Direct energy conversion

Last updated

Direct energy conversion (DEC) or simply direct conversion converts a charged particle's kinetic energy into a voltage. It is a scheme for power extraction from nuclear fusion.

Contents

A basic direct converter Direct Converter.jpeg
A basic direct converter

History and theoretical underpinnings

Electrostatic direct collectors

In the middle of the 1960s direct energy conversion was proposed as a method for capturing the energy from the exhaust gas in a fusion reactor. This would generate a direct current of electricity. Richard F. Post at the Lawrence Livermore National Laboratory was an early proponent of the idea. [1] Post reasoned that capturing the energy would require five steps: [2] (1) Ordering the charged particles into linear beam. (2) Separation of positives and negatives. (3) Separating the ions into groups, by their energy. (4) Gathering these ions as they touch collectors. (5) Using these collectors as the positive side in a circuit. Post argued that the efficiency was theoretically determined by the number of collectors.

The Venetian blind

The Venetian blind design is a type of electrostatic direct collector. The Venetian Blind design name comes from the visual similarity of the ribbons to venetian window blinds. Designs in the early 1970s by William Barr and Ralph Moir used repeating metal ribbons at a specified angle as the ion collector plates. These metal ribbon-like surfaces are more transparent to ions going forward than to ions going backward. Ions pass through surfaces of successively increasing potential until they turn and start back, along a parabolic trajectory. They then see opaque surfaces and are caught. Thus ions are sorted by energy with high-energy ions being caught on high-potential electrodes. [3] [4] [5]

William Barr and Ralph Moir then ran a group which did a series of direct energy conversion experiments through the late 1970s and early 1980s. [6] The first experiments used beams of positives and negatives as fuel, and demonstrated energy capture at a peak efficiency of 65 percent and a minimum efficiency of 50 percent. [7] [8] The following experiments involved a true plasma direct converter that was tested on the Tandem Mirror Experiment (TMX), an operating magnetic mirror fusion reactor. In the experiment, the plasma moved along diverging field lines, spreading it out and converting it into a forward moving beam with a Debye length of a few centimeters. [9] Suppressor grids then reflect the electrons, and collector anodes recovered the ion energy by slowing them down and collecting them at high-potential plates. This machine demonstrated an energy capture efficiency of 48 percent. [10] However, Marshall Rosenbluth argued that keeping the plasma's neutral charge over the very short Debye length distance would be very challenging in practice, though he said that this problem would not occur in every version of this technology. [9]

The Venetian Blind converter can operate with 100 to 150 keV D-T plasma, with an efficiency of about 60% under conditions compatible with economics, and an upper technical conversion efficiency up to 70% ignoring economic limitations. [4]

Periodic electrostatic focusing

A second type of electrostatic converter initially proposed by Post, then developed by Barr and Moir, is the Periodic Electrostatic Focusing concept. [2] [5] [11] Like the Venetian Blind concept, it is also a direct collector, but the collector plates are disposed in many stages along the longitudinal axis of an electrostatic focusing channel. As each ion is decelerated along the channel toward zero energy, the particle becomes "over-focused" and is deflected sideways from the beam, then collected. The Periodic Electrostatic Focusing converter typically operates with a 600 keV D-T plasma (as low as 400 keV and up to 800 keV) with efficiency of about 60% under conditions compatible with economics, and an upper technical conversion efficiency up to 90% ignoring economic limitations. [12]

Induction systems

Conduction systems

From the 1960s through the 1970s, methods have been developed to extract electrical energy directly from a hot gas (a plasma) in motion within a channel fitted with electromagnets (producing a transverse magnetic field), and electrodes (connected to load resistors). Charge carriers (free electrons and ions) incoming with the flow are then separated by the Lorentz force and an electric potential difference can be retrieved from pairs of connected electrodes. Shock tubes used as pulsed MHD generators were for example able to produce several megawatts of electricity in channels the size of a beverage can. [13]

Induction systems

In addition to converters using electrodes, pure inductive magnetic converters have also been proposed by Lev Artsimovich in 1963, [14] then Alan Frederic Haught and his team from United Aircraft Research Laboratories in 1970, [15] and Ralph Moir in 1977. [16]

The magnetic compression-expansion direct energy converter is analogous to the internal combustion engine. As the hot plasma expands against a magnetic field, in a manner similar to hot gases expanding against a piston, part of the energy of the internal plasma is inductively converted to an electromagnetic coil, as an EMF (voltage) in the conductor.

