Solar Tracker Design

[400bird]

I want to start by saying that I realize I will never recoup the money spent on this tracker. I don't need any reminders.
Electronics and solar are my hobby. The tracker was the 11 year old's idea and he wants to help!

Anyways on to the meat and potatoes!

We're looking at a 2 axis tracker on top of a pole with 2- 480 watt panes. The array will be roughly 6' x 6'
The first conundrum is how tall should the mount/pole be?
We live in a suburb, so this is going in the back yard, near the house.
House faces south, backyard on the north.
That means the sun rises over the house, and figuring out the height of the pole leaves more variables outside of my math skills than I like.

There's the measurements I am stuck with:
Roof ridge 14' tall
Tracker mount will be 26 north of the peak.
Latitude 37.7595 puts the lowest sun at an elevation of 28.8° on Dec 21st.

Here's the backyard layout, up is north. The dot is the approximate tracker location. The roof ridge runs east/west at the bottom of the image.



Once I have the pole height figured out, this is the tracking mechanism we plan to use:


Control program is in process, will be run on an Arduino (or Raspberry Pi, but that seems like overkill this far)

 

[Zwy]

Go here and input your location, zoom in, enter the height of the house and see where the shadow is from the house. https://www.suncalc.org/#/44.979,-93.2649,11/2022.12.14/18:01/8/1

Need any assistance on how to work it let me know. It took me some time to figure it out. Move the map around, the sun dial will recenter, the center red dot is where the high point that causes the shadow will be. The very top of the page you see the time scale, you move the yellow dot to scroll thru the day. Be sure to check the winter solstice.

 

[Doggydogworld]

I think you mean 28.8 degrees elevation. That only applies at high noon, but using that for starters we get:

14.0' - (26.0' * tan 28.8 deg) = ~0'

So you could put the panels on the ground and your roof ridge would not shade them at high noon on December 21. It's probably not the ridge that's your issue at high noon, though, it's the gutter. If your roof pitch is 4:12 (18.4 deg) then any time the sun is higher than 18.4 degrees the backside of your roof will be in the sun and the ridge will cast no shadow.

If your pole is 10' from the gutter (just a guess) the bottom of your panels could be 10' * tan 28.8 = 5.5' below your gutter on high noon Dec 21.

Enough about high noon. Your problem will be early morning and late afternoon in winter. The ridge line will come into play then. At sunrise the sun will be on the horizon and the only way to illuminate your panels is to raise them higher than the ridge. You need to decide how early and how late you want to be illuminated on Dec 21. That math gets tricky and you're better off playing with something like SunCalc mentioned above. Your neighbor's roof (to the west) might also come into play in the evening.

 

[realpinochet]

I want to start by saying that I realize I will never recoup the money spent on this tracker. I don't need any reminders.
Electronics and solar are my hobby. The tracker was the 11 year old's idea and he wants to help!

Anyways on to the meat and potatoes!

We're looking at a 2 axis tracker on top of a pole with 2- 480 watt panes. The array will be roughly 6' x 6'
The first conundrum is how tall should the mount/pole be?
We live in a suburb, so this is going in the back yard, near the house.
House faces south, backyard on the north.
That means the sun rises over the house, and figuring out the height of the pole leaves more variables outside of my math skills than I like.

There's the measurements I am stuck with:
Roof ridge 14' tall
Tracker mount will be 26 north of the peak.
Latitude 37.7595 puts the lowest sun at an azimuth of 28.8° on Dec 21st.

Here's the backyard layout, up is north. The dot is the approximate tracker location. The roof ridge runs east/west at the bottom of the image.
View attachment 143756


Once I have the pole height figured out, this is the tracking mechanism we plan to use:
View attachment 143757

Control program is in process, will be run on an Arduino (or Raspberry Pi, but that seems like overkill this far)

Which actuator is that? What tilting design does it work with? The videos I've been watching show the typical plunger style actuators that push pull.

 

[realpinochet]

I was looking to build something similar to this.

