Renewables capacity assumptions

I am very interested in using sis-energy-derived-projections table. I wonder what assumptions are being taken as regards installed wind and solar panel capacities. I understand that the capacity ratio factor is changing, that the climate variables affect production. However, the capacity assumptions play are role in the whole equation as well. I could not find any description in confluence how the capacities are projected to the future. Can anyone explain it and provide references to the algorithms?