WO1994001893A2

WO1994001893A2 - Thermoelectric device and method of fabrication and thermoelectric generator and vehicle

Info

Publication number: WO1994001893A2
Application number: PCT/US1993/006297
Authority: WO
Inventors: Karol Bialy
Original assignee: TECHNOBEAM Corp
Current assignee: TECHNOBEAM Corp
Priority date: 1992-07-01
Filing date: 1993-07-01
Publication date: 1994-01-20
Anticipated expiration: 1995-01-01
Also published as: AU4662293A; WO1994001893A3

Abstract

This invention provides a new thermoelectric device and related method of fabrication with a relatively high conversion efficiency. One application, a thermoelectrically propelled vehicle, utilizes thermoelectric generators that generate electricity according to the Seebeck principle. The thermoelectric generation utilizes at least two parallel layers of alternating 'n' and 'p'-type elements, having hot and cold junctions connecting adjacent elements, that form series electrical connections within each layer. Each layer is thermally coupled in parallel with the other layers and is doped with a varying amount of cobalt, such that each layer realizes a different optimal thermoelectric temperature range. The layers cascade a temperature differential over the entire device, such that the thermoelectric device has a high conversion efficiency. The vehicle's thermoelectric generators use a graphite-based heat battery and a heat sink to provide a ΔT which may be made to exceed 2000 °F. A plurality of solar collectors are employed to collect and concentrate sunlight for heating of the graphite-based heat battery. Deceleration energy is fed back to the heat battery.

Description

THERMOELECTRIC DEVICE AND METHOD OF FABRICATION AND THERMOELECTRIC GENERATOR AND VEHICLE

This invention relates to the generation of energy from alternative sources and in particular to thermoelectric devices and related methods of

fabrication which efficiently generate electricity from a heat difference, and vice-versa. BACKGROUND OF THE INVENTION

With levels of pollution soaring in many parts of the word and encroachments upon the environment approaching a dangerous level that may well imperil us all, the need for alternate sources of energy has reached a new pinnacle. In fact, many individuals believe we are experiencing a new type of energy crisis; not one caused primarily by shortage of energy, but rather one caused by the side effects of its use. As a matter of global concern, there is an increasing need to develop alternate forms of energy; namely, sources that are more efficient and cleaner than those now used, and ideally, those which may be considered, in every sense, technological innovation and advancement, spurning additional development and research. This invention addresses these important needs by providing a new efficient means of generating electrical power from heat. The invention described by this patent makes direct thermoelectric conversion widely feasible, and it may be applied to any heat source. Below, background is provided to the basic principles of thermoelectric conversion and to the preferred implementations of the invention, including a novel electric car. 1. General Background.

Today, solar cells are popularly regarded as one of the most promising forms of generating electrical power from light. Solar cells apply a principle known as the "photovoltaic effect," which is the generation of a potential difference across two dissimilar materials when one of the materials is exposed to electromagnetic radiation, such as sunlight. Thus, for example,

bombarding a surface comprised of two different

materials, such as a semiconductor and a metal, with light creates a voltage between those two materials.

This voltage may be tapped and used to drive electric circuits, the "solar cell" maintaining its supplied voltage as long as it is exposed to light. Solar cells are currently used in various applications, such as some experimental electric cars, calculators, other low power consumer electronics, and for space applications (e.g., driving satellite electronics). However, for many potential applications, their high cost and relatively low efficiency have tended to make them rather

impractical and noncompetitive with conventional power sources. For example, at high noon on a bright day, sunlight will normally yield about one thermal kilowatt of energy for each square meter (about ten square feet) of light-collection area. Yet, since solar cells are typically only about ten percent efficient, ten square meters are needed to collect one electrical kilowatt of energy. Since a typical house may use in excess of six- hundred and fifty kilowatt-hours of electricity per month, a solar cell of enormous size and rather

prohibitive cost would be needed to meet the electrical needs of the house. In addition, batteries to store the electrical energy needed during hours when incident light is unavailable would also tend to be extremely expensive. Solar cells further tend to decrease in effectiveness over time due to damage from radiation received, despite necessary maintenance. Thus, direct light-to-electricity conversion is simply not generally cost effective under current technology.

This is not to say that solar energy is not currently used. There are many examples of applications that generate heat from sunlight. Greenhouses, for example, are one of the most common longstanding

examples of man's harnessing of the sun's energy.

Today, many structures feature solar-powered water heaters that heat water using heat generated from sunlight, using conventional water heaters to store the hot water and maintain its temperature.

Mankind has long harnessed naturally occurring heat, apart from that generated by sunlight. One example is the harnessing of geothermal heat. Of more recent vintage is the steam engine, which typically converts heat generated by burning wood or coal to mechanical energy, applied to propel trains and boats.

Conversion of the sun's radiation to electric power and the use of steam are but particular examples of the harnessing of natural heat. Other forms of generating energy from the radiation of heat also exist. Many people are, for instance, probably also familiar with use of nuclear radiation to generate electricity. This method utilizes radioactive isotopes that emit energy, thereby causing surrounding material to heat up significantly. This heat is typically placed in contact with water to thereby generate steam. This steam, conveyed through pipes, is utilized to drive turbines that generate electricity. It is upon this basic principle that most nuclear power plants operate. The current invention makes use of heat to directly generate electricity, without indirectly employing a steam/turbine arrangement. By using new microchip technology, an efficient source of electricity can be harnessed, as further described below.

2. The Thermoelectric Generator.

Traditional thermoelectric generation has used a compressible medium, such as steam, to transfer heat energy to mechanical action. In a simple steam

generator, water is heated in a boiler to create steam at high pressure. This steam then flows to a

superheater, where even more pressure is created. The steam is then applied against a mechanical element, such as a fan or a piston, and in so-doing, expands in volume, thereby losing temperature. The piston or fan drives a high voltage generator. The steam is

subsequently recondensed into water and recirculated to the boiler.

Of relatively more recent vintage, owing perhaps largely to the development of the semiconductor

industry, is the thermoelectric chip, a device that directly converts heat to electricity and also

electricity to heat, depending upon its application. As heat is itself a form of radiation, its application to certain materials excites migration of electrons in the materials to flow away from a cold material junction and towards heat, or vice-versa, depending upon the

material. The term "thermoelectric device," as used herein, includes, but is not limited to, any device that converts heat directly to electricity by use of heat radiation to excite migration of charge within a

material. However, even with the development of the semiconductor industry, the thermoelectric device has not been very widely used, because of its relatively low conversion efficiency of normally only a few percent. To date, its most practical uses have tended to be in space applications, for example, to generate heat from sunlight, or where vast sources of heat are available and not usable for other purposes, such as where there exists a hot exhaust. Examples of these applications may be seen with reference to my previous patent, U.S. Patent No. 3,379,394, and also U.S. Patent No.

4,095,998, respectively.

The present invention presents a thermoelectric device having efficiency as yet unachieved by other known semiconductor construction. As seen below, thermoelectric devices, including a novel thermoelectric generator provided by the present invention, operate upon a principle known as "the Seebeck principle."

3. The Seebeck Principle

Thermoelectric generation is based upon a principle, discovered by Seebeck in 1821; namely, that current is produced in a closed circuit of two

dissimilar metals if the two junctions are maintained at different temperatures. This principle and its inverse relationship, the Peltier principle (which points out that a junction of two thermoelectric materials may be heated or cooled by passing current through the

junction) are illustrated with reference to FIG. 1.

According to one implementation of these principles, electrons in an "n"-type semiconductor material 11 migrate away from the heat source 13, while electrons in a "p"-type semiconductor material 15 migrate toward the heat source . This enables the construction of an electric power source by connecting thermojunctions 17 and 19 in series electrically and in parallel thermally. In other words, p and n type elements 11 and 15 are postured alongside each other, forming a group of thermojunctions that are

perpendicular to the direction of heat propagation, with each p/n element abutment being coupled by a hot

junction 17 (that is, electrically connected at the end of their abutment to the heat source), and each n/p element abutment being coupled by a cold junction 19 (that is, electrically connected at the end of their abutment opposite the heat source and maintained at cold temperature). An end "n"-type element 21 is tapped for negative potential at a cold junction, whereas an end "p"-type element 23 is tapped for positive potential at a cold junction. The cold junctions are thermally coupled by a heat sink 25, which maintains the cold junctions 19 at a substantially uniformly cool

temperature.

Thus, an arrangement utilizing the Seebeck principle typically feeds heat to a semiconductor material and generates electricity driven by a

temperature gradient across the semiconductor material. The efficiency of the heat-to-electricity energy

transference is primarily a function of the hot junction temperature, T_HOT' the temperature difference between the hot and cold junctions, ΔT = T_HOT - T_COLD, and a quantity known as the "figure of merit," Z, which varies for each material.

Thus, different materials have different thermoelectric applications, depending upon the heat source temperature and the specific range of heat difference across the semiconductor. However, the materials currently used have relatively low conversion efficiency, because typically, only one thick layer (typically ¼ to ½ inch thick) of semiconductor materials is used, depending upon the heat source temperature and the gradient of the temperature loss across the

semiconductor material.

4. Application Of Thermoelectrics To Electric

Vehicles

One of the principal applications of the current invention, discussed below, is to electric vehicles. Electric vehicles have recently been placed in the limelight because of soaring air pollution levels in various parts of the world. Various types of electric vehicle drives have been proposed, including Solar- electric vehicles and electric vehicles that operate on conventional electric power received by the car and stored in large batteries. However, neither the solar electric vehicles nor the stored electricity vehicles are capable of supplying electric power sufficient to drive the car for the extended periods of time necessary in many circumstances. Pursuant to current technology, electric vehicles that operate on stored batteries typically only have a range of only 60 to 150 miles at highway speed, necessitating frequent recharging.

