Method and apparatus for converting energy to electricity

A method and apparatus are provided for converting electromagnetic radiation directly into electricity. The method aligns a plurality of ferromagnetic nanocrystals to produce an aggregate magnetic field; utilizes an electrical coil in the aggregate magnetic field; and alternately directs and removes radiant energy from the ferromagnetic nanocrystals such that the aggregate magnetic field decays and regenerates to produce a current in the electrical coil. The apparatus includes either a distribution or a stackup of ferro-magnetic nanocrystals and an electrical coil, the combination of the nanocrystals and the electrical coil operating with energy derived from the source of radiant energy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the direct conversion of radiant energy into electricity, and more particularly, to a method and apparatus for producing electricity by causing a magnetic field to alternatingly decay and regenerate.

2. Description of the Prior Art

Historically, electricity has been produced by using a generator device to move an electrical coil and a magnetic field relative to one another. Such methods require mechanical moving parts which can wear out or break down and create an interruption in providing electrical power to components.

Various methods have been proposed to directly convert an energy source directly into electricity. U.S. Pat. No. 5,714,829 issued to Gurusprasad, for example, discloses a magnetic mechanical heat engine for converting heat into electricity using electromotive force induced by demagnetization. The heat engine utilizes a magnetic medium which is magnetized by means of a magnetic field produced by an external electrical coil. However, operation of the apparatus disclosed in Gurusprasad '829 requires that the magnetic medium be brought into and out of thermal contact with a heat source, which thus necessitates moving parts and reduces the efficiency of the apparatus.

What is needed is an apparatus for efficiently converting energy directly into electricity.

SUMMARY OF THE INVENTION

The present invention provides a method and an energy conversion device for efficiently converting radiant energy directly into electricity.

In one general aspect of the present invention, a first embodiment comprises a distribution of ferro-magnetic nanocrystals and an electrical coil, the combination operating with energy directed from a radiation source.

In another general aspect of the present invention, a second embodiment comprises two distributions of ferromagnetic nanocrystals, a pair of electrical coils enclosing the ferromagnetic nanocrystals, and a controllable radiation source.

In yet another general aspect of the present invention, a third embodiment comprises a controllable radiation source, a plurality of transparent annular disks alternatingly stacked with a plurality of soft magnetic disks coated with ferromagnetic nanocrystals embedded in a matrix layer, a transparent cylindrical core, and an electrical coil enclosing the stacked annular disks and cylindrical core.

In a further general aspect of the present invention, a method is provided for converting energy from a radiant source into electricity. Initially, a plurality of ferromagnetic nanocrystals are aligned so as to produce an aggregate magnetic field; an electrical conductor is placed into the aggregate magnetic field; and radiant energy is directed onto the plurality of ferromagnetic nanocrystals such that the aggregate magnetic field begins to decay. The radiant energy is then attenuated, allowing the aggregate magnetic field to regenerate, and the process is repeated inducing electric current in the electrical conductor in response to the changing magnetic field.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Shown throughout the figures, the present invention is generally directed to a method and device for producing electricity. In comparison to other methods known in the art, the method of the present invention provides an elegant and efficient process for directly converting energy into electricity.

Referring initially toFIGS. 1–2, an energy conversion device, shown generally as reference numeral10, includes a magnetic dipole module11enclosed by an electrical coil13having a plurality of ‘N’ turns or windings. The electrical coil13is thus immersed in a magnetic field produced by the magnetic dipole module11. For clarity of illustration, only a first turn15, a second turn17, and a third turn19are shown in the diagrammatical representation ofFIG. 1, but it should be understood that the number of turns or windings is much greater than three turns.

The magnetic dipole module11may be generally cylindrical in shape having a module longitudinal axis21and comprising a plurality of ferromagnetic nanocrystals23distributed within a matrix25. The ferromagnetic nanocrystals23are preferably single-domain particles or smaller, and each ferromagnetic nanocrystal23comprises a material having a Curie temperature denoted by TC.

Each ferromagnetic nanocrystal23has an associated nanocrystal magnetic dipole moment27generally aligned along the module longitudinal axis21. In this aligned configuration, each nanocrystal magnetic dipole moment27contributes to a module aggregate magnetic field29, designated by the vector symbol {right arrow over (B)} and defined in accordance with a vector coordinate system31.

The magnetic dipole module11may also include a rod-shaped core magnet33having a core magnetic dipole moment35aligned along, and preferably coincident with, the longitudinal axis21. This aligned configuration serves to ensure that the contribution of the core magnetic dipole moment35to the strength of the module aggregate magnetic field29is optimal.

The core magnet33may comprise a permanent magnet, for example, or an electromagnet to provide a greater core magnetic dipole moment35than may be possible with a permanent magnet of similar size. A stronger core magnetic dipole moment35can, in turn, increase the magnetic strength of the ferromagnetic nanocrystals23which can, accordingly, subject the turns or windings of the electrical coil13to a greater magnetic flux produced by the magnetic dipole module11.

