Would an east facing array outperform a west facing array?

[sunshine_eggo]

Another thing I'm thinking about and i don't know how this works exactly but Ive seen vids that suggest if you are using power directly from pv it's more efficient than storing it in the battery first and then using it later

Battery charging isn't 100% efficient. Lead acid can be as low as 85% average, and it's even worse in the absorption phase.

LFP charging is pretty darn efficient.

So what I'm thinking is that with a west facing array ,for example, the power is available later in the day when it's needed so it could be pulling straight from pv instead of battery, say for example at 6pm in the summer when I imagine a south facing array is already done.
This would mean some efficiency gains vs a south array correct?

Theoretically, but not a lot.

Now, where I'm confused,or skeptical is this. How can battery inverter consume directly from the pv(charge controller) when the job of the charge controller is to, wait for it, charge the battery?

An inverter inverts DC to AC. It's a system. Current is either going into or out of the DC system or in equilibrium.

It's makes no sense because to my thinking the charge controller is always charging the battery and the inverter will always pull from battery, no?

Load = battery voltage dip
battery voltage dip = charger supplies more current to maintain battery voltage.

Net result = MPPT is feeding load directly and providing "float current" to the battery.

Victron MPPT run without battery once battery voltage has been established. I was shutting my system down and not really thinking about it in detail. It was in the evening, so not a lot of juice coming in. Loads were < 200W, so order didn't matter in my head. When I turned the battery switch off, I had a stupefying moment where the system was still running with the battery completely isolated. Occurred to me the system was being powered directly by the MPPT... forgot about that feature.

 

[timselectric]

Sometimes our choices are limited.
I have a hill to my south. And my roof is East/ West.
I will be adding a South facing ground mount array, hopefully next year.
I need it for winter production. But I have to clear some trees first. As I need to get it far away from the hill.

 

[1201]

Some, yes.

in an AIO, the SCC sends power to the high voltage DC bus. The inverter pulls its power from the high voltage DC bus. It's more efficient to not go into the battery and back out.
In a separate module system. The SCC sends its power to the low voltage DC bus bars. (If installed) and the inverter pulls its power from there.
Still more efficient than going into and back out of the battery.
But there are more conversion losses.

Basically
Avoiding the charging and discharging losses is always more efficient.

ahh. the old high voltage dc bus. Thanks for the education.

so even with a separate charge controller the inverter can pull directly from pv without the battery conversion losses or is it always pulling from battery?

 

[1201]

I have a one string 3.6kW going in now at 165°/60° angled and a two string 7.2kW at 215°/60° angled array- just finished. Let’s just say, REC405 (215°) panels out performed my QCells430 (180°/45° angled) from noon on yesterday after the sun popped out. The steeper angle with the 405’s does not do well in overcast conditions like yesterday morning compared to the 430’s. I will not go with due east or west, because I have plenty of power when the sun is that far north in the sky. I need wintertime power for heat pumps. I also have a 200’ tall hill to my east.

I like southwest array for cooking dinner. My SolArk12K’s is 2% more efficient when going from PV to A/C output vs going into battery then pulling back out later.

hi. how do you calculate the efficiency and figure out that pulling from pv is 2% more efficient than from battery? thanks!

 

[1201]

Theoretically, but not a lot.

ok, so in practice it wont overcome the lower production of facing the array somewhere other than directly south.

An inverter inverts DC to AC. It's a system. Current is either going into or out of the DC system or in equilibrium.



Load = battery voltage dip
battery voltage dip = charger supplies more current to maintain battery voltage.

Net result = MPPT is feeding load directly and providing "float current" to the battery.

hmm. It makes sense but i'll have to think about this a little more.

Victron MPPT run without battery once battery voltage has been established. I was shutting my system down and not really thinking about it in detail. It was in the evening, so not a lot of juice coming in. Loads were < 200W, so order didn't matter in my head. When I turned the battery switch off, I had a stupefying moment where the system was still running with the battery completely isolated. Occurred to me the system was being powered directly by the MPPT... forgot about that feature.

fascinating.

 

[sunshine_eggo]

Some, yes.

in an AIO, the SCC sends power to the high voltage DC bus. The inverter pulls its power from the high voltage DC bus. It's more efficient to not go into the battery and back out.
In a separate module system. The SCC sends its power to the low voltage DC bus bars. (If installed) and the inverter pulls its power from there.
Still more efficient than going into and back out of the battery.
But there are more conversion losses.

