Tape for Flexible Solar Panel on Roof

[Alex Adams]

One of my projects next year is to mount a 100 watt flexible solar panel to the roof of my trailer. I am planning on using tape to secure it. Has anyone used that Flextape stuff advertised on TV? Any other recommendations for tape to use including double-sided? I plan to put the double-sided tape at the 1/4, 1/2 and 3/4 positions on the back of the panel and then use the Flextape or other product to seal around the edges.

[rbryan]

Jim Bennett installed 4 of the flexible panels on the roof of his new 5.0TA a while back. He used Eternabond tape to secure them. He recently posted that the tape seems to be holding up well. Here's the url on the Escape Forum.

http://www.escapeforum.org/forums/sh...ad.php?t=10273

[Raz]

3 M Very High Bond tape has been used by many. But before you start, research gel coat separation using the search feature. As I recall Escape had some issues early on. Bolts are more secure with the obvious hole through the hull down side. I chose not to do a roof install. I bought two panels and hinged them. Folded, they ride nicely against the back wall of the pickup when not in use. Good luck with your project. Raz

[rbryan]

Originally Posted by Raz

3 M Very High Bond tape has been used by many. But before you start, research gel coat separation using the search feature. As I recall Escape had some issues early on. Bolts are more secure with the obvious hole through the hull down side. I chose not to do a roof install. I bought two panels and hinged them. Folded, they ride nicely against the back wall of the pickup when not in use. Good luck with your project. Raz

Escape did have 2 or 3 panels detach from the gelcoat but those were aluminum mounting rails epoxied to the gelcoat, not taped. Secondly, that was on raised rigid panels with frames, where winds exert a considerable amount of force on the mounts.

Since the OP intends to use flexible panels resting directly on the roof, bolts or other mounting hardware are irrelevant, and wind is not a factor.

A high bond waterproof tape (such as the Eternabond roof sealer I mentioned above) should do a good job of adhering such panels. Check out the thread I linked above from the Escape Forum for photos.

[trumpetguy]

I have 5 100 watt panels attached to my Airstream with 3m VHB tape. 9000 miles so far and no way to pull them off. I smothered the feet with Sikaflex after the installation.

Caution about the flex panels though. They tend to cup where the cells are and collect dirt. Also will the movement of the panel caused by lift eventually destroy the panel?

[rbryan]

Originally Posted by trumpetguy

Caution about the flex panels though. They tend to cup where the cells are and collect dirt. Also will the movement of the panel caused by lift eventually destroy the panel?

Good points about flexible panels. I guess the cupping or lifting depends on the panel.

[Alex Adams]

Originally Posted by trumpetguy

Caution about the flex panels though. They tend to cup where the cells are and collect dirt. Also will the movement of the panel caused by lift eventually destroy the panel?

That's why I was thinking of putting double-sided tape at the 1/4, 1/2 and 3/4 lines if you divide the panel along the long length. That would keep the panel from "flapping". Only 1 foot sections would be subject to being pulled off the roof. I think that would be more than enough support to keep flexing to a minimum.

[David B.]

I had two 100 watt semi-flexible Renogy panels VHB taped to the front of our Lil Snoozy, and I tell you that it was almost impossible to remove them 2 years later. I don’t know if it was just a bad batch of panels, or if it was the fact that they did not have any airflow under them that caused them to drop from 18.5 volts in the cool morning sun, to just 5 volts when the sun was at it’s peak. Renogy gave me a total refund, so I just purchased a conventional aluminum framed 160 watt panel from them and VHB taped it via Renogy’s mounting system for fiberglass roofs. It’s been holding up well now for over a year and about 6,000 miles.
Dave & Paula

[Alex Adams]

David, I didn't consider that!

Has anyone else experienced this with the flexible panels?

[Jim Bennett]

Originally Posted by rbryan

Jim Bennett installed 4 of the flexible panels on the roof of his new 5.0TA a while back. He used Eternabond tape to secure them. He recently posted that the tape seems to be holding up well. Here's the url on the Escape Forum.

Solar Installation - Escape Trailer Owners Community

Yep, still holding strong. This reminds me I never posted here about my solar setup.

Originally Posted by trumpetguy

Caution about the flex panels though. They tend to cup where the cells are and collect dirt. Also will the movement of the panel caused by lift eventually destroy the panel?

The newer type like I used in the link above are not supposed to do that, and show no signs of it near a year later.

Originally Posted by David B.

I had two 100 watt semi-flexible Renogy panels VHB taped to the front of our Lil Snoozy, and I tell you that it was almost impossible to remove them 2 years later. I don’t know if it was just a bad batch of panels, or if it was the fact that they did not have any airflow under them that caused them to drop from 18.5 volts in the cool morning sun, to just 5 volts when the sun was at it’s peak. Renogy gave me a total refund, so I just purchased a conventional aluminum framed 160 watt panel from them and VHB taped it via Renogy’s mounting system for fiberglass roofs. It’s been holding up well now for over a year and about 6,000 miles.
Dave & Paula

This is why I used the Eternabond tape. Although it holds like crazy, it can be cleaned of with some effort. I have been getting fairly good current off mine, though have not really tested them, and often am in partial shade. I set mine up in pairs in series putting out 36V, and have never had much of a voltage drop, just a current drop.

I never expected them to get anywhere near their full potential, figuring that if I got 50% in good sun I would be happy. I have an 80W portable to supplement if necessary.

[Raz]

Originally Posted by rbryan

Since the OP intends to use flexible panels resting directly on the roof, bolts or other mounting hardware are irrelevant, and wind is not a factor.

