DIY OG Solar install

This is what i pictured when he said fuse box which would be a dead short (naturally once the fuse is in)
 

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Calculating panel output via:

1) Sqm:

width x length = sqm
2.2 x 6.6m = 14.5sqm

sqm * 1kw/sqm x module efficiency
14,500 * 20% = 2,800w

Vs.

2) Panel specs:

number of panels x panel wattage
6x 550w = 3,300w

Where am I going wrong? What accounts for the disparity between the two?
 
leon.davibe said:
This is what i pictured when he said fuse box which would be a dead short (naturally once the fuse is in)
Click to expand...
Dunno.

He refers to it as a 'fuse-block'.

I presume current is color blind, so according to the theory established earlier in this thread... the current would move into the positive bus-bar and then run up the wire into the 'fuse-box' and then continue up the negative side.

If it isn't a block of fuses, what kind of 'block' is it?
 
itareanlnotani said:
Ideally you want as much PV as you possibly can fit within budget. Go with 120% of inverter capacity.
So if you have a 5KW inverter, 6KW of panels
Click to expand...
It looks like the space we are looking at for panels is going to be about 7x 550w panels, max. (but as I mentioned the usgae is now coming to less than 450/mnth. They discovered a very thirsty fridge is accounting for the vast majority of the energy they consume as much as 90% or more. So they are going to look to cut that fridge consumption by around 2/3rds i.e. 66%)

So anyway, if that PV output comes to 3,850w, then by your 120% rule of thumb, the inverter should ideally be around 3,200w, to match the PV arrays.

Is that correct?
 
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To reiterate:


Panels -> mini db. Cabling in conduit. DC breaker at DB (looks like a normal household one, but DC rated). Lightning protection if needed (i.e Jhb etc) Mini db -> Inverter. I've seen installs without this. Makes maintenance a hassle.

Batteries -> DC fused breaker (Jean Muller or Keto ones are decent) -> Inverter. Ensure cable thickness is sufficient for load. This is an area they will cheap out on occasionally.

Eskom -> Inverter. Depending on location muni or elec supplier may also require an switch here too. ATS or otherwise.

Inverter -> house DB (for "essential loads" - fridge, lights tv...)
Inverter -> non essential load if Eskom is down. (i.e. a geyser circuit)

I'd get someone in to do it, just make sure that they do a decent job.
 
lexity said:
Says

Lux Power 5KW SNA Inverter 2 MPPT - With Gen Input​

Lux Power 5KW OFFGRID Inverter (SNA5000WPV) Description Applicable for pure off grid/ backup power / self-consumption / on grid situation Integrated with 2 MPPT solar charge controllers, MPPT ranges 120V~385V Rated power 5KW, power factor 1 Be able to run with or without battery in Ongrid and...
www.ptonline.co.za
www.ptonline.co.za
lexity said:
Speedster said:
3 should work
Click to expand...
3 what?
Click to expand...
bump
 
lexity said:
Which should be 80% of which?
Click to expand...
If you have 7 50v voc panels it would be 350v as long as this is less than 80% of the max voc of charge controlelr lets say 450v then you have 77.7%

Now yes you can go closer but then you have to do the math with the temps of your area
To be sure it won't hit 450v in record low temps
 
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lexity said:
Calculating panel output via:

1) Sqm:

width x length = sqm
2.2 x 6.6m = 14.5sqm

sqm * 1kw/sqm x module efficiency
14,500 * 20% = 2,800w

Vs.

2) Panel specs:

number of panels x panel wattage
6x 550w = 3,300w

Where am I going wrong? What accounts for the disparity between the two?
Click to expand...
Is the 20% the device spec or a rule of thumb, some higher
 
lexity said:
3 panels in series at 42v each is 126v so that is enough for one mppt, right? If you do 6 panels you could have 126v per mppt.
Click to expand...
Wouldn't really be enough, I'd put 4 in series at least.

Otherwise your MPPT side is going to sit there doing nothing for half the day till the panels get enough voltage via the big shiny star thing in the sky to get going.
 
itareanlnotani said:
Wouldn't really be enough, I'd put 4 in series at least.

Otherwise your MPPT side is going to sit there doing nothing for half the day till the panels get enough voltage via the big shiny star thing in the sky to get going.
Click to expand...
Slight mods to the pv input install:

Now there will be 2x strings of 4x 550w panels each. (550w is the advertized number on each panel)

2200w per string. So, a total of 4400w.

Is this per hour?

What can I expect in terms of generation from 4400w? The average solar exposure for my area is 5.7kw per day(5.7hrs of sufficient sunshine).

What losses should I factor in?
 
lexity said:
Slight mods to the pv input install:

Now there will be 2x strings of 4x 550w panels each. (550w is the advertized number on each panel)

2200w per string. So, a total of 4400w.

Is this per hour?

What can I expect in terms of generation from 4400w? The average solar exposure for my area is 5.7kw per day(5.7hrs of sufficient sunshine).

What losses should I factor in?
Click to expand...
For the first question, see here: https://mybroadband.co.za/forum/threads/what-are-watts-and-watt-hours.1240325/

4400w should give around 4000w peak and 20kwh on a good day.
 
lexity said:
Slight mods to the pv input install:

Now there will be 2x strings of 4x 550w panels each. (550w is the advertized number on each panel)

2200w per string. So, a total of 4400w.

Is this per hour?

What can I expect in terms of generation from 4400w? The average solar exposure for my area is 5.7kw per day(5.7hrs of sufficient sunshine).

What losses should I factor in?
Click to expand...
It's theoretical max you'll see per hour in an ideal world.

Realistically, you'll probably pull around 5hrs of that in summer (as Speedster says +-20kWh/day), and 1-2hrs of that in winter (4-8kWh/day) as an average in WC, better winter figures in other areas.

The actual output will increase during the day from sunrise on, peak at midday, then go back down to zero at sunset.
Your output curve will look something like this. Peak will be your 4400W less some conversion losses, and losses from heat in summer, as panels typically lose some < percent for every degree over STC (25c)


images



Some graphing of solar averages in different areas here - https://www.news24.com/news24/tech-...olar-output-in-every-province-in-sa-20230518#




Going back to your setup as stated -

Panels will be 50v each VoC x 4 = 200V (+-at worst)
Your Luxpower 5KW inverter is MPPT ranges 120V~385V

I'd lean toward 5 x 550W panels per string x 2 (or 50 x 5= 250V which is still fine), then voltage will be hit earlier in winter, vs later.
Winter will give you more output.

Luxpower datasheet says 6000W is fine, that will max out at 5500W. I'd actually lean towards 6 per string (for 300V max VoC, even with 20% safety -> 360v, its still safely under the 385v max voltage). Which puts you at 6600W. The inverter says it will handle 6000W, so you'll still get most of that output, then it SHOULD clip amp's if it goes over that.

However, I'm not familiar enough with those inverters to say yay or nay for amp clipping. Check with installer regarding how they clip when input is higher. Remember, Volts NEVER go over. Amps - less of a deal, as (good) inverter(s) will clip.

Example of what happens when inverter clips:

Picture3-500x373.png


Ideally, overspec panels for winter needs. The more you have, the longer you'll get output (as seen in graph above).
Summer, its a slight waste as you chop off the potential extra for some of the day, but not a big one.
 
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