The commercial generation of power by wind, as on wind farms, is through the utilization of turbines of the horizontal axis category.  This category wind turbine is known by the familiar image of a giant propeller atop a tall, slender tower.  Being suitably powerful and reliable, these are the wind turbines capable of utility-scale power generation.

There is a second category of wind turbines, known as vertical axis wind turbines, or by the acronym VAWT.  No turbine of this category, both powerful and suitable, has yet been developed for commercial-scale utility.  The lack of a VAWT suitable for utility-scale power generation is attributable to the category’s problematic aerodynamics which generates a cyclic load against the turbine.  Cyclic loading has deleterious effects on a turbine, wearing components and, in some cases, leading to their fatigue and failure.  The larger and more powerful the turbine, the more severe the cyclic loading.                                                                                                                                                 

Cyclic loading has plagued all the large VAWT prototypes and frustrated attempts to commercialize a powerful VAWT.  It originates in the reversing nature of VAWT aerodynamics, wherein a turbine blade moves with the wind during one leg of its circuit and against the wind in the following leg.  This engenders a problematic back-and-forth airflow, encountered by a blade as it moves through its circuit.  To address the back-and-forth aerodynamics, a blade having airfoil camber on both sides is deployed and the generation of lift switches from one side to the other as the dual camber blade travels its circuit.

So generated, lift resolves into two orthogonal components: one is motive torque, the other is load.  Load is the unwanted component and is directed radially against the turbine as either a push or a pull, that is, either centripetally or centrifugally.  As the generation of lift alternates between the inboard side and the outboard side of a blade, load alternates between push and pull.  The value of lift varies from point to point on a blade’s circuit, and, likewise, the value of load, which varies over a wide range.  At one point in a blade’s circuit, load reaches its maximum value, exceeding that of motive torque.  This is the problematic cyclic loading.  Added to the load generated at the blade is the centrifugal force of rotation, which combines with lift vectorially and aggravates cyclic loading.

Wind turbines of the vertical axis category are also known as Darrieus turbines, after the inventor Georges Darrieus.  The main aspect of Darrieus design is a turbine supported centrally, at a shaft or a derrick positioned at the axis of rotation.  The Darrieus turbine has been the focus of VAWT design and experimentation for the past four decades, during which period about thirty large Darrieus prototypes have been tested.  Of these thirty prototypes, none proved suitable for utilization in the generation of power for commercial distribution.  

Despite such unfavorable results, some students of wind power, including the applicant, consider the vertical axis category to hold potential for a powerful and efficient  turbine, capable of reliably generating wind power on a commercial scale.  However, a VAWT that achieves commercial requirements is heretofore unattained, such requirements herein  defined as including the capability of generating at least one megaWatt of power.  The VAWT prototypes have demonstrated, however, that any attempt at such power is doubtful of success if undertaken without an effective remedy against cyclic loading.  The disclosed blade mounting system offers such a remedy.

The Darrieus method of supporting the turbine at a central derrick or shaft, presents another obstacle against achieving a powerful turbine. This method of support has shortcomings, in that it imposes practical limits on turbine size and hence, on power, as power is primarily a function of turbine size; indeed, the larger the turbine, the greater its power.  Therefore, the present invention utilizes a turbine designed as an annular framework, as will be discussed in following paragraphs, rather than the conventional Darrieus turbine structure.