Solar Panels, Panneaux Solaires ....

Yesterday I received the following question from a friend:

We have a small technical question: We are in Martinique, consulted an experienced technician on the efficacy of our solar panels and were strongly advised to put the radar in front of the mast to prevent the shadow problem which cuts the electric production very heavily. Would you please advise us where in the mast the best location is? Next to the lower spreaders? Higher? Do you advise a certain brand of mounting piece? Can you give us any hints whether our cable will be long enough or what size cable do we need to order ( or maybe connect a piece by soldering). We also plan to add a flexible and transportable solar panel to use in . Until few years ago their capacities were limited, lately I have read a test in a British journal telling that 70 Watt panels are working efficiently. Do you have any ideas? How did you rig Hanami II for electrical production for the World ARC? Thank you very much for all your help

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Not too easy to manage even if the answer seems straight forward.

Here is what I came up with, of course, as usual,  it needs criticizing and comments.

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Hi, good morning to both.

I hope you enjoy some sunny weather in Ste Anne and have a good time on those beautiful beaches.
For the solar panels, I think the advice you were given is right.
Solar cells are linked one to the other in serie and any shadow or dust will either cut the circuit or reduce the output.
To boot, the panels should be strictly perpendicular to the solar rays for maximum performance.

Here are some of the possible consequences for the panels:

• The panels must not receive any shade from the main sail.
• They should not be in the shade of the wind-vane or any other device located on the arch, including the radar dome. This is why you have been given the advice mentioned and why wind vanes are often located on a mast bent backward toward the aft of the boat.
• They should be installed on articulated frames, allowing for good orientation. Of course this will be limited as it is very likely that compensation for the tilting generated by the boat heeling will be impossible. This is a very important factor as the loss is depending on the sin of the angle and a variation of more than 20 degrees will be significant as seen on those two diagrams I extracted from french web sites, one being cipcsp.com

• Additionally, solar panels rarely deliver the total output expected as it is depending upon the orientation and tilting of the panel but also on the temperature, ideally 25°C and at noon the loss can be 10%
• This, of course is only during day time and when the sun is high in a clear sky and dusk, dawn and clouds won't help of course.
• There are indications that solar panel could deliver less, at least some of them, it the temperature is too high and this may happen in tropical zones. All manufacturers give a diagram of the SP output (Amps and Volts) against temperature and when the temp increases, the curve is shifted to the left: the Amps are stable but Volts diminish which is bad for charging batteries.
• If there are multiple solar panels, it is crucial that each of them is protected by a "diode" as a panel in the shade, hence not delivering anything, would drain what comes from the others. Same mechanism for batteries: the empty one drains the full one. The down side of the diodes is that they generate a small drop too.
• From everything I have seen I reckon that the most you can get is 75% of the maximum theoretical output given by the manufacturer and this during the 4 or 5 best hours of the day. seems to be safe guess.
• Flexible solar panels installed on the roof can probably compensate for the shade generated by the sails and the heeling on one side provided that enough solar panels are located on both sides.

The only way I know to control what the panels deliver is to have them monitored in real time on the MasterVolt network,by connecting their regulator to the MasterEasy or even better by using a MasterVolt regulator. Of course any other manufacturer 's equipment having the same function will do the job.

Hence, installing the radar dome far from the panels, i.e. on the mast above the first spreaders, is quite an obligation.

On Hanami 2 the Furuno radar is on the mast and the mounting piece is from Furuno too and carefully isolated. The cable is a Furuno one, goes into the mast and the length is probably 20m.

I personally consider the solar panels to be almost useless on a long cruise, except when the boat is moored with plenty of sun and the panel regularly oriented toward the sun (then, some one must do it) or to keep the batterie topped up if the boat is not used for a long time with no shore connection. In a nutshell, I believe it is good to have them but, in my view it is unsafe to rely too much on them. They are additional to the other equipment but can't replace them. Consequently, for the World ARC H2 will be fitted with: 2 alternators already installed, one for the house bank and one for the start battery. 2 100w solar panels, already there too A new D400 wind turbine with an oversized tail to avoid tilting when heeling, A MasterVolt Whisper 3000 generator, installed before the 2011 ARC. A MasterVolt network with MasterEasy monitoring, Installed at the time H2 was built. 880ah of calcium/lead batteries, new from 2012. A Watt&Sea (cruise model) hydrogenerator to be installed by Alubat next month. An isolation transformer to avoid any issue coming from poorly wired pontoons.

It may looks like "belt and braces" but I want ot be on the safe side.

For fixing your issues, there is a very good and knowledgable marine electrician and MasterVolt contact in le Marin: name is "YES Caraïbes", they are located in the ARTIMER area behind the Carrefour supermarket and the pricing is reasonable. I am sure he may be able to help you as he efficiently fixed my electrical issues and was warmly recommended by MasterVolt France.

All the best and tell me what happen next.

M.