I was preparing to order semi-flexible 100W solar panels from Windy Nation early this morning, the same panels that Renogy offers. Six of ’em weigh about 25 pounds, versus three of the 195W panels from the Defiant that weigh 129 pounds to get the same wattage total. The Intrepid’s roof lift struts help a lot, but not that much!
Then I came across a post about how the cells on semi-flexible panels tend to cup (distort) on exposure to solar heat (pooling dirt), and that this deterioration is evident after just one year. That made me think about the usual warranty on these, which is just 5 or 10 years, and that’s a lot less than the 25 or 30-year warranty on rigid panels. Instead of glass, the protective coating is transparent plastic. When I then stumbled over a blog post detailing heat-failed Renogy panels and found that Renogy has pulled them from their product listing, that kinda caused a mental Chinese fire drill around here. The same panel technology is shared across the market, and other major sources for this type of panel have submerged as well.
Considering that I didn’t even order the Four Wheel Grandby pop-up until I could first be assured of a workable and fairly painless solar system – one which avoids an elaborate or laborious setup – such a revelation was unwelcome. The 12′-long Grandby roof is supported only at its front and rear ends, and the whole thing is something like 1-1/2″ thick, based upon a lightweight aluminum tube frame. That’s one reason why the factory limits its roof-mounted solar option to a single 160W solar panel, probably weighing about 30 pounds. Additional wattage is only available as a ground panel.
So conventional glass-faced solar panels pose no durability problems, but pose practical limits as to how much wattage can be installed on the largest Four Wheel’s roof. A warped roof can rarely be made straight again. An inspection of my Grandby’s roof shows it to be more or less flat on top, until it tapers thinner about 6″ from the edge. That affects the mounting area available. If panel weights go up, some care needs to be given to distributing weight along the roof surface instead of relying on a few common point mounts. With the roof being interrupted by two big vents and a solar panel SAE outlet, space for maximum wattage is at a premium. Heavily loading the roof asymmetrically side-to-side would be hard on the main supports.
On the face of it, it will be a significant challenge to place just 400 watts of solar on the Grandby’s roof such that I’ll be able to lift it, and that it will not pose a risk to the roof in some way. I’m still unwilling to perforate the roof for fasteners at this point. The remainder of wattage would have to be made up with ground panels, or at least panels located off-roof. That, or of course chop battery capacity to more conventional levels.
One thing caught my eye, however. The fried Renogy panel was fastened down much as I planned to do mine, with 3M mushroom-head tape in small pieces at the borders. That spaces the panel up nearly 1/4″. I was going to add more along the centerline to help keep the panel center up. Looking at the fry marks on the roof in the blog photos, that makes me suspect that the roof surface may have contributed to the panel’s overheat by direct contact, instead of wicking heat away. The value of adding a few support ribs under the panel might help with isolating it, but the value of a mere 1/4″ air gap is probably debatable in terms of cooling air flow. The value of backing the panel with a sheet of Reflectix comes to mind to do the spacing, since it has air gaps and can reflect heat both ways, but I’m well out of my element here as far as figuring out all that would be going on. Study time. A thin layer of insulation may be more appropriate.
Bottom line – the solar aspect of the Intrepid is on hold until I can work something up. Just to complicate matters, the claim is out that a better panel design is being worked on, but when, how much improved, and cost make it difficult to decide whether to work up a stopgap and gimp it, or fake up a final system and just live with it.