Abstract:
The invention relates to a system for absorbing electric energy from regenerative braking. The system comprises a battery, a thermoelectric module in thermally-conductive contact with the battery, a generator for generating an electric current from regenerative braking, the generator connected to the battery via a first switch and connected to the thermoelectric module via a second switch, and a sensor for measuring a temperature and a charge state of the battery. The system also comprises a controller for activating and deactivating the first switch and the second switch when certain conditions have been met.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The invention relates to systems and methods for absorbing electric energy or waste electricity from regenerative braking in hybridized vehicles. More particularly, the invention relates to systems and methods for using thermoelectric devices to absorb electric energy or waste electricity from regenerative braking in hybridized vehicles. 
         [0003]    2. Background 
         [0004]    The term “hybrid vehicle” is commonly referred to as a vehicle that utilizes more than one power source for propulsion. For example, a hybrid vehicle can be a vehicle that uses an internal combustion engine as a primary power source and an electric motor as a secondary power source. The electric motor can operate independently of or in conjunction with the internal combustion engine to drive the wheels of the vehicle. The electric motor enhances the fuel efficiency of the internal combustion engine. 
         [0005]    The electric motor can be powered by a number of batteries that need to be recharged on a regular basis. The batteries can be used to drive the electric motor and other components of the vehicle. The batteries are generally high-voltage (200-400 volts) batteries. A generator may be used to charge the batteries. 
         [0006]    Upon deceleration or downhill driving of a hybrid vehicle, the generator creates energy by regenerative braking and transfers the energy to the batteries for charging. Regenerative braking has the effect of slowing the vehicle down when traveling on a flat surface and reducing acceleration of the vehicle when traveling downhill. The batteries are continuously charged by regenerative braking. 
         [0007]    Continuously charging the batteries by regenerative braking has several drawbacks. First, the batteries can reach or exceed a predetermined maximum state-of-charge. Second, the batteries can reach or exceed a predetermined maximum temperature. In both cases, the batteries cannot accept any additional charge or risk being damaged from overcharging or overheating. Therefore, the amount of electric energy that can be absorbed by the batteries from regenerative braking may be limited due to the afore-mentioned drawbacks. If the batteries cannot absorb the energy from regenerative braking, the generator may be disengaged and the slowing or retarding force to the vehicle is reduced or eliminated. 
         [0008]    Therefore, a need exists in the art for providing systems and methods to absorb electric energy or waste electricity from regenerative braking in hybridized vehicles. 
       SUMMARY 
       [0009]    In one embodiment, the invention is a system for absorbing electric energy from regenerative braking. The system comprises a battery, a thermoelectric module in thermally-conductive contact with the battery, a generator for generating an electric current from regenerative braking, the generator connected to the battery via a first switch and connected to the thermoelectric module via a second switch, and one or more sensors for measuring a temperature and a charge state or state-of-charge of the battery. The system also comprises a controller for deactivating the first switch and activating the second switch when the charge state is equal to or greater than a maximum charge state of the battery, wherein the electric current is transferred to the thermoelectric module and has a polarity that causes the thermoelectric module to alternately cool and heat the battery in order to absorb the excess energy and change battery temperature if needed. The alternating may be performed every 5 seconds, for example. 
         [0010]    The system also comprises a controller for (1) deactivating the first switch and activating the second switch when the battery temperature is equal to or greater than a maximum temperature of the battery, wherein the electric current is transferred to the thermoelectric module and has a polarity that causes the thermoelectric module to cool the battery, (2) deactivating the first switch and activating the second switch when the battery temperature is below a minimum battery temperature, wherein the electric current is transferred to the thermoelectric module and has a polarity that causes the thermoelectric module to heat the battery, and (3) deactivating the first switch and activating the second switch when the charge state is equal to or greater than a maximum charge state of the battery, wherein the electric current is transferred to the thermoelectric module and has a polarity that causes the thermoelectric module to alternately heat and cool the battery to absorb the excess electric current without changing the charge or net state of the battery. 
