Abstract:
A sewer energy mill system is provided for converting kinetic energy possessed by the wastewater flowing through a sewer line into electrical energy. The system may be installed within a conventional existing manhole infrastructure of the sewer system or within a customized structure specifically designed to accommodate the system and installed into the sewer system

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to the hydropower generation of electricity in sewer lines and, more particularly, to a system capable of being installed in a sewer system for converting the kinetic energy of the fluid flowing through a sewer line into electrical energy. 
       BACKGROUND OF THE INVENTION 
       [0002]    In developed countries worldwide, most cities, villages and other areas of human population concentration have installed sewer systems to handle sanitary waste from homes, apartment buildings, office buildings, industrial complexes and other concentrations of human activity. The sanitary waste is diluted with water at its source and delivered through branch lines into a sewer system formed of a network of sewer lines. The sewer system generally includes a plurality of trunk lines that receive the wastewater from the branch lines and deliver that wastewater to a sewer main line that typically discharges into a sewage treatment plant. 
         [0003]    The sewer systems are designed such that the pre-treatment wastewater will flow from the multiplicity of sources through the branch lines, trunk lines and main lines to the sewage treatment plant. Generally, this is accomplished by providing a downhill declination to each of these lines in the direction of flow through the lines whereby the flow passes through the sewer system under the force of gravity. At selected locations in the sewer lines, pump stations may be provided to pump the wastewater from a lower elevation to a higher elevation from which the pre-treatment wastewater will continue to flow downhill under the force of gravity. Therefore, the wastewater flowing through the various sewer lines of the sewer system possesses kinetic energy. 
       SUMMARY OF THE INVENTION 
       [0004]    A system is provided for converting kinetic energy possessed by the wastewater flowing through a sewer line into electrical energy. The system may be installed within a conventional existing manhole infrastructure of the sewer system or within a customized structure specifically designed to accommodate the system and installed into the sewer system. 
         [0005]    The sewer energy mill system includes an energy extracting device mounted to a rotatable shaft, an alternator for generating electricity having a rotatable shaft, a gearing mechanism connecting the shaft of the energy extracting device to the shaft of the alternator for rotating the shaft of the alternator, and an inlet channel configured to be installed within the sewer line upstream with respect to wastewater flow of the energy extracting device, the inlet channel having a throat defining a variable flow area. The energy extracting device is positioned whereby wastewater flowing through the sewer line impacts the energy extracting device thereby rotating the shaft of the energy extracting device. The system may also include an inflatable bladder disposed in the sewer line upstream with respect to wastewater flow of the energy extracting device. 
         [0006]    In an embodiment, the energy extracting device comprises a paddlewheel drum having a plurality of outwardly extending paddles. In an embodiment, the energy extracting device comprises a turbine having a plurality of blades 
         [0007]    The system may also include a controller operative to selectively vary the variable flow area of the throat of the inlet channel. The controller may also be operative to selectively inflate the inflatable bladder. At least one flow velocity sensor may be associated with the controller for sensing a flow velocity of the wastewater approaching the paddlewheel drum and transmitting a signal indicative of the sensed flow velocity to the controller. At least one flow depth sensor may be associated with the controller for sensing a depth of the flow of the wastewater approaching the paddlewheel drum and transmitting a signal indicative of the sensed flow depth to the controller. At least one pressure sensor may be associated with the controller for sensing the head pressure of the flow and transmitting a signal indicative of the sensed head pressure to the controller. 
