US3299299A

US3299299A - Apparatus for generating electrical energy by the application of heat

Info

Publication number: US3299299A
Application number: US483013A
Authority: US
Inventors: Theodore M Dickinson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-07-19
Filing date: 1965-08-18
Publication date: 1967-01-17
Anticipated expiration: 1984-01-17
Also published as: FR1329278A

Description

' Jan; 1967 T M. DICKINSON 3,299,299

APPARATUS FOR GENERATING ELECTRICAL ENERGY BY THE APPLICATION OF HEAT Original Filed July 19, L961 2 Sheets-Sheet 1 CUEEI/W' by w d fill v 1975 Attorney Jan. 17, 1967 T. M. DICKINSQN 3,299,299

. APPARATUS FOR GENERATING ELECTRICAL ENERGY BY THE APPLICATION OF HEAT Original Filed July 19, 1961 2 Sheets-Sheet 2 (by 2} 4 W /7 /.'5 Axrorney United States Patent 3,299,299 APPARATUS FOR GENERATING ELECTRICAL ENERGY BY THE APPLICATION OF HEAT Theodorer M. Dickinson, Schenectady, N.Y., assignor to I General Electric Company, a corporation of New York Continuation of application Ser. No. 125,196, July 19,

y 1961. This application Aug. 18, 1965, Ser. No. 483,013

13 Claims. (Cl. 310- 4) improved method and an apparatus for converting thermal heat or other forms of energy directly into electrical energy without the use of a rotating machinery.

This application is a continuation of copending application, now abandoned, Serial No. 125,196, filed July 19, 1961, and assigned to the same assignee as the present invention.

If a: conductive probe is inserted in an ionized plasma, itwill be bombarded with both positive ions and electrons. Ina normal plasma, the number densities of the electrons and positive ions are equal. The electrons are eitherat the same temperature as the ions or at a higher temperature, Because of their lighter mass, the velocities of the electrons are higher and the number of electrons striking the probe per unit time exceeds the number of, positive ions striking the probe. If an electrical circuit to the probe is completed, a net negative current willflow. If the probe is left open circuited, it will charge up to a negative potential relative to the plasma such that the resulting, electrostatic force on the electrons repels all but the most energetic electrons, reducing the flow of electrons to. a value exactly equal to that of the positive ions, and resulting in a net current equal to zero; The magnitude of the negative potential so pro duced depends on the temperature of the electrons; the

higher. their temperature, the higher the negative potential; The negative potential may be expressed by the equation where T and T are the electron and ion temperatures in degrees Kelvin and, m and m their respective masses. Ifa second probe is inserted in the plasma at a point where the electron temperature is different from that at thefirst probe, the second probe will charge up to a different 1 potential and a potential difierence will exist be- I tween the two probes. If a load is connected between the two probes, current will flow therethrough and electrical. power may be extracted from the plasma. The energy which is supplied to the plasma to maintain it in an ionized state is thus converted directly to electrical energy, with the plasma acting as the coupling medium.

Heretofore, the potential difference between the two electrodes hasbeen achieved by utilizing electrodes of different shapes or, of different materials or operating at diiferent temperatures; or by other methods, such as the use of magnetic fields or electron attachment to theneutral gas atoms to reduce the electron flow to one electrode relative to the other. For the embodiment of the present invention, it is only necessary that the electron temperature be higher at one electrode than at the other. Therefore, a principal object of the present invention is to provide an improved energy converter for converting heat or other forms of energy directly into electrical energy.

3,299,299 Patented Jan. 17, 1967 A further object of the present invention is to provide both an improved method and. apparatus for utilizing the differential rates of diffusion of charged particles of an ionized medium to achieve a source of electrical power.

Briefly, in one form of the present invention, energy in a first form such as heat, nuclear radiation, or electromagnetic energy is converted directly into energy of a second form, i.e., electrical energy. This is accomplished by producing a gradient in the temperature of the electrons in an ionized plasma without regard to the material, shape or any other characteristic of the electrodes immersed in the ionized plasma.

FIGURE 1 is a schematic diagram of an energy converter containing an ionized plasma;

FIGURE 2 is a graph showing the electrical characteristics for the electrodes of the energy converter shown by FIGURE 1;

FIGURE 3 shows an embodiment of the energy converter shown in FIGURE 1;

FIGURES 4a and 4b illustrate modifications of the converter shown in FIGURE 3;

FIGURE 5 shows a plurality of the energy converters of FIGURE 3 arranged to form a typical system; and

FIGURE 6 illustrates an alternate embodiment of the present invention.

