Abstract:
Briefly stated, in accordance with the present subject matter, a generator system is provided. The assembly includes a turbine to be driven by exhaust air and a casing surrounding the turbine. The exhaust air issues from an exhaust structure. The turbine and the casing are each supported independently of the exhaust structure by a support structure. A generator is mechanically coupled to the turbine. The support structure is proportioned to mount the generator system in a selected juxtaposition with a preselected exhaust structure. A generator provides power to an output conductor. Power conditioning apparatus may be included in the system or may be located remotely.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 13/107,938, entitled “Green Power Generator Device,” filed on May 15, 2011 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present subject matter relates to a generator system which reuses air exiting from an exhaust port. 
     2. Related Art 
     The push toward “green technology” has led to greater emphasis on recovering energy that would previously have gone to waste. Air issuing from exhaust fans is the source in many schemes. 
     United States Patent Application Publication Number 2011/0089701 discloses a system in which vertically flowing exhaust air from an axial fan is directed at a turbine having a horizontally disposed access which is supported on an exhaust port. The turbine is in the envelope of a right circular cylinder. This construction cannot be efficiently manufactured to intercept a common form of exhaust such as an axial fan. A smaller cylinder will intercept only a portion of the flow. A cylinder large enough to intercept the flow will require more energy to rotate. 
     United States Patent Application Publication Number 2010/0244455 discloses a square air conditioning unit providing a vertical airflow exhaust. An assembly in a housing sits on and it covers the air conditioner. The assembly contains a turbine. Due to this construction, the housing will create back pressure on the exhaust airflow, decreasing efficiency. 
     SUMMARY 
     The present subject matter is directed to a generator system which reuses exhaust air in an efficient manner and which can be constructed efficiently to meet the requirements of many architectural contexts. 
     Briefly stated, in accordance with the present subject matter, a generator system is provided. The assembly includes a turbine to be driven by exhaust air and a casing surrounding the turbine. The exhaust air issues from an exhaust structure. The turbine and the casing are each supported independently of the exhaust structure by a support structure. A generator is mechanically coupled to the turbine. The support structure is proportioned to mount the generator system in a selected juxtaposition with a preselected exhaust structure. A generator provides power to an output conductor. Power conditioning apparatus may be included in the system or may be located remotely. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present subject matter may be further understood by reference to the following description taken in connection with the following drawings: 
         FIG. 1  is a diagram illustrating an installation incorporating the present subject matter; 
         FIGS. 2 ,  3 , and  4  are respectively an isometric view, a cross sectional view, and a partial detailed isometric view of a first embodiment driven by the exhaust of an axial fan; 
         FIGS. 5 ,  6 , and  7  are respectively an isometric view, a cross sectional view, and a partial detailed isometric view of a first embodiment driven by the exhaust of a radial fan; and 
         FIG. 8  is a plan view of embodiment in which a plurality of generator systems are connected to a single power conditioning circuit. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagram illustrating a building installation  10  incorporating the present subject matter. Energy is extracted from exhaust air  12  in order to power a turbine. The installation  10  may comprise any of a number of types of locations. The present matter in  FIG. 1  shows a building roof  14  having an exhaust unit  20  comprising an exhaust port  22  surrounding an exhaust fan  16 . The exhaust port  22  may take many forms. In the present illustration, the exhaust port  22  comprises a cylinder surrounding the exhaust fan  16 . Embodiments described below specifically illustrate exhaust fans comprising axial and radial fans. The current subject matter is not limited to any one particular form of fan. The preferred construction is in accordance with principles described below. 
     A generator system  30  comprises a casing  32  surrounding a turbine  34  in a radial dimension. The radial dimension may also be described as a horizontal plane  38 . Terms such as horizontal and vertical are used to describe relative positions. They do not necessarily describe orientation with respect to the radius of the Earth. The turbine  34  drives a generator  36 . The generator system  30  is suspended free of engagement with the exhaust unit  20  by a support  40 . Commonly, a support  40  will support the generator system  30  a predetermined distance above the roof  14 . The distance is determined in accordance with the teachings below. 
     A first embodiment working in conjunction with an axial exhaust fan is described with respect to  FIGS. 2 ,  3 , and  4 . These figures are respectively an isometric view, a cross-sectional view of an installation  10 , and a partial detailed isometric view illustrating support of the casing  32  and turbine  34  to the support  40 . 
     The exhaust unit  20  comprises a base  50  secured to the roof  14 . A foot  52  surrounds an air outlet  54  ( FIG. 3 ) supplying air to an annular path  56 . A first, outer wall of the air path  56  is defined by a radially outer wall  57  of an exhaust port  58  having a lower wall  59  substantially horizontally disposed. A radially inner wall of the air path  56  is defined by an exhaust fan motor housing  60  comprising a radially inner wall  62  extending in an axial, or vertical, dimension. A horizontal wall  64  of the exhaust fan motor housing  60  is axially opposite the lower wall  59 . A centrifugal fan  70  comprises a fan motor  72 , driveshaft  74 , and an impeller  76 . The impeller  76  rotates to draw in air from the air outlet  54  and propel it through the air path  56 . 
     Within the generator system  30 , the casing  32  is supported free of engagement with the exhaust unit  20 . In this manner, the generator system  30  can intercept the airflow  12  and at the same time avoid creating back pressure into the air path  56  ( FIG. 3 ). 
     The turbine  34  comprises an annular hub  104 . The annular hub  104  has a radially inner surface  106  and a radially outer surface  108 . In one form, the radially outer surface  108  is canted with respect to the radially inner surface  106 , and the two surfaces are joined at the lower end by a rounded portion  110  in order to form an airfoil. The turbine  34  is supported by radial support  112 . Blades  120  extend radially from the hub  104 . 
