Optimal design for sensible thermal energy storage tank using natural solid materials for a parabolic trough power plant

This paper presents numerical investigation of transient behavior and thermal storage capability of a sensible heat storage (SHS) unit designed for storing heat in the temperature range of 523-673 K. The objective of this study is to assess the potential of using two candidate materials as energy storage media found in Jordan. The thermal performance of using these materials in SHS tank is compared against concrete bed. A heat storage unit of cylindrical configuration with embedded charging tubes has been designed. To investigate their heat storage characteristics, a finite element based 3-D mathematical model has been developed using COMSOL Multiphysics 5.1. Numerically predicted results match closely with the data reported in the literature. Performances of the thermal storage bed of capacity of 136.7 MW in 3 h (including charging time, energy storage rate, charging energy efficiency) have been evaluated for the selected three storage materials. In order to optimize the design of energy storage tank, parametric studies are carried out by varying the number of the charging tubes, diameter of charging tubes, fins effectiveness, and storage bed diameter to its height. Simulations results showed that overall thermal performance of these materials using optimal design are satisfactory considering the problems associated with molten salt and concrete bed. More specifically, Dead Sea salt, concrete bed and Basalt rocks are more economically attractive relative to molten salt plant because they eliminate the extra cost associated with freeze protection, no pressurizing problem, no corrosion. Finally, natural stones can operate at higher temperature and do not suffer from cracking due to cyclic charging and discharging.