Performance of a Packed Bed Solar Energy Stoarge System with Concrete Spheres as Storage Material

ABSTRACT

A storage system constitutes an important component of the solar energy utilization system. Packed bed generally represents the most suitable energy storage unit for air based solar energy systems. Packing of small sized particles requires a large pressure drop for uniform flow of hot air through the bed, which causes a large amount of energy consumption to propel hot air through the bed. An experimental study on a packed bed solar energy storage system has been conducted and reported in this paper. Concrete spheres of relatively large size (60 mm diameter) have been used as the storage material in order to reduce the energy consumption. The sphericity for the spherical shaped element is equal to one. The storage elements are placed uniformly in different arrangements to obtain four different void fraction values. The effect of system and operating parameters on the heat transfer and pressure drop characteristics has been investigated. It is concluded that the Nusselt number increases with an increase in the Reynolds number and it decreases with an increase in the value of void fraction, whereas the friction factor decreases with an increase in Reynolds number and it also decreases with an increase in void fraction.

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