Abstract:
A fluid energy harvester, including a housing having at least one port and an outlet, and the housing defining at least one fluid passageway therein. The fluid energy harvester also includes a converter disposed within the housing and configured to convert at least a portion of potential energy in an exhaust fluid, a generator operably coupled to the converter and configured to generate an electrical current from the converter, a charging controller electrically coupled to the generator, and a storage medium electrically coupled to the generator and configured to store the electrical current generated by the generator. The fluid energy harvester further includes a nozzle configured to control a flow of the exhaust fluid.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a non-provisional application based upon U.S. provisional patent application Ser. No. 62/314,527, entitled “ACTUATOR EXHAUST FLUID ENERGY HARVESTER”, filed Mar. 29, 2016, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0002]    The present invention relates to energy harvesters, and, more particularly, to an exhaust fluid energy harvester in a motive system that generates electrical energy in order to store the electrical energy and/or use it to power an external load. 
       2. Description of the Related Art 
       [0003]    Actuators are mechanical or electromechanical devices which convert energy into mechanical motion. Often, mechanical actuators are powered with a compressed fluid which alternately enters and exits a cylindrical volume to act against a movable piston and rod assembly. The rod is extended by fluid pressure acting on one face of the piston and is retracted when fluid acts on the opposing face of the piston. To affect motion, the face of the piston upon which motive fluid pressure acts must be continuously supplied with pressurized fluid from a supply, while any pressurized fluid acting on the opposing face of the piston is continuously exhausted so as to maintain a continuous pressure differential between the two faces. The motive force produced on the piston is proportional to the magnitude of this pressure differential. 
         [0004]    It is often advantageous to produce as large a motive force as possible by exhausting the fluid present on the exhaust side of the piston to as low a pressure as possible; typically, to the ambient pressure of the environment in which the actuator is operated. As the actuator cycles, moving the piston and rod attached to the piston in a reciprocating motion, the supply side of the piston on a given stroke of the piston and rod becomes the exhaust side of the piston on the successive stroke. The fluid on the supply side of piston is ideally maintained at the full pressure of the fluid supply in order to produce the maximum work output from the actuator. At the completion of a stroke, the volume of fluid on the supply side of the piston remains at full supply pressure until the fluid is subsequently exhausted during the reciprocal successive stroke. This volume of fully pressurized fluid contains a quantity of potential energy proportional to the volume and pressure of the fluid. As the fluid is exhausted to the low pressure environment or other low pressure sump, the potential energy stored in the compressed fluid is lost from the motive system. This loss of energy degrades the efficiency of the system. 
         [0005]    What is needed in the art is a cost-effective device to recoup as much of the lost energy as is practical, so as to increase the overall efficiency of the motive system. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a fluid energy harvester for harvesting electrical energy from the compressed fluid present on the exhaust side of an actuator piston. The electrical energy can be used to perform other useful work elsewhere in the actuator system. 
         [0007]    The present invention in one form is directed to a fluid energy harvester, including a housing having at least one port and an outlet, and the housing defining at least one fluid passageway therein. The fluid energy harvester also includes a converter disposed within the housing and configured to convert at least a portion of potential energy in an exhaust fluid, a generator operably coupled to the converter and configured to generate an electrical current from the converter, a charging controller electrically coupled to the generator, and a storage medium electrically coupled to the generator and configured to store the electrical current generated by the generator. The fluid energy harvester further includes a nozzle configured to control a flow of the exhaust fluid. 
         [0008]    The present invention in another form is directed to an actuating system. The actuating system includes a fluid supply for supplying a fluid and an actuator. The actuator includes a piston having a piston rod, a first piston face, and a second piston face. The actuator further includes a piston housing substantially encasing the piston and defining a first volume and a second volume respectively adjacent to the first piston face and the second piston face, and a first port and a second port fluidly connected respectively with the first volume and the second volume of the piston housing. The actuating system also includes a valve fluidly connected to the fluid supply and the actuator, and having an exhaust port, and a fluid energy harvester fluidly connected to the actuator. The fluid energy harvester includes a housing having a first port, a second port, and an outlet, and the housing defining at least one fluid passageway therein. The fluid energy harvester also includes a converter disposed within the housing and configured to convert at least a portion of potential energy in the fluid exhausting from the actuator, a generator operably coupled to the converter and configured to generate an electrical current from the converter, a charging controller electrically coupled to the generator, and a storage medium electrically coupled to the generator and configured to store the electrical current generated by the generator. The fluid energy harvester further includes a moveable needle disposed within the at least one passageway of the housing and configured to control a flow of the fluid. 