Similarly, solar cells of the type discussed above tend to be expensive and fragile, and typically require significant space on the car's exterior for generation of sufficient electric power to drive the vehicle.

Solar electric vehicles are typically slow and can generally only be operated during the daylight, unless they are equipped with large chemical batteries that are capable of storing generated electricity through hours of darkness. 5. Statement of Problem.

It must be stressed that the Seebeck principle is by no means new, having been discovered in 1821.

Rather, what has been missing to date is a method and construction that enables more practical and widespread usage of the Seebeck principle to provide efficient and effective thermoelectric generation, including

generation of electricity from a wide variety of heat sources, including sunlight and small-scale radioactive sources. Thus, there is a need for an invention that provides for more efficient thermoelectric conversion and allows for more widespread usage of thermoelectric devices. There is further a need for thermoelectric devices which permit direct conversion of heat to electricity in a manner that minimizes waste of heat energy. Additionally, such devices should be usable in different environments, and not limited to situations where vast amounts of heat are plentiful, or alternative applications of thermal energy impractical. The current invention addresses these needs, and provides a new thermoelectric device and thermoelectric generator which has more efficient thermoelectric conversion and tends to be usable in a wide variety of applications. There is also a need for an electric vehicle with extended range and improved power. Thermoelectrics offers important applications to electric vehicles, because electric power can better be generated without the need for extensive electric battery storage

capacity. Thus, today's society and levels of pollution demand an electric vehicle that is practical, and has improved power storage capability and efficiency. More particularly, there is a need for a vehicle and

associated power source that overcomes the

aforementioned problems and provides further, related advantages. SUMMARY OF THE INVENTION

The present invention provides a new

thermoelectric device and related method of fabrication having an heightened efficiency of conversion that makes thermoelectric conversion more practical, with a wide range of applications to electrical power generation, heating and cooling which were not previously thought to be practical. The present invention also provides a thermoelectrically propelled vehicle having a range which may exceed six hundred miles, with ample supply of generated electrical power to allow the electric vehicle to travel at highway speeds. The invention as defined by the appended claims may be characterized as providing (1) a thermoelectric device having heightened conversion efficiency, (2) a thermoelectric generator and (3) a thermoelectrically powered vehicle, whereas other similar vehicles would have been primarily powered by chemical fuels or other energy sources and generally have higher associated cost and reduced maximum range.

In one aspect of the invention, the

thermoelectric device of the current invention includes at least two parallel thermoelectric layers, each adapted for thermoelectric conversion at cascading temperature brackets within the overall temperature difference across the thermoelectric device. More particularly, each layer includes adjacent "n"-type and "p"-type elements that are electrically connected in series either to produce a heat difference across the layer when driven by electric current, or to create a potential difference when a heat gradient exists through the layer. The thermoelectric device may consist of many layers arranged in series thermally, each efficiently operating within a discrete temperature range.

In another aspect of the invention, the thermoelectric generator of the current invention includes a heat source, a heat sink, and a

thermoelectric device having at least two thermoelectric layers therebetween, for generating electricity over cascading temperature gradients. More particularly, a plurality of thermoelectric modules may be mounted between a heat dissipation region of a heat battery and a heat sink, the thermoelectric modules wired

electrically in parallel to provide current density and in series to generate voltage. The heat source may include a solar energy source that collects light and concentrates the light onto a heat battery, which is heated thereby and used to drive the thermoelectric generation. Alternatively, radioisotope heat generation may be used as the heat source, or any other convenient means of generating heat.

In still another aspect of the invention, the thermoelectric driven vehicle provided by the current invention utilizes a heat source and at least one thermoelectric generator for converting the heat into electrical power to drive the wheel motors of the vehicle. More particularly, the vehicle may feature solar collectors for collecting light and providing the light to a heat battery, an electric heating element for charging the heat battery using an electrical outlet, a power regulation distribution center and a regenerative braking system for causing transference of the energy of the vehicle's motion into heat, and infusing thermal energy into the heat battery, to cause the vehicle to decelerate. The invention may be better understood by referring to the following detailed description, which should be read in conjunction with the accompanying drawings. The detailed description of a particular preferred embodiment, set out below to enable one to build and use one particular implementation of the invention, is not intended to limit the enumerated claims, but to serve as a particular example thereof.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration used to explain the Seebeck and Peltier principles, and shows three

semiconductor junctions, including two "n"-type elements and two "p"-type elements, and the interaction of those junctions with a heat gradient;

FIG. 2 shows a lengthwise cross-sectional view of a thermoelectrically powered car utilizing the principles of the current invention, where the heat source utilized includes three solar collectors;

FIG. 3 shows a cross-sectional view of one of the three solar collectors of FIG. 2;

FIG. 4 shows a top plan view of the car shown in FIG. 2, illustrating in phantom lines the solar energy collection and distribution system, including

distribution of collected solar energy to two

thermoelectric generators;

FIG. 5 is a block diagram of the power system of the car of FIG. 2;

FIG. 6 is a top plan view of the power system shown in FIG. 5, showing the location of elements "under the hood;" FIG. 7 shows a block electrical diagram of the car shown in FIG. 2, including motor elements, operator controls, thermoelectric generation elements, chemical battery and magnetic reed relays; FIG. 8 shows a perspective view of a

thermoelectric generator of the current invention, and shows a heat battery, a plurality of thermoelectric modules, and a heat sink;

FIG. 9 shows a cross-sectional view of the thermoelectric generator of FIG. 8 with the heat sink installed to overlie the heat battery and thermoelectric modules, and also showing the heat battery fitted with a center insert that carries fiber optic bundles for termination inside the heat battery;

FIG. 10 is a cross-sectional view of the thermoelectric generator, taken substantially along lines 10-10 in FIG. 9; and FIG. 11 is a perspective view of the

thermoelectric device provided by the current invention, showing a plurality of thermoelectric layers tailored to cascading temperature ranges. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The current invention provides a new

thermoelectric device and a related method of

fabrication with a relative efficiency of conversion between heat gradient and electricity to an extent not previously realized. This thermoelectric device may be incorporated into a thermoelectric generator and

preferably, but not necessarily, a portable generator that may be used to generate electricity, provide a desired temperature, or generate electricity to drive an electric vehicle. As will become apparent below, the device also has a number of other applications as well. The present invention further provides a novel and thermoelectric generator and thermoelectric powered vehicle. Referring first to FIG. 2, the preferred

thermoelectrically powered vehicle 27 that exemplifies the present invention is shown in cross-section. The vehicle 27 has three solar energy collectors, 29, 31 and 33, each respectively mounted on the hood 35, roof 37 and trunk 39 of the vehicle. Each of these collectors is approximately 1 meter square in surface area, and features a lens element 41 that focuses collected solar radiation to a second smaller surface area, a light entry point of the collectors 43, where the light is captured by a plurality of fiber optic bundles 45.

(See, FIG. 3).

FIG. 3 illustrates the distribution arrangement for distributing the collected focused solar energy to two thermoelectric generators 47 and 49. As depicted in FIGS. 2 and 4-6, generated electrical power from the thermoelectric generators 47 and 49 is fed to a power regulation and distribution system 51 where the power is regulated to drive DC wheel motors 53 and 55, store electrical power in a chemical storage battery 57, located at the rear 59 of the car, and drive peripheral electronics 61, such as climate control, radio, lights, etc. (not shown) indirectly by way of the chemical storage battery.

Referring to FIG. 3, the solar energy collectors 29, 31 and 33 will be explained in additional detail. The lens element 41 of each collector 29, 31 and 33 is mounted integral with the hood, roof or trunk of the car. It includes a fresnel lens 63 which refracts light rays 65, 67 and 69 incident from the sun to a light entry point 43 of the fiber optic bundles. The fiber optic bundles 45 are borne within the vehicle structure 71 and feature an abrupt right-angle turn 73 to a region where the collected solar energy is further focussed to provide additional concentration to the light. Since one square meter during peak daylight hours will yield about 1 kW of light energy, the three solar collectors 29, 31 and 33 will typically provide the equivalent of three kilowatts of electrical power, which is carried by the three fiber optic bundle paths 75, 77 and 79

illustrated in FIGS. 2 and 4. These three fiber optic bundle paths 75, 79 and 79 carry the concentrated light to a solar energy distribution center 81, located in the front 83 of the car and adjacent to the power regulation and distribution system 51. The fiber optic bundles 45 may be composed of standard plastic fiber optics, "PPNA" in the case of the preferred embodiment, but should advantageously be capable of withstanding heat of up to 400° F created by the conveyance of the concentrated light to the solar energy distribution center 81.

The solar energy distribution center 81 receives the three path-groups of fiber optic bundles 75, 77 and 79 and distributes and further concentrates the focused collected solar energy into an even smaller cross-sectional area which is distributed between two glass fiber optic bundles 85 and 87 which carry the

concentrated solar radiation directly into the

thermoelectric generators 47 and 49, shown in FIG. 4. The transition from plastic to glass fiber optic media is manifestly advantageous, since the thermoelectric generators 47 and 49 are called upon to generate heat of over 2000° F. The solar energy distribution center 81 features a tapered termination to each fiber optic bundle 45, which further concentrates the already focussed solar energy into the two paths of glass fiber optic bundles 85 and 87. Thus, a plurality of fiber optic bundles 45 (in three groups, 75, 77 and 79) from the three solar energy collectors 29, 31 and 33 are divided into two paths (85 and 87) to the thermoelectric generators 47 and 49, and tapered into the two glass fiber optic bundles 85 and 87. This tapering will provide additional amplification that allows for the generation of the 2000° F that is utilized for

thermoelectric generation. It will be appreciated that various other kinds of fiber optic media and

arrangements of fiber optic bundles can be employed.