The operation of one embodiment of the present invention may best be understood by reference to FIGURE 1 of the drawings which illustrates schematically a chamher 1 containing an ionized plasma 2. Ionization of the plasma is maintained by some means such as an external source of energy in the form of ionizing radiation 3. It would also be possible to apply a nuclear energy source or source of another type internally. Immersed in the ionized plasma are two electrodes 4 and 5 which float at diiferent potentials. As no special design requirement exists for these electrodes, they may be of tungsten or any other material having similar thermal and electrical conductivity properties. If a circuit is connected between the two electrodes 4 and 5, current flows when in accordance with the invention there is created a gradient in the temperature of the electrons of the plasma between the electrodes. It is only necessary that the temperature of the electrons be greater near one electrode than the other. In FIGURE 1, it can be seen that electrode 4 is in the region of higher electron temperature due to the fact that the ionizing radiation is directed toward the plasma in that area adjacent to the electrode 4. Since the radiation is concentrated in the plasma nearer electrode 4, the electron current fiow from the plasma to that electrode will exceed that from the plasmato electrode 5 and a net flow of electrons externally from electrode 4 to electrode 5 will result. Thus, the gradient in temperature of the electrons existing in the plasma between the electrodes produces a flow of current.

FIGURE 2 is a graph of the characteristics of the electrodes 4 and 5. Since the temperature of the electrons in the region of electrode 4 is higher than that at electrode 5, its floating potential (A of electrode 4 is more negative than that of electrode 5 shown as (B A high impedance voltmeter connected between the electrodes reads this potential difference. If the electrodes are connected together through a low impedance ammeter, the potential of electrode 4 will become less negative and that of electrode 5 more negative, until equal currents are attained. The new potential of the two electrodes is indicated by the vertical dashed line connecting points of equalcurrents on the two curves (A and (B If a resistive load 6, in FIGURE 1, is connected between the two electrodes 4 and 5, and a line is drawn on the plot having a negative slope equal to twice the value of the resistance and intersecting the two curve points at equal 3 currents as at (AL) and (BL) then the voltage across the load will be shown as E and the current I Therefore, the powerproduced is E I Thus efiectively there has been a conversion of nuclear energy or electromagnetic energy into electrical power.

In FIGURE 3 is shown one embodiment of the energy converter diagrammatically shown by FIGURE 1. The device may comprise a cell 11 in which an inner cylinder 7 constitutes one electrode and another concentric outer cylinder 8 the other electrode. End walls of the cylindrical structure are provided although not shown in FIGURE 3; and these walls are formed of electrical insulating material. Within the inner cylinder 7 may be placed a fissionable material 9 such as U U or Pu The space between the two cylinders is filled with a gas 10' of low ionization potential, such as cesium at atmospheric or higher pressure, or of another easily ionized gas. Ionization radiation from the fissionable material 9' passes through the thin walls of the inner cylinder 7 to ionize the plasma and heat the electrons near the inner cylinder to a temperature greater than those near the outer cylinder, there-by establishing the temperature gradient required to produce a d'iiference in potential between the inner and outer cylinders. The plasma near the inner electrode 7 may operate at 3,000 K. to produce an appreciable amount of thermal ionization of the vapor. This may be augmented to some extent 'by ionization resulting directly from the high nuclear radiation intensity Within the cell. At the assumed temperature 3,000 K. and at one atmosphere pressure, cesium is thermally ionized to about one part in 140, representing an ion density of l.73 10 ion/cm. These ions diffuse through the gas and are cooled down by collision. If no recombination occurs during their transit to the outer electrode 8, the saturation current density to the outer electrode 8 is approximately amps/om. or 190- amps./cm. of length of the cell shown by FIGURE 3. The temperature gradient in the cesium vapor will produce a no load potential difference of 1.44 volts between the two electrodes 7 and 8 because of the plasma between the electrodes operating at 3,000 K. and approximately 300 K. respectively near the inner 7 and outer 8 electrodes. If an optimum value of load is selected, the maximum output of this one cell is obtained with 184 amps. and 1.23 volts resulting in an output of 226 watts/ cm. of length. Under high temperature conditions, thermal electrons will be emitted (from the solid surfaces of the electrodes. If the work function is low enough and the temperature high enough, this emitted electron current, which is in opposition to the electron current coming from the plasma, will appreciably reduce the output. One method of overcoming this deficiency is by the use of an additional electrode, or plurality of electrodes, positioned in the region of high electron temperature, but cooled by appropriate means to a temperature at which the current due to the thermionic emission of electrons from the electrodes is relatively small with respect to the current due to the flow of electrons from the plasma to the electrodes. Embodiments showing this configuration are shown in FIGURES 4a and 4b. The elements numbered 7 to 11 are the same as shown in FIGURE 3. In FIGURE 4a, the central core 7 containing a fissionable material 9 is surrounded by a grid of water-cooled tubes 12 which serves as the negative electrode. In FIGURE 4b, the water-cooled negative electrode 12 is centrally located at the highest temperature point in the chamber and is surrounded by a cluster of tubes 7 containing fissionable material 9. When these configurations are utilized, the load 6 is connected to the cooled electrode or electrodes 12 and the inner cylinder or cylinders 7, previously connected to the load, and used as electrodes, are now used only as containers in which the means for supplying the heat energy is disposed.

