I have planned to install my two 68-watt Unisolar flexible solar panels (self-stick) along the rounded edge of our motor home but before I do that I would like to run the pros and cons (mostly the cons) by the group to see what I've missed.
Pro: Flexible and should glue right down to the room on the round edges. I have already fit them and they adapt well to the curved surface.
Pro: Self Stick means that I don't have to drill any holes in the roof.
Pro: No need to go up on the roof to tilt these panels; they're already tilted.
Pro: The Unisolars work well in different angles of light and in shadows which means that if any system would be useful on a curved surface it would be a Unisolar.
Pro: One panel is likely to be in sunlight more meaning that it could operate more efficiently than a panel laid flat.
Pro: I only paid $75 for each of them so if they work then that's great and if they don't then it's not that big of a loss.
Con: One panel is likely to not be in sunlight more meaning that for two panels I only really get one useful panel under practical circumstances.
Con: If they don't work it might be a problem getting them off and where they are mounted could make for an unsightly mess.
Con: The movement of the coach through the air might set off eddies that I don't know about that could loosen them.
Con: They don't work with the sun behind them... which would be at least some of the time for each panel.
Con: They're only 12vdc but with an MPPT controller it's not that big of an issue plus I could also use a small MPPT controller in parallel with the existing charging system(s) for just the Unisolar devices.
Anyone else see anything? I am really most concerned with the way I'm going to mount them and the chances of them coming loose (or off) when the coach is moving.
Craig
Craig, it looks like you have it figured out.
I think you are being overly pessimistic as to the come.
These panels are claimed to work well at low angles of sun exposure. I tend to believe the claims. Yes, one will put out more than the other when the sun is setting, but still putting out some useful power.
As long as you keep your rig wheels side down, sun from the backside should not be a problem.
I've put about 1000 miles on mine at 60-65 mph and they appear to be staying put. If they do come loose, getting them off might be easy. These were designed to stay on roofs during commonly heavy winds.
One reason I went with a mppt controller is that I can connect as many panels as I want in series so long as I don't exceed the 150 volt maximum panel voltage. This allows you to easily add dissimilar panels.
Is current from each panel similar enough to avoid problems that might result from connecting the panels in series? Each panel would have to handle the maximum current from the panel which produces the most current.
I am only guessing at this, but I believe this will work as long as the panels are in the same ballpark. They use the same gauge wire and the same connectors, and I assume the same gauge interconnects and diode amperages. I makes economical sense in manufacturing to design for the top model in the family but use the same components for the entire family, at least within the same ballpark.
I'll let you know in a couple of weeks how well two Global 90W panels play in series with two Unisolar 136W panels.
Craig,
Looks like you are ready to roll. With a clean prepared surface, I don't think you will have any problem with the panels coming unstuck but checking every so often will give peace of mind. Yes, removing them might make a bit of a mess but unless the adhesive is super strong, I doubt if it will pull the gelcoat off. I didn't worry about holes in the roof as there are over a hundred when it comes from the factory and sealers are better today than in the '90s. Any kind of inexpensive controller will work with 12V. A MPPT controller will up the day's total by 10 percent or so. Lots of controllers of all types/prices on ebay and for not much $$ until you get into the high amp models. A 280 watt commercial PV panel like ours is available for $160 out the door. That make them even less expensive per watt. Mounting panels with an air gap above the roof will give slightly more output and the roof will be cooler in that spot with the sun high in the sky. With only one big panel, you could design a mount that would allow tilting it into the sun with just a pole from the ground and would get close to the maximum wattage out of the panels. As the panel gets closer to perpendicular to the sun, the output really jumps up. I you do use a MPPT controller, you can wire in series to cut down on the loss to the controller. Make sure to locate the controller as close to the batteries as possible or run a couple of welding cables from the house batteries to the controller. Be sure to fuse the lead, as close to the batteries as possible. I installed a couple of breakers, one set between the panels and the controller and the other set between the controller and the batteries with labels. Battery breakers switch on first and then the panel breakers. Shutting down, the panel breakers go off first and then the battery breakers. I used sets of two breakers as the amperage is high on ours. Solar breakers are not expensive and Northern Arizona Wind and Sun has both breakers and mini box to hold them. Other companies will also carry them. I mounted the box inside, rather than on the roof.
