I'm working on a pole mount for my portable panels so that when the trailer is in direct sun, or getting the panels 10' or so in the air gets good sun I can put them on the pole instead of on the ground.What I have are two 80 watt panels.The easiest mount would be to have the panels fixed and oriented perpendicular to the ground rather than at an adjustable angle. I know my panels do see higher current out at a 45-60 degree angle instead of flat on the ground, especially in the fall. Most of the time we will be 45 latitude or higher, so I think the ideal angle is near 60 degrees.Anyone have any experience or info on how much difference in panel output I can expect between optimum and 90 degrees?if it isn't much I'll likely not go through the effort to make adjustable angle mount. With the mount scheme I have in mind it will be easy to rotate the panel to keep it facing the sun during the day when we are around the trailer.

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.

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.

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.

For noon (1300 fast time) at 46N you know Dec is 23 on 21 June and Zero on 21 Sep.21 June Noon Tilt is 46-23 = 2321 Sep Noon Tilt is 46-0 = 46change is about 8 degrees a month.Roughly, Jun and July are the same, May and Aug the same, Apr and Sep the sameI get the right tilt for noon, getting panel Isc for amps then tip it up till I see amps drop so that tells me how much higher I can go and still get Isc at noon. After that, you have to pick something that you like.

If you build it same as,.....or find an old "C Band" Sat dish mount that tracks the arc of the sattellites, has "skew" built into it, it will track the sun's arc perfectly. That's the way I built mine.

solar panel output vs. tilt angle | Good Sam Community

13 Replies

ktmrfs
Explorer II
Oct 13, 2013
Thanks for all the responses, hints, data and links. Looks like I have some research to do. Definitely want to be able to have some range of variable tilt on the panels.
ktmrfs
Explorer II
Oct 13, 2013
Almot wrote:
PV Watts is a good site.

This one is good too. If you need a semi-annual tilt, i.e. one for winter and another one, flatter, for summer, it will give you the numbers for your latitude.

For simplicity - and considering mentioned above dangers of climbing up and down too often - you can just have a winter angle, lay it flat for summer which will also be a "travel" position.

it will be easy to adjust before I put it up. The plan is to have a pipe with the panels attached that I just lift and drop into a 2' long tube attached to the trailer A frame tongue. The scheme I have will allow me to attach the panels to the pipe and set the angle while it is basically on the ground. Once installed, I'll be able to rotate it during the day if we are around. otherwise just have it pointed south.

Similar scheme to what I do now for mounting my external cell phone antenna that goes to my cell phone 3W amp inside the trailer for use when we don't have good cell reception.

When traveling the panels are stored inside the trailer.

if we don't have sun near the trailer, well, I have up to 100' of #8 extension cords to get the panels in the sun. Which worked real well this last september.

Probably half the time we camp, trailer is very shaded, so only solar is to use portable panels in the sun, which can be a ways away.

The other half the time, trailer is in decent sun, or at least the trailer roof is in sun most of the day, so if the panels could be 5-10 ft in the air I'd be all set.

but I really don't want panels sitting on the roof. To easy to have the panels damage the EPDM roof, plus the hassle of putting them up there temporarily.

so that's why the "panel on a pole" approach.
Almot
Explorer III
Oct 13, 2013
PV Watts is a good site.

This one is good too. If you need a semi-annual tilt, i.e. one for winter and another one, flatter, for summer, it will give you the numbers for your latitude. It will also tell you when to switch from "winter" to "summer" angle. Then you won't have to think every time.
Z-Peller
Explorer
Oct 13, 2013
For what it's worth, the "clinometer" app for an iPhone does a fine job of finding the angle of the dangle........cheap and easy way to go if you have a smart phone.....just sayin....
BFL13
Explorer II
Oct 13, 2013
The real problem is measuring the angle of the dangle, where you have no level base. You need a gravity based indicator you can set on the panel face. This is the sort of thing I think. I have something like it attached to a square (I see they call them Empire squares but only have a bubble in those. Mine has a great big circular gravity based pointer thingy like this sort of.

http://www.homedepot.ca/product/magnetic-protractor-angle-locator/967209
Wayne_Dohnal
Explorer
Oct 13, 2013
This is my favorite solar calculator:

PV Watts

You can plug in the location, tilt, and azimuth and get month-by-month production results. The production is based on "average" weather conditions for the chosen location. The site tries to steer you to a newer version which I find more difficult to use, so I stick with the old one.
ktmrfs
Explorer II
Oct 13, 2013
I found a declination calculator. Guess I'll plug in some numbers for months I camp and make a "cheat sheet"

declination calculator
ktmrfs
Explorer II
Oct 13, 2013
RJsfishin wrote:
If you build it same as,.....or find an old "C Band" Sat dish mount that tracks the arc of the sattellites, has "skew" built into it, it will track the sun's arc perfectly. That's the way I built mine.

Now you got the "nerd" in me fired up!!
RJsfishin
Explorer
Oct 13, 2013
If you build it same as,.....or find an old "C Band" Sat dish mount that tracks the arc of the sattellites, has "skew" built into it, it will track the sun's arc perfectly. That's the way I built mine.
BFL13
Explorer II
Oct 13, 2013
For noon (1300 fast time) at 46N you know Dec is 23 on 21 June and Zero on 21 Sep.

21 June Noon Tilt is 46-23 = 23
21 Sep Noon Tilt is 46-0 = 46

change is about 8 degrees a month.

Roughly, Jun and July are the same, May and Aug the same, Apr and Sep the same

I get the right tilt for noon, getting panel Isc for amps then tip it up till I see amps drop so that tells me how much higher I can go and still get Isc at noon. After that, you have to pick something that you like.

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solar panel output vs. tilt angle

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