.

Solar panels are semiconductor devices. When you heat a semiconductor it changes it's electrical characteristics for the worse. Raising the panel allows for good air flow and keeps the panel cool. At that point wind does become a factor and bolts become relevent.

[rbryan]

Originally Posted by Raz

Solar panels are semiconductor devices. When you heat a semiconductor it changes it's electrical characteristics for the worse. Raising the panel allows for good air flow and keeps the panel cool. At that point wind does become a factor and bolts become relevent.

Yes, I'm aware of airflow and heating issues, but it's not practical or advisable to raise a flexible panel, even if you devised a mounting system to do so. The wind would make it flap and probably rip it apart. Since they're not rigid, and have no frame to mount a standoff, they're designed to be surface mounted, at least every one I've ever seen. An exception to surface mounting it might be when it's used as a portable panel, but that's not the OP's plan.

[Raz]

Originally Posted by rbryan

Yes, I'm aware of airflow and heating issues, but it's not practical or advisable to raise a flexible panel, even if you devised a mounting system to do so. The wind would make it flap and probably rip it apart. Since they're not rigid, and have no frame to mount a standoff, they're designed to be surface mounted, at least every one I've ever seen. An exception to surface mounting it might be when it's used as a portable panel, but that's not the OP's plan.

Panels are designed to operate at 25*C. A typical derating figure is 1/2% reduction in output for every 1 degree increase in temperature. I'm sure you will agree that if the panel doesn't produce the voltage required then the stability of the mount is irrelavent. The op may want to consider that in his plan. Raz

[Huck]

I used VHB tape to install a Renogy 100 watt flex panel on my Parkliner about 3 years ago. Still holding fine.

[Jim Bennett]

Originally Posted by Raz

Panels are designed to operate at 25*C. A typical derating figure is 1/2% reduction in output for every 1 degree increase in temperature. I'm sure you will agree that if the panel doesn't produce the voltage required then the stability of the mount is irrelavent. The op may want to consider that in his plan. Raz

This heat factor then is very small. For starters it is rare for me to camp in temps over 25°C, and if I am it means there must be lots of available sunlight, so though my potential collection drops a wee bit, the amount of available light increases more than enough to offset this.

I have seen similar loss numbers in the past, but lots of changes are being may to solar panels these days, just look at the advance in the semi-flexible now to the ones like I used. Heck, in 5 years they too might be obsolete with even better ones out there.

Nonetheless, if you took my potential for 240W at 25°, and raised the temperature to 35°C (95°F), you would lose 5% of the max capacity, resulting in 228W. Not that much of a loss or of concern for me, especially given the fact I will be desperately looking for 120V to run my A/C at those melting temps.

Seeing the main reason for me to have solar is to provide enough power to run my furnace, high temps are not that much of a concern. Even for those in warmer temps, the need for solar power collection at high temperatures is not very high. Running a DC compressor fridge might be a good reason though.

[Raz]

Remember there are other reasons for voltage loss; angle and loading are two that come to mind. Every little bit hurts. With 36 volts I'm guessing you have series connected your panels and are using an MPPT controller. Not the most efficient approach but that gives you a lot of wiggle room. David Trumpet Guy has the perfect trailer. Aluminum is what heat sinks are made of..

[rbryan]

Raz, the efficiency and temperature issues aside, I still don't understand what you propose. The OP is looking for a tape to adhere their flexible panels. If you are suggesting going with rigid panels that's fine, but if the flexible ones, what mounting solution do you propose other than surface mounting them?

[Jim Bennett]

Originally Posted by Raz

With 36 volts I'm guessing you have series connected your panels and are using an MPPT controller. Not the most efficient approach but that gives you a lot of wiggle room.

Correct, I have two pair of series connected panels, and my portable is in series too, all going through an MPPT controller, which is a must with this voltage. It actually is more efficient than having all four panels parallel, with amperage cut in half. I admit the line loss is very small though.

Like Robert alludes to, these panels are made to be mounted flush. I love that they are not at all visible from ground level. Some sort of surface mounting is required, and after a lot of researching I decided on the EternaBond tape as a strong, yet reversible solution.

[Raz]

Originally Posted by rbryan

Raz, the efficiency and temperature issues aside, I still don't understand what you propose. The OP is looking for a tape to adhere their flexible panels. If you are suggesting going with rigid panels that's fine, but if the flexible ones, what mounting solution do you propose other than surface mounting them?

Ah, put me on the spot. Very good. I'm really not proposing anything, just pointing out the pros and cons. When I went through the exercise my solution was a folding panel unattached to the trailer. Storage and theft are the obvious cons.

Ever notice what happens when you drill a hole in your trailer with a twist bit. Unless you run the bit backwards you stand to have a chunk of gel coat separate from the fiberglass. That's my concern with tape. It relies on a good bond between the gel coat and the fibergsss. While a flat flexible panel might reduce that concern, the heat issue comes up. Not just voltage reduction but failure. And don't assume the panel is at ambient. Heat absorption and I^2 R loss come into play.

If I absolutely had to put the panel on the roof, a rigid panel on a bolted frame would be my choice. Of course putting holes in the roof ......

Nothing's ever easy.

[rbryan]

Originally Posted by Raz

If I absolutely had to put the panel on the roof, a rigid panel on a bolted frame would be my choice. Of course putting holes in the roof ......

Nothing's ever easy.

Thank you for the clarification. A rigid framed panel is my preference too, but that's obviously not the case here.