     The casing  32  has a radially inner surface  130  and a radially outer surface  132 . In one form, the radially outer surface  132  is canted with respect to the radially inner surface  130 , and the two surfaces are joined at the lower end by a rounded portion  136  in order to form an airfoil. Blades  120  extend radially from the hub  104 . The annular hub  104  and the casing  32  define an air path  136 . The casing  32  is supported to the support  40  by pieces  140  as further described below. 
     The axial, i.e., vertical cross section of the casing  32  is described by a geometrical function. In one form, the casing  32  comprises a truncated cone. Curves which are arcuate or which are defined by other functions could be embodied in the vertical cross section of the casing  32 . 
     The turbine  34  is supported in a horizontal plane by radial support  112 . Radial support  112  is coupled for rotation to a driveshaft  150  of the generator  36  and is supported by the driveshaft  150 . Power conditioning may be provided at the generator  36 . Usually, however, a conductor  154  is connected to the generator  36  and conducts power for conditioning elsewhere. In one form, an alternator  156  may be supported to the roof  14 . Alternatives include processing power elsewhere or connecting the outputs of a plurality of generators  36  to a single power conditioning unit, e.g., power conditioning unit  400  ( FIG. 8 ). 
     The support  40  ( FIG. 1 ) may take many different forms. In the embodiment illustrated, the support  40  comprises first, second, and third support members  162 ,  172 , and  182 . 
     The first support member  162  comprises a first vertical leg  164 , a radially inwardly extending leg  166 , and a vertical inner leg  168 . Similarly, the second support member  172  comprises a first vertical leg  174 , a radially inwardly extending leg  176 , and a vertical inner leg  178 . The third support member  182  comprises a first vertical leg  184 , a radially inwardly extending leg  186 , and a vertical inner leg  188 . Bolts  190  ( FIG. 3 ) may fasten the support  40  to the roof  10 . 
     The first, second, and third vertical inner legs  168 ,  178 , and  188  extend axially, i.e., downwardly, from the legs  166 ,  176 , and  186  respectively. They are dimensioned to place the generator system  30  at the preselected desired vertical position. The first, second, and third vertical inner legs  168 ,  178 , and  188  are secured to the generator  36  at attachment points  169 ,  179 , and  189  ( FIG. 4 ). The attachment points  169 ,  179 , and  189  may be equiangularly spaced. Attachment may be achieved by any of a number of means such as by welding, brazing, or by the use of fasteners. 
     As seen particularly in  FIG. 4 , each of the first, second, and third radially extending, i.e., horizontal, legs  166 ,  176 , and  186  respectively support mounting brackets  202 ,  204 , and  206 , each mounting bracket being in radial registration with an outer diameter of the casing  32 . Attachment may be achieved by any of a number of means such as by welding, brazing, or by the use of fasteners. 
     A second embodiment working in conjunction with a radial exhaust fan is described with respect to  FIGS. 5 ,  6 , and  7 . These figures are respectively an isometric view, a cross-sectional view of an installation  10 , and a partial detailed isometric view illustrating support of the casing  32  and turbine  34  to the support  40 . 
     In the present example, a centrifugal exhaust fan  300  is mounted on the roof  14 . The generating unit  30  may be constructed to work with centrifugal exhaust fans that are not necessarily mounted on top of the roof  14 . Dimensioning the support  40  and other components in accordance with the present teachings will accommodate other configurations of exhaust fans. 
     Exhaust air is delivered to the exhaust unit  20 . A duct  302  provides exhaust air to an intake eye  304  ( FIG. 6 ) of an impeller  306  of a centrifugal fan  310 . Impeller vanes  314  drive air to a centrifugal fan exhaust duct  318  which is positioned to provide an airflow  320  aimed at generating unit  30 . In the present arrangement, the airflow  320  is directed vertically. The airflow  320  exits from the centrifugal fan  310  at an outlet  324 . In the present embodiment, the outlet  324  is rectangular in a horizontal plane. It is desirable to intercept as much of the airflow  320  as practicable. 
     Therefore, a turbine  340  is provided with blades  344  substantially subtending the entire radial extent of the casing  30 . The blades  344  extend from a central hub  350 . The central hub  350  may have a curved lower axial surface  352  in order to reduce wind resistance. The central hub  350  is supported to a driveshaft  150  and with the turbine  340  rotates the driveshaft  150 . 
     The support  40  comprises a horizontal bar  360  supported on opposite horizontal sides by first and second A-frame supports  362  and  364 . The support is dimensioned to hold the generator system  30  at a desired vertical height. The desired vertical height is defined by a distance from the centrifugal fan outlet  324 . This distance is an optimization of maximum air velocity capture by the generator system  30  versus back pressure created on the airflow  320 . 
     The casing  32  is supported to horizontal bar  360  by first and second brackets  370  and  372 , as seen particularly in  FIG. 7 . Attachment may be achieved by any of a number of means such as by welding, brazing, or by the use of fasteners. 
       FIG. 8  is a plan view of embodiment in which a plurality of generator systems are connected to a single power conditioning circuit. In this illustration, first, second, and third generator systems  30 - 1 ,  30 - 2 , and  30 - 3  are provided. They deliver outputs respectively to conductors  156 - 1 ,  156 - 2 , and  156 - 3 , each of which is connected to a power conditioning circuit  400 . The power conditioning circuit  400  may include various forms of circuitry. The outputs from the generator units may be combined. Alternatively the outputs may be selectively switched. 
     Alternating current generators could be used. However, in applications contemplated for the present subject matter, DC generators will be more cost-effective and more efficient. 
     While the foregoing written description of the subject matter enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The subject matter should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the subject matter as claimed.