Help understanding ONE string for exterior garage (gable facing due South) Panels on both sides of roof

[RevMikeB]

I need to run one string from my exterior garage to grid tie/hybrid inverter. ((((The other 3 strings will be running from the home's roof. The inverter allows for 4 strings/DC inputs. The panels on the house that compile the 3 strings all face due South, which is fine; each of those 3 strings will get equal sun and will NOT require optimizers.))) However, the fourth string on the exterior garage will comprise half the panels or 8 panels on one side of the roof's garage and half or 8 panels on the other side. The roof's gable faces due South, so both sides of panels of the garage will get equal sun in the middle of the day. But only half the panels will get sun in the morning, and the other half will get the sun toward the evening. What is the solution to this problem of unequal sun in parts of the day if the garage panels are all on the same string? Is it possible to use optimizers on one string, but not the other 3? I was planning on running all 4 strings in series. Would it be better to somehow ONLY run the garage string in parallel? I would appreciate the help of any knowledgeable people out there. It's going to take 70 ft of wire to run to the panels from the inverter. Each of the 16 panels have a current of 8.97A & 37.33V at max power.

 

[timselectric]

The two halves of the garage string. Should be installed as two strings in series. And then paralleled together with blocking diodes. This way, you get the most power production throughout the day.

 

[RevMikeB]

Do you mean this?

https://www.amazon.com/Single-Phase-Bridge-Rectifier-Module-Terminals/dp/B07DKZ2S1M/ref=sr_1_59?keywords=solar%2Bpanel%2Bblocking%2Bdiode&qid=1647121322&s=industrial&sr=1-59&th=1

 

[RevMikeB]

The two halves of the garage string. Should be installed as two strings in series. And then paralleled together with blocking diodes. This way, you get the most power production throughout the day.

So, do I use two diodes, one for each side of the garage? From the solar panels, connect the positive solar cable to diode positive (in) and negative to negative. For the 2 outs from both diodes, y them together to connect the positives together and the negatives together to combine both sides into one, making one cable (meaning 2 wires) to run to the inverter from the garage?

 

[timselectric]

So, do I use two diodes, one for each side of the garage? From the solar panels, connect the positive solar cable to diode positive (in) and negative to negative. For the 2 outs from both diodes, y them together to connect the positives together and the negatives together to combine both sides into one, making one cable (meaning 2 wires) to run to the inverter from the garage?

One diode on each string positive , before the Y.
Then, just a Y on the negatives.
One positive and negative, to the inverter.

 

[timselectric]

ZOOKOTO 5pcs Solar Panel PV Connector with Built in 20A Diode Waterproof Solar Panel Cable Connector https://www.amazon.com/dp/B0825HS2VQ/ref=cm_sw_r_cp_apann_glt_i_A03KMCHNEJ4JEWR77GYP

 

[RevMikeB]

One diode on each string positive , before the Y.
Then, just a Y on the negatives.
One positive and negative, to the inverter.

Sorry to ask, but can you link what it is? So not 2 of these diodes? https://www.amazon.com/Single-Phase...iode&qid=1647121322&s=industrial&sr=1-59&th=1

 

[timselectric]

Sorry to ask, but can you link what it is? So not 2 of these diodes? https://www.amazon.com/Single-Phase-Bridge-Rectifier-Module-Terminals/dp/B07DKZ2S1M/ref=sr_1_59?keywords=solar+panel+blocking+diode&qid=1647121322&s=industrial&sr=1-59&th=1

Sorry, edited above.
First link was wrong.
Fixed now.

 

[rmaddy]

And then paralleled together with blocking diodes.

Is this actually needed if the panels already have bypass diodes?

Depending on the specs of the charge controller why not put the 16 panels in 8S2P and then there is nothing to deal with at all. If the controller can't handle the 2P then put the panels in 16S (even though half are on each side of the garage) and let the panel bypass diodes do their job.

 

[timselectric]

Is this actually needed if the panels already have bypass diodes?

