My 44kW vertical and bifacial set in Finland.

[houseofancients]

Got Deye12K to my FIL and he is going to connect 6,6kWp to MPPT1 and his old 3kWp array to MPPT2. Now he wants to add more panels to MPPT2 with 180 degree difference in azimuth (adjacent slope in his roof) by paralleling strings and wants to use 3-way split with MC4 connectors including diodes in both strings leads. This is supposed to prevent strings fighting each others when other is in sun and the other isn't. I told him it's a bad idea, but then what would I know...

Anyone?

Well.. let us call it..

Less than optimal

 

[MattiFin]

Got Deye12K to my FIL and he is going to connect 6,6kWp to MPPT1 and his old 3kWp array to MPPT2. Now he wants to add more panels to MPPT2 with 180 degree difference in azimuth (adjacent slope in his roof) by paralleling strings and wants to use 3-way split with MC4 connectors including diodes in both strings leads. This is supposed to prevent strings fighting each others when other is in sun and the other isn't. I told him it's a bad idea, but then what would I know...

Anyone?

Parallei strings work just fine both in theory and practice. No need for diodes.
Just need to match the string voltages reasonably close (10-20%) to each other, mismatch in string voltage is lost energy.

 

[CostOptimizer]

Given this production per year, in how many years would you get your investment back ?

 

[400bird]

270kWh today. Almost perfect day.

Backside production at 21.00.
View attachment 212474

That's pretty neat, and lots of energy!
Do you see production fall off in the morning at evening as the Sun is directly in line with the frames? Like due east or west?

 

[shadowmaker]

Parallei strings work just fine both in theory and practice. No need for diodes.
Just need to match the string voltages reasonably close (10-20%) to each other, mismatch in string voltage is lost energy.

Even while other string is totally shaded and other one is having full sun?

Would be fun to test without and with diodes though as I understood those 3-way splitters are cheap.

 

[MattiFin]

Even while other string is totally shaded and other one is having full sun?

Would be fun to test without and with diodes though as I understood those 3-way splitters are cheap.

Yeah even when one string would be in pitch black cave and another in full sunlight.
Solar panel is a string of diodes connected in series. It will draw very little to no current if the (externally applied) voltage is lower than the diode string voltage.

 

[shadowmaker]

Given this production per year, in how many years would you get your investment back ?

As I DIYed everything my cost with GTIs (4x Bluesun15K) only and no battery would have been ~0,85e/W. This was my initial plan. ROI maybe 3-5 years?

Then I got a 30kWh (C/5 rating) lead acid battery and 7,2kWh UPS for free and found unused 3kWh UPS for 600e and decided to sell two GTIs and get two hybrid Deye12Ks instead plus bought some LFP too. With lead, 75kWh LFP batteries and 2x Deye12K it came ~1,35e/W. With batteries/hybrid inverters it gets more expensive, but I can also manage my self usage better and even sometimes grid charge cheap and then sell back to grid with decent profit when spot prices are up. ROI maybe 5-7 years?

At first there were economics involved, but now not so much anymore. It'd be fun to be self sufficient someday. Not off-grid style, but to survive few weeks even few moths grid outage in case of emergency. Our east neighbor has leader with big time Napoleon syndrome so anything can happen.

 

[shadowmaker]

That's pretty neat, and lots of energy!
Do you see production fall off in the morning at evening as the Sun is directly in line with the frames? Like due east or west?

My array has 135 azimuth so in mornings it works really nice. It's the afternoon around 15.30-18.30 when there's a huge dip in production due to sun angle (see post #187). This is why I'm going to install 15,4kWp monopanels on nearby shed roof with 235 azimuth. Hopefully it'll help with afternoon/evening production.

 

[OffGridForGood]

I'm going to install 15,4kWp monopanels on nearby shed roof with 235 azimuth

15,4 + 44 = 59,4kWp PV

 

[400bird]

My array has 135 azimuth so in mornings it works really nice. It's the afternoon around 15.30-18.30 when there's a huge dip in production due to sun angle (see post #187). This is why I'm going to install 15,4kWp monopanels on nearby shed roof with 235 azimuth. Hopefully it'll help with afternoon/evening production.

And here I thought I had been reading along the entire time. I missed that post entirely.

Do you have net metering or are you hurting for power when the sun lines up with the array? Sorry if you already answered this too.

 

[shadowmaker]

And here I thought I had been reading along the entire time. I missed that post entirely.

Do you have net metering or are you hurting for power when the sun lines up with the array? Sorry if you already answered this too.

No net metering as we have spot prices here. One can choose to buy with spot or fixed prices but selling uses always spot. I have fixed price which is ~12c/kWh all included this year. For next year I need to make a new deal. Just as I'm typing this my system is backfeeding ~40kW as spot price is 30-50c/kWh. I'm hoping to make ~60e this morning before spot prices go back to normal.

New panels are meant to help with afternoon dip in production as it is very normal here to have bad weather morning and nice sunny weather afternoon or vice versa. I don't need more production (well in winter I could use much more), but I would like some every day.

 

[shadowmaker]

Can't see how this is even possible. Both Deyes making little over 8,5kW PV so combined ~17kW but still charging 7,13kW + 12,93kW = ~20kW to my batteries. Work mode is Zero Export to CT on both and no grid charge allowed. I have no shunt on my batts as Deye has some internal way to calculate things (P=UI). It did this at least 10min while I was trying to figure it out but probably much longer. Checked LFP rack batts individual screens and calculated that they were taking ~240A combined which is ~13kW so it has to be correct. Didn't have my clamp meter close so couldn't check actual currents. Just wondering where did that extra ~3kW charge came from??? No AC coupling so both Bluesun15Ks taking care of my loads and pushing ~7,5kW to grid so ignore right side of the screen. Have never seen this kind of behavior before although I'd love to have extra 3kW charge power out of thin air if possible.