Patent Publication Number: US-2023138483-A1

Title: Thermoelectric Energy Harvesting Apparatus System and Method

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to apparatuses and systems of battery-free thermoelectric devices, and, in particular, energy harvesters for Internet of Things sensors. 
     2. Description of the Related Art 
     Electronic sensors have been in use for decades, relaying information to data collectors and hubs in commercial and residential applications. While early sensors obtained power to transmit their data by wired connections, later sensors were remote and had their own power storage and transmitted data wirelessly. Embedded sensors with wireless capability are fundamental to the Internet of Things (IoT) technology. 
     While millions of remote sensors reduced the cost and bulk of hardware required for installation, maintenance was increased by the need to change out the power storage devices (i.e. batteries) on a periodic basis. One solution to the battery changing dilemma was the use of photovoltaic cells to power the sensors via sunlight. 
     A shortcoming in prior art sensors is the need to have energy storage devices replaced on a regular basis. Another shortcoming in some prior art sensors is that they need exposure to a radiant light power source, such as the sun, and, thus, cannot be used in placed in areas where visible light is low or absent. 
     What are needed are thermoelectric energy harvesting devices that can power sensors and do not require changing of the energy storage devices. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     In aspects, the present disclosure is related to an apparatus and system for supplying energy to low power devices, and, in particular, thermoelectric energy harvesters that eliminate the need or greatly reduce the need for replacing energy storage batteries. 
     One embodiment according to the present disclosure includes a thermoelectric energy harvesting apparatus, the apparatus including a thermoelectric converter with a temperature differential between a first side and a second side of the thermoelectric converter; a heat sink in thermal communication with the first side and ambient air; a plurality of heat fins in thermal communication with the heat sink and the ambient air; a base plate in thermal communication with the second side; a power management component comprising an energy storage medium in electrical communication with the thermoelectric converter; and an air mover electrically coupled to the power management component to direct air flow at the plurality of heat fins. The apparatus may also include a voltage rectified electrically disposed between the thermoelectric converter and the power management component. The apparatus may also include a power feedback loop configured to adjust the power to the air mover based on an increase in power generated by the thermoelectric converter. The apparatus may also include a heat exchanger disposed between at least two adjacent heat fins of the plurality of heat fins, wherein the heat exchanger surface is substantially parallel to the direct air flow. The heat exchanger may be corrugated in shape. 
     Another embodiment according to the present disclosure includes a thermoelectric sensor system, the system that includes: a thermoelectric energy harvester including a thermoelectric converter with a temperature differential between a first side and a second side of the thermoelectric converter; a heat sink in thermal communication with the first side and ambient air; a plurality of heat fins in thermal communication with the heat sink and the ambient air; a base plate in thermal communication with the second side; a power management component comprising an energy storage medium in electrical communication with the thermoelectric converter; and an air mover electrically coupled to the power management component to direct air flow at the plurality of heat fins; a sensor electrically connected to the power management component; and a wireless transmitter electrically connected to the sensor. In some embodiments, the wireless transmitter may be configured to communicate with the Internet or another computer network. 
     Another embodiment according to the present disclosure is a method of harvesting electrical energy, the method including the steps of: generating electrical power using a thermoelectric energy harvester; storing the electrical power; moving ambient air or the thermoelectric energy harvester relative to the other using the stored electrical power. The method may also include a step to adjusting the stored electrical power used based on an increase in electrical power generated using the thermoelectric energy harvester. Examples of the more important features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood and in order that the contributions they represent to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
         FIG.  1    is a diagram of a thermoelectric wireless sensor system according to one embodiment of the present disclosure; 
         FIG.  2 A  is a graph of ambient air temperature fluctuations on the first side of the thermoelectric converter of the thermoelectric wireless sensor of  FIG.  1   ; 
         FIG.  2 B  is a graph of temperature differentials across the thermoelectric converter of the thermoelectric wireless sensor of  FIG.  1   ; 
         FIG.  2 C  is a graph of the voltages produced by the thermoelectric converter of the thermoelectric wireless sensor of  FIG.  1   ; 
         FIG.  2 D  is a graph of the power transferred by the thermoelectric converter to the energy storage of the thermoelectric wireless sensor of  FIG.  1   ; 
         FIG.  3    is another embodiment of a thermoelectric wireless sensor system according to one embodiment of the present disclosure; 
         FIG.  4    is a graph of the heat transfer of the thermoelectric converter of  FIG.  3    relative to air movement; 
