Why should i not do this with my solar?

[patman30]

Just looking to see if anyone with experience/knowledge knows why this would be bad
i have an OFF GRID solar setup 3 x 5kw growatt inverters with 4 x 15kw SOC
first things first
i am not looking to add to may current PV arrays, i am certainly not looking to climb up onto my roof.

What i want to do is add panels on the east and west WALLS of my house
to capture sun during the early morning and late evening
at these times my current PV array is not getting much light and by the time it is, the newer panels will not be getting any
and obviously when sun is on east wall the west is in shade and vice versa
breaking it down to just 1 inverter (so this times 3)
i would like to add a 600w panel on the west wall
and on the east wall will be 2 x 150w panels connected in series
i will then have these connected in parallel to the inverter 

what i read online is always about trying to maximize etc and how lowest voltage or current is used when mixing panels
but these are not for that
i have 2 PV inputs on the inverters so will make use of the 2nd unused input
is it fine to join these 2 when connecting to inverter?
only one or the other will have sun at any one time
so i fail to see how any difference between voltage and current from diff panels would have any effect as only one will have sun

any input is appreciated, thanks
 

[Crossy]

If you are running strings in parallel to a single MPPT input your strings should have approximately the same Voc total (say within 10% although it's not a hard and fast rule).

 

The strings come up to voltage very quickly when there is any light at all, there's just no power there (they will certainly make your eyes light up mind).

 

Sketch out what you want to do (including the panel quantities and parameters) and post here, we should be able to determine just how well things will worth for you.

 

[Crossy]

21 minutes ago, patman30 said:

i would like to add a 600w panel on the west wall
and on the east wall will be 2 x 150w panels connected in series
i will then have these connected in parallel to the inverter 

 

What are the parameters of your panels (post photos of the labels)?

 

Vertical panels are certainly finding favour in the higher latitudes, but the sun rises so rapidly here I'm wondering just how much extra energy you would actually gain.

 

Moved to the Alternative Energy forum.

[patman30]

13 minutes ago, Crossy said:

What are the parameters of your panels (post photos of the labels)?

Vertical panels are certainly finding favour in the higher latitudes, but the sun rises so rapidly here I'm wondering just how much extra energy you would actually gain.

 

i have not yet purchased the panels
but the ones below are what i am looking at, the ones to go on east wall are based purely due to where they will be fitted
the 600w also on size as i only have enough space for 3 large panels on the west wall
yes you are correct the sun does rise rapidly but these are just to get any extra where possible 
as i am maxing out battery use, and yes i am up in the mountains so sun can be very low morning and evening
this is basically what i want to do

 

 

here are the panels i am looking at

and

 

 

 

 

 

 

[Crossy]

2 x 150W in series = a Voc of 44.92V

 

In parallel with your 600W Voc of 49.53V

 

That's about a 10% difference in Voc. It will certainly work, just how much efficiency you lose is debatable.

 

I'd be tempted to add a >20A Schottky diode in series with the 150W panels to avoid reverse-biasing them (which they really don't like).

 

Is there really not room to put a 600W on both walls??

[patman30]

8 minutes ago, Crossy said:

2 x 150W in series = a Voc of 44.92V

 

In parallel with your 600W Voc of 49.53V

 

That's about a 10% difference in Voc. It will certainly work.

 

I'd be tempted to add a >20A Schottky diode in series with the 150W panels to avoid reverse-biasing them (which they really don't like).

ok will take a look
only thing i thought if there was any issue with the setup would be put the panels on timers so they are disconnected during times they don't get sun, so only the 2x150w or the 600w are connected at any one time

 

This was yesterday
the red square is where i want to get a bit more power (this would be from the 600w panels)
the east facing panels will just be a little bonus

[Crossy]

3 minutes ago, patman30 said:

only thing i thought if there was any issue with the setup would be put the panels on timers so they are disconnected during times they don't get sun, so only the 2x150w or the 600w are connected at any one time

 

You need to be very, very careful switching panels when it's light. DC is a very different animal to the AC most timers are designed to switch.

 

I would be tempted to try it as you suggest and see how well it works, then add the blocking diode, then try actually disconnecting one array at a time.

[Crossy]

Another thought. What is the start-up voltage of your second MPPT input? Will one panel actually get it going?

[patman30]

1 minute ago, Crossy said:

Another thought. What is the start-up voltage of your second MPPT input? Will one panel actually get it going?

will have to check manual, i was assuming it would just be a 2nd input for adding a 2nd array as inverter is already running,
as for timers, yes may be tricky, timer would likely need be separate/AC powered
but it would be more to connect panels only during times they get sun so then only one (or none) connected at a time,
worst case for this would just be myself flicking breakers during the day (which would quickly get tiresome)
but again this would only be done if needed

[patman30]

@Crossy Another option i have 
*i have space for 7 x 150w panels
and could fit 1 more 600w panel so 4 total (area is only 75% in light right now at 3:30pm)
and connect the 1050w (7x150) to 1 inverter (or 900w maybe 6 x 150, or possibly 1200w with 1 panel on a south facing wall)
and connect 1200w (2x600) to the other 2 inverters
would this be a more sensible approach do you think?