Finding True North for Solar Panel Placement: A Simple Method

[DaveC426913]

Yes, but the OP mentioned only the panels - no system restrictions were described.

It behooves us to point out that this may not be the only factor to consider when configuring his panels.
It is entirely up to him to decide whether it applies to his system, but we would be doing him a disservice to omit mentioning such a salient factor.

But I agree with your terminology - the better term is optimization.

 

[DaveC426913]

Relative to the OP, I think this post is key. Unless you are really far north (and likely not using solar panels!), the delta between True North and Magnetic North is probably a very tiny effect on total power out.

It's generally on the order of 10 degrees. Roughly, the COS of that is 0.97.
If the OP didn't care about that 3%, he probably wouldn't be going to the lengths he is - both researching the calcs himself and bringing it to PF for verification.

 

[OmCheeto]

Apart from the good advice note that the sun input to your panels is a cosine funktion of the angle and not super critical to get very accurate.

Important is that you clean the panels , more frequently if there is a lot of dust in the air , and you should run a test now and then to determine that the efficiency still is OK. It will deteriorate with time and hopefully you have a guarantee that set the max amount.
Good luck with the project.

Good points! I did the maths on PV output vs misalignment a couple of years ago. [ref]

misalignment   percent
angle °        of rated
               output
30               86.6%
25               90.6%
20               94.0%
15               96.6%
10               98.5%
5                99.6%
0               100.0%

 

[NTL2009]

It behooves us to point out that this may not be the only factor to consider when configuring his panels.
It is entirely up to him to decide whether it applies to his system, but we would be doing him a disservice to omit mentioning such a salient factor.

But I agree with your terminology - the better term is optimization.

I agree that it it is worth bringing up as a question to the OP, and hopefully they will respond. I disagree with any broad-brush statements that the output needs to be matched to demand - that is system dependent and goal dependent (maximize total output or maximize output at certain times of the day).

It's generally on the order of 10 degrees. Roughly, the COS of that is 0.97.
If the OP didn't care about that 3%, he probably wouldn't be going to the lengths he is - both researching the calcs himself and bringing it to PF for verification.

But that is totally dependent upon location (which I don't think the OP provided). This link: https://upload.wikimedia.org/wikipedia/commons/2/28/Mv-world.jpg

shows a line of "No Variation" roughly from Duluth, MN to New Orleans, LA, and down through part of Central and South America. Another one does a wild curve through Europe, Africa, swooping up through India and beyond.

 

[NTL2009]

Just as another possibly interesting side note - I was reading about someone who had a little off-grid cabin in the woods that he'd visit on some weekends. He had his solar panels arranged in an extremely inefficient manner, but it was an effective way to achieve his goals.

They were near vertical, pointing straight East and straight West. He had some small trickle draw that he wanted to keep active while away. His panels provided far more peak power than he needed for this trickle draw, so this arrangement provided that power from sunrise to sunset. That minimized the draw down (and recharging cycles) on his battery storage. I think that he had them set up, so when he was there, he could easily tilt them out flat later in the day, and have more power available for his needs mid-day, or recharge the batteries from draw down from the previous evening.

The other advantage for him was that a near vertical panel will shed snow. I've seen the panels here in Northern IL have their output drop to near zero for weeks at a time. Panels here are mounted about 20° from horizontal to maximize the annual production (longer summer days), and that leads to the snow clinging to them. So for him, it was more about convenience than getting the most kW-hr out of a panel. Over-sizing the panels was a cheap price to pay for convenience.

 

[Baluncore]

Three other ways.
1. Mark your exact location on a map. Look for a distant visible feature that is also marked on the map. Draw a line on the map between the two. Rotate the map so the line points at the distant feature. The map is then correctly orientated, so the map grid will be N–S at your location.

2. Use a GPS to read Lat–Long on site and somewhere that can be seen from site. Travel back and forth to check the readings are reliable. The bearing of the line between the two sites can be found from the equations for a great circle passing through those two points.

3. If you read GPS Longitude, then find a place North or South with exactly the same longitude, the line between the two will be true North–South. The further apart the points, and the more times you check the numbers, the more accurate the N–S line.

 

[Tom.G]

If you want perfection near the solstice, you can get a good west-east line by marking the shadow any time before noon, marking intervals as you observe the shadow get shorter, and then stop marking when the shadow is the same length as the original mark. The shadow traces a hyperbolic path with the apex pointing at your stick, so you just go for symmetry of the hyperbola to get your west-east line.

That's almost the simplest way. As @Anachronist stated, the apex of the hyperbola will point at the stick at local Noon. This is the same as saying that the shadow will be shortest at Noon. The shortest shadow of stick is your North-South line, and it occurs at local Noon. No need to spend the time creating the other half of the hyperbola.