The good folks over at Ocean Planet Energy are selling these foldable and portable solar panels.
A couple of these will provide a cruising boat with around 100 amp hours at 12 volts over the course of a reasonably sunny day at anchor.
To me this is a way better idea, at least to supplement a reasonable number of fixed panels, a good cruiser’s alternator, and possibly a hydro-generator for offshore use, than festooning a boat with a huge unseamanlike fixed solar array.
Might even get one of these for our J/109, and I also think this, or something like it, could be a great solution for many Adventure 40 owners.
Our 150 watt panel, installed horizontally above the Bimini with no shade, give us a maximum of 30 Amp-hours per day here at 15 deg North
Thanks for the real world numbers. I did wonder if that estimate of total Ah was a bit optimistic. That said, surely your panel will get some shading from the mast and backstay over the course of the day? Also those portable panels can be inclined to the sun, which might help them a bit. On the other hand they will get some shading too, so probably a wash.
Anyway, the key, and valuable, point you make that the difference between theoretical output and actual over a day is huge.
I am a little surprised by how low an output you are recording unless you only cruise in the short days of winter, you are 24V or something. We have an older Kyocera 140W panel with ±30° manual tilting capability through a Victron MPPT controller and on normal sunny summer days average around 60 Ah at 12V nominal and have peaked a little over 70 Ah in a single day near the summer solstice. We are located at 42N so on average should have less solar potential than you.
Have you read the max current coming from the panel on a perfectly clear sunny day with the sun directly overhead? If you are not seeing right around the panel’s rating, then something is wrong. A tiny bit of shading such as a backstay can provide a shocking drop in output and I know several people who have thought there was a panel problem when instead they had something like a spare halyard tied off in a bad way. Since you mention the panel is above the bimini, if it is a flexible panel and has been flexed too much, it may well be damaged and not really putting out. One other thought is that there are plenty of apps and online calculators that let you plug in all your parameters and they pull the climate data and give you a predicted output assuming you are not load limited so you could check one of those against your real world numbers.
Why would you not install a semi-flexible panel in the same location? I bet lunch it produces more power because it will be exposed for 3 times more hours, because you don’t have to fool with it or forget to put it out.
Yup, I like hard panels, but unless you have a big hardtop (cruising cats) using deck space with semi-flexible panels makes a lot of sense. I installed a semi-flexible panel on the companionway turtle several years ago, and while it sees some shading, it is there, making power, all day. I would also bet it will last as long because it will see less flexing and handling (flexing is the leading cause of death of Bimini panels–micro cracking of the cells).
A bunch of reasons, but the main reason is that I do not consider the semi flexible panels, even those that claim non-skid to provide safe footing, therefore I believe they should be limited to very low traffic areas, and certainly not be used on, for example, the foredeck.
Other benefits of the portable are easy installation, being able to incline it, being able to move it to a better place to avoid shading, and air space underneath which will enhance cooling and up efficiency.
So I can see a use for these, although I agree that semi flexible have used too.
Do you have a recommendation connecting these folding panels to your house banks for charging? Especially if you might want to move them to different locations throughout the day?
We have one that’s used to charge our electric outboard battery and laptops but I couldn’t figure out a reasonable way to direct the power to the house bank. Likely I’m missing something obvious and would love a hint!
This was just a tip about an interesting option, so I have not put much thought into the details. Seems like you could have a waterproof plug and socket around amidships and the use a wandering lead to connect the panel to it. Just make sure the wire is a heavy enough gauge to carry the current without undue voltage drop.