Airborne Wind
The developments in renewable energy over the last decade can be summed up as follows: the winners have won and the losers have lost. The plummeting costs of energy from solar and wind have put extreme pressure on things like hydrokinetics and the others.
Whatever happened to airborne wind? The attraction of a wind turbine that could float high above the Earth’s surface where wind velocities are much greater seem to have promise for a time–especially insofar as power is proportional to the cube of velocity.
Indeed, even though there are daunting physical challenges, as presented in the article linked above, some folks haven’t given up. Interesting stuff.