 90v Voc 145w panel, so a search for any of the higher voltage panels that many are unaware of will open up a range of options you were previously unaware of...) These allow a single panel with voltage high enough to start the MPPT up (remembering that they normally need about 5v above the battery voltage to actually get into the more efficient MPPT regime, below that they stay in PWM mode and you lose output) or use small series strings (say 2 38v-45v Voc panels in series) then parallel those series pairs...

There are 'boost' MPPT controllers around (often used for 48v golf carts and the like for their solar roofs) but in boost mode- their efficiency is rather poor... best avoided imho

https://www.originenergy.com.au/wp-content/uploads/Sliver4500_Panel_Specifications.pdf
View attachment 237363

No, not wasted or any sunk cost issues. I need 48v on my boat as going for an all electric galley and I have 2 x 48v motors to run as an electric boat.

I do know there are panels out there that run at higher higher voltages - just none to be found where I am located and shipping panels in would be outrageously expensive - so thats not an option.

One option may be to run Tigo optimisers (to stay all DC to DC) OR an Enphase Microinverter that converts the panels DC power to AC power at the panel. Issue with micro inverters is the batteries become "AC coupled" so DC from panel -> AC at micro inverter -> DC conversion at MultiPlus II to charge the batteries and finally -Dc to AC to run an appliance on AC voltage from inverter. Thats got to be a lot of losses going on.

Advantage to the optimizer or micro inverter is the low start up voltage needed to get the optimizer or the Micro inverter is around 20v -80v ...so can be used with most panels.

So far thats about the only way to manage this issue - either use an optimizer or micro inverter per panel or run panels in series/parallel config groups and live with the shading issues from time to time, or use high voltage panels that are hard to get locally and each panel would require its own SCC to get the most out of each panel.

Is there any other method that I am missing ?

 

[Suijkerbuijk]

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[Bop]

No, not wasted or any sunk cost issues. I need 48v on my boat as going for an all electric galley and I have 2 x 48v motors to run as an electric boat.

I do know there are panels out there that run at higher higher voltages - just none to be found where I am located and shipping panels in would be outrageously expensive - so thats not an option.

One option may be to run Tigo optimisers (to stay all DC to DC) OR an Enphase Microinverter that converts the panels DC power to AC power at the panel. Issue with micro inverters is the batteries become "AC coupled" so DC from panel -> AC at micro inverter -> DC conversion at MultiPlus II to charge the batteries and finally -Dc to AC to run an appliance on AC voltage from inverter. Thats got to be a lot of losses going on.

Advantage to the optimizer or micro inverter is the low start up voltage needed to get the optimizer or the Micro inverter is around 20v -80v ...so can be used with most panels.

So far thats about the only way to manage this issue - either use an optimizer or micro inverter per panel or run panels in series/parallel config groups and live with the shading issues from time to time, or use high voltage panels that are hard to get locally and each panel would require its own SCC to get the most out of each panel.

Is there any other method that I am missing ?

Many people are fascinated with this 'need 48v for cooking/tools' thing- you REALLY don't need to go to 48v in the first place (especially on a boat, where a huge 4 oven 7 burner cooktop is 'unlikely' to be found...)

Hell- I do all my cooking here on a 12v system (because of the 12v caravan system at the shed while building the house), with a 8kw 12v inverter ((that also runs the welder and the like)- yes you do need to set it up correctly, and it needs heavier cabling- which is all of 30cm/1ft long!!!


That even runs the portable AC unit in the caravan on hot days...
Off 12v (a 1600Ah 12v LYP battery bank, that will eventually be running the house at 48v, but for now configured as 12v because of the lights/pumps/tv etc built into the van...)

 

[efficientPV]

If starting from the beginning, I would have used mppt boost converters. It would probably need one for every two panels in parallel. These are quite cheap and four would probably cost less than the victron.

 

[Ohms_Cousin]

Many people are fascinated with this 'need 48v for cooking/tools' thing- you REALLY don't need to go to 48v in the first place (especially on a boat, where a huge 4 oven 7 burner cooktop is 'unlikely' to be found...)

Hell- I do all my cooking here on a 12v system (because of the 12v caravan system at the shed while building the house), with a 8kw 12v inverter ((that also runs the welder and the like)- yes you do need to set it up correctly, and it needs heavier cabling- which is all of 30cm/1ft long!!!
View attachment 237367

That even runs the portable AC unit in the caravan on hot days...
Off 12v (a 1600Ah 12v LYP battery bank, that will eventually be running the house at 48v, but for now configured as 12v because of the lights/pumps/tv etc built into the van...)

2 x 48v motors mounted to the hull. 48v it is then. All planned from the start. Was not going to go solar but changed my mind and want to install panels as mentioned above. So Solar has to fit into the 48v system.

 

[Bop]

2 x 48v motors mounted to the hull. 48v it is then. All planned from the start. Was not going to go solar but changed my mind and want to install panels as mentioned above. So Solar has to fit into the 48v system.

Well you have to accept that your design choices dictate your equipment choices- it isn't as if there is a way to order stuff internationally- they really need to invent something that would let you use say a computer to order stuff from far away....

 

[Ohms_Cousin]

Well you have to accept that your design choices dictate your equipment choices- it isn't as if there is a way to order stuff internationally- they really need to invent something that would let you use say a computer to order stuff from far away....

Hmmm that would be a great invention indeed.

But back to the issue at hand. So it seems it comes down to high voltage panels, OR panels in series/parallel config and live with the shading losses OR install Tigo optimisers or micro inverters.

Anybody got any other ideas ?

 

[IGBT]

On our sailboat with a 48 volt battery and 48 volt electric motor, we are going with a Victron 150/35 MPPT and using CIGS solar panels which are quite shade tolerant (because they have 24 bypass diodes per panel). My testing shows that a mast or stay shadow that would wreck the output of a normal panel only reduces the CIGS panel output by the % of diodes that are activated. Thus two shadows across the panel which activate 8 diodes, reduce the 200 watt panel output down to 16/24, or 130 watts (or thereabouts). A 200 watt glass panel with 2 bypass diodes might drop down to near 0 watts with 2 big shadows across it.

 

[yabert]

The issue is I dont want to run the string in series due to shading issues (boom/mast/rigging wires/sails when under way). Parallel is not much use to me in this scenario as I need to get the voltage at least 5v above battery voltage which in this case is 61v min (battery is 56v fully charged) - panels are around 40v each (not selected the panels yet but they all seem to be in the 38-45v range per panel).

I'm in the same situation for our sailboat.
I've looked at high voltage solar panel: https://diysolarforum.com/threads/high-voltage-solar-panel-60-70vmp.87106/
I've looked at Boost MPPT like this: https://ebikes.ca/adjustable-400w-boost-mppt.html
And I will probably end with 4 typical panels with split cells in a configuration 2 series of 2 parallel with two Victron 100/20-48.
I'm confident that split cells panels can help considerably with the shade.

 

[Ohms_Cousin]

On our sailboat with a 48 volt battery and 48 volt electric motor, we are going with a Victron 150/35 MPPT and using CIGS solar panels which are quite shade tolerant (because they have 24 bypass diodes per panel). My testing shows that a mast or stay shadow that would wreck the output of a normal panel only reduces the CIGS panel output by the % of diodes that are activated. Thus two shadows across the panel which activate 8 diodes, reduce the 200 watt panel output down to 16/24, or 130 watts (or thereabouts). A 200 watt glass panel with 2 bypass diodes might drop down to near 0 watts with 2 big shadows across it.

Very interesting. I searched and found these panels locally. However the problem is they still dont get a high enough voltage to run a single panel with a SCC. They are not very efficient though......14.3% !!

"The Cigs-3350A1 solar panels have a rated output of 335 Wp and an impressive efficiency of 14.3 %, making them an excellent choice for homeowners looking to harness the power of the sun and reduce their energy costs."

 

[IGBT]

Very interesting. I searched and found these panels locally. However the problem is they still dont get a high enough voltage to run a single panel with a SCC. They are not very efficient though......14.3% !!

"The Cigs-3350A1 solar panels have a rated output of 335 Wp and an impressive efficiency of 14.3 %, making them an excellent choice for homeowners looking to harness the power of the sun and reduce their energy costs."

