Abstract:
Methods and apparatus for improved power generation through movement of water retrofitting existing hydroelectric dams with draft tube inserts and tailrace walls to increase water velocity for production of power using hydrokinetic turbines installed in the tailrace. By initial design or by draft tube inserts and tailrace walls, increased and streamlined water flow leads to higher efficiencies of the hydrokinetic turbine, thus more efficiently converting available kinetic energy of the water into usable energy.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 11/983,989 filed on Nov. 13, 2007, issued as U.S. Pat. No. 7,837,411 which is based on provisional application Ser. No. 60/859,789, filed on Nov. 17, 2006, which is incorporated as if fully set forth herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     DESCRIPTION OF ATTACHED APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of energy and more specifically to methods and apparatus for an improved hydropower system. 
     There are a variety of prior art systems for extracting power from water based systems such as dams, rivers and ocean flows. Several patents disclose a variety of after market retrofits for extracting hydropower from river flow by inserting additional equipment at the base of the dam to take advantage of the head potential present behind the dam. For example, U.S. Pat. Nos. 4,073,146, 4,078,388, 4,117,676, 4,159,188, 4,165,467, 4,170,428, 4,261,171, 4,279,539, and 4,468,153 show a retrofit system for extracting energy out of the head potential of a dam. None of these patents shows the innovative combination of the present invention and its use for increased extraction of kinetic flow energy in a downstream system and innovative method of increasing flow velocity for kinetic hydropower. 
     One of the current problems facing hydrokinetic power producers when locating hydrokinetic turbines downstream of existing dams is that the design of the draft tube at an existing dam (the draft tube conducts water from the outlet of the turbine to the body of water downstream of the existing dam) is specifically designed to dissipate kinetic energy. That is to say, the draft tube is a diffuser. The diffuser sometimes takes the shape of a frustoconical or an elliptically shaped conical fusta due to underwater bathymetry. The end result of the draft tube diffuser is that the kinetic energy of the water is lowered, meaning the water velocity is slowed. An additional problem that hydrokinetic power producers face at dams is that many tailrace designs dump water from the outlet of the draft tube into an open body of water, such as a lake, reservoir, pool, or river to additionally dissipate the kinetic energy of the water in the tailrace exiting the draft tube. 
     BRIEF SUMMARY OF THE INVENTION 
     The primary advantage of the invention is to provide improved hydrokinetic power system. 
     Another advantage of the invention is to provide a retrofit for existing dams to increase velocity of flow to a kinetic power system. 
     Another advantage of the invention is a method to retrofit existing hydropower dam system outflow draft tubes to lessen the loss of flow velocity to improve efficiency and increase power in downstream hydrokinetic turbines. 
     Another advantage of the invention is to provide wall system to channel flow to increase kinetic energy downstream of a dam for a hydrokinetic power system. 
     A further advantage of the invention is to provide a kinetic power system that utilizes increase flow dynamics in situ. 
     In accordance with a preferred embodiment of the invention, there is disclosed a system for improved power generation having a dam storing water as potential energy, one or more hydroelectric turbines positioned in the dam to receive the kinetic movement of water, one or more draft tubes to conduct water from the outlet of the hydroelectric turbines to a body of water downstream of the dam tailrace, one or more reciprocal draft tube inserts placed in the draft tube to reduce the water diffusing characteristics of the draft tubes and increase water velocity at the draft tube outlets, and one or more hydrokinetic turbines installed in the dam tailrace to produce energy from the water flow exiting the draft tube outlets. 
     In accordance with another preferred embodiment of the invention, there is disclosed a system for improved power generation having a dam storing water as potential energy, one or more hydroelectric turbines positioned in the dam to receive the kinetic movement of water, one or more draft tubes to conduct water from the outlet of the hydroelectric turbines to a body of water downstream of the dam tailrace, one or more walls fixably attached to the dam tailrace bottom and draft tube outlet side of the dam perpendicular to the dam to channel the dam outlet water, and one or more hydrokinetic turbines installed in the dam tailrace receiving the water flow channeled by the walls in the dam tailrace. 
