Fluid turbine systems

Abstract

Various fluid turbine systems and methods are described. The turbine can be a vertical axis wind turbine configured to generate power from wind energy. The turbine system can have a blade assembly. The blade assembly can have a plurality of blades rotatable about an axis. The turbine system can have a concentrator positionable upwind and in front of a return side of the blade assembly. The concentrator can define a convex surface facing the wind. The turbine system can also have a variable concentrator positionable upwind of a push side of the blade assembly. The variable concentrator can be adjustable between a first position and a second position, the variable concentrator being capable of deflecting more wind toward the turbine in the first position than in the second position.

What is claimed is: 
     
         1 . A fluid turbine system, comprising:
 a turbine comprising blades rotatable about an axis, the blades defining a window along a substantial portion of a height of the blades, wherein a first plane parallel with and intersecting the axis divides the space surrounding the turbine into a return side and a push side opposite the return side, the turbine configured to rotate generally in an upstream direction on the return side and generally in a downstream direction on the push side relative to a fluid flowing nominally parallel to the plane; and   a concentrator positionable upstream of at least a portion of the turbine and at least partially or completely on the return side, the concentrator comprising a first curved surface portion configured to extend from a first position upstream of the turbine to a second position further upstream of the turbine and further into the return side, wherein the first curved surface portion is configured to be convex facing an upstream direction of the fluid flow, the first curved surface portion positionable to deflect at least some fluid toward the push side, the concentrator further positionable to create a relative vacuum to draw at least some fluid away from the window of the blades.   
     
     
         2 . The fluid turbine system of  claim 1 , wherein the concentrator comprises a second surface portion positionable further into the return side relative to the first curved surface portion, the second surface portion configured to extend from a third position to a fourth position that is further into the return side and further downstream than the third position. 
     
     
         3 . The fluid turbine system of  claim 2 , wherein the concentrator comprises a back surface portion configured to be concave facing downstream, the back surface portion comprising an upstream flow surface portion, an intermediate surface portion, and a downstream flow surface portion, the upstream flow surface portion shaped and positionable to direct at least some fluid flowing upstream from the turbine toward the intermediate surface portion, the intermediate surface portion shaped and positionable to redirect the at least some fluid flowing upstream to flow generally downstream toward the downstream flow surface portion, and the downstream flow surface portion shaped and positionable to receive the at least some fluid from the intermediate surface portion and direct the at least some fluid generally downstream into the fluid flowing nominally parallel to the plane. 
     
     
         4 . The fluid turbine system of  claim 2 , wherein the concentrator is configured to extend in a direction further into the return side at least to an outer edge of the turbine such that the concentrator at least intersects a second plane, the second plane being tangent to an outermost edge of the turbine and parallel to the first plane. 
     
     
         5 . The fluid turbine system of  claim 4 , wherein the second plane is separated from the first plane by a blade tip radius, and wherein the concentrator is configured to extend past the second plane at least twenty-five percent of the blade tip radius. 
     
     
         6 . A fluid turbine system, comprising:
 a turbine rotatable about an axis, wherein a plane parallel with and intersecting the axis divides the space surrounding the turbine into a return side and a push side opposite the return side, the turbine configured to rotate generally in an upstream direction on the return side and generally in a downstream direction on the push side relative to a fluid flowing nominally parallel to the plane, the turbine having a return outer edge furthest away from the push side; and   a concentrator positionable upstream of at least a portion of the turbine and at least partially or completely on the return side, the concentrator comprising a generally u-shaped section, the generally u-shaped section comprising an upstream surface portion positionable to be convex facing upstream and a downstream surface portion positionable to be concave facing downstream, the upstream surface portion positionable to direct a push portion of fluid toward the push side, the upstream surface portion further positionable to direct a return portion of fluid downstream away from the turbine, the downstream surface portion forming a partially enclosed area shaped and positionable to receive a drag portion of fluid from the turbine and redirect the drag portion of fluid downstream into the return portion of fluid, the concentrator having a return end configured to be furthest away from the push side, the return end positionable such that the closest distance between the return end of the concentrator and the plane is at least 1.2 times greater than the closest distance between the return outer edge of the turbine and the plane.   
     
     
         7 . The fluid turbine system of  claim 6 , wherein the entire concentrator is positionable upstream of the entire turbine. 
     
     
         8 . The fluid turbine system of  claim 7 , wherein the concentrator is shaped substantially as a section of a hollow airfoil. 
     
