Generator or Inverter for residential use?

signates

Executive Member
Joined
Dec 8, 2009
Messages
7,151
Ended up using 29% of the battery during the 2 hours of load shedding even with the aircon running. DB did not trip when the grid came back online.

Should end up with 1.6MWh for December and nearly 6MWh since commissioning. Screenshot_20201231-105131_solarmanPro.jpg
 

signates

Executive Member
Joined
Dec 8, 2009
Messages
7,151
Hi @signates , what Solarman app is this
Solarman Business

 

Saba'a

Executive Member
Joined
May 21, 2009
Messages
5,897
Interesting list of solar panels.


I'm considering installing some pv panels during this year.


I have an 8.8kw Sunsynk inverter and 2 x 3.5kw Pylontechs (aiming to add another 2 or 3 batteries but at a much later stage only).

House, excluding 3 x geysers, seem to peak at 5 max 7kw at a time and consumes max 25kWh a day.

I'll reduce it more by installing a gas oven, already using gas stove.

Any suggestions ito PV panels?


Also how to calculate
1. how much I should aim to generate (given days of low production) and
2. thus how many panels should I install without wasting production?

I could use some excess for the geysers of course, so excess could be utilised.
 
Last edited:

RonSwanson

Executive Member
Joined
May 21, 2018
Messages
5,150
Interesting list of solar panels.


I'm considering installing some pv panels during this year.


I have an 8.8kw Sunsynk inverter and 2 x 3.5kw Pylontechs (aiming to add another 2 or 3 batteries but at a much later stage only).

House, excluding 3 x geysers, seem to peak at 5 max 7kw at a time and consumes max 25kWh a day.

I'll reduce it more by installing a gas oven, already using gas stove.

Any suggestions ito PV panels?


Also how to calculate
1. how much I should aim to generate (given days of low production) and
2. thus how many panels should I install without wasting production?

I could use some excess for the geysers of course, so excess could be utilised.
How much roof space have you got (if installing on a roof), dimensions and what is the azimuth?
 

wingnut771

Honorary Master
Joined
Feb 15, 2011
Messages
11,806
Interesting list of solar panels.


I'm considering installing some pv panels during this year.


I have an 8.8kw Sunsynk inverter and 2 x 3.5kw Pylontechs (aiming to add another 2 or 3 batteries but at a much later stage only).

House, excluding 3 x geysers, seem to peak at 5 max 7kw at a time and consumes max 25kWh a day.

I'll reduce it more by installing a gas oven, already using gas stove.

Any suggestions ito PV panels?


Also how to calculate
1. how much I should aim to generate (given days of low production) and
2. thus how many panels should I install without wasting production?

I could use some excess for the geysers of course, so excess could be utilised.
Do you have a meter that turns backwards?
 

Neuk_

Expert Member
Joined
Jan 23, 2018
Messages
4,749
Interesting list of solar panels.


I'm considering installing some pv panels during this year.


I have an 8.8kw Sunsynk inverter and 2 x 3.5kw Pylontechs (aiming to add another 2 or 3 batteries but at a much later stage only).

House, excluding 3 x geysers, seem to peak at 5 max 7kw at a time and consumes max 25kWh a day.

I'll reduce it more by installing a gas oven, already using gas stove.

Any suggestions ito PV panels?


Also how to calculate
1. how much I should aim to generate (given days of low production) and
2. thus how many panels should I install without wasting production?

I could use some excess for the geysers of course, so excess could be utilised.

There are more variables than the obvious to think about including...

Roof layout/size - Sometimes it is more efficient/effective to go for a lower rated and smaller PV panel but be able to fit more on a roof than to simply buy the largest rated and sized PV panel.
Daytime use - Many forget that they need to include the charging requirements of their batteries in to the size of their PV setup so take this in to account as well.

Then there is the obvious of peak day time use, the PV that the inverter can handle if it uses built in MPPT, orientation of your roof for a North facing setup or perhaps and East/West split like we had to go for, etc, etc. As for the calculations, I believe there is software that installers use that can calculate this but I take it with a pinch of salt as it is massively dependent on available sunlight and load.
 

Saba'a

Executive Member
Joined
May 21, 2009
Messages
5,897
How much roof space have you got (if installing on a roof), dimensions and what is the azimuth?
Roof space not an issue.

Azimuth result attached.

Interesting link:

aa9066c67caebb2d8770a31840c9fc84.jpg
 

Saba'a

Executive Member
Joined
May 21, 2009
Messages
5,897
There are more variables than the obvious to think about including...