     In accordance with a preferred embodiment of the invention, there is disclosed a method for improved power generation having the steps of storing water as potential energy behind a dam, converting the potential energy to electricity by moving stored water through one or more hydroelectric turbines positioned in the dam to receive the water, conducting water through one or more draft tubes to from the outlet of said hydroelectric turbines to the dam tailrace, reducing the water diffusing characteristics of the draft tubes and increasing water velocity at the draft tube outlets through one or more draft tube inserts, and positioning one or more hydrokinetic turbines in the dam tailrace to produce energy from the water flow exiting the draft tube outlets. 
     Other objects and advantages of the present invention will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
         FIG. 1  shows a schematic diagram of a power generating station on a dam in a conventional configuration using head potential to generate power through a turbine and outflow through a draft tube. 
         FIG. 2  shows a retrofit insert and draft tube exit wall in combination with a hydro kinetic turbine according to a preferred embodiment of the present invention. 
         FIG. 3  shows a plan view of a conventional draft tube and turbine power assembly with attendant decrease in velocity of water exiting the turbine. 
         FIG. 4  shows a draft tube insert according to a preferred embodiment of the present invention and effective reduced diameter of draft tube for increased velocity 
         FIG. 5  shows a conventional power configuration without tailrace walls and attendant dissipated power potential to kinetic turbine downstream. 
         FIG. 6  shows tailrace walls for increased power potential to downstream hydro kinetic power turbines in multiple wall configurations and shapes. 
         FIGS. 7A and 7B  show a cross sectional view of a representative tailrace vertical wall and tailrace box wall respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
     A system to retrofit existing hydropower dams so that the kinetic energy in the tailrace (the tailrace is the body of water directly at the outlet of the draft tube) can be increased for higher hydrokinetic energy production at a downstream hydrokinetic energy generating power station.  FIG. 1  shows a conventional power system  10  where head power from the upstream water blocked by a dam  12  is used to drive turbine  14  to generate power. Outflow of turbine  14  is through draft tube  16  which dissipates the flow of water from the turbine to reduce turbulence and other negative effects. 
     As previously mentioned, one of the current problems facing hydrokinetic power producers when locating hydrokinetic turbines downstream of existing dams is that the design of the draft tube at an existing dam (the draft tube conducts water from the outlet of the turbine to the body of water downstream of the existing dam) is specifically designed to dissipate kinetic energy. The end result of is that the kinetic energy of the water is lowered, meaning the water velocity is slowed, thus reducing potential capture of energy. 
     A hydrokinetic turbine, one which operates solely on the water velocity, and not the pressure head of impounded water, from a theoretical standpoint, require the highest possible water velocity and the largest possible turbine diameter in order to generate the greatest amount of power possible. 
     By installing a retrofit to the draft tube of the existing dam or designing the draft tube for optimal flow can result in a significant increase in the streamlined or turbulent flow velocity at the outlet of the draft tube, resulting in a much higher velocity at the downstream hydrokinetic turbine thereby increasing the power output. This can be accomplished in a number of ways by adding a retrofit draft tube insert or initially designing a draft tube for a new dam such that the diffusing rate that is lower but still of a diffusing design (the ratio of area&#39;s is still positive) or have a constant diameter draft tube or slightly decrease the draft tube diameter to compensate for minor frictional losses in the draft tube due to the materials of construction of the draft tube. 
     In a preferred embodiment, the flow may be streamlined as it lends itself to higher efficiencies of the hydrokinetic turbine, thus more efficiently converting available kinetic energy of the water into usable energy (shaft work). 
