Patent Application
20080245407
Process, machine, manufacture, composition of matter, and improvements thereto, with particular regard to radioactive decay of isotopes, fission of nuclear materials, fusion, chemical reactions, and the like in generating electrical power.
Turn now to the accompanying drawings, which illustrate embodiments in detail intended to illustrate and exemplify in a teaching and prophetic manner, rather than limit—much like teaching mathematical addition by examples rather than by an explicit compendium of all addition possibilities.
This thermal energy is conducted via convection, radiation, or physical coupling to a surface 20 that radiates this thermal energy in the form of blackbody radiation 25. Because the blackbody radiation spectrum is so broad, prior technologies at harnessing this energy for power production were limited in acceptance and hence operated at reduced efficiency. By reflecting the long wavelength 50 portion of this radiation back toward said emitting surface 20 and transmitting only the upper short wavelength 35 edge of the blackbody radiation spectrum, only a narrow band 730 in the electromagnetic spectrum is transmitted for harvesting via photovoltaic 380 conversion 40 into electrical power 45. A device capable of reflecting long wavelengths and transmitting short wavelengths is called a hot mirror 30.
In a particular embodiment particularly suitable as a teaching example, consider a system architecture in which radioisotopic nuclear decay energy 110 is completely or essentially encapsulated within a tungsten shell 320, and converting, with high efficiency, the energy from the decay into thermal energy 15. See
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Embodiments that follow this example can be directed to any isotope according to its power density and radiation leakage properties. Low leakage rates can equate to low possibility of radiation induced degradation of any active component of the system. As seen in
Consider the following variations on the theme for such a power source architecture and accompanying isotope synthesis:
1) Electrical power conversion 40 efficiencies can be in the range of at least 10%, preferably in the range of 10% to 30%, and more preferably in the range of more than 30% to achieve power densities. However, in this particular example, the end supports do transmit some thermal power (see
2) In the case of radioisotopes 310 as the source of thermal energy, radiation leakage at 1-foot can be in the range of 100 to 500 mrem/year, preferably in the range of 50 to 100 mrem/year, and more preferably in the range of less than 50 mrem/year.
3) In the case of radioisotopes 310 as the source of thermal energy, sealed source geometry that shields surrounding materials and electronics to radiation levels at or below normal background. The volume of isotope and the thickness of the tungsten shield can be selected in amounts traded against each other to accommodate a broad range of suitable isotopes. For example, a 35 milliwatt electric power source can fit into a 1 cc volume wherein the thickness of the tungsten shell is approximately 1.2 mm. This kind of configuring of the encapsulation of the source of radiation prevents radiation induced degradation of active components.
4) Power conversion can be adapted to output continuous electrical power 45, e.g., into fixed electrical impedance, regardless of the age of the isotope 310 (i.e., with respect to its half-life).
5) Passive titanium vacuum gettering can be used behind the end mirrors 360 to preserve the thermal insulation vacuum 355 around the tungsten shell 320. Specific assembly of this architecture in a vacuum 355 system can allow the radiative heat from the tungsten shell 320 to vacuum process the components before sealing the outer casing 390.
6) Embodiments can be configured for a low thermal signature. Due to total efficiencies in the ranges of 10% to 50%, preferably greater than 50% or an embodiment with an efficiency of approximately 33%, a 35 mWe (milliwatt electric) power source can have a surface heat dissipation rate of only 0.1 Watt. At this power level, an initial shape of a 1 cc unit is similar to a 0.75″ section of a standard pencil. Thus such an embodiment can be about twice as long, and about three times larger in surface area, of a standard 1 Watt resistor, and therefore remain close to room temperature.
Heat leak calculations of the end supports are shown in
Tungsten has an emissivity that is very low (˜0.05) at infrared wavelengths and almost 0.5 at visible wavelengths. Depending on surface roughness, a variety of specific emissivity curves 400 are summarized in
Surrounding the tungsten shell surface 325 can be highly efficient infrared reflectors (hot mirrors) composed of a thin gold film 370 on a transparent substrate 375, which can suddenly become transparent between 600 and 900 nm. The temperature of the tungsten shell 320 increases until the visible photon power transmitted 730 through the hot mirrors 30 essentially just equals the heat generation power 10 of the radioisotope 310.
In such an embodiment, an architecture can created in which the photon power spectrum is precisely tuned to the peak response of a high-efficiency power conversion device 40. A summary of the spectral efficiencies of a number of photovoltaic technologies are illustrated in
Representing still another embodiment, by using an alternative hot mirror 30 technology that transmits light starting at either 1.2 or 1.7 microns, significantly lower tungsten surface 325 temperatures can be used. The result is less heat leak out the end supports 330. Preliminary calculations suggest that the overall system efficiency would drop from about 33% to approximately 20%.
