Wave propagation and thermodynamic losses in packed-bed thermal reservoirs for energy storage

Abstract

This paper presents a numerical and theoretical analysis of thermal wave propagation in packed bed thermal reservoirs for energy storage applications. In such reservoirs, the range of temperatures encountered is usually such that the solid storage medium will exhibit significant changes in specific heat capacity. This in turn results in non--linear wave propagation and may lead to the formation of shock--like thermal fronts. Such effects have an impact on the exergetic losses due to irreversible heat transfer, and should be taken into account during the design and optimisation of the reservoirs. In the present paper, the emphasis is on thermal losses due to irreversible heat transfer. Frictional (pressure) losses and heat leakage between the storage medium and the environment are also important but are not considered here. The implications of the results for storage material, and particle size are discussed briefly in the context of loss minimisation. Keywords: energy storage, irreversible heat transfer, thermal reservoirs, exergetic loss. NOMENCLATURE

The influence of gas–solid reaction kinetics in models of thermochemical heat storage under monotonic and cyclic loading

“…partial loading and unloading of the storage can occur which is likely associated with consequences for material usage and fatigue. Furthermore, consecutive cycles are known to influence each other, even in chemically inert systems [18]. As far as we are aware, no modelling study has been performed that focusses on the conditions inside the reactor under cyclic temperature and partial vapour pressure loading using a fully coupled thermohydro-chemical model with local thermal nonequilibrium as done in this study.…”

Adiabatic Compressed Air Energy Storage with packed bed thermal energy storage

“…Desrues et al [32] analyses a PTES system which uses electricity to pump heat between packed beds, before using a heat engine to produce electricity at a later time. White et al [33] undertakes a detailed theoretical analysis of thermal front propagation in packed beds for energy storage. Although the use of packed beds for heat storage in A-CAES has been suggested, a detailed analysis of this type of system is hard to find in the literature.…”

A comparative study of liquid, solid and hybrid adiabatic compressed air energy storage systems

“…Materials selection essentially becomes finding the substance with the largest volumetric heat capacity because cost tends to be dominated by the pressure vessel. On the basis of work reported in [13], magnetite (Fe 3 O 4 ) has been used as the solid storage medium for the analysis presented here, and the maximum temperature is set at 600°C. For liquid TES, mineral oil, molten salt and water are the most widely used thermal fluids.…”

“…The model used here is that described in Refs. [13,18,19] and is based on the well-established Schumann model. Although the numerical method employed takes account of additional phenomena (such as unsteady terms for the gas phase and temperature-dependent heat capacities) the propagation of thermal fronts within the packed bed is described to a good approximation by:…”