There may be losses in the cells resulting from heat transfer from the plasma near the inner electrodes 7 to the outer electrode 8. This heat transfer may be produced by several means including radiation, conduction by a neutral gas, release of ionization energy, and kinetic energy of ions arriving at the outer electrode 8. Because of the cylindrical geometry of the cell, the heat radiated from the inner electrode 7 is partly reflected and the thermal loss is determined by the absorptivity of the outer electrode 8. With a polished surface the heat loss by the absorptivity of the outer electrode 8 may be kept low. If, for purposes of this example, a 10% absorptivity is assumed for the outer electrode 8 and 50% emissivity for the inner electrode 7, then the heat loss at 3,000 K. is 20 watts/cm. or 126 watts/ cm. length. Conduction heat loss is 11 watts/cm. length. The ionization energy will be 3.87 volts and the kinetic energy will be 0.16 volt so that with 180 amps/cm. length, the loss from these two sources will be 742 watts/cm. of length. The net efiiciency is then output/ (loss-l-output) which is FIGURE 5 shows an arrangement in which the cells are stacked to form a device which is designed primarily as an electrical generator. In the example shown, since the cells have a five centimeter center to center spacing, the arrangement allows for 400 cells per square meter or 900 kilowatts per centimeter of length. Therefore, in one cubic meter of the device there may be generated 9 megawatts of electrical power with 36 megawatts of heat loss. If desired, a coolant and moderator such as water may be circulated between the cells of the device in order to improve the efiiciency of the operation.

Though a prefered practical embodiment of the invention has been described above, it is well to note that instead of using a fission reaction at the inner electrodes 7 to produce heat, uranium vapor may be substituted for the cesium and allowed to react. Since the uranium has an ionization potential of 4 volts, it is thermally ionized in almost the same percentage, at the same temperature, as cesium. In such an arrangement the temperature of the gas may be permitted to react to higher values to produce higher cell voltages and resulting higher efliciencies.

Another form of the cell described using an easily ionized gas such as cesium vapor may utilize a solar energy to heat the inner electrodes rather than a radioactive material such as U In addition other types of heat, such as flue gases from power plants, atomic installations or blast furnaces or from the exhausts of jet engines and rocket missiles may be used. In the case of waste heat from jet engines and rocket missiles, such an apparatus may be used to operate the electrical equipment of the device from which the waste heat is obtained. However, regardless of the heat source utilized or the type of materials used for the electrodes, which as previously mentioned may be tungsten or any material having similar thermal and electrical conductivity properties, the thermal gradient in the ionized plasma between the two electrodes produces the net potential difference and thereby generates electricity directly from another source of energy.

An embodiment of the present invention which utilizes electromagnetic radiation is shown schematically in FIG- URE 6. The device may comprise a cylindrical cell 13 in which an outer cylinder 14 serves as one electrode and an inner centrally disposed cylinder 15 the other electrode. End walls 16 enclose an ionizable gas 17 such as cesium, mercury vapor, argon, or the like. Electromagnetic energy is collected by a suitable device such as an antenna 19 connected to the inner electrode 15 by means of a lead 22. The electromagnetic energy in the form of a high frequency alternating current passes through the cell from the inner electrode 15 to the outer cylinder 14- ionizing the gas. If the electrical impedance of the cell is properly matched, such as by proper choice of dimensions and gas pressure, to the rest of the circuit, a large percentage of the electromagnetic power received is absorbed in the plasma, raising its temperature and producing ionization.

