Optimal Fixed Solar Panel Angle?

[WattAboutThat]

I originally thought that I would want a seasonal adjustment to get the max production all year long.

Then I went to Solar Power Calculator at
pvwatts.nrel.gov

and started calculating different gains and losses
throughout the year at various angles.

My conclusions were:

At my Latitude of 39.45 degrees N

That an angle of 45.4 degrees above the horizontal plane, which would be an elevation angle for sun at 44.6 degrees above horrizon,

That I would only lose 0.05% of max capability on the best summer day,

and I only lose 0.001% i of max in winter

So it seems logical to just set it at 45.4 degrees
all year long.

I would love to hear your opinions
on if this is correct thinking, or if I have overlooked or miscalculated.

Thanks

 

[DIYrich]

If you have net metering, then whatever angle maximizes annual production.
Otherwise, maximize self-consumption, which may be optimize winter production (over paneling for lower winter production).

 

[WattAboutThat]

If you have net metering, then whatever angle maximizes annual production.
Otherwise, maximize self-consumption, which may be optimize winter production (over paneling for lower winter production).

Completely off grid.

 

[tellingson]

Completely off grid.

If you have lots of snow, consider a steeper angle like 50 for better snow shedding.

 

[Shimmy]

What impact does it have on your worst day though?

 

[timselectric]

In summer, I get so much production. I could stand the panels vertical and get enough to cover my needs.
I think that it's best to design for winter. The rest of the year is never a problem.

 

[Steve_S]

My ground mount is set to 45 degrees which is the optimal year-round production angle for me, max generation, therefore, occurs in March & September. I am quite North near Algonquin Park Ontario so as you can imagine I get a LOT of snow in winter, 1'+ snowfalls are normal and even @ 45 degrees it sticks and can get up to 2' thick before it slips off. Fortunately being a ground mount with the lowest edge @ 4' off the ground I can brush it off with a Foam Brush (never use anything that can scratch or has a hard edge of any kind).

Don't get caught up on precision minutia, it will only serve to create stress and there isn't any point. Even making your rack 44 or 46 degrees will NOT make much difference in the grand scheme... The worst that will happen is your optimal generation may change by a few days... Really, it is NOT that significant so don't stress on it. As I stated above my Optimal Generation is Mar & Sep, my 2080W Array will actually get up to 2200W for about an hour (which is not unusual for panels). The GOTCHA right here !

The GOTCHA here is that all solar panels can actually produce more than their rating for various reasons like direction/angle, cooler temps and such. The FAIL part is when people calculate their solar array for their controllers they must account for that extra generation that can & does happen. Some Solar Charge Controllers like Midnite Solar have a feature called HyperVOC to address that and handle over generation, other SCC's do not and so it has to be accounted for. IF this is not accounted for and you over generate beyond the SCC's capabilities you can burn it out.

Also I want to point out something else that too many get buggered up on... Assume the software says you need to aim your panels Directly South (by compass point) @ 45 Degrees angle. You can be +/- and the Angle as it will only change the optimal generation "time period" by a few days either way. As for the E-W direction, again if not perfect it's NOT a big deal, that only shifts the time when you are generating max... IF at perfect South then at Noon on June 21st you hit peak production but if you are 2 degrees east or west from direct south, then your optimal generation time maybe offset by 20 Minutes either way... These values are just used as an example.

Lesson Learned Dept:
Optimal Annual Generation angle works fine BUT depending on location then not necessarily optimal in the grand scheme. Today I will see 15 Hours of sunlight and am in float by noon.... Pretty Cool right ! In December I may get 3.5 Hours of sunlight and won't get to float (with current setup, being updated this summer). Summer Generation is no problem for obvious reasons but not in Winter. Changing my panels to 36 Degrees will change my Optimal Generation window to Feb & Oct or @ 28 Degrees for optimal Jan & Nov. That would improve generation in winter and also enhance the Snow Shedding and reduce my generation in summer but that is compensated for by the amount of Sun Hours everyday.

Anyone installing Solar on a Roof needs to work out Roof Pitch / Degrees.

Roof Pitch Calculator​

Calculate roof pitch by entering the rise and run or the angle in degrees. Learn more about measuring roof pitch and the rise and run below.

Hope it Helps, Good Luck

 

[Solar Guppy]

Typically angles are relative to the ground and are the inverse of what the image shows above and the advice for annual best production is tilt is equal to latitude of the installation with the below reference.

For example, if the solar panel is flat on the ground and the sun is directly overhead, that is considered and angle of zero. The higher the latitude the higher the angle needed to be perpendicular to the Sun, as the Sun is lower in the horizon.

See HERE for more information

 

[timselectric]

My optimal angle is based on the tree tops on the hill to the south. lol

 

[Mike 134]

I originally thought that I would want a seasonal adjustment to get the max production all year long.

Then I went to Solar Power Calculator at
pvwatts.nrel.gov

and started calculating different gains and losses
throughout the year at various angles.

