I just watched it and i would like to add something.
Ii tried one similar to hot aussie drier but it didn't perform well in my place -too much morning humidity, rainfall etc... But i remembered my research about updraft and downdraft driers...
The thing i found was interesting: the air with more humidity in it is lighter than the one with less humidity (relative humidity). The gas law from chemistry explains that because at the same pressure there can only be certain amount of molecules present in the same volume. Since the molecules of water vapour are lighter than average weight of molecules in the air, the drier air is denser (or heavier per volume unit).
gives a simple calculation of air density:
at 50C and 20% density is 1,08 kg/m3
at 50C and 50% density is 1,07 kg/m3
at 50C and 70% density is 1,05 kg/m3
at 40C and 70% density is 1,10 kg/m3
The faster the airflow through the drier, the lesser is the cooling effect and the lesser is the humidifying effect - my conclusion would be that faster air flow saves it all, but it need some more solar gain surfaces to get that air faster to the appropriate temperature...
I would say that in this particular example there is not much of an information but maybe for the future projects it might come handy: humid air is lighter than dry air - contrary to obvious conclusion...
Thinking of it i can't help to think about rocket stoves with low temperature exhaust - now it looks like humidity in them helps to add upwards draft even if cooled to the temperature of the surrounding areas... But the CO2 highers the density of exhaust.
There is also an interesting point:
"Humid air containing water molecules as liquid - droplets - may be more dense than dry air or humid air containing water only as vapor. "
I found that one here: https://www.engineeringtoolbox.com/molecular-mass-air-d_679.html
Pretty complex problems and with so many variables it is hard to walk safely on the edge -