Experimental study on single-unit solid particle packed bed for thermal energy storage of extracted steam from thermal power plant to consume more renewable energy

Abstract

Solid particles instead of molten salt as a heat storage medium for extracted steam energy storage are essential in thermal power flexibility retrofit. This study constructs a charge-discharge experimental device using by-products from the steel industry as heat storage materials, similar to a battery cell, which is easily scalable and accomplishes the steam-solid particle-steam energy conversion. Investigation parameters include temperature distribution, power variation, and cycle efficiency for different charging and discharging modes. Results indicate that the charging mode II outperforms mode I in temperature uniformity, charging flow rate, and pressure loss, yielding higher charging power and total convective heat transfer coefficients at 13 kW and 275 W/(m² K), respectively. The pilot device demonstrates commendable insulating properties. Its heat dissipation rate is approximately 33.33%, which surpasses that of reported thermal storage devices. Moreover, the mode II exhibits superior temperature non-uniformity during heat release, ensuring that 40 kg/h of superheated steam at 220 °C can be produced continuously for 5 min. The cycling efficiency is noteworthy, reaching 65% in low flow rate discharge, accompanied by 79% charging efficiency and 82% discharging efficiency. A temperature difference cloud map elucidates the primary phase change region, emphasizing preheating, evaporation, and superheating segments. Experimental results provide new ideas for combining waste elimination in the steel industry and energy storage in thermal power plants.