Analysis of Heat Storage and Delivery of a Thermocline Tank Having Solid Filler Material

Abstract

Thermal storage has been considered as an important measure to extend the operation of a eoneentrated solar power plant by providing more eleetricity and meeting the peak demand of power in the time period from dusk to late night everyday, or even providing power on eloudy days. Diseussed in this paper is thermal energy storage in a thermoeline tank having a solid filler material. To provide more knowledge for designing and operating of sueh a thermoeline storage system, this paper firstly presents the application of method of characteristics for numerieally predicting the heat charging and discharging process in a paeked bed thermocline storage tank. Nondimensional analysis of governing equations and numerical solution schemes using the method of characteristics were presented. The numerical method proved to be very efficient, accurate; required minimal computations; and proved versatile in simulating various operational conditions for which analytical methods cannot always provide solutions. Available analytical solutions under .simple boundary and initial conditions were used to validate the numerical modeling and computation. A validation of the modeling by eomparing the simulation results to experimental test data from literature also confirmed the effectiveness of the model and the related numerieal solution method. Finally, design procedures using the numerical modeling tool were discussed and other issues related to operation of a thermoeline storage system were also studied.

Numerical analysis of charging and discharging performance of a thermal energy storage system with encapsulated phase change material

“…Researchers in the National Renewable Energy Laboratory (NREL) numerically modeled the packed-bed molten salt thermocline system in which the solid fillers were in the form of hexagonal rods or a honeycomb-like structure [7]. Using the adopted Schumann model [3], the performance of thermocline energy storage system, filled with rocks as filler material, was studied by Van Lew et al [8] and the effects of particle diameter, bed dimensions, fluid flow rate and the solid filler material on the dynamic performance of thermocline storage system were studied by H€ anchen et al [9].…”

Application of phase change materials for thermal energy storage in concentrated solar thermal power plants: A review to recent developments

“…Approaches of analytical solution assisted with numerical computation to the above equations have been well described in the work of Van Lew et al [140] for thermal storage with no melting, and the work of Tumilowicz et al [139] for the case with melting process.…”

Experimental and numerical investigation of combined sensible–latent heat for thermal energy storage at 575°C and above

“…This unit was designed for an air-based tubular receiver for a CSP trough system that can deliver air at 600°C and above (Good et al, 2013). Recently, rocks have been suggested as filler material for oil and molten salt tanks in order to increase the energy density and help create and maintain temperature stratification (Van Lew et al, 2011;Flueckiger et al, 2012;Valmiki et al, 2012). Packed beds of rocks using air as HTF finds application not only in CSP plants (Bader et al, 2011), but also in adiabatic compression-expansion cycles for electricity storage (Jakiel et al, 2007).…”