Abstract:
An apparatus for generating electricity from a moving liquid has a generally oblate casing and a generally helicoid working member adapted to convert energy of a flowing fluid into rotation of the casing. A rotor-like element of an electrical generator is coupled to the rotating casing. A stator like element of an electrical generator is coupled to a stabilizing element. The stabilizing element may be a fin, a counter-rotating turbine, or another structure that develops torque from the moving liquid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application 61/189,950 entitled, “Fine Arts Innovations,” and filed Aug. 22, 2008, and 61/202,126 entitled “Apparatus for Generating Electricity from Flowing Fluid Using Generally Prolate Turbine,” and filed Jan. 30, 2009, the disclosures of which are incorporated herein by reference in their entireties. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    None. 
       NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    None. 
       BACKGROUND 
       [0004]    The generation of electricity from water today predominantly uses impoundments, such as dams. 
         [0005]    To convert water currents into electricity without impoundments, in-stream energy conversion devices are placed in a flowing stream. According to the Electric Power Research Institute, such in-stream electricity generation without using impoundments remains a largely untapped potential. See, e.g., “North American Ocean Energy Status,” Electric Power Research Institute, March 2007. This report states that the world&#39;s first marine renewable energy system of significant size to be installed in a genuinely offshore location was the Marine Current Turbine (MCT) 300 kw experimental SeaFlow unit installed off the coast of Devon, UK in May 2003. The MCT SeaFlow unit used a rotating, axial-flow turbine using hydrodynamic, generally planar blades as working members. (The term “working member” here refers to a member having a surface that functions to react with a working fluid, such as water, such that movement of a working fluid causes movement of the working member.) The report discusses other in-stream projects that use axial-flow turbines with generally planar blades. The Verdant Power 5.5 axial flow turbines were installed in the East River of New York beginning in December 2006. The Canadian Race Rocks British Columbia Tidal Project delivered electricity for the first time in December 2006. 
       SUMMARY 
       [0006]    An object of some embodiments of the invention is to provide an improved, in-stream apparatus for generating electricity from fluid flows, especially relatively shallow river and tidal flows. Other objects of some embodiments the invention are to provide:
       (a) improved apparatus for generating electricity with low impact on marine life,   (b) improved apparatus for generating electricity in reversible current flows, such as tidal flows,   (c) improved apparatus for generating electricity at low cost, and   (d) scalable arrangements of apparatus for generating electricity.       
 
         [0011]    These and other objects are achieved by providing a turbine that uses a generally helicoid working member to convert a tidal or river flow into rotational motion of a generally prolate carrier. (By way of non-limiting example, a football could be considered as having a prolate shape.) Helicoid working members on the exterior of such carriers reject debris, and they tend not to catch or otherwise harm marine life. The generally prolate shape can have low drag, provide an internal volume for electricity-generation equipment, and provide buoyancy through displacement, if desired. The generally prolate shape can accelerate fluid flow around its periphery and provide an increased radial moment and increased torque about its central axis when compared to comparably-sized working members on a circular cylinder. They can work well partially submerged in shallow surface currents as well as completely submerged in deeper water applications. 
         [0012]    The turbine generates electricity by causing relative rotation of stator-like and rotor-like elements of an electrical generator. (The terms “stator-like” and “rotor-like” are used here as broader terms than “stator” and “rotor” in that they do not require either to be fixed or rotating, nor do they require either to have a specific internal construction. For example, where an electric generator uses magnets in one element and coils in another element, either or neither may be fixed, and one or both may be rotating when viewed from an external point of reference. Either may be a “stator-like” or “rotor-like” element.) Various arrangements may be used to cause relative motion between a stator-like element of an electrical generator and a rotor-like element. A fin may be provided to hold the stator-like member in a relatively fixed orientation when viewed from an outside reference point. Alternately, the stator-like member may be driven by another turbine to counter-rotate relative to the rotor-like element. 
         [0013]    Multiple turbines may be anchored in groups in tidal, river, or other streams. Their axes of rotation preferably will be generally parallel with the prevailing fluid flow, but it has been found that the prolate carrier and helicoid working member also perform well with oblique currents. Their rotational axes may be coaxial (in line) or offset. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0014]    Reference will be made to the following drawings, which illustrate preferred embodiments of the invention as contemplated by the inventor(s). 
           [0015]      FIG. 1  illustrates a top plan view of a generally prolate turbine according to an embodiment of the invention. 
