Solar Panel Advice

[Sunbeam]

I would prefer two 50 watt panels instead of one big 100W panel (i.e. if the 100W was split lengthwise). I think that this would be easier to install on the CD22 given the lack of large open spaces. I would put one panel on each side of the center roof bump (outside the rails).

Solarland's SLP 070 (formerly 065) is long and narrow (~13" x 58"). That said, I considered/measured with the idea of placing them where you say on the 22 and still felt it would be rather big/awkward for going forward. I think that instead I'll put panel(s) on the center of the roof. Yes, if I put a kayak up there they will be shaded, but I figure that would mostly be underway, when I have the engine alternator going - or at short term anchorages where I have enough power left over. For longer anchoring times I'd likely have the dinghy (kayak) down and so the panels would not be shaded. Granted all the locations are going to have their plusses and minusses. Another thought I had was a hard topped bimini with panels above, but, I think I like the option of folding the bimini...

 

[rogerar]

THANKS for the info, I have been searching for a long time for narrow panels, also they are Marine Grade, I can get a pair shipped to FL for 500.00, plus a Dometic Freezer around 650.00, better start saving!
Roger

 

[bcassal]

I recently installed the Renogy 100 watt bendable panel on Carpy and am very pleased with it. It is about 43 x 21 inches and 1/8 inch thick!.
Pics in my album

Bruce
Carpy

 

[Pat Anderson]

If I did not already have the aluminum frame panels, I would get a couple of these Renogy bendable panels. More durable and easier to put on and take off, more mounting options for sure.

 

[colobear]

Bob,
You asked for sun and night voltage output from the panel. With no load and at a 3' pigtail: Direct sun: 20.7V, bright overcast 19.02V, night (w/some ambient light) .59V.

 

[Sunbeam]

If I did not already have the aluminum frame panels, I would get a couple of these Renogy bendable panels. More durable and easier to put on and take off, more mounting options for sure.

I'm not sure if the flexible panels AM Solar has been testing are the same exact ones, but they did not sound "good in the real world" yet to me based on their testing. Although it would be nice if they were! Here is what they found:

http://www.amsolar.com/home/amr/page_25 ... panel.html

We have had these on the roof of our RV since June of 2013. They are made with SunPower's back contact cells (like the ones we use in our GS100 solar panel). We used 3M VHB tape to hold them to the roof and that seems to work well so far. They worked very well during the summer months when the sun was high. However, we have noticed a fairly dramatic drop off in power with low angle sun during the winter and early morning/late afternoon sun angles when compared to the output of the glass/aluminum GS100.

The most serious problem we noticed was during a spell of 90 to 95 degree temperatures last summer. The thin covering over the cells (3mm thick) was not sufficient to keep the cells from "cupping". This, in essence, caused each cell to form a shallow bowl which collects dust that any moisture will push to the middle of the cell. When the water evaporates, there is a small circle of dried mud that blocks enough sun to cause a power loss.

Simply spraying them with a hose didn't completely remove that spot. I had to use a soft brush to scrub it off and then I noticed I was actually scratching the plastic surface of the panel (made from a UV resistant P.E.T. or "polyester"). Scratching the surface means less transparency which means less light hitting the cells which means loss of power.

Given that they scratch easily, have reduced output at off angles of the Sun, cupping cells from high heat and a limited 10 year warranty. We consider them "Not Ready for Prime Time". We are working on ways to address these problems and will offer them for sale when we have something we can heartily recommend.

Some sailing acquaintances are very happy with their Solbian brand flexible panels. They have zippers on them and zip right onto the top of their canvas bimini.... sweet! (Or you can use velcro or other means.) But they are extremely expensive (now) as compared to rigid panels.

There are also some "stick on like tape" type panels that sound pretty good; but you need yards and yards of them for the equivalent output as the rigid ones (again... now). Some folks I know with large Class A's (lots of roof) are using them.

 

[thataway]

I don't know if this applies to the flexible solar panels, but I was cautioned on my RV panel to have it spaced at least 1/2" off the roof, to allow for air circulation and avoid excess heat build up. (Also allows you to wash under the panel.) The panels on a Bimini top would have that ventilation. It would also be less likely to be shaded--and might allow for sun orientation during the day to some degree.