How about just putting them in place without peeling the adhesive backing off to test the system before permanently mounting?
If you decide on more panels in the future and dry camp a lot, I would look at an American product like the Midnight 150 as they have a long warranty and will get a replacement to you in a hurry. Even after the 5 year warranty, the cost is only $125 to do any repair or replace the entire insides.
Back from the South Pacific last night so PM or call me with any questions
Pierce
Pierce, et al...
I have two 240w 24vdc solid panels and the mounting brackets to even allow me to tilt them (although I am less enchanted over tilting as I grow older).
I also have two MPPT controllers; I bought a cheap 20A version and then decided to buy the Classic 150 for more options, better control, etc. The cheap unit will only do 12/24volt input for a 12vdc output. The Classic 150 is far more versatile.
The two Unisolar 68w (at 12vdc) panels I have now were purchased specifically to give the coach a little power no matter what direction we're parked. But because they are on opposite sides of the coach one of them is very likely to be partially or fully shaded so I plan to connect them in parallel to mitigate that shading effect. Even though Unisolar are reputed to be much more effective when partially shaded, connecting them in parallel further helps with that.
So we'll have, when we're done (with this round) two 240vdc (24vdc) solid panels in series and two Unisolar 12vdc panels (in parallel).
My other option is to stick the Unisolar panels down on the rooftop in series with the solid panels. Since the Unisolar panels can be walked upon (gently) that's certainly viable. Still thinking it over. Going to the RV today to make some dummy panels and lay them out to see what I like best.
Mounting the Classic 150 is something of an issue. I know you took part of your cabinets. I plan to remove a mirror from the wall against the cabinet and mount it there and routing the cables into that pantry and down into the battery box beneath.
Craig
Craig,
OK, have your installation in my head now. The Classic 150 will generate some heat, depending on the input so the mounting is important for a supply of air for the fans. Ours turns on the two smaller fans with moderate output with a third fan coming on as the output goes much higher. It can be sealed and will work OK, but the output will be lower. Translation; our little storage door has to be open while it is in operation unless just in float mode.
Excellent idea on the dummy layout.
I still have not connected the temperature probe but have six house batteries so figure I can't get them warm even at max output.
I went into the buss instead of the batteries for the 12V connections as it was much more convenient but that will depend on Foretravel model and battery location.
Pierce
I mounted my Tracer 30A charge controller on the equipment bay wall, below the inverter-charger, close to the fan, and a short run to the batteries in the next bay.
The DW and I had an "RV Day" yesterday. Along with a few other chores we created a "dummy" panel (from the box one of our panels came in) and used that to determine where we can mount the four panels we have (two solid 240-watt/24vdc and two Unisolar 68-watt/12vdc) and I'm glad that I didn't buy more panels last year. We have just enough room with our floorplan to put the two Unisolars along the edges and the two solids on. I'll have to eliminate the Wineguard TV antenna (which I have never received a TV signal over anyway) and substitute a "Jack" to do it, but it can be done and still walk to all the spots on the roof.
To do an install which will allow tilting the panels I won't be able to screw down the mounts so will be using High Adhesive 3M tape. I have a few ideas about this and will probably use an aluminum base-plate for the mounts (with recessed fasteners on the underside) to give a wider footprint for the tape to do its bonding work.
Glad I took the old satellite antenna and the huge storage box off. But now we forget to bring our lounge chairs. LOL
Craig
Craig, the VHb tape from 3M works great to hold those brackets down. Mine have not moved in over 2 yrs. All the wires and combiner box are held on with it. I do put some levelling sealer around them too.
JohnH
Thanks, John. I know you've mentioned that yours hold well before and that's one recommendation that makes me feel more secure about the method. One of our solid panels will be right at the front of the coach so I plan to make a wind-screen for it (like you have done).
Craig
Craig,
I was faced with the same clearance problem with the "bat" but turned it 90 degrees. Since we usually use the Dish Tailgater, I will probably remove it but that is another project.
Pierce
I have never managed to get a tv signal from the batwing even though it is the new HD version. I think a previous owner re-wired all the coax to accommodate a satellite system and I haven't expended enough time to trace it all out yet. Most of the time we're camped in a location where on-air tv is problematic at best anyway. We plan to go to a carry-out system so it's no big deal if we are not able to get programming for a few days. It's not like there aren't books. :D
Craig