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Old 04-12-2015, 09:34   #1
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Which solar panels - Flexible/rigid, 12/24 volt...

For anyone curious about the different types of solar panels on the market, we've lived on solar power for over eight years and done quite a few solar power installations on our boat and on RVs, using both 12 volt and 24 volt panels, rigid (framed) panels, flexible panels and both monocrystalline and polycrystalline panels.

Each type of panel is great in certain circumstances, but not in others, and I've written up some notes about what we've learned here:

Which Solar Panels to buy...Flexible or rigid? 12 or 24 volt? mono- or polycrystalline?

I hope this helps anyone who's thinking about doing a solar installation and found this stuff confusing (we sure did at first!)
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Old 04-12-2015, 21:51   #2
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

I thought from your Subject line that you were asking a question.

I've just spent a bit of time looking at your link and some of the other articles on your site as well.

That's a great resource and I've bookmarked it to spend more time there later.

Thank you for sharing!
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Old 05-12-2015, 07:43   #3
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

Thanks, Stu, I've really enjoyed learning about all this stuff and writing about it (in fact, I've got an article on solar coming out in Cruising World next summer).

Thank you for reading, bookmarking and for the kind words!!!
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Old 05-12-2015, 10:29   #4
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

Agree. I've bookmarked it too for later reference. Thanks.


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Old 05-12-2015, 12:43   #5
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

As mentioned in the article, I had two flexible solar panels cruising in the Caribbean.

After 18 months, one cell burnt and melted the covering plastic and made a brown mark on the fiberglass underneath. It was very hot and might caught fire if I didn't disconnect it. On the other, plastic film as very matte.

The other hard panels on the boat look as new.

The flexible was made in Sweden, and I thought the quality was OK but maybe made for a cooler climate.
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Old 05-12-2015, 18:33   #6
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

Quote:
Originally Posted by settingsun View Post
For anyone curious about the different types of solar panels on the market, we've lived on solar power for over eight years and done quite a few solar power installations on our boat and on RVs, using both 12 volt and 24 volt panels, rigid (framed) panels, flexible panels and both monocrystalline and polycrystalline panels.

Each type of panel is great in certain circumstances, but not in others, and I've written up some notes about what we've learned here:

Which Solar Panels to buy...Flexible or rigid? 12 or 24 volt? mono- or polycrystalline?

I hope this helps anyone who's thinking about doing a solar installation and found this stuff confusing (we sure did at first!)

Very well done piece, may have a confusing error/redundancy in one paragraph though.

The Paragraph titled: "What to do? SOLAR PANEL VOLTAGE and WIRE SIZE", has the last two sentences:
" In the case of solar panels wired in parallel, the voltage will be stepped down in the solar charge controller. So, in our example, the solar charge controller will step down the voltage from 48 volts to 12 volts, ensuring that the circuitry between the solar charge controller and the batteries is at operating at 12 volts."

It seems to state that a "parallel" SP array will be stepped down by the controller (possible of course), but the only examples given previously used a serial 48V panel connection example (in the paragraph: "WIRING SOLAR PANELS IN PARALLEL vs. IN SERIES"), in the circuit between the panels and the charge controller. The two panel examples given in the beginning of this paragraph don't fit this description.

Also, from that previous paragraph, and others, the use of "drop" isn't technically correct: "then the voltage drop across all the panels would be 48 volts (12 x 4)".
The words "...the developed voltage across all the panels...", as in "EMF developed", are more correct.
Versus using "drop", which refers to a loss of circuit voltage/EMF across a component(s), as from a resistor converting in-circuit voltage/EMF energy to heat lost.

The EMF/voltage is actually created, or developed, in the solar panels by converting solar insolation energy into electrical energy; then added/summed up by the silicone and 'forced' into the circuit/cables as a voltage/EMF and current (coulombs...arrrg, I said it...heading for the bunker now...).

"Electromotive force, also called emf (denoted and measured in volt),[1] is the voltage developed by any source of electrical energy such as a battery or dynamo. It is generally defined as the electrical potential for a source in a circuit.[2] A device that supplies electrical energy is called a seat of electromotive force or emf. Emfs convert chemical, mechanical, and other forms of energy into electrical energy.[3] The product of such a device is also known as emf."
https://en.wikipedia.org/wiki/Electromotive_force

Don't want to start another 'anchor' war, or like that other electrical 'debate' ongoing here, but a long career as a poly-systems EE makes it irresistible...
.
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Old 06-12-2015, 08:14   #7
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

Thank you Tayana42 for saving this for reading later, and thank you Sail IC for offering your experience with flexible panels (how frustrating for you, though!!).

And thanks, TxJ for reading my blog post with such attention to detail! Wow!!

I would change what I wrote about the series vs. parallel wiring, but the "example above" that I reference and that worries you is of two 240 watt panels wired in parallel as stated in the immediately previous paragraph. I think what I have is correctly referenced.

