Patent GB-1103084-A (GB)
Title: Generator of electrical energy
IPC: H01L35/06
Filed: 1965-11-04
Abstract: 1,103,084. Thermoelectric generators. NUCLEAR MATERIALS & EQUIPMENT CORPORATION. 4 Nov., 1965 [3 Dec., 1964], No. 46741/65. Headkng HlK. A thermoelectric generator comprises two thermoelectric assemblies in cascade, the thermoelements of the assemblies being of different materials. As shown, Fig. 2, the upper thermoelectric assembly 11 comprises a plurality of N and P- type silicon-germanium thermoelements THN ,  THP electrically connected in series by platinum straps (S2 to S8) and thermally connected in parallel between a heat source plate HSO and a heat transfer structure 16. The lower thermoelectric assembly 13 comprises a plurality of N and P-type lead telluride thermoelements, each of which comprises two sections THN1- THN2, THP1-THP2 having different characteristics. The elements of assembly 13 are electrically connected in series by copper straps (S10 to S23) and thermally connected in parallel between heat transfer structure 16 and a heat sink plate HSI. The lower N-type elements THN2 are provided with internal holes 15 which match their electrical characteristics to those of elements THN1. The elements of assembly 11 have tungsten caps 80, 81 sprayed or vapour-deposited on their ends. The upper connecting straps are brazed directly to end caps 80, while copper shoes 111 are inserted between the lower connecting straps and end caps 81. The upper connecting straps are thermally connected to plate HSO by zirconia strips 103 mounted between tungsten compensating strips 101, 105. The lower connecting straps are thermally connected to heat transfer structure 16 by layers of silicon-based ceramic glaze applied to the straps and to copper compensating strips 115. The elements of assembly 13 have iron caps 83 sprayed on their ends and are provided with copper shoes 121, 123 which are pressed against cap 83 but are not bonded. The connecting straps are brazed to shoes 121, 123 and are insulated from copper compensating strips 115, 131 by layers of glaze 133. Assembly 13 is electrically connected in series with assembly 11 by U-shaped connecting straps S1 (S9) and external connections are made to the arrangement by terminal structures T1, (T2) which engage spring contacts 71. The heat transfer structure 16 comprises a vacuum-tight container 17 having flexible stainless steel walls 19 sealed to a peripheral support 21. A plurality of springs 27 are mounted inside container 17, each spring 27 comprising four turns of a mesh or cloth of fine stainless steel wire. A metal such as caesium (or gallium) is inserted in container 17 which is then evacuated and sealed. The caesium is liquid at the temperature of the hot junction of assembly 13 and gaseous at the temperature of the cold junction of assembly 11. Structure 16 therefore operates as a single chamber evaporation condensation heat transfer system, the liquid caesium being carried to the upper wall 19 by the capillary action of springs 27. The two assemblies 11, 13 and structure 16 are enclosed by a housing comprising thin walls 41, 43 of an iron-chromium-aluminium-cobalt alloy welded between plates HSO, HSI and peripheral plates 47, 53 and brazed to centre support plates 45, 51 which are welded together. Plates HSO, HSI, 45, 47, 51 and 53 may all be of the same alloy as the walls 41, 43. The housing may be evacuated or filled with a 95/5 mixture of argon and hydrogen. The elements of assembly 13 may be of tin telluride instead of lead telluride, and the connecting straps of assembly 11 may be of niobium-coated copper instead of platinum. The constituents of the alloys used for brazing various parts together are specified. The thermoelectric elements are insulated from one another by a coating which may be of zirconia for assembly 11 and a ceramic glaze for assembly 13. The heat source for the generator may be a radio-active mass or a nuclear reactor.