The two thermoelectric generators 47 and 49 are positioned in the front left and right portions 89 and 91 of the car, beneath the hood, and as shown in FIG. 8, include a graphite heat battery 93, a plurality of thermoelectric modules 95, and a heat sink 97, which creates a heat gradient between the heat battery 93 and the exterior 99 of each of the plurality of

thermoelectric modules 95, which enables each of the plurality of thermoelectric modules to generate a potential difference, as is described in additional detail below. The heat sink 97 is substantially a hollowed cylinder having a plurality of radial fins 101 for keeping the heat sink cool. As used herein, "heat sink" refers to any device capable of supplying a relatively uniform reference temperature to one side of the thermoelectric modules. In the preferred

embodiment, the utilized heat sink is made of copper and maintains the thermoelectric modules' exteriors at approximately 100° F. Thus, this configuration for each of the two thermoelectric generators 47 and 49 will provide a temperature gradient of approximately 1900° F. The basic components of the thermoelectric generator are shown disassembled in FIG. 8.

As depicted in FIG. 11, each of the

thermoelectric modules 95 includes ten thermoelectric layers 103 (four of which are shown in FIG. 11), each of which generates electricity when a heat gradient is placed across it. The thermoelectric modules 95 feature thermoelectric layers 103 which are configured in series thermally, that is, the ten parallel layers have one large heat gradient across them with each layer adapted to operate most efficiently in generating a potential difference over a specific cascaded temperature range of the heat gradient. In other words, the layer closest to the heat battery may feature a heat gradient of 2000° F - 1850° F, while a tenth layer furthest from the heat battery may experience a temperature gradient of 350° F -

100° F. The fabrication and usage of these

thermoelectric modules 95 will be described further below.

Each layer 103 of each thermoelectric module 95 is electrically coupled in parallel to each other layer 103 within that module. In other words, all of the layers 103 of each thermoelectric module 95 produces the same voltage output as any other layer 103, but all of the layers are connected together to provide a greater current density. In addition, each thermoelectric module 95 is also electrically coupled in parallel to every other module 95 within a given column for further increasing the current density. The electrical output of each the thermoelectric generators 47 and 49 is coupled to the power distribution center 51 which

supplies a relatively low-voltage, i.e., ½ V to 1 V, of high amperage.

The novel thermoelectric vehicle 27 of the present invention has an efficient system for maximizing the efficiency of use of the collected solar energy.

With reference to FIG. 5, the wheel motors 53 and 55, which are mounted at each of the left and right front tires to separately drive rotation of those tires, each have a DC wheel generator as part of a regenerative braking system 105. When the vehicle operator depresses a brake 113 (FIG. 7), the DC wheel generators are engaged, causing the car to decelerate. The vehicle's deceleration causes the wheel generator to generate electrical power, in roughly the reverse manner in which electrical power fuels an electric motor. The generated electrical power is fed to a power control circuit 107 which feeds a spiral tungsten heating element 108 (FIGS. 9-10) that is mounted at a bore 111 of the heat battery 93. The bore 111 also receives a glass fiber bundle 85 or 87 from the solar energy distribution center 81, illustrated by the reference numeral 109 in FIGS. 9-10. Thus, when the operator of the vehicle steps on a brake 113, electricity is generated and turned into heat, turning the car's velocity back into heat for subsequent reuse. The regenerative braking system includes the DC wheel generator that is built into the same housing as the wheel motors 53 and 55, and

preferably constitutes a dual winding about the wheel's axis. Thus, the wheel generators will generate

electricity at 12 VDC whenever their respective wheels turn.

The power control circuit 107 also regulates electrical power received from external power inputs 115 and 117, located at the front 83 and rear 59 of the vehicle. Thus, during nighttime hours, when solar energy is not available, or when quick charging of the heat battery 93 is desired, the vehicle operator may stop the vehicle and plug an external power coupling (not shown) into either or both of front and rear external power inputs 115 and 117 (see FIGS. 2 and 5-7) and thus charge the heat battery 93 through regulation of the heating element 108 by the power control circuit 107. The heating element 108, which is fabricated of tungsten, heats the heat battery 93 far more quickly than the collected solar energy when it is supplied with power of relatively high voltage, on the order of

120/220 volts. The power control circuit 107 provides both power regulation of both the external power inputs 115 and 117 and the regenerative braking system 105. Of course, the 120 VAC external inputs may be used to directly heat the tungsten, and consequently, the power control circuit is an electronic circuit that preferably switches between the regenerative braking system 105 and the external power inputs 115 and 117, the latter used only when the vehicle is stopped. It will be observed that the design of the power control circuit 107 is well within the skill of anyone with an understanding of electronics and is not considered necessary for an understanding of the invention. Control of power from the power distribution system 51 to the wheel motors 53 and 55 is achieved by a magnetic reed relay system 119, a simplified schematic of which is shown in FIG. 7. Unlike a conventional car, the acceleration and deceleration of the vehicle is achieved by an accelerator pedal 121 which controls both increase of the electrical power supplied to the wheel motor, and decrease of the same. Since most vehicle operators are accustomed to using both an accelerator pedal and a brake, the brake 113 of the vehicle

described herein is mechanically tied to the accelerator pedal 121, such that depressing the brake 113 controls raising of the accelerator pedal to decelerate the vehicle. The operator controls, including the ignition switch 123, the brake 113, the accelerator, pedal 121 and a forward/reverse control 124, are generally designated in FIG. 5 by the reference numeral 125.

The plastic fiber optic cables (of paths 75, 77 and 79), which may be composed of "PPNA", carry

concentrated light from the solar collectors 29, 31 and 33 to the solar energy distribution center 81, for further concentration and distribution to the two sets of glass fibre optic bundles 85 and 87. The plastic fiber optic bundles 45 have a relatively high loss of the solar energy, compared to the glass fiber optic bundles 85 and 87, which are approximately 99 %

efficient. The glass fiber bundles 85 and 87, as shown in FIG. 9, enter the heat battery 93 through the bore 111 as a centralized insert 109. The various fibers are terminated radially outwardly within the insert 109, as shown in FIG. 9, so that light is focused on the

interior of the bore 111 of the graphitic heat battery 93. In this manner, solar radiation is directed

radially outward towards the graphitic heat battery to impinge upon the heat battery 93 and generate heat at the heat battery's center axis. The heat battery 93 retains its heat which is transmitted to the cylinder's outer periphery 127 and used to generate electricity in accordance with the principles of the invention.

Preferably, the graphite core (of the heat battery 93) also possesses the spiral tungsten strip 108, as

discussed above, which may be used to apply heat to the heat battery. For example, in accordance with the solar thermoelectric vehicle 27 provided by the current invention, at night time, when the external solar collectors 29, 31 and 33 are no longer able to provide significant amounts of heat to the heat battery 93, the vehicle 27 may be stopped and an external power input 115 or 117 engaged with a power source, such that the tungsten elements of the insert 109 heat the heat battery 93. As mentioned, since the graphite is

expected to retain this heat for four hours or longer, this heating will provide a ready source for electric power for several hours of driving thereafter.

External to the heat battery 93 and its blanket of thermoelectric modules 95, is the heat sink 97, which maintains the outer surface of the thermoelectric chips 99 that faces away from the heat battery at a relatively cool temperature. In the preferred embodiment the heat sink 97 is selected to maintain the outer surface 99 of the thermoelectric modules 95 at approximately 100º F. The array of glass fibers from groups 85 or 89 within the core of the heat battery causes the heat battery 93 to ideally to be heated to over 2000º F. Thus, a temperature difference of approximately 1900º F is maintained across the width of the thermoelectric modules 95. Since this heat difference is applied to a cascading array of discrete thermoelectric layers 103, each optimally designed to operate over a different temperature range, this construction of this invention will enable an optimal conversion between a heat

gradient and electricity to an extent not before

realized, since only one relatively thick thermoelectric layer is generally used for electrical generation, or generation of heat from electricity.

The heat sink 97 may be comprised of any material suitable for use as a heat dissipator, for example, copper or aluminum. As observed in FIG. 8, the heat sink 97 is shaped as a hollow cylinder, the

cylinder receiving the heat battery 93 and its blanket of thermoelectric modules 95 within its inner periphery, as shown in FIGS. 9 and 10. The heat sink 97 also has a plurality of radial fins 101 that increase the surface area of the heat sink exposed to air. Since the heat sink 97 is composed of a material that dissipates heat as rapidly as possible, the fins 101 increase the surface area over which heat may be dissipated, enabling a much cooler cooled junction of the thermoelectric chips 95 than otherwise would be possible.

A. Fabrication and Use of the Thermoelectric Modules

Each of the thermoelectric modules 95 are advantageously semiconductor chips which, as shown in FIG. 8, are arranged in a row/column array around the periphery of the heat battery 93. The modules are bonded to the heat battery by any suitable epoxy, which may preferably be a material known as "Silastic," avai able from the General Electric Company of

Waterford, New York. The modules 95 are manufactured to electrically couple together when placed in abutting contact with a module lying in the same plane. As shown in FIG. 8, each module 95 within a column 129 fits to the module above and below, in adjacent rows 131, to electrically couple in parallel to adjacent modules, such that each column is a parallel electrical coupling of all modules in the column. Each column electrically contacts a bus bar 132 and 133 (See, FIG. 9), respectively located at the top and bottom of each thermoelectric generator 47 and 49. The contacts between adjacent modules may be made by copper

male/female arrangements (not shown), with sputter deposited copper post within the module coupling both the top and bottom of each module for the parallel electrical coupling. The chip fabrication process will be described further below. This arrangement of

parallel modules provides power density to the electric charge provided by each thermoelectric generator.

Each module 95 includes a semiconductor chip having an electrical parallel connection of a plurality of discrete thermoelectric layers 103, arranged

thermally in series, or parallel to each other across the heat gradient created between the heat source and the heat sink. Each layer may be of a different

material composition, which is to say, the

thermoelectric characteristics of each layer 103 may differ from other layers such that each layer is

particularly tailored for a distinct ∆T. More

particularly, each layer may be composed of the same single material, and varied in thickness or doping to achieve the difference in thermoelectric

characteristics, or composed of alternate substances, or be composed of identical substances of identical

thicknesses of varying degrees of doping. The "heat source," as used herein, is any device that provides a first temperature, while the heat sink 97 is any device that applies a reference temperature, whether hotter or cooler than the heat source, such that one side of the chip is relatively hot and the other side relatively cooler. The heat differential across the chip results in a heat gradient within the chip, which causes a series of potential differences within the chip

according to the Seebeck principle.

To provide the maximum efficiency of conversion of heat-to-electricity possible, the chip has a

plurality of thermoelectric layers 103 (ten, in the preferred embodiment) that are individually tailored to operate within cascading temperature ranges. For example, if the heat differential across the chip is 2000º F to 100º F, the first layer might correspond to the range 2000 - 1850º F, the second 1850 - 1670º F, etc. Each layer possesses a "Figure of Merit" (a numerical quantity used to measure the thermoelectric conversion characteristics of a material, dependent upon electrical resistivity and thermal conductivity and expressed by the formula Z = S²/ρK, where Z is the

Seebeck coefficient, K is the thermal conductivity and ρ is the electrical resistivity) that will produce an optimal efficiency of conversion for the layer's

corresponding temperature range. As efficiency of thermoelectric conversion is a function of the Figure of Merit for the particular material, ΔT and the hot junction temperature of the material, a layer of a given thermoelectric material may have its efficiency of conversion optimized for a particular temperature range by adjusting the thermal conductivity K of that

material. This generally also alters the electrical resistivity ρ of the material, which is tied to the thermal conductivity.

In the preferred embodiment, each thermoelectric layer 103 has a plurality of "n"-type and "p"-type elements that are composed of the same base materials. The layers 103 are optimized to a particular temperature range ΔT by doping these elements with a metal to increase thermal conductivity K and decrease electrical resistivity ρ. A layer 103 with a greater degree of doping provides greater thermoelectric conversion at relatively high temperature, while having a relatively small temperature drop across the layer's thickness.

Conversely, a layer with a lesser amount of doping works best at a low temperature, but has a relatively greater temperature drop ΔT across the layer's thickness. Incidently, the converse of what has been said is also true, namely, a thermoelectric layer that generates electrical power in response to a heat

gradient is also inherently capable of generating a heat gradient in response to electrical power. Thus, what has just been described as the principles underlying the layering of the thermoelectric module also apply for instances where the thermoelectric module (the preferred example of the thermoelectric device referred to in the claims) is to be used for climate control, to heat, or to refrigerate, or both.

The potential difference generated by each of the individual layers in response to the thermal

gradient is coupled electrically in parallel with the other layers 103, such that each module or chip 95 produces one potential difference that is generally the same as any given layer, but with a current density that is the product of the cascading temperature ranges of the heat differential between the heat battery side of the chip and the exterior of the chip that will abut the heat sink. It is stressed again that the thermoelectric module described may be used not only to generate electricity from heat according to the Seebeck effect, but also inherently is capable of driving a heat

differential when supplied with the electrical power according the principles of the Peltier effect. Thus, a thermoelectric module provided by the current invention would feature a reduced load presented by the relatively thin thermoelectric layers 103, each layer generating a heat differential in series with the other layers 103. In addition, it is well within the principles of the invention to couple each of the ten thermoelectric layers 103 within the module in series electrically, to provide a greater potential difference output with reduced current density, and correspondingly, to

generate a temperature differential from a voltage supply as opposed to a current supply. These alternate configurations are implemented simply by adjusting the masks used to manufacture the chip, which is well within the skill of one familiar with semiconductor

manufacture. Thus, the thermoelectric chip provided by the invention may be used to create heat or

refrigeration from electrical power, or electricity from a heat differential. As mentioned above, in the preferred embodiment, the thermoelectric module 95 includes approximately ten discrete layers 103 of a single base material with a variance in doping that correspondingly alters the figure of merit for each discrete layer. In the

preferred embodiment, each layer is formed of

alternating "n"-type and "p"-type semiconductor elements 11 and 15, with the "n"-type elements being formed of gallium arsenide and the "p"-type elements being formed of bismuth telluride. Alternatively, lead telluride, germanium telluride, silver antimony telluride, tin telluride and any other suitable material where

electrons flow against the heat gradient may be used as the semiconductor element 15. Similarly, germanium, silicon, or any similar material wherein electrons flow with the heat gradient, is suitable for use as the element 11.

These base materials are doped with a varying amount of cobalt, or other metal, to alter the electric resistivity ρ and thermal conductivity K within each layer 103 of each module 95. For example, as shown in FIG. 11, the first layer 134 closest to the heat battery 93 is the most heavily doped with cobalt, to the extent of some 0.06 %. Thus, the thermal conductivity K in that layer will be quite high and the electrical

resistivity ρ within this first layer 134 will be quite low, due to the greater electron mobility provided by the greater metal presence. Thus, this first layer 134 operates upon a relatively small temperature

differential across the layer with a relatively high amount of electron migration. By contrast, the tenth layer (furthest removed from the heat source, designated by the reference numeral 135 in FIG. 11, which for simplicity only shows four thermoelectric layers 103) is doped to about 0.03 % with cobalt. Thus, the outermost layer 135 has a relatively larger ΔT, which contributes to its efficiency of thermoelectric conversion. The precise quantity of doping for each layer is empirically determined depending upon the temperature range desired in connection with a particular application. Thus, in the preferred embodiment, while the doping is not precisely linear across the module 95, it is

advantageously roughly linear such that the second layer 136 is doped with about 0.057 % cobalt, etc. The first layer 134 is separated from both the heat battery 93 and the second discrete layer 137 by an electrical insulator 139, which also serves as a thermal conductor so that the heat is not wasted across the thickness of the electrical insulator 139 (FIG. 11 does not show the electrical insulator between the first layer 134 and the source of heat). The preferred material for this insulator is a silica based material, preferably a ceramic mica. This insulator 139 may either be a substrate over which conduction elements and the "n"-type and "p"-type elements may be deposited, or the insulator may be separately deposited using

conventional sputtering techniques over the

thermoelectric elements of a previous layer. Thus, the thermoelectric module 95, including all ten discrete thermoelectric layers 103, may be sputter deposited in one proceeding. Alternatively, discrete thermoelectric layers 103 may be severally manufactured and bonded together by a press and sintering process, which is commonly used to manufacture semiconductor devices.

The fabrication of the thermoelectric modules 95 will now be described. Each thermoelectric layer 103 is fabricated in the same basic manner. One begins with a silica-substrate, preferably composed of a ceramic mica. Using masking techniques, such as with a wire mesh, copper is sputter deposited onto the substrate to form electrical contacts 17 that will abut "n" type and "p" type elements at the n/p junction. Second, one of the "n" and "p" elements are deposited using a different mask configured to allow "n" and "p" elements to allow the copper contact at the junction. Third, the second of the "n" and "p" elements is deposited using yet another mask such that the "n" and "p" elements lie in parallel relationship above the metallized substrate. For each layer 103, the substrate is masked for the metal contacts that will be placed upon that

substrate (and also on the bottom of the substrate if the substrate is to serve as an insulator in between two thermoelectric layers, as further described below).

Using the masks, one sputter deposits copper onto the substrate to form the conduction channels for one of the n/p or p/n junctions, 17 and 19, respectively (alternate junction conduction channels are place on opposite sides of the thermoelectric layer as noted with reference to the conduction channels 17 and 19, shown in FIG. 1) . The copper may be deposited using conventional masking techniques, for example, using a wire mask. Once the conduction channels 17 and 19 have been deposited, the mask is removed and a second mask used to deposit one of the "n"-type and the "p"-type elements 11 and 15 that experience electron migration when exposed to a heat gradient. As mentioned, the preferred

embodiment employs gallium arsenide as the "n"-type element, in which electrons flow with the heat gradient towards the cool junction, and bismuth telluride as the "p"-type element, in which electrons flow against the heat gradient towards the hot junction. A third mask is then used to deposit the other of the "n"-type and "p"-type elements. Notably, the second and third masks are not negatives of one another, since the alternating elements must remain in electrical insulation from one another except at the copper contacts 17 and 19. In the preferred embodiment, a vacuum is used as the electrical insulator.

