Thermo-electric device to provide electrical power

A thermoelectric device to generate electrical power at high voltages, for example 110 volts to 900 volts, using a thermopile, a temperature differential applied to the thermopile and the Seebeck Coefficient of dissimilar materials assembled in a defined manner and in conjunction with controls and batteries to power electric devices.

TECHNICAL FIELD

A thermoelectric device to generate electrical power at selected voltages, for example 110 volts to 900 volts using a thermopile.

BACKGROUND OF THE INVENTION

The present invention relates to the field of devices used to generate power for electrical powered devices by converting a temperature difference into electrical energy.

An electric car, for example, generally uses several expensive and heavy batteries with a limited capacity, that is, miles per charge. Recharge stations for these vehicles require specialized chargers for the different types of batteries. These stations are expensive and require maintenance.

Many industrial, commercial and residential entities such as hospitals, factories, banks, commercial retailers, and so on require back-up power in case of power loss due to storms, accidents or other power failure. Data loss in banking and commercial enterprises can cost thousands of dollars or more. Many such entities have dedicated back-up generators, generally gas or diesel powered generators, which are automatically activated in event of loss of commercial power to maintain commercial or emergency operation. Computer and data backup are often in the form of large banks of DC batteries. Uninterruptible Power Supplies provide backup power for other computer systems. Space and remote habitat facilities require electrical power in isolated environments. Other commercial operations have processes that generate heat, which is wasted into the atmosphere but could be captured and turned into electricity.

Creation and use of electrical power for sustained periods without direct use of fossil fuels and without permanent connection to the electrical grid is severely restricted. The invention solves this problem of generation of electrical power without the direct burning of fuels and without the use of radioactive material.

SUMMARY OF THE INVENTION

The present invention utilizes thermocouples and the Seebeck Coefficient of dissimilar materials assembled in a unique manner and in conjunction with controls, a capacitance means, and batteries to power electric devices. The thermocouples connected in series comprise a thermopile generating electrical power at high voltages, for example 110 volts to 900 volts, from a temperature differential applied to the thermopile

The thermopile,FIG. 19, consisting of multiple thermocouplesFIG. 18, for example 100,000 thermocouples, is located so a temperature gradient applied to it with use of a material at selected temperatures, for example paraffin heated to 270 degrees Celsius or liquid nitrogen at minus 200 degrees Celsius, and ambient air temperature such that the thermopile generates DC voltages at two output terminals.

A control circuitFIG. 13, including switching transistors capable of switching currents and voltage in a range of amps and voltages in a range of volts is used to connect the thermopile to a capacitance means, such as grouping of capacitors capable of operating in a selected range of volts DC is connected to a control circuit and to rechargeable batteries and finally to an electronic load.

A Device Recharging System,FIG. 17, selectively connected to an external power source to reheat material used to create a temperature difference on the thermopile and simultaneously recharge batteries.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom, for modification will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention and scope of the appended claims. Accordingly, this invention is not intended to be limited by the specific examples presented herein. Rather, what is intended to be covered is within the spirit and scope of the appended claims.

Thermopile Construction

The present invention provides a thermoelectric device which can be designed to generate voltages, for example between 110V and 900V or more, using a thermopile consisting of a selected number of thermocouples in series, for example 100,000 thermocouples, exposed to temperature differentials and controls and batteries to power devices such as an electric load as described herein.

Based on the Seebeck effect, a small electrical potential is created across the length of a wire due to a difference in temperature along that wire. Thermocouples are created by connecting two sections of dissimilar metal at a junction with the opposite ends free, seeFIG. 18. A temperature difference between the junction connection23and the free ends of the two sections creates an electrical voltage between each of those free ends of the sections,90and91.

