Solar panel partial shading - SailNet Community
 8Likes
Reply
 
LinkBack Thread Tools
post #1 of 14 Old 4 Weeks Ago Thread Starter
Barquito
 
Barquito's Avatar
 
Join Date: Dec 2007
Location: Madison, WI
Posts: 3,371
Thanks: 1
Thanked 87 Times in 86 Posts
Rep Power: 13
 
Solar panel partial shading

For the panels that are mounted on top of the dodger, for example, wouldn't the boom really kill the output due to partial shading? Does having two panels up their help? Does it help to use thin film amorphous panels? I want to sort out if a position under the boom is just not ideal, or really inefficient.

Valiant 32
Barquito is online now  
Sponsored Links
Advertisement
 
post #2 of 14 Old 4 Weeks Ago
Member
 
aeaston's Avatar
 
Join Date: Aug 2011
Location: Nova Scotia
Posts: 57
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 9
 
I have a panel on the dodger. Single older style 100 watt. When it's partially shaded, output is greatly reduced.

When at anchor or moored, which is most of the time, I move the mainsheet to the toerail which gets the boom shade off the panel and output is back where it should be.

I also have 2 50 watt panels on the Bimini, but haven't yet noticed if it's better than the single or not. These are the thin flexible variety.
aeaston is offline  
post #3 of 14 Old 4 Weeks Ago
Moderator
 
MarkofSeaLife's Avatar
 
Join Date: Nov 2010
Location: London!
Posts: 6,916
Thanks: 69
Thanked 309 Times in 280 Posts
Rep Power: 10
 
Dock
Re: Solar panel partial shading

I think the overshaddowing is a bit over rated. Yes its going to drop a bit of power but its better than nothing. Yes, hauling out the boom is going to be better, as is tilting panels towards the sun.
What about clouds? No need to shake a fist at them either imho.

But they only need a bit of sun and they still make power.

Sea Life
Notes on a Circumnavigation:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


People can say they want freedom, but offer them the keys to what chains them, a map to where they want to go,
And they'll turn it down for the cell they know
MarkofSeaLife is offline  
 
post #4 of 14 Old 4 Weeks Ago
Senior Member
 
colemj's Avatar
 
Join Date: Jul 2003
Location: On the boat cruising
Posts: 3,128
Thanks: 4
Thanked 125 Times in 119 Posts
Rep Power: 17
 
Re: Solar panel partial shading

Solar panels consist of a bunch of small cells connected in series strings. Let's say your panel has 3 of these series strings. If a small area of the panel is shaded so that the shadow falls on only one of the strings, then you would lose up to 1/3 of your output. However, if the same small piece of shade falls across all 3 strings, then you will lose almost the entire panel output.

The type and style of cells makes no difference, so amorphous, thin film, etc are meaningless in this regard.

Most people just move their boom out of the way of bimini mounted panels whenever they can.

Solar mounted anywhere is better than no solar at all.

Mark

Dolphin 460 Catamaran "Reach"

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Current boat

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Previous boat
colemj is offline  
post #5 of 14 Old 4 Weeks Ago
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Westchester, NY
Posts: 4,246
Thanks: 2
Thanked 108 Times in 108 Posts
Rep Power: 13
 
Re: Solar panel partial shading

My anecdotal experience....

My 2 panels sit on the coach roof along side a hatch in the salon and DO get shade from the boom or the main at times. These panels (total 110watts) are for keeping the house bank (500 ah) topped up. I do not monitor their output. But they do the job... my bat voltage, if that's a measure... when I return to the boat (at anchor or moored) is pretty much 12.9 - 13.2). Since this is working for me... and has for 25 years, I don't see a problem. I do not have any continuous high amp loads like refer.

When sailing I have the instruments, and the AP... and at night we have LED lighting and maybe the PC. So if you are not needing a lot of charging (alternative) to satisfy hungry loads... then you don't need much solar power. When we do run our refer it is with the engine which also has a high output alternator. This works for me! YMMV

pay attention... someone's life depends on it
SanderO is online now  
post #6 of 14 Old 4 Weeks Ago
Old soul
 
MikeOReilly's Avatar
 
Join Date: Apr 2010
Location: Wherever I am
Posts: 4,186
Thanks: 258
Thanked 199 Times in 186 Posts
Rep Power: 10
 
Re: Solar panel partial shading

My 400 watt array consists of four separate panels. They are all run mid-ships, all under the boom. I definitely experience significant shading much of the time. But when thinking about my system I knew this would happen. I assume I'm exposing only 1/2 my panels most of the time.

All panels are parallel, which helps. And at anchor I swing the boom out to fully expose them. But underway we tend to get only 1/2 exposure most of the time.

Why go fast, when you can go slow.
BLOG:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
MikeOReilly is online now  
post #7 of 14 Old 4 Weeks Ago
Senior Member
 
colemj's Avatar
 
Join Date: Jul 2003
Location: On the boat cruising
Posts: 3,128
Thanks: 4
Thanked 125 Times in 119 Posts
Rep Power: 17
 
Re: Solar panel partial shading

Quote:
Originally Posted by MikeOReilly View Post
But underway we tend to get only 1/2 exposure most of the time.
Underway is always a crap shoot and no way to plan for it. If the sun is in the east, the winds will be west...

Mark
MikeOReilly likes this.

Dolphin 460 Catamaran "Reach"

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Current boat

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Previous boat
colemj is offline  
post #8 of 14 Old 4 Weeks Ago
Master Mariner
 
capta's Avatar
 
Join Date: Jun 2011
Location: somewhere south of civilization
Posts: 7,487
Thanks: 145
Thanked 401 Times in 389 Posts
Rep Power: 9
 
Re: Solar panel partial shading

Our panels do just fine on the bimini. The boom is only a few inches above the panels when we aren't sailing, so shading is minimized. They are separated significantly which helps for both shading and viewing the sails when sailing. It really doesn't matter where you mount your panels, unless you have a mechanism that keeps them facing the sun 100% of the time, you will rarely get full power out of them. And of course, there's clouds as Mark mentioned.
Plan for enough wattage to keep you batteries filled at 1/2 efficiency or even less over the daylight period where you intend to use your boat. Don't forget to leave an air space behind the panels if you mount them on your bimini, as heat also diminishes their efficiency.
Below is a pic of ours, 10 years trouble free and counting.
Attached Thumbnails
ss stern to.jpg  
SanderO and MarkofSeaLife like this.

"Any idiot can make a boat go; it takes a sailor to stop one." Spike Africa aboard the schooner Wanderer in Sausalito, Ca. 1964.
“Believe me, my young friend, there is nothing - absolutely nothing - half so much worth doing as simply messing about in boats.” ― Kenneth Grahame, The Wind in the Willows

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

facebook.com/svskippingstone

Last edited by capta; 4 Weeks Ago at 01:49 PM.
capta is online now  
post #9 of 14 Old 4 Weeks Ago
Old soul
 
MikeOReilly's Avatar
 
Join Date: Apr 2010
Location: Wherever I am
Posts: 4,186
Thanks: 258
Thanked 199 Times in 186 Posts
Rep Power: 10
 
Re: Solar panel partial shading

Looka nice Capta. Unfortunately our boat's boom is a lot bigger (proportionally speaking). My boom easily blankets my panels, but we still manage to generate good power most of the time.
Attached Thumbnails
IMGA0529.jpeg  
SanderO likes this.

Why go fast, when you can go slow.
BLOG:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
MikeOReilly is online now  
post #10 of 14 Old 4 Weeks Ago Thread Starter
Barquito
 
Barquito's Avatar
 
Join Date: Dec 2007
Location: Madison, WI
Posts: 3,371
Thanks: 1
Thanked 87 Times in 86 Posts
Rep Power: 13
 
Re: Solar panel partial shading

Thanks for the real-world responses. I think I will go with nuclear power.

Valiant 32
Barquito is online now  
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome