The article is written in environmental speak.... words and some vauge science.... and makes no sense in the real world.
If you were to get their claimed figures and find out what they really mean, then I suspect their 30% compared to normal mill will look decidedly like .03% in reality, as it has no swept area....
So perhaps we can rely on their figures to mean 30% less efficient in converting kinetics to power... then take out the ratio of swept area of the prop version to the pencil version of theirs...their power figures disappear into obscurity...... it feels like cold fusion..... or more likely, global warming .... money for nothing... ie research grants and feed money... and no product......... as it was never going to work usefully, or as purported.
.................oztules