Old mods - new optimizers

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Zee

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How would you add Solaredge optimizers to an (E) array of 20 @ 180W SunTech mods?
72 cell
5.4 Isc
44.4 Voc
2 strings of 10 mods
built in 2008

--Do they have optis for retrofits like above?

---Background:
Gonna add add'l 6-9 kW of PV, and need to meet rapid shutdown. Too confusing to leave old mods w/o RS and add new mods with RS.
Also will replace (E) 4 kW SMA INV with larger SE INV, 7.6 or 11.4 kW likely )
 
I have personally added P320 Opti though they are specifically for 60 cells modules, TO 72cells modules if the VOC Falls under limiting 48 volts. Looks like VOC 44.4 of existing solar modules is under the limit voltage 48 volts for SE P320 OPTIMIZERS. MAX Isc for p320 optimizers is also 11amps which falls under the criteria. (Some AHJ Only look specs and wants you to change the optimizer that fits 72 cells module )
IF You add the new optimizers to existing solar modules and connect it to new solaredge inverter they will be rapid shutdown compliant as SolarEdge optimizers have module level rapid shutdown compliance.
Also code allows if you can separate old modules and new modules and keep the placards per NEC 2017 690.56 C(1)(a) and 690.56 (2) keeping old module's and inverters as it was.
 
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Thank you I agree.

Wonder if anyone has experience or knows ,if I can combine these 20 panels into one circuit, even though they are two now.
It's just 3600 Watts total.

I am thinking of several different methods including
- paralleling two mods at a time per Opti
- or stringing all 20 together

I'm wondering how the optimizers would handle the voltage in just one long string of 20.

Sent from my SM-G950U1 using Tapatalk
 
Zee said:
Thank you I agree.

Wonder if anyone has experience or knows ,if I can combine these 20 panels into one circuit, even though they are two now.
It's just 3600 Watts total.

I am thinking of several different methods including
- paralleling two mods at a time per Opti
- or stringing all 20 together

I'm wondering how the optimizers would handle the voltage in just one long string of 20.

Sent from my SM-G950U1 using Tapatalk
Click to expand...

Optimizers act analogously to miniature transformers, that can dynamically adjust their buck/boost ratio. Like transformers, they trade voltage and current analogously to what gears do with rotation speed and torque, with the product of voltage and current being roughly equal on both sides of the device. Unlike transformers, they are built for working with DC instead of AC, and do not isolate the two sides.

The raw open circuit voltages of the modules do not add up, like they ordinarily do when modules are directly connected in series. What happens is that the inverter prescribes an operating voltage, and the optimizers work together to solve the algebra problem in order to satisfy Kirchhoff's laws. Current must be the same in all, because they are in series. Voltage comes in proportion to the power that each can produce, and adds up to the voltage set by the inverter. What is "optimized", is that the optimal point of each module (or pair of modules) is tracked separately, and mismatch losses and shading are localized to the individual module, such that "one bad apple" no longer "spoils the whole pot".

The constraint on string sizing is such that DC module power at STC is limited to the amp rating of the optimizers multiplied by the inverter-prescribed operating input voltage. There is also a minimum number of optimizers per string, typically 8, depending on the specific products selected. In the case of the 7.6 kW HD wave inverters, the input voltage is 400V, and typical individual module optimizers are limited to outputting 15A. This means 6000W is the maximum power per string, in this example.

The voltage input range needs to be coordinated with the low temperature Voc for the modules, for your location's ASHRAE low design temperature. Given P320 optimizers limited to 48V input, this may look like it can handle your 72-cell modules, but you need to realize that the Voc has to be adjusted for your design low temperature. It may bleed beyond 48V, thus requiring you to use an optimizer that has a higher input voltage capacity.
 
Use an opti built for 72 cell modules. Looks like you could put two of those modules in parallel on a P401. ;) Short circuit current is within spec. Ask Solaredge though.
 
Yes, a higher V window will be needed due to 72 cell mods in cold temps.

Is there a max # of mods per string? Prolly best to ask SE. I know they publish minimum maximums but also now interesting things developed in conversations here.
I mean in theory, I could do 33 mods (!) in one string..... before I hit the 6000 W limit.


I was thinking of paralleling two mods per Opti also due to Amps being half of today's mods and wattage is half too.

Sent from my SM-G950U1 using Tapatalk
 
Zee said:
Is there a max # of mods per string? Prolly best to ask SE. I know they publish minimum maximums but also now interesting things developed in conversations here.
I mean in theory, I could do 33 mods (!) in one string..... before I hit the 6000 W limit.
Click to expand...

The wattage limit is your limit to comply with SolarEdge's design constraints. As long as you don't exceed the STC watts per string governed by the inverter-specified operating voltage and optimizer-specified maximum output current, and as long as you have the minimum they require in series, your system will still work. The other limit that would apply, is max 30 optimizers per string when needed to comply with rapid shutdown, as they default to 1 volt per optimizer when the system is turned off.

It's an unknown whether your AHJ will require you to comply with rapid shutdown, or let it just comply with NEC 2008 as it once did. But if you design to the 30V limit applies regardless, you are covered either way.
 
Designer101 said:
I have personally added P320 Opti though they are specifically for 6s, TO 72cells modules if the VOC Falls under limiting 48 volts. Looks like VOC 44.4 of existing solar modules is under the limit voltage 48 volts for SE P320 OPTIMIZERS0 cells module. MAX Isc for p320 optimizers is also 11amps which falls under the criteria. (Some AHJ Only look specs and wants you to change the optimizer that fits 72 cells module )
IF You add the new optimizers to existing solar modules and connect it to new solaredge inverter they will be rapid shutdown compliant as SolarEdge optimizers have module level rapid shutdown compliance.
Also code allows if you can separate old modules and new modules and keep the placards per NEC 2017 690.56 C(1)(a) and 690.56 (2) keeping old module's and inverters as it was.
Click to expand...
I hope that there is some margin in the 48V limit (like "for 48V nominal panels")
In a cold climate the winter morning Voc can be up to 25% higher than the STC nominal Voc.
 
GoldDigger said:
I hope that there is some margin in the 48V limit (like "for 48V nominal panels")
In a cold climate the winter morning Voc can be up to 25% higher than the STC nominal Voc.
Click to expand...

The P320 is designed for only 60 cell modules up to 320W, which have an STC Voc of around 38V and should never get up to 48V in typical circumstances. That's why he needs to use one of their optimizers that is designed for higher voltage modules, preferably those designed for 72 cell moduels that have an 80V max DC input. The P400 has the voltage rating, but doesn't have the short-circuit current rating to connect two modules in parallel. The P405 is probably the one. The P370 might also do, but is more borderline on the voltage.
 
Looks like the P370 will be ideal. It has a max Voc of 60V, so no problems there. Max Isc is 11A, so two modules in parallel puts you at 10.8A.
 
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