Hello all!
Designing a solar panel array for Nausikaa.
There is some contradictory/inconsistent advise out there (tech docs from manufacturers vs sailor forums vs else) with regards to the best architecture, particularly on whether to wire the panels in series/parallel to maximise output with partial shading of the panels.
Now, I can only install panels on the cabin roof, and I need 360 watts to cover my daily energy budget.
Key issue here is shading on the cabin roof from the sails (I have a 30’ ck), and whether serial or parallel wiring of the panels will minimise the effects of partial shading on overall panel output.
I am asking for practical experience/advise here, from other owners with similar setups. There are some cost implications also (series wiring requires more expensive MTTP controllers). Length of cabling (re voltage drop-offs) and cost of other materials is virtually the same.
Many thanks in advance for the input!!
Rafael
I have 2 180 watt panels on my hardtop, one on each side of the boom. They are wired in parallel. After 10 years I can say that my setup has worked well for me and allows me to go for days at anchor without additional charging. Ten years of having solar cells has also shown me that given the position of the boom or how the wind blows the boat around at anchor some part of one of the panels will always be in shadow. Solar cells on a movable platform is a good example of a situation were good is great and perfect is impossible.
I went with 1 controller per panel based upon advice from installers to maximize panel output. It’s worked well for me.
– Geoff
You want panels that are divided by diodes, so that the shade doesn’t stop the output from the part in the sun. You might also want a switch to shut the panels down. I found both my regulator and charger base their output on voltage which will be high with solar operating. When the batteries are low and I charge, with the solar on the charger won’t put out any amps.
Just my experiences.
Gents
Thank you all for your input. Continuing with my research and will post updates.
@ Geoff, particularly interested in your setup of having one regulator per panel. Unexpected! I’d like to understand the efficiency rationale your installer gave you for this architecture. Are you using MPPT or PWM controllers? Where did you install the controllers in relation to the location of the batteries?
I have a clear run for cabling on the inside of the cabin roof. It only gets messy when running wires from the cabin roof to the aftmost lockers under the cabin seats, where I have my batteries.
Thanks again for the info!
Rafael
I have two flexible HQST 100 watt panels installed on my Mull 30. They are wired in series in an attempt to minimize shadowing impact. The panels are very light and I am happy with them. I spent quite a bit of money on an MPPT controller by midnite solar (the marinized kid). I have breakers for the panels and the controller. I like this set up if you have the breaker panel room for it. You can completely isolate the panels which appeals to me and conforms to the controller manufacturers recommendation. Absolutely agree with another poster on actual output. I have never seen more than about 120 watts from my system due to shadowing, sun angle, weather, water, there is always something. Having said this, the 120 watts takes care of my needs unless I am using the AP 24/7. In that case I have to engine charge for about 45 to 70 minutes per day. At anchor the 120 watts is way more than I need. I do not have refrigeration.
If you were to get the arrays on a bracket off the stern you could probably do a lot better regarding power out. I was going for the most secure install I could get and needed the stern for an emergency rudder assembly. So this wasn’t an option for me.
Hi Mike
Thanks for the input. 120 W actual out of 200 is somewhat disappointing. Hoping for more than that on my install, but actual usage will tell. However, good pointer to size the array. I agree mounting on the stern would more efficient, but my stern is rather crowded; radar pole, wind vane, and a couple of other gadgets, all hanging on brackets from the transom. Also my mizzen boom overhangs the transom by about 40 cm, so brackets are rather large to provide radius for the boom and sheet to move on the traveler. Not an option for me either.
At the moment, tending towards 18 V panels connected in parallel. Two arrays of 180 W (100+80) on either side of the roof, each with an MPPT controller. Expensive… over 1000 GBP BOM, and that’s off eBay! 
…plus my labour…
From what I remember, if you’re going to run multiple panels off of 1 controller, you would need blocking diodes, which drops the voltage by 0.7V, to protect a panel which was shaded. I’m not a solar expert in any way, shape or form, so I searched the Internet for this and this may help: https://www.coastalclimatecontrol.com/index.php/blog/140-marine-solar-panel-planning-guide.html. I needed flexible panels to mount on my hard dodger and due to the size requirements went with Soliban, which are quite pricey and thus the addition of second Genasun GV-4-MPPT was minor compared to the total system cost. My controllers are about 5’ away from the panels.
I used Bruce Schwab to determine equipment and found Bruce to be very knowledgeable. Here’s a link to the controllers that I used, but the rest of the site has a lot of good information. https://www.bruceschwab.com/genasun-gv-4/
– Geoff
Great discussion. I recommend calling or emailing Hamilton Ferris. They can design/recommend a workable solution at what I think is a good price. They provided a great recommendation for me with my Sabre 34 for offshore Experiences- again, like Mike said - only run the engine when AP is heavily used. (No refrigeration). Once I installed the system - single 150wflexible panel snapped to my soft dodger with a mppt controller - did not connect to shore power for next 2 years. (Full electronics - radar, AP, wind, speed, depth, vhf, LED lights, etc.)