         [0009]    The present invention in yet another form is directed to an actuating system. The actuating system includes a fluid supply for supplying a fluid and an actuator. The actuator includes a piston having a piston rod, a first piston face, and a second piston face. The actuator also includes a piston housing substantially encasing the piston and defining a first volume and a second volume respectively adjacent to the first piston face and the second piston face, and a first port and a second port fluidly connected respectively with the first volume and the second volume of the piston housing. The actuating system also includes a valve fluidly connected to the fluid supply and the actuator, and having an exhaust port, and a fluid energy harvester fluidly connected to the actuator. The fluid energy harvester includes a housing having a port and an outlet, and the housing defining at least one fluid passageway therein. The fluid energy harvester also includes a converter disposed within the housing and configured to convert at least a portion of potential energy in the fluid exhausting from the actuator, a generator operably coupled to the converter and configured to generate an electrical current from the converter, a charging controller electrically coupled to the generator, and a storage medium electrically coupled to the generator and configured to store the electrical current generated by the generator. The fluid energy harvester further includes a moveable needle associated with the at least one passageway of the housing and configured to control a flow of the fluid. 
         [0010]    An advantage of the present invention is that greater efficiencies of a motive system can be achieved. 
         [0011]    Another advantage of the present invention is that harvested energy which would have been lost in a traditional motive system can be stored or used to perform work elsewhere in the motive system. 
         [0012]    Yet another advantage of the present invention is that motion of the actuator can be controlled while simultaneously harvesting energy from the exhaust fluid. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following descriptions of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0014]      FIG. 1  is a schematic representation of a typical actuator known in the art; 
           [0015]      FIGS. 2A-2B  are schematic representations of the typical actuator as shown in  FIG. 1 , illustrating the movement of the piston and rod relative to the housing; 
           [0016]      FIGS. 3A-3B  are schematic representations of an actuator system incorporating an energy harvester according to the present invention; 
           [0017]      FIG. 4  is a schematic diagram illustrating an energy harvester according to the present invention; 
           [0018]      FIG. 5  is an exploded view of an embodiment of an energy harvester according to the present invention; 
           [0019]      FIG. 6  is a top view of the energy harvester as shown in  FIG. 5 ; 
           [0020]      FIG. 7  is a cross sectional view of the energy harvester as shown in  FIG. 6  taken across line  7 - 7 ; 
           [0021]      FIG. 8  is a side view of the energy harvester as shown in  FIG. 5 ; 
           [0022]      FIG. 9  is a cross sectional view of the energy harvester as shown in  FIG. 8  taken across line  9 - 9 ; 
           [0023]      FIG. 10  is a side view of the energy harvester as shown in  FIG. 5 ; 
           [0024]      FIG. 11  is a cross sectional view of the energy harvester as shown in  FIG. 10  taken across line  11 - 11 ; 
           [0025]      FIG. 12  is an exploded view of another embodiment of an energy harvester according to the present invention; 
           [0026]      FIG. 13  is a top view of the energy harvester as shown in  FIG. 12 ; 
           [0027]      FIG. 14  is a cross sectional view of the energy harvester as shown in  FIG. 13  taken across line  14 - 14 ; 
           [0028]      FIG. 15  is a side view of the energy harvester as shown in  FIG. 12 ; 
           [0029]      FIG. 16  is a cross sectional view of the energy harvester as shown in  FIG. 15  taken across line  16 - 16 ; 
           [0030]      FIG. 17  is an exploded view of another embodiment of an energy harvester according to the present invention; 
           [0031]      FIG. 18  is a top view of the energy harvester as shown in  FIG. 17 ; 
           [0032]      FIG. 19  is a cross sectional view of the energy harvester as shown in  FIG. 18  taken across line  19 - 19 ; 
           [0033]      FIG. 20  is a side view of the energy harvester as shown in  FIG. 17 ; and 
           [0034]      FIG. 21  is a cross sectional view of the energy harvester as shown in  FIG. 20  taken across line  21 - 21 . 
       
    
    
       [0035]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE INVENTION 
       [0036]    Referring now to  FIG. 1 , there is shown a schematic representation of a typical actuator  1  known in the art, in which the actuator rod  2  is extended and retracted by a pressurized fluid acting against the faces  3 A and  3 B of the piston  3 . Housing  4  guides rod  2  and encloses piston  3  to form volumes  5 A and  5 B adjacent to piston faces  3 A and  3 B, respectively. Flow controls  7  and  8  connect fluid lines  9 A and  9 B to double acting valve  10 . Valve  10  is able to connect lines  9 A and  9 B to either pressurized fluid supply  12  or exhaust  11 , depending on the position of the valve  10 . Flow controls  7  and  8  can be in the form of throttling devices  7 A and  8 A and check valves  7 B and  8 B, respectively. Throttling devices  7 A and  8 A can be adjusted to meter the flow rate of pressurized fluid passing through them. Check valves  7 B and  8 B are configured to allow fluid to flow freely through them when the fluid is moving to enter the actuator  1  (i.e. when moving from line  9  toward port  6 ), while completely blocking flow when the fluid exits the actuator  1  (i.e. when moving from port  6  toward line  9 ). In this fashion, fluid flow entering the actuator  1  can pass freely through the open check valve, bypassing the restriction to flow created by the throttling device, while flow exiting the actuator  1  is forced by the closed check valve to the flow restriction created by the throttling device. In the field of art, this arrangement is known as “meter out” speed control, with the adjustable flow rate imposed on the fluid exhausting from the actuator  1  by the appropriate throttling device controlling the speed of the piston  3  and the actuator rod  2 . 
         [0037]    Referring now to  FIG. 2A , there is shown a schematic operation of a typical actuator system known in the art, in which the actuator rod  2  is extending away from housing  4 . Pressurized fluid, flowing from supply  12 , is routed by valve  10  to line  9 B. Passing through open check valve  8 B, the fluid bypasses throttling device  8 A to enter port  6 B and fill volume  5 B. The fluid pressure acting against piston face  3 B acts to move the piston  3  and extend the attached actuator rod  2  away from housing  4 . Simultaneously, the pressurized fluid occupying volume  5 A exhausts through port  6 A toward flow control  7 . Closed check valve  7 B forces the exhaust flow to pass through throttling device  7 A, to govern the speed of the extending rod  2 . The exhaust flow from line  9 A passes through valve  10  to be exhausted to ambient pressure through exhaust port  11 . 
         [0038]    Referring now to  FIG. 2B , there is shown a schematic operation of the same actuator system shown in  FIG. 2A , but when the actuator rod  2  is retracting toward housing  4 . Pressurized fluid, flowing from supply  12 , is directed by valve  10  to line  9 A. Passing through open check valve  7 B, the fluid bypasses throttling device  7 A to enter port  6 A and fill volume  5 A. The fluid pressure acting against piston face  3 A acts to move the piston  3  and retract the attached actuator rod  2  toward housing  4 . Simultaneously, the pressurized fluid occupying volume  5 B exhausts through port  6 B toward flow control  8 . Closed check valve  8 B forces the exhaust flow to pass through throttling device  8 A, to govern the speed of the retracting rod  2 . The exhaust flow from line  9 B passes through valve  10  to be exhausted to ambient pressure through exhaust port  11 . 
         [0039]      FIGS. 3A and 3B  schematically show some of the possible locations at which an energy harvester  20  can be integrated into an actuator system. Although the invention is disclosed in conjunction with a pneumatic actuator producing a reciprocating linear motion, it is understood that the invention can also be applied to hydraulically powered actuators and actuators producing rotary or curvilinear motion. 
         [0040]      FIG. 3A  shows harvester  20  located adjacent to the ports  6 A,  6 B of actuator  1 . The harvester  20  can be configured to also incorporate the functions of flow control (check valve and throttling device) as shown in the harvester  20  located between port  6 B and line  9 B. The harvester  20  can also be added adjacent to a discrete flow control as shown in the harvester  20  located between port  6 A and line  9 A. Locating the harvester adjacent to ports  6 A,  6 B offers the possible benefit of increasing the amount of energy available from the exhaust flow for harvest, since energy is lost from the exhaust flow in the form of frictional heat generated between the flow and walls of the conduit conveying the flow, as the flow moves progressively away from the ports  6 A,  6 B. However, a harvester  20  located adjacent to ports  6 A,  6 B can only harvest energy from the actuator port to which it is attached, creating the disadvantage of requiring two harvesters  20  to be used in order to extract energy from the entire quantity of fluid exhausted from the actuator  1 . 
