The Windjoule energy machine is a vertical axis drag differential device.

It is the result of blue sky clean sheet thinking, designed to make use of the available UK on shore wind resource.

The UK Average Mean Wind Speed is

5 metres per second, conventional wind turbines produce their rated power output at 11-14 mps.

It works by leveraging the wind collected by the sails in power mode against a small amount of aerodynamic friction caused when the sails are parallel to the wind in return mode. The sails are free to pivot to the most efficient position. Wind tunnel testing of ¼ scale prototypes at Cranfield University in 2009 showed an advantage of 5 times more power over conventional turbines, of the same size. At a windspeed of 10mph the tip speed of the rotor was measured at 9.7mph which demonstrates how great the differential is.

The originality of the invention is reflected by the grant of a European Patent.