Projected zenith convenience function #1904
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@@ -232,3 +232,76 @@ def sky_diffuse_passias(masking_angle): | |||||
| Available at https://www.nrel.gov/docs/fy18osti/67399.pdf | ||||||
| """ | ||||||
| return 1 - cosd(masking_angle/2)**2 | ||||||
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| def projected_solar_zenith_angle(axis_tilt, axis_azimuth, | ||||||
| solar_zenith, solar_azimuth): | ||||||
| r""" | ||||||
| Calculate projected solar zenith angle in degrees. | ||||||
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| This solar zenith angle is projected onto the plane whose normal vector is | ||||||
| defined by ``axis_tilt`` and ``axis_azimuth``. The normal vector is in the | ||||||
| direction of ``axis_azimuth`` (clockwise from north) and tilted from | ||||||
| horizontal by ``axis_tilt``. See Figure 5 in [1]_: | ||||||
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There was a problem hiding this comment. Does that mean the axis of tracker rotation is the surface normal vector we're talking about? There was a problem hiding this comment. From Figure 5 caption:
I'm pretty sure it is. Do you think this line of text is worth to be added to the current caption? I didn't want to copy-paste the paper content. There was a problem hiding this comment. How about:
Suggested change
That puts a picture in my mind! There was a problem hiding this comment. That's more focused on tangible parts, I like it. Nonetheless, I'm a bit hesitant to change that since there is ongoing discussion regarding the tracking or fixed support nomenclature. And that suggests SAT. There was a problem hiding this comment. No worries, I wasn't actually expecting this wording to be adopted. :) |
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| .. figure:: ../../_images/Anderson_Mikofski_2020_Fig5.jpg | ||||||
| :alt: Wire diagram of coordinates systems to obtain the projected angle. | ||||||
| :align: center | ||||||
| :scale: 75 % | ||||||
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| Fig. 5, [1]_: Solar coordinates projection onto tracker rotation plane. | ||||||
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| Parameters | ||||||
| ---------- | ||||||
| axis_tilt : numeric | ||||||
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There was a problem hiding this comment. For a general purpose function, would There was a problem hiding this comment. There's a comment up there from @kandersolar asking for changes from I'll request reviews for the current reviewers hoping they also give some insight regarding this. Anyway, if you are sure of it, I change it without no problems. There was a problem hiding this comment. Is the issue that I'm inclined (pun intended) to keep the term Perhaps a good compromise is to clarify that point in the parameter description/Notes? There was a problem hiding this comment. I feel like these two terms refer to pure maths, and mapping those words to concise real-world systems is a bit counter-productive due to the variability. Is there some generic -maths- term we can use for a general description of this, a projection? Like Just to weight in some more options outside of the current frame:
I don't dislike this possibility if we don't agree on anything else eventually, but we are overcomplicating the docs IMHO. BTW, I'm +1 for the There was a problem hiding this comment. I admit to suffering from tunnel vision for trackers, but in my view How about: Similar for |
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| Axis tilt angle in degrees. From horizontal plane to array plane. | ||||||
| axis_azimuth : numeric | ||||||
| Axis azimuth angle in degrees. | ||||||
| North = 0°; East = 90°; South = 180°; West = 270° | ||||||
| solar_zenith : numeric | ||||||
| Sun's apparent zenith in degrees. | ||||||
| solar_azimuth : numeric | ||||||
| Sun's azimuth in degrees. | ||||||
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| Returns | ||||||
| ------- | ||||||
| Projected_solar_zenith : numeric | ||||||
| In degrees. | ||||||
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| References | ||||||
| ---------- | ||||||
| .. [1] K. Anderson and M. Mikofski, 'Slope-Aware Backtracking for | ||||||
| Single-Axis Trackers', National Renewable Energy Lab. (NREL), Golden, | ||||||
| CO (United States); | ||||||
| NREL/TP-5K00-76626, Jul. 2020. :doi:`10.2172/1660126`. | ||||||
| """ | ||||||
| # Assume the tracker reference frame is right-handed. Positive y-axis is | ||||||
| # oriented along tracking axis; from north, the y-axis is rotated clockwise | ||||||
| # by the axis azimuth and tilted from horizontal by the axis tilt. The | ||||||
| # positive x-axis is 90 deg clockwise from the y-axis and parallel to | ||||||
| # horizontal (e.g., if the y-axis is south, the x-axis is west); the | ||||||
| # positive z-axis is normal to the x and y axes, pointed upward. | ||||||
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| # Since elevation = 90 - zenith, sin(90-x) = cos(x) & cos(90-x) = sin(x): | ||||||
| # Notation from [1], modified to use zenith instead of elevation | ||||||
| # cos(elevation) = sin(zenith) and sin(elevation) = cos(zenith) | ||||||
| # Avoid recalculating these values | ||||||
| sind_solar_zenith = sind(solar_zenith) | ||||||
| cosd_axis_azimuth = cosd(axis_azimuth) | ||||||
| sind_axis_azimuth = sind(axis_azimuth) | ||||||
| sind_axis_tilt = sind(axis_tilt) | ||||||
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| # Sun's x, y, z coords | ||||||
| sx = sind_solar_zenith * sind(solar_azimuth) | ||||||
| sy = sind_solar_zenith * cosd(solar_azimuth) | ||||||
| sz = cosd(solar_zenith) | ||||||
| # Eq. (4); sx', sz' values from sun coordinates projected onto surface | ||||||
| sx_prime = sx * cosd_axis_azimuth - sy * sind_axis_azimuth | ||||||
| sz_prime = ( | ||||||
| sx * sind_axis_azimuth * sind_axis_tilt | ||||||
| + sy * sind_axis_tilt * cosd_axis_azimuth | ||||||
| + sz * cosd(axis_tilt) | ||||||
| ) | ||||||
| # Eq. (5); angle between sun's beam and surface | ||||||
| theta_T = np.degrees(np.arctan2(sx_prime, sz_prime)) | ||||||
| return theta_T | ||||||
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