How to mount solar panels in treetops?

[treecharger]

Hi tree folks,

I'm a solar electric system dealer in Washington State, where a lot of off-grid folks live deep in the woods. Solar PV panels do not work in the shade.

Most of my tree climbing is to put solar panels up in the tops of trees so they can be in the sunshine.

My question is, what would you recommend as the best way to attach the rack to the tree? The "side of pole" mount racks that we get have a steel band that wraps around the 'pole' (tree) to squeeze the rack to it. That creates a partial girdle of the tree, however, so I'm looking for a better alternative.

I can bolt the rack straight to the tree, but it is nice to have the sway bracing of the strap. I'm thinking of a combination of face bolting with some side braces bolted also to help with the twisting motion.

What kind of fasteners are okay for trees?
Galvanized lag bolts?
Stainless lag bolts?
Threaded rod thru bolted? galvy or stainless?
something else?

I usually remove enough limbs in the area of the panel(s) to reduce the sail area by about as much as I'm adding with the panels, and to prevent shading from lower limbs that will grow up in front of the panels eventually.

Solar panels in treetops is a great way to get clean quiet power to an off-grid location in the woods, but I want to be sure that I'm doing the best I can for the trees. Thanks in advance for your suggestions.

Eric
islandenergysystems.com
solarempowerment.ning.com

 

[ClimbinArbor]

wow have never heard of this before. what are the dimensions of the panel? how long have you been doing this? is there any long term (5-10year) studies on the negative effects to the tree? what are the standard inspection lengths on the installations?

as far as mounting goes the only systems i use are non-invasive, except for the rare static needed crotch. implementing into your design shouldnt prove to difficult. there are cambium protection sleeves that would fit your steel bands to preserve the bark.

However; any system you use should be reguraly adjusted so as not to hinder growth underneath the clamps. If a clamp is left unchecked the tree will grow around it. This is neither good for the tree or your panels(if the tree fails, you will get to observe the gliding capabilities of your panels). also you should be careful not to remove to many limbs from one area.



As far as invasive mounting goes i have a couple ideas that could help. an I-bolt top and bottum mount to the leader for your main mount, with 2 or 4 side mounted lines running to neighboring limbs secured in the same fashion to prevent swaying.

Another idea would be to incline the panel so that the bottom is mounted onto a lower limb and the top mounted to the leader. this would cause less stress for the tree. The side mounts would again prove useful.


Most hardware used is galvanized but i can't see stainless causing any problems either.

hope this helps a little. I am very interested to see how this thread goes. Plz give any long term details of any negative effects this system has caused mounting trees. this will better help us develop solutions and brainstorm ideas

 

[treecharger]

thanks for the reply. I have removed one rack from a tree that had been up for about 4 years. The tree had grown completely around the back band, I could not get it out (the band) without a lot of cutting so I left it up there. I would say that it had girdled about 1/3rd of the total circumference of the tree.

Yes it would be best to go up every few years to loosen the straps, trim any encroaching branches and check things out. Not everyone will do that, of course, but it could be a good service contract to set up with an arborist. If anyone wants to be a dealer/installer for my 'treecharger' product, let me know.

Of course if the top breaks out of the tree the whole thing could end up on the ground. No warranty for that!

I've done up to 200 Watts of PV panels in a tree - that is roughly 3' x 5' of glass area.

Hopefully this image will work, this is a 75 Watt panel, but you can't see the band very well in the picture :.

BTW, I've also put wind generators in tree tops:

So galvanized fasteners are okay for tree health?

best,
Eric

islandenergysystems.com
solarempowerment.ning.com

 

[ClimbinArbor]

okay i see your setup now. like i said this is a new one on me, give me a day and check back, maybe i can come up with some of my patented genius on this.

yes most hardware used in tree applications are galvanized.

as far as the wind generators go, i would recommend(for tree health) using a longer rod. topping a tree is bad........ You should really read up on proper tree pruning, i see some nasty cuts in those pics.

Also, i don't know how busy you are, but i would consider trying to contract annual in tree inspections on all installations. put it on the initial install contract. its more work for you, better for your system, and better for the tree.

are your current mounting straps adjustable? if not consider making them so.

 

[ClimbinArbor]

oh and btw. as i said most tree hardware i use is non-invasive. hopefully someone else will chime in with me on the galvanized vs stainless subject.

Hint. Hint.....

