Adding Solar Panels

[RockyMtnRay]

I placed an order today with RV Solar (http://www.rvsolarelectric.com/inform.htm) for their "Jumbo" (120 Watt) Solar Kit plus an additional 50 Watt panel. The kit comes with panel, 30 feet of UV resistant wiring, and a 16 amp charge controller. I had them add an extra 20 feet of wire to be confident of getting all the way to the battery compartment in the back of my TM (2720SL). Total came to $950 and since that was close to their free shipping minimum of $1000 (and I'm a really nice guy ), there was no shipping charge.

After discussing the TM's roof construction with the sales rep, he recommended pop riveting each panel's Z-mount (4 per panel) to a square sheet of aluminum stock (each at least 4 to 5 inches square) , then glueing the squares to the roof with either a marine adhesive or liquid nails. He said the marine adhesives (Plexus?) are stronger, more water resistant, and cure to a clear (or white) color. Now all I gotta do is find some marine adhesive in this town-of-very-few-boat dealers (or order online). Suggestions on the adhesive (and sources) would be most welcomed.

The plan is to mount these panels lengthwise in parallel on the curb side of the TM (with the shorter, 50 watt panel toward the center.

Will post more (and provide pictures) when the parts come in next week.

[Sinclue]

Ray,

Some sources for Marine sealants(online): West Marine, Boat U.S., and SailNet. Others on this board have used liquid nails with success.

Sounds like a good permanent installation. I think I would mount the heavier panel in the middle. It seems to me that maybe the weight on one side or another might result in some torquing of the shell when you open or close (possible scrapping or hanging up).

Remember that wherever you mount them you'll want that spot to be located to likely receive the most sunlight. If you are in hot places that makes for more heat on that part of your rig (and inside too).

jim

[RockyMtnRay]

Thanks muchly for the suggestions...I just checked the 3 on line marine stores and 'twould appear the strongest adhesive they're offering is an epoxy. Suspect I could find something at least that good locally so tomorrow will be a day to prowl the hardware stores.

As for mounting the panels toward the side (vs the center of the roof), I don't think that will be a problem as the weight of the awning (which is about twice as heavy as these solar panels) is totally on the curb side of the front shell yet there is no torqueing or twisting of the shell as it is raised and lowered. I'll certainly keep your caution in mind before I permanently glue the mounting pads to the roof & am planning to temporarily mount them with duct tape and do a bit of experimentation to make sure the shell raises and lowers properly. I'm sure I'll have to adjust the torsion bars a bit anyway and if there is some twisting, will see if preloading the curb side a bit more takes care of it. Also, I'm quite fortunate in that The Car Show (my TM dealer) is only a 20-30 minute cross-town drive away and has been more than happy to capably answer questions over the phone.

As for heat & sunlight issues, my situation is quite a bit different than most folk's. About 99% of my camping is done at elevations above 8000 feet and probably 60% of it is at elevations above 10,000 feet...so the temperature even in direct sunlight is seldomly much over 75 degrees. And since the forests at those elevations are almost entirely skinny/scrawny pine trees (largely lodgepole pine)...or equally scrawny aspen trees, there's effectively zero shade over the trailer in any campground that I've been in between roughly 9 am and 3 pm...even in the campsites that are labeled as "shady". Soooo I"m really not concerned about positioning panels (or even the trailer) with regard to shade from trees. However, because the mornings in Colorado's mountains are almost 100% likely to be clear and the afternoons are almost as likely to be cloudy (because of the almost daily thunderstorm formations), I sorta pay attention to whether or not the campground as a whole will get morning sunshine.

[RockyMtnRay]

Bill...

I did this sorta scientifically by using the handy-dandy worksheet that RV Solar has on their website (http://www.rvsolarelectric.com/custom.htm). I camp solo about half the time, the rest with one companion...but in my case that's not the major determinants of electrical usage. My electric usage comes mostly in the following categories:

--As noted before, I mostly camp at high altitude where nighttime temperatures are often in the 30s even in mid-summer. And I'm usually up well before dawn and often run the furnace for an hour or more in the mornings, sometimes for half an hour in the evenings. Figured I'd need about 15 amp-hours just for the furnace.

--Assumed I'd probably use other electrical devices (in particular the water pump) to the tune of around 4 amp-hours each day.

--I like a LOT of light...especially when I'm trying to wake up and get going in the morning. If I have my druthers (and the juice to do it), I'll simultaneously turn on most of the TM's overhead lights...and both of the "elegant" lights. Figured I'd need around 15 amp-hours for 2 to 3 hours of lighting.

