PV panel mounting?

kaipo_boy

Solar newbie here. I've just received three new Trina 285w panels and boy are they pretty. This should probably be posted in a different section but they will be connected to my small battery system, so I figured I'd stick with this section of the forum. You guys have probably covered this ground many times, so feel free to point me to the correct place to go look it up...
The panels themselves feel like they weigh close to 40 lbs each and are maybe 77" x 39?" or thereabouts. They have a C shaped aluminum box section wrapping around the exterior dimensions. The corners are not mitered. The thickness (height) of the C channel is about 1.800" plus or minus a few thousands of an inch. So, along the longest axis, there are 3 holes drilled on each long leg; one in the middle, and one each at around the 1/4 mark... presumably for mounting.
My questions:
(1) I'm juggling several different designs in my head for making the mounting hardware. At first, I figured just use these existing mounting holes and bolt them to a cross beam made of steel or something.... has anyone noted any type of adverse galvanic reaction when combining these aluminum extrusion frames with a steel crossmember? I do have aluminum C channel extrusions of about the same size as the frames that I can use for a crossmember but those are not as big or as strong as I would like, given 3 abreast might provide a pretty good lift in a gust.
(2) A new thought has occurred to me and that is, why bother with the mounting holes? it will mean marking out your crossmember very tedious because you have to get the hole spacing just right to fit the hardware for mounting. It would be an easy thing to just cut a small section of, say, L shaped angle iron, and on the long leg of the L, weld a short tube that will fit a long mounting bolt... then you can just use the L as a clamp and clamp your frames down to a crossmember and not worry about any hole spacing. YOu don't have to gorilla the clamps down super tight, as we have no snow or super high winds here in hawaii.... These will be mounted on the ground in my back yard, no roof rack to worry about. Do these frames tend to react badly to frame clamping? Have they crushed the frames or led to the PV chips cracking inside? Have people used a small section of compliant rubber or something between the clamp and frame to act as a bushing?

Lastly, I'm at around 21 degrees north latitude. Does that mean I should angle the panels around 21 degrees from the horizontal?

aloha,
walt

Photowhit

Mounting within 15 degrees of you latitude, for max exposure, you might go for a slightly higher angle to help with the natural cleaning of rain showers.

I used aluminum angle drilled out to a pattern so the spacing was consistent then mounted wood with the bottom pre drilled to start the panels in parallel.

My old panels have been up for @10 years and still working fine, though one of the supports that were not attached directly to the panels warped bad enough to warrant replacing.Attachment not found.

The 'buffer' between the aluminum and the pressure treated wood is a plastic. I actually connected a couple panels, that I thought would be temporary, without the plastic and I saw minimal oxidation of the aluminum, so I don't bother anymore. The panels are raised above the wood and rest solely on the aluminum angle.

I only used stainless steel fasteners, SS can be tricky and it likes to bind to it's self, use a bit of grease/wax on the bolts! Also might be worth being sure the nuts and bolts are different alloys!

Vic

Hi kaipo..,

Here is the Data Sheet on a Trina 285 + PV module, assume that this is the PV family that matches your Trina 285:
http://www.trinasolar.com/HtmlData/d...eb13_US_EN.pdf

This PV weighs 60.8 Lbs. There should be an Installation Guide for these PVs. This should specify the required mounting means -- Top Down clamps, bolting through the rear flange (if it has one) etc. This manual should also specify the number of mounting rails per PV, and the recommended orientation of the rails, and the PV, plus the recommended number of mounting rails for differing wind/snow loads (perhaps).

Here is the Installation Guide:
http://www.civicsolar.com/sites/default/files/documents/trinasolarmoduleinstallationmanualul-1703-43136.pdf

FWIW, Good Luck, Vic

kaipo_boy

Wow, thanks guys. I bought them cash and they didn't have a manual with them although they are still new/unused.
Vic, good to know that they were 60#! I thought I was getting wimpy as they were harder to move around than I thought. Not that heavy, but pretty bulky and lots of opportunity for the wind to catch one...

Photowit, I see that your panels are bound together but that the L sections you used are also aluminum... I do have aluminum lying around but nothing as thick as you have there. I do have steel angle iron lying around; do you think that would do? I'm worried about corrosion as hawaii has red dirt and salt in the air... nice going on 'lifting' them above the wood so they don't have many places for water to gather. I live in a desert, technically, as the rainfall here is very very minimal. I had to give up having a nice yard as the water expense to maintain it was horrendous.

Vic

And, kaipo..,

Just my opinion, but believe that these long, heavier PVs should really be handled by two persons. If you handle them by yourself, please be very careful, as they may tend fo flex a bit, and this could possibly damage the glass seals, possibly.

The 48-ish lb PVs like the SW 280s, etc, are only about 66 inches long, and seem very easy for one person to handle and mount, but seems to me that 61 lbs and 77 inches long (sorry, am in the USA), seems like it is pushing it for one person.

Opinion, FWIW, Have Fun! Vic

waynefromnscanada

Photowhit wrote: »

The 'buffer' between the aluminum and the pressure treated wood is a plastic. I actually connected a couple panels, that I thought would be temporary, without the plastic and I saw minimal oxidation of the aluminum, so I don't bother anymore. The panels are raised above the wood and rest solely on the aluminum angle.
I only used stainless steel fasteners, SS can be tricky and it likes to bind to it's self, use a bit of grease/wax on the bolts! Also might be worth being sure the nuts and bolts are different alloys!

One thing I learned a couple of years ago is that there are now several different processes and chemicals used to pressure treat wood. Some are far more corrosive to aluminum than others. Whatever the wood I used 8 years ago was very corrosive and it was then I learned to use a plastic barrier between the wood and metal. Of course I live in a rather damp climate, so that too may have contributed to the problem. Thankfully I discovered the problem one year after installation, before the damage became more serious. My experience would lead me to suggest using a barrier. You can always remove it later if you want to, but it would be a shame to have your panels etc damaged. In my case the panels were bolted directly to the treated wood, so yes, it was the panel frames that were corroding.

Mountain Don

Regarding the current PT woods and metal... Aluminum is about the worst there is to have in direct contact with PT wood. The fasteners that contact the PT wood are also "special". S/S is very good. Hot dipped galvanized is good, but the common everyday variety of electroplated zinc is not. There are other special coatings that are approved for use in PT wood. The damper the climate, the damper the wood, the worse the problems. There are self adhesive materials used as door and window flashing that make good separations between metal and PT wood. (Google Grace Vycor)

Photowhit

kaipo_boy wrote: »

Photowit, I see that your panels are bound together but that the L sections you used are also aluminum... I do have aluminum lying around but nothing as thick as you have there. I do have steel angle iron lying around; do you think that would do? I'm worried about corrosion as hawaii has red dirt and salt in the air... nice going on 'lifting' them above the wood so they don't have many places for water to gather. I live in a desert, technically, as the rainfall here is very very minimal. I had to give up having a nice yard as the water expense to maintain it was horrendous.

I purchased my aluminum on eBay, not sure if priority mail is 48 or 50 states now. I think that use to be the cheap shipping method to Hawaii.

I think Aluminum has the advantage, if you can call it that, of skinning/surface oxidizing very quickly, When I looked after 4 years(when the pictures were taken), I looked for pitting, and again when I took them down and moved them for their new owner after 5 1/2 years. I didn't see much more than surface and that wasn't powdery. Yes salt air is wicked stuff! I would be very hesitant to use standard steel angle, I suspect it would rust very quickly, with minimal rain you might try some of the coated steel, I'm not sure about having SS in contact with steel, I think Bill said something about worrying about electrolysis as well...

kaipo_boy

Excellent comments, all. I've owned many boats in my life and in my mind electrolysis is a process that can only happen while the bits are immersed in solution, so while the boat is in the water... but the corrosion I would see on my boats needed constant attention, even while the boats were not in the water very often so its pretty obvious it also happens without immersion. My favorite tactic would be to just clamp cheap-to-replace zinc sacrificial anodes everywhere. Thought about it for PV panels, but haven't seen anyone else do it... probably not worth it? Has anyone else bothered?

I'm still playing with the idea of using some steel angle iron (thanks for the comments, Photowit) vs trying to pick up some aluminum ones... I thought, what if I just used really really heavy paint on the steel angle iron to retard corrosion? But I think I'll have to go look for some aluminum. Sigh, another delay... but I have to order some MC4 connectors anyway, arghh.

softdown

Pound for pound, steel is generally similar to aluminum for strength purposes. Prime it before you paint it. Both materials can work well and are not prone to the splitting and splinters that wood is notorious for. Plus you can employ ~#12 self drilling roofing screws with rubber washers and avoid drilling a lot of holes.

I look at this way. Say you are driving a 60,000 pound rig. Would you rather cross a wood, aluminum, or steel bridge? Having said that, aluminum is the most common fastening material in the solar industry. Looks spiffy and is easy to work with less corrosion.

You might find an angle iron welder on craigslist. Aluminum welders are a lot more rare.

If heating is the big issue, use an angle greater than your latitude. If cooling is the issue, use an angle less than your latitude. Maximum gains during the summer are found at latitude minus 15 degrees. Maximum gains during the winter are found at latitude plus 15 degrees. I am in a cold climate so it was a no brainer to settle on 45 degrees while being at a latitude of 37. Lose a little during the summer. Gain a little during the winter when the days are short and often cloudy. No brainer.