TITLE:
Packed Bed Thermocline Thermal Energy Storage for Medium-Temperature Concentrating Solar Systems: Numerical and Experimental Study
AUTHORS:
Nikolaos Stathopoulos, Nikolaos Papadimitriou, Vassilis Belessiotis, Elias Papanicolaou
KEYWORDS:
Thermal Energy Storage, Packed Bed, Numerical, Model, Experimental
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.11 No.5,
May
31,
2023
ABSTRACT: Thermal Energy Storage is
becoming a necessary component of sustainable energy production systems as it
helps alleviate intrinsic limitations of Renewable Energy Sources, such as
intermittent use and mismatch between power demand and supply. This paper
discusses a packed bed thermocline tank as a thermal energy storage solution.
Firstly, this paper presents the development of a numerical model calculating
heat transfers within the tank, based on a discretization over several nodes
and the nodal formulation of the heat balance equation. The model considers a
filler material and a heat transferring fluid and uses the finite difference
method to calculate the temperature evolution of the two media across the tank.
The model was validated with two different packed bed systems from the
literature during a discharging process, presenting a good fit with the
experimental results. Secondly, the experimental packed bed is presented and
characterized for a charging cycle from ambient temperature to approximately
180?C. The charging experiment was accurately reproduced with the numerical
model requiring minimal computational time. Two additional charging modes were
simulated with different inlet HTF conditions:
constant temperature and varying temperature following the profile produced by
a thermal solar collector field. The temperature profiles obtained from the
three charging modes were analysed and compared to each other. The proposed
numerical and experimental tools will be used in future studies for a better
understanding of the design and operating conditions of packed bed thermal
energy storage systems.