--As a self-employed software developer with never-ending deadlines and client tech support requirements, the only way I can get away (even for 2-day camping trips) is to bring my laptop along. Every day I have email, a check on my servers (I run several database servers out of my home office), some development work, etc. Since I use my cellphone as a wireless modem at 14.4K (max), file & email uploads/downloads, web browsing, etc. take quite a bit of time. All in all, I figured about 2 to 3 hours or roughly 16 to 24 amp-hours to power the computer each day.

--Miscellaneous...like recharging my digital camera, cellphone, etc....about 4 amp-hours.

Add it all up and my daily power use (if I have all that I can get) is around 70 amp-hours. Add in a fudge-factor for battery and line-loss and it comes up closer to 80 amp-hours.

Based on the assumption that I'll have good sunlight for about 6-8 hours a day (some days more, some less because of afternoon clouds), I calculated that I'd need a panel array that could generate about 10 amps. Based on RV Solar's offerings and pricing, that turned out to be their Jumbo 120 watt Kit (7 amps of generation) plus a second 50 watt panel (3 amps of generation). Their Kyocera 50 watt secondary panel was only $20 more than a 40 watt panel; but the 80 watt was $100 more than the 50 watt. It seemed that for my needs the sweet spot in terms of watts/dollar system cost (including controller, wring, mounts, etc.) was at 170 watts total.

I'm guessing the total weight of roof mounted components will be somewhere around 50 lbs. This is partly from bits and pieces of info I've picked up elsewhere and partly from the shipping weight of my order (60 lbs) The RV solar price list shows 12 lbs each for their kits but I think that's probably way too low.

I personally am kinda doubtful that a 50 watt panel would be enough to recharge your battery every day unless you're extremely frugal with power usage...and have cloud-free skies and a shade-free location for your panel nearly every day. A 50 watt panel is only going to generate around 3 amps in full sunlight under normal temperature conditions.

Ray,

I've had quite a bit of experience with adhesives during the manufacture of my woodworking tools. You mentioned the use of epoxy glue to mount your solar panels to your TM's roof. I can see a couple of problems with using epoxy for this application. The first is that epoxy resins begin to soften at around 140 deg. Fahrenheit temperature. The second is that epoxy resins slowly deteriorate with exposure to sunlight. They become chalky and powdery. This latter result can be prevented or retarded by painting the glue lines with some kind of a durable paint, perhaps one with a UV light inhibitor. However, using this kind of adhesive in a location for which you will try to maximize sunlight exposure, and therefore heat from the sunlight, may not be the wisest thing to do.

Whoh Ray, be very careful of the placement, you WILL have to adjust your torsion springs by adding them, if too heavy, might have to buy all new ones as I was told by Jimmy Davis at the TM plant when I was considering adding roof air. (That's about 100.00 a pop, x4, if it's that much heavier a setup). Chosing to find a side air unit which mine was made for, I simply removed my awning, (because I was thinking about getting a new one, and didn't want to drill any holes in all the new aluminum I added in the top before that decision was finalized), and see a SIGNIFICANT difference in how my TM closes, opening's fine tho I'm sure it scrapes a bit, the seals for the most part protect it, but when I go to close it, (by another member of this board's description, which fits it best), it calliwhumps down, scraping all over the awning side because it's adjusted PRECISELY to the weight of the awning that is supposed to be there! (no, the springs aren't "that" forgiving, they have to be adjusted for like every 10lbs or maybe more, not sure, but to be on the safe side, lets say 10lbs). Just be very careful Ray about the weight distribution as you'll wind up scraping up your windows and such if you're not aware of that. I would suggest before you glue them down, do your best to distribute the weight equally, and try opening and closing the top and see how it goes, never mind if it gets hard to open for the extra weight, that can be adjusted later, just make sure it opens up SMOOTHLY.....without rubbing or "callywhumping".

Next, may I suggest "Gorrilla Glue" as an adhesive? You can seal them with silicon still, or whatever ya want, but that stuff is rock solid, and won't give.....no matter what, and if ANYONE in this room knows a way of removing it in any way, PLEASE let me know, I have a few dribbles I can't even scrape off with a knife it's that strong! (Body shops use it in fact to secure molding and such it's so strong!) Might have to get my Dremel tool after it I guess, and paint underneath when I hit aluminum? LOL (Nah, I'd much rather simply find a solvent that would get rid of it rather than do that). It's a bit expensive, but worth it, and will bond aluminum to aluminum, or whatever with NO WORRIES ABOUT ANYTHING coming lose! lol Lets put it this way, dunno what TM is using to glue the aluminum in there now, but after removing the wood from mine to replace out, I peeled back the stretchy glue from the aluminum like a sunburn peeling. Gorrilla Glue, um, I think the area would have to be cut out, then the aluminum skin probably could not be removed in one piece with a chisle and a hammer even! Dunno much about epoxy's, but this stuff bonds to aluminum WELL! (And it looks so innocent simply sitting in the bottle like a typical Elmer's glue only brown). LOL I can CERTAINLY speak from experience on that stuff!

