Rollable/stowable Solar Panels

[marujosortudo]

Anyone have any preferences/experiences as far as rollable/stowable solar panels go? Any thoughts on durability? I'm thinking of constructing a bimini/shade cover that's mainly composed of solar panels and easily stowed. It would be primarily for use on the hook. My alternator should be able to fulfill power requirements when underway (coastal cruising with plenty of time in the ditch); although I would probably make the panels detatchable so a few could be lashed down on deck underway where they wouldn't cause too much windage or noise.

Thoughts?

[sailingdog]

You're much better off with solid/rigid panels, since they are far more efficient than the rollable/flexible panels.

[RobertKWFL]

It depends on your power needs and the space available. Flexible thin film panels are about half as efficient as rigid crystalline panels so you'll need at least twice the space watt for watt. If the numbers add up, flexible panels are ideal for the uses you described and are very durable and weigh less. Thin film panels can also provide somewhat better performance in situations where there are small shadows on the panels, as often happens on a sailboat.

I had to go with rigid panels on my boat because even on a catamaran I couldn't find enough space for 120 watts of flexible panels.

[arisatx]

No first hand experience with them, but I have seen the Lyman Morse s/v New Morning (link) install the "bendable" solar panels from SunWare (link) that look promising. As I understand, this high-end boat is pure DC.

They're really not "rollable" per the OP's desired criterion, but if you crafted a rigid top on your dodger (as on the Valiants) I imagine you could permanently install these without the windage and w/o their being too obtrusive.

[marujosortudo]

I am certainly aware that crystalline panels are much more efficient when in full sun, unshaded and positioned at the proper angle. How often do these conditions actually exist on a sailboat, though? Also, aren't the demands on the system greatest when it's cloudy anyway? For example, I'll compare a Kyocera KCM85 and a Spectra Flex 32W. Based on their performance sheets, they generate 12 and 4.9 Watts/ft^2, respectively. Wow! Seems to go hands down the Kyocera, no?

What about real world performance? I thought this study was interesting, even though I could only read the abstract:

SpringerLink - Book Chapter

So, spec. sheets indicate a performance ratio of 2.45:1 (watts/area again), but a 12-month test on a fixed, unshaded, south-facing mount indicates a ratio of 1.62:1. Things are changing now, no? Now, what if the panels get shaded and/or are getting less than ideal light most of the time (diffuse light from clouds or no southerly positioning)? Even harder to quantity, what if the light weight and lack of hardware needs of the flexible panels lets you mount them almost anywhere and get them out of the shade? I would love to have data on this, but I'm guessing this ratio might lie in the 1.2:1 to 1.4:1 range for a 12-month period with even better performance on cloudy days (i.e., when you really need it!) Of course, power draws like fridges will be running more on sunny days so better performance in full sun has advantages, too.

Then, there are all the other considerations. Weight, windage, stowability, flexibility in charging configurations, safety, warranties, cost, additional hardware required, etc. I like the idea of easily being able to remove all panels and hardware and stow them below in my limited stowage space. The performance of amorphous panels in terms watts produced per weight carried seems unbeatable. Also, the apparent cost advantage of crystalline panels gets obliterated if you mount them on some serious hardware like a Solar Stik. I don't need anything more to mount an amorphous panel then some extra line. If I can figure out a way to make a solar panel bimini that goes over the boom when on the hook with relatively no extra fabric and hardware, then further savings on cost, weight, and stowage could be achieved and shading would be minimal. That's the dream anyway. I haven't figured out the details, yet.

Regarding the SunWare panels, they have the performance you'd expect from crystalline panels and the large number of cells per panel means that their shade performance is probably much better than say, the Kyocera above. As far as Watts/$ though they cost about as much as a full rollable model. So, if you don't mind taking up the extra space on deck, the rollable ones might have a few more options for mounting and stowing. That's my thinking, anyway.

Other thoughts?

-Colin

[donradclife]

My personal experience with flexible panels is a bit dated, but the one we had lost 80% of its capacity in the first 18 months, whereas my hard panels have lost less than 20% capacity in 15 years. Don't believe the marketing claims--ask for a 10 year warranty and see what they say.

[marujosortudo]

Don,

Durability is a primary concern. I don't want to be buying new panels every couple of years . The rollable panels only carry 1-2 year warranties where the rigid panels carry 15-25 year warranties. Of course, I'd really like to hear what experience people had with these newer, flexible panels holding up. Do you remember what brand/model those panels were that you had trouble with? How long ago was this?

Thanks, Colin

[wind_magic]

I've considered it ...

I have some folding panels but they are used for camping where you can't really take a full sized panel. The folding panel seems to work well, I like it, but of course it is of limited usefulness because of its size. They do make larger panels, however.

For the boat I think folding panels could be useful. Besides being a replacement for normal panels (an expensive replacement) you could also use folding panels in ways that you can't use regular solar panels. Many of the folding panels have metal eyes on them so you can hang them up, are lightweight, etc, anyone for a solar panel riding sail ? How about hoisting some folding panels up with the halyard for a little extra power ?

I think something that is going to eventually become big for boaters is using cheap very thin panels as a layer when laying fiberglass. It would be very easy to glass thin flexible panels directly into the boat under some clear, even if it isn't much in terms of power at least it could be enough to keep the clocks set to the right time, or run the burglar alarm or something.

[RobertKWFL]

I wouldn't expect to get any meaningful power generation from solar panels on a cloudy day. These are full sun power sources. For power on a cloudy day, consider installing a wind turbine. Or go with both and you'll have power whenever there is wind and/or sun.

[donradclife]

We bought a flexible panel from West Marine in 1992, but can't tell you the brand. By the end of a year's cruise it was yellowed from the sun--must have had some epoxy coating vs the glass they use in rigid panels.

Unless you hear differently from some actual users, I think that you should not assume the panels will outlast their warranty periods, expecially if they are exposed to the sun daily.