My conclusions were:

At my Latitude of 39.45 degrees N

That an angle of 45.4 degrees above the horizontal plane, which would be an elevation angle for sun at 44.6 degrees above horrizon,

That I would only lose 0.05% of max capability on the best summer day,

and I only lose 0.001% i of max in winter

So it seems logical to just set it at 45.4 degrees
all year long.

I would love to hear your opinions
on if this is correct thinking, or if I have overlooked or miscalculated.

Thanks

Unless there's a rocket scientist hiding on this DIY site giving advice, I'd go with the results from PVwatts.
Mine are mounted on an 8/12 pitched roof which is a 33 degree incline and wet snow slides right off. Sounds like you're going to have a ground mount since you were thinking of adjusting the angles so snow is not an issue for you to remove.

 

[WattAboutThat]

My ground mount is set to 45 degrees which is the optimal year-round production angle for me, max generation, therefore, occurs in March & September. I am quite North near Algonquin Park Ontario so as you can imagine I get a LOT of snow in winter, 1'+ snowfalls are normal and even @ 45 degrees it sticks and can get up to 2' thick before it slips off. Fortunately being a ground mount with the lowest edge @ 4' off the ground I can brush it off with a Foam Brush (never use anything that can scratch or has a hard edge of any kind).

Don't get caught up on precision minutia, it will only serve to create stress and there isn't any point. Even making your rack 44 or 46 degrees will NOT make much difference in the grand scheme... The worst that will happen is your optimal generation may change by a few days... Really, it is NOT that significant so don't stress on it. As I stated above my Optimal Generation is Mar & Sep, my 2080W Array will actually get up to 2200W for about an hour (which is not unusual for panels). The GOTCHA right here !

The GOTCHA here is that all solar panels can actually produce more than their rating for various reasons like direction/angle, cooler temps and such. The FAIL part is when people calculate their solar array for their controllers they must account for that extra generation that can & does happen. Some Solar Charge Controllers like Midnite Solar have a feature called HyperVOC to address that and handle over generation, other SCC's do not and so it has to be accounted for. IF this is not accounted for and you over generate beyond the SCC's capabilities you can burn it out.

Also I want to point out something else that too many get buggered up on... Assume the software says you need to aim your panels Directly South (by compass point) @ 45 Degrees angle. You can be +/- and the Angle as it will only change the optimal generation "time period" by a few days either way. As for the E-W direction, again if not perfect it's NOT a big deal, that only shifts the time when you are generating max... IF at perfect South then at Noon on June 21st you hit peak production but if you are 2 degrees east or west from direct south, then your optimal generation time maybe offset by 20 Minutes either way... These values are just used as an example.

Lesson Learned Dept:
Optimal Annual Generation angle works fine BUT depending on location then not necessarily optimal in the grand scheme. Today I will see 15 Hours of sunlight and am in float by noon.... Pretty Cool right ! In December I may get 3.5 Hours of sunlight and won't get to float (with current setup, being updated this summer). Summer Generation is no problem for obvious reasons but not in Winter. Changing my panels to 36 Degrees will change my Optimal Generation window to Feb & Oct or @ 28 Degrees for optimal Jan & Nov. That would improve generation in winter and also enhance the Snow Shedding and reduce my generation in summer but that is compensated for by the amount of Sun Hours everyday.

Anyone installing Solar on a Roof needs to work out Roof Pitch / Degrees.

Roof Pitch Calculator​

Calculate roof pitch by entering the rise and run or the angle in degrees. Learn more about measuring roof pitch and the rise and run below.

Hope it Helps, Good Luck

View attachment 152165

Thank you for this excellent anslysis!

 

[LydMekk]

I have filled my south-facing roof with panels, approx 30 degrees.
Contemplating mounting 6 extra panels flat (90 deg) on a white sidewall pointing east...
Should also help in winter, because as Tim says the summer production is never a problem.

 

[mountkay]

Im completely off-grid with a ground mount array. I took data from PVwatts for each angle and put it into a chart and made a graph; it was easier for me to visualize it this way.

I found out that as the angle increased, I would be sacrificing quite a bit of summer production for barely any gains in winter .

I still would have liked to go with a 55deg angle, being off grid winter would be most important.
Going any steeper than 55 seemed like it gained me almost nothing in winter.

KWH/Month/Degree of angle


Total Yearly KWH / Deg of angle

I ended up going with 40deg because of the amount of extra metal pipe and concrete that would be needed to go at a steeper angle (Iron-Ridge ground mount). Basically as the angle increases, you are making more of a sail like structure that will catch more wind. I think I would have found a way to buffer the wind, maybe with some greenhouse plastic, but I had to build it to code for my building inspector. This means it had to withstand 115mph winds, although I dont think I will ever see anything close to that. I figured that after I passed inspection I could add a smaller array specifically designed for winter if I need it.

At 40deg the snow sheds off pretty well. Not the best, and I still have to use a snow brush quite a bit, but if temps get above freezing, the backside of the snow melts and it slides off on its own. In the picture below, the snow slid off on its own.