Techno-economic optimization of a packed-bed for utility-scale energy storage

Abstract

The optimization of a packed bed for utility-scale applications is presented in this paper. The effects that particle size, aspect ratio and storage mass have on the roundtrip exergy efficiency of the store are thoroughly analysed. The paper seeks to provide a clear insight of what ranges of values for the aforementioned design parameters are adequate to consider when designing a grid-scale packed bed. Simulations were carried out using a one-dimensional model that accounts for temperature-dependent properties and self-discharge losses. The assumed operating temperature range for the packed bed is 290-823 K, which is typical of CSP plants and CAES systems. A 24-hour work cycle (12 hr charge / 12 hr discharge) with variable power (10 MW peak) and a total energy storage requirement of 79.4 MWhth has been considered for the study. It has been found that exergy losses are minimized if a configuration based on an aspect ratio between 0.5 and 0.8 is adopted and the size of the rocks is finely tuned for the specific shape of container. In this work-unlike similar studies-a cost-benefit analysis has been carried out, which indicates that increasing the thermal storage mass leads to a considerable increase in efficiency. A mass overrating of 50% yields the lowest levelized cost of storage for the economic scenario considered. The optimum design obtained from the optimization process has an aspect ratio of 0.6, a particle size of 4mm and a mass overrating factor of 1.5. This packed bed attained a roundtrip exergy efficiency of 98.24 %

Techno-economic analysis of thermal energy storage systems

“…Cárdenas et al 38 investigated that exergy losses are minimized for an aspect ratio between 0.5 and 0.8. Also, it was predicted that the increase in the mass of storage media enhances the storage efficiency of the packed bed.…”

A sign-preserving filter for signal decomposition

“…Each combination will produce two load profiles ( b and c ) which will be handled by two different packed beds. The design of each packed bed will be optimized for its working load, following the procedure described in Cárdenas et al 26 The optimum signal split is the one that produces the lowest total exergy losses.…”

“…Ca´rdenas et al 26 carried out a techno-economic optimization of a utility-scale packed bed. In the study, the authors analyze comprehensively the aforementioned trade-offs.…”

“…The parametric analysis carried out with v 1 in Ca´rdenas et al 26 was repeated with the different work cycles v 2 , v 4 and so on. For every one of the load profiles, several different values of a and sizes of rocks were evaluated to find the optimum design in terms of performance (lowest exergy losses).…”

Numerical Model of Lab-Scale Packed-Bed Thermal Energy Storage System

“…The results showed that at least 98% efficiency could be achieved with 30 mm rock diameter and 0.6 m insulation layer. Cardenas et al [4] evaluated packed-bed TES system by developing temperature dependent 1-dimensional 2-phase model. Packed bed with 4 mm rock diameter and 0.6 aspect ratio showed higher efficiency.…”