Because of extremely small physical size, the ferromagnetic nanocrystals23may, under certain conditions, become superparamagnetic. The core magnet33serves to offset this potential occurrence by maintaining the magnetic moment orientation of the ferromagnetic nanocrystals23at temperatures below the Curie temperature until incident radiation decouples the magnetic moments.

The operation of the energy conversion device10follows from Faraday's observation that a transient electrical current can be induced in the electrical coil13if the magnetic field {right arrow over (B)} is changed as a function of time. This changing magnetic field produces a corresponding change in the magnetic flux across the electrical coil13. An electromotive force can be induced in an electrical circuit37comprising the electrical coil13and an external electrical load39in response to this change in the magnetic field {right arrow over (B)}. In accordance with Faraday's Law, the electromotive force is proportional to the time rate of change of the magnetic flux linking the electrical coil13,

E=-k⁢ⅆFⅆtwhere E is the electromotive force around the electrical coil13;k is a constant of proportionality dependent on the choice of units for the electric and magnetic field quantities; andF is the magnetic flux linking the electrical circuit37which includes turns15,17, and19.
The negative value of k indicates that the induced current (and accompanying magnetic flux) is in such a direction as to oppose the change of flux through the windings of the electrical coil13(exemplified by the turns15,17, and19). As can be appreciated by one skilled in the relevant art, the resulting current can be increased by increasing the number of turns ‘N’ in the electrical coil13.

In accordance with the present invention, the magnitude of the magnetic field {right arrow over (B)} can decay and regenerate as a function of radiant energy incident on the energy conversion device10. The radiant energy may be provided in the form of a radiation beam41emitted from a radiation source43, as described in greater detail below.

The matrix25is highly transparent to the wavelength λ of the radiation beam41such that the radiation source43transmits the radiation beam41through an enclosure49and through the matrix25with minimal attenuation to irradiate the ferromagnetic nanocrystals23. Preferably, the wavelength λ of the radiation beam41is also selected so as to effectively impart thermal energy to irradiated ferromagnetic nanocrystals23. In an alternative embodiment, the enclosure49comprises a “soft” magnetic material.

At the start of operation, that is, before the radiation source43is powered to direct the radiation beam41onto the magnetic dipole module11, the ferromagnetic nanocrystals23are initially at an ambient temperature Ta, where Tais less than the Curie temperature TCof the ferromagnetic nanocrystals23. When the energy conversion device10is irradiated by the radiation beam41for a predetermined amount of time, the ferromagnetic nanocrystals23are heated to a temperature of T1or greater, where T1is greater than the Curie temperature TC.

As the respective temperatures of the ferromagnetic nanocrystals23rise above the Curie temperature TC, the magnetic dipole moments27decouple out of alignment with the module longitudinal axis21. The module magnetic field29begins to decay and may decrease to a value approximately that of the core magnetic dipole moment35. This results in a decrease in magnetic flux across the electrical coil13.

After a predetermined period of time, the irradiation of the magnetic dipole module11is reduced or terminated so as to allow heat to flow from the ferromagnetic nanocrystals23into the matrix25. This action can be accomplished by, for example, attenuating the output of the radiation source43or by blocking the radiation beam41. In one embodiment, the radiation source43comprises a pulsed laser device (not shown) which functions to output a radiation beam41, which controllably varies between full power and an attenuated power level.

In an alternative embodiment, the radiation beam41can be blocked by closing a shutter45, such as an optical Kerr cell or similar device, interposed between the radiation source43and the magnetic dipole module11. As the nanocrystals23lose heat to the relatively cooler matrix25, the temperatures of the nanocrystals23drop to a value of T2or lower, where T2lies below the Curie temperature. That is, T2<TC<T1. This drop in temperature allows the magnetic flux to regenerate and to reappear across the electrical coil13.

Operation of the energy conversion device10thus comprises repetitive cycles of alternatingly causing the magnetic flux to decay across the electrical coil13and then enabling the magnetic flux to regenerate. These cycles of decay and regeneration are achieved by alternating the steps of: (1) irradiating the ferromagnetic nanocrystals23to a temperature of T1or higher to cause the magnetic flux to decay, and (2) reducing or terminating the irradiation for a predetermined amount of time to allow the temperatures of the ferromagnetic nanocrystals23to fall below T2so as to enable the magnetic flux to regenerate across the electrical coil13.

In accordance with Faraday's Law, a corresponding electrical current i, indicated by an arrow47, is produced in the electrical coil13with the decay and regeneration of the magnetic flux produced by the ferromagnetic nanocrystals23. The high output frequency of the electrical current i, may be converted to a DC signal, and then to a lower-frequency AC signal, such as a 60 Hz output signal, for example. The energy conversion device10thus functions to directly convert a portion of the energy in the incident radiation beam41into the electrical current i provided to the external electrical load39.