           [0016]      FIG. 2  illustrates a side plan view of a generally prolate turbine according to an embodiment of the invention. 
           [0017]      FIG. 3  illustrates a front plan view of a generally prolate turbine according to an embodiment of the invention. 
           [0018]      FIG. 4  illustrates a series arrangement of generally prolate turbines according to an embodiment of the invention. 
           [0019]      FIG. 5  illustrates an offset arrangement of generally prolate turbines according to an embodiment of the invention. 
           [0020]      FIG. 6  illustrates an exploded view of a first arrangement of components of a generally prolate turbine according to an embodiment of the invention. 
           [0021]      FIG. 7  illustrates a cut-away view of components of the turbine of  FIG. 6  without casing. 
           [0022]      FIG. 8  is an exploded view of a second arrangement of components of a generally prolate turbine. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  illustrates a top plan view of an embodiment of a generally prolate turbine  10 . The turbine  10  includes two generally helicoid working members  12   a ,  12   b  that spiral around a generally prolate casing  11 . The two working members  12   a ,  12   b  are interleaved like double-start screw threads. A fin  13  is mounted at an upstream end of the casing, and an optional drag  14  is mounted at the opposite (downstream) end from the fin  13 . 
         [0024]    When the turbine  10  is placed on the surface of flowing water and secured at the upstream end by a tether (not shown), water naturally orients the turbine  10  with the upstream end (with fin  13 ) pointing upstream (to the right in  FIG. 1 ), and the downstream end (with drag  14 ) pointing downstream. In such an orientation, the water flow impinging on the helicoid working members  12   a ,  12   b  causes the working members  12   a ,  12   b  and attached casing  11  to rotate. 
         [0025]    The casing  11  is generally prolate, that is, generally symmetrical about a central axis, wider in the middle, and narrower at the ends. The casing  11  may be manufactured in two parts with an upstream shell  16   a  and downstream shell  16   b . While a generally prolate casing is desired, the degree of curvature of casing  11  is not critical, and the casing need not be a mathematically perfect prolate shape. The embodiment of  FIG. 1  shows two working members  12   a ,  12   b , though a different number of working members may be used. The embodiment of  FIG. 1  has working members with a lead (axial distance covered by one turn of the thread) of approximately one-half the length of the turbine, but other leads may be used. 
         [0026]    The fin  13  preferably mounts at the upstream end of the casing to a hollow shaft  19  and projects away from the central axis into the fluid stream. The shaft  19  penetrates the casing  11  through a bearing and seal  18  and extends along at least part of the interior central axis of the casing  11 . The fin  13  maintains a generally stable position at the water surface. The bearing  18  allows rotation of the casing  11  relative to the shaft  19  and fin  13 , and the water seal prevents water penetration. The fin  13  holds the shaft  19  in a relatively fixed rotational position while the casing  11  rotates about the shaft  19 . As will be discussed further below, the shaft  19  couples internally to a stator-like element of an electric generator (not shown), and the casing  11  couples internally to a rotor-like element. Torque from the working elements  12   a ,  12   b  may be coupled through the generator to the shaft  19  and cause the shaft  19  to roll. Such roll dips the fin  13  deeper into the water, which increases the fin&#39;s counter-balancing torque and keeps the stator-like element fixed relative to plane of the water surface. Electrical conductors  17  carrying electricity from the internal generator (not shown) preferably exit the casing  11  through the interior of the hollow shaft  19 . 
         [0027]    The turbine  10  of  FIG. 1  preferably is positively buoyant and floats on the surface. Nevertheless, it may be advantageous to adjust the buoyancy, and the turbine  10  may include internal ballast bladders or compartments (not shown) with access ports  15  to allow positive or negative buoyancy. 
         [0028]    An optional drag  14  attaches to the casing  11  at the downstream end. The illustrated drag has a semi-rigid shaft and terminates with conical, cross-fin, or other tail. The drag  14  assists in maintaining turbine orientation similar to the way the fins on an arrow maintain the head pointing in the direction of flight, that is, by providing fluid drag downstream of the center of mass. 
