2MW agrivoltaic design - design constraints for inverter

[erk3]

Hello,

I am designing a 2MW solar array and am creating the electrical plan now. I was wondering if you could help with some advice on the inverter specs. I will include a photo of them. Since the output data is 72.3A, does this limit the input to the inverter to be less than 72.3A or is this per MPPT like the input data? I am arranging my arrays of panels and originally had 8 connected in parallel. 8 would be divided by the 4 MPPT's, which would make the total current per MPPT 27.38A which satisfies the 36A maximum per MPPT; however, since there are 4 MPPT's, then the total current going into the inverter would be 109.52A which is well above the 72.38A maximum output current. I am currently changing the design to have only 5 arrays entering the inverter (each array has a maximum current of 13.69A (short circuit) and 13.05A (maximum power current) to ensure the total current is less than 72.3A, but having less inverters would cut the cost of this drastically. Thank you for any help in advance!

 

[G00SE]

You need to look at the pv input data Operating current per MPPT is up to 36a. Times 4 MPPT.
144a total. (DC)
140a at say 700v=98,000w (spec says max PV is 78,000)

72.3a output = AC out

Also, 2MW array! WOW
What are you panel specs?

 

[timselectric]

2 MW
Are you planning on 20 Sol-Ark units?

 

[G00SE]

2 MW
Are you planning on 20 Sol-Ark units?

He does include a pic of a sol-ark 60kw 3 phase unit.
First id seen the spec sheet…impressive

 

[timselectric]

He does include a pic of a sol-ark 60kw 3 phase unit.
First id seen the spec sheet…impressive

They are only capable of 78 kw PV each.

 

[G00SE]

They are only capable of 78 kw PV each.

True. Even 2mwh is a far cry with one.
Heck, 400kw in panels is still 1000-400w panels right?

 

[timselectric]

2 MW is grid scale.

 

[shadowmaker]

Hello,

I am designing a 2MW solar array and am creating the electrical plan now. I was wondering if you could help with some advice on the inverter specs. I will include a photo of them. Since the output data is 72.3A, does this limit the input to the inverter to be less than 72.3A or is this per MPPT like the input data? I am arranging my arrays of panels and originally had 8 connected in parallel. 8 would be divided by the 4 MPPT's, which would make the total current per MPPT 27.38A which satisfies the 36A maximum per MPPT; however, since there are 4 MPPT's, then the total current going into the inverter would be 109.52A which is well above the 72.38A maximum output current. I am currently changing the design to have only 5 arrays entering the inverter (each array has a maximum current of 13.69A (short circuit) and 13.05A (maximum power current) to ensure the total current is less than 72.3A, but having less inverters would cut the cost of this drastically. Thank you for any help in advance!

It's a hybrid inverter so going to have batteries also? In that case 5x Sunsynk (=Deye=Sol-Ark) 1MWh battery containers each having 400kW inverter capacity. Cost about 100k per unit, but includes fully lined container with build-in climate control, fire suppression system, EMS and alarm. 500k gets you 2MW inverter capacity and 5MWh battery.

 

[erk3]

I am reading through the comments and will try to respond today as time allows. Here is my most recent plan drawn out. I have 72 of the string inverters since the max current out is 72.3A which is why I have a maximum of 5 PV arrays in parallel entering the inverter. I am struggling to find a proper electrical distribution panel system (circuit breakers, etc.) that the power from the inverters can enter, and also need to find a transformer to bring the voltage up to reach the requirements of the grid which I am struggling to properly identify. Thank you again in advance, and i'm sorry not to respond to all posts immediately. I truly do not know all those answers since I am still learning a bit about this whole process.

 

[Brucey]

Have you already got an interconnection agreement setup for this?

 

[740GLE]

You looking to upgrade your off grid snow cabin so you can keep your battle born bank charged year round without a standby generator?

207kWh System... In 12V??? 😬

Holy cow, where do we start... $149,000 of batteries... are they unaware of other options on the market today? 12V batteries in series? Yikes...

diysolarforum.com

At 4-6 acres per MW, you got your work ahead of you.

 

[AntronX]

Since the output data is 72.3A, does this limit the input to the inverter to be less than 72.3A or is this per MPPT like the input data?

No. Inverter converts PV to different voltage and 3 phase. Calculate by power, not current. You can do 16 * 550w panels in series * 2 parallel per MPPT input = 672V * 26A = 17.47kW * 4 MPPT inputs = 69.9kW PV STC total from 128 panels per inverter. Open circuit voltage at coldest temp will be 16 * 56.5V = 904V < 1000V max Voc.

 

[erk3]

No. Inverter converts PV to different voltage and 3 phase. Calculate by power, not current. You can do 16 * 550w panels in series * 2 parallel per MPPT input = 672V * 26A = 17.47kW * 4 MPPT inputs = 69.9kW PV STC total from 128 panels per inverter. Open circuit voltage at coldest temp will be 16 * 56.5V = 904V < 1000V max Voc.

Thank you that is helpful! This is for Grid sell which the inverter changes the maximum power to be 60,000W, so I have a maximum of 14 panels in series = 14*550W = 7,700Wdc * 2 parallel per MPPT * 4 MPPT per inverter = 61,600Wdc, so I can tweak this a bit to get under the 60,000, only need to take away 4 panels per inverter. Thank you, this was my original plan, but I changed it per the output power from the inverter.

