I had problems with running direct sun studies (from courses)
Simulation tool up all my RAM - 27 gb and cpu usage was 10 % -60 % (ryzen 2700x)
After changing from 1 year study to 1 h study I realized that i have started to work on cm template in rhino and simulation surfaced was way in grid 1x1 cm not 1x1 m
Would recommend to check level of detailing.