As understood by one skilled in the relevant art, a single domain may be approximately 10−6to 10−2 cm3in size, for example, and may contain 1015to 1021atoms. The small physical sizes of the nanocrystals23thus allow the magnetic flux to be cycled at high frequencies. For example, single-domain particles having temperatures above the Curie temperature TCcan be demagnetized in time intervals as small as one femtosecond. Changing the magnetic field at a high frequency can thus provide a relatively large electrical current even if the magnetic field is relatively small.

The radiation source43can be, for example, a narrowband source such as a laser, or a broadband source such as sunlight. The radiation beam41can thus comprise a range of frequencies best suited to induce heating of the ferromagnetic nanocrystals23. As can be appreciated by one skilled in the art, the broadband sunlight source may be more practical than a narrowband laser source for providing, or boosting, an external electrical current source. In other applications, the best source to provide electricity, e.g., to a subcutaneous cardiac pacemaker or insulin pump, may be a pulsed radio-frequency source.

Referring now toFIGS. 3–4, an energy conversion device, shown generally as reference numeral50, comprises a first ferromagnetic suspension chamber51at least partially enclosed in a first electrical coil53, and a second ferromagnetic suspension chamber55at least partially enclosed in a second electrical coil57. The energy conversion device50further includes a disk-shaped core magnet59disposed between the first ferromagnetic suspension chamber51and the second ferromagnetic suspension chamber55.

The first ferromagnetic suspension chamber51includes a first cylindrical shell61and a first endcap63, and the second ferromagnetic suspension chamber55includes a second cylindrical shell65and a second endcap67. The first cylindrical shell61, the first endcap63, the second cylindrical shell65, and the second endcap67can be fabricated from: (1) aluminum; (2) a nonmagnetic material or soft metal such does not hold a magnetic force when not in a magnetic field; or (3) a “soft” magnetic material. The first ferromagnetic suspension chamber51houses a first ferromagnetic suspension71comprising a distribution of the aligned ferromagnetic nanocrystals23in the matrix25. Likewise, the second ferromagnetic suspension chamber55also houses a second ferromagnetic suspension73comprising a plurality of the ferromagnetic nanocrystals23disposed in the matrix25.

Radiant energy is provided to the energy conversion device50by a radiation source81, such as a pulsed laser source. When operating in accordance with the present invention, the radiation source81provides pulsed radiation (not shown) to the first ferromagnetic suspension71via a first optical fiber83, and pulsed radiation to the second ferromagnetic suspension73via a second optical fiber85. The energy conversion device50, the radiation source81, the first optical fiber83, and second optical fiber83form an energy conversion system20. The radiation pulses may be provided to the two ferromagnetic suspensions71and73either simultaneously or alternately.

Referring now toFIG. 5, in which the first ferromagnetic suspension71is shown in greater detail, the nanocrystals23comprise nickel having a Curie temperature of about 627° K., and the matrix25comprises aluminum oxide. In an alternative embodiment, the nanocrystals23comprise iron having a Curie temperature of about 1043° K. In other alternative embodiments, the nanocrystals23may be formed from: (1) “hard” ferromagnetic crystals comprising metal ions such as cobalt, neodymium, or gadolinium; (2) ferrite crystals comprising metal ions such as cobalt, neodymium, or gadolinium; or (3) ferrites such as yttrium-iron-garnet. When utilized in the first ferromagnetic suspension71, a ferrite crystal may produce a weaker magnetic field than when utilizing a nanocrystal, but the frequency of operation may be greater than that for nonocrystals.

Referring now toFIG. 6, a doped ferromagnetic suspension75is shown comprising a distribution of nanocrystals23in the matrix25. The doped ferromagnetic suspension75further comprises a distribution of dopant particles77comprised of a material such as titanium, copper, yttrium, or other such transition metal. The dopant particles77may serve to scatter the radiation from the radiation source81throughout the first ferromagnetic suspension chamber51or the second ferromagnetic suspension chamber55. In addition, as titanium has a relatively high thermal conductivity, the dopant particles77would also serve to absorb heat from the nanocrystals23. In yet another alternative embodiment, the dopant particles77comprise a material such as Ti:Sapphire—titanium-doped sapphire (Ti3+:Al2O3).

Referring now toFIG. 7, an energy conversion device, shown generally as reference numeral90, comprises a first layered ferromagnetic chamber91at least partially enclosed in the first electrical coil53, and a second layered ferromagnetic chamber93at least partially enclosed in the second electrical coil57. In an alternative embodiment, the energy conversion device90may include the disk-shaped core magnet59disposed between the first layered ferromagnetic chamber91and the second layered ferromagnetic chamber93.

