Shaded Panels - Catamaran Boom

[Pete7]

Originally Posted by ArranP

However these are regulations for USA only. In Europe ( Maybe Aus ) I gather regulations don't stipulation this interconnection between AC Earth and DC Negative, which maybe the piont that you were reluctant to convey, as you did not want me go de-coupling the DC Negative fromt the commond busbar, and assume I would then be safe having done so.
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A lot of yachts in Europe have the AC earth connected to the DC negative and on to an anode, mine does. What we don't generally have is seacocks wired to the DC negative, but that's another story.

Pete

[hzcruiser]

Originally Posted by Pete7

A lot of yachts in Europe have the AC earth connected to the DC negative and on to an anode, mine does. What we don't generally have is seacocks wired to the DC negative, but that's another story.

Pete

You mean protective earth, not AC neutral, I take it?

[ArranP]

Originally Posted by hzcruiser

Not quite opposing, more like both options have their merits...

And yes, high DC voltage (as in >48V) is not per se wrong on a boat, only running an additional conduit through the boat is much more involved than just routing the wires directly as part of the bigger loom.

Furthermore please keep in mind the standards likely also prohibit running high DC (or AC) voltage through the same conduit as low voltage DC, hence a second conduit is needed.

It appears a tipping point between using high voltage dc or not is the use of conduit to run the dc of cables.

There is plenty of space in the run down from the bimini top to the electric room, it goes across the ceiling of the saloon where there is a substantial gap between the ceiling panels and the fibreglass roof.

I am familiar with the solar equipment that I have used my at home, my preference is to stay with it if possible. DC optimisers can be used in strings of panels to mitigate the loss of power due to shading.

[ArranP]

Originally Posted by hzcruiser

From your reference list I can see you're doing your due diligence, good on you! And you already noticed that even the different standards have varying recommendations...

To quickly answer your questions: DC negative should or is generally connected to "chassis", as you call it, through the engine block and the starter motor anyway. Also the engine is connected to the outside water via the prop shaft. That's why it's the "normal" thing to do, connecting the battery minus to the engine.
The recommendation you read in other forum threads about having exactly one ground has to do with electrolysis issues, not electrocuting yourself.

In your first paragraph you mention "AC earth". I would reiterate that AC has the phase (or life wire) and neutral, which is "return". The third wire is then protective earth (PE) and should _not_ carry any current but rather trip the breaker if it is. That's how it's protecting you.
But there is more to that and whether or not connecting PE to battery minus or the engine... that's why I recommended getting a pro involved.

Yes, the green wire should under normal conditions NOT carry any current, ONLY when there is a fault occurs should it carry current, it acts as an "alternate route to earth" and importantly less resistive that the human body.

I do not plan to have any connection to shore based power including power from a marine supply, at any time. All AC power will be generated on board via the inverters or deisel engines alternator..... I believe there have been cases of water electrocution of swimmers near boats in mariners due to the current returning through the grounding plate / water, rather than the through marine supplied AC Earth wire, caused by incorrect AC wiring on the boat.

On my boat as the AC power is being generated by the onboard inverter I believe the AC Earth should be connected to the Neutral at or inside of the inverter.

I won't comment any further until I complete my reading of the 16 page article.
https://newboatbuilders.com/pages/electricity1.html

[hzcruiser]

Originally Posted by ArranP

It appears a tipping point between using high voltage dc or not is the use of conduit to run the dc of cables.

There is plenty of space in the run down from the bimini top to the electric room, it goes across the ceiling of the saloon where there is a substantial gap between the ceiling panels and the fibreglass roof.

I am familiar with the solar equipment that I have used my at home, my preference is to stay with it if possible. DC optimisers can be used in strings of panels to mitigate the loss of power due to shading.

Well, then go with it, by all means. As mentioned, both options have their merits.

[SV__Grace]

Originally Posted by ArranP

Following are two layouts for solar panels, I have attempted to demonstrate the shading when the boom is on the left and when the boom is on the right side.

Seems like you are in the planning stage and if you haven't already purchased your solar panels you might consider the REC Alpha Series, which are twin panels- each panel is split into two halves.

I recently upgraded my older solar panels and wanted higher output in the same size. In researching the available options the PO of our boat recommended these solar panels and it solves my shading problem.

Being a ketch, when I tie the boom all the way to one side, the mast and the mizzen are the source of shading and almost always shade one corner.

Have the equivalent of 4 panels laid out in a square, wired in parallel, if one is shaded the other 3 are still in full sun (well, more cloudy sun here in PNW). The twin panel design seems perfect for the shading issues on boats.

[skenn_ie]

Solar panels output according to the exposure of the weakest cell. It makes no difference if all the cells are shaded as opposed to a single cell.

[tdtrimmer]

Originally Posted by ArranP

Following are two layouts for solar panels, I have attempted to demonstrate the shading when the boom is on the left and when the boom is on the right side.

