Wind turbines with telescopic arms could generate double the amount of power (Jeremy Woodhouse/Getty)

GO GO gadget arms! Turbines could soon sport blades that extend and retract to suit wind conditions.

Large turbines harvest more energy from the wind than small ones – provided the breeze doesn’t freshen too much. Then long blades become a disadvantage as they exert big stresses on the turbine’s mechanism, which can damage it. So turbine designers generally strike a compromise between efficiency and durability.

What about a wind turbine with telescopic arms? Rajnish Sharma of the University of Auckland in New Zealand calculated that such a turbine could generate twice as much power over a year as an ordinary one, and be safe to run at high wind speeds. To test the idea, he built a prototype based on a small 1.5-kilowatt turbine. In strong winds it generated the same power as a standard turbine, while in gentler conditions it easily beat its rival.

The extendable blades cost more to make, though Sharma calculates they would be cost-effective even if they were four times as expensive as ordinary ones. The blades could be deployed in areas once thought unsuitable for wind power, Sharma adds. And existing turbines could be retrofitted with the blades, though Sharma has not tested the idea on industrial-scale turbines.