     
         9 . A fluid turbine system, comprising:
 a turbine rotatable about an axis, wherein a first plane parallel with and intersecting the axis divides the space surrounding the turbine into a return side and a push side opposite the return side, the turbine configured to rotate generally in an upstream direction on the return side and generally in a downstream direction on the push side relative to a fluid flowing nominally parallel to the plane, the turbine defining a sweep path; and   a variable concentrator positionable on the push side, the variable concentrator further positionable upstream of the entire sweep path of the turbine, the variable concentrator comprising a deflection surface positionable to extend generally parallel to the axis along a substantial portion of a height of the turbine and adapted to deflect at least some fluid, the variable concentrator being moveable between a first position and a second position, the deflection surface being configured to deflect less fluid toward the turbine in the second position than in the first position.   
     
     
         10 . The fluid turbine system of  claim 9 , wherein the variable concentrator is rotatable about a variable concentrator axis from the first position to the second position. 
     
     
         11 . The fluid turbine system of  claim 10 , wherein the variable concentrator is configured to be biased toward the first position. 
     
     
         12 . The fluid turbine system of  claim 11 , wherein the variable concentrator is configured such that fluid flow over the variable concentrator is operable to adjust the variable concentrator from the first position to the second position. 
     
     
         13 . The fluid turbine system of  claim 12 , wherein the variable concentrator is shaped generally as an airfoil and is adapted to deflect at least some fluid toward the turbine at a low fluid speed to increase torque output, the variable concentrator further adapted to deflect less fluid toward the turbine or not to deflect fluid toward the turbine at a high fluid speed to prevent damage to the turbine. 
     
     
         14 . A fluid turbine, comprising:
 a plurality of blades rotatable about an axis, one or more of the blades defining an open section positioned such that a portion of the open section is closer to the axis than an outside edge of the blade, the turbine comprising a push half and a return half for a given direction of an overall flow of a fluid that defines an upstream direction and a downstream direction;   wherein one or more of the plurality of blades is a push blade, the push blade defining the open section and comprising a tip, the push blade positionable in a push position in which the tip of the push blade is located on the push half, the push blade further comprising a push surface portion facing generally upstream when the push blade is in the push position; and   wherein one or more of the plurality of blades is a catch blade, the catch blade comprising a tip, the catch blade positionable in a catch position in which the tip of the catch blade is located generally downstream of the axis, the catch blade further comprising a catch surface portion facing generally upstream when the catch blade is in the catch position; and   wherein the turbine is positionable in a torque position wherein an upstream blade is a push blade in the push position and a downstream blade is a catch blade in the catch position, the torque position being defined by the downstream blade being located generally downstream of the upstream blade and the catch surface portion of the downstream blade being located directly downstream from the open section of the upstream blade.   
     
     
         15 . The fluid turbine of  claim 14 , wherein one or more of the plurality of blades is a lift blade, the lift blade comprising a tip, the lift blade positionable in a lift position in which the tip is located generally upstream of the axis, the lift blade further comprising a curved surface portion, the curved surface portion being convex facing away from the return half when the lift blade is in the lift position, the curved surface portion shaped and configured to deflect a lift portion of a fluid flowing generally downstream across the curved surface away from the return half when the lift blade is in the lift position. 
     
     
         16 . The fluid turbine of  claim 15 , wherein the lift blade defines the open section, the open section of the lift blade operable to allow at least some of the lift portion of fluid to flow through the open section of the lift blade. 
     
     
         17 . The fluid turbine of  claim 15 , wherein the plurality of blades comprises four blades extending from the axis and equally spaced from each other, and wherein each of the four blades is a lift blade, a push blade, and a catch blade, the four blades defining the open section such that an inner radial half of the four blades is substantially open, the four blades comprising a front surface portion and a back surface portion, the front surface portion and the back surface portion being located at least substantially on an outer radial half of the blades:
 wherein the front surface portion comprises a generally straight portion and a curved portion located radially outward from the generally straight portion, the four blades positionable in a horizontal position in which the generally straight portion is perpendicular to the plane and facing upstream, the curved portion being located further upstream than the generally straight portion when the blades are in the horizontal position; and   wherein the back surface portion extends from a first end near the tip of the blades to a second end near the open section, the back surface portion being substantially curved and shaped to be convex facing downstream when the four blades are in the horizontal position, the back surface portion shaped and configured such that a point on the back surface portion located furthest downstream when the four blades are in the horizontal position is between the first end and the second end of the back surface portion.   
     
     
         18 . The fluid turbine of  claim 17 , wherein the horizontal blade sections comprise at least two blades configured to be fixed in relation to an adjacent horizontal blade section and angularly offset from the adjacent horizontal blade section. 
     
     
         19 . The fluid turbine system of  claim 18 , wherein the array comprises at least three horizontal blade sections angularly offset to form a virtual helix adapted to reduce cycles in torque output.