Optimal year round panel angle?

garynappi · September 2019

I went to:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Then today I marked my south facing articulated panel mount with the summer (79 deg.), winter (49 deg.), and optimal year round (64 degree) performance angles. Thanks to my Dad for that weird shop protractor I never thought I'd use it was a snap. With my 100 watt panel on a vertical wall above the first floor I wondered what kind of losses I might expect if I just left it at one setting year round?

Being that the panel(s) are difficult to easily / safely get to, if losses are minimal I might consider either leaving them at the "optimal" or even something in between it and the "winter" settings.

I'd think I would rather add another fixed panel to make up for losses if they were more than minimal to avoid changing the angle 2x per year.

Oh, my system is only for outside mood / security lighting and bird bath type 12 volt circulation pumps on a 95Ah battery. I figure 30 watts continuous draw overnight.

I looked for info on the web regarding sun / angle losses and found only cryptic "without great yield losses" Any thoughts?

BB. · September 2019

You need to be real sure of your energy usage... Say

12 hours overnight x 30 Watts = 360 Watt*hours

12 hours daytime * 20 Watt pump = 240 WH

Total = 600 WH per day (guessing/example)

You 100 Watt panel on a good average summer day would produce roughly

100 Watts * 0.61 DC system eff * 5.0 hours of sun per day = 305 WH per day.

And in winter, 1/2 that amount (roughly).

Bill

Estragon · September 2019

I leave mine at winter angle all year (~25° from vertical), as even at that angle they produce enough in spring/summer. In fall/winter they don't.

Horsefly · September 2019

Although I chose a simple fixed angle, this site proves some pretty complete and compelling data on the subject:

http://www.solarpaneltilt.com/

I haven't examined all his conclusions for accurate math, but it seems pretty good.

jonr · September 2019

I use https://pvwatts.nrel.gov/pvwatts.php

garynappi · September 2019

Thx Bill, my 30 watts is including the little fountain pump, my lighting fixtures are all 1 watt LED lamps. The daytime usage of the little pump is only 5w bringing me to ~420 WH which still looks a bit high for my setup.

So, I looked at linear actuators which I can easily implement due to the way I re-designed the panel holder but...

Every actuator I looked at is two wire. I suspect the motor goes into reverse automatically after a stop in one direction caused by an operator using the switch or a limit switch is used for up and down.

In order to have complete control up and down to change the angle dynamically and at a non specific degree of tilt I would imagine that a three wire motor would be a necessity? Or is a two wire the only option with having to hunt up/down? I prefer not to complicate the issue with a limit switch scheme.

Optimal year round panel angle?

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