With the cylindrical geometry chosen, the electric field will be strongest at the central electrode. Since power is absorbed in the plasma by coupling through the elec/ trons, the electrons in the vicinity of the central electrode will have the highest temperature. This creates the required gradient in the electron temperature to produce a potential difference between the inner and outer cylinders in the same manner as in the embodiment shown in FIGURE 3. Ifa load is connected between the inner and outer cylinders, a negative current flows out of the inner. cylinderdelivering .electn'calpower to the load. To preventthe high frequency alternating current from passing through the load,and thus reducing the current flowing in. the desired path through the cell, a choke coil 20 or other device having a high impedance to high frequency current but having :a low impedance to the load the load to. the cell as is shown in FIGURE 6.

Becausethet ionization which is produced in the cell as described .doesnot .dec'ay instantly, and although the high. frequency alternating current may be of sinusoidal form passing through zero twice each cycle, the ionization tends to persist during the period when the high frequency alternating current passes through zero, and the unidirectional current through the load is nearly constant at a valuewdetermined by the magnitude of the high frequency current. If the magnitude of the high frequency current varies slowly, the ionization level and the load current will vary in a like manner. By proper choice of dimensions of the cell and type of gas mixture used, the ionization level can be made to follow more rapid changes in the. magnitude of the high frequency current. Underthese conditions, the electromagnetic radiation can be modulated at a commercial power frequency with the result being that the current supplied to the load will vary fromzero to maximum at the commercial power frequency rate. By using a filter or transformer to couple to. a load, the direct current component can be removed leaving a pure alternating current. This principle may also be extended to audio or higher frequencies if desired. In FIGURE 6, the collector for the electromagnetic radi ation is shown connected to the cell by means of a single lead 22. if Conventional coaxial conductors or wave guides may; also be used to deliver the electromagnetic energy to the cell.

Although particular embodiments of the present invention have been described, many modifications may be made and it is understood to be the intention of the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for converting energy in a first form into electrical energy comprising:

(a) an enclosure,

(b) an ionizable gaseous medium within said enclosure, said medium constituting the primary source of electrons,

(c) means for ionizing said gaseous medium,

(d) a first electrode in contact with said medium and subject to bombardment by both positive ions and electrons from said medium,

(e) a second electrode in contact with said medium and spaced from said first electrode, said second electrode also subject to bombardment by both positive ions and electrons from said medium,

(f) means for producing a thermal gradient in said medium between said spaced electrodes, said thermal gradient causing a greater number of electrons and positive ions to strike one of said electrodes than the other of said electrodes so that a potential differ ence is established therebetween, and

(g) means for utilizing said potential difference.

2. An. apparatus for converting energy as described in claim 1 wherein said ionizing means and said means current'is inserted in series with the lead 21 connecting" for producing a thermal gradient are located nearer one of said electrodes than the other of said electrodes.

3. An apparatus for converting energy as described in claim 1 wherein said first electrode comprises said enclosure and said second electrode is cooled in order to produce the thermal gradient.

4. An apparatus for converting energy as described in claim 1 wherein said ionizing means comprises radiation means.

5. An apparatus for converting energy as described in claim 1 wherein said ionizing means comprises a high frequency electric field.

6. An apparatus for converting energy as described in claim 5 further including means for modulating said high frequency electric field to produce a lower frequency voltage for said utilizing'means.

7. An apparatus for converting energy as described in claim 1, wherein said first probe comprises an inner cylinder, said second probe comprises an outer concentric cylinder, said outer concentric cylinder also comprising said enclosure, and said thermal gradient producing and ionizing meansare disposed within said inner cylinder.

8. Apparatus for converting energy in a first form into electrical energy comprising:

(a) an enclosure,

(c) means for ionizing said gaseous medium,

(d) a first electrode in contact with said medium and subject to bombardment by both positive ions and electrons from said medium, said first electrode also comprising said enclosure,

(e) a container centrally disposed within said enclosure,

(f) a plurality of second electrodes, said plurality of electrodes being disposed about said container and being subject to bombardment by both positive ions and electrons from said medium,

(g) means for producing a thermal gradient in said medium between said first and said second electrodes, said ionizing means and said thermal gradient producing means being disposed within said container, said thermal gradient causing a greater number of electrons and positive ions to strike one of said electrodes than the other of said electrodes so that a potential difference is established therebetween, and

(h) means for utilizing said potential difference.

