Seasonal tilt adjustment of solar panels

[Bob Blarney]

For those who use portable solar panels, this discussion of seasonal tilt angles might be of interest to you to get the most energy from your panels.

https://www.solarpaneltilt.com/

Oh, I just had an idea that is interesting, but probably wouldn't work out in practice. How about repurposing the elevation mechanism of the Winegard VHF/UHF television antenna to optimize the solar panel orientation? I'm doubtful that it could withstand much wind force, and so it would necessary to lower it during windy weather, but then again the same must be considered for the awnings.

[Tomzstream]

If you don't want to bother changing tilt angles, and will be parked in the same locale most of the year, a good rule of thumb is to tilt the panels at the same angle as the value of your latitude. I have 7.8kW worth of panels on a South Facing roof of my house which coincidentally matches my latitude of 30 degrees. On the Equinoxes, the Sun elevation at Solar Noon is 60 degrees which puts it perpendicular to the panel surface. During the Summer its elevation is much higher and in the winter much lower. But for optimal capture, match the angle of your latitude. Granted, this is for fixed panels facing South. The optimal arrangement would be a tracking system that always faces the Sun.

I would not set an Airstream panel angle up this way simply because of air resistance, but for portable panels, it's a good technique. Any good astronomy site can give you the altitude of the sun at your location at Solar Noon for a particular date. I really like this site too. https://www.esrl.noaa.gov/gmd/grad/solcalc/

[Bob Blarney]

Originally Posted by Tomzstream

. Any good astronomy site can give you the altitude of the sun at your location at Solar Noon for a particular date. I really like this site too. https://www.esrl.noaa.gov/gmd/grad/solcalc/

Yes, I've used this site too, to set up sundials. As a matter of fact, I've imagined adapting the analemma from analemnatic sundials to adjust panel orientation. Somewhere in my back pages, I have a spreadsheet that calculates and displays such a sundial for any specific location. One well-known analemnatic sundial is located at Longwood Gardens in Kennett Square PA, which would be nice travel destination.

[uncle_bob]

Hi

You very much do *not* want to try this with something as lightweight as the antenna arm gizmo. A solar panel has a lot of weight and a lot of "sail area". You will rip it right off the top of the trailer pretty quickly.

Any "tilt" device on a roof mount RV solar needs to have a way of latching down when in motion. That semi in the other lane on a 2 lane road is pushing a lot of air in front of it. If you both are going 60 MHP, your roof likely is getting hit with 120 MHP gusts.

Adequately designed tilt gizmos add weight. Pretty much the last place you want to put weight on an RV is on the roof. Stability wise, it's a bad thing. Weight on the roof and right at the rear is a very bad thing .....

Lots of issues ...

Bob

[Bob Blarney]

Originally Posted by uncle_bob

Hi

You very much do *not* want to try this with something as lightweight as the antenna arm gizmo. A solar panel has a lot of weight and a lot of "sail area". You will rip it right off the top of the trailer pretty quickly.

Any "tilt" device on a roof mount RV solar needs to have a way of latching down when in motion. That semi in the other lane on a 2 lane road is pushing a lot of air in front of it. If you both are going 60 MHP, your roof likely is getting hit with 120 MHP gusts.

Adequately designed tilt gizmos add weight. Pretty much the last place you want to put weight on an RV is on the roof. Stability wise, it's a bad thing. Weight on the roof and right at the rear is a very bad thing .....

Lots of issues ...

Bob

As I said, it would not likely be practical. It was just 'blue sky' thinking, but that's how innovation eventually occurs.

It would never do for a trailer underway, but for an AS that was set up as a (semi-) permanent installation it might work. But then again it would be easier to set up a ground or pole installation.

[uncle_bob]

Originally Posted by Bob Blarney

As I said, it would not likely be practical. It was just 'blue sky' thinking, but that's how innovation eventually occurs.

It would never do for a trailer underway, but for an AS that was set up as a (semi-) permanent installation it might work. But then again it would be easier to set up a ground or pole installation.

Hi

If the trailer needs to move down the road safely, that puts constraints on what you can add to it. If semipermanent means the trailer never moves then that's different.

There are already manual tilt setups available for trailers and some have them. The typical response after a while is - "I don't bother with it anymore, to much hassle for to little gain".

Bob

[Bob Blarney]

Originally Posted by uncle_bob

Hi

If the trailer needs to move down the road safely, that puts constraints on what you can add to it. If semipermanent means the trailer never moves then that's different.

There are already manual tilt setups available for trailers and some have them. The typical response after a while is - "I don't bother with it anymore, to much hassle for to little gain".

Bob

The improvement in efficiency is about 4-5%. I waded through a technical engineering paper that states that a maximal seasonal deviation of +/-24d from the equatorial plane at the solstices will improve efficiency from ~71% to 75%, with 100% obtained by using an active tracking mechanism on the mount. So yes, most people probably won't bother.

[dznf0g]

I fashioned 3 sets of rods for each (2-100watt) panels for my latitude. I use them primarily for when the AS is at home between trips. Each set is set up for the chart angles...1 set for summer, one set for spring and fall, and one set for winter. I have the AM solar feet with the screw handle mounts.

I had to use some geometry to calculate the proper length, due to the AS curved roof.

[DaveP]

Great information. Thanks for posting it!