Anyway Ray, please keep the things I said in mind while doing your project, and you should be ok....(Especially about the weight thing)......Anyway, hope I'm of help!

[glow=red,2,300]Happytrails........[/glow]

[RockyMtnRay]

Whoh Ray, be very careful of the placement, you WILL have to adjust your torsion springs by adding them, if too heavy, might have to buy all new ones as I was told by Jimmy Davis at the TM plant when I was considering adding roof air.

Already ahead of you there, HT. When my dealer installed an awning this spring, they found the existing torsion bars couldn't be adjusted enough to handle the extra weight. So they went ahead and put in the heavy-duty bars and I now have a heckuva lot of torsion adjustment available.

I would suggest before you glue them down, do your best to distribute the weight equally, and try opening and closing the top and see how it goes, never mind if it gets hard to open for the extra weight, that can be adjusted later, just make sure it opens up SMOOTHLY.....without rubbing or "gallywhumping".

Well, as noted above, I'm certainly not going to permanently attach the panels until I'm satisfied with both the panel position and torsion adjustments (will use duct tape to temporarily mount them). There are pros and cons to both center mounting the panels and side mounting them. Center mounting will balance the weight between the two sides...but since the awning is one side only (and weighs a lot more), that is not necessarily required. Side mounting will allow me to use the top of wall aluminum structural tube with screws (vs adhesive)...and it will help the overall side to side weight balance of my TM (my street side weighs nearly 200 lbs more than my curb side because all the water tanks are on the street side). I will discuss this issue with Jimmy Davis before finally settling on a location. At the moment though, I'm leaning toward mounting them along the curb side right next to the awning and adjusting the tornsion bars as needed to balance the weight.

Next, may I suggest "Gorrilla Glue" as an adhesive? You can seal them with silicon still, or whatever ya want, but that stuff is rock solid, and won't give.....no matter what, and if ANYONE in this room knows a way of removing it in any way, PLEASE let me know,

I spent nearly all of this past weekend researching structural adhesives and found that Loctite Corp's website had a treasure trove of information...see http://www.loctite.com/literature/. A lot of it is pretty technical but since I have a Masters Degree in Chemistry I found it as fascinating as a great novel....but the phrase "Your Mileage May Vary" might apply for other people.

To make a very long story short, there are basically 4 or 5 classes of applicable adhesives...epoxies & urethanes, 2 part-no mix acrylates, silicones, and cyanoacrylates. Only the epoxies, urethanes, and 2-part acrylates have the sheer strength, weather resistance, peel resistance, etc. to be suitable for attaching solar panels to the roof of the TM.

Gorilla Glue is a urethane class adhesive. As you note, urethane adhesives are (or can be) extremely strong. However, the "curing" process of urethane adhesives is dependent on moisture diffusing through the polymer. For you in pretty darn soggy Virginia this is not going to be a problem as you have lots and lots of atmospheric moisture nearly all the time. For me in typically arid Colorado (relative humidities often way below 10%), this could be a very big problem and there's a distinct possibility that Gorilla Glue would not form a strong bond here. I'm not sure if they even sell the stuff hereabouts.

As Larry notes (and was confirmed by the Loctite literature), epoxies are not very tolerant of temperatures over 140 F...and on a hot, sunny day the roof of the TM is quite likely to exceed that.

Soooo, I'm currently focused on the 2-part acrylates like Loctite Depend. This class of adhesive is extremely strong (2000 to 3000 lb/sq inch sheer strength) and is very heat tolerant (at least 260 degrees). It's also tolerant of uneven bond gaps and even some contaminants on the surfaces. And unlike epoxies, there's no need for precise ratios...apply the resin to one of the surfaces to be bonded and an activator (or catalyst) to the other, stick them together, and in about 2 minutes the bond is "fixed". Badda-bing, Badda-boom. The problem is that these are very, very pricey adhesives (around $25 for an eensy, weensy, teensy, tiny 25 ml syringe of the resin...though that's supposed to be enough for 200 sq. inches) ...and not sold by just any old hardware store. I'm hoping that one of the Loctite distributors here in Colorado Springs (we have about 6) will have the stuff but, if not, I can get it from at least 2 on-line adhesive merchants.