This scheme is best used with pulsed devices, because the converter then works like a "magnetic four-stroke engine":

  1. Compression: A column of plasma is compressed by a magnetic field that acts like a piston.
  2. Thermonuclear burn: The compression heats the plasma to the thermonuclear ignition temperature.
  3. Expansion/Power: The expansion of fusion reaction products (charged particles) increases the plasma pressure and pushes the magnetic field outward. A voltage is induced and collected in the electromagnetic coil.
  4. Exhaust/Refuel: After expansion, the partially burned fuel is flushed out, and new fuel in the form of gas is introduced and ionized; and the cycle starts again.

In 1973, a team from Los Alamos and Argonne laboratories stated that the thermodynamic efficiency of the magnetic direct conversion cycle from alpha-particle energy to work is 62%. [17]

Traveling-wave direct energy converter

In 1992, a Japan–U.S. joint-team proposed a novel direct energy conversion system for 14.7 MeV protons produced by D-3He fusion reactions, whose energy is too high for electrostatic converters. [18]

The conversion is based on a Traveling-Wave Direct Energy Converter (TWDEC). A gyrotron converter first guides fusion product ions as a beam into a 10-meter long microwave cavity filled with a 10-tesla magnetic field, where 155 MHz microwaves are generated and converted to a high voltage DC output through rectennas.

The Field-Reversed Configuration reactor ARTEMIS in this study was designed with an efficiency of 75%. The traveling-wave direct converter has a maximum projected efficiency of 90%. [19]

Inverse cyclotron converter (ICC)

Original direct converters were designed to extract the energy carried by 100 to 800 keV ions produced by D-T fusion reactions. Those electrostatic converters are not suitable for higher energy product ions above 1 MeV generated by other fusion fuels like the D-3He or the p-11B aneutronic fusion reactions.

A much shorter device than the Traveling-Wave Direct Energy Converter has been proposed in 1997 and patented by Tri Alpha Energy, Inc. as an Inverse Cyclotron Converter (ICC). [20] [21]

The ICC is able to decelerate the incoming ions based on experiments made in 1950 by Felix Bloch and Carson D. Jeffries, [22] in order to extract their kinetic energy. The converter operates at 5 MHz and requires a magnetic field of only 0.6 tesla. The linear motion of fusion product ions is converted to circular motion by a magnetic cusp. Energy is collected from the charged particles as they spiral past quadrupole electrodes. More classical electrostatic collectors would also be used for particles with energy less than 1 MeV. The Inverse Cyclotron Converter has a maximum projected efficiency of 90%. [19] [20] [21] [23] [24]

X-ray photoelectric converter

A significant amount of the energy released by fusion reactions is composed of electromagnetic radiation, essentially X-rays due to Bremsstrahlung. Those X-rays can not be converted into electric power with the various electrostatic and magnetic direct energy converters listed above, and their energy is lost.

Whereas more classical thermal conversion has been considered with the use of a radiation/boiler/energy exchanger where the X-ray energy is absorbed by a working fluid at temperatures of several thousand degrees, [25] more recent research done by companies developing nuclear aneutronic fusion reactors, like Lawrenceville Plasma Physics (LPP) with the Dense Plasma Focus, and Tri Alpha Energy, Inc. with the Colliding Beam Fusion Reactor (CBFR), plan to harness the photoelectric and Auger effects to recover energy carried by X-rays and other high-energy photons. Those photoelectric converters are composed of X-ray absorber and electron collector sheets nested concentrically in an onion-like array. Indeed, since X-rays can go through far greater thickness of material than electrons can, many layers are needed to absorb most of the X-rays. LPP announces an overall efficiency of 81% for the photoelectric conversion scheme. [26] [27]

