solar panel output vs. tilt angle

BFL13 wrote:
I have some experience with this. The situation is that at noon there is a proper tilt angle for the panel facing South that you can calculate when you know the sun's declination and your latitude.

That tilt angle changes by about 46 degrees over six months, so the average change is 8 degrees a month, but it is not linear month to month.

Meanwhile, the sun is lower the rest of the day, so the panel needs to be tilted higher when pointing at the sun earlier and later than noon. So the compromise for a fixed tilt on a rotating contraption is higher than for noon but not forgetting that most of the daily AH haul is mid-morning to mid afternoon so you shouldn't have it way up for best early morning late afternoon angle. Something more but not a lot higher tilt than for noon is the best compromise.

So that still leaves the problem of when in the year is this for? All year or just the summer or when? You need to find a compromise proper tilt for noon in that period of use, so you can then pick a tilt higher than that.

Note---for a fixed tilt South, non rotating panel, it is the opposite situation. You want the tilt less than for noon so it can catch light better earlier and later. Macslab has some numbers for that.

I didn't work too hard to find a best tilt angle for the period mid April to mid September for 49.2N but where the best angle for noon was 40 I would make the tilt no more than 50. You get about 10 degrees of play before you lose amps much so that did pretty well.

I found changing the swivel aim three times a day was sufficient, SE S , and SW (putting it back to SE at sunset) If you did have an adjustable tilt to go with the swivel you would have two positions. One lower at S and one higher for SE and SW.

BFL. THANKS!!

Since I'm most often camping between 45 and 47 latitude, and similar to you in that common camping is April through october, sounds like I should plan either an adjustable mount for angle or set it around between 40 and 50 degrees, rather than vertical at 90 degrees. Have to think more about how to mount the panels to the pole in a way that is reasonably easy to mount/remove and store the bits and pieces when I just have the panels tilted on the ground.

Flat or 0 degrees is OK to recharge the batteries without getting on the roof, and doing possible damage to it. By tilting to about 35 degrees in the winter, you will enhance the solar gain.

However in the middle of summer, the tilt will not help as much. What is suggested is lattitude +10 degrees in the winter and lattitude - 10 degrees in the summer, due to it's higher angle in the sky. So flatter is better in the summer than in the winter.

I would rather recommend another 100 - 150 watt solar panel, then fix all of them to the roof full time, than to recommend something you need to fiddle with each time you set up or break camp. It is most likely that you will leave the flat mount panels on the roof all the time, than the portable ones will see any sunlight while being towed.

Even while towing, you will get amperage from the solar panels (once mounted to the roof). I ran the wiring down the back of the refrigerator, and made mounts from 6" length of 2" angle aluminum from Home Depot, with 1 hole 5/16" on the panel side and 3 each 3/16" holes on the other side into the roof with rubber roof sealant and 3 #10 screws.

The solar controller was in my closet, and wiring then went to the battery. I ran #10 UV rated wire (gray stuff from Home Depot) to the panels and the controller. You can run about 175 watts to the controller with each wire run. While the wire is rated at 30 amps, if you run more than about 10 amps, voltage loss becomes excessive.

Fred.

I have some experience with this. The situation is that at noon there is a proper tilt angle for the panel facing South that you can calculate when you know the sun's declination and your latitude.

That tilt angle changes by about 46 degrees over six months, so the average change is 8 degrees a month, but it is not linear month to month.

Meanwhile, the sun is lower the rest of the day, so the panel needs to be tilted higher when pointing at the sun earlier and later than noon. So the compromise for a fixed tilt on a rotating contraption is higher than for noon but not forgetting that most of the daily AH haul is mid-morning to mid afternoon so you shouldn't have it way up for best early morning late afternoon angle. Something more but not a lot higher tilt than for noon is the best compromise.

So that still leaves the problem of when in the year is this for? All year or just the summer or when? You need to find a compromise proper tilt for noon in that period of use, so you can then pick a tilt higher than that.

Note---for a fixed tilt South, non rotating panel, it is the opposite situation. You want the tilt less than for noon so it can catch light better earlier and later. Macslab has some numbers for that.

I didn't work too hard to find a best tilt angle for the period mid April to mid September for 49.2N but where the best angle for noon was 40 I would make the tilt no more than 50. You get about 10 degrees of play before you lose amps much so that did pretty well.

I found changing the swivel aim three times a day was sufficient, SE S , and SW (putting it back to SE at sunset) If you did have an adjustable tilt to go with the swivel you would have two positions. One lower at S and one higher for SE and SW.