Solar Panel Tilt Bracket Ideal Azimuth Formula Strike Angle

[albert436]

Headed off to the dentist in a few minutes and will try to get my mind around all of that later.

But basically, for aesthetic reasons I would think it best to keep one edge of the panels flush to the roof surface, as shown in the photo posted at the beginning of this thread:

(Don't you think this would look better, and would it be be better able to be securely fastened?)

[posplayr]

I totally get this.



I'm was thinking that because the angle doesn't have to be very much, like in the range of 22 degrees (?), that the rows of panels might not have to be spaced too far apart. That's presuming they are placed in landscape orientation. But would we lose some sun in the afternoon sun just due to the angle of the roof itself, compared to if they were on a flat roof or a roof that actually was facing SSE ?

Inquiring minds want to know !

The issue becomes how high above the roof you can mount the panel or how strong your mounting structure is for additional leverage a high mounted array would have. If the panel is it is high enough above the roof there is no roof interference limitations.

With the method I described, you can translate any optimal program fixed angle solution by a roll orientation change to new panel orientation whose horizontal projection matches your roof orientation. You have to look at how much height you will need to mount that panel, but before imposing a height limit it will have the same inertial point angle as the unconstrained optimal panel angle.

Matching the roof horizontal projection will give you the largest contiguous dimensions for a side (of the array) and so there will be no shading of panels on that plane. If it is too tall you will have to start making compromises to limit the angles or break up the panel allowing for spacing (lower panel density). If you only have one space(between panels) it is not as good as no spaces but it is better than any other arrangement.

[albert436]

There are other rotations that will give you the same panel normal angle to a local geographic frame.You can visualize this by orienting your panel ideally in az (180 due south) and tilt (or pitch) as optimally calculated and then spin the panel around it's center in the plane of the panel. That entire closed set, a full rotation in roll, represents a continuum of an infinite number of orientations that are all also optimal.

I totally get this.

More specialized software (incorporating the solar path) is necessary to determine how to lay out the panels to avoid external and self-shading in the compound orientation.

I'm was thinking that because the angle doesn't have to be very much, like in the range of 22 degrees (?), that the rows of panels might not have to be spaced too far apart. That's presuming they are placed in landscape orientation. But would we lose some sun in the afternoon sun just due to the angle of the roof itself, compared to if they were on a flat roof or a roof that actually was facing SSE ?

Inquiring minds want to know !

[albert436]

This is getting really interesting, thanks everyone for the comments.

It will take me a while to get my mind around some of it.

JPM, here's what I'm trying to figure out, or actually was trying to figure out would be more accurate, but now my curiosity has been piqued.

My mom's house had some shading issues which were resolved last week when several giant trees at a neighbors house were cut down.

Prior to that I was looking at the options for panel placement. The roof of her garage has a lot of room facing in an ENE direction, which is not particularly optimal. The roof has a fairly standard pitch for a California ranch. I was wondering whether tilting the panels "sideways" toward the south would give me a more favorable angle. If so, how much of a tilt would be optimal, and how much better would it be ? Does tilting them sideways change their direction to SSW ? And how much etc etc. For some reason this has got me slightly fascinated.

Hope that clarifies things.

[J.P.M.]

Albert: What are you actually looking for and for what purpose ?

If you are looking for the angle of incidence between the incoming direct (beam) solar irradiance and the normal to a flat surface of any random orientation, that information can be easily calculated by hand or machine. I'd suggest the hand calc a few times to understand the concepts, but doing that and suggesting such a thing seems to be anachronistic.

If you are looking for the optimum orientation to maximize the amount of solar radiation incident over a period of time for a clear sky, that calculation involves more than angles of incidence.

If you let me know what it is you are looking for and for what purpose, I believe I can point you in some correct directions. Euler angles, or direction cosines are one way to look at it. they are useful for many things. I've used them in engineering work unrelated to anything here. But, if I understand what I think you are asking, they won't get you where you want to go.

[sensij]

But for the sake of academics--how do you figure these angles?