Once both alternating thermoelectric elements 11 and 15 have been deposited, the fabricated layer is ion bombarded with a metal that increases the layer's thermal conductivity and decreases its electrical resistivity. In the preferred embodiment, cobalt is used to dope the layers from between .03 %, in the layer furthest from the heat source, to .06 %, in the layer closest to the heat source. The doping may be

alternatively performed using any conventional doping techniques.

At this point, the insulator between the "n"-type and "p"-type elements is deposited, if a solid material (the insulator is not shown in FIG. 11, for the sake of simplicity). As mentioned, a vacuum is used to insulate the "n"-type and "p"-type elements in the preferred embodiment. Alternatively, air, silica, or any other electrical insulator may be used. If a solid material is used, it must be deposited during the element deposition process, preferably after each of the "n"-type and "p"-type elements 11 and 15 have been deposited. Deposition of this insulator may be

performed by an evaporation process or any other

convention material deposition process. It is important to note, however, that the electrical insulator should be of a material that does not readily transmit or lose heat since this may detract from the thermoelectric generation. Then, copper is again deposited on another, different substrate to form the conduction channels 19 for the p/n junctions of the thermoelectric layer just fabricated. This second substrate will provide the second set of conduction channels 19 opposite the first 17, and be later mounted to the fabricated layer by a press and sintering process, to complete the electrical connection, sandwiching the fabricated layer between the two substrates. If additional layers are to be

fabricated, the second substrate 139 is inverted before being pressed and sintered to the fabricated layer, and the layer deposition process described above recommenced for the next subsequent layer, with a different quantity of cobalt doping. It is for this reason that some substrates have two sets of conduction channels 17 and 19 deposited at the beginning of a thermoelectric layer fabrication, as mentioned above. Thus, every

thermoelectric layer 103 is insulated from surrounding layers (and from the heat sink and heat source) by a substrate 139 which is an electrical insulator and thermal conductor and which is deposited for the

conduction channels for both adjacent thermoelectric layers (or one adjacent layer, if the innermost or outermost substrate).

The "n"-type and "p"-type elements 11 and 15 of each layer 103 form a single series electrical

connection within that layer. Since, as seen in FIG. 1, electrons in the "n"-type material 11 flow away along a heat gradient, whereas electrons in the "p"-type

material flow 15 towards a heat gradient, the copper channels 17 and 19 at alternate sides of the layers create a single potential difference across each layer, much like common household battery configurations, which feature series connections between batteries that alternate in their orientation to provide a single voltage that is the sum of the voltages of each of the batteries.

During the deposition process, the masks are also configured to allow the creation of copper channels between adjoining layers (not shown in FIG. 11), such that all ten layers may be connected in parallel to the adjacent layers. Thus, two copper posts, perpendicular to the layering of thermoelectric layers 103, are placed to pass through or around the substrates 139 and contact conduction channels 17 and 19. These posts may be mask-deposited to provide a parallel electrical connection of all thermoelectric layers 103 within each module 95. In addition, a copper conduction channel (not shown) is deposited on the outermost substrate outside an area overlaid by the thermoelectric layers 103 to provide a coupling between opposite sides of the module 95, and thus provide the parallel coupling between each

thermoelectric module 95 within a column 129. Thus, the potential difference of each layer 103 is similarly configured in parallel such that each column 129 of modules 95 provides a single output voltage of high current density. For example, each thermoelectric layer 103 is to generate approximately 1½ V of potential difference at approximately 200 mA, providing 2 amps per module. Thus, since the thermoelectric generators 47 and 49 include approximately 37 columns and 8 rows of modules, each thermoelectric generator 47 and 49 will produce 1½ V of potential difference with a current supply of 592 amps.

In alternative applications to the

thermoelectric vehicle 27 described herein, if the modules 95 are to have internal electrical series connection between layers, then each module 95 can produce 15 V at approximately 200 mA of current supply. Metallized leads may be soldered to the chip's exterior for ready electrical coupling to a circuit remote to the heat source.

B. The Heat Battery

The heat battery 93 includes a graphite cylinder having a centralized bore 111 that is 10 to 15 % of the cylinder's diameter. In the preferred embodiment, a block of graphite composition twelve inches high with a circumference of eight inches and a 1½ inch diameter bore will be used. This battery 95 can thus

accommodate thirty-seven columns 129 of thermoelectric modules 95 along the cylinder's outer periphery and eight rows 131 of thermoelectric modules along the height of the cylinder. Notably, it has been found that there is decreasing economies of scale with the

thermoelectric generators 47 and 49, and in particular, with the manufacture of the graphite heat battery 93. It is for this reason that the preferred embodiment uses two thermoelectric generators 47 and 49 of the type described, rather than a single larger generator.

Since the graphite 141 is an electrical conductor, it is not very appropriate to place the graphite directly in contact with the thermoelectric modules. Rather, the graphite is encased along its circular periphery in a material 143, such as silica, that serves as an electrical insulator and a thermal conductor. In the case of the preferred embodiment, a ¼ to ½-inch thick layer of silica is used to surround the graphite 141 and insulate the thermoelectric modules from the graphite. However, the silica 143 also serves an equally important function of increasing the latent heat of the graphite heat battery. In order for the vehicle's range to be maximized for a charged heat battery 93 , it is necessary that the heat battery be capable of retaining heat as long as possible. Thus, the heat battery 93 must have a high latent heat, or ability to remain hot after heat is no longer applied to the heat entry region of the heat battery, which is within the bore 111 of the cylinder. It is expected that encasing the graphite 141 in the additional

material 143 will improve the vehicle's range from over 400 miles to over 600 miles in absence of light or electrical input to charge the heat battery 93.

The heat battery 93 must be a device capable of storing heat preferably for as great a length of time as possible. In the example discussed, the graphite core 141 is expected to retain heat of approximately 2000° F for approximately 4 hours. The center of the graphite core is fitted with the glass fiber insert 109, which fits snugly into the bore 111 and provides termination for the glass fibers of fiber groups 85 and 87,

discussed above. Alternatively, the central insert 109 could include any means of imparting heat to the heat battery 93 such as for example, a radioisotope heat source. This is exemplified by the use of spiral tungsten elements 108 contained within the graphite core 141 immediately adjacent to the bore 111. This heating element imparts heat to the heat battery 93 during regenerative braking and also when the external power inputs 115 and 117 are connected with power couplings to charge the heat battery. The tungsten element 108 features two electrical connections, designated as V+_IN and V_IN in FIG. 9, which are coupled to the power control circuit 107. This allows the coupling of either AC voltage from the external power inputs, amplified as necessary (an AC charging circuit is a commercially available standard element in electric vehicles, and 120 VAC or 220 VAC may be used depending upon the charging circuit selected), or DC voltage from the regenerative braking system 105. Much as with the filament in many light bulbs, the tungsten heats substantially when large currents flow through it. One end of the heat battery 93 mounts the V_IN terminal 145 for providing a low resistance flow path for the voltage supplied by the power control circuit 107. Thus, the tungsten elements bear large currents, transferring generated heat through the tungsten's abutting contact with the graphite 141 to the heat battery 93.

The glass fiber bundles 85 and 87 from the solar energy distribution center 81 enter the heat battery 93 of each thermoelectric generator 47 and 49 within the centralized insert 109. FIG. 9 shows only a few fiber bundles for illustration of their even distribution within the bore 111. However, its is expected that many dozens of bundles will be used, having a right angle bend within the insert and termination perpendicular to the axial bore of the heat battery such, that the concentrated solar energy is radiated upon the graphite 141, heating the heat battery 93. Importantly, the centralized insert 109 must not be a source of heat loss, and is preferably insulated at each end of the insert. A contemplated alternative embodiment to the thermoelectric generator of the present invention is a radioisotope thermoelectric generator, which generates heat based upon the radioactive decay of an isotope fuel. The central insert would contain a radioisotope, preferably Strontium⁹⁰ or Cesium¹³⁷, which would be replaced after approximately one half-life, or

approximately each 30 years in the cases of Strontium⁹⁰ and Cesium¹³⁷, respectively. The radioisotope heat source could be implemented either in addition to, or in lieu of, the solar energy collection system of the preferred embodiment. It is stressed that the

principles of the present invention may be applied to any heat source, not just the solar energy and

radioisotope heat sources discussed herein.

At each end of the heat battery are heat insulation layers, 147 and 149, that minimizes heat loss through paths not encompassing the thermoelectric modules. These layers are preferably made of a material known as "MIN-K," which is available from the Manville Company of Elkhart, Indiana.

Adjoining the circular periphery of the insulation layers 147 and 149 are the upper and lower bus bars, 132 and 133. These are discontinuous copper rings which carry the electrical power for groups of columns 129 of thermoelectric modules 95. In particular, each pair of contacts for a given column 129 connect to a magnetic reed switch 151 of the magnetic relay system 119. Since the DC wheel motors 53 and 55 are current driven, as the operator depresses the accelerator pedal, and increasing number of magnetic reed switches 151 are engaged, each coupling

approximately 3 columns 129 of thermoelectric modules to the wheel motors 53 and 55. The greater the number of columns 129 so connected, the faster the vehicle moves.

C. Operation Of The Vehicle

The vehicle's generation of heat and operation will now be described. The solar collectors 29, 31 and 33 charge the heat battery during daylight hours. If desired, the vehicle is coupled to an external power supply, such as a convention 120 VAC output, causing the heating element 108 within each thermoelectric generator 47 and 49 to rapidly heat the heat battery 93.

