To inspect the blades of the more than 270,000 wind turbines operating globally, technicians have traditionally relied on binoculars and field scopes from the ground, or have scaled the turbines with the help of ropes or cables. Today, unmanned aerial vehicles are providing a safer option, with the benefit of higher-resolution imaging. Cumulative global revenue for wind turbine UAV sales and inspection services is expected to reach nearly $6bn by 2024, according to a Navigant Research report.

The year 2013 saw record-breaking growth for solar electricity generation as the photovoltaic and concentrated solar thermal power markets continued to grow. With over 39 gigawatts installed worldwide, the PV solar market represented one third of all newly-added renewable energy capacity, according to Max Lander and Xiangyu Wu writing in the latest number of the Worldwatch Institute's Vital Signs Online publication.