So the guy who is going to install new panels for me has suggested the following
Replace the North string with 550W panels
Change the East facing string of 325W panels to West facing and augment it with the newly spare panels.
So my question is about orientation. He says that in his experience N&W is more productive than N&E. It seems to me that it’s 6 of one, half a dozen of the other. There have been days when the morning is cloudy and then I wish I had something facing W. But there are other days when the morning is bright and the afternoon is cloudy, but my battery is already charged and then the current arrangement is quite satisfactory.
He says my say is the final say, but he strongly recommends N&W over N&E, says in the long run it is more productive and this is what he always recommends to customers who can’t go all N.
I have higher mountains to the east than to the west, so sunrise is a little later than the symmetrical sunset on the other end.
It is also somewhat typical to have a little bit of cloud cover on the horizon in the mornings, but uncommon to have that in the afternoon. So I do get more out of panels on the west than I do to the east.
If I could only cover one direction, for me it would be west. But what I did, is I have my oldest panels and also the smallest array (6 x 150W) pointing east for that same reason.
Anyway, now we are getting something approximating sunny weather in Gauteng, I have a ladder propped up, and every 30 minutes or so I go and check the W facing roof for shade.
It’s a False Bay thing. The Hottent… you know, that mountain… is closer to the east than the nearest mountain to the west (Table mountain). If I lived closer to Table mountain, the panels would go east.
I’m the wrong side of 35 now, and routines get harder to change. We’re used to a world in which we get lots of PV before noon and the battery is charged by 11:30 (most days of the year). I don’t know if I want to work out a new routine.
It will be interesting to see how much spare capacity I have now. We may have more freedom now. Forgetting routines is something I can still manage.
All I can add is that in my limited experience of 7 years of owning my own system, you can never say that an afternoon will be better than the morning in terms of production.
In Gauteng, its the roll of the dice. Its never the same.
I would place the panels where the least shadows would be. Look at the surroundings.
If it’s “fixed” shading due to trees, buildings, mountains, etc it’s an easy decision. Clouds however not… but then go for Bifacial panels. They are giving great production in (somewhat) cloudy conditions and are now available at the same price as Mono panels. and N/E works best for me in Pretoria.
But how do I get sun on both sides of those except by standing them upright? The panels are going on rails on a roof pitched at 30 something degrees.
Interestingly the current E facing string is still producing useful power at 14:30 when the sun isn’t striking the panels at a small angle. The N string is already producing about 750W to 1.3kW from the E string at 8:40.
Really the orientations are ENE and NNW.
My inclination (pun!) is to stick with E (or ENE). The hill I’m on is lower to the E, I have more open space to the E, trees are further away to the E.
I think the argument is that sun that bounces off other surfaces also help with generation. On a roof, 150mm away from the tiles… probably not much use. On a ground mount, or at an angle on the roof, likely quite a bit more.
Some people also just fit them because they look nice.
If there’s no shade differences then look at your consumption patterns. For me, I would prefer them east so that batteries can charge after the night especially if there was a long outage. My geysers come on early in the day so once batteries are full and geysers are hot, anything else is just wasted.
Your additional power from the north string should be able to carry you into sunset if you haven’t had any issues thus far.
It’s also more important to consider winter as production is much lower on east / west. Compared to summer.
Mine are NW because they have to be. I prefer to have PV later and to go into the night with more from there. I can wait for PV in the morning before adding loads. Go to work, get supplies or use it as an excuse to lie in for a bit on weekends!
