Are two partially shaded total 260W panels worth it

[coopec43]

Increased Output

An Enphase Micro Inverter is attached to the mounting kit underneath each panel. The micro inverter uses state of the art electronics to convert DC to AC underneath each panel. This allows each individual panel to output power independently from the other panels, significantly increasing system output.
According to Renewable Energy World, shading of as little as 9% of a solar system connected to a central inverter, can lead to a system-wide decline in power output with as much as 54%.


https://solaray.com.au/the-best-solar-system-in-australia-in-2019/

[mickt243]

Originally Posted by coopec43

Increased Output

An Enphase Micro Inverter is attached to the mounting kit underneath each panel. The micro inverter uses state of the art electronics to convert DC to AC underneath each panel. This allows each individual panel to output power independently from the other panels, significantly increasing system output.
According to Renewable Energy World, shading of as little as 9% of a solar system connected to a central inverter, can lead to a system-wide decline in power output with as much as 54%.


https://solaray.com.au/the-best-solar-system-in-australia-in-2019/

Enphase micro inverters are of no use here, they are designed for grid connection and will shut down with no grid power (until the iq8’s hit the market)

Op is better off with each panel connected to its own mppt battery charger - something like a Victron 75/15.....

[coopec43]

I have no experience with solar panels but after reading all the comments I have come to the conclusion that shading has a devastating effect on a solar panel output.

If that is correct then wouldn't it be better to have smaller moveable panels as pictured?

[hpeer]

I’ve a couple of new panels sold as 315 watt. But they are rated 250 watts in “standard” conditions. But that’s at 40v. So to get that available power I needed MPPT controllers. (this have been a slow and expensive learning curve.). Just fitted the controllers 3 days ago and have been watching them. Panels are mounted on an arch along with a wind generator and radar.

Here are my initial observations. You can very clearly see the drop in power when the boat swings so that there is a shadow on the panels. It is all of 50%, perhaps more. The controller records some bits of data so I can see that my leak power during the day was 218watts from one panel. But on average I’m getting 70 or so watts. We are in the Carribean, so the boat lays facing East, sun on south side, ensures maximum shade. It would be better if the wind was out of the South, or if the wind generator was mounted on the Port side, but alas, no.

When the sky is clear the swings due to shading are quite noticeable. When ther is some overcast well then the power output is more stable, I guess the clouds disperse the sunlight and reduce the sharp shadows through reflected and refracted light.

Bottom line is, on the two full days of data I have, I’m getting 450 watts which is about 400 amps from each panel, or 800 amps total. Not a bad boost to the batteries.

Moving on, elsewhere I’ve heard others disparage running dissimilar panels in parallel. I personally have my system set up so each panel is totally separate, 2 controllers. If one dies the other is independent.

[petesals]

I agree with Mickt, use a separate mppt regulator for each panel so you will get full performance from whichever panel is not shaded. I am currently mounting 5 x 300 watt panels on my cat and plan to use 5 moderately sized regulators. Turns out cheaper as well!

[Jim Cate]

Bottom line is, on the two full days of data I have, I’m getting 450 watts which is about 400 amps from each panel, or 800 amps total. Not a bad boost to the batteries.

Alternative reality??? Y ou said two panels rated at 250 watts under normal conditions (meaning no shade, near 90 degree sun angle, reasonable temperature. I can see peak power near noon and with low soc in batteries reaching 450 watts. Daily average will be WAY lower than that. And where in the world did you get 400 amperes from each panel? Around 25 to 30 amps peak is more like it... and that's from both panels combined.

You need to rethink your calculations...

Jim

[john61ct]

450W is maybe 25 amps.

In **ideal** conditions may contribute an average 150Ah per day of actual charging.

Any shading or clouds, or higher latitudes, can easily cut that by at least half.

[foggysail]

Originally Posted by john61ct

450W is maybe 25 amps.

In **ideal** conditions may contribute an average 150Ah per day of actual charging.

Any shading or clouds, or higher latitudes, can easily cut that by at least half.