9. Apparatus for converting energy as described in claim 8 wherein said plurality of second electrodes are cooled in order to further aid in setting up the thermal gradient in said medium.

10. Apparatus for converting energy as described in claim 9 wherein said plurality of cooled electrodes comprise hollow cylindrical members through which water passes.

11. Apparatus for converting energy of a first form into electrical energy comprising:

(a) an enclosure,

(c) means for ionizing said gaseous medium,

((1) a first electrode in contact with said medium and subject to bombardment by both positive ions and electrons from said medium, said first electrode also comprising said enclosure,

(e) a second electrode in contact with said medium and spaced from said first electrode, said second electrode also subject to bombardment by both positive ions and electrons from said medium, said second electrode being centrally disposed within said enclosure,

(f) a plurality of containers disposed between said first and said second electrodes,

(g) means for producing a thermal gradient in said medium, said thermal gradient causing a greater number of electrons and positive ions to strike one of said electrodes than the other of said electrodes so that a potential difierence is established therebetween, said thermal gradient producing means and said ionizing means being disposed in said plurality of containers, and

(h) means for utilizing said potential difference.

12. Apparatus as described in claim 11 wherein said second electrode is cooled in order to further aid in setting up the thermal gradient in said medium.

13. A device for generating electrical enegy comprismg:

(a) a plurality of cells in stacked arrangement, each of said cells comprising an inner cylindrical tungsten electrode and an outer concentric cylindrical tungsten electrode, said outer tungsten electrode also comprising an enclosure for said generator,

(b) an ionizable cesium vapor contained between said electrodes, said vapor constituting a primary source of electrons, V

(c) a core of U-235 within said inner electrode for difference is established therebetween, and (d) means for connecting a load to said devicev to utilize the potential difference developed by said cells.

References Cited by the Examiner UNITED STATES PATENTS 2,598,925 6/1952 Linder 3104 X 2,718,786 9/1955 Ohmart 3104 X 2,754,442 7/1956 Bontry 310-4 X 2,817,776 12/1957 Cohen 310-4 X 2,837,666 6/1958 Linder 3104 X 2,980,819 4/1961 Feaster 3104 3,021,472 2/ 1962 Hernquist 310-4 X 3,113,091 12/1963 Rasor 3104 X MILTON O. HIRSHFIELD, Primary Examiner. J. W. GIBBS, Assistant Examiner.

Claims

1. APPARATUS FOR CONVERTING ENERGY IN A FIRST FORM INTO ELECTRICAL ENERGY COMPRISING: (A) AN ENCLOSURE, (B) AN IONIZABLE GASEOUS MEDIUM WITHIN SAID ENCLOSURE, SAID MEDIUM CONSTITUTING THE PRIMARY SOURCE OF ELECTRONS, (C) MEANS FOR IONIZING SAID GASEOUS MEDIUM, (D) A FIRST ELECTRODE IN CONTACT WITH SAID MEDIUM AND SUBJECT TO BOMBARDMENT BY BOTH POSITIVE IONS AND ELECTRONS FROM SAID MEDIUM, (E) A SECOND ELECTRODE IN CONTACT WITH SAID MEDIUM AND SPACED FROM SAID FIRST ELECTRODE, SAID SECOND ELECTRODE ALSO SUBJECT TO BOMBARDMENT BY BOTH POSITIVE IONS AND ELECTRONS FROM SAID MEDIUM, (F) MEANS FOR PRODUCING A THERMAL GRADIENT IN SAID MEDIUM BETWEEN SAID SPACED ELECTRODES, SAID THERMAL GRADIENT CAUSING A GREATER NUMBER OF ELECTRONS AND POSITIVE IONS TO STRIKE ONE OF SAID ELECTRONS AND THE OTHER OF SAID ELECTRODES SO THAT A POTENTIAL DIFFERENCE IS ESTABLISHED THEREBETWEEN, AND (G) MEANS FOR UTILIZING SAID POTENTIAL DIFFERENCE.