I too taught a solar in solar design, 45 years ago, was the state energy engineer and designed my near net zero home and office. When you add PVs to the north-facing side of the building, in the northern hemisphere, it's much cooler doing the installation than when you mount them on a proper side. But you still need to add the racking system, inverters and wiring. Where the vast majority of the PVs are mounted on the North-facing roof surface, so this project should have been like one of almost 50% of existing roofs that must be walked away from. This project screams that the install was quite clueless and damaging to the industry.
Original Message:
Sent: 9/3/2024 5:32:00 PM
From: Steven Hegedus
Subject: RE: Slar panel mounting
Hello Michael
I also was shocked when about 8 years ago I saw the first residential system in my neigborhood with both south and north facing modules. (I Live in Delaware). Then I thought about it. (I teach a class on solar technology applications). The cost breakdown for a residential system nowadays has the price of modules at less than 30% of the total installed price. So adding modules on the north makes sense since they incrementally add a small amount to the rest of the fixed costs. Adding 10% more cost but getting 60% more energy (see below) makes sense! As others have said, this new strategy was only possible due to the dramatic decrease in module pricing. And remember that rear facing modules see all the same diffuse hazy light that front modules see whcih is about 20-30% of the total over a year.
To verify this, I went to the NREL PVWatts calculator https://pvwatts.nrel.gov/pvwatts.php. I assumed a 1 kW ssytem facing S (180 deg azimuth) or N (0 deg azimuth). I assumed a slope of 30 degrees and calculated the output for a N and S facing systems in Dallas or Chicago. Results are:
Dallas: N- 1516 kWh, S-905 kWh or 40% less energy for the N facing array.
Chicago: N-1329 kWh, S-729 kWh or 45% less energy for N facing. This is expected since the farther N you are the less light on the rear.
If your slope is less than 30 degrees it gets much better especially the farther N you are. So that is why it is cost effective to put modules on the N.
I will say I am a little surprised that you ahve THREE times as many modules facing N than S. That is very unusual in my experience and in my opinion not a good deal for you given that 66% of your modules are getting much less energy than the remaining 33%. Which skews the payback against you.
Steve
------------------------------
Steven Hegedus
Professor and Senior Scientist
University of Delaware
Newark Delaware
------------------------------
Original Message:
Sent: 09-03-2024 01:43 PM
From: william fitch
Subject: Slar panel mounting
Without knowing were you are (Unless I missed it), a comment would be futile for the most part.
North side panel installation was not even a "thing", until they got so cheap it began to make sense, depending on the exact circumstances of the site. Low roof angles are pretty much required and generally you should be happy you get much of anything at all, given a true north install.
Latitudes under 20deg can fair not too badly. North of that gets progressively worse. North of 40, Winter will be in the toilet.
I would be happy and leave it alone, with a quality install. If its not broken, don't fix it.
------------------------------
william fitch
Owner
www.WeAreSolar.com
Original Message:
Sent: 09-02-2024 10:13 AM
From: MICHAEL MILLER
Subject: Slar panel mounting
I recently had 39 405 watt q-cell panels installed on my roof with IQ8 inverters. There are 10 panels on the south facing slope of my roof and 29 facing north. The panels facing south have consistently produced twice as much as those on the north slope - primarily I suppose due to the angle sloping away from the sun. I was wondering if there is an easy or recommended way to angle the north facing panels toward the sun without having to spend $50-$100 plus per panel. It seems most adjustable solutions Ive found online are geared towards RV type setups. The company that installed the panels did a great job all around but actively expressed no interest when I asked them about this. Perhaps it would be cheaper to just add more panels, but the difference in production of power between the north and south facing panels does seem quite high to me, as a south facing panel may produce 1.92 kWh in a day while a north facing one only produces 855wh. That is a comparison from yesterday via my Emphase app.
------------------------------
MICHAEL MILLER
------------------------------