PV Inputs and Sizing

[steveap]

Hi,
I'm looking at purchasing a 20Kw hybrid inverter along with a 48Kwh battery stack. The following are the inverter specs:

Number of PV string connections: 8
Number of MPP tracking units: 2
Maximum input voltage pv: 500 VDC Total
Input voltage range (functional): 80 - 500VDC
Input MPP tracking range: 80 - 500VDC
Input current per PV input: 32 ADC max (per string)
Input power per PV input: 3,7500W max (per string, up to 8 strings)

A lot of other specs are available on the inverter but I put here just the ones I thought would be needed to answer my questions. I don't have a strong knowledge on the ramifications of each of these specs, but what would be the ideal solar panel configuration (ground mount)? I'm thinking about a16Kw panel array of approximately 36 bifacial panels, give or take a few panels and/or give or take a few Kw of approximately 440 plus or minus watts each panel. What would be the ideal panels and the ideal series/parallel configurations? And would the added expense of micro-inverters be worth the extra expense? I've heard somewhere that a couple extra panels will more than make up for the lack of micro-inverters. Your help in this part of my project design is sincerely appreciated.
Thank you.

 

[BentleyJ]

Could you clarify the specs posted above. If there are 2 MPP tracking inputs what did you mean by Input Power 3,7500W? So Is that 3 inputs at 7,500W each?

In any case, typically we would recommend putting as many panels in series as will fit and stay under the Max Voltage limit. This reduces the amount of wiring needed vs. having more parallel strings. The exception to the rule would be in situations with shading. For example with 12 panels 2 strings of 12 would be the usual configuration. However, if there is shading in an area that affects 4 panels then it would better to group 4 in one string so its the only one with low output due to shade. The other panels would be either be grouped in string of 8 if Voltage limit allows or 2 strings 4 in parallel if the Max Current on the MPPT allows this.

 

[steveap]

Could you clarify the specs posted above. If there are 2 MPP tracking inputs what did you mean by Input Power 3,7500W? So Is that 3 inputs at 7,500W each?

In any case, typically we would recommend putting as many panels in series as will fit and stay under the Max Voltage limit. This reduces the amount of wiring needed vs. having more parallel strings. The exception to the rule would be in situations with shading. For example with 12 panels 2 strings of 12 would be the usual configuration. However, if there is shading in an area that affects 4 panels then it would better to group 4 in one string so its the only one with low output due to shade. The other panels would be either be grouped in string of 8 if Voltage limit allows or 2 strings 4 in parallel if the Max Current on the MPPT allows this.

I'm not sure I understand either, that's why I ask the question here. Nice to know I'm not the only one who doesn't understand their specs as put on their sheet. I'll contact the inverter manufacturer by email today and ask for a claification. Would it help if I put a link to their inverter, or is that not allowed? I don't want to undermine this forum's sponser.

 

[BentleyJ]

Links to datasheets, PV panel labels and all sorts of equipment are posted here all the time related to questions being asked. It just can't be for commercial purposes like a company trying to introduce or sell items. Member sales of used or new equipment is allowed as long as its a one time thing and not a commercial endeavor.

EDIT: I would be be very cautious about purchasing equipment from a vendor or manufacturer that can't even write a legible specification or datasheet.

 

[steveap]

Links to datasheets, PV panel labels and all sorts of equipment are posted here all the time related to questions being asked. It just can't be for commercial purposes like a company trying to introduce or sell items. Member sales of used or new equipment is allowed as long as its a one time thing and not a commercial endeavor.

EDIT: I would be be very cautious about purchasing equipment from a vendor or manufacturer that can't even write a legible specification or datasheet.

Hi, here is the link to the closest inverter they have listed on their web site:
https://drive.google.com/file/d/1GOQ1SqTU6VTHclDmK9KdCa3coNvVoBSI/view
It's the SB48-21 model - 21 Kw inverter with 48Kwh batteries included. Actually I'm planning to get their SB50-20 model - its an updated model with full bi-directional EV charging and increased capacities over their SB48-21 model. I like it because everything is together in one hurricane outdoor-rated enclosure. And its upgradable to 48Kw inverters and 100Kwh battery stack - all in the one enclosure. I think their quote is overpriced if I have them do the solar panel racking. They quoted I need about 34 400w panels but I think better are now available. So I would like to install the panels and racking myself and just have them install the inverter and wire everything together. I've been following them for about a year now, waiting for my settlement to come through so I can afford everything.
Your help in finding/using the best solar panels is appreciated.
Thank you.

 

[BentleyJ]

Looks like there is just an extra 0 on the PV input Watts value. If its actually 3,750W x 8 Inputs that would be 30kW of Solar which correlates well with a 20kW inverter output.

Under Battery branch breaker its listed as 75 VDC with a nominal battery voltage of 400 ??? Maybe another typo.

As far as solar panels, there are differing opinions of what is "best". Usually lowest cost for many folks but I always say the lowest priced product is never the best value. My definition of the best solar panel would be ones with the lowest long term degradation and a low Voltage/temp coefficient.

Something like an REC Alpha. 92% output after 25 years.