Steep angle solar panels

alfaeric

Solar Enthusiast
Joined
Jan 21, 2020
Messages
240
I see there are a number of posts asking about ideal angle, but has anyone studied output vs. sun angle for various panels?

In today's solar panel video that Will posted, he started out by doing a quick angle study, which made me thing of this question. Especially since the most likely build I'll do in the future is a travel trailer- where the panels will be fixed angle.

So I was wondering if the most efficient panels overall also give the widest angle efficiency as well. Peak power is important, but overall power during the day will be more important, I think.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,365

alfaeric

Solar Enthusiast
Joined
Jan 21, 2020
Messages
240
Here's an article on the topic


Coatings could improve acceptance of light at off-angle


You may find geometry is the dominant factor. Maybe a manual tilt you can access if you need to boost power production.
But the way, we understand that flat facing up is best during overcast winter weather.
Great paper- not that I read everything, but I did get to the heart of the data. Even though it's over 7 years old, the results seem that they would not have changed- given the results. I was kind of hoping that some technology would be more robust to angle of incidence, but seeing that they are all the same, it's going to come down to the best overall value for our situation.

Thankfully, we have time on our side- before making the jump to be solar capable, we need to record and track our power usage. And by the time I have really good data, there should be some more progress in both solar and battery tech.
 

fratermus

Solar Addict
Joined
Mar 19, 2021
Messages
223
I was wondering if the most efficient panels overall also give the widest angle efficiency as well

I suspect effective panel area (as dictated by the cosine of solar zenith angle) dominates the situation.

overall power during the day will be more important

We might assume the best "wide angle" panels would still be less effective than 2-axis tracking, and my reading suggests 2-axis tracking yields ~+10% power over daily optimal positioning (best static position for any given day). If so, it seems easier/cheaper to add panel than to track or invest in $$$ panels.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,365
Solyndra featured no reduction in output vs. sun's angle (in one axis.)
With cylindrical cells spaced apart, they present the same area toward the sun over a range of angle, until one starts to shade the next.
Of course, they had circumference = pi x D thin-film PV material in order to present "D" width to the sun.
If placed on a white roof, they work like bi-facial panels.

I thought that was their entire claim to fame (you pay for pi x D material to get D worth of collector area) until someone I know (who declined an offer to run the company) said their real advantage was that wind can pass between the tubes. It is easy to install with ballast instead of roof penetrations.

My approach is to buy low-tech flat PV panels made from thick silicon wafers (thicker stops more photons) and place pairs of panels in an inverted "V", to similarly catch light over a range of angles. To be more effective than a flat array, rows of these have to be quite far apart to avoid shading. So better to just have one pair of arrays with different orientations; this will cast a long shadow in the early and late hours.

... and my reading suggests 2-axis tracking yields ~+10% power over daily optimal positioning (best static position for any given day). If so, it seems easier/cheaper to add panel than to track or invest in $$$ panels.

I usually see the figure 45% more. But still better to add panels.
 

HRTKD

Boondocker
Joined
Apr 24, 2020
Messages
5,979
Location
Somewhere South of Denver
We might assume the best "wide angle" panels would still be less effective than 2-axis tracking, and my reading suggests 2-axis tracking yields ~+10% power over daily optimal positioning (best static position for any given day). If so, it seems easier/cheaper to add panel than to track or invest in $$$ panels.

Like Hedges, the number I've heard from dual-axis tracking is 40% better output. But the low tech solution of adding more panels is often more cost effective. Trackers are expensive and require some upkeep. If I was limited on space, a dual axis tracker would be the way to go.
 

fratermus

Solar Addict
Joined
Mar 19, 2021
Messages
223
Like Hedges, the number I've heard from dual-axis tracking is 40% better output.

I will back off my "+10% over daily optimal" claim, since I can't find any research on daily optimal. I had a vehicle dweller in mind who would tweak the panel position slightly each day in accordance with the ephemera.

Here is some research on differences between 2-axis and single-position (fixed) optimal:

Irradiation incident on a 2-axis tracking panel in one year was 25%–45% higher than irradiation received by a panel at optimum fixed orientation - source

So 45% appears to be the extreme end of the spectrum, although admitted more realistic than my +10% claim.

Surprisingly (to me at least) 2-axis tracking appears to have little advantage over single-axis tracking:

At virtually all latitudes, 1-axis horizontal tracking receives within 1–3% the incident solar radiation as 2-axis tracking - source
 

Ironman

Solar Enthusiast
Joined
Nov 29, 2020
Messages
81
Great paper- not that I read everything, but I did get to the heart of the data. Even though it's over 7 years old, the results seem that they would not have changed- given the results. I was kind of hoping that some technology would be more robust to angle of incidence, but seeing that they are all the same, it's going to come down to the best overall value for our situation.
I wonder if anyone has done the data on the weak morning and evening sun at about 50 latitude. I am curious about gains from casing the rays by angling to morning and evening sun, or how small they would be.
 

LR~Eagle

New Member
Joined
Mar 29, 2021
Messages
13
You can model all these options using this site and see how your output in KWHs changes...

 

Bluedog225

Texas
Joined
Nov 18, 2019
Messages
191
I’ve got a different take on this. Specifically, thinking about some fixed east and west facing panels, say 45 degrees or more, to capture the morning and evening sun to flatten the curve and reduce battery time by … a couple of hours?

Looking at the PV watts hourly numbers, you do lose a lot of production through the day at 75 degrees west tilt. But you can pick up some good generation 4-6 pm at which time it all goes away. Noticeably better pickup in the morning with east facing panels at 75 degrees.

Saving 5000 watts or so of storage might be worth factoring in as it relates to terms of battery cost.

I’m just dipping my toe into solar calculation so take this with a large grain of salt.
 

niktak11

Solar Enthusiast
Joined
Mar 14, 2021
Messages
90
Great paper- not that I read everything, but I did get to the heart of the data. Even though it's over 7 years old, the results seem that they would not have changed- given the results. I was kind of hoping that some technology would be more robust to angle of incidence, but seeing that they are all the same, it's going to come down to the best overall value for our situation.

Thankfully, we have time on our side- before making the jump to be solar capable, we need to record and track our power usage. And by the time I have really good data, there should be some more progress in both solar and battery tech.
There is no overcoming trigonometry. You could try using mirrors to reflect more light at the panel if you need more output at a steep angle.
 
Top