         FIG.  5 A  is a diagram a rectifier for use in the thermoelectric wireless sensor system of  FIG.  3   ; 
         FIG.  5 B  is a diagram of another rectifier for use in the thermoelectric wireless sensor system of  FIG.  3   ; 
         FIG.  6 A  is a picture of a thermoelectric energy harvester with air mover and heat exchangers according to another embodiment of the present disclosure; 
         FIG.  6 B  is a cross-section view of the thermoelectric energy harvester of  FIG.  6 A ; 
         FIG.  6 C  is a cross-section view of the air mover in the thermoelectric energy harvester of FIG. 
         FIG.  7 A  is a diagram of another embodiment of a thermoelectric energy harvester using vibrators to move the heat exchanger relative to the air according to one embodiment of the present disclosure; 
         FIG.  7 B  is a picture of an alternative heat exchanger array a thermoelectric energy harvester according to another embodiment of the present disclosure; and 
         FIG.  8    is a flow chart of a method for generating electrical energy using a thermoelectric energy harvester according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Generally, the present disclosure relates to apparatuses and systems for transmitting data while powered through the conversion of heat energy to electrical energy, and, in particular, transmitting data using energy derived from temperature differentials and storing that energy in an energy storage medium that does not require regular access for changing out power cells. The present disclosure is susceptible to embodiments of different forms. They are shown in the drawings, and herein will be described in detail, specific embodiments of the present disclosure with the understanding that the present disclosure is to be considered an exemplification of the principles of the present disclosure and is not intended to limit the present disclosure to that illustrated and described herein. 
       FIG.  1    shows a diagram of a thermoelectric wireless sensor system  100 . The system  100  includes a thermoelectric energy harvester  110 , a power management component  120 , a microcontroller unit (MCU) and sensor  130 , and a wireless transmitter  140 . The thermoelectric energy harvester  110  includes a thermoelectric device with a first side and a second side (discussed later) and generates electrical power from a temperature differential in the ambient air and electrically communicates this power to the power management component  120 . The power management component  120  may include an energy storage device, such as an electrolytic capacitor, supercapacitor, a power management integrated circuit (PMIC), or a rechargeable battery, that is suitable to store energy from the thermoelectric energy harvester  110 . The power management component  120  may include a circuit for switching between charging and discharging modes. The power management component  120  may discharge energy to the microcontroller  130 , which may include one or more sensors that are configured to detect one or more parameters of interest and convert sensor inputs into data that can be transmitted. The parameters of interest can be any measurable characteristic or property, including, but not limited to, temperature, magnetic field strength, sound frequency, light intensity, chemical composition, humidity. A person of skill in the art would recognize that anything that can be sensed can have its sensor used with the system  100 . The microcontroller with sensor  130  communicates its data to the wireless transmitter  140 , which converts the electrical signal into an electromagnetic signal that can be detected by a suitable receiver at a location remote to the system  100 . The wireless transmitter  140  may communicate information from the microcontroller with sensor  130  to any wireless receiver, including the receivers connected to the Internet or local routers or networks. In some embodiments, one or more systems  100  may be part of an IoT system, whereby the separate systems  100  may communicate via the Internet, whether local or remote, with other devices or one another. 
       FIG.  2 A  shows a graph of ambient air temperature fluctuations on the first side of the thermoelectric energy harvester. In this exemplary and non-limiting instance, the temperature fluctuates between about 24 degrees Celsius and 31 degrees Celsius. In some embodiments, the ambient air temperature may be lower or much higher (over 1000 degrees Celsius). These temperature fluctuations tend to be quicker than the changes in the temperature of the second side of the thermoelectric energy harvester  110 . As a result of the difference in the speed of temperature fluctuations between the first side and the second side, a temperature differential between the two sides is created, as shown the graph in  FIG.  2 B . 
       FIG.  2 C  shows a graph of the voltage generated by the thermoelectric energy harvester  110  due to the temperature differential between the first side and the second side.  FIG.  2 D  shows a graph of the power transferred to the power management component  120  due to the voltage generated by the thermoelectric energy harvester  110 . 
       FIG.  3    shows another embodiment of a thermoelectric wireless sensor system  300 . The system  300  includes a thermoelectric energy harvester  300 , the power management component  120 , the microcontroller (with sensor)  130 , and the wireless transmitter  140 . The thermoelectric energy harvester  300  may include a thermoelectric converter  320  with a first side  323  and a second side  327 . In some embodiments, monolithically integrated thermoelectric converters implemented as arrays of thermoelectric couples to form the thermoelectric converter  320 . In some embodiments, thermoelectric converter  320  may be selected based on the desired operating temperature and/or temperature difference expected across the thermoelectric converter  320  as shown in Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Operating 
                   