As for the use of the word "voltage drop" rather than "developed voltage," I was a physics major and we always used the term "voltage drop" to refer to the voltage difference between two end points, and that's what I had in mind here.

As a professional EE with a long standing career, you are definitely correct with the term "developed voltage," and I will make that change so my blog post is more accurate for the most discerning readers like yourself (once I get back from my hike today).

I appreciate your insights and technical expertise!

As you know, writing a blog post is something done from a passion to share information, not as a paid gig reviewed by an editorial staff. It's a little surprising to look at the clock and realize it has taken 80 hours to write a blog post like this one, but my hope is to provide an easy to read and easy to understand review of the major issues for sailors looking to put solar power on their boat.

-Emily
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Old 06-12-2015, 19:06   #8
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

Quote:
Originally Posted by Sail IC View Post
As mentioned in the article, I had two flexible solar panels cruising in the Caribbean.

After 18 months, one cell burnt and melted the covering plastic and made a brown mark on the fiberglass underneath. It was very hot and might caught fire if I didn't disconnect it. On the other, plastic film as very matte.

The other hard panels on the boat look as new.

The flexible was made in Sweden, and I thought the quality was OK but maybe made for a cooler climate.
Sorry to hear about your experience with those panels.

Almost all of the flexible panel manufacturers recommend mounting the panels with something to facilitate airflow beneath them. In our case, Solbian recommended using a couple of strips of two sided mounting tape when mounting them to a solid surface. There are lots of variations I am sure.

How were yours mounted?
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Old 07-12-2015, 00:33   #9
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

What brand were those "Swedish" solar panels. Most likely they were rebranded Chinese...

Solbian panels for hard surface mounting are available with a continuous backing of peel & stick adhesive; basically a full sheet of VHB tape. So they are fine without any air behind them. Note that on their panels over 100W, there are two series strings in series, and each has a small bypass diode laminated into the panel. These help reduce the chances of "hot spots" as only half (one string) can backfeed into any one shaded spot (as one string is shaded and voltage drops, current can bypass that string).
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Old 07-12-2015, 03:21   #10
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Lightbulb Re: Which solar panels - Flexible/rigid, 12/24 volt...

Thanks for that guys. All this info together really helps.
Happy sailing on the "roads less traveled"
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Old 07-12-2015, 07:52   #11
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

OceanPlanet - Thanks for the info, Solbian sounds interesting.
Blackie Swart - All smooth sailing on the roads less traveled...life is sweet! And thanks for reading!
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Old 07-12-2015, 11:26   #12
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

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Originally Posted by OceanPlanet View Post
What brand were those "Swedish" solar panels. Most likely they were rebranded Chinese...

Solbian panels for hard surface mounting are available with a continuous backing of peel & stick adhesive; basically a full sheet of VHB tape. So they are fine without any air behind them. Note that on their panels over 100W, there are two series strings in series, and each has a small bypass diode laminated into the panel. These help reduce the chances of "hot spots" as only half (one string) can backfeed into any one shaded spot (as one string is shaded and voltage drops, current can bypass that string).
Not sure of the original manufacturer of the panels. Maybe Chinese, maybe not. I bought it from a small company only selling solar panels and controllers.

I have a catamaran, and they were mounted flush on the hard cabin/bimini top. The only point to go flexible is to able to mount them flush on a slightly curved area and if requiring air to circulate underneath, I don't see the point of having a flexible panel (in my opinion).

I'm putting ridged panels now at the same space.
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Old 07-12-2015, 11:36   #13
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

I have been working on a design that uses angle stock to make a removable "solar tray" that attaches to a skeleton hard top with U bolts. The idea is that the flex panels themselves form the hard top, so there would be nothing but air under them except around the edges. This approach means that I can design the radar arch and hard top components to stay with the boat, and replace or upgrade the solar as technology changes. The design also allows me to use this setup to divert and store rain water. My biggest issue so far is getting someone to build me the radar arch. I've tried to get the attention of the "arch in a box" people, but they don't seem interested in building one that spans 145 inches.
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Old 07-12-2015, 11:38   #14
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Re: Which solar panels - Flexible/rigid, 12/24 volt...

Quote:
Originally Posted by Sail IC View Post
Not sure of the original manufacturer of the panels. Maybe Chinese, maybe not. I bought it from a small company only selling solar panels and controllers.

I have a catamaran, and they were mounted flush on the hard cabin/bimini top. The only point to go flexible is to able to mount them flush on a slightly curved area and if requiring air to circulate underneath, I don't see the point of having a flexible panel (in my opinion).

I'm putting ridged panels now at the same space.
Roger that. If rigid panels will work (without snagging sheets, etc. or getting hit by whatever), they are much less expensive. The best marine rigid panels we have seen are the Solara Ultra-S with high-grade SunPower cells. They are less $ than flexible however more than Kyocera/etc.

We have seen a lot of sales lately to rooftops on cats of Solbian -SM (Surface Mount) panels with a textured surface (semi-nonskid) the adhesive backing, and backside wiring for a flush surface.
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