Patent Publication Number: US-2009235968-A1

Title: Apparatus for generating electric power using thermal energy

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Application No. 97109852, filed on May 20, 2008. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an apparatus for generating electric power, more particularly to an apparatus for generating electric power using thermal energy. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional thermoelectric semiconductor device  1  for electric generation is shown to include a first metal conductor  13 , two second metal conductors  14  spaced apart from each other, a P-type semiconductor element  11  interconnecting electrically the first metal conductor  13  and one of the second metal conductors  14 , and an N-type semiconductor element  12  interconnecting electrically the first metal conductor  13  and the other one of the second metal conductors  14  such that the P-type and N-type semiconductor elements  11 ,  12  are connected electrically to each other in series via the first metal conductor  13 , wherein the first metal conductor  13  serves as a low temperature side, and the second metal conductors  14  constitute a high temperature side. As a result of the Seebeck effect, the conventional thermoelectric semiconductor device  1  generates a DC current (I) corresponding to a difference between temperature of the first metal conductor  13  and temperature of the second metal conductors  14 . 
     The following are some of the drawbacks of the conventional thermoelectric semiconductor device  1 : 
     1. The P-type and N-type semiconductor elements  11 ,  12  are formed by high-pressure pressing fine metal powers, and are soldered respectively to the first and second metal conductors  13 ,  14  with tin solder having a melting point of 200° C. Thus, the P-type and N-type semiconductor elements  11 ,  12  are easily broken under a high temperature environment, thereby occurring peeling of the tin solder. 
     2. Since heat from the second metal conductors  14  is easily transferred to the first metal conductor  13  via air, thereby resulting in a reduced temperature difference between the first metal conductor  13  and the second metal conductors  14 . 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide an apparatus for generating electric power using thermal energy that can improve the electric-generating efficiency. 
     According to the present invention, there is provided an apparatus for generating electric power using thermal energy. The apparatus comprises: 
     a thermoelectric semiconductor unit including at least one thermoelectric semiconductor device that includes
         a first ceramic layer having an outer surface that serves as a low temperature surface adapted to contact a cold source, and an inner surface opposite to the outer surface of the first ceramic layer,   a second ceramic layer opposite to the first ceramic layer and having an outer surface that serves as a high temperature surface adapted to contact a heat source, and an inner surface opposite to the outer surface of the second ceramic layer,   a row of first conductive members attached spacedly to the inner surface of the first ceramic layer,   a row of second conductive members attached spacedly to the inner surface of the second ceramic layer,   a plurality of alternately arranged P-type and N-type semiconductor elements disposed between the first and second ceramic layers, each of the P-type and N-type semiconductor elements interconnecting electrically a corresponding one of the first conductive members and a corresponding one of the second conductive members to form a snakelike structure so that the P-type and N-type semiconductor elements are connected electrically and alternately to each other in series via the first and second conductive members, and   a heat insulation material filled between the inner surface of the first ceramic layer and the inner surface of the second ceramic layer,   wherein the thermoelectric semiconductor device of the thermoelectric semiconductor unit outputs a DC power in the form of a current corresponding to a difference between temperature of the low temperature surface of the first ceramic layer and temperature of the high temperature surface of the second ceramic layer; and       

     a circuit unit coupled to the thermoelectric semiconductor unit for receiving the DC power therefrom, and operable so as to output a voltage output corresponding to the DC power. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic view illustrating a conventional thermoelectric semiconductor device; 
         FIG. 2  is a schematic circuit block diagram illustrating the preferred embodiment of an apparatus for generating electric power using thermal energy according to the present invention; 
         FIG. 3  is a schematic view illustrating a thermoelectric semiconductor device of a thermoelectric semiconductor unit of the preferred embodiment; 
         FIG. 4  is a perspective fragmentary view showing the preferred embodiment; and 
         FIG. 5  is a fragmentary schematic sectional view showing the preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 2 to 5 , the preferred embodiment of an apparatus for generating electric power using thermal energy according to the present invention is shown to include a thermoelectric semiconductor unit  2 , a circuit unit  3 , and a heat-conducting unit  4 . 