         [0041]      FIG. 3B  shows harvester  20  attached to the exhaust port  11  of valve  10 . Locating the harvester  20  in this position, offers the advantage of allowing a single harvester  20  to extract energy from the entire quantity of fluid exhausted from the actuator  1 , since both of the exhaust flows from both ports  6 A,  6 B of actuator  1  are alternately directed to common exhaust port  11  by valve  10 . Locating the harvester  20  at exhaust port  11  has the possible disadvantage of reducing the amount of energy available from the exhaust flow for harvest, since energy is lost from the exhaust flow in the form of frictional heat generated between the flow and walls of the conduit conveying the flow, as the flow moves progressively away from actuator ports  6 A,  6 B. 
         [0042]      FIG. 4  shows a schematic representation of the components of the energy harvesting system  20  according to the present invention. The energy harvesting system  20  provides energy to external load  25 . Energy is extracted from the exhaust fluid stream by converter  20 A, which converts a portion of the potential energy stored in the compressed exhaust fluid into mechanical motion. Generator  20 B generates an electrical current from the mechanical motion produced by converter  20 A. Charging controller  20 C directs the electrical current produced by generator  20 B into storage medium  20 D during periods when the power produced by generator  20 B exceeds the power demanded by external load  25 . Charging controller  20 C provides an electrical current from storage medium  20 D to external load  25  during periods when the power demanded by the external load  25  exceeds the power produced by generator  20 B. 
         [0043]    Converter  20 A can include any suitable means common in the art of converting fluid flow into mechanical motion. For example, impingement of the flow, either axially or tangentially, onto a bladed turbine can convert the fluid motion into rotation of the turbine. The action of a linear oscillating spring-mass positive volume displacement pump can be reversed so that the fluid flow produces a reciprocating linear motion. In a similar manner, an alternating-valve-oscillating-piston-positive-volume-displacement pump can be used to produce a reciprocating linear motion. The action of a Wankle rotary pump can be reversed to produce rotary motion. The Bernoulii Effect can be exploited to produce either a fluttering flexion or oscillating torsional twisting of a reed over which the fluid flow is directed. 
         [0044]    Any means known in the art can be used to perform the function of Generator  20 B. For example, the action of an electric motor can be reversed to convert mechanical rotation into electrical current. Reciprocating linear motion can be converted into electrical current by the action of a magnet moving relative to a helical coil formed by an electrical conductor encircling the magnet. Flexion of a reed can be converted into an electrical current through a piezoelectric film laminated onto the reed. Laminated piezoelectric film or the reversed action of an electric motor are suitable to convert the torsional twisting of a reed into an electrical current. 
         [0045]    Charging controller  20 C can include an electrical integrated circuit (IC) specifically designed for the task, such as the bq25504 IC which is manufactured for energy harvesting applications by Texas Instruments Corporation. 
         [0046]    Storage medium  20 D can include any suitable combination of rechargeable batteries, super-capacitors, and/or conventional capacitors. 