         [0008]    In an embodiment, the controller compares the sensed flow velocity to a design threshold velocity, selectively decreases the flow area of the throat of the inlet channel if the sensed flow velocity is less than the design threshold velocity, and selectively increases the flow area of the throat of the inlet channel if the sensed flow velocity exceeds the design threshold velocity. In an embodiment, the controller compares the sensed flow depth to a design threshold depth and selectively inflates the bladder if the sensed flow depth exceeds the design threshold depth. In an embodiment, the controller adjusts the flow area of the throat of the inlet channel inversely to the sensed head pressure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a further understanding of the disclosure, reference will be made to the following detailed description which is to be read in connection with the accompanying drawing, where: 
           [0010]      FIG. 1  is an elevation view, partly in section, of the sewer energy mill disclosed herein positioned within a manhole of a sewer system; 
           [0011]      FIG. 2  is an elevation view, partly in section, of the sewer energy mill of  FIG. 1  substantially as viewed from line  2 - 2  of  FIG. 1 ; and 
           [0012]      FIG. 3  is a schematic diagram illustrating an exemplary embodiment of the control system of the sewer energy mill disclosed herein. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring initially to  FIGS. 1 and 2 , there is depicted an exemplary embodiment of a sewer energy mill system, designated generally as  10 , disposed in chamber  22  of a conventional manhole structure  20  opening into a sewer line  24  of a conventional sewer system. The sewer energy mill system  10  constitutes a system for converting the kinetic energy of wastewater flowing through the sewer line  24  into electrical energy. The term wastewater as used herein is to be understood to include sanitary wastewater per se, as well as mixed sewer line wastewater flows, for example mixed sanitary wastewater and storm system drainage flows. The generated electricity may be supplied to an electric power grid for distribution or may be supplied to a dedicated facility or for a dedicated use or to a battery, a capacitor or other storage device for subsequent delivery to an electric power grid or to a dedicated device or use. 
         [0014]    The sewer energy mill system  10  includes an energy extracting device  40  and an alternator  30  for generating electricity and operatively connected to the energy extracting device. The sewer energy mill system  10  will be further discussed and described herein with reference to the depicted embodiment of the sewer energy mill system  10 , wherein the energy extracting device  40  comprises a paddlewheel drum. However, it is to be understood that in other embodiments, the energy extracting device  40  could comprise a water turbine having a plurality of paddles mounted to a rotatable shaft or other device for extracting energy from the momentum of flowing water for rotating a shaft to which the device is mounted. 
         [0015]    The paddlewheel drum  40  is mounted to a rotatable shaft  42  that is disposed along a central axis of the paddlewheel drum  40 . The shaft  42  extends across the manhole chamber  22  and the respective ends of the shaft  42  are supported in rails  28  extending generally vertically on diametrically opposite sides of the wall of the manhole structure  20 . The paddlewheel drum  40  also includes a plurality of paddles  44  extending radially outward from the paddlewheel drum  40 . The paddles  44  are distributed about the circumference of the paddlewheel drum  40  at equally spaced intervals. The shaft  42  of the paddlewheel drum  40  is positioned within the manhole structure  20  such that paddles  44  on a lower portion of the paddlewheel drum  40  extend into the channel  25  of the sewer line  24  at the bottom of the manhole chamber  22 . Each paddle  44  has a generally semi-circular shape, the number and size of the paddles  44  being selected for maximum wastewater flow impact to the paddlewheel drum  40  to allow for maximum transfer of kinetic energy into rotational energy to the paddlewheel drum  40 . 
         [0016]    The alternator  30  has a rotatable shaft  32  that extends across the manhole chamber  22  with the respective ends of the shaft  32  being supported for rotation from the wall of the manhole structure  20 . The shaft  32  of the alternator  30  is operatively connected to the paddlewheel drum  40  so as to be driven in rotation as the paddlewheel drum  40  rotates. Rotation of the shaft  32  results in electric current being output by the alternator  30 . 
         [0017]    A drive mechanism  50  is provided for operatively connecting the shaft  32  of the alternator  30  to the shaft  42  of the paddlewheel drum  40 . For example, as depicted in the drawing, the drive mechanism  50  may comprise a gearing mechanism that includes a drive gear  52  mounted on the shaft  42  of the paddlewheel drum  40 , a driven gear  54  mounted on the shaft  32  of the alternator  30 , and a drive belt or chain  56  to transmit rotational force from the drive gear  52  to the driven gear  54 . The drive gear  52  has a diameter that is several times greater than the diameter of the driven gear  54 , whereby the shaft  32  of the alternator  30  will be driven at a greater rotational speed than the rotational speed at which the shaft  42  of the paddlewheel drum  40  rotates. It is to be understood, however, that the drive mechanism  50 , rather than having a belt or chain drive, could constitute a series of intermeshing gears linking the drive gear  52  on the shaft  42  to the driven gear  54  on the shaft  32  of the alternator  30 . It is also to be understood that the shaft  32  of the alternator  30  could be operatively connected to the shaft  42  of the paddlewheel drum  40  by a direct drive arrangement, rather than through a gearing mechanism. 
