Shadow tolerance

[Hamma]

Hi,

Reviewing many of the solar panel threads, shadow tolerance is an issue for many boat-mounted panels. Is there some way to determine the likely shadow tolerance from the spec? Is it an issue caused by a style of manufacture?

I am planning on mounting mine on the coach roof and obviously shadow will be an issue there from time to time.

Should I be looking for a particular type of panel?

 

[VicMallows]

Generally, Monocrystaline and Polycrystaline panels (the rigid sort also used on fixed installations and homes) are more efficient, but very intolerant of any shade.

Amorphous panels (which can be rigid or flexible) are less efficient but more tolerant of a degree of shading.

As always it's a compromise. I use two 40W Monocrystaline domestic panels, one on each side of the boat and find I have ample power even though only one is usually working efficiently at any given time. (cost was £140 for the pair).

 

[noelex]

The greater the number of bypass diodes the better. 8 is very good but the cheaper panels often only have 3.

 

[WilliamUK]

Another option would be to go for several smaller panels.

As I understand it, a bit of a panel in shade reduces the output of the whole thing. It that's the case, a shadow cast on one panel in an array of panels would reduce the output of that one only while leaving the others working properly. More shade tolerance than a single large panel of the same output.

 

[vyv_cox]

I have Kyocera panels, 40 and 85 watts. We launched an hour ago and having berthed stern-to one of the first jobs was checking electrics. I was somewhat shocked to see only 2 amps, in blazing Greek midday sun. Climbing up to investigate I realised that the shadow of my neighbour's mast was right across the big panel. Five minutes later we were up to 6 amps when the shadow had moved away.

 

[William_H]

Solar and shadows

If you have the type of panel that is built in strips of semiconductor each strip being a cell then if the shadow falls shading one or more strips you will lose a lot of power. If you turn the panel so that shadows (of mast) tend to fall across the strips at right angles then you will get less reduction with a narrow shadow.
consider good luck olewill

 

[robertj]

I tend to agree with smaller panels situated in varying postions around the boat for the best
power, but, this is a lot of work with regard to wiring/fixing etc.
One yacht I have seen and chatting to the livaboard skipper advocates two panels situated on the cockpit area guard wires where the dodgers fit.
I have a 60w panel on a stern arch which I will soon be changing to a 100w panel (depending on cost of faulty Profurl Furler repair). My reasoning, is to give as much power while unshaded. The 60w panel will then be, a floating, best position addition, connected to a cockpit plug.

Bob

now to work on solar water heater

 

[Hamma]

Thanks for the assistance. I'm thinking of fitting this panel

I don't have the space (or capital) to install two smaller units although I can see the evident benefit in doing so.

Incidentally - this panel is about £620. There are similar output panels available on eBay for around 50% of that price. Is the price difference justified by anything?

 

[VicMallows]

Thanks for the assistance. I'm thinking of fitting this panel

IMHO that is incredibly expensive for the output. 100% mark-up seems quite typical of mainstream chandlers, so not surprised at the discrepancy you have found. Even at half the price you suggest I would be looking for other solutions.

Do bear in mind that the useful output you get in the UK will only be around half the quoted 'peak-power-output', and only then on a reasonably sunny day for about 6-8 hours.

 

[Hamma]

IMHO that is incredibly expensive for the output. 100% mark-up seems quite typical of mainstream chandlers,

Actually in this case Foxs are about £30 below the manufacturers' own web site price, so it seems this cost comes from the factory.

Ebay panels almost a third of the price. I know this issue comes up time and time again. I think I'm just going to buy the ebay one and see how I get on.

 

[tinkicker0]

Trouble is most generic solar panels are manufactured by the same company that produces Flux Capacitors and there is a built in unreliability factor in order to partially evade complex HMRC green taxes and partially to make the end user feel smug when he expends considerable amounts of time and know how in getting the device to work again.

BMW and Audi have also copied the smug factor in their marketing campaigns, so it must be recognised that same is a strong selling point in the key demographic, ie middle class professionals and travelodge dwelling salesmen.

Recognising this demographic crosses over neatly with the average yottie, the swindlers marketed a marine version of both the solar panel and the flux capacitor at double the price and half the reliability; realising that the smugness factor must therefore be off the scale with the opportunity to relate such tales of derring do on forums provided by Messrs IPC & Co such as PBO only adding to the enjoyment.

"I got enough power to light up the United States from my 10w monocrystaline panel with the simple modification of 2 elastic bands and a bit of ear wax" type posts not being uncommon.

Thus in these uncertain times, consumer satisfaction is restored and HM Guvmint can carry on doing what the chuff it wants without redress.

http://uncyclopedia.wikia.com/wiki/Flux_Capacitor