         [0047]      FIG. 5  shows an exploded isometric view, and  FIGS. 7 and 9  show section views, of a first embodiment of energy harvester  20 , intended to be located between port  6 B and line  9 B as shown in  FIG. 3A . Bearing bushing  31  is disposed into a mating bore in housing  30 . Shaft  33  is bonded to turbine  32  so that rotation of turbine  32  causes a like rotation of shaft  33 , with one end of shaft  33  supported by bearing bushing  31 . The opposing end of shaft  33  is supported by bearing bushing  34 . Bushing  34  is disposed into a mating bore in plug  36 . The actions of bearing bushings  31  and  34  allow shaft  33  and turbine  32  to rotate freely, while preventing axial translation of the shaft  33  and turbine  32  between plug  36  and housing  30 . O-ring seal  35  seals the periphery of plug  36  to prevent the ingress of moisture past the plug  36 . The input shaft of electrical generator  37  is bonded to one end of shaft  33  so that rotation of the shaft  33  by turbine  32  causes a like rotation of the generator input shaft. The electrical output terminals of generator  37  are electrically connected to printed circuit board (PCB)  38 . Also, electrically connected to PCB  38  are charging controller IC  39  and storage super-capacitor  40 . Turbine  32 , generator  37 , charging controller IC  39 , and storage super-capacitor  40  perform the actions respectively of converter  20 A, generator  20 B, charging controller  20 C, and storage medium  20 D, which are shown schematically in  FIG. 4 . Electrical connector  41  connects electrically to PCB  38  and provides a way of connecting harvester  20  to an external load, represented schematically as load  25  in  FIG. 4 . Elastomeric O-ring  42  is disposed within a bore in cover  43  so as to remove any physical space that might occur between generator  37  and cover  43  resulting from the dimensional variation of the components that comprise the harvester  20 . Threaded fasteners  44  physically attach cover  43  to housing  30 . An O-ring seal  45  is disposed within a complimentary recess in a needle  47  ( FIG. 9 ). Check seal  46  is disposed within a complimentary gland in needle  47 . One end of pin  48  is disposed within a mating bore in needle  47 . The opposing end of pin  48  passes through a bore in cap  50 . Pin  48  is constrained from radial movement by the bore in cap  50 , but the pin  48  is free to translate along the longitudinal axis of the cap  50 . The flange portion of cap  50  is disposed into a complimentary bore in housing  30 . Retaining ring  52  retains cap  50  within a mating bore in housing  30 , while O-ring seal  49  prevents the passage of pressurized fluid around the flange portion of cap  50 . Speed adjustment knob  53  threads onto cap  50 . Pin  54  is secured into a mating bore in knob  53  after the knob  53  is threaded on the cap  50  to prevent the knob  53  from subsequently being able to be completely unthreaded from cap  50 . O-ring seal  51 , seated within a complimentary gland in cap  50 , seals against knob  53  to prevent the egress of fluid around pin  48 . 
         [0048]    Arrows  60  in  FIGS. 9 and 11  show the direction of flow of pressurized fluid through harvester  20 . The housing  30  has at least one fluid passageway, for example, it may include four fluid passageways in the form of a passage  62 , a cavity  63 , a nozzle  64 , and a passage  65 . Passages  62  and  65  fluidly connect ports  61  and  66 , respectively, with the cavity  63 . The moveable needle  47  is associated with at least one fluid passageway of the housing  30 . In the present embodiment, the needle  47  is disposed within the cavity  63  and can be selectively adjusted with respect to and engaged with the nozzle  64  to adjust and/or close off fluid flow therethrough. In this manner, the needle  47  is configured to adjust a flow of the fluid as it can adjust fluid flow within cavity  63  and through nozzle  64 . 
         [0049]      FIG. 9  shows the operation of harvester  20  when exhaust fluid is flowing from port  6 B to line  9 B (see also  FIG. 3A ). Pressurized fluid enters port  61  in housing  30  and flows through passage  62  into cavity  63  and through the annular orifice formed between needle  47  and conical nozzle  64  in body  30 . Nozzle  64  directs the fluid flow to impinge upon the vanes of turbine  32  causing the turbine  32  to spin along with shaft  33 . The exhaust flow, depleted of kinetic energy by the action of impingement against the vanes of turbine  32 , subsequently exits housing  30  through outlet  67  and porous plug  55 , which is retained in a complimentary bore in housing  30 . Fluid pressure acting on the underside of check seal  46  causes the skirt of the check seal  46  to inflate radially outwards to seal against the walls of cavity  63 , preventing the flow of fluid through passage  65  and out of port  66  in housing  30 . The axial position of needle  47  relative to nozzle  64  determines the area of the annulus through which the fluid flows prior to exiting through the nozzle  64 , creating the ability to meter the flow rate of the exhaust flow through the harvester  20 . The axial position of knob  53  relative to cap  50  provides a means of externally adjusting the axial position of needle  47  relative to nozzle  64  by restricting the axial movement of pin  48  as fluid pressure acting on the underside of check seal  46  exerts a force to push needle  47  away from nozzle  64 . In this manner, needle  47 , pin  48 , cap  50 , knob  53 , and check seal  46  with body  30  form a throttling device and check valve which perform the function of the conventional speed controlling throttling device  8 A and check valve  8 B respectively, as shown schematically in  FIGS. 1 and 2 . 