         [0029]      FIG. 2  illustrates a side plan view of a generally prolate turbine  10 . This view illustrates the curvature of the fin  13 . Under light load from the generator and working members  12   a ,  12   b , the shaft  19  rotates so that the fin  13  is only slightly in the water. As generator load increases, the shaft  19  rolls further so that more of the fin dips into the water flow, which in turn increases the balancing force acting on the fin  13 . The shaft  19  rolls until the fin  13  generates an amount of torque to balance to the torque imparted by the working members  12   a  and  12   b  through the casing  11  and internal generator (not shown). 
         [0030]      FIG. 3  illustrates a front plan view of a generally prolate turbine  10 . This view better illustrates the interleaved-relationship of the two working members  12   a ,  12   b . It also better illustrates how rotation of the fin  13  increases the exposure of the fin  13  to water and thus increases the amount of counter-balancing torque developed by the fin  13 . 
         [0031]      FIG. 4  illustrates a series arrangement of generally prolate turbines  40   a ,  40   b  held with their axes of rotation generally aligned with a prevailing current flow between two submerged anchorages  41   a ,  41   b . The turbines  40   a ,  40   b  are essentially the same as the turbines of  FIGS. 1-3  in that each turbine  40   a ,  40   b  has a generally helicoid working member rotating a generally prolate casing to cause relative opposite rotation between a stator-like element and a rotor-like element. The generally helicoid working members will generate power in reversing flows, such as tidal flows, without need for re-orientation. 
         [0032]    When completely submerged in series, the turbines may omit stabilizing fins. Instead, alternating turbines counter-rotate, and upstream turbines provide counter-rotational torques to downstream turbines. For example, the casing of an upstream turbine couples through a universal joint to the shaft (and ultimately rotor-like element) of a downstream turbine. More than stabilizing the downstream stator-like element, the upstream turbine counter-rotates the stator-like elements of the downstream turbines. In  FIG. 4 , for example, turbines  40   a  may rotate in a clockwise direction about their axis of rotation, while turbines  40   b  rotate in the opposite direction. For a turbine in the middle of the series, its working member drives its own, internal, rotor-like element in one direction, while the working member of the immediate upstream turbine drives the stator-like member in an opposite direction. Generators transfer electricity through brushes to cables or other electrical conductors (not shown), which in turn pass between turbines and ultimately transfer electricity to fixed connections on one or both anchorages  41   a ,  41   b.    
         [0033]    At the upstream end of the series of turbines, an upstream anchorage  41   a  connects through a shaft  42  or other non-rotating attachment to the stator-like element of the first turbine. At the downstream end of the series of turbines, a downstream anchorage  41   b  attaches to the rotating casing of the last turbine through a shaft, cable or other attachment. The downstream attachment may be fixed to the casing through a bearing at either the downstream turbine or the anchorage  41   b  to allow rotation of the turbine relative to the anchorage  41   b . In the arrangement of  FIG. 4 , torques on the stator-like elements of turbines ultimately are derived from the fluid flow, except for the first turbine of the series, which may derive torque from the upstream anchorage  41   a.    
         [0034]      FIG. 5  illustrates a parallel arrangement of generally prolate turbines held in a frame  53  with their axes of rotation parallel, offset, and generally aligned with a prevailing current flow. The turbines are essentially the same as the turbines of  FIG. 4  in that each turbine has a generally helicoid working member  51   a ,  51   b  rotating a generally prolate casing  52   a ,  52   b  to cause rotation of a rotor-like element relative to a stator-like element. Turbine casings  52   a ,  52   b  counter-rotate. 
         [0035]    The casings  52   a ,  52   b  of turbines each connect internally to a rotor-like element. Each of the casings  52   a ,  52   b  also connects externally through drive system  54   a ,  54   b  to the stator-like element of the other turbine. The drive systems  54   a ,  45   b  preferably are belt or chain drives, but other mechanical couplings may be used. The casings  52   a ,  52   b  power the drive systems  54   a ,  54   b  through drive members  55   a ,  55   b , which are pulleys in the case of a belt drive, or sprockets in the case of chain drives. The opposite end of the drive system  54   a ,  54   b  from the drive members that cause counter rotation  55   a ,  55   b  are corresponding pulleys or sprockets coupled to shafts that connect internally to stator-like members of the adjacent turbine. The drive members and their corresponding pulleys or sprockets may have differing diameters to effect a step-up or step-down ratio. Shafts and casings may be journaled with bearings  57   a ,  57   b ,  57   c ,  57   d  to allow rotation of shafts and casings relative to the frame  53 . Through this arrangement, each working member  51   a ,  51   b  applies a torque to its own casing and to the stator-like member of the neighboring turbine. 