An operator turns the ignition 123 "on" and depresses the accelerator pedal 121 which engages some of the magnetic reed switches 151, shown schematically in simplified form in FIG. 7. Although FIG. 7 shows only six magnetic reed switches 151 associated with the accelerator pedal 121, there are in fact advantageously approximately two dozen such switches, each a singlepull, double-throw switch having mercury contacts about %-inches in diameter for handling 200-300 amps of power during the coupling of groups of columns 129 to the DC wheel motors. As mentioned, the DC wheel motors are current driven, requiring only a small quantity of voltage taken directly from the thermoelectric

generators 47 and 49. Both the DC wheel motors and the magnetic reed switches are commercially available units and the particular types selected are simply a matter of design choice. Suitable DC wheel motors of the type discussed herein are available pursuant to specification manufacture from the BEI Motion Systems Company, Kimco Magnetics Division, of San Marcos, California.

Currently, no specific model of switch or DC motor has been selected as the preferred model or type to be utilized in a commercial thermoelectric vehicle.

Preferably, the DC motors should be operable at the level of voltage output by the thermoelectric

generators, or a DC-to-DC converter implemented to adjust the voltage output of the thermoelectric

generators to the appropriate level .

As the operator depresses the accelerator pedal 121 further, a greater number of magnetic reed switches 151 are engaged, and the vehicle 27 moves faster. Since the thermoelectric modules 95 also generate heat when coupled to a potential difference, modules not connected to a load through the magnetic reed switches 121 serve to insulate the heat battery, preserving the heat energy much as a gasoline tank preserves fuel when the motor is not in use.

When the operator decides to brake, he depresses the brake 113 which manually raises the accelerator pedal 121 and also electrically couples the chemical storage battery 57 to the regenerative braking system, which charges the chemical storage battery at twelve volts. A second set of magnetic reed switches 153 performs this coupling.

When the operator decides to put the vehicle in reverse, he simply manipulates the forward/reverse control 124 to change the polarity of the power supplied to the DC wheel motors 53 and 55.

What has been described herein is a particular embodiment for the inventions defined by the appended

36 claims. Numerous modifications of this particular embodiment will occur to those skilled in the art without falling outside the inventive principles listed in the claims.

For example, the thermoelectric vehicle of the current invention may be any type of vessel, car, motorcycle or nearly any other apparatus or machinery that can make use of thermoelectric power. Similarly, other types of thermoelectric structures having multiple layers may be feasible without falling outside of the principles of the invention, and may be applied to temperature generation as well as electrical generation. Having thus described several exemplary embodiments of the invention, it will be apparent that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements, though not expressly described above, are nonetheless intended and implied to be within the spirit and scope of the

invention. Accordingly, the foregoing discussion is intended to be illustrative only; the invention is limited and defined only by the following claims and equivalents thereto.

Claims

1. A thermoelectric device, comprising: a first thermoelectric layer; a second thermoelectric layer disposed adjacent to said first thermoelectric layer in opposed substantially parallel spatial relationship to said first thermoelectric layer; and, wherein said first and second thermoelectric layers are adapted for generation of electrical energy at a temperature differential across the layer, each of said thermoelectric layers having a different temperature range, said first and second thermoelectric layers generating one of electrical energy in response to the temperature differential, and of the temperature

differential in response to supplied electrical energy.

2. A thermoelectric device as in claim 1, wherein each thermoelectric layer is made of material composition which optimizes the thermoelectric

generation of the layer within that temperature range.

3. A thermoelectric device as in claim 1, further comprising an electrical insulator layer

disposed adjacent to and between said first and second thermoelectric layers, in substantially parallel spatial relationship thereto.

4. A thermoelectric device as in claim 1, wherein said first and second thermoelectric layers are electrically coupled in series.

5. A thermoelectric device as in claim 1, wherein said first and second thermoelectric layers are electrically coupled in parallel.

6. A thermoelectric device as in claim 1, wherein each of said first and second thermoelectric layers includes a plurality of alternating "n"-type and "p"-type semiconductor elements that are electrically coupled in series to produce at least one of a potential difference in accordance with the Seebeck principle when a temperature gradient is applied across said layers, and of a heat gradient in accordance with the Peltier principle when a potential difference is applied across the series electrical coupling of said thermoelectric layers.

7. A thermoelectric device as in claim 6, wherein: said "n"-type semiconductor element includes gallium arsenide; and said "p"-type semiconductor element includes bismuth telluride.

8. A thermoelectric device as in claim 1, wherein the material composition of each of said first and said second thermoelectric layers includes the same base materials with different amounts of a second, doped material.

9. A thermoelectric device as in claims 8, wherein said second, doped material includes cobalt.

10. A thermoelectric device as in claims 8, wherein said base materials include bismuth telluride.

11. A thermoelectric device as in claims 8, wherein said base materials include gallium arsenide.

12. A thermoelectric device, comprising: a plurality of thermoelectric layers arranged in substantially parallel opposing spatial relationship, each of said thermoelectric layers including

(a) at least one first element and one second element, arranged adjacent to one

another, in substantially parallel spatial relationship perpendicular to the arrangement of said thermoelectric layers,

(i) said first element including a

first material which is

characterized by negative

electrical charge flowing toward a heat source when a temperature difference is applied across a length of said first element,

(ii) said second element includes a

second material which is

characterized by negative

electrical charge flowing away from a heat source when a temperature difference is applied across a length of said second element,

(iii) said first element and said second element being electrically coupled at one end of their parallel relationship, so as to form a series electrical connection;

(b) first electrical insulator separating

each of said thermoelectric layers, said electrical insulator also constituting a thermal conductor; and (c) an electrical contact, electrically

coupled to said plurality of thermoelectric layers, and being adapted for at least one of applying a potential to said thermoelectric layers for

creating a temperature difference across said plurality of thermoelectric layers, and driving an electrical load from potential difference generated by said plurality of thermoelectric layers when a temperature difference is applied across said plurality of thermoelectric layers.

13. A thermoelectric device as in claim 12, further including elemental insulation means for

electrically insulating said semiconductor elements from adjoining elements and permitting series electrical conduction only at electrical couplings at one end of the parallel relationship between adjoining elements.

14. A thermoelectric device as in claim 12, wherein said plurality of thermoelectric layers includes thermoelectric layers that are fabricated of materials that impart differing electrical resistivity to said layers.

15. A thermoelectric device as in claim 12, wherein each of said plurality of thermoelectric layers includes thermoelectric layers that are fabricated of materials characterized by different thermal

conductivity.

16. A thermoelectric device as in claim 12, wherein said plurality of thermoelectric layers includes thermoelectric layers that are fabricated of materials characterized by different figures of merit.

17. A thermoelectric device as in claim 16, wherein each of said thermoelectric layers are

characterized by a different figure of merit.

18. A thermoelectric device as in claim 17, wherein each of said thermoelectric layers is

characterized by a figure of merit that is selected to provide an optimal efficiency of conversion (between electric charge and temperature gradient across a thermoelectric layer) for selected different temperature ranges that are to occur across each of said

thermoelectric layers.

19. A thermoelectric device as in claim 12, wherein said plurality of thermoelectric layers includes thermoelectric layers that are fabricated of a material doped to produce a selected figure of merit.

20. A thermoelectric device as in claims 19, wherein said plurality of thermoelectric layers includes thermoelectric layers that are doped with cobalt.

21. A thermoelectric device as in claims 19, wherein said material doped to produce a selected figure of merit includes bismuth telluride.

22. A thermoelectric device as in claim 12, wherein said electrical contact further includes means for electrically coupling each of said thermoelectric layers in series.

23. A thermoelectric device as in claim 12, wherein said electrical contact further includes means for electrically coupling each of said thermoelectric layers in parallel.

24. A thermoelectric device as in claim 12, wherein said first material is "p" type material, and wherein said second material is "n" type material.

25. A thermoelectric device as in claim 24, wherein said first material includes bismuth telluride and said second material includes gallium arsenide.

26. A thermoelectric device as in claim 12, wherein said plurality of thermoelectric layers are each configured to generate electricity according to the Seebeck principle when a temperature gradient is applied across a junction of said first and second elements.

27. A thermoelectric device as in claim 12, wherein said plurality of thermoelectric layers are each configured to generate heat pursuant to the Peltier principle when current is passed through the series electrical connection of each layer.

28. A thermoelectric device, comprising: first thermoelectric conversion means for converting one of voltage to temperature difference across said first thermoelectric conversion means and a temperature difference across said first thermoelectric conversion means to voltage; second thermoelectric conversion means for converting one of voltage to a temperature difference across said second thermoelectric conversion means and a temperature difference across said second thermoelectric conversion means to voltage; and, wherein said first thermoelectric conversion means and said second thermoelectric conversion means are arranged in series thermally.

29. A thermoelectric device as in claim 28, further comprising coupling means for coupling said first thermoelectric conversion means and said second thermoelectric conversion means in series electrically.

30. A thermoelectric device as in claim 28, further comprising coupling means for coupling said first thermoelectric conversion means and said second thermoelectric conversion means in parallel

electrically.

31. A thermoelectric device as in claim 28, wherein: said first thermoelectric conversion means includes a first semiconductor-based layer that is characterized by a first figure of merit; said second thermoelectric conversion means includes a second semiconductor-based layer that is characterized by a second figure of merit, different from the first figure of merit.