Direct energy conversion from fission products

In the early 2000s, research was undertaken by Sandia National Laboratories, Los Alamos National Laboratory, The University of Florida, Texas A&M University and General Atomics to use direct conversion to extract energy from fission reactions, essentially, attempting to extract energy from the linear motion of charged particles coming off a fission reaction. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Nuclear fusion</span> Process of combining atomic nuclei

Nuclear fusion is a reaction in which two or more atomic nuclei, usually deuterium and tritium, combine to form one or more different atomic nuclei and subatomic particles. The difference in mass between the reactants and products is manifested as either the release or absorption of energy. This difference in mass arises due to the difference in nuclear binding energy between the atomic nuclei before and after the reaction. Nuclear fusion is the process that powers active or main-sequence stars and other high-magnitude stars, where large amounts of energy are released.

<span class="mw-page-title-main">Tokamak</span> Magnetic confinement device used to produce thermonuclear fusion power

A tokamak is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being developed to produce controlled thermonuclear fusion power. As of 2016, it was the leading candidate for a practical fusion reactor. The word "tokamak" is derived from a Russian acronym meaning "toroidal chamber with magnetic coils".

<span class="mw-page-title-main">Fusion rocket</span> Rocket driven by nuclear fusion power

A fusion rocket is a theoretical design for a rocket driven by fusion propulsion that could provide efficient and sustained acceleration in space without the need to carry a large fuel supply. The design requires fusion power technology beyond current capabilities, and much larger and more complex rockets.

<span class="mw-page-title-main">Inertial confinement fusion</span> Branch of fusion energy research

Inertial confinement fusion (ICF) is a fusion energy process that initiates nuclear fusion reactions by compressing and heating targets filled with fuel. The targets are small pellets, typically containing deuterium (2H) and tritium (3H).

<span class="mw-page-title-main">Fusor</span> An apparatus to create nuclear fusion

A fusor is a device that uses an electric field to heat ions to a temperature in which they undergo nuclear fusion. The machine induces a potential difference between two metal cages, inside a vacuum. Positive ions fall down this voltage drop, building up speed. If they collide in the center, they can fuse. This is one kind of an inertial electrostatic confinement device – a branch of fusion research.

<span class="mw-page-title-main">Fusion power</span> Electricity generation through nuclear fusion

Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices designed to harness this energy are known as fusion reactors. Research into fusion reactors began in the 1940s, but as of 2024, no device has reached net power, although net positive reactions have been achieved.

This timeline of nuclear fusion is an incomplete chronological summary of significant events in the study and use of nuclear fusion.

<span class="mw-page-title-main">Inertial electrostatic confinement</span> Fusion power research concept

Inertial electrostatic confinement, or IEC, is a class of fusion power devices that use electric fields to confine the plasma rather than the more common approach using magnetic fields found in magnetic confinement fusion (MCF) designs. Most IEC devices directly accelerate their fuel to fusion conditions, thereby avoiding energy losses seen during the longer heating stages of MCF devices. In theory, this makes them more suitable for using alternative aneutronic fusion fuels, which offer a number of major practical benefits and makes IEC devices one of the more widely studied approaches to fusion.

A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply to neutralize the electron space charge.

<span class="mw-page-title-main">Aneutronic fusion</span> Form of fusion power

Aneutronic fusion is any form of fusion power in which very little of the energy released is carried by neutrons. While the lowest-threshold nuclear fusion reactions release up to 80% of their energy in the form of neutrons, aneutronic reactions release energy in the form of charged particles, typically protons or alpha particles. Successful aneutronic fusion would greatly reduce problems associated with neutron radiation such as damaging ionizing radiation, neutron activation, reactor maintenance, and requirements for biological shielding, remote handling and safety.

<span class="mw-page-title-main">Field-reversed configuration</span> Magnetic confinement fusion reactor

A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring.

