Aiming Solar panels, Grog gets it wrong.

[Abe53]

Talking to Grog this morning:
in pretoria south africa what is the angle of the sun at 12:00
The angle of the sun (solar altitude angle) at 12:00 in Pretoria, South Africa, on June 7, 2025, is approximately 40.9° above the horizon. (Right so far...)
How many days in a year will the solar altitude angle in Pretoria, South Africa be below 45 deg?
The solar altitude angle at 12:00 PM SAST in Pretoria, South Africa, is below 45° on approximately 66 days of the year, specifically from January 1 to January 20 and from November 16 to December 31. (Obviously wrong!)
Background: I am mounting solar panels due North at 45 degrees up from horizontal, and wanted to check that compromises are reasonable.

 

[Sinbad]

Talking to Grog this morning:
in pretoria south africa what is the angle of the sun at 12:00
The angle of the sun (solar altitude angle) at 12:00 in Pretoria, South Africa, on June 7, 2025, is approximately 40.9° above the horizon. (Right so far...)
How many days in a year will the solar altitude angle in Pretoria, South Africa be below 45 deg?
The solar altitude angle at 12:00 PM SAST in Pretoria, South Africa, is below 45° on approximately 66 days of the year, specifically from January 1 to January 20 and from November 16 to December 31. (Obviously wrong!)
Background: I am mounting solar panels due North at 45 degrees up from horizontal, and wanted to check that compromises are reasonable.

As I remember it, you want your angle to be the same as your latitude.

 

[killerbyte]

Talking to Grog this morning:
in pretoria south africa what is the angle of the sun at 12:00
The angle of the sun (solar altitude angle) at 12:00 in Pretoria, South Africa, on June 7, 2025, is approximately 40.9° above the horizon. (Right so far...)
How many days in a year will the solar altitude angle in Pretoria, South Africa be below 45 deg?
The solar altitude angle at 12:00 PM SAST in Pretoria, South Africa, is below 45° on approximately 66 days of the year, specifically from January 1 to January 20 and from November 16 to December 31. (Obviously wrong!)
Background: I am mounting solar panels due North at 45 degrees up from horizontal, and wanted to check that compromises are reasonable.

Why were you talking to your alcohol?

 

[Left Of Bang]

An online tool that may help with your calculations:
PHOTOVOLTAIC GEOGRAPHICAL INFORMATION SYSTEM

Some screenshots:

 

[Snotface]

Talking to Grog this morning:
in pretoria south africa what is the angle of the sun at 12:00
The angle of the sun (solar altitude angle) at 12:00 in Pretoria, South Africa, on June 7, 2025, is approximately 40.9° above the horizon. (Right so far...)
How many days in a year will the solar altitude angle in Pretoria, South Africa be below 45 deg?
The solar altitude angle at 12:00 PM SAST in Pretoria, South Africa, is below 45° on approximately 66 days of the year, specifically from January 1 to January 20 and from November 16 to December 31. (Obviously wrong!)
Background: I am mounting solar panels due North at 45 degrees up from horizontal, and wanted to check that compromises are reasonable.

Just stick them on your roof and forget about them. Unless they are way off, those couple of extra degrees aren't worth the effort.
Convert your work effort into Rand/hour and just buy a couple of extra panels with that saved money.

 

[Benedict A55h0le not]

You are overthinking it. The angle matters less in summer, so set it up to be optimal for winter. Summer has more sunlight hours, so will produce more energy in summer even with panels angled perfectly for the winter sun.

 

[killerbyte]

You are overthinking it. The angle matters less in summer, so set it up to be optimal for winter. Summer has more sunlight hours, so will produce more energy in summer even with panels angled perfectly for the winter sun.

And frankly I have seen systems that are overkill for the houses they are in get the batteries full by 12pm on a summers day. So the angle is not something to worry about for summer.

 

[BBSA]

In Pretoria, summer often brings cloudy and stormy weather, so it’s important to maximise solar gain when the sun shines. Setting your solar panels at an angle equal to your latitude (about 25° for Pretoria) offers a good year-round compromise between summer and winter performance.

 

[Benedict A55h0le not]

And frankly I have seen systems that are overkill for the houses they are in get the batteries full by 12pm on a summers day. So the angle is not something to worry about for summer.

Yep, it is common for systems to be panel "heavy" and "light" on batteries. I also bought a system with 8 large panels and only a 5kw battery. The battery was full in about 2 hours on a sunny day. It would have been better to have half the panels and double the battery. The extra panels is handy to have though on cloudy days.

 

[killerbyte]

Yep, it is common for systems to be panel "heavy" and "light" on batteries. I also bought a system with 8 large panels and only a 5kw battery. The battery was full in about 2 hours on a sunny day. It would have been better to have half the panels and double the battery. The extra panels is handy to have though on cloudy days.

The smaller of the two system I know has 12x 500W panels and a 10kWh battery.
The other system has 24x 500W panels and 4x 10kWh batteries. So these aren't really light on batteries, especially not the second one.
But I agree with you, and I feel that if you find you have extra solar capacity then throwing in another battery is always a good idea. Capture as much sunlight as you can to fuel your usage at night... **** Eskom.