 

[bcassal]

My Renogy panel is sitting in the Hoosier sun with no issues so far. It is completely open underneath. I think an air space is a very good idea.
As far as the cost: My panel, controller and wire cost less than $250.

Carpy

 

[Pat Anderson]

If you notice from the photo, my Renogy aluminum frame panels are mounted on 1/2" "plastic wood" pieces that raise them off the wings, and allow air to circulate underneath. This was not by design but resulted from wanting a mounting system that allowed me to put them on and take them off easily. But I guess it is for the better!

Anyway, since I have them, I will stick with them, no reason to move to the bendable panels, it just seemed they offered some advantages - but maybe not.

Pricewise, my two Renogy 100 watt panels plus controller were $379, free shipping and no tax. Not much more for a few MC4 cables, probably spent about $20 on those. The wires back to the batteries from the controller are the same wires that used to power the Wallas. These are about the heaviest gauge wires going forward from the batteries. A very economical system, even considering the $158 for the Victron Battery Monitor, which I consider just about essential if you want to know what is really going on and are using your solar for more than just "topping off" charging.

 

[chriscarrera]

Just took delivery of my Renogy 100w flexible panel, waiting for the genasun charge controller, then will install.
Looks like it will lay on the camper back right at the junction of the cabin top.
Not ideal but that is where it will go. Pics when I get it done.

 

[thataway]

I read last night that the panels are 10% more effective with an air space under for ventilation and cooling.

 

[journey on]

The comments here are interesting. What people are seeing is the way solar panels operate. Here's how solar panels output power and the consequences:

Pat, sorry to use your panels as an example. But you've given some numbers and a picture. Apologies in advance.

1. Heat decreases the solar cell efficiency. The rated output is tested at 20 deg C, 68 F. So if they aren't cooled by air flow or radiation and they get up to say, 100 F they lose power. And that's the cell temp, not ambient. Feel them when they're putting out power, they're warm.
.

2. They have to be pointed at the sun to put out maximum power. One may not remember trig, but the output falls off as the cosine of the angle between the sunliine and the perpendicular to the panel.. Looking at Pats installation, there's first ~30 deg of difference between the panel mounting from side to side. So, if one panel is pointed at the sun, the other is down by 14% (1-cos of the angle.) Also, the panels lie flat on the roof. To be perpendicular to the sunline they need to be tilted to the suns elevation. tis is the latitude (48 deg) + declination (23 deg at this time of year.) That's another 10% at this time of year when the sun is at its highest. In addition, Pat's installation is only getting max sunlight at noon, when the sun is directly overhead, say between 11 am and 1 pm. Again the cosine of the angle.

3. The solar panel rated power is given from flash tests and is at maximum power, which is for Pat's panels, 17 volts. By hooking them to a battery, you're reducing the power by decreasing the output voltage to 13.5 VDC. So those panels are 160 watt panels at battery voltage when cold. The current stays approximately the same. Solar inverters track the peak power point to run the panels at max output. The cheap regulators just turn the current on and off to maintain the battery voltage. That's what I have on the 25 watt solar panel which maintains the truck battery.

So Pat's numbers of 5 amps at 13.6 volts give 68 watts. Pointing those panels is one solution. Letting the breeze blow on them is another. Look at commercial solar farms. The panels are mounted on posts and track the sun. While we on boats can't do as well, we can do the best under the circumstances.

So, Pat's panels are doing what they're designed for at 68 watts.

Boris

 

[jkidd]

I've been experimenting with 4 Goal Zero portable panels that I take with me with the trailers or the boat. I have an Engel 45T Fridge. One panel will pretty much keep up with the fridge and two will keep the battery charged nicely. The only time I have to put all four out is when the weather gets bad. When I use them with the trailer they mount on a tripod so I can sit in the shade and move the panels to the sun. On the boat I have just been hanging them off of the boat some where. I made a board so I can put them on the bow and turn them at the sun. Of course at Lake Powell back in the backs of the canyons if your trying to hide from the sun there might be a small problem. You should be able to get enough time during the day to get the batteries topped off.