Not so much for the wings + Wind Turbines + Solar Cells but because it is not one hull but Seven (7!) each one of those sub sections is essentially a barge with a rugged locking mechanism that creates a rigid sea going hull once engaged. This way the crew and propulsion section can drop off and pick up sections either all or one or two as they make their rounds and the expensive bit gets much more use as well as being smaller and less expensive, probably safer as well.