Patent Publication Number: US-8987578-B2

Title: Energy conversion device

Description:
TECHNICAL FIELD 
     This invention relates generally to the field of energy devices and more specifically to energy conversion devices. 
     BACKGROUND 
     Radioactive decay is the process in which an unstable atomic nucleus spontaneously loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type, called the parent nuclide, transforming to an atom of a different type, named the daughter nuclide. A nuclide is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons, its number of neutrons, and its excited state. Isotopes are different types of atoms of the same chemical element, each having the same number of protons and a different number of neutrons. 
     SUMMARY OF THE DISCLOSURE 
     According to one embodiment, an energy conversion device comprises a nuclear battery, a light source coupled to the nuclear battery and operable to receive electric energy from the nuclear battery and radiate electromagnetic energy, and a photocell operable to receive the radiated electromagnetic energy and convert the received electromagnetic energy into electric energy. The nuclear battery comprises a radioactive substance and a collector operable to receive particles emitted by the radioactive substance. 
     Certain embodiments of the invention may provide one or more technical advantages. A technical advantage of one embodiment may include the capability to provide a longer-life battery that can be used in roughly the same mechanical and electrical manner as a conventional electrochemical battery. Another technical advantage of one embodiment may include the capability to provide low-voltage power from a nuclear power source. Yet another technical advantage of one embodiment may include the capability to provide power over an extended lifetime and eliminate the need of an on/off switch from some electronic devices. 
     Various embodiments of the invention may include none, some, or all of the above technical advantages. One or more other technical advantages may be readily apparent to one skilled in the art from the figures, descriptions, and claims included herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows an energy conversion system according to one embodiment; 
         FIG. 2  shows an energy conversion system according to one embodiment; 
         FIGS. 3A ,  3 B, and  3 C shows a cylindrical energy conversion system according to one embodiment; 
         FIG. 4  shows stacked energy sources and energy collectors according to one embodiment; and 
         FIG. 5  shows an energy conversion system according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     It should be understood at the outset that, although example implementations of embodiments of the invention are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or not. The present invention should in no way be limited to the example implementations, drawings, and techniques illustrated below. Additionally, the drawings are not necessarily drawn to scale. 
     Electrochemical Cell Batteries 
     Electric power in batteries may be provided through electrochemical reactions inside an enclosure. Examples include AA and AAA batteries. Once a resistive load is attached to one or more of these batteries, they will discharge their electrochemical potential into that load. As that energy is dissipated into that load, the energy stored in the battery will deplete over an amount of time proportional to the load placed on the battery. A typical AA battery may have a maximum energy storage capacity of perhaps 10,000 Joules, which will be consumed over some period of time. Once depleted, the electrochemical cell battery must be either replaced or recharged. This process is very costly. Accordingly, teachings of certain embodiments recognize the capability to provide a longer-life battery that can be used in roughly the same mechanical and electrical manner as a conventional electrochemical battery. 
     Radioactive Decay Process 
     A radioactive substance is an unstable isotope which will be permanently transformed by some nuclear decay process. Example decay processes include alpha decay and beta decay. When that transformation occurs, an unstable isotope (in alpha and beta decay) will emit radiation in the form of a particle and in the process lose some energy, which will be taken out of that nucleus by the emitted particle. The nucleus will tend towards a more stable state; although the new nucleus may still be radioactive it is one step closer in the decay chain toward a stable isotope. 
     Alpha radiation is a form of nuclear fission in which an atom splits into two smaller atoms and releases kinetic and electrical energy. Alpha particles (the emitted particle involved in alpha radiation) are identical to the nucleus of a helium atom (two protons and two neutrons) with no attached electrons. There are many known sources of alpha radiation. One example is Americium-241, which is used in many types of smoke detectors. 
     Beta radiation is a form of nuclear decay in which an atom releases a beta particle. Beta radiation comes in two forms, beta minus which is the release of electrons, and beta plus which is the release of positrons. There are many natural sources of beta radiation in nature. One example is as tritium, an isotope of hydrogen. 
     Nuclear Power Sources 
       FIG. 1  shows an energy conversion system  100  according to one embodiment. Energy conversion system  100  converts nuclear energy into electrical energy. Energy conversion system  100  features an energy source  110  and an energy collector  120 . 
     Energy source  110  includes a substrate  112 , a coating  114 , and an emitting layer  116 . In some examples, substrate  112  may be either a conductor, such as a metallic substrate, or an insulator, such as a plastic substrate. In the illustrated example, substrate  112  is a 250 μm-thick, stainless steel substrate, coating  114  is a 5 μm-thick polyimide coating, and emitting layer  116  is a 3 μm-thick nuclear source layer. In this example, emitting layer  116  is a radioactive substance that undergoes a nuclear decay process. Energy collector  120  includes a substrate  122  and a coating  124 . In the illustrated example, substrate  122  is a 250 μm-thick, stainless steel disk, and coating  124  is a 25 μm-thick polyimide coating. 
