Hi Guys, 

I am sure was asked before, but searches weren't very successful,  probably because million keywords around the same topic. 

Could you please post your solar production graphs my month. I live in Johannesburg and is trying to predict my production how much my solar system would produce during the autumn and winter months. 

Thanks 

Theo

@TheoVogel My system it's only 3 months old, I've only stored +_ 2 months of info, I live about 60 Km south of JHB ( Vaal Triangle ) 

My daily average house consumption is about 24 KW/h 

My system comprises of the following

2 X 5 KW Growatt inverters

12 X 410 KW solar panels 2 stings ( 6 in series ) per string connected to each inverter.

1 X 5.1 KW/H LBSA 

Here is my data, hope it helps you.

 

The professional guys use fancy software to model typical yields.  Below are the modelling results for my house in Pretoria East - my final installation was somewhat different but it does give a good indication of seasonal yields. This is a free tool which doe sthe same without the monthly split.  It is pretty good, but assumes, like the pro software, there is no clipping ...  https://pvwatts.nrel.gov/

 

 

Edited December 4, 20214 yr by Scubadude

Thanks for all the insights. 

It looks like solar production in Gauteng is pretty flat throughout the year. 

I was expecting a bigger dip in winter. Good news though! 

On 2021/12/04 at 4:18 PM, TheoVogel said:

Thanks for all the insights. 

It looks like solar production in Gauteng is pretty flat throughout the year. 

I was expecting a bigger dip in winter. Good news though! 

I've only been on Solar for 4 weeks, the main issue is that excess "solar production" is "discarded" so it's quite difficult to measure.

There are only a few situations "solar production" can be measured:

1. You grid-tied and feeding into the grid every single kWh
2. Your own consumption exceeds the kWp of the solar PV

Both of these are unlikely in CoJ since (1) is discouraged by CityPower and (2) most people oversize the PV.

In my case the graphs on a sunny summer day look like this, after midday, the battery is full, the geyser is hot and there is nothing in my house to use the excess solar, so "solar production" drops.

In summer my battery is full by 11:30-12:30, I expect in winter to be full by 13:30-14:30
Still the same "total solar production", just over a longer period.

Would be interested to see "solar production" data from someone that feeds the grid.
 

 

Edited December 11, 20214 yr by system32

When a system is designed not to export, not to have excess PV. Draw some power from the grid every day one can achive the following in Gauteng. Yes June or July will produce the lowest PV but due to clear skies in winter the PV is not much lower than heavy cloudy months in summer. My system is in place for just under 3 years. Load can be controller via timers during the sun periods. 

List from Oct 2020 listing the efficiency of the system in kWh/kW of solar panels installed.

 

 

Edited January 4, 20224 yr by Scorp007

Great answer, than you for sharing 

kWh's generated by month here (in the Orange River Valley)...

worst month June with 640.3kWh, best month November with 921.9kWh.

I suppose I had better add that the PV panels are either 280 or 290W, not 100%  certain, now and there are 9 on the 1st MPPT and 8 on the second MPPT on a Sunsynk 5kW inverter.

Edited January 5, 20224 yr by Kalahari Meerkat
incomplete

@TheoVogel
Try pvoutput
https://pvoutput.org/listmap.jsp?sid=87830
You can search for PV in your area.

1 hour ago, system32 said:

@TheoVogel
Try pvoutput
https://pvoutput.org/listmap.jsp?sid=87830
You can search for PV in your area.

Wow, this tool is such a big security risk for targeted robberies! It shows exact location to everyone to see!

2 hours ago, system32 said:

@TheoVogel
Try pvoutput
https://pvoutput.org/listmap.jsp?sid=87830
You can search for PV in your area.

I would be interested to join. How do you interface your data?

2 hours ago, PowerUser said:

Wow, this tool is such a big security risk for targeted robberies! It shows exact location to everyone to see!

How do you conclude that it's a risk for targeted robberies?
Will someone come and steal my PV panels?
The location information is voluntary.

If thieves want to target a home, they could use:

• Driving around the suburbs.
• Property Value information from Metro General Property Valuation Register
• Property24.
• Google Earth (Satellite) or other satellite site.
• Bing Street View/Google Street View
   

1 hour ago, Scubadude said:

I would be interested to join. How do you interface your data?

There is a forum & help site that discusses how to upload data:
https://pvoutput.org/help/index.html
https://forum.pvoutput.org/
There are various methods - some involve push, some involve pull.
There are 2 API's one for daily and one for real time.
I think the "daily" one is legacy.
I used the "daily" api via "cURL" to upload the previous days readings as documented in the API
https://pvoutput.org/help/api_specification.html

curl -s -H "X-Pvoutput-Apikey: $Your_API_Key" -H "X-Pvoutput-SystemId: $Your_System_Id"  \
     -d "d=$Date" -d "e=$Exported" -d "c=$Consumption" -d "ip=$Import_Peak" -d "cd=$Condition" -d "g=$Generated" -d "pp=$Peak_Power" -d "pt=$Peak_Time" \
     https://pvoutput.org/service/r2/addoutput.jsp

Enjoy

To answer the original question as simply as possible; In summer you will get a max of 6 X installed panel and in winter 4 X installed panel...Average, summed over the entire day from dawn to dusk. You may get > 100% of installed panel power in bursts though.. Today I got 110% of rated installed panel power.

It also depends on the orientation and angle of your panels, but the above is a good estimate of what can realistically be achieved..

