Buoyancy Driven Solar Engine



Warm air rises. In any air-filled configuration, open to the atmosphere, if part of the volume is heated, warm air will rise drawing ambient air from beneath to replace. If entry of air at the base of the configuration is restricted by a constriction/funnel/convergent nozzle, incoming air is accelerated by the geometric constraint. It may thus be possible to produce high air flow velocity using the buoyancy of warm air.

In this paper it is suggested that warm air from a solar absorber/collector flows via a warm air store into the atmosphere. This provides a suction force drawing ambient air from beneath into the absorber. Incoming air is channelled through a convergent nozzle where the narrower is the throat of the nozzle the higher is the air flow velocity. Calculations suggest that at UK maximum summer insolation an air flow velocity of 50 m/s can be achieved. If solar energy can be converted efficiently into the kinetic energy of air flow, this can be harnessed using an air/wind turbine to produce electricity.

No experimental work has been carried out. The author suggests a series of experiments that could validate the approach and describes possible working models. It is the author’s belief that the ‘buoyancy driven solar engine’ outlined will allow conversion of solar energy into electricity with over 50% efficiency and that it is amenable to large scale application.

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