         [0036]    The parallel arrangement of turbines may be connected through a frame  53  to an anchorage (not shown). The counter-rotation and cross-coupling of turbines allows a balancing of torques so that the frame  53  experiences little if any net torque as a result of the action of the fluid on the working members  51   a ,  51   b . Downstream bearings  57   b ,  57   d  will transfer axial (thrust) loads to the frame  53  that results from the fluid acting on the working members  51   a ,  51   b.    
         [0037]      FIG. 6  illustrates an exploded view of a first arrangement of components of a generally prolate turbine. It shows a casing made of two parts  61   a ,  61   b , with each part supporting portions of a generally helicoid working member  62   a ,  62   b . When assembled, the casing parts  61   a ,  61   b  and working member portions  62   a ,  62   b  align to give an overall shape as the turbine of  FIGS. 1-3 . The turbine of  FIG. 6  also has a fin  63  at the upstream end connected to a shaft  65 , and a drag  64   a  at the downstream end connected at an attachment point  64   b , similar to those of the turbine of  FIGS. 1-3 . 
         [0038]    The fin  63  is designated as “stationary” with the understanding that it may experience some roll of a fraction of a revolution. In contrast, the casing is designated as “rotating” with the understanding that it will rotate through complete revolutions. 
         [0039]    The fin  63  attaches to a shaft  65 , which in turn connects to the stator or a stator-like member of an electric generator  66 . The rotor or rotor-like member of the electric generator  66  attaches through a seal  67   a  and flange  67   b  to the downstream part of the casing  61   a . Electric wires  68  carrying electricity from the stationary generator pass through the shaft  65 . A bearing  69  mounted in the upstream part of the casing  61   b  allows relative rotation between the casing and the shaft  65 . The shaft  65 , generator  66 , and wires  68  are designated as “stationary” similarly to the fin  63 . Seals prevent water from causing electrical short circuits in the generator or any components carrying electricity. 
         [0040]    The generator should be sized to the expected conditions of the prevailing fluid flow and to the geometry of the turbine so that the prevailing fluid flow turns the casing at a rotation rate that is optimal for the generator without need for a transmission to step-up or step-down the rate. An exemplary turbine might be eighty-eight (88) inches in length with a casing width of twenty-nine (29) inches at the widest point. The drag may extend fifty-two (52) inches. Two working members could be provided, each having a radial height of about 6.25 inches at the widest point and making two turns over the length of the casing. For river or tidal flows of about four (4) knots, a component generator could be a model 300STK4M manufactured by Alxion of Colombes, France. These dimensions are merely exemplary, and the turbines of substantially larger dimension are contemplated, including sizes appropriate for generating ones or tens of megawatts of power (comparable to thousands or tens of thousands of horsepower). 
         [0041]      FIG. 7  illustrates a cut-away, assembled view of components of the turbine of  FIG. 6  without casing. This figure illustrates working member sections  62   a ,  62   b ; fin  63 ; drag  64 ; shaft  65 ; generator  66 ; and electric wires  68  as described previously. Also shown are longitudinal, shape-support members  70  running axially along the length of the casing (not show). The shape-support members  70  may be made of continuous plate material but preferably have portions removed to reduce weight. Circumferential shape-support members may be used instead of axial members, especially in rotating sections that might contain ballast water. 
         [0042]      FIG. 8  is an exploded view of an alternate interior arrangement of rotor-like element  81  and stator-like element  82  for an electricity generator for a generally prolate turbine. This figure illustrates upstream and downstream casing sections  61   a ,  61   b ; working member sections  62   a ;  62   b ; fin  63 ; drag  64   a ; and shaft  65  as described previously. In this embodiment, the rotor-like element  81  has a diameter approximately equal to the casing and mounts directly to the interior of the downstream casing  62   a . The rotor-like element  81  may be used to join the upstream and downstream casing sections together, such as by fastening both casing sections to the rotor-like element  81 . The rotor-like element  81  includes a rotational thrust bearing  83  that transfers the axial load of the working members  62   a ,  62   b  to the shaft  65 . 
         [0043]    The embodiments described above are intended to be illustrative but not limiting. Various modifications may be made without departing from the scope of the invention. The breadth and scope of the invention should not be limited by the description above, but should be defined only in accordance with the following claims and their equivalents.