 

[rbtree]

treecharger, contact Scott at www.treesolutions.net. Best consultant around. He's an infrequent visitor here as well..... http://www.arboristsite.com/member.php?u=8297

 

[M.D. Vaden]

Seen the trees in my signature link?

The redwoods?

A link on that page goes to Dr. Sillett's webpage at Humboldt State University. And he has a photo album there. He also has some huge photos on the Gigapan website.

He mounts solar panels in redwoods that are of the highest priority for preservation. See if his photos provide useful clues.

The redwoods he puts solar panels in to run the cased computer and scientific instruments, have a different canopy structure due to age, than what you may work in. So his method may or may not work for your needs. But I doubt he bolts at all. Probably all straps.

I'm not so certain that you should focus on some aspects of tree pruning, although it never hurts to know more.

But your opening post seems to connote that many of these trees "off the grid" would be in areas where we might expect some of the trees to be logged anyway. Or similar in nature.

And I'm guessing that being able to live and have power would be a priority.

There are properties like that minutes south of us near Rogue River National Forest. If I were to buy one, getting light to the panel would be the priority.

My request would be for stainless steel. More expensive, but not too much.

Seems that an elastic nature of mount would be miserable, and at least for me, I'd say, just find a solid tree and bolt the panel to it. Then have you come out every 2 to 5 years for maintenance, remounting, etc..

The best mount for a tree, might be one that contacts bark in the smallest area. Like if a mount could clamp with a stabbing prong from two sides, where skinny ends poke in and clamp with pressure, that could be better than a big plate.

Wrapping or encircling the trunk is not too good. At least for my needs, I'd rather have a plate bolted on one side.

 

[BIG JAKE]

I would probably use standoffs and lag into the side of trunk rather than a band, as it doesn't take long for a tree to grow around it. If the lag is long enough, say 4 to 6 inches of freespace, this would allow the tree to continue to grow circumference wise for a long time. The lag will get buried over time but so what. You could use a small safety cable attached to the frame of your panel to save it from falling in the event high winds snapped of the trunk or limb at that point. Galvanized bolts of 3/8 to 1/2" dia should last as long as a panel will, based on hardware I've pulled out of trunks.
You can use additional panels at different angles to capture sun at different times of day. The combined energy input to your battery bank at days end is what matters, not necessarily full power to each panel. As long as you keep the batt's at full charge, then goal is met.
Other idea- lag a mast holding a pair of panels above tree top, like in the turbine pic-square tubing with holes so you can pull a pin and adjust upward occasionally.
For me, I'd keep them on my roof and remove a few trees, or mount a bank of panels on a tall pole. I don't like prospects of continually having to screw with something every few years.
Just ideas-nice thread/nice work!

 

[ClimbinArbor]

I would probably use standoffs and lag into the side of trunk rather than a band, as it doesn't take long for a tree to grow around it. If the lag is long enough, say 4 to 6 inches of freespace, this would allow the tree to continue to grow circumference wise for a long time. The lag will get buried over time but so what. You could use a small safety cable attached to the frame of your panel to save it from falling in the event high winds snapped of the trunk or limb at that point. Galvanized bolts of 3/8 to 1/2" dia should last as long as a panel will, based on hardware I've pulled out of trunks.
You can use additional panels at different angles to capture sun at different times of day. The combined energy input to your battery bank at days end is what matters, not necessarily full power to each panel. As long as you keep the batt's at full charge, then goal is met.
Other idea- lag a mast holding a pair of panels above tree top, like in the turbine pic-square tubing with holes so you can pull a pin and adjust upward occasionally.
For me, I'd keep them on my roof and remove a few trees, or mount a bank of panels on a tall pole. I don't like prospects of continually having to screw with something every few years.
Just ideas-nice thread/nice work!

and people say tree climbers are crazy!

+1 for good ideas.

 

[Kneejerk Bombas]

I like the idea of stand offs of some sort to prevent girdling of the tree.
I can not think of any tree health issue with any metal hardware. A lot of commercial tree hardware is galvanized and it holds up well in living trees, it's also readily available in all different sizes and shapes, and it's cheap.
Stainless would work, but it's spendy and really not very strong.