         [0018]    In operation, as the sewer wastewater passing through the sewer line  24  traverses the channel  25  at the bottom of the manhole chamber  22 , the force of the sewer wastewater flowing through the channel  25  against the paddles  44  causes the paddlewheel drum  40  to rotate together with the paddlewheel shaft  42  and the drive gear  52  mounted thereto. The rotation of the drive gear  52  is transmitted to the driven gear  54  by the belt or chain  56  thereby causing the shaft  32  of the alternator  30  to rotate. The rotation of the shaft  32  results in the generation of electric current in the alternator  30 . In this manner, a portion of the kinetic energy of the sewer wastewater is recovered and effectively converted to electrical energy. The generated electric current may be delivered through a cable (not shown) to an electric power grid for distribution or may be supplied to a dedicated facility or for a dedicated use or to a battery, a capacitor or other storage device. 
         [0019]    The sewer energy mill system  10  may also include an inlet channel  60  having variable flow area throat  62  installed within the sewer line  24  upstream with respect to wastewater flow of the paddlewheel drum  40 . The inlet channel  60  receives the wastewater flow flowing from the sewer line  24  into channel  25  and redirects the received wastewater flow toward the paddlewheel drum  40  to more effectively impact the paddles  44 . If a different energy extracting device were employed, for example a water turbine, the inlet channel  60  would be arranged to most effectively direct the wastewater flow into that energy extracting device. The inlet channel  60  defines a convergent passage  64  extending from the inlet end of the inlet channel  60  to throat  62 . The inlet channel  60  may also define a divergent passage  66  extending downstream from the throat  62  to the outlet end of the inlet channel  60 . In an embodiment, the inlet channel  60  may comprise a venturi having a variable throat area. 
         [0020]    Additionally, the sewer energy mill  10  may include a selectively inflatable bladder  70  disposed within the sewer line  24  upstream with respect to the inlet channel  60 . The bladder  70  may be mounted to the crown (i.e. roof) of the sewer line  24 , for example as depicted in  FIG. 1 , and maintained in a deflated state during normal levels of wastewater flow. During conditions when the level of the wastewater flow becomes higher than a design threshold depth for operation of the energy mill system  10 , the bladder  70  may be inflated to partially block the flow passage defined by the sewer line  24 , thereby controlling the level of the wastewater flow received at the inlet channel  60 . The bladder  70  may, for example, be made of rubber or other elastomeric material. 
         [0021]    Referring now to  FIG. 3 , there is depicted schematically an exemplary embodiment of a control system  80  operatively associated with the sewer energy mill system  10 . The control system  80  includes a controller  82  and a plurality of sensors, including at least one flow velocity sensor  92  and at least one flow depth sensor  94 . A pressure sensor  96  may also be included. The controller  80  comprises a microprocessor  82  and its associated memory  84 , an input/output interface  85 , including an analog-to-digital converter  86 , and drive circuits  88  for receiving commands from the microprocessor  82  and in turn controlling various components of the sewer energy mill system  10 . The flow velocity sensor  92  measures and transmits a signal indicative of the flow velocity of the wastewater entering or within the flow channel  25 . The pressure sensor  96  measures and transmits a signal indicative of the water pressure. The flow velocity sensor  92  and the pressure sensor  96  may be positioned in the sewer line  24  upstream of the bladder  70  (so positioned designated as  92 A,  96 A in  FIG. 1 ) or at or near the entrance to the flow channel  25  (so positioned designated as  92 B,  96 B in  FIG. 1 ) or within the flow channel  25 , but upstream of the point at which the wastewater impacts the paddlewheels  44 . The flow depth sensor  94  measures and transmits a signal indicative of the depth of the wastewater flowing through the flow channel  25 . The flow depth sensor  94  may be positioned within the sewer line  24  upstream of the flow channel  25  and generally upstream of the bladder  70  as illustrated in  FIG. 1 . 
