Operation of Darrieus Helix Wind Turbines for Small Wind.
Because the Darrieus design is more suited to small wind turbines, we will examine how they operate using the Quietrevolution qr5 small wind helix turbine as an example. (See Image below.)
The vertical axis wind turbine has a number of blades in the shape of a helix. A helix blade is really a straight blade tapered at each end, but with a twist in the middle.
The blades are vertical and run from the top of the turbine to the bottom held in place by spider supports, the flat section in the middle of the blades catching the wind and causing them to rotate. Because of the helix shape, the blades can scoop up the wind from any direction; this is a big bonus as yaw or pitch mechanism is not required also saving weight, energy, and reducing noise levels.
There are thrust bearings fitted at the top and bottom of the blade central shaft, since the wind attempts to “lift" the turbine. This is prevented by the thrust bearings, and consequently the kinetic energy of the wind is converted to mechanical energy.
Attached to the bottom of the blades is a generator, which being direct-driven negates the use of a gearbox, reducing noise and weight. It also has the advantage of being accessible for maintenance.
As well as ground-mounted, the turbine can be mounted on a mast of 35’ or rooftop mounted, using a 6' mast bolted to the gable end of the house.
Darrieus helix turbines can also be mounted on flat roofs using ground-mounting kits, and along with photovoltaic panels as a hybrid system.