Google X was established to work on the million-to-one scientific bets, projects that require generous funding, leaps of faith and a preparedness to break things, which explains the remarks made by Google X director Astro Teller when the acquisition was announced. "He [Google CEO Larry Page] said we could have the budget and the people to do this, but that we had to make sure to crash at least five of the devices in the near future," he said.
Google has backed Makani to the tune of $15 million over the past seven years and a full takeover became more likely after the death last October of Makani's founder and design team leader, Corwin Hardham.
Makani completed the first fully autonomous flight of a 30kW kite power system, the M30, on 9 May. Work has also begun on a three-year programme to design, test and commercialise a 600kW version, dubbed the M600.
High-altitude wind is being pursued by a number of start-ups employing different turbine designs. The companies include Windlift of North Carolina, which has backing from the US Department of Defence.
"Potentially, it's a very interesting technology," says Dr Fort Felker, director of the National Wind Technology Centre. But he warns that it's too early to say whether the technology can deliver on the clear advantages of high-altitude winds. These include the faster and steadier speeds of wind at height, which boosts power and provides few grid integration problems, and the reduction in weight and raw materials provided by the turbines not requiring a tower or foundation.
According to a 2012 study in Nature magazine, conventional wind turbines could generate 400TW of power globally, but high-altitude turbines could produce more than 1800TW.
However, there are signficant obstacles to overcome, ranging from the reliability of all flight vehicles and their access for maintenance, to conflicts over airspace given that most designs for high-altitude turbines are not stationary. Years of data will be required for regulatory purposes, says Dr Felker, who believes it could be a decade before commercialisation of high-altitude wind turbines is achieved. Niche applications, on remote islands or for military projects, are the most promising areas for development, he says.