I don't know anything about that panel. The ones I am using are from BougeRV and are (possibly) based on MiaSole flexible CIGS tech. They are made somewhere in China at any rate (what isn't?).

There are CIGS glass panels but I don't know if those include bypass diodes for each cell like the BougeRV flexible ones. I wanted flexible because I plan to roll them all up and stick them in the cockpit locker when not in use. 17% cell efficiency so 14.3% panel efficiency sounds about right.

 

[yabert]

They are not very efficient though......14.3% !!

Wow! not so interesting.
That represent almost 150% of the surface area of regular 21-22% efficient panels for the same output.
That, to me, is more critical than shade.

 

[IGBT]

Wow! not so interesting.
That represent almost 150% of the surface area of regular 21-22% efficient panels for the same output.
That, to me, is more critical than shade.

It is only interesting if you try to roll up a glass panel into a 11" tube. The output goes really low when you do that.

 

[Ohms_Cousin]

Wow! not so interesting.
That represent almost 150% of the surface area of regular 21-22% efficient panels for the same output.
That, to me, is more critical than shade.

yeah its kinda hard to figure what would work best - 14.3% is dismal these days for sure - BUT - if the panel keeps giving in shaded conditions then although its not very efficient it might actually give more over a day then a 22% efficient panel ?

 

[yabert]

Yeah, really depend of boat and other details.
At the moment, for me on our Beneteau 37', the best plan seem to have a permanent array in the rear of the boat who act as a bimini + dinghy davit.

 

[Ohms_Cousin]

Yeah, really depend of boat and other details.
At the moment, for me on our Beneteau 37', the best plan seem to have a permanent array in the rear of the boat who act as a bimini + dinghy davit.

exactly what I am doing on my 42ft'er

 

[yabert]

exactly what I am doing on my 42ft'er

Nice! Even more space than me. Do you have pics?
Here is the rough plan for this winter modification on our boat.
A complete new aluminum structure will be build.

 

[Ohms_Cousin]

Nice! Even more space than me. Do you have pics?
Here is the rough plan for this winter modification on our boat.
A complete new aluminum structure will be build.

View attachment 237696

No, no photos at the moment. The boat is being rebuilt so a long way to go.

 

[HarryN]

Take a look at the gensun solar charge controllers. They were designed by an EE that is a sailor just for this reason.

I have used them in vans with good success.

Genasun – Sunforge LLC

sunforgellc.com

 

[IGBT]

Take a look at the gensun solar charge controllers. They were designed by an EE that is a sailor just for this reason.

I have used them in vans with good success.

Genasun – Sunforge LLC

sunforgellc.com

Very expensive for a 48V system though. The GVB-8 boost is about $190 and only supports a 350 watt panel.

 

[HarryN]

Very expensive for a 48V system though. The GVB-8 boost is about $190 and only supports a 350 watt panel.

I guess it depends on your viewpoint.

People drop much more than that for victron solar chargers and this will work much better for sail boat / rapidly changing conditions.

There is no superior technical solution, so it is really just a matter of willingness to spend a few hundred dollars to optimize a power system that is costing ~ $5 - 10K.

For me, they are a proven entity so....

I am a big fan of a mixture of panels facing "up" and "sideways".

Here is how I power my off grid work shop - spartan as it is.

~ 150 watts facing "up" and ~ 300 watts mounted vertically.

All of that is feeding one genesun into a 48 volt pack.

Roughly 5 pm PST, this is what it looks like.

The turn on voltage is something like 10 - 11 volts, so it will start charging very early in the morning and run later than most setups.

 

[IGBT]

A Victron 150/35 which is a bluetooth enabled 48V charger capable of supporting a 150V string at 35 amps is the same price as one GVB-8, which is quite old tech now (they even admit this on their website:

"Panel ratings have increased since we designed the GVB-8. Although we don't believe in changing specifications without a corresponding engineering change, based on both our customers' experiences over the years as well as the headroom we designed into the GVB-8, we feel comfortable recommending the GVB-8 for panels with Imp up to 9 A."

 

[yabert]

That lead me to ask when Victron will come with a 75/15 boost MPPT.
That would be ideal in my situation.