         [0050]      FIG. 11  shows the operation of harvester  20  when supply fluid is flowing from line  9 B to actuator port  6 B (see also  FIG. 3A ). Pressurized fluid flowing from the supply  12  enters port  66  in housing  30  and flows through passage  65  into cavity  63 . The pressure of the fluid, acting on the topside of check seal  46 , causes the skirt of the check seal  46  to collapse, allowing the fluid to flow around the annular area formed between the periphery of the skirt and the walls of cavity  63 . Fluid pressure acting on the topside of check seal  46  and the top surface of needle  47  exerts a force to push needle  47  downwards until O-ring seal  45  seats against the bottom of cavity  63 , which prevents the flow of fluid through nozzle  64  (see also  FIG. 9 ). The flow exits cavity  63  through passage  62  and passes out of port  61  in housing  30  to supply port  6 B of actuator  1  with pressurized fluid. 
         [0051]      FIG. 12  shows an exploded isometric view, and  FIGS. 14 and 16  show section views, of a second embodiment of the energy harvester  20 , suitable for attachment to exhaust port  11  of valve  10  as shown in  FIG. 3B . Bearing bushing  131  is disposed into a mating bore in housing  130 . Shaft  133  is bonded to turbine  132  so that rotation of turbine  132  causes a like rotation of shaft  133 , with one end of shaft  133  supported by bearing bushing  131 . The opposing end of shaft  133  is supported by bearing bushing  134 . Bushing  134  is disposed into a mating bore in plug  136 . The actions of bearing bushings  131  and  134  allow shaft  133  and turbine  132  to rotate freely, while preventing axial translation of the shaft  133  and turbine  132  between plug  136  and housing  130 . O-ring seal  135  seals the periphery of plug  136  to prevent the ingress of moisture past the plug  136 . The input shaft of electrical generator  137  is bonded to one end of shaft  133  so that rotation of the shaft  133  by turbine  132  causes a like rotation of the generator input shaft. The electrical output terminals of generator  137  are electrically connected to printed circuit board (PCB)  138 . Also, electrically connected to PCB  138  are charging controller IC  139  and storage super-capacitor  140 . Turbine  132 , generator  137 , charging controller IC  139 , and storage super-capacitor  140  perform the actions respectively of converter  20 A, generator  20 B, charging controller  20 C, and storage medium  20 D, as shown schematically in  FIG. 4 . Electrical connector  141  connects electrically to PCB  138  and provides a way of connecting harvester  20  to an external load, represented schematically as load  25  in  FIG. 4 . Elastomeric O-ring  142  is disposed within a bore in cover  143  so as to remove any physical space that might occur between generator  137  and cover  143  resulting from the dimensional variation of the components that comprise the harvester  20 . Threaded fasteners  144  physically attach cover  143  to housing  130 . Needle  147  is disposed within a complimentary bore in cap  150  with a treaded portion of needle  147  engaging mating threads in cap  150 . In this manner, rotation of needle  147  relative to cap  150  causes needle  147  to move along the longitudinal axis of cap  150 . Retaining ring  148  prevents needle  147  from subsequently being able to be completely unthreaded from cap  150 . O-ring seal  151  is disposed within a complimentary gland in needle  147  and prevents the egress of fluid between the bore in cap  151  and the body of needle  147 . The flange portion of cap  150  is disposed into a complimentary bore in housing  130 . Retaining ring  152  retains cap  150  within a mating bore in housing  130 . 
         [0052]    Arrows  160  in  FIG. 16  show the direction of flow of pressurized exhaust fluid through harvester  20 . The housing  130  has at least one fluid passageway, for example, it may include three fluid passageways in the form of a passage  165 , a cavity  163 , and a nozzle  164 . Passage  165  fluidly connects port  166  with the cavity  163 . The moveable needle  147  is associated with at least one fluid passageway of the housing  130 . In the present embodiment, the needle  147  is partially disposed within the cavity  163  and can be selectively moved with respect to and engaged with the nozzle  164  to adjust and/or close off fluid flow therethrough. In this manner, the needle  147  is configured to adjust a flow of the fluid as it can adjust fluid flow within cavity  163  and through nozzle  164 . 