Neutral-beam injection (NBI) is one method used to heat plasma inside a fusion device consisting in a beam of high-energy neutral particles that can enter the magnetic confinement field. When these neutral particles are ionized by collision with the plasma particles, they are kept in the plasma by the confining magnetic field and can transfer most of their energy by further collisions with the plasma. By tangential injection in the torus, neutral beams also provide momentum to the plasma and current drive, one essential feature for long pulses of burning plasmas. Neutral-beam injection is a flexible and reliable technique, which has been the main heating system on a large variety of fusion devices. To date, all NBI systems were based on positive precursor ion beams. In the 1990s there has been impressive progress in negative ion sources and accelerators with the construction of multi-megawatt negative-ion-based NBI systems at LHD (H0, 180 keV) and JT-60U (D0, 500 keV). The NBI designed for ITER is a substantial challenge (D0, 1 MeV, 40 A) and a prototype is being constructed to optimize its performance in view of the ITER future operations. Other ways to heat plasma for nuclear fusion include RF heating, electron cyclotron resonance heating (ECRH), ion cyclotron resonance heating (ICRH), and lower hybrid resonance heating (LH).

Similar to how the fission-fragment rocket produces thrust, a fission fragment reactor is a nuclear reactor that generates electricity by decelerating an ion beam of fission byproducts instead of using nuclear reactions to generate heat. By doing so, it bypasses the Carnot cycle and can achieve efficiencies of up to 90% instead of 40-45% attainable by efficient turbine-driven thermal reactors. The fission fragment ion beam would be passed through a magnetohydrodynamic generator to produce electricity.

The polywell is a proposed design for a fusion reactor using an electric and magnetic field to heat ions to fusion conditions.

TAE Technologies, formerly Tri Alpha Energy, is an American company based in Foothill Ranch, California developing aneutronic fusion power. The company's design relies on an advanced beam-driven field-reversed configuration (FRC), which combines features from accelerator physics and other fusion concepts in a unique fashion, and is optimized for hydrogen-boron fuel, also known as proton-boron and p-B11. It regularly publishes theoretical and experimental results in academic journals with hundreds of publications and posters at scientific conferences and in a research library hosting these articles on its website. TAE has developed five generations of original fusion platforms with a sixth currently in development. It aims to manufacture a prototype commercial fusion reactor by 2030.

Norman Rostoker was a Canadian plasma physicist known for being a pioneer in developing clean plasma-based fusion energy. He co-founded TAE Technologies in 1998 and held 27 U.S. Patents on plasma-based fusion accelerators.

<span class="mw-page-title-main">ITER Neutral Beam Test Facility</span>

The ITER Neutral Beam Test Facility is a part of the International Thermonuclear Experimental Reactor (ITER) in Padova, Veneto, Italy. The facility will host the full-scale prototype of the reactor's neutral beam injector, MITICA, and a smaller prototype of its ion source, SPIDER. SPIDER started its operation in June 2018. SPIDER will be used to optimize the ion beam source, to optimize the use of caesium vapor, and to verify the uniformity of the extracted ion beam also during long pulses.

Colliding beam fusion (CBF), or colliding beam fusion reactor (CBFR), is a class of fusion power concepts that are based on two or more intersecting beams of fusion fuel ions that are independently accelerated to fusion energies using a variety of particle accelerator designs or other means. One of the beams may be replaced by a static target, in which case the approach is termed accelerator based fusion or beam-target fusion, but the physics is the same as colliding beams.

Heavy ion fusion is a fusion energy concept that uses a stream of high-energy ions from a particle accelerator to rapidly heat and compress a small pellet of fusion fuel. It is a subclass of the larger inertial confinement fusion (ICF) approach, replacing the more typical laser systems with an accelerator.

The history of nuclear fusion began early in the 20th century as an inquiry into how stars powered themselves and expanded to incorporate a broad inquiry into the nature of matter and energy, as potential applications expanded to include warfare, energy production and rocket propulsion.