         [0022]    The controller  80  receives the signal indicative of wastewater flow velocity from the flow velocity sensor  92  and the signal indicative of the depth of the wastewater from the flow depth sensor  94  through the input/output interface  85  wherein any received analog signals are converted by the analog-to-digital converter  86  to digital signals. The controller  80  processes the received signals and determines what action, if any, is necessary to maximize electricity generation. For example, if the sensed wastewater flow velocity is slower than necessary to maximize electricity generation, the controller  80  will further close the throat  62  of the inlet channel  60  thereby reducing the flow area through the throat  62  of the inlet channel  60  to increase the wastewater flow velocity and accelerate the flow of wastewater into the paddles  44  to increase the rotational speed of the paddlewheel drum  40 . Conversely, if the sensed flow velocity exceeds a design threshold velocity, which if exceeded could cause the paddlewheel drum  40  to stall or cease rotation, the controller  80  will further open the throat  62  of the inlet channel  60  to increase the flow area through the inlet channel  60  to decrease the wastewater flow velocity through the channel  25 . 
         [0023]    Additionally, if the sensed flow depth of the wastewater through the channel  25  is outside a design depth range, the controller  80  may adjust the inflation of the inflatable bladder  70 . If the sensed flow depth of the wastewater through the channel  25  is above an upper threshold depth of the design depth range, the controller  80  will inflate the inflatable bladder  70  to hold back wastewater flow through the sewer line  24  upstream of the inlet channel  60 . The inflated bladder  70  in effect acts like a dam by reducing the flow area through which wastewater may pass into the inlet channel  60 , thereby increasing the head pressure and causing the depth of the wastewater in the sewer line  24  upstream of the bladder  70  to increase. The increase in the depth of the wastewater flow upstream of the bladder  70  results in an increase in head pressure on the wastewater flow entering the inlet channel  60 , which will have the effect of increasing the flow velocity of the wastewater flow entering the inlet channel  60 . The controller  80  will adjust the throat  62  of the inlet channel  60  as necessary in the manner discussed hereinbefore to ensure that the flow velocity does not exceed the design threshold velocity. 
         [0024]    The sewer energy mill system  10  may be designed such that the paddlewheel drum  40  (or other energy extracting device), the alternator  30  and the drive mechanism  50  may be pre-assembled into a supporting manhole structure  20  to form a module that may be installed in place into a sewer system as a single unit. Further, the paddlewheel  40  (or other energy extracting device) and the alternator  30  may be mounted within a manhole structure such that the paddlewheel drum  40 , the alternator  30  and the drive mechanism  50  may be inserted and extracted from the manhole structure  20  as a modular unit. For example, in the embodiment of the sewer energy mill  10  depicted in  FIGS. 1 and 2 , the respective ends of the shaft  32  of the alternator  40  and the respective ends of the shaft  42  of the paddlewheel drum  40  are supported in rails  28  extending generally vertically on diametrically opposite sides of the wall of the manhole structure  20 . The respective ends of the shafts  32  and  42  are so engaged with the rails  28  as to permit the shaft ends to translate upwardly and downwardly within the rails  28 . 