               
               
                 temperature range 
                 Thermoelement materials 
               
               
                   
               
             
            
               
                 −50° C. to 
                 Bi—Sb—Te—Se chalcogenides, Mg—Bi—Si, 
               
               
                 150° C. 
                 In—Sb, Organic (PANi/graphene-PEDOT:PSS/PANi/ 
               
               
                   
                 DWNT-PEDOT), Heusler materials Fe—V—W—Al 
               
               
                  150-400° C. 
                 Pb—Te—Se, Sn—Se, Zn—Sb, Ba—Yb—CoSb3, 
               
               
                   
                 Ce—Fe—CoSb3 
               
               
                 400-1000° C. 
                 Si—Ge—C, Zintls such as Yb—Mn—Sb, rare-earth 
               
               
                   
                 tellurides La—Te and Pr—Te 
               
               
                   
               
            
           
         
       
     
     The second side  327  is in thermal communication with a base plate  330 . The base plate  330  may be made of or include a phase change material (PCM). In some embodiments, the base plate  330  may be made of a metal. A plurality of heat fins  340  may be in thermal communication with the first side  323  and the ambient air. One or more thin heat exchangers  350  may be disposed between adjacent heat fins  340 . The thin heat exchangers  350  may be made of a thin metallic foil or other heat conducting material. The thin heat exchanger  350  increases the surface area for dispersing heat into the ambient air beyond what could be done with only the heat fins  340 . In some embodiments, the thin heat exchangers  350  may be loosely folded multiple times between adjacent heat fins  340 , forming an even larger surface area contact with the ambient air. While the heat fins  340  are disposed perpendicularly or substantially perpendicular to the first side  327 , the thin heat exchangers  350  may be disposed parallel to or substantially parallel to the first side  327 . Thus, the heat exchangers  350 , while loosely folded or corrugated, may be in physical communication with and generally perpendicular to the heat fins  340 . The system  300  includes an air mover  360  configured to cause air movement in the form of pulses or wavelets  365  or otherwise disturbs laminar air flow. The air mover  360  is disposed such that the wavelets  365  travel across the surfaces of the thin heat exchangers  350  and the heat fins  340  to maximize the removal of heat to the ambient air. The thermoelectric converter  320  produces an electric voltage when there is a temperature differential across the thermoelectric converter  320 . The temperature differential may be positive or negative depending on whether the first side is hotter or colder than the second side, resulting in a positive or negative voltage produced by the thermoelectric converter  320 . This voltage may be rectified by a voltage rectifier  370  such that the electrical energy flows into the power management component  120  for storage. Power from the power management component  120  may pass through a feedback controller circuit  380  and be used to power the air mover  360 . The feedback controller circuit  380  may be configured to drive the air mover  360  up to a power level where there is still a net gain in power being received by the power management component  120 . 
       FIG.  4    shows a graph of the heat transfer of the thermoelectric converter  320  and how it changes as the air wavelets  365  remove heat from the heat fins  340  and thin heat exchangers  350 . The curve  400  shows the increase in the heat transfer coefficient as the air speed across the heat fins  340  and/or thin heat exchangers  350  increases and improves heat convection. When the heat transfer coefficient increases, more power is produced by the thermoelectric converter  320 , and this increase can be more than the amount of power required to drive the air mover  360  along certain parts of the curve  400 . The line  410  shows the heat transfer coefficient when the air movement is zero or still, so the only removal of heat is due to thermal radiation or natural convection based on density gradients in the ambient air. The line  420  shows the limit of the heat convection, where the heat transfer coefficient is limited by solid fin efficiency and will not increase even if the air speed across the heat fins  340  and/or heat exchangers  350  is increased. The shape of the curve  400  indicates that there is at least one point of maximized increase power gained due to increasing the heat transfer coefficient relative to the power consumed by the air mover  360  to move the air to realize that gain the heat transfer coefficient. That point is marked as point  430  along the curve  400 . As can be seen, the presence of the air wavelets can increase the heat transfer coefficient between 5 to 10 times the value present without air flow. 
       FIGS.  5 A- 5 B  show suitable circuit diagrams for low-voltage rectifier configurations for the voltage rectifier  370 .  FIG.  5 A  shows a circuit diagram of a Schottky diode rectifier  510 , and  FIG.  5 B  shows a circuit diagram of a MOSFET rectifier  520 . These rectifier configurations are illustrative and exemplary only, as a person of skill in the art could use any voltage regulator configuration that can rectify the output voltage of the thermoelectric converter  320  based on its individual characteristics and environment. 
