Rivian's New Amazon Delivery Van

[GeorgeRa]

Originally Posted by dhectorg

Nonsense. Why is it so hard for some people to just acknowledge that they were wrong? The benefits of tilting solar panels is well documented all over the web. Doing this can absolutely realized huge gains throughout the day, anytime the sun isn't directly overhead. This isn't complicated.

There is no question that mounting panels allowing tilting has value during times when the Sun is low, such as winters, northern states, sunsets or sunrises but implementation is complex. Any system which would improve usability would make it even more complex. Most of tilting mounts allow tilting to one side only, which reduces choices for campsites. AM Solar has nice mounts allowing tilt to both sides but climbing on the roof is necessary.

Your point that folks don’t recognize the harvesting benefits of tilting, I think they do, but they evaluate if there is bang for the buck, and for most there isn’t.

There was a discussion on the Sprinter forum how to increase harvesting by stocking panels vertically, I had idea of sliding panels left and right, Avanti thought about using parallelograms, someone had a solar panel moving out from under a roof cargo panel. https://sprinter-source.com/forum/sh...g+solar+panels

So, don’t be so quick in thinking that the reason that most folks having flat PV panels is because they don’t understand the value of tilting, they do, but they see reality of mounting and using complexity.

[booster]

Here is a link to a thread I started about how to calculate the total potential harvesting from solar panels over a full day, anywhere on earth, any time of the year, for horizontal panels. It is not an "under the curve" calculus integration, but estimates the area by doing quite a few points.


http://www.classbforum.com/forums/f2...html#post57708


It would be pretty easy to just change the solar angle part of the equation to 90* all day, I think, for each of the calculation points and use the same method to get a total for the day with perfect tracking, harder for to calc for single tilt, as you would have two angles to put in. It would be very, very, interesting to see just how much you would actually gain over a day with perfect tracking.



I can tell you that there have been quite a few tiltable panel installs done over the years, and from what followup there has been, most are likely being used flat nearly all the time because of the hassle of tilting and the inability or difficulty of trying to get the van in right direction to get much benefit, from what I have seen and read.


Of course, you will not get 90* to the panel unless you can tilt and track so would need to be moving the panels on two axis continually, so has to be automatic and powered, which would use some of the gain for sure.


I think we all have to be careful when evaluating this kind of stuff to understand how the "maximum possible" compares with the "actual reasonably attainable". In this case, it is also very important to remember that the gains very early and very late in the day are going to be much higher in % than later in the day when the sun is higher, even with perfect tracking. The only real way to evaluate is to do the calculations like mentioned above, covering the entire day, for both types of panel orientation.



Interesting to me is that with a tilted panel facing straight south on longer days, you would likely get no solar input in the early morning and late afternoon as the sun would be coming up and going down north of the panel axis and not hit it.


Most of the articles I have read, and installations I have seen for permanent solar locations is that tilt is worth the effort, but not auto variable tilt, and full tracking is more trouble than it it worth. Solar farms appear to be fixed position and tilted at an angle that is the average of the yearly sun height at noon, at least around here.

[avanti]

I agree with all of the above. But, let's remember that the original claim was

Originally Posted by dhectorg

I've seen 22' Sprinter vans with 1000 watts of solar installed. That amount of solar can fully charge a large chassis battery bank over a few days, as well as charging the smaller house battery.

This claim is a non-starter based on the basic physics of the situation. The math is not hard.

The equally-dubious "increase output by many multiples" claim comes later.

Plus, we haven't begun to talk about shade, weather or longitude.

[booster]

Originally Posted by avanti

I agree with all of the above. But, let's remember that the original claim was



This claim is a non-starter based on the basic physics of the situation. The math is not hard.

The equally-dubious "increase output by many multiples" claim comes later.

Plus, we haven't begun to talk about shade, weather or longitude.

Yep, totally agree. This comes under the "actual reasonably attainable" I mentioned above. I think the theoretical for a flat panel of 18% or so efficiency is above 50ah/day IIRC, but most of us have found that if we get closer to the "rule of thumb" of about 30+ah/day in decent conditions. Add bad conditions and it goes down more very quickly.

[booster]

I am not a mathematician by any stretch, so this may be way off, but here goes. Of course this assumes the sun angle is a sine wave to the panel which may not be true.


I just looked up what the area under a sine wave curve is and found this link.


https://girlsangle.wordpress.com/201...actly-equal-2/


It says the area is always 2 regardless of amplitude. A sinewave crosses at 3.14 for an amplitude of 1, so the area if you were always perpendicular sin = 1) to the sun would be 3.14 as it would then be a rectangle.



3.14-2 = 1.14


1.14/2 = .57 or 57% increase in area. I am assuming this would also be the increase in solar hitting the panel at 90* so also your net gain by doing 100% perfect tracking.



If correct, this is not "orders of magnitude" of increase.

[booster]

This might be better information, it is from here:


https://www.sciencedirect.com/topics...altitude-angle





This shows a comparison between east west tracking, north south tracking, and both at the same time. What it doesn't give is a comparison to horizontal panels, unfortunately.