     In some embodiments, energy source  110  and energy collector  120  are separated by some distance. Teachings of certain embodiments recognize that energy source  110  may emit particles that travel across this distance before striking energy collector  120 . The distance may be of any suitable length. For example, teachings of certain embodiments recognize that the length of the distance may be optimized based on a desired capacitance across the distance. Also, teachings of certain embodiments recognize that the maximum length of the distance may be limited to the distance that particles can travel and still strike energy collector  120 . 
     In operation, emitting layer  116  emits charged particles that strike a conductor, such as substrate  122 . In the illustrated embodiment, the emitting layer  116  is applied to a second conductor, substrate  112 . In some examples, substrate  112  acts as a support structure only; in other embodiments, substrate  112  may act as a second collector. As a result of electrical charge transfer, substrate  122  will acquire an electrical charge, and energy conversion system  100  will generate electric power  150 . 
     In this example, energy source  110 , which has an electrical charge, emits a particle such as a beta particle, and energy collector  120  struck by the particle acquires the opposite charge. This opposite charge may be opposite in both sign and magnitude. Teachings of certain embodiments recognize that the two electrodes may maintain a difference of potential for as long as charged particles are emitted from energy source  110  and these emissions strike energy collector  120 . An electrical load may be attached to the two electrodes so that the separated charge from one electrode may pass through the load and recombine with the charge on its companion electrode. In this manner, energy source  110  that spontaneously emits charged particles may be made to provide an electric power source. Accordingly, teachings of certain embodiments recognize that a nuclear ‘battery’ may have many applications including the replacement of many disposable and rechargeable batteries now used in commercial and military applications. 
     However, for optimal efficiency, the voltage difference across the electrodes of a typical nuclear battery should be on the order of the energy of the particles emitted from the nuclear material. This voltage is typically very high, and such nuclear batteries tend to provide extremely high output voltage and extremely low output current. 
     For example, Tritium is a nuclear isotope that emits beta particles and photons with the beta particle carrying away roughly 5700 electron volts of kinetic energy. In order to obtain the maximum conversion efficiency of a nuclear battery based on the isotope of Tritium, the electrodes in this battery should be spaced so that they may be charged, via the absorption of the beta emissions, to slightly less than 5700 volts. If this is not the case, the particle will retain excess kinetic energy when it strikes the collection electrode; this excess kinetic energy will be lost as heat, light, or another form of energy. 
     In addition to optimizing the voltage difference based on the order of the energy of the particles emitted from the nuclear material, one may improve nuclear battery efficiency by matching the resistance of the load connected to the nuclear battery to the internal resistance of the battery. For example, if a layer of beta-emitting tritium material generates an assumed 1 milliampere of current, the internal resistance of an optimized tritium battery would be 5700 volts/0.001 amperes=5.7 megohms. Thus, optimal efficiency for power transfer from the battery would require the load to have a resistance of the same value (a matched load) of 5.7 megohms. However, many electrical devices require a much lower operating voltage and have a much lower load resistance. A typical AA battery has an output voltage of 1.5 volts and an internal resistance of less than 1 ohm. 
     Accordingly, teachings of certain embodiments recognize the capability to provide an efficient battery based on nuclear emissions with an output voltage commensurate with the requirements of modern battery-powered devices. Thus, teachings of certain embodiments recognize the capability to efficiently convert the high voltage output of a nuclear power source into lower voltage and lower effective internal resistance. 
       FIG. 2  shows an energy conversion system  200  according to one embodiment. Energy conversion system  200  converts nuclear energy into electrical energy  250 . Energy conversion system  200  features an energy source  210 , one or more energy collectors  220 , a light source  230 , and a photocell  240 . 
     In this example, energy source  210  is a radioactive substance that undergoes a nuclear decay process. Energy collectors  220  may represent any conductors configured to detect particles emitted by energy source  210 . Examples of energy source  210  and collectors  220  may include energy source  110  and energy collector  120  of  FIG. 1 . 
     Light source  230  may represent any device operable to receive electric power from energy source  210  and/or energy collectors  220  and radiate electromagnetic energy, such as light. Examples of light source  230  may include light-emitting diodes (LEDs); laser diodes, such as vertical-cavity surface-emitting lasers (VCSELs); transverse electric lasers; and electroluminescence devices. Electroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light as the result of radiative recombination of electrons and holes in a material, such as a semiconductor. 
     Light source  230  may include one or more individual light sources. For example, light source  230  may include multiple LEDs connected in a series such that the forward voltage of the series of diodes is equal to the electrical output voltage of energy source  210 . 
     Photocell  240  may represent any device suitable to receive the radiated electromagnetic energy and convert the radiated electromagnetic energy into electric power  250 . One example of photocell  240  may include a photovoltaic cell, such as a solar cell. 