This effect is most easily observed and applied as shown inFIG. 18with a junction23of two dissimilar metals in contact, such as Nichrome 30 and Constantan 32, where the junction23of the two metals is at one temperature and the free ends,90and91, of the two materials is at a different temperature than the junction23. This translates to a voltage between the two ends,90and91. Most, if not all, pairs of dissimilar metals will produce a measurable voltage when their junction is heated or cooled relative to the temperature of the opposite free ends. Different combinations of selected metals produce differing voltages per degree of temperature difference.

The physical properties of materials include a Seebeck coefficient. For example, the Seebeck coefficient of Nichrome is +25 microvolts per degree Celsius. The Seebeck coefficient of Constantan is −35 microvolts per degree Celsius. If one end of a Nichrome wire is connected to one end of a constantan wire forming a junction23as shown inFIG. 18, the cumulative Seebeck coefficient of the thermocouple between the opposite ends90and91will be approximately: 25−(−35)=60 microvolts per degree Celsius. The Seebeck effect is typically linear in that the voltage produced by a heated junction of two wires is directly proportional to the temperature.

Two thermocouples,FIG. 19, connected in series can produce twice the voltage of one single thermocouple,FIG. 18. Three thermocouples produce three times the voltage of one thermocouple and so forth. The voltage increases proportionately with the number of thermocouples connected in series. Multiple thermocouples connected in series form what is called a thermopile. By connecting many thermocouples in series, as shown inFIG. 6, and creating a temperature difference at one side of the junctions71and a different temperature at the other side of junctions72, a thermopile can be constructed to produce substantial amounts of voltage between the free ends80and81ofFIG. 6.

For example, a thermopile can be constructed of two selected materials, for example Nichrome and Constantan, with Seebeck Coefficient properties such as to create a thermocouple.FIG. 1shows an arrangement of a thermocouple material (1)60, such as Nichrome sheet, of selected dimensions. Slots are created in the sheet wherein strips of material31remain between the slots of the sheet of material60leaving edges on the sheet30aand30b. The slot and material dimensions are variable. The edges30aand30bwill be removed at final assembly.

As shown inFIG. 3, the second thermocouple material (2)33, such as constantan sheet, can be formed from selected dimensions similar or equal overall dimensions of thermocouple material (1). However, the slots in this sheet are created at an angle,73, in relation to the slots of material (1). Again, edges are left on the sheet32aand32b. The angle of slots in material (2) in relation to material (1) is further shown inFIG. 19. The material and slot dimensions may vary.

As shown inFIG. 2, an electrically insulating material such as electrically insulating paper62is placed on top of the thermocouple material (1)60ofFIG. 1. The electrically insulating material allows for the tops and bottoms of the slots to be exposed as shown in the figure. The thermoelectric material (2) sheet is placed on top of the electrically insulating material, which is on top of the thermoelectric material (1) sheet. The assembly as shown inFIG. 4, then forms three layers, thermocouple material (1) as shown inFIG. 1on the bottom, insulating material as shown inFIG. 2in the middle, and thermocouple material (2) as shown inFIG. 3on top. As shown inFIGS. 2 and 4, the insulating sheet62is narrower than the width of the conductive sheets33and60. Therefore, as shown inFIG. 4, a selected portion of each electrically conductive sheet33and60containing electrically conductive sections31and64are in electrical conduction with one another on either side of the insulating sheet62at points71and72. Furthermore, conductive sheets33and60are arranged on either side of the insulator sheet62so that the ends of the section of thermocouple material (1), 31, and the ends of the sections of the thermocouple material (2),64, are in alignment and the two components overlap each other. The angle of the slots of thermoelectric material (2), as shown inFIG. 3item73and further shown inFIG. 4, is such that the top of the first thermocouple material (1) section,31, meets the top of one thermocouple material (2) section,64, at point71; the bottom of said thermocouple material (2) section,64, meets the bottom of the adjacent section of thermocouple material (1) at point72. Repeating this pattern forms a zig-zag pattern of sections of thermoelectric material (1) and thermoelectric material (2) creating a series of thermocouples. As stated and shown inFIG. 4, the ends of the sections of thermoelectric material (1)31and thermoelectric material (2)64, over lap at points71and72and are in contact with each other, on both sides of the assembly. Every overlapping section end is fastened together in electrically conductive contact at points71and72to form a thermocouple at these points of overlap only. When all section ends similar to points71and72are fastened together in this manner, multiple thermocouples are formed and linked together across the assembly. Each point across the assembly where the overlapping sections are fastened, points71and72, forms a thermocouple junction. The insulating material62ensures that the two thermoelectric materials are in contact at their end points, such as at71and72and similar points across the assembly.FIG. 5is shown for further clarification only and illustrates the assembly ofFIG. 4without insulating material62.

The tabs at the top and bottom of thermoelectric material (1) and thermoelectric material (2), as shown as items30aand30binFIG. 1and shown as items32aand32binFIG. 3, are removed after each of the points of overlap are fastened together. The result is shown inFIG. 6. As shown inFIG. 6, multiple thermocouples are therefore created in a chain from left to right. The assembly inFIG. 6is called a thermocard.

When the top junctions71of the thermocard inFIG. 6are exposed to one temperature and the bottom junctions72are exposed to a different temperature, a voltage difference is created between points80and81inFIG. 6.

The dimensions of the sheets inFIGS. 1 through 6can be altered to achieve different voltage and space requirements.

The electrically insulating material may be an electrical insulator such as MYLAR, polyethylene, styrene, electrically insulating paper or others.

The fastening of the section ends at points71and72ofFIG. 4andFIG. 6maybe accomplished by epoxying with electrically conductive epoxy, welding such as electric resistance welding, soldering, brazing, crimping together or by other means physically connecting the two section at those points in electrical conduction. They may also be connected via another conductive material such as copper wire.

The thermocard, when fully assembled can comprise a selected number of thermocouples, for example 200 thermocouples in a series. As shown inFIG. 7, multiple thermo-cards can be connected in series. The last thermoelectric material (2) section of a selected thermocard, point80, is electrically connected to the first thermoelectric material (1) section of the adjacent thermocard point81, as shown inFIG. 7. The connections may be made by crimping the ends of conductive wires to each of the elements and/or welding and/or soldering/brazing the ends or physically connecting by other mean as previously mentioned. Thus multiple thermocards can be connected in series in this manner to form a thermopile of desired size.

Therefore, if a thermocard consists of, for example 200 thermocouples, combining two thermo-cards in series results in 400 thermocouples in series. Three thermocards in a series results in 600 thermocouples in series and so on. A selected number of thermocards, for example 500 thermocards of 200 thermocouples each, can be connected in series to create a thermopile of 100,000 thermocouples in series economically and in a relatively small volume.

A plurality of thermocards65may be arranged in a radial pattern65as shown inFIG. 8, or in a block form74as depicted inFIG. 9or multiple block form76as shown inFIG. 10.

Example calculations are given below of the voltages, the number of thermocouples required and the subsequent number of thermocards required is given below for a temperature gradient of 220° C.:

575 Voltage Required

220 Temperature Delta Celsius

43561 Number of thermocouples Required

25 Length of each Thermopile Card (in)

5445 Total Length of Thermopile 138.3062 M

218 Number of Thermopile Cards Required

1.651376 angle per card in degrees

200 Thermocouples per card

43561 Total number of Thermocouples

It will be understood that the materials may also be clad to an electrically insulating substrate and thermocouple lines etched or printed onto the substrate as would occur in common printing of a circuit board.

It will be further understood that the electrically conductive sheets33and60may also be made by laser cutting, punching or mechanically milling the section and slot arrangements to shape. The shapes may also be made by chemically milling the sheets. The shapes may also be created by laying the thermocouple materials on a substrate similar to printing. Semiconductor and/or other polycrystalline materials such as bismuth and silicon may be used as thermoelectric materials provided by a process of growing crystals or otherwise leaving a coating of the material on a substrate similar to methods used in semiconductor manufacture.