References

  1. Post, Richard F. (November 1969). "Direct Conversion of Thermal Energy of High Temperature Plasma". Bulletin of the American Physical Society. 14 (11): 1052.
  2. 1 2 Post, Richard F. (September 1969). Mirror Systems: Fuel Cycles, Loss Reduction and Energy Recovery (PDF). BNES Nuclear Fusion Reactor Conference. Culham Centre for Fusion Energy, Oxfordshire, U.K.: British Nuclear Energy Society. pp. 87–111. Archived from the original (PDF) on 2015-06-23. Retrieved 2014-06-22.
  3. Moir, R. W.; Barr, W. L. (1973). ""Venetian-blind" direct energy converter for fusion reactors" (PDF). Nuclear Fusion. 13: 35–45. doi:10.1088/0029-5515/13/1/005. S2CID   54532893. Archived from the original (PDF) on 2016-03-20. Retrieved 2015-08-29.
  4. 1 2 Barr, W. L.; Burleigh, R. J.; Dexter, W. L.; Moir, R. W.; Smith, R. R. (1974). "A preliminary engineering design of a "Venetian blind" direct energy converter for fusion reactors" (PDF). IEEE Transactions on Plasma Science. 2 (2): 71. Bibcode:1974ITPS....2...71B. doi:10.1109/TPS.1974.6593737. Archived from the original (PDF) on 2016-04-23. Retrieved 2015-08-29.
  5. 1 2 Moir, R. W.; Barr, W. L.; Miley, G. H. (1974). "Surface requirements for electrostatic direct energy converters" (PDF). Journal of Nuclear Materials. 53: 86–96. Bibcode:1974JNuM...53...86M. doi:10.1016/0022-3115(74)90225-6. Archived from the original (PDF) on 2016-03-05. Retrieved 2015-08-29.
  6. Morris, Jeff. "In Memoriam." (n.d.): n. pag. Rpt. in Newsline. 19th ed. Vol. 29. Livermore: Lawrence Livermore National Laboratory, 2004. 2. Print.
  7. Barr, William L.; Doggett, James N.; Hamilton, Gordon W.; Kinney, John; Moir, Ralph W. (25–28 October 1977). Engineering of Beam Direct Conversion for a 120kV, 1MW Ion Beam (PDF). 7th Symposium on Engineering Problems of Fusion Research. Knoxville, Tennessee. Archived from the original (PDF) on 22 July 2016. Retrieved 23 June 2014.
  8. Barr, W. L.; Moir, R. W.; Hamilton, G. W. (1982). "Experimental results from a beam direct converter at 100 kV". Journal of Fusion Energy. 2 (2): 131. Bibcode:1982JFuE....2..131B. doi:10.1007/BF01054580. S2CID   120604056.
  9. 1 2 Rosenbluth, M. N.; Hinton, F. L. (1994). "Generic issues for direct conversion of fusion energy from alternative fuels". Plasma Physics and Controlled Fusion. 36 (8): 1255. Bibcode:1994PPCF...36.1255R. doi:10.1088/0741-3335/36/8/003. S2CID   250805049.
  10. Barr, William L.; Moir, Ralph W. (January 1983). "Test results on plasma direct converters". Nuclear Technology - Fusion. 3 (1). American Nuclear Society: 98–111. doi:10.13182/FST83-A20820. ISSN   0272-3921.
  11. Barr, W. L.; Howard, B. C.; Moir, R. W. (1977). "Computer Simulation of the Periodic Electrostatic Focusing Converter" (PDF). IEEE Transactions on Plasma Science. 5 (4): 248. Bibcode:1977ITPS....5..248B. doi:10.1109/TPS.1977.4317060. S2CID   12552059. Archived from the original (PDF) on 2016-03-04. Retrieved 2015-08-29.
  12. Smith, Bobby H.; Burleigh, Richard; Dexter, Warren L.; Reginato, Lewis L. (20–22 November 1972). An Engineering Study of the Electrical Design of a 1000-Megawatt Direct Converter for Mirror Reactors. Texas Symposium on Technology of Controlled Thermonuclear Fusion Experiments and the Engineering Aspects of Fusion Reactors. Austin, Texas: U.S. Atomic Energy Commission.