Depending on the specs of the charge controller why not put the 16 panels in 8S2P and then there is nothing to deal with at all. If the controller can't handle the 2P then put the panels in 16S (even though half are on each side of the garage) and let the panel bypass diodes do their job.

This is a blocking diode.
Not to be confused with a bypass diode.
Two totally different functions.

8s2p is what I am referring to.

 

[rmaddy]

This is a blocking diode.
Not to be confused with a bypass diode.
Two totally different functions.

8s2p is what I am referring to.

I understand that they are different. That's why I asked. Why would a blocking diode be needed at all, especially at 8S2P? And at 16S the bypass diodes of the panels would allow half of the string to still work even if the other half is fully in shade.

 

[timselectric]

The string that is producing more power, will be pushing power into the string that is producing less power. The blocking diode makes all produced power go to the inverter.

 

[timselectric]

Diodes decrease efficiency slightly.
16s = 8 Diodes of efficiency loss. (Or more, depending on how many diodes are in each panel)
8s2p = 1 Diode of efficiency loss.

 

[Phil.g00]

Blocking diodes are not necessary.
A string only conducts in reverse above its Voc.

 

[timselectric]

 

[RevMikeB]

ZOOKOTO 5pcs Solar Panel PV Connector with Built in 20A Diode Waterproof Solar Panel Cable Connector https://www.amazon.com/dp/B0825HS2VQ/ref=cm_sw_r_cp_apann_glt_i_A03KMCHNEJ4JEWR77GYP

Sorry, edited above.
First link was wrong.
Fixed now.

Got ya. Yeah, that first link was ONLY a fuse, no diode. Thanks, that looks pretty easy to do and it would seem to make it more likely to function properly than just relying on the diodes in the panels to do their job.

One diode on each string positive , before the Y.
Then, just a Y on the negatives.
One positive and negative, to the inverter.

So, to be clear, I'm running each side of the garage in series (negative to positive) all the way across. Then at the end of row, both positives (one on each side of the garage) each get plugged into their own diode and then plugged into a y combiner to come out with one plug that runs one positive wire to the inverter. Both negative plugs get plugged into a y combiner to come out with one plug that runs one negative wire to the inverter. This solves the problem of different amounts of sun on the east or west sides of the garage while being able to run the entire garage on one string. Thus, isn't the configuration kind of like having two separate arrays each wired in a series (facing east & west) that come together to be wired in parallel? Am I saying this correctly? And one other question: what happens with the current and volts with such a configuration? In the middle of the day, would the max voltage and amps be the same as if the whole garage (all 16 panels) were wired in series and run directly to the inverter? I want to make sure I get the right gauge wire.

 

[timselectric]

Got ya. Yeah, that first link was ONLY a fuse, no diode. Thanks, that looks pretty easy to do and it would seem to make it more likely to function properly than just relying on the diodes in the panels to do their job.



So, to be clear, I'm running each side of the garage in series (negative to positive) all the way across. Then at the end of row, both positives (one on each side of the garage) each get plugged into their own diode and then plugged into a y combiner to come out with one plug that runs one positive wire to the inverter. Both negative plugs get plugged into a y combiner to come out with one plug that runs one negative wire to the inverter. This solves the problem of different amounts of sun on the east or west sides of the garage while being able to run the entire garage on one string. Thus, isn't the configuration kind of like having two separate arrays each wired in a series (facing east & west) that come together to be wired in parallel? Am I saying this correctly?

Yes, exactly.

 

[RevMikeB]

Yes, exactly.

Thanks for all your help. I really appreciate it.

 

[RevMikeB]

Thanks for all your help. I really appreciate it.

And one other question: what happens with the current and volts with such a configuration? In the middle of the day, would the max voltage and amps be the same as if the whole garage (all 16 panels) were wired in series and run directly to the inverter? I want to make sure I get the right gauge wire.

 

[timselectric]

Voltage would be of 8 in series.
Amperage would be of 2 in parallel.
According to the panel specs.