It will be further understood that the thermocouple as shown inFIG. 12illustrates an electrical joining of two dissimilar metals such as copper and iron or other dissimilar metals such as Nichrome and constantan, or combinations of others including but not limited to materials such as: silicon; bismuth and bismuth alloys and compounds; iron; copper; aluminum; germanium and germanium alloys; polycrystalline Bi2Te3—PbTe; antimony; gold; tantalum; lead and lead alloys; alumel; chromel; tungsten; molybdenum, platinum, selenium, tellurium and crystalline tellurium alloys and compounds; Ag—Pb—Sb—Te quaternary systems; Half-Heusler compounds; High-ZT oxides; skutterudite compounds and other materials with Seebeck coefficients sufficient to generate useful voltage and/or current and/or power.

Controls

A control circuit, including switching transistors capable of switching a range of current and voltage is utilized to make use of the voltage created by the thermopile.

The control circuit operation is shown inFIGS. 13 through 16and Table 1. Switching transistors240,248,250,252, and253are shown as simple switches in the figures. As shown in Table 1 State (1) andFIG. 13, switching transistors240,248,250,252, and253are initially open. In State (2), the thermopile is connected to the capacitance means through switching transistors248and250closed with switching transistors240,252and253open, as shown inFIG. 14. State (3), the thermopile is disconnected from the capacitance means after the capacitance means is charged to the voltage of the thermopile with switching transistors240,248,250,252and253open, as shown inFIG. 13. State (4), the circuit connects the capacitance means first in series to rechargeable batteries through selected switching transistor240closed and switching transistors248,250,252and253open, as shown inFIG. 15. State (5), the circuit connects the capacitor/battery combination in series through switching transistors with an electrical device/load and closes the circuit to complete the capacitor, battery, load series loop, by switching transistors240,252and253closed and248and250open, as shown inFIG. 16. The capacitance means42is thus discharged through the rechargeable batteries22and supplied to the load24. The circuit then returns to its initial state (1), as shown inFIG. 13.

A diagram of the control circuit and its operating steps are shown inFIGS. 13-16and Table 1. The cycling of the switches is described in the Circuit Cycle table as follows:

Further explanation of the controls and operation is given as the following:

Charging the capacitance means to the voltage of the thermopile and then placing it series with the batteries in an open circuit, State (2), State (3) and State (4), results in the equivalent circuit shown inFIG. 20. The voltage between points100and101ofFIG. 20is equivalent to the voltage of the capacitors charged to the thermopile voltage. The voltage between points101and102ofFIG. 20is the voltage of the rechargeable batteries. The sum of the voltages of the capacitance means and the batteries is the voltage between points100and102ofFIG. 20:
Vtotal=Vcapacitors+Vbatteries

As shown inFIG. 16, the switches240,252and253are closed resulting the equivalent circuit shown inFIG. 21. The capacitance means42are then discharged through the batteries22and to an electronic load24at Vtotal. The current supplied to the electronic load24is the max drain rate of the batteries. The switching states 1 through 5 can be repeated at a selected rate.

The control circuit,FIG. 13, will consist of a printed circuit board with power transistors and timing circuit of standard design and manufacturing methods. The timing circuit of known art and not shown, will activate the switching transistors in a specific order and frequency.

Capacitors used may be, for example, approximately five 1000 μF 900 V, such as Cornell Dubilier Electronics (CDE) part number 947D102K901CJRSN. The switches may consist of selected MOSFETs, for example, STMicroelectronics model STY139N65M5 operated via a microcontroller such as Microchip Technology model number PIC24FJ128GA006T-I/PT.