  13. Sutton, George W.; Sherman, Arthur (July 2006). Engineering Magnetohydrodynamics. Dover Civil and Mechanical Engineering. Dover Publications. ISBN   978-0486450322.
  14. Artsimovich, L. A. (1963). Управляемые термоядерные реакции[Controlled Thermonuclear Reactions] (in Russian) (2nd ed.). Moscow: Fizmatgiz.
  15. Haught, A. F. (1970). "Magnetic Field Confinement of Laser Irradiated Solid Particle Plasmas". Physics of Fluids. 13 (11): 2842. Bibcode:1970PhFl...13.2842H. doi:10.1063/1.1692870.
  16. Moir, Ralph W. (April 1977). "Chapter 5: Direct Energy Conversion in Fusion Reactors" (PDF). In Considine, Douglas M. (ed.). Energy Technology Handbook. NY: McGraw-Hill. pp.  150–154. ISBN   978-0070124301.
  17. Oliphant, T. A.; Ribe, F. L.; Coultas, T. A. (1973). "Direct conversion of thermonuclear plasma energy by high magnetic compression and expansion". Nuclear Fusion. 13 (4): 529. doi:10.1088/0029-5515/13/4/006. S2CID   121133314.
  18. Momota, Hiromu; Ishida, Akio; Kohzaki, Yasuji; Miley, George H.; Ohi, Shoichi; Ohnishi, Masami; Sato, Kunihiro; Steinhauer, Loren C.; Tomita, Yukihiro; Tuszewski, Michel (July 1992). "Conceptual Design of the D-3He Reactor Artemis" (PDF). Fusion Science and Technology. 21 (4): 2307–2323. doi:10.13182/FST92-A29724.
  19. 1 2 Rostoker, N.; Binderbauer, M. W.; Monkhorst, H. J. (1997). "Colliding Beam Fusion Reactor" (PDF). Science. 278 (5342): 1419–22. Bibcode:1997Sci...278.1419R. doi:10.1126/science.278.5342.1419. PMID   9367946. Archived from the original (PDF) on December 20, 2005.
  20. 1 2 USpatent 6850011,Monkhorst, Hendrik J.&Rostoker, Norman,"Controlled fusion in a field reversed configuration and direct energy conversion",issued 2005-02-01, assigned to The Regents Of The University Of Californiaand University Of Florida Research Foundation
  21. 1 2 WOapplication 2006096772,Binderbauer, Michl; Bystritskii, Vitaly& Rostoker, Normanet al.,"Plasma electric generation system",published 2006-12-28, assigned to Binderbauer, Michland Vitaly Bystritskii, Norman Rostoker, Franck Wessel
  22. Bloch, F.; Jeffries, C. (1950). "A Direct Determination of the Magnetic Moment of the Proton in Nuclear Magnetons". Physical Review. 80 (2): 305. Bibcode:1950PhRv...80..305B. doi:10.1103/PhysRev.80.305.
  23. Yoshikawa, K.; Noma, T.; Yamamoto, Y. (May 1991). "Direct-Energy Conversion from High-Energy Ions Through Interaction with Electromagnetic Fields". Fusion Science and Technology. 19 (3P2A). American Nuclear Society: 870–875. doi:10.13182/FST91-A29454.[ permanent dead link ]
  24. Rostoker, N.; Binderbauer, M.; Monkhorst, H. J. (1997). Office of Naval Research Reports (Technical report).
  25. Taussig, Robert T. (April 1977). High thermal efficiency, radiation-based advanced fusion reactors. Palo Alto, CA: Electric Power Research Institute. OCLC   123362448.
  26. USpatent 7482607,Lerner, Eric J.&Blake, Aaron,"Method and apparatus for producing X-rays, ion beams and nuclear fusion energy",issued 2009-01-27, assigned to Lawrenceville Plasma Physics, Inc.
  27. USapplication 2013125963,Binderbauer, Michl&Tajima, Toshiki,"Conversion of high-energy photons into electricity",published 2013-05-23, assigned to Tri Alpha Energy, Inc.
  28. l.c. Brown (2002). "Direct Energy Conversion Fission Reactor Annual Report for the Period August 15, 2000 Through September 30, 2001". doi:10.2172/805252.{{cite journal}}: Cite journal requires |journal= (help)