My best months are in Sept/Oct and worst June/July but my panels are at an angle of 22 deg, North facing which is not ideal in Winter but perfect in summer. In summer in JHB we get rain and heat, both lower production...

Also remember your panels will only "produce" what your load is so its difficult to predict how much you will use of the power that is possible. Also consider in low light conditions you want as many panels as possible/allowed but this means you will be "wasting" money in good conditions because your inverter may limit power production due to max (A) reached, clipping..

My plan was to install the max my inverter could cope with.....

 

On 2021/12/04 at 10:03 AM, TheoVogel said:

Hi Guys, 

I am sure was asked before, but searches weren't very successful,  probably because million keywords around the same topic. 

Could you please post your solar production graphs my month. I live in Johannesburg and is trying to predict my production how much my solar system would produce during the autumn and winter months. 

Thanks 

Theo

This is a hard question to answer actually.

Firstly there are a lot of variables, like the exact orientation of your panels, the number and type of panels, their angle of tilt etc.

Secondly my system seldom produces it's theoretical maximum: either because the property's demand for power is less, or because bad weather reduces it's output. My system is set to not export. So on a sunny day, it will generate maximum PV until the battery is charged, then will generate just enough to keep the house running. I think I've seen about 20 kw/h a time or two, but most clear days I won't get near that because the demand isn't there and so the system doesn't generate power it can't do anything with.
 

I use this website, which I have found comes in within 5% of my actual annual yield:

https://pvwatts.nrel.gov/

It uses solar irradiance data, not just a "all days are sunny and the sun is at this angle" calculation, but one based on real measurements of how much sunlight falls in an area, accounting for typical number of cloudy vs sunny days.

 

On 2022/01/05 at 11:18 AM, PowerUser said:

Wow, this tool is such a big security risk for targeted robberies! It shows exact location to everyone to see!

Help for other areas.

This link provides for a smallish specific area as per map.

How would one choose a different area like Pta, CT, Bloem, Durbs etc. ?

Edited February 12, 20224 yr by Scorp007
spelling

On 2022/01/27 at 11:02 AM, Paulcupine said:

I use this website, which I have found comes in within 5% of my actual annual yield:

https://pvwatts.nrel.gov/

It uses solar irradiance data, not just a "all days are sunny and the sun is at this angle" calculation, but one based on real measurements of how much sunlight falls in an area, accounting for typical number of cloudy vs sunny days.

 

Although a great resource I find their May, June, July figures higher than Nov, Dec, Jan and that is quite out of line from real figures for Johannesburg.

On 2022/02/12 at 10:55 AM, Scorp007 said:

Although a great resource I find their May, June, July figures higher than Nov, Dec, Jan and that is quite out of line from real figures for Johannesburg.

Interesting...  perhaps the Johannesburg solar irradiance data is not as accurate as the source they are using for Cape Town?

On 2022/02/12 at 10:55 AM, Scorp007 said:

Although a great resource I find their May, June, July figures higher than Nov, Dec, Jan and that is quite out of line from real figures for Johannesburg.

That will depend on the slope of your panels. The one thing that usually confuses the matter is that the shadows are generally much more of a factor in production in winter months, but usually not considered in the calculators. Some do allow you to add horizon data...

9 hours ago, P1000 said:

That will depend on the slope of your panels. The one thing that usually confuses the matter is that the shadows are generally much more of a factor in production in winter months, but usually not considered in the calculators. Some do allow you to add horizon data...

Even if you change the slope of the panels you still get winter months with higher values than in summer months. All my PV is used every day so no wasted PV. Although year on year we do get large variations my 3 year figures would be a good guide for Gauteng.

The site indicates July higher than most summer months. Angle of 26 deg and a 4kW PV.

8 hours ago, Scorp007 said:

Even if you change the slope of the panels you still get winter months with higher values than in summer months. All my PV is used every day so no wasted PV. Although year on year we do get large variations my 3 year figures would be a good guide for Gauteng.

The site indicates July higher than most summer months. Angle of 26 deg and a 4kW PV.

That is correct. Change the angle closer to 0°. At ~23° it should be as close as you can get to the same production every month, lower than that will get more in summer, higher more in winter.

On 2022/01/27 at 11:02 AM, Paulcupine said:

I use this website, which I have found comes in within 5% of my actual annual yield:

https://pvwatts.nrel.gov/

It uses solar irradiance data, not just a "all days are sunny and the sun is at this angle" calculation, but one based on real measurements of how much sunlight falls in an area, accounting for typical number of cloudy vs sunny days.

 

Thanks for this link. I have been looking for this quick reasonably accurate forecasting site. 

 

Thanks for this link. I have been looking for this quick reasonably accurate forecasting site. 

This week knowing we should have clouds and rain I decided to get a forecast from my weather APP and a PV APP. At the top is my normal APP used. One would assume they all have access to the same data and they normally indicate they do regular like 15min updates.

Forecast was done Wednesday morning. My regular APP showed partly cloudy for  Wednesday, Thursday and Friday and by now we know that Wednesday to Friday we had cloudy conditions in Gauteng. 3 hrs, 3 hrs and 6 hrs sun.

The bottom pic did get the current day (Wednesday) correct but indicated full sun conditions for Thursday and Friday.

This demonstrates that even weather/PV APPS are not equal.

 

 

After the rain PV in Gauteng is having a fantastic day. The best peak this summer. 

 

Edited September 30, 20232 yr by Scorp007