After we left the still for 2 days, we check the water level in both trays. The water evaporated out ~ 1 cm height(~0.8 L). So the rate is about 0.5 cm per day (~0.4 L/day). Our target is about 3L/day, so if we can’t increase the evaporation rate, we would need to increase the size by about 8x.
We cleaned the glass since we found some of the water drop may go back to the tray and then rotate to face South. We will see the result in next 2 days.
An additional action item is to switch to a black tray to reduce reflection of light/heat out of the still.