         [0011]    In another embodiment, the invention is a method of absorbing electricity from regenerative braking. The method includes measuring an actual temperature of a battery using a first sensor, measuring a charge state of the battery using a second sensor, and obtaining a maximum operating battery temperature and a maximum charge state from memory. The method also includes transferring electric current from regenerative braking to a thermoelectric module using a controller wherein the controller sets a polarity of the electric current to cool the battery when the actual temperature is greater than or equal to the maximum operating battery temperature, and transferring electric current from regenerative braking to the thermoelectric module using the controller wherein the controller alternates a polarity of the electric current to heat and cool the battery when the charge state is greater than or equal to the maximum charge state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The features, objects, and advantages of the invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein: 
           [0013]      FIG. 1  is a block diagram of a system that uses thermoelectric modules to absorb waste electricity from regenerative braking according to an embodiment of the invention; and 
           [0014]      FIG. 2  is a flow chart of a method of absorbing waste electricity from regenerative braking according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Apparatus, systems and methods that implement the embodiments of the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate some embodiments of the invention and not to limit the scope of the invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements. 
         [0016]      FIG. 1  is a block diagram of a system that uses thermoelectric modules to absorb waste electricity from regenerative braking according to an embodiment of the invention. The system  100  may include an engine  105 , an electric motor/generator  110 , a controller  115 , a sensor  120 , a battery  125 , and a thermoelectric module  130 . The system  100  may be used with a vehicle that has a transmission  135 , a braking system  140 , and wheels  145 . The vehicle may be an automobile powered by any means (e.g., fuel cells, gasoline, hydrogen, solar, etc.) provided the vehicle is fully or partially powered by one or more batteries. For example, the vehicle may be a hybrid vehicle having a propulsion system which uses a combustion engine as one source of power, either to drive the vehicle wheels through a direct mechanical link or to generate electrical power, and also uses an electric motor to provide some or all propulsion power for the vehicle wheels. 
         [0017]    The engine  105  can be an internal combustion engine, a fuel cell, or any other type of engine that may be hybridized to provide partial or full power to the vehicle. The engine  105  is connected to the transmission or torque converter  135 , which is connected to an axle  150  that rotates to move the wheels  145 . 
         [0018]    The electric motor/generator  110  can be combined as one component or can be separate components. The electric motor/generator  110  uses electric fields and coiled wires to provide or generate electrical current to power the vehicle. 
         [0019]    The sensor  120  measures the actual temperature of the battery  125  and determines the charge state (e.g., fully or partially charged) of the battery  125 . The sensor  120  is in thermally-conductive contact with the battery  125 . 
         [0020]    The battery  125  can be a lead-acid battery, a nickel cadmium battery, a nickel metal hydride battery, a lithium-ion battery, or any other type of battery. The battery  125  may be a 12 volt battery for powering the components of the vehicle or a high-voltage battery for powering the electric motor/generator  110 . Other voltages may also be used. The battery  125  may comprise one or more batteries of the same or different voltages. 
         [0021]    The thermoelectric module  130  may have a first side and a second side. The flow of electrical current in one direction through the thermoelectric module  130  causes the first side to be heated and the second side to be cooled. Conversely, the flow of electrical current in the opposite direction through the thermoelectric module  130  causes the first side to be cooled and the second side to be heated. The first or the second side of the thermoelectric module  130  is in thermally-conductive contact with the battery  125 . In one embodiment, the thermoelectric module  130  is a Peltier circuit. 
         [0022]    The controller  115  can be any type of controller or switch which can direct the electrical current produced by the electric motor/generator  110  to the battery  125  and/or the thermoelectric module  130  based on the battery temperature and/or the battery charge received from the sensor  120 . That is, if the actual battery temperature exceeds a desirable operating temperature of the battery  125 , then the controller  115  may cause the electric current generated from regenerative braking to be directed to the thermoelectric module  130  in a direction of current flow that cools the battery  125 . If the actual battery temperature is less than a desirable operating temperature of the battery  125 , then the controller  115  may cause the electric current generated from regenerative braking to be directed to the thermoelectric module  130  in a direction of current flow that heats the battery  125 . Similarly, if the charge state is fully charged, then the controller  115  may cause the electric current generated from regenerative braking to be directed to the thermoelectric module  130  in an alternating direction of current flow that serves to cool and heat the battery  125  in periodic or random fashion. The controller  115  may be coupled to a memory  117 , which can be used to store a maximum operating battery temperature and a minimum operating battery temperature, and a fully-charged state of the battery  125 . 
