diy solar

diy solar

How to correctly measure for solar angles for DiY design and build

JohnLM

New Member
Joined
Dec 1, 2019
Messages
51
I was wondering, how do you calculate the angles for rigging up a solar panel for the maximum sun coverage?

I have seen numbers like 20 to 45 degrees but I don't know if those are correct angle numbers. What I'd like to do is rig some wood or metal poles and draw the angle degrees on them and I would lay a panel on it at those angles. So, lets say that the first 6 inch is 30 degrees, then 8 inches is 40 degrees. Crude but workable DiY design. And it does not have to be perfect. TIA.
 
Thank you, guys, thus far. bookmarked for the angle lookup. Still searching, however, because I also would like to build a user-friendly app. I just need to find a database of this info to plug into a custom db I might build for the app.
 
Thank you, guys, thus far. bookmarked for the angle lookup. Still searching, however, because I also would like to build a user-friendly app. I just need to find a database of this info to plug into a custom db I might build for the app.
You don't need an app. There are already dozens of them.

There is only one way to get a perfect angle but it comes at a cost, the dual-axis tracker.

The least costly method is;
optimal angle is whatever your latitude is.

If possible adjust the angle two or three times a year to perpendicular at solar noon.

A single-axis slewing panel will follow the sun, sunrise to sunset at whatever angle your latitude is.

If you want to help fight "The Duck Curve" put your panels on west-facing roofs.

There is always a compromise. If money is no obstacle, dual-axis wins the production output every time.
 
I use ground deployment panels with my RV trailer. They get setup each time I park for more than a couple days.

I use an Android app called "Optimal Tilt". It works good. I don't change the panels once they're setup unless I inadvertently put them in shade.
 
I decided to look at my tilt angles. My rv tilt brackets in the last holes on end are @30* yesterday my 720w array saw 523w max. Generated 2.53Kwh

Today was mostly cloudy but some sun got through. Tilted to 49* I saw a peak of 668w tilting is huge! can't wait for a sunny day!

From what I read I found my latitude and added 15* for winter sun.
 
If you're going for a fixed position, you can always split the difference between your summer and winter solstice angles. Or if you're wanting the maximum power for expected outages (using your system as a power backup unit) then it depends on the season that causes you problems the most. For example, Houston TX experiences most of it's power outages due to tropical storms and hurricanes, so the summer angle of just over 83.7 deg would be the target. Once you get up in the midwest, then you've got to figure on winter storms being the main problem, so a lower angle of the winter position would be more suitable.
 
So after reading this thread and playing with some apps last night I increased my angle from about 28 deg to about 40 deg. My peak wattage increased by over 20% to 2085. Not bad for an array of used 250 watt panels in SE PA on the last day of sept
 

Attachments

  • BFEF11B8-5F1B-4575-9CA3-F629540AC265.jpeg
    BFEF11B8-5F1B-4575-9CA3-F629540AC265.jpeg
    351 KB · Views: 21
It all depend for what you want to optimise.
- On grid you want to get the maximum on sunny days.
- Off grid, you may want to get the maximum on cloudy days: the panels are tilted more horizontally.
 
Would you not want to maximize daily harvest in both cases? Why would the more diffuse light if cloudy days be optimized by a more shallow angle?
 
Would you not want to maximize daily harvest in both cases? Why would the more diffuse light if cloudy days be optimized by a more shallow angle?
In sunny days, the battery is full at 12:00 and then, I throw energy away anyhow. Why optimising?
The problem is to get the max on cloudy days, where I hardly get enough to balance the daily consumption.
Then the light comes from everywhere and a roughly flat panel delivers the best output.
 
Panels are cheaper than tracking mounts.
Use two arrays, one oriented toward AM sun and one toward PM. They can be wired in parallel to a single MPPT.
If you need more power in winter, have a 3rd array oriented South with winter tilt.

Would you not want to maximize daily harvest in both cases? Why would the more diffuse light if cloudy days be optimized by a more shallow angle?

What I've heard is, the light source is straight overhead: the clouds.
A panel with steep tilt for winter sun has part of its (off-angle) exposure from the ground, which isn't a good source of light.
 
In sunny days, the battery is full at 12:00 and then, I throw energy away anyhow. Why optimising?
The problem is to get the max on cloudy days, where I hardly get enough to balance the daily consumption.
Then the light comes from everywhere and a roughly flat panel delivers the best output.
Aha, I may see my uniqueness. I never fill a battery my target max is 85%. That and a small array means that my limits are low side, not highside
 
Use two arrays, one oriented toward AM sun and one toward PM. They can be wired in parallel to a single MPPT.
That’s my next experiment is to split my single series into 2 4-panel banks with one at about a 175 azimuth the other at 185 to start
 
So here is today’s grouping. 4 on the right are at about 170 deg azimuth 40 deg tilt. Those on the left upper are at 200 deg azimuth lower 225degree azimuth same approx tilt. Left and rank banks are 2 4-panel arrays into the single MPPT of the LVX
 

Attachments

  • B5BED517-23E7-4ED6-A895-1208E5D207EA.jpeg
    B5BED517-23E7-4ED6-A895-1208E5D207EA.jpeg
    566.8 KB · Views: 9
So here is today’s grouping. 4 on the right are at about 170 deg azimuth 40 deg tilt. Those on the left upper are at 200 deg azimuth lower 225degree azimuth same approx tilt. Left and rank banks are 2 4-panel arrays into the single MPPT of the LVX

Those are all pretty similar orientation.
Can you graph power produced during the day?
Compare what you've got with half aimed at 10:00 AM sun and half at 4:00 PM. (maybe 10:00 and 3:00, given shorter days now.)
I think it will reduce peak to about 70% as high (for 6 hour, 90 degree orientation difference) but extend hours. That should hold battery SoC more constant through the day, enter evening with higher SoC.

That and a small array means that my limits are low side, not highside

Large array and throw out unneeded production is the way to go. PV is cheaper than battery.
 
Large array and throw out unneeded production is the way to go. PV is cheaper than battery.
but permission from wife to FU her zen and sight lines with solar panels for my hobby is priceless, and the real constraint. That’s also why that dogwood that casts the morning shadow still lives too BTW
 
I was going to a proper 20 degrees for Cabo San Lucas, MX. Then I went through a cat 2 hurricane last month. One of my panels (not mounted) flew 60 ft. Now I'm going to do flat and just add more panels to compensate. Try not to let much air get underneath then. Highest gust was 110 mph so I can't image hurricane Odile 140mph sustained for at least one minute.
 
Back
Top