Need an education here...

Let's say the PV is disconnected. If the inverter pulls from the high voltage DC bus, is there a DC-DC converter to step up the low voltage DC to high voltage?

 

[efficientPV]

I figure 12 hours of night use and a couple in the morning is a long time to wait before a south and west array start producing. My refrigerator doesn't work at night so it has to recover first thing in the morning. I'm about as close as you can get to using power directly from the panels. While not a typical day, refrigerator has recovered, hot water is up to 60C by 10am when I start the dishwasher (heating element runs from array DC) and have done three loads of laundry (direct from array power with hot water from PV) by noon with battery fully charged. It has to be a good day for laundry and started in the morning because we line dry. East facing array (1/3 of total panels) in my location produces more power than the rest of the system.

It is always site dependent and based on lifestyle. We don't have commitments like work which prevent us from doing things when the sun is shining. Dishwasher has a start delay feature making it easy to run when we are away, and the hot water gets up to temperature. Remarkably low battery requirements when you get away from the I want it now mentality. On a nice day I get nearly full rated power from the east array for several hours. South facing panels is just a dated way of thinking from when panels were expensive and batteries were cheap.

 

[timselectric]

so even with a separate charge controller the inverter can pull directly from pv without the battery conversion losses

Yes

 

[timselectric]

Need an education here...

Let's say the PV is disconnected. If the inverter pulls from the high voltage DC bus, is there a DC-DC converter to step up the low voltage DC to high voltage?

Yes
It's a bidirectional DC to DC converter.

 

[JWLV]

Victron MPPT run without battery once battery voltage has been established. I was shutting my system down and not really thinking about it in detail. It was in the evening, so not a lot of juice coming in. Loads were < 200W, so order didn't matter in my head. When I turned the battery switch off, I had a stupefying moment where the system was still running with the battery completely isolated. Occurred to me the system was being powered directly by the MPPT... forgot about that feature.

LOL I had a similar moment too. I was relieved that I didn't blow anything up. I thought about putting up a checklist with 1, 2, 3 signs in each shutoff location to make sure I don't make any mistakes in the future. Also had a different moment where I thought something was shut off when it wasn't. Sparks were flying that day with 25kwh of battery.

 

[1201]

Yes
It's a bidirectional DC to DC converter.

do you have any information on the efficiency of these dc to dc converters in the budget AIOs?

 

[sunshine_eggo]

LOL I had a similar moment too. I was relieved that I didn't blow anything up. I thought about putting up a checklist with 1, 2, 3 signs in each shutoff location to make sure I don't make any mistakes in the future. Also had a different moment where I thought something was shut off when it wasn't. Sparks were flying that day with 25kwh of battery.

Yikes! I feel your pain. ?

 

[RV10flyer]

hi. how do you calculate the efficiency and figure out that pulling from pv is 2% more efficient than from battery? thanks!

 

[RV10flyer]

LOL I had a similar moment too. I was relieved that I didn't blow anything up. I thought about putting up a checklist with 1, 2, 3 signs in each shutoff location to make sure I don't make any mistakes in the future. Also had a different moment where I thought something was shut off when it wasn't. Sparks were flying that day with 25kwh of battery.

We’ve all been there ?, or will be there.

 

[timselectric]

do you have any information on the efficiency of these dc to dc converters in the budget AIOs?

Sorry, I don't.

 

[45North]

East and West each have their advantages. But panels are cheap now so do both.

 

[Crowz]

My system makes more power after noon here. No clue why but it seems to favor westward so I adjusted my panels to a slight westward angle vs right on east/west aligned. Its not a huge difference but it shows up. Might be an Alabama thing.

The panels may have dew on them in the morning hours affecting them.

 

[1201]

East and West each have their advantages. But panels are cheap now so do both.

True. The mounting , wiring and charge controllers cost more than the panels themselves

 

[cs1234]

True. The mounting , wiring and charge controllers cost more than the panels themselves

So much of it is the mounting. It's unreal !

 

[cs1234]

East and West each have their advantages. But panels are cheap now so do both.

Too bad single axis trackers cost so much / aren't that common. I like the ones I've seen on here that work like a little rotisserie chicken. I forgot who here on the forum made their own little ground mounted single axis tracker with a couple small solar panels with diodes and some little servos or something to move it back and forth based on which small panel was outputting the higher voltage. An inexpensive commercial design of that would be sweet!