Good info. It may be misleading a bit where it uses "solar radiation" but does not give a value for that as it changes all day. IE if you get "5 hours" that does not mean you get the same amps all during that five hour period. I was measuring actual amps to the battery bank (with Trimetric)
In this guide, which has that info as a reference link,
he says to not use the theoretical optimum tilt for noon all day, but lower it some to capture the light in the shoulder hours. He does not say to lower it to flat.
See his example near the end under "Why does this work?" where instead of tilting at noon's 16.5 degrees he says to use 12.5 degrees.
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I am still puzzled by that study that shows the same or slightly better "solar radiation" for flat compared with tilted in June and July.
They have figures like in June, av 5.6 hrs (4.6 min/6.6max) vs 5.5 (4.4/6.5) tilted. But the panel is getting useful amps from 7am to 7pm with high noon at 1pm, during this time. That's 12 hours not 6.
Their 6 hr time is only three hours each side of high noon. Are they comparing flat vs tilted only in that time frame? The sun is quite high then, so the penalty for being flat is less.
During the hours from 7-10am and 4-7pm, the sun is lower but off to the side more. Flat is better (but how much better?) for catching the light off to the side, but tilted is better (but how much better compared with sideways better?) for the sun being lower.
I do not have a full day's comparative AH haul for each case of flat vs tilted for fixed South. I only have flat vs tilted for a panel pointing at the sun during shoulder hours. At that time the panel needs to be tilted quite high up since the sun is lower then.
For flat to be better than tilted in shoulder hours with the panel pointing South, the advantage of getting sideways light must be greater than the advantage of being tilted up for the lower sun.
It all calls for some testing, which I can do with my set-up if we ever get more than one nice day in a row this year. Seeing is then believing. These various solar charts and guides are too confusing.
The thickness of the atmosphere is "at play". At noon on the equinox at the equator there is say a 100 mile thickness. At six pm the sun's rays have to go through a much thicker "layer". That absorbs photons and reduces the energy content, tilt or no tilt.
What "aiming" does is reduce the reflection off the surface of the panel.
Yes, that shows in the tracking curve I posted above, where amps fall off earlier and later in the day even though the panel is aimed. You just can't get max amps when the sun gets below a certain altitude.
However, I don't see where that fits in with the flat vs tilted with a fixed panel pointing South.
Thanks for pickin' up the slack for me, mene-dog. Guess I had a little too much Cinco de Mayo last night to open the laptop.
Since my rig is a small MH... and we usually pull a boat as our toad, the MH becomes our run-around-town rig. This would not be practical for me. And yes... since solar has recently become so affordable, aiming for RV systems is no longer as attractive an idea as it once was. And since I'm a small business owner who's already buried, I could make a lot more money than the cost of an extra panel in the time it would take me to build one of these. And an extra panel gets me 100% more power vs. 30.
BUT...
B is retired. And a bad day tinkering in the garage is better than a good day at work. It's cool that he does this kind of stuff in the same of SCIENCE!!!
Good work, B! We look forward to your reports.
Cheers,
Kendall
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Our Camper (with no payments)
I think the problem with these solar websites and the "hours " posting
is they are giving the number of peak hours during the day, Or the equivalent avg total hrs per day
when looking at these solar calculators they give number hrs for peak output, peak angle ,best avg angle, avg hrs per day for the whole yr and are for a fixed stationary mounting
so you might have 300watts of panels, you look up your location and the guide says 5.6 hrs
they mean you will avg 5.6 hrs of output per day over the course of the year
that's 1680 watts theoritical avg but then you have to find the solar radition percent index for you location and multiply that times the 1680 to get a truer number of you daily avg
to get numbers for a specific day or time of year you need to look at one of the charts that shows sun angles for that day
example yesterday
505 watts of solar clear sunny and breezy 13+ hrs from sunrise to sunset
2310.0 watt hrs 169.56 AmpHrs
using straight uncomplicated math that's just over FOUR solar hrs of output
peak amps 21.71, peak watts 290.4
by the time solar noon arrived (just after 1pm) the batteries had taken enough charge that they could not /would not absorb 25 amps peak out put of the controller
my batteries and use needs were less than the peak available
by 5 pm charge rate was 10 amps, which will just keep up with the fridge and fans, turning on the TV puts me at a deficit, more drain than production, tiling the panels would reduce that loss but too many panels and we move too much
Grid Tie with a steady constant drain offers a different set of total output
theoreticaly the power gtid can accept everything that your panels produce that is not being used at home, so a grid tie system would produce Max available all day, yes it will vary by sun angle and weather but not be affected by battery resistanceand charge use patterns
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Had a window with some sun in the clear of trees to run a quick flat vs tilted back-yard test of fixed panel pointing South.
Time 0930, three and a half hours before high noon at 1300ish, so at 15 degrees an hour sun was bearing approx SE by E
Used Trimetric and with a load on batteries, panel out on ground in driveway full sun , no shade, on extra long wire lash-up so some voltage loss, but got some amps to make the comparisons ok.
Panel Pointing South:
Flat on ground-- 2.9a
Tilted up some-- 4.2a
up some more---- 4.6a
Note graph posted earlier above, showing amps at 0930 at 5a so that is consistent. (probably tilt was a little higher then and less voltage drop on the "real" wiring)
This shows that optimum amps in shoulder hours is achieved by some tilting up, as "my guy" says in the above link.
So I have no idea what those other people are talking about with their flat is better than tilted in summer stuff.
in the early hours at lower latitudes the flat will pick up morning and evening tradition that a ilted panel will miss
remember you are talking tiling and tracking for a seasonal site
Vs fixed mount tiliting for year round use
anytime you include "tracking" you can optimise the sun angle all day any day or any time of the yeat
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