Would an east facing array outperform a west facing array?

[1201]

So on paper east and west should have the same production correct? But like the heat gain through a window, east and west should have the same heat gain but west ends up having more because of higher ambient temperature.

So, since temperatures are lower in the morning(summer time) does it mean east facing panels would be cooler and produce more than west facing panels?

 

[timselectric]

So on paper east and west should have the same production correct? But like the heat gain through a window, east and west should have the same heat gain but west ends up having more because of higher ambient temperature.

So, since temperatures are lower in the morning(summer time) does it mean east facing panels would be cooler and produce more than west facing panels?

Yes
According to my East and West facing arrays.

 

[1201]

Strangely enough pvwatts says the West facing array will slightly outperform the east facing array??

 

[1201]

Yes
According to my East and West facing arrays.

What kind of improvement do you see?

 

[sunshine_eggo]

While ambient plays a role, my gut says that the 80% of sunlight that gets converted into heat and raising the cell temperature is going to have a bigger influence. Yes, I think morning will outperform evening by a bit, but it doesn't seem like a ton.

Hmmm...I just checked some older models I had saved from PVWatts at my location.

Annual production of a 5kW E array: 8.85MWh
Annual production of a 5kW w array: 8.28MWh

About 7% better

 

[timselectric]

What kind of improvement do you see?

10% to 15% more from the East.
But I assume that it also depends on the location.

 

[1201]

10% to 15% more from the East.
But I assume that it also depends on the location.

That's huge!

 

[1201]

While ambient plays a role, my gut says that the 80% of sunlight that gets converted into heat and raising the cell temperature is going to have a bigger influence. Yes, I think morning will outperform evening by a bit, but it doesn't seem like a ton.

Hmmm...I just checked some older models I had saved from PVWatts at my location.

Annual production of a 5kW E array: 8.85MWh
Annual production of a 5kW w array: 8.28MWh

About 7% better

Hmm. I wonder why it says West is better in my location. I wouldn't imagine it would be location dependent but it appears it is. I have a lot to learn

 

[cdherman]

PVWatts has information about cloud cover. Morning clouds in many locations occur and then burn off in the afternoon. Just a guess on my part, but valid I think.

 

[sunshine_eggo]

Hmm. I wonder why it says West is better in my location. I wouldn't imagine it would be location dependent but it appears it is. I have a lot to learn

PVWatts factors in 30 year average weather. I checked June 30th, and W was higher on that day.

 

[1201]

PVWatts has information about cloud cover. Morning clouds in many locations occur and then burn off in the afternoon. Just a guess on my part, but valid I think.

Ahh. I didn't even know about cloud cover. Very nice. Thanks for that bit of info

 

[sunshine_eggo]

While ambient plays a role, my gut says that the 80% of sunlight that gets converted into heat and raising the cell temperature is going to have a bigger influence. Yes, I think morning will outperform evening by a bit, but it doesn't seem like a ton.

Hmmm...I just checked some older models I had saved from PVWatts at my location.

Annual production of a 5kW E array: 8.85MWh
Annual production of a 5kW w array: 8.28MWh

About 7% better

While those models were based on theoretical due E and due W arrays @ latitude tilt, my actual array is set to 165° vs. 180° at 29° tilt due to anecdotal claims that afternoon clouds inhibit afternoon production, so you get a little more daily juice favoring East.

Unfortunately, it's not true according to PVWatts. My 165° array produces 5.402MWh vs. 5.416MWh for a 180° array. During the summer months, I can produce up to 8kWh additional per month.

 

[efficientPV]

The real practical consideration is when do you need the power and that is usually in the morning. I have an east facing array and my system has totally recovered by 10am. This results in needing less battery. Don't know how this matters here. Majority buy batteries like women buy shoes.

 

[JWLV]

Keep in mind that a nearly empty battery charges faster than a nearly full battery. So if your battery has been drained overnight by whatever you use at night, it would draw more power and charge faster the next morning as opposed to charging all day and then top off at the end of the day.

 

[1201]

The real practical consideration is when do you need the power and that is usually in the morning. I have an east facing array and my system has totally recovered by 10am. This results in needing less battery. Don't know how this matters here. Majority buy batteries like women buy shoes.

Hmm that's interesting.

Now in Texas where I live, we need that power from noon till 7pm so west might be best but I do like the idea of charging the batteries up early

 

[timselectric]

Something else to keep in mind.
Storms usually come in the afternoon/ evening.
Mornings are more often clear skies, than evenings are.
There are a lot of variables to consider.
That's why I have both, East and West arrays.

 

[1201]

Something else to keep in mind.
Storms usually come in the afternoon/ evening.
Mornings are more often clear skies, than evenings are.
There are a lot of variables to consider.
That's why I have both, East and West arrays.

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

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?

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?

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?

 

[hwy17]

Weather dependent. Some places have clear skies in the morning, I get clear skies in the afternoon.

PVWatts is really an amazing tool, most of all because it includes these weather factors.

 

[RV10flyer]

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.

 

[timselectric]

This would mean some efficiency gains vs a south array correct?

Some, yes.

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?

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.