In one example, if the total Seebeck coefficient of a nichrome-constantan thermocouple is 50×10−6V/° C., and the effective temperature difference is 100° C., and the number of thermocouples is 100,000; the voltage generated will be (50×10−6×100×100,000)=500V. The voltage is dependent upon the size of the thermopile, the extent of temperature difference, and the materials used in construction of the thermopile. As shown inFIGS. 13 through 16and described in Table 1, control circuitry20, as described previously, charges capacitors42using the voltage from the thermopile39. The voltage of the capacitors42is added to the voltage supplied by the rechargeable batteries22. For example, if the thermopile charges the capacitors to 500 volts and the capacitors are placed in series with a 12 volt battery in an open circuit, the voltage across the capacitor and battery series will be: 500 Volts+12 Volts=512 volts. The batteries are necessary because the thermopile produces a relatively small amount of current, in the range of milliamps, and cannot power a significant load alone. Whereas the batteries can supply significantly more current than the thermopile, such as drain rates of 10 A or more. Therefore, the voltage of the thermopile in conjunction with capacitors and the drain rate of the batteries combine to provide more power than batteries alone or a thermopile alone. The control circuitry may alternate the polarity of the terminals outputting this voltage to simulate an AC voltage to power AC loads such as AC motors or other AC electronic devices24.

Temperature Gradient Creation

The creation of the voltage by the thermopile is dependent upon creating a temperature gradient across it and the number of thermocouples used. For example, a source of heat, such as from thermal contact with heated material, waste heat from hot exhaust material, an exothermic chemical reaction, radioactive substance decay, solar heat, or some other means is applied to one set of junctions of the thermopile such at points71ofFIG. 6. The other set of junctions are exposed to a different temperature by some means such as a cooling fluid, ambient air, ground water, seawater, open space or other means. The thermopile generates DC voltage to power an electronic device depending on the number of thermocouples used and the extent of the temperature difference.

The present invention includes a method for applying heat or coolant to the thermopile as show inFIG. 11. A containment vessel16, containing either hot or cold material, is placed in thermal contact with one side of junctions of the thermopile39. The opposite junctions on the other side of the thermopile are exposed to a different temperature, such as ambient air.

For example, as shown inFIG. 11, a hot material such as paraffin may be placed in the containment vessel16at 270 degrees Celsius. The containment vessel16, being in thermal contact with one side of the thermopile39, increases the temperature of these junctions as previously described. The other, opposite junctions of the thermopile may be left in contact with ambient air at ambient temperature. Thus, a temperature difference is created in the thermopile and a voltage is created. This voltage is then used in the control cycle as described previously.

As shown inFIG. 11, the present invention includes a method for heating the material contained in the containment vessel16for use in creating a temperature gradient on the thermopile. The device may utilize a heating element17to heat material to a select temperature in the containment vessel. Said heating element may be connected to the electric utility grid on a temporary basis to heat the material in the containment vessel, such as paraffin, to the select temperature, such as 270 degrees Celsius. When the material is at the selected temperature the device is disconnected from the electric utility grid. When power is desired from the device, the heated material, in thermal contact through the containment vessel16with one side of the thermopile39, creates a temperature difference between both sides of said thermopile39, generating the selected voltage. The control circuit operation begins as described previously and the device can supply power until the material temperature returns to a temperature below which useful voltage is not produced by the thermopile. The device may then be reconnected to the electric utility grid or some other power source external to the device to reheat the material. This is further described later as a part of a Device Recharging System.

It is anticipated that hot or cold material, for use of creating a temperature difference across the thermopile, may be supplied commercially and/or externally to create the temperature gradient instead of being generated as a part of the Device Recharging System. If supplied external to the system, the hot or cold material can be directly added to the containment vessel similar to adding gasoline to an automobile. In this example, the material may be liquid nitrogen, dry ice, hot oil, hot paraffin, or materials that would create a temperature difference on the thermopile as described above.