     In operation, energy source  210  emits charged particles that strike energy collectors  220 . As a result of electrical charge transfer, energy collectors  220  will acquire an electrical charge generate electric power. Light source  230  will receive this electric power and radiate electromagnetic energy. Photocell  240  receives the radiated electromagnetic energy and converts the electromagnetic energy into electric power  250 . 
     Energy conversion system  200  may be constructed in any suitable manner. For example,  FIGS. 3A ,  3 B, and  3 C show a cylindrical energy conversion system  300  according to one embodiment. Energy conversion system  300  converts nuclear energy into electrical energy  350 . Energy conversion system  300  features an energy source  310 , one or more energy collectors  320 , a light source  330 , and a photocell  340 . 
     In this example embodiment, energy conversion system  300  is housed in a cylindrical body  360 . Body  360  may be formed out of any suitable material. For example, in some embodiments, body  360  is a conductor, such as a metal body, or an insulator, such as a plastic body. In some embodiments, body  360  may act as an outer conductor and shield, absorbing particles from a radioactive material such as energy source  310  and shielding those particles from escaping outside energy conversion system  300 . 
     In this example embodiment, energy source  310  and energy collectors  320  are shown as layers of material wrapped inside of body  360 . For example, energy source  310  and energy collectors  320  may be rolled around each other and fit within body  360 , as shown in  FIG. 3A . However, teachings of certain embodiments recognize that energy source  310  and energy collectors  320  may be disposed within body  360  in any suitable manner. 
     Energy sources  310  and energy collectors  320  may be paired and arranged in any suitable manner. For example, the embodiment shown in  FIG. 3B  features energy source  310  disposed between two layers of energy collectors  320 . In this example, when the energy source  310  and energy collectors  320  are rolled inside body  360 , a cross-section of the roll would appear as follows: energy collector  320 , energy source  310 , energy collector  320 , energy collector  320 , energy source  310 , energy collector  320 , etc. Each energy collector  320  is situated between an energy source  310  and another energy collector  320 , and each energy collector  320  only absorbs particles from the one adjacent energy source  310 . 
     In another example, the embodiment shown in  FIG. 3C  features energy source  310  disposed next to one layer of energy collectors  320 . In this example, when the energy source  310  and energy collector  320  are rolled inside body  360 , a cross-section of the roll would appear as follows: energy collector  320 , energy source  310 , energy collector  320 , energy source  310 , energy collector  320 , energy source  310 , etc. Each energy collector  320  is situated between two energy sources  310 , and each energy collector  320  absorbs particles from both adjacent energy sources  310 . 
       FIGS. 3A ,  3 B, and  3 C show example embodiments of layers of energy sources  310  and energy collectors  320  rolled inside of a cylindrical body  360 . However, teachings of certain embodiments recognize that embodiments are not limited to a cylindrical body  360 , but rather energy conversion device  300  may be of any suitable shape and dimensions. 
     Additionally, teachings of certain embodiments recognize that energy sources  310  and energy collectors  320  are not limited to being rolled together. Rather, energy sources  310  and energy collectors  320  may be arranged in any suitable manner. 
     For example,  FIG. 4  shows stacked energy sources  410  and energy collectors  420  according to one embodiment. Unlike the examples shown in  FIGS. 3A ,  3 B, and  3 C, which features a single energy source  310  wrapped inside body  360 ,  FIG. 4  shows multiple, discrete energy sources  410  stacked between multiple, discrete energy collectors  420 . 
     Energy sources  410  and energy collectors  420  may be of any suitable shape or size. For example, in one embodiment, energy sources  410  and energy collectors  420  may be circular so as to fit inside the cylindrical body  360  of  FIG. 3A . In another example embodiment, energy sources  410  and energy collectors  420  may be square or rectangular so as to fit inside a square or rectangular energy conversion device. 
       FIG. 5  shows an energy conversion system  500  according to one embodiment. Energy conversion system  500  features energy source  310 , one or more energy collectors  320 , a light source  330 , and a switch  510 . Switch  510  may represent any switch configured to turn on and/or turn off energy conversion system  500 . For example, in one embodiment, switch  510  may turn on and/or turn off light source  330 . In some embodiments, energy conversion system  500  does not feature a switch  510 . 
     Teachings of certain embodiments recognize that energy conversion system  500  may provide electromagnetic light energy for longer periods of time than traditional light sources, such as flashlights powered by alkaline, zinc-carbon, or lithium batteries. However, teachings of certain embodiments are not limited to flashlights; rather, energy conversion system  300  may be used to transmit light in any suitable environment for any suitable use. 
     In the embodiment of  FIG. 5 , energy conversion system  500  is cylindrical. However, teachings of certain embodiments recognize that energy conversion system  500  may be any suitable shape. 
     Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. Additionally, operations of the systems and apparatuses may be performed using any suitable logic. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
     Although several embodiments have been illustrated and described in detail, it will be recognized that substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the appended claims. 
     To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.