Kite turbines generate more power

Joby Energy in California is testing kites flying at an average height of 400m (1,300ft) – around five times the height of a ground-based turbine – where winds are faster and more consistent.

The first prototypes can produce up to 30kW of power, but the firm is developing a system that is designed provide between 300kW and 3MW – enough to supply up to 1,500 US homes. It hopes to begin manufacturing in 2012.

The modular kites can be built with five tons of material per MW produced, compared to nearly 100 tons for conventional wind turbines, giving them a capital cost of under $1 (£0.7) per watt.

Although air is thinner at higher altitudes, meaning lower power density, winds are much faster because of the lack of obstacles and friction from the ground. This means that overall power density is much higher.

A spokesperson from Joby told The Engineer: ‘By tapping in to the more powerful winds, our system can produce twice the amount of energy as a ground-based wind turbine of the same capacity.