         [0025]    In this manner, the paddlewheel drum  40 , the alternator  30  and the drive mechanism  50  may be lowered into position and lifted out of the manhole structure  20  as a modular unit. Additionally, the paddlewheel  40 , the alternator  30  and the drive mechanism  50  may be raised within the manhole structure  20  as a modular unit, thereby extracting the paddlewheel drum  40  from the channel  25  in the event that the wastewater flow through the sewer line  24  becomes so excessive as to risk damage to the energy extracting device. The paddlewheel  40 , the alternator  30  and the drive mechanism  50  may be partially withdrawn, as a modular unit, upwardly a selective distance during a high flow condition that does not necessitate full withdraw to prevent damage to the system. This variable extraction permits the modular unit to be selectively raised such that a portion of the paddlewheel remains in the flow stream, thereby still providing drive power for rotating the alternator for electric power generation, albeit likely at a reduced power output. In an embodiment, at least one depth sensor  94 L may be installed in the manhole chamber  22  at least one preselected distance above the crown of the sewer line to sense the raise of wastewater up the manhole chamber and transmit a signal to the controller  80  indicative of the raise of wastewater to the level of that preselected distance up the manhole shaft. The controller  80  may be programmed to initiate a full or a variable extraction of the modular unit in response to the receipt of a signal from the at least one depth sensor  94 L or from multiple depth sensors positioned at different preselected distances up the manhole chamber  22 . 
         [0026]    Additionally, velocity, depth and pressure sensors,  92 U,  94 U,  96 U may be located more remotely upstream of the bladder  70  for providing information regarding upstream wastewater flow conditions to the controller  80 . Inclusion of such more remotely located upstream sensors would enable the controller  80  to monitor upstream flow conditions and take protective action in the event that a potentially excessive wastewater flow condition, such as a surcharge condition, is detected. In a surcharge condition, wastewater flow through the main sewer line  24  becomes so excessive that wastewater backs up into lateral sewer lines entering the main sewer line  24  upstream of the manhole structure  20 . In the event that a potential surcharge condition is detected, the controller  80  can extract the paddlewheel drum  40  (or other energy extracting device) from the flow channel  25  thereby preventing damage thereto and also clearing the flow channel  25  so that the paddlewheel drum  40  does not obstruct wastewater flow during the existence of the surcharge condition. 
         [0027]    One or more gated wastewater bypass lines,  124 , may be included in connection with the sewer energy mill system  10  to provide for establishing a flow path through which some of the wastewater flow may be diverted rather than flowing through the channel  25  during excessive wastewater flow conditions, thereby obviating and at least delaying the need to extract the paddlewheel drum  40  from the flow channel  25 . The bypass lines  124  tap into the sewer line  24  upstream of the inlet channel  60  to receive wastewater flow when opened to flow and reenter the sewer line  24  downstream of the flow channel  25 , thereby bypassing the waterwheel drum  40 . The gated bypass lines  124  may also be selectively opened when necessary to bypass a portion of the wastewater flow around the paddlewheel drum  40  to maintain operation of the sewer energy mill system  10  at optimal efficiency. In an embodiment, an additional modular sewer energy mill system  10  (not shown) may be selectively positioned with respect to the at least one wastewater bypass lines  124 , or if desired each of the bypass lines  124 , for converting the kinetic energy of wastewater flowing through the at least one wastewater bypass line  124  into electrical energy. 
         [0028]    As noted previously, in other embodiments, the energy extracting device could comprise a water turbine having a plurality of paddles mounted to a rotatable shaft, such as for example, but not limited to, a Pelton wheel, or other device for extracting energy from the momentum of flowing water for rotating a shaft to which the device is mounted. In general, the efficiency of the energy extracting device in the sewer energy mill system  10  depends upon the wastewater head pressure and the wastewater velocity delivered to the energy extracting device. The selection of the particular energy device employed would depend upon expected wastewater flow conditions including available water pressure head, available wastewater mass flow rate, and available wastewater velocity. Also as noted previously, various drive mechanisms may be employed for transmitting rotation of the shaft of the energy extracting device into rotation of the shaft of the alternator. 
         [0029]    The terminology used herein is for the purpose of description, not limitation. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as basis for teaching one skilled in the art to employ the present invention. Those skilled in the art will also recognize the equivalents that may be substituted for elements described with reference to the exemplary embodiments disclosed herein without departing from the scope of the present invention. 
         [0030]    While the present invention has been particularly shown and described with reference to the exemplary embodiment as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications, some of which may have been alluded to herein, may be made without departing from the spirit and scope of the invention. It is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims.