Need inverter sizing advise using Bi-Facial PV panels

D0T-C0M

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I got a really good deal for a pallet of 35 CanadianSolar-BiKu_CS3U-MB-AG 375W BiFacial Panels. I'm paying $0.41/watt which in Canada is really really cheap. I am really excited with these new panels because these panels should produce more power in the winter due to the snow cover reflecting a lot of the light thus taking advantage of the Bi-Facial aspect of these panels. This should in theory, offset the fact that we only get about 2.5 sun hours in the winter.

I plan to eventually work myself up to a 10k-12k Watts of PV panels with a 48v Battery backup (560Ah) but for my first leg of the project I want to install ~16 PV panels for about 6000w hybrid grid tied without batteries for now but want to option to add batteries later in the future.

The issue I have is with 6000W BiFacial panels they can produce up to 7600W. This means I have to oversize my inverter to accomadate for this but inverters aren't cheap and I'm trying to figure out if its worth it. Will these BiFacial panels really produce 7600w in real world conditions? Anyone here have real world summer(grass reflected light) and winter data(snow reflected light) in northern areas using BiFacial PV panels (Field mounted not roof mounted)? Are there inverters that can handle the 30% max power variance that doesn't cost an arm and a leg? Should I lower the wattage of my solar array to 5000W? Or should I find regular panels that have a constant max wattage?

Also looking for 240VAC Hybrid grid tie inverter suggestions. So many different types.
 
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SolarQueen

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I'm assuming you are doing a ground or pole mount to take advantage of the bifacial. A simple roof mount won't do much better than single facials.

Trying to install hybrid without batteries for now limits your options of inverters. SolArk can do this. They have a 12kW inverter with a max PV input of 13kW. Canadian Solar recommends planning on up to 30% increase from their bifacials. So technically, you can have up to 10kW of the bifacials on it. Maybe you could sell 8 or 9 panels from the pallet to help offset the price of the inverter ($6850).
 

Hedges

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You can lower the peak wattage and extend the hours of operation (at least for long summer days) by orienting some strings of PV panels towards morning sun, some towards afternoon. With a 90 degree angle between them, to the first order this will reduce peak to 0.7 times as much. There, I just lowered your wattage to 5kW.

You can install a grid-tie inverter to start, rather than a hybrid. That will only export to grid, not provide power during grid failures.
Some (current SMA Sunny Island models) have "Secure Power" outlet, separate switch and outlet to give you up to 2kW of 120VAC during grid failure.

Later you can add a battery inverter. Either Sunny Island (which I have) for 48V battery, or Sunny Boy Storage for 400V battery.

Something to look for in battery inverters, whether SMA, SolArk or others, is expandability. Can you grow it to be a whole-house backup in the future by adding more? Several brands/models allow this, but some do not.

Going batteryless to start is a good idea to be economical. A battery/inverter setup can cost as much or more than a PV/GT inverter setup.
I think you can get a Sunny Boy GT inverter (models range from 3kW to 7.7 kW) for around $2000 current model, close to $1000 prior model. Difference is features that might be required for permits and grid tie. The new features may only be required in some markets such as California, and not in yours.
 
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D0T-C0M

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Hedges Thank you so much for the great information. I am intrigued in the way you suggested orienting the panels. I'll definitely look into that. With the BiFacial panels I might recoup some of the power lost from the reflected light if the panels are 90 degrees apart.

As far as the inverters you discussed I was just looking into the sunny boy line and saw that they had that 2000w 120v output but I need to run my 240v well pump so i need at least a 240v backup feed. The MPPSolar Hybrid V2 5KW seems very promising. It has 450vdc max pv input and It can be run batteryless when only using one inverter. I'd have to start with 5kw of panels but could double it in phase2 of my project. You only need batteries if you stack multiple units. I can't seem to find any canadian suppliers for MPPSolar inverters in Canada which is disappointing. The SolArk 12k all in one is pretty much exactly what I would want but its almost $10kCAN with tax
 

Hedges

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Well pump with induction motor - what are the ratings? You'll need an inverter that can provide surge current to 5x the nameplate, for about a second or less. The Sunny Boy secure power might start a 400W 120V fridge or window air conditioner. To power the pump you'll need a pretty good inverter, probably "low frequency" (transformer based and heavy) rather than "high frequency" (no transformer, light weight)

You will probably need batteries for the surge current needed to start the pump, unless you have more than 10 kW of PV panels and only try to start the pump in full sun.
I used a 100 Ah 48V AGM battery initially ($1200), now have 400 Ah.

What I have are Sunny Boys coupled with Sunny Island 6kW 120V battery inverters. I have them series/parallel connected for 120/240V split-phase. A single Sunny Island would probably run your pump if coupled to a transformer to make 240V. It delivers 11 kW surge for 5 seconds.

Besides Sunny Island, there are several other good brand low-frequency inverters, many of which can be stacked for more power or split-phase, some split phase in a single unit. Schneider/Trace, Outback, Victron for instance
 

D0T-C0M

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its a 230v 3/4HP submersivable pump so it draws like 6-7amps. Also in regards to the battery bank I was thinking of making my own out of the 280Ah LiFePO4 cells from china that everyone is raving about.
 

Hedges

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Figure 30 to 35A surge, 8 kW or so. Most low-frequency inverters rated 4kW or above would have a surge rating to cover that.
A transformer able to put 4 kW on a second 120V winding from a primary 120V winding would let a 120V inverter drive it. I'm not sure what (smaller) continuous rating is needed from a transformer to deliver 4 kW surge.

I posted links to some transformers I saw recently that would probably do it:


Those DIY lithium cells have become quite inexpensive, looks like you should be able to make a battery with 5000+ deep cycle life for same or fewer dollars than AGM with 800 deep cycles. Whether its worthwhile depends on how big a bank you want (how big the savings) and your interest in the project. At some small size, off the shelf AGM could be the way to go. Mine is probably larger than the crossover point, but I don't anticipate many cycles.
 
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