I use 3D modelling software to figure out the equivalent Azimuth/Tilt plane for Poa irradiance calculations created when a panel is oriented with azimuth, tilt, and "sideways tilt", as you called it. More specialized software (incorporating the solar path) is necessary to determine how to lay out the panels to avoid external and self-shading in the compound orientation.

NREL's SAM (System Advisor Model) has a 3d shade modelling engine... it is free, but takes some time to learn.

[posplayr]

Reviving this thread just out of curiosity. The neighbors have cut down some trees so I don't need to worry about it.

But for the sake of academics--how do you figure these angles?

Anyone have any ideas?

I might have asked about this on another thread, I think I referred to it as a "sideways tilt".

Have you ever heard of Euler Angles?

The optimal solar angle is implicitly a two angle rotation AZ then, tilt (pitch). This is not a unique solution and can be arrived at with other rotations. See a review of Euler angles. If it was unique, then that would say your final roll angle has to be something specific but indeed the solar energy captured is only a function of incidence angle in two dimensions and not three. Landscape and Portrait orientation are but two of a continuum infinite set of optimal solutions defined by a full rotation about the normal.

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&es_th=1&ie=UTF-8#q=euler%20angles

There are other rotations that will give you the same panel normal angle to a local geographic frame.You can visualize this by orienting your panel ideally in az (180 due south) and tilt (or pitch) as optimally calculated and then spin the panel around it's center in the plane of the panel. That entire closed set, a full rotation in roll, represents a continuum of an infinite number of orientations that are all also optimal.

In summary:
The optimal panel orientation is one where the panel normal is oriented south at a tilt angle nominally equal to your Latitude. One way (the conventional one) to achieve this is to perform an AZ rotation of a flat panel so it is orientated N-S ( in either landscape of portrait) and then add a tilt equal to Latitude. Any rotation about that panel normal (imagine a vector coming out perpendicular from the panel) is also an optimal panel orientation. If you do a virtual spin of the panel, you will find an an azimuth angle (or approximately a projection to the ground) that matches your house orientation.


If you follow all of this we an work on how to do it analytically if you have trouble with that.

And yes there is something else called Quaternion which would do the same as Euler angles, but I'm trying to keep this simple.

PS: most all of the terminology I have used is in common usage in aerospace, aeronautical engineering or mechatronics. Apparently not so common in solar, I apologize for any confusion.

[albert436]

Reviving this thread just out of curiosity. The neighbors have cut down some trees so I don't need to worry about it.

But for the sake of academics--how do you figure these angles?

Anyone have any ideas?

I might have asked about this on another thread, I think I referred to it as a "sideways tilt".

[Badore]

That's not Really what I was asking about

I attached a picture of what I am planning to do. The calculations can't be done with typical software. I will need to come up with a formula.

[SunnyTimes]

here another simple tool, for few regions around the world.. http://valentin-software.com/xcartgo...lculation.html

[Mike90250]

Go to (RUN, dont' walk) the PV Watts site http://mapserve3.nrel.gov/PVWatts_Viewer/index.html and enter your location and PV size & angles. You can play around and see what gives you the most. I set my array for winter harvest, summer I have extra.

[Badore]

I have a W facing roof with no shade on a 35 Degree angle. My latitude is 43 Degrees. I have installed my panels on a 15 Degree angle facing S. What is the actual Azimuth to use in my calculations for output? Does anyone know the Formula? I need to know what to put into the Solar Pathfinder Assistant software.

This is what I have so far: the ideal tilt for max production based on weather data for my area is 34 Degrees. From what I can tell the panels are not really facing straight South. As the angle of the roof gets steeper the panels would start facing more West, right? But since the Sun is at a lower angle in the afternoon the ideal angle for a West facing roof would be steeper than 34 Degrees.

Suppose 34 is my ideal tilt on flat roof facing South. As I tilt the roof to the right the panel starts to face away from the ideal 34 Degrees x 180 Degrees, right?

I have attached a picture of another project. I install systems under the Ontario microFIT program and knowing this would allow me to boost production on my customers roofs.