32. A thermoelectric device as in claim 28, wherein at least one of said thermoelectric conversion means includes a series electrical connection including a plurality of alternating "n"-type and "p"-type

semiconductor elements arranged substantially in

parallel along a direction of heat propagation, said semiconductor elements being fabricated such that negative electric charge in said "n"-type semiconductor elements flows towards relative heat and the opposite direction in the "p"-type semiconductor elements.

33. A thermoelectric device as in claim 28, wherein: said first thermoelectric conversion means includes two electrical insulation layers having disposed therebetween said first semiconductor- based layer; said second thermoelectric conversion means includes two electrical insulation layers having disposed therebetween said second semiconductor- based layer; and wherein said electrical insulation layers are also thermal conductors.

34. A method of fabricating a thermoelectric device, comprising the steps of: fabricating a first thermoelectric material layer with a first material which optimizes the layer for generation of electrical energy at a first selected temperature range; and fabricating a second thermoelectric material layer with a second material which optimizes the layer for generation of electrical energy at a second selected temperature range different from the first, and positioning said second thermoelectric material layer in opposed

substantially parallel spatial relationship to said first thermoelectric material layer, in a manner such that the first and second

thermoelectric material layers are adapted to cascade differential heat across the

thermoelectric device.

35. A method of fabricating a thermoelectric device as in claim 34, wherein: the step of fabricating the first layer further includes the step of fabricating the first material layer with a first material

characterized by a first figure of merit; and the step of fabricating and positioning the second layer further includes the step of fabricating the second material layer with a second material characterized by a second figure of merit different from the first.

36. A method of fabricating a thermoelectric device as in claim 35, wherein each of the steps of fabricating the first layer and fabricating the second layer includes the step of depositing a substrate with a thermoelectric material layer having an alternating arrangement of first and second elements, the first elements having a first material wherein negative electrical charge flows towards a heat source when a temperature difference is applied across the first element, the second element having a second material wherein negative electrical charge flows away from a heat source when a temperature difference is applied across a length of said second element.

37. A method of fabricating a thermoelectric device as in claim 36, wherein the steps of depositing the substrates include depositing each substrate with the same base materials and doping the base materials overlying each substrate with a doping material to thereby differentiate the figure of merit of the first and second layers.

38. A method of fabricating a thermoelectric device as in claim 37, wherein the step of doping the base material includes the step of ion bombarding the base material with a metal.

39. A method of fabricating a thermoelectric device as in claim 36, wherein each of the steps of fabricating the first layer and fabricating the second layer includes depositing at least two layers of conductors for electrically coupling the elements, one layer of conductors deposited before the steps of depositing the substrates and one layer of conductors deposited after the steps of depositing the substrate, to electrically couple the first and second elements in series.

40. A method of fabricating a thermoelectric device as in claim 39, wherein the steps of depositing the substrates with a thermoelectric material having an alternating arrangement of first and second elements includes the step of creating an insulator between each of the alternating first and second elements such that the first and second elements are electrically coupled in series only by the two layers of conductors.

41. A method of fabricating a thermoelectric device as in claim 35, wherein the step of fabricating and positioning the second layer includes bonding the first layer to the second layer after their respective fabrication by a sintering technique.

42. A method of fabricating a thermoelectric device as in claim 34, wherein the step of fabricating and positioning the second layer includes the steps of depositing a substrate material upon the first material and depositing the second material upon the substrate.

43. A method of fabricating a thermoelectric device as in claim 34, further comprising the step of electrically coupling the first and second layers in parallel electrically.

44. A method of fabricating a thermoelectric device as in claim 34, further comprising the step of electrically coupling the first and second layers in series electrically.

45. A thermoelectric generator, comprising: a heat source; a heat sink; and at least two thermoelectric layers disposed in substantially parallel, opposed spatial relationship between the heat source and the heat sink, each thermoelectric layer being adapted to generate electric power from a heat gradient across the layer, each thermoelectric layer operating over different temperature ranges such that a heat difference across the thermoelectric device between the heat sink and the heat source is cascaded across the layers to generate electric power.

46. A thermoelectric generator as in claim 45, wherein the heat source includes a heat battery.

47. A thermoelectric generator as in claim 45, wherein said heat source includes a solar heat source.

48. A thermoelectric generator as in claim

47, wherein said heat source includes: a light collector; a light converter that converts light to heat; and guide means for guiding collected light from said light collector to said light converter.

49. A thermoelectric generator as in claim

48, wherein said guide means includes at least one fiber optic cable coupling the light collector and the light converter.

50. A thermoelectric generator as in claim 48, further comprising focussing means for converging light collected by the light collector to said guide means, wherein said guide means includes a light entry point having a cross-sectional area smaller than a surface area associated with said light collector.

51. A thermoelectric generator as in claim 48, wherein said light converter includes a graphite material, positioned at a terminal of each fiber optic cable so that light is irradiated on said graphite material.

52. A thermoelectric generator as in claim 51 wherein said light converter includes means for

increasing the latent heat of said graphite material.

53. A thermoelectric generator as in claim 51, wherein said light converter includes a graphite

cylinder having a bore that receives each

terminal, said thermoelectric layers coupled to an outer surface of said graphite cylinder.

54. A thermoelectric generator as in claim 45, wherein said heat source includes an aircraft engine and wherein the atmosphere exterior to the aircraft forms the heat sink.

55. A thermoelectric generator as in claim 45, wherein said heat source includes a radioisotope heat generator.

56. A thermoelectric generator adapted to provide a relative temperature when supplied with electrical power, comprising: a first thermoelectric layer including at least one hot semiconductor junction and at least one cold semiconductor junction forming a series electrical connection, adapted to generate a first temperature differential between said hot and cold junctions according to the Peltier effect when said series electrical connection is coupled to a potential difference; a second thermoelectric layer including at least one hot semiconductor junction and at least one cold semiconductor junction forming a series electrical connection, adapted to generate a second temperature differential between said hot and cold junctions according to the Peltier effect when said series electrical connection is coupled to a potential difference; and wherein said first and second thermoelectric layers are disposed thermally in series such that the relative temperature differential generated by said thermoelectric device is substantially the sum of said first and second temperature differentials.

57. A thermoelectric generator as in claim 56, wherein said first and second thermoelectric layers are electrically coupled in series.

58. A thermoelectric generator as in claim 56, wherein said first and second thermoelectric layers are electrically coupled in parallel.

59. A thermoelectric device as in claim 56, wherein each thermoelectric layer is made of material composition which optimizes the layer thermoelectric generation for generation of a temperature differential at a selected temperature.

60. A thermoelectric device as in claim 56, wherein each of said first and second thermoelectric layers includes a plurality of alternating "n"-type and "p"-type semiconductor elements that form said junctions and are electrically coupled in series.

61. A thermoelectric generator, comprising: a plurality of thermoelectric modules, each module having at least two thermoelectric layers disposed in substantially parallel, opposed spatial relationship between the heat source and the heat sink, each thermoelectric layer adapted to generate electric power from a heat gradient across the layer, each thermoelectric layer operating over different temperature ranges such that a heat difference across each said module is cascaded across the layers to generate electric power; a heat battery having a heat entry region and a heat dissipation region, said plurality of thermoelectric modules mounted adjacent to said heat dissipation region; means for providing heat to said heat entry region; and, a heat sink mounted adjacent to said plurality of thermoelectric modules opposite said heat battery, such that said heat battery and said heat sink are arranged to provide a temperature differential across said plurality of

thermoelectric modules.

62. A thermoelectric generator as in claim

61, wherein each of said thermoelectric layers includes a plurality of alternating "n"-type and "p"-type

semiconductor elements that are electrically coupled in series, said elements adapted to produce at least one of a potential difference in accordance with the Seebeck principle when a temperature gradient is applied across said layers, and of a heat gradient in accordance with the Peltier principle when a potential difference is applied across said thermoelectric layers.

63. A thermoelectric generator as in claim

62, wherein said "n"-type semiconductor element includes gallium arsenide and wherein said "p"-type semiconductor element includes bismuth telluride.

64. A thermoelectric generator as in claim 62, wherein each of said first and said second

thermoelectric layers is produced of the same base materials with different amounts of a second, doped material.

65. A thermoelectric generator as in claims 64, wherein said second, doped material includes cobalt.

66. A thermoelectric generator as in claim 61, wherein each of said plurality of thermoelectric modules are electrically coupled in parallel.

67. A thermoelectric generator as in claim 61, wherein each of said thermoelectric layers within each module are electrically coupled in series, such that each thermoelectric module forms a single series electrical configuration.

68. A thermoelectric generator as in claim 61, wherein each of the plurality of thermoelectric modules also includes an electrical insulator separating each of the thermoelectric layers.

69. A thermoelectric generator as in claim 61, wherein said means of applying heat to said heat entry region includes: a solar collector; means for concentrating light collected by said solar collector; and means for carrying light collected by said solar collector to said heat entry region.

70. A thermoelectric generator as in claim 61, wherein said heat battery is substantially

cylindrical having a central bore, said heat entry region located within said central bore, said plurality of thermoelectric modules mounted adjacent to the outer circumferential surface of said heat battery.

71. A thermoelectric generator as in claim

70, wherein said cylindrical heat battery includes a graphite material and an exterior layer of a material that increases the latent heat of the graphite.

72. A thermoelectric generator as in claim

71, wherein said material that increases the latent heat is silica-based.

73. A thermoelectric generator as in claim 70, wherein said cylindrical heat battery includes an insulation layer at each cylindrical end of said heat battery.