         [0053]    In operation, pressurized fluid enters port  166  in housing  130  and flows through passage  165  into cavity  163  and through the annular orifice formed between needle  147  and conical nozzle  164  in body  130 . Nozzle  164  directs the fluid flow to impinge upon the vanes of turbine  132  causing the turbine  132  to spin along with shaft  133 . The exhaust flow, depleted of kinetic energy by the action of impingement against the vanes of turbine  132 , subsequently exits housing  130  through outlet  167  and porous plug  155 , which is retained in a complimentary bore in housing  130 . 
         [0054]    The axial position of needle  147  relative to nozzle  164  determines the area of the annulus through which the fluid flows prior to exiting through the nozzle  164 . During operation of the harvester  20 , needle  147  is first rotated relative to cap  150 , which remains stationary relative to body  130 , to adjust the axial position of needle  147  so that needle  147  is fully retracted from nozzle  164 . Throttling devices  7 A and  8 A may be included and subsequently adjusted to obtain the desired extend and retract speeds of rod  2  of the actuator  1  (see also  FIGS. 1 and 2 ). Needle  147  is finally rotated relative to cap  150 , to reduce the annular area formed between needle  147  and nozzle  164 , until the reduction in area begins to reduce the extend and/or retract speed of actuator  1 . In this manner, exhaust fluid is caused to exit nozzle  164  at the highest flow speed practical without adversely altering the desired actuation speed of actuator  1 . Such high flow speed provides for an exhaust flow with a kinetic energy content as great as is possible, to provide for optimal energy transfer from the fluid to turbine rotor  132 . 
         [0055]      FIG. 17  shows an exploded isometric view, and  FIGS. 18 and 19  show section views, of a third embodiment of the energy harvester  20 , suitable for attachment to exhaust port  11  of valve  10  as shown in  FIG. 3B . Such an embodiment may be desirable as a lower cost alternative for those applications wherein optimization of the harvested energy is not required. Bearing bushing  231  is disposed into a mating bore in housing  230 . Shaft  233  is bonded to turbine  232  so that rotation of turbine  232  causes a like rotation of shaft  233 , with one end of shaft  233  supported by bearing bushing  231 . The opposing end of shaft  233  is supported by bearing bushing  234 . Bushing  234  is disposed into a mating bore in plug  236 . The actions of bearing bushings  231  and  234  allow shaft  233  and turbine  232  to rotate freely, while preventing axial translation of the shaft  233  and turbine  232  between plug  236  and housing  230 . O-ring seal  235  seals the periphery of plug  236  to prevent the ingress of moisture past the plug  236 . The input shaft of electrical generator  237  is bonded to one end of shaft  233  so that rotation of the shaft  233  by turbine  232  causes a like rotation of the generator input shaft. The electrical output terminals of generator  237  are electrically connected to printed circuit board (PCB)  238 . Also, electrically connected to PCB  238  are charging controller IC  239  and storage super-capacitor  240 . Turbine  232 , generator  237 , charging controller IC  239 , and storage super-capacitor  240  perform the actions respectively of converter  20 A, generator  20 B, charging controller  20 C, and storage medium  20 D, as shown schematically in  FIG. 4 . Electrical connector  241  connects electrically to PCB  238  and provides a way of connecting harvester  20  to an external load, represented schematically as load  25  in  FIG. 4 . Elastomeric O-ring  242  is disposed within a bore in cover  243  so as to remove any physical space that might occur between generator  237  and cover  243  resulting from the dimensional variation of the components that comprise the harvester  20 . Threaded fasteners  244  physically attach cover  243  to housing  230 . 
         [0056]    Arrows  260  in  FIG. 21  show the direction of flow of pressurized exhaust fluid through harvester  20 . The housing  230  has at least one fluid passageway, for example, it may include a fluid passageway in the form of a nozzle  264 , e.g., a fixed orifice nozzle. The dimensions of nozzle  264  are selectively chosen to control the velocity of fluid passing through the orifice so formed, creating the ability to meter the flow rate of the exhaust flow through the harvester  20 . 
         [0057]    In operation, pressurized fluid enters port  266  in housing  230  and flows through the orifice formed by conical nozzle  264  in body  230 . Nozzle  264  directs the fluid flow to impinge upon the vanes of turbine  232  causing the turbine  232  to spin along with shaft  233 . The exhaust flow, depleted of kinetic energy by the action of impingement against the vanes of turbine  232 , subsequently exits housing  230  through outlet  267  and porous plug  255 , which is retained in a complimentary bore in housing  230 . 
         [0058]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.