         [0023]    The controller  115  can cause the electric motor/generator  110  to simultaneously direct electric waste energy to both the battery  125  and the thermoelectric module  130  to preserve the “engine braking” feel. In one embodiment, the thermoelectric module  130  can consume additional energy from regenerative braking to preserve the “engine braking” feel by alternately heating and cooling the battery  125  in rapid succession (e.g., every 5 seconds). The alternately heating and cooling of the battery  125  may also be periodic or random. 
         [0024]      FIG. 2  is a flow chart of a method of absorbing waste electricity from regenerative braking according to an embodiment of the invention. The sensor  120  measures an actual temperature and a charge state of the battery  125  (block  200 ). The controller  115  receives the actual temperature and the charge state of the battery  125 . The controller  115  also receives and/or stores a maximum battery temperature and a minimum battery temperature (block  205 ). If the actual temperature of the battery  125  is greater than the maximum battery temperature (i.e., battery  125  is too hot) or less than the minimum battery temperature (i.e., battery  125  is too cold) (blocks  210  and  220 ), then the controller  115  causes the electric motor/generator  110  to transfer electric current (i.e., waste electricity from regenerative braking) to the thermoelectric module  130  in a direction or with a polarity that cools or heats the battery  125  (blocks  215  and  225 ). If the charge state of the battery  125  is fully charged (i.e., battery  125  does not need any more charging) (block  230 ), then the controller  115  causes the electric motor/generator  110  to transfer electric current (i.e., waste electricity from regenerative braking) to the thermoelectric module  130  in a direction or with a polarity that cools or heats the battery  125  depending on the actual temperature of the battery  125  (block  235 ). In one embodiment, if the charge state of the battery  125  is fully charged, then the controller  115  causes the electric motor/generator  110  to transfer electric current to the thermoelectric module  130  in a direction or with a polarity that alternately (e.g., every 5 seconds) cools and heats the battery  125 . If the charge state of the battery  125  is not fully charged (i.e., battery  125  needs more charging), then the controller  115  causes the electric motor/generator  110  to transfer electric current to the battery  125  and/or the thermoelectric module  130  in a direction or with a polarity that charges the battery  125  and/or cools or heats the battery  125  depending on the actual temperature of the battery  125  (block  240 ). 
         [0025]    Directing the electricity from regenerative braking to the thermoelectric module  130  (rather than continuously charging the battery  125 ) allows the vehicle to preserve its original retarding force instead of reducing its rolling resistance and forcing the driver to increasingly rely on the braking system  140  for slowing the vehicle. The system  100  maintains or acquires optimum temperature of the battery  125 . In addition, the thermoelectric module  130  provides a sink for or absorbs waste electricity or excess power during periods of time when (1) regenerative braking energy continues to be created after the battery  125  has reached its maximum charge state, (2) the battery  125  is overheating due to, for example, extended downhill driving, and (3) the battery  125  is too cold because the battery  125  has been exposed to cold temperatures. 
         [0026]    Those of ordinary skill would appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the examples disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosed apparatus and methods. 
         [0027]    The various illustrative logical blocks, modules, and circuits described in connection with the examples disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
         [0028]    The steps of a method or algorithm described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an Application Specific Integrated Circuit (ASIC). The ASIC may reside in a wireless modem. In the alternative, the processor and the storage medium may reside as discrete components in the wireless modem. 
         [0029]    The previous description of the disclosed examples is provided to enable any person of ordinary skill in the art to make or use the disclosed methods and apparatus. Various modifications to these examples will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other examples without departing from the spirit or scope of the disclosed method and apparatus. The described embodiments are to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.