I am uncertain of the best possible configuration in terms of strings and parallel.

I have 4 mppt charge controllers, more can be add more if need be. Panels are 500w 1.2m x 2.1m

Attachment 249722

Attachment 249723

Thank you for your comments

Have you considered Semi-rigid walk-on panels from companies like Custom Marine Products? The performance is comparable to rigid panels, they are robust and can be walked on anytime.

[hzcruiser]

Originally Posted by skenn_ie

Solar panels output according to the exposure of the weakest cell. It makes no difference if all the cells are shaded as opposed to a single cell.

Can you prove or corroborate such an outlandish statement please?

[jeepers]

For @ anchor or at the dock.
Does the Cat have in mast furling?
If so. Wind the sail in.
Hoist the boom up against the mast.
May require a pivot @ gooseneck.

There are actuators and slides that will slide the solar panels approx 48-60 inches.
This is Episode #5 on a Youtube channel (Beginning from this Morning) that put sliding solar panels on a coach bus roof.
Maybe these 5 videos will give you ideas on "moving" solar panels
1.) out of shade
2.) to create clear access to the boom.
3.) provide visibility of the sail set & mast.
4.) provide a easy path of access up to the solar panels.
5.) increasing the number of solar panels possible as well as shade.

https://www.youtube.com/watch?v=LE10sgaCKHA

[HeywoodJ]

Originally Posted by hzcruiser

Can you prove or corroborate such an outlandish statement please?

Not at all outlandish. A cell can only pass the amount of current that is generated by the light on that cell. A fully shaded cell will have zero current, and this will affect all other cells connected in series between any bypass diodes (if fitted).

Corroboration

An individual solar cell has an output of 0.5 V. Cells are connected in series in a module to increase the voltage. Since the cells are in series, the current has to be the same in each cell and shading one cell causes the current in the string of cells to fall to the level of the shaded cell. Typically, the module ISC is reduced to the lowest ISC of all the cells in a string. Shading just one cell in a module to half causes the output power of the whole module to fall to half. No matter how many cells there are in the string, completely shading one cell causes the output power of the module to fall to zero. The lost output power of all the unshaded cells is dissipated in the shaded cell. It is even worse at the system level, where multiple modules are in series to increase the system voltage to 600 or 1000 V and shading one cell would affect the entire module string

More Corroboration

Shading of a Single Cell
The output of a cell decreases drastically when shaded by any blockage like a tree branch, a building or dust accumulating on the module. The output decreases proportionally to the percentage of shading. For completely opaque objects like leaves, the decrease in current output of the cell is proportional to the percentage of the cell that is blocked.

Even More

Shading a solar cell is similar to introducing a clog in a pipe of water. The clog in the pipe restricts the flow of water through the entire pipe. Similarly, when a solar cell is shaded, the current through the entire string is reduced.

[Uncle Bob]

Originally Posted by HeywoodJ

Not at all outlandish. A cell can only pass the amount of current that is generated by the light on that cell. A fully shaded cell will have zero current, and this will affect all other cells connected in series between any bypass diodes (if fitted).

Corroboration



More Corroboration


Even More

The perfect demonstration of why panels should be wired in parallel on a boat, or at least series and parallel.

[Shaneesprit]

I have a single panel and it works just fine not perfect because it faces away from the sun while on its mooring, so that’s at least 50% of the year - worrying about shade is like worrying about the clouds or snow.
Although I do have a nice photo somewhere of someone on a building installation with a roof over the solar water heater tubes 😂 I can only think that the water was too hot

[sv Stella Maris]

**This is tested, not opinion:

We had (7) panels on our cat, total of 2,320 watts. Experimented with multiple configs. Takeaway:

-new split cell panel technology (such as Q-Cell panels) completely eliminated the concern for shading. Even in series with a middle panel completely shaded the other panels are not affected at all.

With split cell tech this debate is a mute point of the past.

PM me for specific questions.

(All Victron components used for real-time-feedback during testing. Loads were in excess of 2kw)

(Utilize larger MPPT’s to maximize voltage to
minimize wire size)

[CatNewBee]

Originally Posted by sv Stella Maris

**This is tested, not opinion:

We had (7) panels on our cat, total of 2,320 watts. Experimented with multiple configs. Takeaway:

-new split cell panel technology (such as Q-Cell panels) completely eliminated the concern for shading. Even in series with a middle panel completely shaded the other panels are not affected at all.

With split cell tech this debate is a mute point of the past.

PM me for specific questions.

(All Victron components used for real-time-feedback during testing. Loads were in excess of 2kw)

(Utilize larger MPPT’s to maximize voltage to
minimize wire size)

Bypass diodes are common technology in large panels, nothing to do with split cells, the shaded part is bypassed, the voltage drops, but there is still some current from the remaining unshaded string bypassing the shaded part. Parallel is still better.