 

[400bird]

Go here and input your location, zoom in, enter the height of the house and see where the shadow is from the house. https://www.suncalc.org/

Need any assistance on how to work it let me know. It took me some time to figure it out. Move the map around, the sun dial will recenter, the center red dot is where the high point that causes the shadow will be. The very top of the page you see the time scale, you move the yellow dot to scroll thru the day. Be sure to check the winter solstice.

Thank you for the link, I had no idea something like that existed! I'll play with it later this evening and let you know if I need assistance.

I think you mean 28.8 degrees elevation. That only applies at high noon, but using that for starters we get:

14.0' - (26.0' * tan 28.8 deg) = ~0'

So you could put the panels on the ground and your roof ridge would not shade them at high noon on December 21. It's probably not the ridge that's your issue at high noon, though, it's the gutter. If your roof pitch is 4:12 (18.4 deg) then any time the sun is higher than 18.4 degrees the backside of your roof will be in the sun and the ridge will cast no shadow.

If your pole is 10' from the gutter (just a guess)

Excellent guess, that's pretty much on the nose.

the bottom of your panels could be 10' * tan 28.8 = 5.5' below your gutter on high noon Dec 21.

Enough about high noon. Your problem will be early morning and late afternoon in winter.

Thank you, I didn't clarify my question well enough. As the sun rises, there's a point where it's going to com up over the west neighbor's roof (which is parallel with mine, same ridge line)

The ridge line will come into play then. At sunrise the sun will be on the horizon and the only way to illuminate your panels is to raise them higher than the ridge. You need to decide how early and how late you want to be illuminated on Dec 21. That math gets tricky and you're better off playing with something like SunCalc mentioned above. Your neighbor's roof (to the west) might also come into play in the evening.

Oh look, you mention the west neighbor's roof. I should have kept reading before starting my reply. Thanks for the input.

Which actuator is that? What tilting design does it work with? The videos I've been watching show the typical plunger style actuators that push pull.

It does both axises from one central assembly. One benefit is the array doesn't make the odd roll you get in the morning and evening with two linear actuators.
There are two slewing bearings at 90 degrees to each other. The black cylinders sticking off are the motors.
Search something like dual axis slew drive. It's not cheap, but it's what the kid picked. Compared to two quality linear actuators, pillow blocks, etc, the difference isn't as much as it initially appears.

 

[400bird]

Go here and input your location, zoom in, enter the height of the house and see where the shadow is from the house. https://www.suncalc.org/#/

I edited the link, you might want to do the same. It looks like it opens to your place as a preset location.

 

[Zwy]

I edited the link, you might want to do the same. It looks like it opens to your place as a preset location.

That isn't my location, I live in Iowa and definitely not in a city. I do believe it is a default location.

 

[400bird]

Well, using the calculator above, the actual results came out better than my seat of the pants feeling.

If I make the lowest edge of the panel 6' from the ground and a 9' tall mount (so I don't run into the panels when walking around the backyard) I will miss about an hour of early morning sun and late evening sun in Nov-Jan. The sun rises at about 7:30 and about 8:30 the panels are out of the shade. Shortly after sun rise, the top half of the panels are in the sun, so I'd have about 50% production as these panels are made from half cut cells.

But, I went out with a tape measure and reality set in. With that 9' mount, the top of the panels will be 12' from the ground. That is only 2' below the ridge of the roof. I'll end up with neighbors complaining for sure.

Looks like the mount will be significantly lower and at the rear of the property, near the north fence. A 4-5' tall mount will be easier to assemble, at at least I won't hit my forehead on the lower corners. It might cost me a shin or two...
Shading is no problem back there.

 

[Doggydogworld]

Sounds like a good plan. Keep us posted and show pics!

 

[400bird]

I've already ordered the slew drive, but the only options were from China. So, the waiting game has started, I've got like 45 days until delivery

 

[Warpspeed]

Another way to do this is to get a "sun chart" for your latitude off the internet.

Build yourself a spy tube that you can look through (poor man's theodolite) and mount that on horizontal and vertical pivots so you can turn it in both azimuth and elevation.
Fit a couple of cheap plastic protractors to it so you know what the angles are you are looking through your tube.

Now your sun chart will tell you exactly where the sun rises each month, and how it tracks through the sky.
You can look through your tube and see what objects get in the way at different times of day throughout the year.
It may be possible to choose a location within your property that has the fewest problems.