Based on case studies I found on the internet, I'm sure this stuff is strong enough...one company is using it to attach micro-vortex generators to the wings of aircraft (instead of rivets). And the folks who run the particle accelerators at the national nuclear labs use it to attach the accelerator/focusing magnets to the tubing (an incredibly demanding application).

[RockyMtnRay]

Allrighty, time to post an update...the panels and parts arrived yesterday and today I spoke with Jimmy Davis at TM about mounting and with a local adhesives expert about adhesives.

First the panels...the 120watt panel is 26"X58" which is pretty darn big when you actually have it in your hands! The 50 watt is a much more manageable 26"X26". Although kinda unwieldy, the weights are quite reasonable...the big one is about 25 lb, the smaller around 11 lbs. They come with just a connection box on the back (no wires attached) so I haven't yet had a chance to hook them up to the charge controller and a battery and put them in the sun for some testing (will do that on Sunday after I get a couple of hot deadlines met). I can say that the folks at RV Solar did a really good job of packaging them for shipment....lots of sturdy spacers and tape and double boxing.

Jimmy Davis was right up front about Solar on TMs...the factory doesn't do this so he doesn't have much knowledge on the subject or recommendations on best practices. He did, however, say that it really doesn't matter where the panels are mounted on the roof (center or edge) because the total weight is relatively low (only about 36 lbs) and that any side-to-side weight imbalance can easily be handled by tweaking the torson adjustments (especially since I have the heavy duty torsion bars but don't have the roof air).

He also said that there are actually two square aluminum tubes at the top corners of the roof in the newer TMs...one in the edge of the roof section and one in the top of the wall section...and these are stacked vertically (roof over wall). Thus, if I wanted to mount the panels on the edge of the roof, I'll be able to sink longer screws down through two structural elements.

I asked if there might be a problem with glued-on panel mounts causing the TM's skin to delaminate from the foam core and he said he'd never heard of that happening to anyone.

Finally, he said the soft rubber strip on the top edges is basically cosmetic only...it hides the screws that actually attach the roof to the wall...and can be cut away as needed to mount the solar panel z-brackets. Oh...and they use a regular clear silcone caulk on their screws to keep the water out.

Finally, had a great discussion with a sales rep at a local branch of the Fastenal Corp (http://www.fastenal.com) (these guys are the experts in fastening things together!) and after I explained my requirements he said he'd do some research and get back to me. Welll...after he talked to a Loctite tech rep, it turns out they recommend the same adhesive I thought would be best: Loctite Depend (http://www.loctite.com/datasheets/tds/Product_330.pdf). They don't have it in stock but will have it by Monday. About $32 for a kit with 25 ml of adhesive (and tiny spray can of activator)...a few bucks more than the cheapest on-line price but I also don't have to pay shipping.

Soooo...the plan now is to mount the panels along the curb (door) side top edge right next to the awning. I'll use sheet metal screws to attach the Z-mounts to the underlying tubing on that side of the panels. And on the other side of the panels I'll rivet 5"X5" aluminum plates (1/8 inch or thicker) to the Z-mounts and bond the plates to the top of the TM with the Depend adhesive.

Before final mounting there'll be some testing and torsion tweaking with the panels affixed with duct tape.

Yes Ray, he was correct about the tubing in the wall and roof sections. Did he say anything about any wood being used in there? In mine, I had to replace the 1.5" wood that had been rotted, with 1" of aluminum tubing, and .5" thick wood strips simply added in there as a filler to fill the gap that would have existed had I only used the aluminum. I imagine they're simply just using the aluminum tubing now tho which is a 1x1 square tube. If you would like to see what I'm talking about, you can see a good example of what exactly's in there JD was talking about on my web page.
http://members.aol.com/br768
Just remember, you probably don't have the wood in there, so you'll have 2" of aluminum tubing to screw down into. Though you can still use 2.5" screws as they will simply get a better bite on the last layer of aluminum in the bottom of the bottom tube, and go harmlessly down into the styrofoam in your wall section. If you use stainless steel screws, be sure to drill your pilot holes just the right size as stainless is very brittle as you well know. Hope this helps!

[glow=red,2,300]Happytrails........[/glow]

[RockyMtnRay]

HT...

As a matter of fact Jimmie did mention that they quit using wood framing "a few years ago" and that my 2002 would definitely be aluminum tubing only.

Thanks muchly re the caution on the brittleness of stainless steel screws...I actually wasn't aware they were more brittle than regular steel! But, to be honest about, I hadn't given the type of screw a whole lot of thought yet (the panels came with what appear to be inch and a quarter galvanized screws). When I go to get the aluminum sheet to make the mounting plates out of, I'll see what my hardware store can scare up vis-a-vis longer screws.