Roof layout/size - Sometimes it is more efficient/effective to go for a lower rated and smaller PV panel but be able to fit more on a roof than to simply buy the largest rated and sized PV panel.
Daytime use - Many forget that they need to include the charging requirements of their batteries in to the size of their PV setup so take this in to account as well.

Then there is the obvious of peak day time use, the PV that the inverter can handle if it uses built in MPPT, orientation of your roof for a North facing setup or perhaps and East/West split like we had to go for, etc, etc. As for the calculations, I believe there is software that installers use that can calculate this but I take it with a pinch of salt as it is massively dependent on available sunlight and load.

Thanks.


I can cover any direction as roof space quite large. But East West less than north south.

Assumed pv panels standard size - will ask installer to consider that.

Was hoping to calculate need based on

A. Peak power required
B. Max kWh per day
C. Extra for battery and geysers
D. Max that 8.8kw inverter and 7kWh (think limited to 5.6kWh?) battery setup can handle.
E. Can I delay adding more batteries?

Also hoping to ensure capacity for bad days when less power generated. So maybe 50% extra capacity to compensate?

Excess can be used for geysers.
 

Saba'a

Executive Member
Joined
May 21, 2009
Messages
5,897
Then you don't have to worry about "wasting production", spin that baby backwards for when the sun don't shine.
Agreed but still dont want to over invest. So need to figure what I need minimum plus some extra for the poor days.

Rather use savings to buy additional batteries and/or greywater system.

Want to have an idea to avoid installer calculating a system larger than my needs.
 

Speedster

Honorary Master
Joined
May 2, 2006
Messages
12,375
Agreed but still dont want to over invest. So need to figure what I need minimum plus some extra for the poor days.

Rather use savings to buy additional batteries and/or greywater system.

Want to have an idea to avoid installer calculating a system larger than my needs.
With a spinning meter you only need enough batteries to get you through a night time load shedding shift.
 

RonSwanson

Executive Member
Joined
May 21, 2018
Messages
5,150
  • Roof space not an issue.

Azimuth result attached.

Interesting link:

aa9066c67caebb2d8770a31840c9fc84.jpg
So your roof is largely NNW facing?

I am assuming that your approach would be to design with the final solution in mind, that way you can build it up and not have unnecessary expenses. I am also assuming that your final "dream" solution would be to minimise Eskom entirely. I am going make an educated guess, from your stated utilisation figures I would say that your utilisation is just under 1000 units per month, around 33 units per day?

This means that your final solution would probably need just over 10 KWp in solar panels. The 8.8K Sunsynk can handle 10.4, so it's cool.
It has two MPPTs, each needs a minimum of 150V to start, but I hear that they prefer it closer to 400V. 500V is max, but to be safe I would try not to exceed 425V. Each MPPT can also take two parallel strings, provided that the current does not exceed 18A. I'd say that its pretty flexible.

Looking at panels, you say you have no problem with space which means that you can play with lower wattage (and perhaps cheaper) panels and just get more of them, although there are diminishing returns with cable lengths and mounting hardware. Also, if you are going to do it in phases, you need to consider panel availability, mixing different types, brands and models over a 3 year period could cause all sorts of problems and inefficiencies. I would opt for a strong brand like JA Solar where I know that I can order a specific panel model 3 years after initial purchase and still be able to get it.

So let's look at the JA Solar 455W JAM72S20, was going for just over 2K last year.
You will need 4 panels to kickstart the MPPT, so your absolute minimum will be 4 in 1 series string, using only 1 MPPT. You can put 9 in series without exceeding operating voltage (425v) at NOCT, but if you really want to be safe (think cold winter's day) it probably needs to be reduced to 8. So max 8 in one series string, but they are still only producing 8.72A, so you can add another 8 in parallel. 16 panels are already 7280KWp, and you still have another free MPPT!
Back to efficiencies, consider wiring both MPPTs for this (if the cable runs are less than 38 metres you can use 6mm cable), and then just add panels as you can afford. 22 panels would give you just over 10KWp.
 

gbyleveldt

Senior Member
Joined
Apr 30, 2009
Messages
592
Our average home consumption is between 900-1000kwh a month. In Dec, the 16*405w JA Mono panels generated 937kwh of solar. Panel total is 6.4kw but often goes up to 7kw in the mornings when it’s a little cooler. 6*us2000 batteries are usually charged by noon. I might be able to add another panel on each string, but I’ve hit the practical limit of roof space. I don’t think there is a thing like too much panels; they are the cheapest expense of the whole system after all. Start with 8 panels on one string and if you get more budget, add another 8 panels later on.

Panels are facing just slightly east of true north, not sure the angle but it’s a pretty standard pitched roof.

Just to give you some perspective.
 
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