Don't know where you are, but here is a chart for 32 degrees north in the Northern Hemisphere.
One for the southern hemisphere look similar, but is upside down compared to this one.

https://hyperfinearchitecture.com/how-to-read-sun-path-diagrams/

This is a bit fancy, but illustrates the general idea.

 

[400bird]

Well, look what showed up today.
Paint can for scale, the thing must weigh 35-40 lbs. Now I want to weigh it.

Once I get a lot more progress, I'll likely start a new thread.

 

[Haze]

What tracker is that ? Do you have a link.

 

[400bird]

It is just the movement axis and motors, I'll end up building the PV frame and mounting post.

It is a dual axis slew drive. I couldn't find any source outside of China for the small size like I needed.

Here's a random Alibaba link, probably not the exact one I purchased.

Source Big size dual axis slew drive for solar tracker on m.alibaba.com

Big size dual axis slew drive for solar tracker, You can get more details about from mobile site on m.alibaba.com

m.alibaba.com

 

[400bird]

I've spent some time on designing the frame. These are bi-facial panels and I'm trying to keep the framing to a minimum. But I could use some input on both the design and material thickness.

The tracker/slew drive has flanges on each side that rotate to adjust the elevation/vertical.


Bolted to this flange, will be 2" OD (1/8" wall?) aluminum tubes protruding out each side.
The angle pieces the panels bolt to is 1"x3" for the two outers and 3"x3" for the center piece, all 3 are 1/8" thick aluminum.
I suppose I could use four 1"x3" pieces vs the current 3.

I am also considering sliding a tube inside (through the middle) and connecting the 2" pivot tubes to add some bracing/strength.

I guess the question is, do you think the design is strong enough?
Is 1/8" thick aluminum is a good choice?

The panels weigh 64 lbs/29kg each.
Wind loads here are low, it will see some protection by the fence, plus will park flat (below the fence line) when the wind gets too high.

That brings another question, any one have input on what wind speed should I park the tracker flat?




I slightly redesigned the end plates to show how they'd actually be built. I also added all the mounting holes for the panels.

 

[45North]

I want to start by saying that I realize I will never recoup the money spent on this tracker. I don't need any reminders.
Electronics and solar are my hobby. The tracker was the 11 year old's idea and he wants to help!

Anyways on to the meat and potatoes!

We're looking at a 2 axis tracker on top of a pole with 2- 480 watt panes. The array will be roughly 6' x 6'
The first conundrum is how tall should the mount/pole be?
We live in a suburb, so this is going in the back yard, near the house.
House faces south, backyard on the north.
That means the sun rises over the house, and figuring out the height of the pole leaves more variables outside of my math skills than I like.

There's the measurements I am stuck with:
Roof ridge 14' tall
Tracker mount will be 26 north of the peak.
Latitude 37.7595 puts the lowest sun at an elevation of 28.8° on Dec 21st.

Here's the backyard layout, up is north. The dot is the approximate tracker location. The roof ridge runs east/west at the bottom of the image.
View attachment 143756


Once I have the pole height figured out, this is the tracking mechanism we plan to use:
View attachment 143757

Control program is in process, will be run on an Arduino (or Raspberry Pi, but that seems like overkill this far)

I think I'd want to teach my 11-year-old the bigger lesson - you don't do projects that are uneconomic. And if you must, these are known as "hobbies".

 

[400bird]

These are known as "hobbies".

I thought that went without saying. Yes, this is a hobby. The kid is going to getting design/engineering hands on time.


Kid had a good idea on the center piece. Two mirror images with a flat plate to tie the two sides together. The flat plate is also less expensive than the tube.

 

[45North]

I thought that went without saying. Yes, this is a hobby. The kid is going to getting design/engineering hands on time.


Kid had a good idea on the center piece. Two mirror images with a flat plate to tie the two sides together. The flat plate is also less expensive than the tube.

View attachment 150705

Understood.
And you'd never make a bridge out of popsicle sticks either - which is what my 11 year old did.

 

[400bird]

Anyone have input on how to calculate the single footer?