     The thermoelectric semiconductor unit  2  includes a plurality of thermoelectric semiconductor devices  20  coupled to each other in series. As shown in  FIG. 3 , each thermoelectric semiconductor device  20  includes a first ceramic layer  21 , a second ceramic layer  22 , a row of first conductive members  23 , a row second conductive members  24 , a plurality of alternately arranged P-type and N-type semiconductor elements  25 ,  26 , and a heat insulation material  27 . For each thermoelectric semiconductor device  20 , the first ceramic layer  21  has an outer surface that serves as a low temperature surface  211  adapted to contact a cold source, such as stream water, seawater, groundwater, etc., and an inner surface  212  opposite to the low temperature surface  211 . The second ceramic layer  22  is opposite to the first ceramic layer  21 , and has an outer surface that serves as a high temperature surface  221  adapted to contact a heat source, such as terrestrial heat, hot spring, high-temperature industry exhaust fume, etc., and an inner surface  222  opposite to the high temperature surface  221 . The first conductive members  23  are attached spacedly to the inner surface  212  of the first ceramic layer  21 . The second conductive members  24  are attached spacedly to the inner surface  222  of the second ceramic layer  22 . In this embodiment, each of the first and second conductive members  23 ,  24  is in the form of a copper foil conductor. The P-type and N-type semiconductor elements  25 ,  26  are disposed between the first and second ceramic layers  21 ,  22 . Each of the P-type and N-type semiconductor elements  25 ,  26  interconnects electrically a corresponding one of the first conductive members  23  and a corresponding one of the second conductive members  24  to form a snakelike structure so that the P-type and N-type semiconductor elements  25 ,  26  are connected electrically and alternately to each other in series via the first and second conductive members  23 ,  24 . In this embodiment, each of the P-type and N-type semiconductor elements  25 ,  26  is formed by sintering fine powers of antimony and bismuth, and has opposite end surfaces soldered respectively to the corresponding one of the first conductive members  23  and the corresponding one of the second conductive members  24  with copper solder that has a melting point higher than 500° C. The heat insulation material  27  is filled between the inner surface  212  of the first ceramic layer  21  and the inner surface  222  of the second ceramic layer  22 . In this embodiment, the heat insulation material  27  includes an ammonium phosphate compound. Each thermoelectric semiconductor device  20  outputs a DC power in the form of a current corresponding to a difference between temperature of the low temperature surface  211  of the first ceramic layer  21  and temperature of the high temperature surface  221  of the second ceramic layer  22 . As a result, the thermoelectric semiconductor unit  2  outputs a sum of the DC powers from the thermoelectric semiconductor devices  20  as a DC input. 
     The circuit unit  3  is coupled to the thermoelectric semiconductor unit  2  for receiving the DC input therefrom, and is operable so as to output a voltage output corresponding to the DC input. In this embodiment, as shown in  FIG. 2 , the circuit unit  3  includes a voltage regulator  31 , a rechargeable battery unit  32 , and a DC-to-AC converter  33 . The voltage regulator  31  is coupled to the thermoelectric semiconductor unit  2  for receiving and regulating the DC input therefrom. The rechargeable battery unit  32  is coupled to the voltage regulator  31 , and is charged by the DC input regulated by the voltage regulator  31  so as to supply a DC voltage. The DC-to-AC converter  33  is coupled to the rechargeable battery unit  32  for converting the DC voltage supplied thereby into an AC voltage, and outputs the AC voltage that serves as the voltage output. 
     As shown in  FIGS. 4 and 5 , the heat-conducting unit  4  is in thermal contact with the high temperature surfaces  221  of the second ceramic layers  22  of the thermoelectric semiconductor devices  20  of the thermoelectric semiconductor unit  2  and is adapted to contact the heat source for transferring heat from the heat source to the high temperature surfaces  221  of the second ceramic layers  22  of the thermoelectric semiconductor devices  20  of the thermoelectric semiconductor unit  2 . In this embodiment, the heat conducting unit  4  includes a rectangular hollow heat-conductive body  40 , a series of tubular heat-conducting members  41 , and a heat insulation frame  46 . 
     The heat-conductive body  40  is configured with a vacuum chamber  401  therein, and has an outer surface  400  that has front and rear surface portions  404 ,  405 , opposite lateral surface portions  407 , and top and bottom surface portions  406 ,  408 , wherein the high temperature surfaces  221  of the second ceramic layers  22  of the thermoelectric semiconductor devices  20  of the thermoelectric semiconductor unit  2  are attached to the front and rear surface portions  404 ,  405 . A heat-conductive material  47  is filled in the vacuum chamber  401 . In this embodiment, the heat-conductive material  47  is in the form of a volatile solution containing inorganic media, such as manganese (Mn), sodium (Na), beryllium (Be), dichromate, etc., zinc (Zn) magnesium (Mg) and calcium (Ca). 
     The heat insulation frame  46  covers the top, bottom and lateral surface portions  406 ,  407 ,  408  of the outer surface  400  of the heat-conductive body  40 . 
     The tubular heat-conducting members  41  are in thermal contact with each other. One of the tubular heat-conducting members  41 , for example, a top one of the tubular heat-conducting members  41  of  FIG. 5 , is in thermal contact with the heat-conductive body  40 . Each tubular heat-conducting member  41  is made of copper, iron, high-carbon steel, etc., has a length ranged from 1 m to 10 m, and includes a metal tube body  411 , a female cover body  412 , a male cover body  413 , and the heat-conductive material  47 . 
     For each tubular heat-conducting member  41 , the metal tube body  411  has top and bottom ends  4111 ,  4112 . The female cover body  412  is connected threadedly and soldered to the top end  4111  of the metal tube body  411  for covering sealingly the top end  4111  of the metal tube body  411 , and is formed with an engaging groove  4121 . The male cover body  413  is connected threadedly and soldered to the bottom end  4112  of the metal tube body  411  for covering sealingly the bottom end  4112  of the metal tube body  411 , has a plug portion  4131  that engages detachably the engaging groove  4121  in the female cover body  412  of an adjacent one of the tubular heat-conducting members  41 , and cooperates with the female cover body  412  and the metal tube body  411  to define an inner accommodating space  410  thereamong. The heat-conductive material  47  is filled in the inner accommodating space  410 . 
     In this embodiment, the heat-conductive body  40  further has a plug portion  403  extending from the bottom surface portion  408  of the outer surface  400  and engaging detachably the engaging groove  4121  in the female cover body  412  of the top one of the tubular heat-conducting members  41 . In this embodiment, each of the plug portion  4131  of the male cover body  413  of each tubular heat-conducting member  41  and the plug portion  403  of the heat-conductive body  49  is in the form of a screw bolt. The engaging groove  4121  in the female cover body  412  of each tubular heat-conducting member  41  is in the form of a blind threaded hole. 
     Furthermore, a U-shaped heat-conductive water tank  5  has an inlet  51  and an outlet  52 , and is disposed around the heat-conductive body  40  so that the water tank  5  is in thermal contact with the low temperature  211  of the thermoelectric semiconductor devices  20  of the thermoelectric semiconductor unit  2 . As a result, stream water, seawater or groundwater serving as the cold source can be drawn into the water tank  5  via the inlet  51  to fill the water tank  5 , and then flows out of the water tank  5  via the outlet  52  to form a flow cycle, thereby maintaining the low temperature surfaces  211  of the thermoelectric semiconductor devices  20  of the thermoelectric semiconductor unit  2  at a relatively low temperature. 
     In use, the number of the tubular heat-conducting members  41  depends on a distance between the heat source and the heat-conductive body  40 . 
     In sum, due to the presence of the heat insulation material  27 , heat transferred from the second ceramic layer  22  to the first ceramic layer  21  can be minimized, thereby improving the electric-generating efficiency. In addition, since the P-type and N-type semiconductor elements  25 ,  26  are formed by sintering, structure strength of the P-type and N-type semiconductor elements  25 ,  26  can be improved. Moreover, the copper foil conductor serving as the first and second conductive members  23 ,  24  and the copper solder have a melting point much higher than that of the tin solder. Therefore, peeling of the solder incurred in the aforesaid conventional thermoelectric semiconductor device can be avoided. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.