 

[erk3]

Thank you that is helpful! This is for Grid sell which the inverter changes the maximum power to be 60,000W, so I have a maximum of 14 panels in series = 14*550W = 7,700Wdc * 2 parallel per MPPT * 4 MPPT per inverter = 61,600Wdc, so I can tweak this a bit to get under the 60,000, only need to take away 4 panels per inverter. Thank you, this was my original plan, but I changed it per the output power from the inverter.

output current from the inverter***

 

[400bird]

Based on what I'm reading, you're out of your league.

At grid scale, it's all about cost/watt.
There's no purpose is spending extra in a battery inverter with integrated grid pass through relays and not buying batteries or having a purpose for the grid pass through.
Also, it's common practice to over panel by something around 25% (also called DC to AC ratio)
So, 61kW on a 60kW inverter is likely less than industry standard at that scale.

Depending on how cold it gets and the temperature compensation numbers, you'd probably be best off doing 15s or 16s to get the ratio up.

I'd expect something like this at 255kW is a much more practical inverter. Don't take this as a recommendation, just an example.

SOLECTRIA XGI 1500-250 Series Inverters - Yaskawa – Solectria Solar

Yaskawa Solectria Solar is pleased to introduce its most powerful XGI 1500 inverters, with the XGI 1500-250 models at 600 Vac, and the XGI 1500-200 models for 4

www.solectria.com

 

[shadowmaker]

Based on what I'm reading, you're out of your league.

At grid scale, it's all about cost/watt.
There's no purpose is spending extra in a battery inverter with integrated grid pass through relays and not buying batteries or having a purpose for the grid pass through.
Also, it's common practice to over panel by something around 25% (also called DC to AC ratio)
So, 61kW on a 60kW inverter is likely less than industry standard at that scale.

Depending on how cold it gets and the temperature compensation numbers, you'd probably be best off doing 15s or 16s to get the ratio up.

I'd expect something like this at 255kW is a much more practical inverter. Don't take this as a recommendation, just an example.

SOLECTRIA XGI 1500-250 Series Inverters - Yaskawa – Solectria Solar

Yaskawa Solectria Solar is pleased to introduce its most powerful XGI 1500 inverters, with the XGI 1500-250 models at 600 Vac, and the XGI 1500-200 models for 4

www.solectria.com

THIS.

If there's not going to be any batteries why pay 5-10 times more for Sol-Ark 60K hybrid inverters if only grid tied inverting is needed?

 

[erk3]

THIS.

If there's not going to be any batteries why pay 5-10 times more for Sol-Ark 60K hybrid inverters if only grid tied inverting is needed?

Thank you for the information. I was pointed in this direction when looking for string inverters. Do you have any recommendations for cheaper string inverters? I will look into this.

 

[erk3]

Based on what I'm reading, you're out of your league.

At grid scale, it's all about cost/watt.
There's no purpose is spending extra in a battery inverter with integrated grid pass through relays and not buying batteries or having a purpose for the grid pass through.
Also, it's common practice to over panel by something around 25% (also called DC to AC ratio)
So, 61kW on a 60kW inverter is likely less than industry standard at that scale.

Depending on how cold it gets and the temperature compensation numbers, you'd probably be best off doing 15s or 16s to get the ratio up.

I'd expect something like this at 255kW is a much more practical inverter. Don't take this as a recommendation, just an example.

SOLECTRIA XGI 1500-250 Series Inverters - Yaskawa – Solectria Solar

Yaskawa Solectria Solar is pleased to introduce its most powerful XGI 1500 inverters, with the XGI 1500-250 models at 600 Vac, and the XGI 1500-200 models for 4

www.solectria.com

Thank you I will look into this!

 

[shadowmaker]

Thank you for the information. I was pointed in this direction when looking for string inverters. Do you have any recommendations for cheaper string inverters? I will look into this.

I know nothing about grid scale solar and very little about solar overall. I do know that both my hybrid Deye12K and US market only Sol-Ark15K have about the same specs and both are manufactured by Deye (China). Deye12K is 2450$ (all included) and S-A15K is ~7000$ (don't know if you still need to pay postage or something) so about three times more while being almost identical. Then I have two Bluesun15K (China also) grid tied inverters (=no battery/storage possible) which have 3kW more inverting and PV capacity but costs only about 950$/pc.

For 2MW PV you'd need about 30pc S-A60K units and they seem to be around 19-20k$/pc so assumed getting those cheap with only 15k$/pc would still be 450k$. That's insane. Even more if you aren't planning any battery storage (=no need for hybrid inverting). Using Bluesun15Ks you'd need 133pcs so it would cost only about 126k$ and they'd probably even give you a nice discount from the price I paid.

But like @400bird said there are utility scale grid tied inverters which are more robust and probably give you more bang for your buck. Playing with more than hundred small Bluesuns or alike would be utterly stupid.

In here our selling prices change every hour depending how much grid scale hydro, wind, solar, nuclear, etc. power is predicted to be available. We get next day predictions (=spot prices) at 14.00 every day. Having hybrid inverters and battery storage means you can sell your PV production when it is most profitable and also charge your batteries from grid when spot prices are low and sell it away when prices are high.

 

[timselectric]

You'll have plenty of time to decide on what inverter to use.
You can think about it while installing the 3,000 solar panels.