I think there is a bug in the losses calculator that SAM is using for detailed residential distributed Photovoltaic analysis.
I have attached a pdf of the sankey chart that SAM generated, it is called "Losses.pdf". I've also attached a pdf of what my excel calculations show based on the loss data shown in the sankey chart called "sam question.pdf"
I can't for the life of me figure out how the loss percentages lead to the kWh stipulated in the diagram.
For example, Nominal DC energy is listed as 4394 kWh.
There are 4 losses listed under nominal DC energy:
snow 3.008%
module 1.387 %
diodes and connections .498%
DC wiring .498%
these losses add up to 5.391%, which would reduce the make the net DC energy equal to 94.609% of 4394 kWh, or 4157.12 kWh. The number that SAM spits out for net DC energy however is 3526 kWh, or 82% of the nominal DC energy figure. See my excel
Can anyone explain to me why this is so far off?
My method works for getting to gross AC energy from net DC energy, and for getting to annual energy from gross ac energy (see "sam question.pdf"). Why doesn't this work when going from nominal DC energy to net DC energy?