       FIG. 2  shows a combination of an insert to the draft tube and exit wall according to a preferred embodiment of the invention. Power system  20  has one or more conventional turbines  24  placed in dam  22  for generation of power from the head potential of the dam. A draft tube  26  is fitted with a reciprocal tube insert  28  for changing the flow characteristics of the tube. Preferably, but not required in all situations, is draft tube exit wall  30  placed in line with the inserted tube  28  to further channel the flow of water to the hydrokinetic turbine  32 . 
     Reciprocal tube insert  28  can be designed in several ways including as a permanent retrofit or a temporary retrofit that could be removed or replaced. Further, the draft tube insert may be made from many materials of construction including, but not limited to, reinforced concrete; metals of various types; wood; and reinforced or non-reinforced synthetic material (for example, plastics), to name a few. 
       FIG. 3  shows the flow characteristics of a convention draft tube system. Turbine  34  generates power from water flow that exits through the draft tube  39 . The flow rate remains constant where A i    36  is the draft tube cross sectional area closest to the turbine, and A o    37  is the cross sectional area farthest from the turbine. Notably, velocity v i    35  is substantially higher than v 0    38  demonstrating that the draft tube decreases velocity of water exiting turbine  34 . 
       FIG. 4  shows a power system  40  having conventional turbines with draft tube  44  retrofitted with tube insert  42  as shown before full insertion, thereby reducing the old diameter  46  of the draft tube to new diameter  48  which increases the velocity of the exiting water. 
     Tube insert  42 , in a preferred embodiment, is designed to matably insert into draft tube  44  as shown in  FIG. 4  with similar outside dimensions to match the inside dimensions of draft tube  44 . 
       FIG. 5  shows a power system  50  for converting river flow through turbines to electrical energy. Turbines  52  are placed in a conventional manner whereby flow velocity v 1    54  is higher than flow velocity v 0    56 . Without the additional of tailrace walls, the kinetic energy at the draft tube dissipates radially outward proportional to the following equation: KE=½ mv 2 . 
     Since velocity is directly proportional to the inverse of the square of the distance from the draft tube, flow velocity v 1    54  is significantly higher than flow velocity v 0    56 . Therefore, power potential for hydrokinetic turbine  58  is reduced and inefficiently low. To increase the flow characteristics for the hydrokinetic turbine, tailrace walls may be preferably placed at the output of the draft tubes. 
     By inserting a wall in between each draft tube outlet, the kinetic energy of the water is forced into a more constant cross sectional channel which also has the effect of preventing or reducing the rate of the dissipation of kinetic energy from the water resulting in higher water velocities (higher kinetic energy) further downstream. Another enhancement to the insertion of walls in between the draft tube outlets is to install a floor below the draft tube outlets that extends downstream with the walls that have been installed creating a channel. By keeping the cross sectional area of the channel for the flowing water relatively constant, additional increases in the kinetic energy of the water can be obtained which increases the quantity of power generated by the hydrokinetic system. 
       FIG. 6  shows a power system  60  with conventional turbine room  64  for generating hydroelectric power from a river. As water flows through the turbines out the draft tube outlets, it is channeled by tailrace walls  66  that direct the water and increase velocity of flow to high power potential hydrokinetic turbines  68 . By doing so, the tailrace walls greatly increase the velocity of downstream flow to the hydrokinetic turbines thereby generating significantly higher amounts of power. 
       FIG. 7  shows an embodiment of the tailrace and channel walls and or floors such as vertical wall  70  and box wall  72 . The combination of walls and floors of the channel can be in many shapes including, but not limited to, vertical parallel walls only; walls and floor that create a “U” shape; walls and floor that create a “U” shape, but converge the further downstream from the draft tube to keep the kinetic energy high; walls that form a “V”; walls that are fully submerged; and walls that are partially submerged. 
     The optimal system for the highest possible hydrokinetic power generation system downstream of a dam for a given dam design may be a combination of both a modified draft tube as shown in  FIG. 2  and tailrace and channel walls and or floors as shown in  FIGS. 6 and 7 . 
     While the invention has been described in connection with several preferred embodiments, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the issued claims.