GB887202A - Solar thermoelectric generators - Google Patents

Abstract

887,202. Semi-conductor devices. AMERICAN MACHINE & FOUNDRY CO. March 9, 1960 [March 9, 1959], No. 8307/60. Class 37. A solar thermo-electric generator has a number of thermocouples mounted in a housing with a window through which radiation enters, a cooled junction being adjacent the window and the hot junction, a flat plate receiver being spaced from the window. As shown, Fig. 1, solar radiation enters the housing through the window 6 which has a high transmission in the visible and near infra-red spectrum and a low transmission of longer wavelength and is received on a plate 5 which may be of metal to increase heat absorption. This plate is a poor reflector for wavelengths below α microns and a good reflector and poor emitter for wavelengths above. The window is spaced from the plate by rigid sides of poorly heat-conducting material, for example wood. The sides are sealed with respect to the receiver and window by gaskets, low-melting-point solder, or an organic polymer cement and the window may be doubleglazed with a space between the plates evacuated or filled with an inert gas. Each thermal element is a cylindrical ingot of bismuth-tellurium alloy and the element 13 is a metal strip such as copper or aluminium. The couples are connected in series by soldered contacts, but pressure contacts may be used. The hot junctions are in contact with the receiver plate but are spaced from it if it is electrically conducting by flakes of mica or polytetrafluorethylene. Fig. 4 shows an arrangement in which the thermal elements 19, 20 are of a bismuth tellurium alloy with traces of other elements to render them electrically positive or negative joined by copper strips 21, 22. In the arrangement of Fig. 5 (not shown), the whole housing is heat-insulated except the window and a heat sink is provided below the receiver plate. This sink may consist of a reservoir of water, a saline solution or a gravel bed. The space beneath the cover may be evacuated in which case the thermocouples may act as supports, this being a convenient way of making pressure contacts. Further thermoelectric materials referred to as suitable are the heavy metal oxides and sulphides, for example ZnO, PbS and zinc-antimony and bismuth-antimony alloys.