Representing another embodiment, consider a manner of adjusting an architecture for embodiments herein, represented by an output power 45 of 35 mWe deposited into a 50Ω load corresponds to a voltage of 1.3 V and a current of 38 mA. Because the output power of radioisotopes 310 decay with time, the initial power level of radioisotope power sources will be much higher, and decay down to 35 mWe after a few half-lives. By employing pairs of tap that the user can electronically short or open via semiconductor gates, progressively more of the photovoltaic 380 surface area can be brought online while the isotope activity decays. These latter sections of surface area are wired in compensating parallel-series configurations to yield an overall net output impedance of roughly 50Ω. While not a continuous load adjustment, several surface area steps can be implemented that approximate a constant 50Ω output impedance.
This power conditioning solution consumes negligible additional mass and essentially zero power source volume. It also can provide a means for direct control over power delivery. For example, assume higher amounts of peak power are to be utilized periodically, so as to benefit from the control. Alternatively, one can set the current vs voltage I-V operating point of the photovoltaic cells 380 to maximum efficiency at the end of operational life of the power source, and then run off-optimum at the beginning of the half-life decay curve of the radioisotope 310.
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Embodiments of emergency power applications 810 include recharging vehicle batteries that have run down, preventing the owner from starting the vehicle. It also includes backup power in the case of a terrorist attack on the electrical grid infrastructure.
Embodiments of remote power applications 820 include camp site and cabin power, power at scientific field locations, and pumping stations for field irrigation. Basically, any temporary power requirement not conveniently connected to the electrical grid qualifies under this application 800 category.
Embodiments of military and security applications 830 include powering weapon systems, recharging batteries carried by soldiers for range finders and radios, powering listening posts and other remote intelligence gathering equipment, powering portable radiation monitoring stations, and providing robust power for underwater operations such a welders employed by divers, powering smart mines, and propelling torpedoes. Embodiments include applications requiring operations in extreme temperatures, pressures, and oxygen deficiency environments that are beyond the capabilities of current power generation and storage systems.
Embodiments of vehicle power and propulsion applications 840 include automobile power, either for all or a portion of the power, used to propel the automobile. Further embodiments include vehicles such as trucks, boring machines, and locomotives. Further embodiments include vehicle power, such as for hydraulic system pumps and energy recovery from high-efficiency regenerative brakes employing the technology of embodiments herein.
Embodiments of aircraft power and propulsion applications 850 include direct power for an electric motor driving a propeller. Further embodiments include aircraft power for navigation, communications, and weapon systems.
Embodiments of watercraft power and propulsion applications 860 include propulsive power for boats, ships, hovercrafts, and jet skis. Further embodiments include onboard power for equipment such as fish finders, bottom finders, sonar systems, and weather radar.
Embodiments of spacecraft power and propulsion applications 870 include electrical power for ion engines. Further embodiments include scientific instrument, navigation, temperature control, and communication power,
Embodiments of grid electrical power generation applications 880 include energy storage during off-peak demand times by regenerating embodiments based on chemical reactions. In this embodiment, chemical reaction products would be reformed back into their original chemical reactant form. Another embodiment includes electrical power generation during peak demand times by converting solar energy.
Consider now a broader application of the foregoing teaching, with regard to conversion of a source of energy into electrical power. The teachings herein facilitate an apparatus, method of making the apparatus, and method of using the apparatus. The apparatus, depending on preferred implementation, be adapted to generate electrical power by conversion from a source of energy, with no moving parts, and with energy conversion efficiency greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, and more preferably greater than 80%. Inefficient power systems have heretofore been a technical problem, and the embodiments herein and thereby offer a technical solution thereto.
Note that the foregoing is a prophetic teaching and although only a few exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate from this teaching that many modifications are possible, based on the exemplary embodiments and without materially departing from the novel teachings and advantages herein. Accordingly, all such modifications are intended to be included within the scope of the defined by claims. In the claims, means-plus-function claims are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment fastening wooden parts, a nail and a screw may be equivalent structures.
This patent application is a continuation-in-part, claiming priority from, and incorporating by reference, the provisional patent applications “Power Source Based on Tuned Photovoltaic Conversion,” Ser. No. 60/833,335, filed Jul. 26, 2006; and “Chemical Conversion Based on Photovoltaic Conversion”, Ser No. 60/900,866, filed Feb. 12, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60833335 | Jul 2006 | US | |
| 60900866 | Feb 2007 | US |
