Sensible thermal energy storage in packed beds using supercritical CO2: A comparative study of tanks with steel-only and reinforced concrete walls

Abstract

Packed-bed thermal energy storage (PBTES) is an affordable option to store energy in concentrated solar power (CSP) plants, where supercritical carbon dioxide (s-CO${}_2$) can be the working fluid in Brayton cycles. Due to the elevated operating pressures required by the s-CO${}_2$ in the power block, the PBTES tanks require thick walls to operate safely, representing constructive and economic constraints for their applicability. Then, this work compares two constructive alternatives from a numerical standpoint: steel-only walls and reinforced concrete (RC) walls. The comparison of these wall materials considers their thermal performance and the levelized cost of storage (LCOS) for different tank configurations, a novelty from the perspective of comparing the performance of different wall materials for PBTES tanks. A fixed volume of $2660\text{m}{}^3$, required for $8\text{h}$ discharge in a $10\text{MW}$ CSP plant, is maintained. The total storage volume can be divided into one, two, four, or eight parallel tanks while considering several aspect ratio values ($AR=0.5$ to 10) and wall inclinations ($\phi =0^{\circ }$, 5°, and 10°). The reinforced concrete walls excel in every aspect considered, and the one-tank configuration with $AR=1$ and $\phi =0^{\circ }$ presents the best $LCOS$.