Design and optimization of lab-scale sensible heat storage prototype for solar thermal power plant application

• Performance analyses of the sensible heat storage prototypes are presented.
• Concrete, cast iron and cast steel are considered as storage materials.
• Number of charging tubes is optimized for 10 MJ capacity based on charging time.
• Incorporation of fins on the charging tube reduces the charging time by 41.4%.
• Numerically predicted results match well with the data reported in literature.

This paper deals with the numerical investigation of transient behavior and thermal storage capability of a sensible heat storage unit designed for storing heat in the temperature range of 523–673 K. A heat storage unit of cylindrical configuration with embedded charging tubes has been designed employing three storage materials viz., concrete, cast steel and cast iron. To investigate their heat storage characteristics, a finite element based 3-D mathematical model has been developed using COMSOL Multiphysics 4.2. The number of embedded charging tubes in the bed has been optimized based on the charging time of storage bed. Numerically predicted results match closely with the data reported in the literature. Performances of the thermal storage bed of capacity of 10 MJ (including charging time, energy storage rate, charging energy efficiency) have been evaluated for the selected three storage materials. The parametric studies are carried out by varying the number of fins on the charging tubes and the heat transfer fluid flow rate. The reductions in charging time are 35.48% (charging time 1307 s) for four fins case and 41.41% (charging time 1187 s) for six fins case as compared to concrete bed with plain charging tubes. For cast iron and cast steel storage beds, the increase in velocity of heat transfer fluid causes the reduction in charging time by the almost same factor while this effect in concrete is less because of comparatively lower thermal conductivity and higher heat capacity.