Abstract:
A system ( 10 ) for converting energy having an array of thermoelectric devices ( 60 ) connected electrically in series between a first heat exchanger ( 15 ) in contact with a first surface ( 61 ) of the array and a second heat exchanger ( 20 ) in contact with a second surface ( 63 ) opposite the first surface of said array ( 60 ). The array ( 60 ) is capable of generating a DC current while a thermal gradient between the first surface and the second surface is applied. When DC current is applied to said array, either waste heating or waste cooling is produced at a working surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to an energy converter that is capable of directly converting between the thermal and electrical energy as part of an integrated cooling, heating, and power (CHP) system where waste heat and electrical power are abundant and accessible. 
         [0003]    2. Description of Related Art 
         [0004]    An integrated CHP system faces challenges to meet simultaneously cooling, heating, and electric loads in a variety of applications and environments. The characteristics of the different loads require that integrated CHP systems have flexible operating modes-and offer flexible cooling, heating and power capacity. While conventional CHP solutions can be used to meet primary loads, supplemental cooling, heating, and power generation systems must be used to meet fluctuated loads at various times of a day or seasons. Conventionally, grid power is used, in addition to a CHP system to meet the need of additional electric load. A vapor compression system is used to meet the need of additional cooling load. A heating system is used to meet the need of additional heating load. The conventional solutions are bulky, noisy, require complex control systems and often take a longer time to achieve a satisfactory cooled or heated condition. Thus they are inconvenient and inefficient. Further, current conventional systems are still dependent on grid power and have lower system reliability because they have many moving parts. 
         [0005]    Therefore, there exists a need for an energy converter that can directly convert between thermal energy (heat rejected or absorbed) and electrical energy (electricity), as a buffering system, to meet the need of various loads that supplemental systems of a conventional CHP system are able to independently meet. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a multi-functional energy converter that is capable of directly converting between electrical and thermal energy using a single system. 
         [0007]    It is also an object of the present invention to provide a multi-functional energy converter that uses an array of thermoelectric elements to convert directly between electrical energy and thermal energy (cooling and heating) using a single system. 
         [0008]    It is a further object of the present invention to provide a multi-functional energy converter that applies a thermal gradient to an array of thermoelectric elements to generate a voltage across the thermoelectric elements. 
         [0009]    It is yet a further object of the present invention to provide a multi-functional energy converter that creates cooling at one surface of the thermoelectric elements and creates heating at another surface of the thermoelectric elements opposite the cool surface when a DC voltage is applied across the array of elements. 
         [0010]    These and other objects of the present invention are provided by an array of thermoelectric elements connected electrically in series between a first heat exchanger in contact with a first surface of the array, the first surface being a working surface, and a second heat exchanger in contact with a second surface opposite the first surface of the array. The array of thermoelectric elements is capable of generating a DC current while applying a temperature gradient between the first surface and the second surface. The array of thermoelectric elements is also capable of providing thermal energy to a fluid or withdrawing thermal energy from a fluid at said working surface from waste heating or cooling at the working surface. 
         [0011]    A system for converting energy having an array of thermoelectric elements connected electrically in series is provided. The system also provides for a first substrate covering one surface of the array and second substrate covering a second surface of the array that is opposite the first surface of the array, the first surface being a working surface. The array of thermoelectric elements is capable of generating a DC current while a temperature gradient between the first substrate and the second substrate is applied or providing thermal energy to said working surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]      FIG. 1  illustrates a first embodiment of the present invention configured for a power generation mode; 
           [0013]      FIG. 2  illustrates a second embodiment of the present invention configured for a cooling mode; and 
           [0014]      FIG. 3  illustrates a third embodiment of the present invention configured for a heating mode. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Referring to  FIG. 1 , the first embodiment of system  10  of the present invention is shown in the power generation mode. In this embodiment, system  10  has a heat exchanger  15  and a heat exchanger  20 . Heat exchanger  15  has a high temperature from waste heat, which flows in the direction of arrow, relative to heat exchanger  20 . Heat exchanger  20  is cooled by water. System  10  has closed valves  45  and  50  to permit heat exchangers  15  and  20  together to create a thermal gradient across thermoelectric devices  60 . Thermoelectric devices  60  have opposing surfaces  61  and  63 . This temperature gradient causes an electric current  70  to flow between terminals  75  and  80 , a phenomenon known as the Seebeck effect. 
         [0016]    Thermoelectric devices  60  located between heat exchangers  15  and  20  are arranged in an array of P and N junctions  65  that are configured in series by electrical contacts  62 . When a thermal gradient is applied, a DC voltage develops across terminals  75  and  80  and current  70  flows across junctions  65 . The DC voltage is converted to an AC voltage in the DC to AC inverter  85 . Substrates  66  hold system  10  together and mechanically and electrically insulate thermoelectric junctions  65 . Surface  61  of thermoelectric devices  60  becomes cool and surface  63  becomes hot. In this example, hot water  90  and cold water  95  flows through heat exchangers  15  and  20 , respectively. Other modes of operation generating either a hot or cold flow of fluid could have been used as well. 
         [0017]    Power created using thermoelectric junctions  65  of the embodiment on  FIG. 1 , can be used to supplement power to a CHP system that is short of electricity and abundant of waste heat in varied geographic locations and ambient environments. The systems need not be geographically isolated. Such systems could be onsite residential communities, office parks, campuses or stand alone buildings. The thermal gradient created by waste heat from a prime mover, for example, can be used to generate the thermal gradient necessary to generate the power to meet the peak electrical load. Alternatively, the power generated could be used during peak power demand times to power other components of a CHP system. 
         [0018]    Referring to  FIG. 2 , a similar configuration of elements as those described in the first embodiment can be re-configured to provide a cooling system  100 . In the second embodiment of the present invention, a DC voltage from a power source  105  is applied across system  100  and a current  110  flows in the direction shown. The P and N junctions  112  in the thermoelectric device  115  absorb heat from a surface  120 , a working surface, and reject the heat to a surface  125  at the opposite side. Surface  120  where the heat is absorbed becomes cold and the opposite surface  125  where the heat is rejected becomes hot. This “heat pumping” phenomenon, known as the Peltier effect, is commonly used in thermoelectric refrigeration. In this embodiment water  130  that flows through a heat exchanger  140  provides heat to surface  120  to be cooled. Water  135  that flows through a heat exchanger  145  will transport heat away from surface  125  and be heated. System  100 , like system  10 , has electrical connectors  142  to connect pairs  112  in series. Substrates  144  hold system  100  together mechanically and electrically insulate pairs  112 . Power source  105  used in this configuration can be a battery, a fuel cell, any other similar devices used to supply current, or simply from the excessive power generated by the CHP system. 
         [0019]    The benefit of using the configuration of  FIG. 2  is that during the period of which additional cooling is required, for example in the summer, and excessive electric power is generated by the CHP system, the system is able to provide additional cooling in addition to the conventional CHP system. Further, because the cooling system uses thermoelectric modules and does not use compressors or other traditional air conditioning components, minimal maintenance is required. Furthermore, the versatility of the system of  FIG. 2 , is such that by reversing the polarity of DC power supply  105  causes heat to be pumped in the opposite direction to convert cooling system  100  to a heating system. 
         [0020]    Referring to  FIG. 3 , in the third embodiment of the present invention, the thermoelectric system is configured as a heating system  160 . In this embodiment, the same components as the embodiment of  FIG. 2 , are used except that the polarity of a power supply  165  is reversed and a current  170  flows in the opposite direction. In  FIG. 3 , current  170  flows through P and N pairs  215  of the thermoelectric devices  220  and a temperature gradient is generated at the surfaces  180  and  185 . At surface  185  heat is absorbed and the surface becomes cool. Water  195  flowing through heat exchanger  205  is cooled. At surface  180 , a working surface, heat is released in the direction of arrow and water flowing through heat exchanger  200  becomes hot. 
         [0021]    The embodiment of the system  160   FIG. 3 , can be used to provide additional heating in a CHP system during the cooler months of the year. The system of  FIG. 3  also offers the same benefits of the configuration of  FIG. 2 . The primary benefit of the system is that a single system can independently meet the cooling, heating and power requirements of a system combined with a conventional CHP system throughout the year by generating DC current from waste heat, generating cooling or heating effect at a working surface. 
         [0022]    While the instant disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.