74. A thermoelectric generator as in claim 73, wherein said insulation layer at each cylindrical end includes "MIN-K."

75. A method of generating electric power, comprising the steps of: collecting solar radiation impingent upon a first surface area and focussing the radiation to a smaller surface area; converting the focussed solar radiation to heat; and generating electricity from a heat gradient according to the Seebeck principle.

76. A method of generating electric power as in claim 75, wherein the step of generating also

includes the steps of providing a thermal gradient across a plurality of thermoelectric layers, each layer connected thermally in series and optimized for

generation of electricity from a specific temperature gradient.

77. A system for moving a vehicle

substantially through applications of electrical power, comprising: a first thermoelectric generator which is mounted to the vehicle and is adapted to generate substantially all of the electrical power for moving the vehicle; propelling assembly means associated with the vehicle and with the thermoelectric generator, for propelling the vehicle in response to electrical power supplied by the thermoelectric generator, the propelling assembly means including a motor which is coupled to the vehicle and to the thermoelectric generator and thereby causes the movement of the vehicle; a heat supply, associated with the

thermoelectric generator, for supplying a first temperature to the thermoelectric generator; and wherein the thermoelectric generator generates the electric power from a temperature

differential between the first temperature supplied by said heat supply means and a

reference temperature.

78. A system as in claim 77, wherein said propelling assembly means further includes first and second wheels which are associated with the motor.

79. A system as in claim 78, wherein said heat supply includes at least one regenerative braking system, said regenerative braking system being coupled to at least one tire to generate electrical power from the rotation thereof.

80. A system as in claim 77, wherein said thermoelectric generator includes at least one

thermoelectric module having a plurality of

thermoelectric generation layers that each generate a potential difference when a heat gradient is applied across said layers, each layer coupled in series

thermally such that said heat gradient is cascaded across each of said plurality of thermoelectric

generation layers.

81. A system as in claim 80, wherein each of said plurality of thermoelectric generation layers is optimized to generate electricity within a corresponding temperature range cascaded across the layer.

82. A system as in claim 77, wherein said thermoelectric generator includes two thermoelectric generators, each generator having a heat battery, a plurality of thermoelectric modules surrounding said heat battery, and a heat sink overlying said

thermoelectric modules in a manner to form a temperature gradient across said thermoelectric modules when said heat battery is charged with heat.

83. A system as in claim 77, wherein said heat supply includes at least one regenerative braking system, said regenerative braking system electrically coupled to a heating element adjacent to said heat battery, said heating element provided electrical power and therefrom heating the heat battery.

84. A system as in claim 77, wherein said heat supply includes a radioisotope heat source thermally coupled to said thermoelectric generator.

85. A system as in claim 77, wherein said heat supply includes solar energy collector means for collecting solar energy irradiated upon a surface area and conversion means for transmitting solar energy to said thermoelectric generator and for converting said solar energy to heat for thermoelectric generation.

86. An electrically powered vehicle as in claim 85, wherein: said solar energy collector means includes focussing means for focussing collected solar energy to a solar energy collection point; and, said conversion means includes solar energy conveyance means for collecting the focussed solar energy and coupling said collected solar energy to said thermoelectric generator.

87. A system as in claim 85, wherein: the system further includes a second

thermoelectric generator, each generator having a heat battery, a plurality of thermoelectric modules surrounding said heat battery, and a heat sink overlying said thermoelectric modules in a manner to form a temperature gradient across said thermoelectric modules when said heat battery is charged with heat; and, said conversion means includes a solar energy distribution center which couples solar energy to each of said heat batteries.

88. A system as in claim 87, wherein said conversion means includes: fiber optic means for conveying light between said solar energy collector means and said solar energy distribution center; glass optical couplings between said solar energy distribution center and said heat batteries, said glass optical couplings adapted to irradiate said heat batteries with solar energy to thereby heat said heat batteries; and, concentrating means for concentrating solar energy irradiated upon said surface area such that said glass optical couplings transmit substantially all of collected solar energy to said heat batteries.

89. A system as in claim 88, wherein said solar energy collector means includes at least two solar energy collectors.

90. A system as in claim 89, wherein at least one of said solar energy collectors is mounted on a roof of said vehicle.

91. A system as in claim 77, wherein said heat supply includes a heat battery having a heat entry region and a heat dissipation region, said

thermoelectric generator is positioned as said heat dissipation region and a heat sink and provides said reference temperature, said heat sink positioned to generate a temperature gradient between said heat battery and said heat sink across said thermoelectric generator.

92. A system as in claim 91, wherein said heat battery includes a cylinder composed substantially of graphite, said heat entry region includes an axial bore within said cylinder, said heat dissipation region includes the curved surface of said cylinder, said heat battery further having insulation means for insulating at least the ends of the cylinder.

93. A system as in claim 92, wherein said heat supply means further includes a heating element mounted adjacent to said heat entry region, said heating element composed of a material that heats when carrying electrical power, said heating element selectively coupled to a power supply to thereby heat said heat battery.

94. A system as in claim 92, wherein said insulation means includes "MIN-K."

95. A system as in claim 91, wherein said heat battery includes an external layer of a material that increases the latent heat of the heat battery.

96. An electrically powered vehicle as in claim 95, wherein said external layer includes a silica-based material.

97. An electrically powered vehicle, comprising: a vehicle ; a solar energy collector; a heat battery; means for irradiating said heat battery with the solar energy collected by said solar energy collector; a plurality of thermoelectric modules overlying a heat emitting region of the heat battery; a heat sink overlying said plurality of thermoelectric modules to sandwich said plurality of thermoelectric modules between said heat battery and said heat sink; at least one wheel motor; power distribution means coupling said

thermoelectric modules and each wheel motor.

98. An electrically powered vehicle as in claim 97, wherein said means for irradiating said heat battery with the solar energy includes optic coupling means for coupling light from said solar energy

collector to said heat battery.

99. An electrically powered vehicle as in claim 97, wherein each of the thermoelectric modules includes a first thermoelectric layer a second

thermoelectric layer disposed adjacent to said first thermoelectric layer in opposed parallel relationship to said first thermoelectric layer and wherein said first and second thermoelectric layers are made of material composition which optimizes the layer for generation of electrical energy at the temperature differential across the layer, each of said thermoelectric layers having a different temperature range.

100. An electrically powered vehicle as in claim 97, wherein said power distribution means includes a power regulator for regulating power generated by the thermoelectric generator to each wheel motor and to an electric power battery.

101. An electrically powered vehicle as in claim 97, further comprising a regenerative braking system coupled to said power distribution means to generate electric power from the vehicle's motion, thereby slowing the vehicle.

102. An electrically powered vehicle as in claim 101, wherein the regenerative braking system includes at least one motor generator, said motor generator having an electrical output that is coupled to a heating element adjacent to said heat battery, said heating element adapted to heat said heat battery when supplied with electrical power, such that the electrical output of said motor generator is converted to heat stored by said heat battery.

103. An electrically powered vehicle as in claim 102, wherein said power distribution means

includes an electrical input accessible from the

vehicle's exterior, said electrical input adapted to received electrical power supplied from the vehicle's exterior and to couple said electrical power to a power control circuit, said power control circuit electrically coupling said heating element to electrical power supplied by said electrical input and electrical power supplied by said motor generator to heat said heating element in response to electrical power supplied by either.

104. An electrically powered vehicle as in claim 100, wherein said power distribution means

includes: a power control circuit; an electrical input accessible from the vehicle's exterior, said electrical input adapted to received electrical power supplied from the vehicle's exterior and to couple said electrical power to said power control circuit; a heating element coupled to said power control circuit and mounted adjacent to said heat battery, said heating element adapted to heat said heat battery when supplied with electrical power; and wherein said power control circuit regulates externally supplied electrical power supplied to said heating element to heat said heat battery.

105. A method of propelling a vehicle, comprising the steps of: collecting solar radiation impingent upon a first surface area external to the vehicle and focussing the radiation to a smaller surface area; conveying the focussed radiation by an optical conveyance device to at least one thermoelectric generator internal to the vehicle; converting the focussed solar radiation to heat; generating electricity from a heat gradient according to the Seebeck principle; and, driving an electric motor with the generated electricity to provide substantially all of the impetus to propel the vehicle.

106. A method of propelling a vehicle as in claim 105, wherein the step of converting also includes the steps of conveying the focussed solar radiation to a heat battery and providing heat to the heat battery by irradiating the heat battery with the focussed solar radiation.

107. A method of propelling a vehicle as in claim 105, wherein the step of generating also includes the steps of providing a thermal gradient across a plurality of thermoelectric layers, each layer connected thermally in series and optimized for generation of electricity from a specific temperature gradient.

108. A method of propelling a vehicle as in claim 105, wherein the step of conveying includes a step of distributing focussed solar radiation to at least two thermoelectric generators, and conveying the distributed focussed solar radiation to heat batteries of each thermoelectric generator by an optical conveyance device.

109. A method of propelling a vehicle as in claim 105, further comprising the step of distributing the generated electric power to the electric motor, to at least one chemical storage battery resident in the vehicle, and to peripheral electronics.

110. A method of propelling a vehicle as in claim 105, further comprising the step of generating electricity with a regenerative braking system.

111. A method of propelling a vehicle as in claim 110, further comprising the step of electrically driving a heating element with electricity generated by the regenerative braking system, the heating element heating the heat battery when supplied with electrical power.

112. A method of propelling a vehicle as in claim 105, further comprising the step of electrically driving a heating element by coupling a power input to a power source external to the vehicle to thereby heat the heat battery.