The first layered ferromagnetic chamber91includes the first cylindrical shell61, a first layered ferromagnet95, and the first endcap63. The second layered ferromagnetic chamber93includes the second cylindrical shell65, a second layered ferromagnet97, and the second endcap67. The energy conversion device90can be used with the radiation source81, the first optical fiber83, and the second optical fiber85to form an energy conversion system100, shown inFIG. 8. In an alternative embodiment, the energy conversion system100may comprise the first layered ferromagnetic chamber91, the first electrical coil53, the first optical fiber83, and the radiation source81.

Referring now toFIGS. 9–10, the first layered ferromagnet95comprises a plurality of “soft” ferromagnetic annular disks101alternately stacked with a plurality of inner Ti:Sapphire annular disks103. An outer Ti:Sapphire annular disk105is provided at both ends of the first layered ferromagnet95. The outer Ti:Sapphire annular disk105may also include a coating113which is highly reflective to the wavelength λ of the radiation beam41. The configuration of the second layered ferromagnet97is similar to that of the first layered ferromagnet95.

For clarity of illustration, the perspective view ofFIG. 9shows a stack of four soft ferromagnetic annular disks101and three inner Ti:Sapphire annular disks103but it should be understood that fewer or more soft ferromagnetic annular disks101and Ti:Sapphire annular disks103can be used in the first layered ferromagnet95and in the second layered ferromagnet97.

The first layered ferromagnet95also includes a cylindrical Ti:Sapphire core107extending through the inside of the stack comprising the soft ferromagnetic annular disks101, the inner Ti:Sapphire annular disks103, and the outer Ti:Sapphire annular disks105. Preferably, the Ti:Sapphire core107is disposed along a layered ferromagnet axis109of the first layered ferromagnet95.

Each of the soft ferromagnetic annular disks101includes a ferromagnetic nanocrystal coating111on a first disk face115and on a second disk face117, as best seen inFIG. 10. Each soft ferromagnetic annular disk101also includes a central opening119, each inner Ti:Sapphire annular disks103includes a central opening121, and each outer Ti:Sapphire annular disk105includes a central opening123. Each of the central openings119, the central openings121, and the central openings123is preferably sized to allow insertion of the Ti:Sapphire core107. This configuration provides for the placement of the cylindrical Ti:Sapphire core107into the stack comprising the soft ferromagnetic annular disks101, the inner Ti:Sapphire annular disks103, and the outer Ti:Sapphire annular disks105as shown.

The ferromagnetic nanocrystal coating111comprises a layer of the matrix25having embedded therein a plurality of “hard” ferromagnetic nanocrystals23(not shown) with respective nanocrystal magnetic dipole moments27(not shown) aligned with the layered ferromagnet axis109. The soft ferromagnetic annular disks101comprise a magnetic material having a Curie temperature TCsoftwhere TCsoft>TC, the Curie temperature of the ferromagnetic nanocrystals23. The ferromagnetic nanocrystals23may comprise nickel or iron, as described above, or may comprise iron-nickel-titanium alloy particles of sufficiently large size that the ferromagnetic nanocrystals23are not superparamagnetic. The magnetic dipole moments27produce the module aggregate magnetic field29, shown inFIG. 9.

Operation of the energy conversion system100includes irradiating the first layered ferromagnet95and the second layered ferromagnet97with the radiation beam41, as described above for the energy conversion system20. The radiation beam41is transmitted to the first layered ferromagnet95, for example, via the first optical fiber83. From the first optical fiber83, the radiation beam41is directed into the Ti:Sapphire core107, as indicated by arrow114. As the Ti:Sapphire core107is transparent to the radiation beam41, the radiation beam41is internally scattered into the plurality of inner Ti:Sapphire annular disks103, such as indicated by arrows116and118, and into the two outer Ti:Sapphire annular disks105.

The scattered radiation beam41irradiates the ferromagnetic nanocrystals23embedded in the plurality of ferromagnetic nanocrystal coatings111on the soft ferromagnetic disks101. The nanocrystal magnetic dipole moments27are uncoupled by the incident radiation and begin to decay. This action causes the soft ferromagnetic annular disks101to demagnetize, causes the module aggregate magnetic field29to collapse, and results in the generation of an electrical current in the first electrical coil53as described in greater detail above.

In an alternative embodiment, discs comprising yttrium aluminum garnet (YAG) are used in place of the Ti:Sapphire annular disks103and105, and a core comprising yttrium aluminum garnet is used in place of the Ti:Sapphire core107. Additionally, the yttrium aluminum garnet discs comprise coatings of yttrium-iron-garnet (YIG) nanocrystal particles.

Since many modifications, variations, and changes to detail can be made to the described preferred embodiments of the invention, it is intended that all matters in the foregoing description and shown in the accompanying drawing be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalence.