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Summary

The author proposes a new method for conversion of solar energy into electricity using natural convection in an open cycle. A convergent nozzle made of glass or other transparent material is arranged vertically with a modest gap between the open base and ground level. A solar absorber abundantly perforated and several layers thick or of metallic honeycomb structure is arranged in the lower levels but above the base of the nozzle. The elaborate solar absorber structure is required to provide rapid heat transfer. Solar energy absorbed warms air in its neighbourhood which rises because of its buoyancy drawing in ambient air to replace. As the air flows through the nozzle it accelerates because of the narrowing/constriction. Heat energy acquired from the absorber is converted into the kinetic energy of flow. A wind turbine placed in the throat of the nozzle converts flow kinetic energy into electricity. A critical height is calculated for given nozzle dimensions where all of the solar energy absorbed is converted into kinetic energy. This could allow the conversion of solar energy into electricity with high efficiency. A prototype solar nozzle is proposed of base diameter 10 metres, throat diameter 1 metre, and height 10 metres. Calculation indicates that at maximum UK summer insolation this could give an electricity output of up to 59 kilowatts. Solar farms could be built of such modular units. Larger prototypes with capacity up to 5 Megawatts are described. An alternative configuration using incoming air into a nozzle pre solar absorber is also described which would be more compact and have higher power density. In all cases the systems proposed are driven simply by the buoyancy of warm air. All the proposals are theoretical and the author asks others to build, test, evaluate and develop the ideas.

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