That is confusing. I know you are well aware of relationship of watts, volts and current.

[Mike OReilly]

It’s hard to avoid shading on a sailboat, especially smallish cruising monohulls. So you have to assume some level of shading pretty much all the time. This is why parallel panels are generally preferred.

I have 400 watts set up in four parallel panels. My panels are relatively new. It’s easy to run the test to see how shading impacts them. I’ve found all it requires is a small amount of shading to significantly knock down a panel’s output. Even dispersed shading from standing rigging will impact my panels. Clouds, water vapour and (last year) smoke from forest fires can have noticeable negative impacts.

At anchor I swing the boom out to the appropriate side get full exposure. At peak I see around 25 amps, but more typically something like 18-20 under good sun. Up where I cruise (~50 degrees North) I see six to eight hours of peak sun in the summer. So about 150 Ah seems about right — on a good day.

[john61ct]

And no, newer cell technologies have not ameliorated the issue, that's a deceptive sales pitch.

[The Sun King]

Originally Posted by Tenedos

Having now made the decision not to install an arch on our 32ft Catalina, I am debating whether to put solar panels on the dodger and in front of it. I think I can fit one 160W panel and another 100W panel and connect them in parallel. However the issue is they will always be partially shaded (boom and mast for the one on dodger and boom, mast and lines for the other).

So I am wondering if this is worth it at all. I am not looking for much, something to trickle the batteries (I have two 8D flooded) when the boat is at a mooring.

This year, we are planning to sail down the California coast and we may need to leave the boat at Morro Bay at a mooring for a month or two. I would love to keep my camera on then, so I can check what is going on from home That would require to power an LTE modem, a wifi camera and an access point. I certainly don't want to drain the battery when I am away.


Thoughts, suggestions?

Amorphous or thin film panels are larger than crystalline, but tend to perform much better in a semi-shaded situation. They are also less affected by seagull poop! Any panel will put out some. If you are using 12v panels (I would not) to charge a 12v battery you might do better in series with an MPPT charge controller.

[nilespf]

Tenedos,
Look at how the bypass diodes are configured and configure the panels accordingly. You may be able to determine how many rows will be shaded and if the diodes will bypass the rows. Sometimes having a controller for each panel will help further eliminating adjacent cause/effect. If your willing to spend the money, pick panels with built-in controllers.



PN

[dinghysailor]

I have been told that if you only have 2 or 3 panels then to minimise the effect of shading have equal nominal capacity panels and connect them in series (not parallel) to a MPPT charge controller that is specified to accept the maximum voltage of the panels connected in series.



Can someone tell me if the above makes sense?
If it does, then is this a suitable combination? :



Three in number 60W semi flexible panels that have 23.9V open circuit voltage and a short circuit current of 3.15amps connected in series to a Victron MPPT 75/10 charge controller (max 10amps at 75v input)

[foggysail]

Originally Posted by dinghysailor

I have been told that if you only have 2 or 3 panels then to minimise the effect of shading have equal nominal capacity panels and connect them in series (not parallel) to a MPPT charge controller that is specified to accept the maximum voltage of the panels connected in series.



Can someone tell me if the above makes sense?
If it does, then is this a suitable combination? :



Three in number 60W semi flexible panels that have 23.9V open circuit voltage and a short circuit current of 3.15amps connected in series to a Victron MPPT 75/10 charge controller (max 10amps at 75v input)

I have two pairs of parallel panels connected in series and things work well for me. I have some degradation in shade although I have never seen the degradation other report that I should see. The benefits of having panels in series is that one can use much smaller wire sizes between the panels and the controller. Others have different opinions

[sailorboy1]

I recently installed 2 new 330W panels. This morning at 0830 I noticed that each panel had a shade band along their length that was about 4" wide because they sit about 1" lower than the aluminum angle I used to make the frame.

I was still getting 6 amps.

By 0900 I was getting 12 amps, and by 1100 getting 20+

There's almost always going to be some shading occurring to your panels during the the day.