Interesting data on module orientation

Desert Rat

I have a 1440 watt array that I installed back in 2003 consisting of twelve 120 watt Kyocera modules (remember when those were big panels?). The array is south facing and is tilted at 15 degrees (I'm at 29 degrees latitude). There are four series strings of three modules each.  I recently added a second array consisting of six SolarWorld 260 watt modules, for a total of 1560 watts. The new array is to provide power for a mini split air conditioner that I plan to install soon.  I faced three modules due east and three due west and each set is tilted at 30 degrees. They are wired in two series strings, three each. Each array runs through a Morningstar TS-MPPT-60 charge controller. I thought it would be interesting to monitor the two arrays and see which produced more watt-hours. I watched them today, and the new array with east and west facing modules produced significantly more watt-hours, even after subtracting the 8% for the slightly bigger size of the 1560 watt array. I quit watching at noon because the batteries had reached absorption in spite of running an electric heater as a diversion load. I had always believed that a south facing orientation is best for a fixed array, but this shows otherwise. Has anyone else observed this?

Johann

Panels will lose on power output with age while new panels may produce more for a few month up to one year before they settle in, so your new panels may outperform the older ones.
It may not be the result of orientation, but the result of comparing new panels vs. old panels.

westbranch

or since it is summer the arrays are getting more hours of exposure to sunlight

BB.

Weather/temperature also matter. Hot summer afternoons can drop output. So can summer storms or morning coastal marine layer.

-Bill

Desert Rat

Johann said:

the result of comparing new panels vs. old panels.

Good point; I hadn't considered that. I'm sure my 13 year old panels are not performing like new ones.

I think y'all are missing the point of my post. I have the unique opportunity to compare two different arrays under the exact same conditions. I installed the new array with east and west facing panels in order to get maximum power early in the morning and late afternoon to extend the run time of my mini split. Now I'm just wondering out loud if it would not be better for a person installing a new system to do "virtual tracking" like this instead of a strictly south facing array.

Dave Angelini

A person installing a new system really has to track the sun offgrid if they are cooling into the evening.
If you virtual track you just have to have the arrays to do it. A nice 2 - 5 KW tracker just makes it easier!

BB.

If you are doing Grid Tied Solar--It does depend on your rate plan. For me, I get "paid" more for afternoon production, so my South East facing array is less than optimum--But my home's orientation is what it is.

If you hare off grid--Having "more hours of sun/charging" per day--Yes, then facing arrays different directions (south east/south west) can be a big help. Lead Acid Battery bank needs something like 4-5 hour minimum of "decent sun" for moderate cycling. And, depending on where you live, having panels facing "not directly south" may not really reduce your overall harvest that much any way (and the later 2-4+ hours of charging are at a declining rate (absorb state). So, unless you have a "big afternoon load" (like water pumping, A/C, etc.), then the westerly facing array does not always need to be "huge".

We call having a "split array" "virtual tracking". And, it can be cheaper/less maintenance ($/kWH harvested) than a "real" mechanical dual axis tracker because the $/Watt of solar panels has become so "cheap".

-Bill

Dave Angelini

Adding on, anyone who lives offgrid would really not use a dual axis tracker as the goal for tracking is not max harvest but rather maximum hours. Much less maintenance on a single axis or horizontal axis tracker. A squirt of grease twice a year.

It scares me to admit that my first virtual tracker was in 1978 at Hewlett Packard. I think the panels were $20 per watt for a Telcom up/downlink up in Big Basin. 

Rain coming Bill?

Desert Rat

I have a 12W panel I bought in 1984. If I'm remembering correctly it cost me $280!

Desert Rat

BB. said:

We call having a "split array" "virtual tracking".
-Bill

Now I know you're not reading my posts; I used that term in my previous post. 

Dave Angelini

It probably did cost that much and there were not many choices then. The cat on your panels, is it hunting

Desert Rat

Dave Angelini said:

 The cat on your panels, is it hunting

Tracking

Dave Angelini

Very cool!  What part of the desert.  I was very close to being s rat south of Tucson! Very close!

BB.

Sorry--I try to read every post (as moderator)--And frequently I am doing that on my phone--Makes reading back up the thread a bit difficult.

But, no excuse--The term virtual tracker was used in several posts above mine.

-Bill

Desert Rat

Dave Angelini said:

 What part of the desert.

Chihuahuan Desert, near Big Bend National Park.  I'm 18 miles from the Mexican border.

Dave Angelini

Cool !  I have a client near Terlingua.  Nice country, are you getting all the rain that is near Houston?

Desert Rat

No rain; that's why it's a desert! It's amazing that they got all that rain over there, and 600 miles away we didn't get any. Truth be told, I did get .03 inches two days ago.

Dave Angelini

Desert Rat said:

No rain; that's why it's a desert! It's amazing that they got all that rain over there, and 600 miles away we didn't get any. Truth be told, I did get .03 inches two days ago.

It was Lyle Lovette who wrote the song,
 Ain't it funny how the way things go.