 

[SHL]

Talking to Grog this morning:
in pretoria south africa what is the angle of the sun at 12:00
The angle of the sun (solar altitude angle) at 12:00 in Pretoria, South Africa, on June 7, 2025, is approximately 40.9° above the horizon. (Right so far...)
How many days in a year will the solar altitude angle in Pretoria, South Africa be below 45 deg?
The solar altitude angle at 12:00 PM SAST in Pretoria, South Africa, is below 45° on approximately 66 days of the year, specifically from January 1 to January 20 and from November 16 to December 31. (Obviously wrong!)
Background: I am mounting solar panels due North at 45 degrees up from horizontal, and wanted to check that compromises are reasonable.

WTF is Grog??? Is he from the multiverse?

 

[Sinbad]

Yep, it is common for systems to be panel "heavy" and "light" on batteries. I also bought a system with 8 large panels and only a 5kw battery. The battery was full in about 2 hours on a sunny day. It would have been better to have half the panels and double the battery. The extra panels is handy to have though on cloudy days.

That's definitely the way here in the UK, especially as panel prices drop. Houses have waay more panels than they would need on a sunny day, so that on cloudy days a decent portion of the daily usage is still covered.
Difference here being you can generally export to the grid for sane money, so you don't "throw power away" like you would do if your batteries were full in SA.

 

[killerbyte]

That's definitely the way here in the UK, especially as panel prices drop. Houses have waay more panels than they would need on a sunny day, so that on cloudy days a decent portion of the daily usage is still covered.
Difference here being you can generally export to the grid for sane money, so you don't "throw power away" like you would do if your batteries were full in SA.

The problem here is that you'd need a truckload of batteries to power the heating in winter. But when I get a house I do want to throw on panels and buy batteries overtime just to reduce the electric bill.

 

[Sinbad]

The problem here is that you'd need a truckload of batteries to power the heating in winter. But when I get a house I do want to throw on panels and buy batteries overtime just to reduce the electric bill.

I wouldn't even try to run heating off solar here

Gas ftw. **** greta.

 

[Benedict A55h0le not]

That's definitely the way here in the UK, especially as panel prices drop. Houses have waay more panels than they would need on a sunny day, so that on cloudy days a decent portion of the daily usage is still covered.
Difference here being you can generally export to the grid for sane money, so you don't "throw power away" like you would do if your batteries were full in SA.

You will definitely need more panels on Mud Island than SA, and relatively less batteries. Mud Island has much less sun, but also has a more stable supply from the state grid.

Yes, SA is an extreme socialist state. The state, including the DA, is against private energy empowerment, even in an energy shortage crises. This is why you get paid sane money for your feed-in, you live in a less socialist state that works with it citizens rather than against them.

 

[killerbyte]

I wouldn't even try to run heating off solar here

Gas ftw. **** greta.

My new place has duel fuel and the cost of gas is just so cheap that I do not understand why people cut off their gas.

 

[Abe53]

You are overthinking it. The angle matters less in summer, so set it up to be optimal for winter. Summer has more sunlight hours, so will produce more energy in summer even with panels angled perfectly for the winter sun.

Thanks, Benedict, my thoughts exactly, going 45 deg angle for winter sun. Also, we get hailstorms and steeply angled panels should survive better.
Now off to https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html (Thanks to Left of Bang for link!)

 

[Snotface]

And frankly I have seen systems that are overkill for the houses they are in get the batteries full by 12pm on a summers day. So the angle is not something to worry about for summer.

I've got one of those systems, but i got a deal i couldn't say no to, so i went all in. I see it as preparing for the future. I've just had a borehole put in, so my water supply will be reliant on my electricity supply; not something to mess around with. Next big project will be more batteries.

 

[killerbyte]

I've got one of those systems, but i got a deal i couldn't say no to, so i went all in. I see it as preparing for the future. I've just had a borehole put in, so my water supply will be reliant on my electricity supply; not something to mess around with. Next big project will be more batteries.

Do you have an above ground tank? What pump are you using to feed into the house? If you don't already have one then highly recommend you look at getting a VFD/VSD pump. A family member has a borehole and a 1.1Kw VSD pump, we have watched the power draw of that pump and it slowly creeps up and rarely runs at 100%, which means its not pulling massive power from the inverter.

 

[Snotface]

Do you have an above ground tank? What pump are you using to feed into the house? If you don't already have one then highly recommend you look at getting a VFD/VSD pump. A family member has a borehole and a 1.1Kw VSD pump, we have watched the power draw of that pump and it slowly creeps up and rarely runs at 100%, which means its not pulling massive power from the inverter.

No tanks yet, still just attached to an arb tap they installed in my garden so that i could run it for a bit to get the gunk out of the well.
Not sure of the make of the pump down the hole, but i'll be using different pumps to pump it out of the tanks into the house and garden.