Solar Energy Conversion by Thermal Destruction of Conductivity

A method is proposed for converting solar radiation directly to electrical energy in space by utilizing the change of state of a superconductor. Apparatus is described whereby intermittent exposure to a concentrated beam of solar radiation causes a magnetic shield to fluctuate between the superconductive state (zero permeability) and the normal state (unity permeability) with resultant flux changes converted to electrical energy by conventional induction methods. A thermal embodiment of Lexis\u27s law, akin to the back torque of a conventional generator or the counter current in the primary of a transformer, is postulated. Such a reaction is demanded by energy conservation principles, although in the present case it can be exerted only against an input of purely thermal energy. In a heat engine working between heat quantities represented by intercepted solar flux at the upper limit and the black cold of space at the lower limit, a theoretical thermal efficiency in excess of 99% is possible. In order to realize this phenomenal efficiency in a heat engine with a radiator of practical size, a closed compound cycle is proposed in which a portion of the power output is used to drive a refrigerator. By compounding the cycle the net thermal efficiency is reduced but the effectiveness of the system remains unchanged, provided only that a part of the output of the converter be utilized in the cooling of other cryogenic devices such as superconductive delay lines, lasers, IR sensors etc., the balance being available for general purposes. The heat extracted from all cryogenic equipment, including the converter itself, can then be radiated away at a temperature high enough to benefit from the fourth power law. A practical form of the converter is described, with particular reference to the problem of eddy-current losses, which are unusually severe at very low temperatures