Procédé et appareil pour la conversion directe d'énergie thermique en énergie électrique

854,036. Discharge tubes. GENERAL ELECTRIC CO. Nov. 21, 1958 [Nov. 25, 1957], No. 37553/58. Class 39(1). In a method of converting thermal energy to electrical energy with a device including a pair of electrode surfaces having substantially different work functions and supported in closely spaced and insulated relation within a vacuum-tight enclosure, heat energy 14 is supplied to the electrode 1 having the higher work function to produce a copious supply of electrons, the electrode 2 having the lower work function is maintained at a temperature several hundred degrees Kelvin e.g. 700‹K. lower than electrode 1, and positive ions are supplied to the space between the electrodes to substantially neutralize the space charge therebetween. As shown a reservoir 7 of readily vapourizable metal, caesium, potassium or rubidium, is located opposite the inlet 10 to the cooling jacket 8. The metal vapour provides a complete coating on electrode 2, of oxidised silver molybdenum, nickel, tantalum, iron or stainless steel, and a partial coating on electrode 1 of molybdenum, tungsten, tantalum or nickel, whereby the work function of electrode 2 is less than that of electrode 1. The positive ions may be produced by the uncoated portion of the emitted electrode or by means of a tungsten filament, heated with direct current, and extending across the diameter of the device between electrodes 1 and 2, and spaced a distance of À025 to À05 mm. from each. However, if desired the positive ions may be injected into the device from an external source. The heat energy required to maintain electrode 1 at a temperature of 1800‹K. may be derived from a nuclear reactor or solar energy system. In an alternative arrangement an inner cylindrical electrode 19, Fig. 4, may be heated by nuclear reaction using uranium oxide fuel or may be open-ended, the heating medium being passed therethrough.