Direct Energy

Direct Energy Conversion from Fusion Power

Direct energy conversion is the conversion of charged particle kinetic energy to potential energy. Typically this is done by decelerating and collecting the charged particles on high-voltage plates.

The concept of direct energy conversion was first recognized in 1959 by G.I. Budker, but it wasn’t until 1967 when Richard F. Post described a high efficiency multi-plate collector that serious study was given to it. Extensive direct energy conversion engineering and economic studies were subsequently made by researchers at Lawrence Livermore Laboratory in the 1970s.

  • “Mirror Systems: Fuel Cycles, Loss Reduction and Energy Recovery,” Richard F. Post, British Nuclear Energy Society, Nuclear Fusion Reactor Conference at Culham Laboratory, September 1969, pp. 87-111.

Direct energy conversion is particularly attractive for aneutronic fusion power plants since over 99% of its power are released as charged particles. Efficiencies of up to 80% may be achieved using direct energy conversion, in contrast to 40% efficiencies from conventional steam-turbine power plant designs.

  • “’Direct Energy Conversion in Fusion Reactors” , Ralph W. Moir; Energy Technology Handbook, McGraw Hill, 1977, pp. 5-150 to 5-154

Electrostatic direct energy converters are linear accelerators run backwards, e.g. fast ions enter the “exit” of the accelerator, are decelerated by retarding electric fields, and collected on high-voltage electrodes forming the positive terminal of the direct energy converter power source.

The Venetian Blind direct energy converter concept developed at Lawrence Livermore Laboratory uses ribbon-like surfaces that 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. They then see opaque surfaces and are caught. In this manner, ions are sorted by energy with high-energy ions being caught on high-potential electrodes.

  • “’Venetian Blind’ Direct Energy Conversion for Fusion Reactors, Ralph W. Moir, William L Barr; Nuclear Fusion 13, January 1973
  • “’A Preliminary Engineering Design of a ‘Venetian Blind’ Direct Energy Converter for a Fusion Reactor” , William L Barr, Richard Burleigh, Warren L. Dexter, Ralph W. Moir, Richard R. Smith; IEEE Transactions on Plasma Science, Volume 2, Issue 2, June 1974, pp. 71-92
  • “Surface Requirements for Electrostatic Direct Energy Converters,” Ralph W. Moir, William L. Barr, and George H. Miley; Journal of Nuclear Materials, 53 (1974) pp. 86-96, doi:10.1016/0022-3115(74)90225-6
  • “’Engineering of Beam Direct Conversion for a 120-kV, 1-MW Ion Beam” , William L Barr, James N. Doggett, John D. Kinney, Ralph W. Moir; Proceedings of the 7th Symposium on Engineering Problems of Fusion Research, October 25-28 1977
  • “Computer Simulation of the Periodic Electrostatic Focusing Converter,” William L. Barr, Barry C. Howard, Ralph W. Moir; IEEE Transactions on Plasma Sciences, December 1977, pp. 248-258, doi:10.1109/TPS.1977.4317060
  • “Direct Energy Conversion Beam Dump for a 1.6 MeV Neutral Beam for the International Thermonuclear Experimental Reactor (ITER),” Ralph Moir; Fusion Technology, Volume 25, March 1994, pp. 129-136