As the former chief designer of the Nautilus class of nuclear submarines, "The Captain" (USN, ret.) knew his way around the ocean.  A large portion of the top engineering execs in US windpower went through his program at UMass Amherst.  Here's the ammonia version from Popular Science around the same time.

Today's versions of the designs are very much more sophisticated.  He passed on a few years ago, and i miss his cantankerous wisdom dearly.

The concept of multiple rotors replacing one large rotor is that each level is tuned to the stronger winds it sees, giving higher efficiencies than a super rotor.  Despite many more parts, they are much easier and cheaper to mass produce to rigorous standards.  Further, there is little risk today for a 20 meter rotor, while the super rotors have many unknowns remaining.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin