Hi all, I'm looking for some feedback on the solar design we just received from Tesla.
We received our system design from Tesla today. Overall it looks pretty standard with a few exceptions that I was hoping to get some feedback on.
Our system is a 8.16kW system (Tesla’s medium size) consisting of 24 Hanwa Q-Cell panels, one Powerwall+ integrated battery & string inverter, and a Gateway2. As shown below, 20 of the 24 panels are in a 4x5 array on the east facing roof, and 4 panels form a 2x2 array on the west facing roof. We have a little shade on the east facing roof, mostly from two chimneys. The west facing roof, on the other hand, is almost completely shaded by trees from about noon onwards during the summer months.
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So if I'm reading the schematics below correctly, the panels will be connected in two strings:
- Two parallel strings of 10 panels each going into one MPPT (MP 1); these are on the front (east) roof of our house.
- A single string of 4 panels going into a second MPPT (MP 2); this is on the rear (west) roof.
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So here are my questions/concerns.
- I am concerned that the 4 panels on MP 2 won’t reach the minimum voltage of the inverter very often due to the shade. To address this, my thinking was to either (1) add TWO more panels to this array, bringing the total to six. Then at least the string should get above V_min more often; mostly in the winter months when the leaves are off the trees. Or (2), get rid of the 4 panels and just go with the 20 on the east roof. I’m leaning towards (1) because this will give us some more power, especially in winter months. I also know it is difficult to try to add panels later on.
- I’m wondering why the 20 panels are strung into two parallel strings of 10 panels each on MP 1, instead of the two strings each being on a separate MPPT? I believe the string inverter supports 4 MPPTs. So the only reason I can think of is to reduce the number of conductors coming off the roof to the inverter in the basement. Would there be any other reason for doing this?
I’ve asked the above questions to my advisor at Tesla, but in the meantime I was hoping for some unbiased feedbac from this group.
Thanks in advance for any advice.