I will seek their advise in my current F35(P) - currently running single fixed stern mounted panel at 80 w to a controller - not to my electrical panel breakers. Good for sf Bay. I will upgrade. Also again not connected to shore power for 1 year.
Hi everyone
Ok, here it is finished, at last!
Boat. Freedom 30 CK (Hoyt), '82
Total Panel Output; 400 Watts nominal in total
Panel Size: 1050 X 540 mm each. Have four in all, installed in two separate arrays.
Panel Location: Cabin roof. Location was determined by lack of space elsewhere. However, required re-directing all the rigging from the main mast, which run along the middle of the cabin roof. There is quite a bit of shading from booms and sails. How much exactly, I still can’t ascertain in watt terms. In sizing the array, I allocated 20% wattage loss caused by shading. Only foreseen potential problem is the occasional need to step on the cabin roof. Panels are supposed to cope with this though.
Type and Brand of Panel: Elfeland, 100 watt nominal each, monocrystaline, semi-flexible. Have to be, as they needed to fit on a slightly convex coachroof. Chinese el chippo panels, bought on eBay.
Total Cost: About 800 GBP in total. This is only HW - not counting my labour!- Panels were 400 GBP for four. This is for the array.
Measured Efficiency: So far happy in the sense that, moored in a marina but living onboard, the array supplies in excess of daily budget (including running the fridge 24X7). Managed to get 7 Amps from each array (i.e. from two panels) in full sunshine. In October, in the UK, that’s not bad. Expect at least double that in any climate fit for human habitation. Anyway, very happy not to have to connect to shore power (or run the engine) when moored!!!
Install: Four 100 Watt nominal panels connected in parallel and wired in two separate, independent arrays; port and starboard respectively, each with its own controller. Reasons for this design are: (1) wish to have 100% redundancy in case of critical failure in one of the arrays, (2) simplify and minimise wire runs to the batteries. In my case, I have two banks of domestic batteries (2X 110 Ah), under the port and stbd bunks respectively. There is a circuit breaker isolating each panel, and a 30 Amp breaker before each battery bank.
…and… absolutely many thanks to all that contributed and offered advise and experience. If the thing is a flop, it’s entirely my fault! 
Looks good! Lots of luck (and sunshine)!
– Geoff
Relating to the location of the controller, you typically want it as close to the batteries as possible especially if your panel voltage is high. My panels output at 48V thus the wire size required to minimize voltage drop at 48V is much lower than at 12V. So big $ savings in keeping the longer wire runs at 48V!
If you have multiple panels that will be shaded differently at different times of day, you are much better having one controller per panel as it will allow them to extract as much as they can from each of the panels. If however the panels were to be installed in a location where they are never shaded, then one controller is fine. If using multiple controllers, do make sure that all the controllers are setup with the same charging parameters as otherwise one might switch to float and basically shutdown while another one is still in absorption.
Good luck!
Thanks Pierre Andre!
Agree with you. Being connected in parallel with 12 V battery system, the voltage will not be too high. Re shading, with panels on that location, I’ve given up trying to model and predict the loss of efficiency. Too many variables interacting in different scenarios! Will have to manage on a daily basis. This was one of the reasons to place the controllers in an easy to see location, where I can monitor charging at a glance, without having to move cushions and open under bunk lockers. I makes the whole install inelegant and looking like an amateur job (which, strictly speaking, it is), but hey… mine is a very practical boat! 
A question from someone who knows little about solar.
I know one could put flexible panels on a sunbrella bimini. Has anyone put non flexible panels up and used that as the shade for the bimini? Would that hold up as it seems that you could get a lot of panels up that way for high output. I was thinking 3x300w.
Hoping to revive this conversation chain. Any thoughts on a solar set up for an F38. Thinking of the bimini arch but it is not very strong. Flexible panels on the deck will probably be impacted by shade. Has anyone found a stronger arch that fits the F38?
I definitely want to install solar for next season, hoping for some good advice from those who have done it already.
Philip
F38
Trinity
Manchester, MA
Hi Philip,
Another member of Blue Water Sailing Club and I did a presentation on solar panel installations last year at Jubilee Yacht Club. I am attaching half the slides as pdf’s now and will follow with the second half. Bernie designed everything from scratch. I went with a package from a dealer. I have 2 50 watt flexible panels mounted on the dodger with velcro sewn to the panels and the dodger. They are invisible to most people and have staid on during 40+ knot winds. I went with two so one was not shaded when the other is.
Blue Water is active in this area. Web site is bluewatersc.org. Two weeks ago, we had a program with Nigel Calder. Get on the mailing list or become a member for other programs.
DIY Solar & Refrig-part1.pdf (8.68 MB)
Here is part 2 of the slides. May work better with commentary
DIY Solar & Refrig-part2.pdf (9.97 MB)
Thank you, Stephen. Nice presentation.
At your suggestion, I have also applied for membership to the Blue Water Sailing Club.
Philip
Philip, suggest you also check a thread titled “illustraded guide to solar installations on boats” on cruisersforum.com. Lost of useful practical examples and info. Worthwhile spending some time there, IMO.
Cheers
Rafa