On average, a humble wind turbine uses less land area per megawatt-hour than almost any other power source. Even so, a wind turbine and its tower can sometimes be too cumbersome. The still-nascent field of airborne wind energy (AWE) has a solution: Swap out the turbine for a kite on a string. Not only is a kite nimbler than a turbine, it can deliver a more constant energy supply.The steady, intense winds some 500 meters above sea level are capable of generating 1800 terawatts: enough to power th...