There is a lot of new hardware that is made from grade 8 steel. It's tough and corrosion resistant. Builders are using it to replace the old galvanized stuff, because for the same strength you can use a much thinner piece of hardware. For example to get the same strength as a 1/2" galvanized lag bolt, you can use a much smaller screw that self taps in with a drill, is just as strong, and is cheaper than the old galvanized hardware.
Smaller holes in the tree, and sufficient stand off for the mounting plate, to allow the tree to grow in diameter, are most important.

Here's the site for LedgerLok: http://www.fastenmaster.com/product.aspx?currentPage=1&catID=8&prodID=9
There is another good one called HeadLok, you'll have to look it up.

 

[(WLL)]

man that looks like ****

 

[Kneejerk Bombas]

man that looks like ****

It looks beautiful to me. Much better option than clearing a big hole in the stand! Plus, alternate energy is so cool.
It's somewhat natural too. It's not uncommon for a conifer to have a top blown off in a storm. I bet in some cases you can't even see the devices without a view from a certain angle.

 

[treecharger]

Here is another picture of a rack in a tree. You can see how the back strap ties into the rack to provide sway bracing. There was a big SS hose clamp on the wiring at the top which I removed, but you can see the imprint in the bark.
The black straps are big plastic zip ties that are left loose to keep the wiring from shaking around.

I know that my system needs to be improved. Thats why I'm asking you guys.

Next I'll post a picture of my new design.

 

[treecharger]

Here is my latest idea for a new tree mount rack. Gotta love Sketchup!

The mounting feet would be U channel steel with 2 holes for screws. Each foot has a horizontal plate welded to it to attach the lateral sway brace straps. The sway brace strapping could be lighter gauge steel so that it could bend out to fit bigger trees or in for smaller trunks. The straps would have holes for multiple screws. The straps would not go all the way around the trunk.

Not shown are the horizontal rails to attach the PV module(s).

What do you think?

 

[treecharger]

Okay one more picture for you all for tonight.

This is what might be at the bottom of the tree, what I call the "Treecharger". It is a AC/DC integrated off-grid power center with plug inputs for the PV modules, PV charge controller, sealed battery and inverter/charger. The accessory shelf is so you can have your batteries and gadgets charging safely inside the box until you need them. You can also hard wire AC or DC power circuits and meters and controllers.
Read more on my website: http://islandenergysystems.com

 

[M.D. Vaden]

You probably have a counterpart in Ontario Canada.

My mother is from an area by Lake of the Woods up there, and there are thousands of islands.

 

[Kneejerk Bombas]

Here is my latest idea for a new tree mount rack. Gotta love Sketchup!

The mounting feet would be U channel steel with 2 holes for screws. Each foot has a horizontal plate welded to it to attach the lateral sway brace straps. The sway brace strapping could be lighter gauge steel so that it could bend out to fit bigger trees or in for smaller trunks. The straps would have holes for multiple screws. The straps would not go all the way around the trunk.

Not shown are the horizontal rails to attach the PV module(s).

What do you think?

Not a great drawing below, but I hope it gets the point to you.
Rather than having the "U" bracket tight on the sides of the tree, make it wider and use stand offs to allow you to tighten it.

The same with the center bracket, just use some kind of stand off. I was thinking a short piece of metal conduit, a stack of washers, or whatever.
The smaller the diameter, the better for the tree. It would keep the tree from growing around the bracket, harming the tree and making it hard to move if the tree grows around it.

 

[TXtreemonkey]

Just a tought

When you lag bolt the bracket, Think of putting in a spacer(of 2'' to 4'').
We have done this when we install Light in yellow pines, this way when the tree grow around the lag there is still room have the bracket.

 

[treecharger]

Thanks guys, the spacer idea makes a lot of sense.

It seems like it might be a bit to juggle all that hardware (lag bolts, short lengths of pipe, rack) while up the tree however. I'd like to keep it to a minimum number of parts to deal with in the tree.

I'm going to work on my mounting bracket design to try to build in the spacers into the welded mounting foot somehow. I'll post some renderings when I have them.

best energy,
Eric

 

[treecharger]

new tree mounting foot

Here's an idea for a mounting foot to lag bolt into the tree. The 'legs' are 3" lengths of 1/2" steel pipe welded to a 6" square plate. It will be hot dip galvanized. The lag bolts would be 5/16" diameter and between 8" and 12" long.

This would allow the tree to grow around the 'legs' for 3" until it came to the plate. Obviously there is no removing this sucker.

With solid bolting this thing will be very stout. I don't think it would need any lateral sway braces at all for a reasonable sized rack.

What do you think?