       FIGS.  6 A- 6 C  show aspects of a thermoelectric energy harvester  600  that may be used in the system  100  or the system  300 .  FIG.  6 A  shows the exterior of the thermoelectric energy harvester  600  including a heat sink  610  that is disposed above a base plate  620 . The base plate  620  may be made of a heat conductive material. In some embodiments, the base plate  620  may be made of or embedded with a PCM. Heat fins  630  may be disposed on the heat sink  610 . The heat fins  630  may be perpendicular or substantially perpendicular to the heat sink  610  in order to maximize the air flow between the heat fins  630 . The heat fins  630  may be long fins  633  extending from an air mover  640  or short fins  637  disposed between the long fins  633  and further from the air mover  640 . In some embodiments, the short fins  637  are optional. 
       FIG.  6 B  shows a cross-section of the thermoelectric energy harvester  600 . A thermoelectric converter  650  is disposed between the heat sink  610  and the base plate  620 . The air mover  640  may include a divided housing with an upper portion  643  and a lower portion  647 . 
       FIG.  6 C  shows a cross-section of the air mover  640 . The air mover  640  may include a yoke  660  that supports a permanent magnet  670 . Proximate to the magnet  670  is a voice coil  680  that can be induced to vibrate by a magnetic field generated by the magnet  680 . The voice coil  680  receives power from the power management component  120  through the feedback control circuit  380 . The voice coil  680  is in physical communication with a diaphragm  690 . The electrical currents in the voice coil  680  creates a fluctuating magnetic force on the voice coil  680  that in turn lifts the diaphragm  690 . The physical movement of the lifting and falling of the diaphragm  690  causes wavelets  365  of air to move in an out of the housing formed by upper portion  643  and lower portion  647 . The upper portion  643  and the lower portion  647  are configured to provide a channel  645  for air to move in and out of the air mover  640  when the voice coil  680  vibrates. The voice coil  680  may be any suitable galvanometer-like actuator that converts a magnetic field into vibrational energy as would be understood by a person of ordinary skill in the art. 
       FIGS.  7 A- 7 B  shown an alternative embodiment  700  based on moving the heat fins relative to the air rather than the air relative to the heat fins.  FIG.  7 A  shows a diagram of a thermoelectric energy harvester  700  that may be used with system  100 . The thermoelectric energy harvester  700  may include the heat sink  610  with heat fins  710 . The heat fins  710  may be splayed as to radiate outward from the center of the heat sink  610  or perpendicular to the surface of the heat sink  610 . The heat sink  610  is attached to the ambient side of the thermoelectric converter  640  while the base plate  620  is on the other side. In physical communication with the base plate  620  are one or more vibrators  720 . The vibrators  720  may be, but are not limited to, vibration motors and linear resonant actuators or piezoelectric transducers. In some embodiments, the vibrators  720  may be disposed between the base plate  620  and a lower surface  730 . The vibrators  720  are configured to transfer vibrational energy into the base plate  620  and, through the thermoelectric converter  640  and heat skin  610 , into the heat fins  710 . The movement of the heat fins  710  relative to the ambient air results in convection cooling of the heat fins  710 . The thermoelectric converter  640  produces an electric voltage when there is a temperature difference across the thermoelectric converter  640 .  FIG.  7 B  shows an alternative version of the heat fins  710 . The heat pin-fin spikes  740  may be attached to the heat  610  and radiate outward not as fins but as spikes, allowing the air to move around as well as across the heat pin-fin spikes  740 . 
       FIG.  8    shows a method  800  of harvesting energy using a temperature differential. In step  810 , the thermoelectric energy harvester  310 ,  600 ,  700  is positioned with a first side in ambient air with fluctuating temperature while the second side is in a stable temperature environment. In step  820  the thermoelectric converter  320  produces electrical power based on a difference in temperature between the first side  323  and the second side  327 . In step  830 , the electrical power is rectified by the voltage rectifier  370 . In step  840  the rectified power is stored in the power management component  120 . In step  850 , power from the power management component  120  is directed to an air mover  360 . In step  860 , the air mover  360  generates air wavelets directed at the first side  623  of the thermoelectric converter  620 . In step  870 , the power applied to the air mover  360  is regulated based on the increase of power generated by the thermoelectric converter  620 . 
     While the disclosure has been described with reference to exemplary embodiments, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications will be appreciated to adapt a particular instrument, situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.