It is also anticipated that the temperature difference across the thermopile may be created with use of waste heat from an existing process in a form such as hot exhaust, waste steam, or other by-product as the high temperature source and a fluid such as ambient air, seawater, ground water, coolant, or other material as the low temperature source.

Device Recharging System

The present invention can include the temporary use of externally sourced electricity, such as provided by the electric utility grid to recharge the system. The externally sourced electricity is used to heat material in the containment vessel, for example paraffin, to a selected temperature above ambient, for example 270 degrees Celsius, and simultaneously recharge batteries when the device is not in use to power an electric load. In one example shown inFIG. 17, the device is connected to the externally sourced electricity28, such as from the electric utility grid, to recharge the batteries22through a battery charger26and simultaneously power a heating element17. For example, the heating element may heat paraffin as the material contained in the thermally insulated containment vessel16, to 270 degrees Celsius. When the batteries are fully recharged and the material is heated to a selected temperature, the device will be disconnected from the external electric source. The material stored in the containment vessel16at the selected temperature and the recharged batteries22store energy for the device for portable use later when needed. When the batteries are drained and the material has cooled to the extent that power from the device is not useful to power the desired load, the device must be reconnected to the external power source, such as the electric utility grid, to recharge the batteries and reheat the material to the desired temperature. The device is then considered fully charged again. Thus, the device is not a perpetual motion device, but rather a rechargeable device.FIG. 17show this example of the system.FIG. 17shows the containment vessel16, the heating element17, the thermopile39, the control circuit20, the capacitors of the control circuit42, the rechargeable batteries of the control circuit22, the battery recharger26, an electronic load24, and an external electricity source that is temporarily connected to the device to recharge the system28.

Benefits of the System

A benefit of the system is to lessen the amperage supplied by the batteries for a given voltage electronic device requiring a given wattage. By using the high voltage of the thermopile, a high voltage load can be operated without requiring batteries alone to provide both voltage and current. Power=Voltage×Current, using the higher voltage requires less amperage for a given power output. For example, a 60 hp, 200V electric load requires roughly 224 amps. A 60 hp, 500V load requires roughly 90 amps. Thus, less amperage is required for the given power output of 60 hp because the device charges the capacitance means at the voltage of the thermopile. Less current from the batteries are required and battery life is greatly extended. Extending battery life would, therefore, extend the usable range of electric devices between recharging periods. This invention would also be beneficial in low power DC devices.

Another benefit is that waste heat from existing processes can be captured and turned into useful electricity. The system is also inherently suitable for marine applications where water is cold and vessels, such as submarines and ships, create waste heat in the form of exhaust and/or steam.

Another benefit includes the fact that electric devices and solid state systems are inherently more reliable and longer lasting than conventional internal combustion generators. There are less moving parts, less control and monitoring systems and emissions controls to fail in a purely electric system. The system is inherently suited to space systems and general aerospace systems since no oxygen combustion is required and the weight of fuel and combustion systems is avoided.

OBJECT OF THE SYSTEM

It is an object of this invention to use a hot or cold material, at a selected temperature and a second material at a different selected temperature, such as ambient air, to provide a temperature gradient which enables a thermopile to supply high DC voltage and to use the DC voltage in combination with capacitors charged by onboard batteries and control circuitry to power an electric device.

It is also an object of this invention to provide a thermoelectric power generator capable of generating DC voltage or single phase or three-phase AC voltage.

It is also an object of the present invention to create useful quantities of electric power by generating thermo electricity to assist and extend the life of batteries. Since power is voltage times current, by using the thermopile to create a voltage, the batteries can therefore provide lower current for a given power output, see page 20.

It is also an object of this invention to provide a thermoelectric power generator which includes rechargeable batteries which are recharged by input power by temporarily connecting the device to an external electric power source such as the electric utility grid.

It is also an object of this invention to include means to heat material for creating a temperature difference between the junctions of the thermopile, by temporarily connecting the device to an external electric source, such as the electric utility grid, such that voltage is created in the thermopile.