Study on development and testing of low-carbon Firebrick battery for reject heat storage

This research explores the design, development, and experimental validation of a firebrick-based thermal energy storage (TES) system tailored for industrial applications involving reject heat. Industrial processes often release substantial quantities of high-grade thermal energy into the environment, contributing to energy inefficiency and environmental degradation. The proposed TES solution addresses this issue by utilizing low-cost, locally available firebricks. These firebricks serve as the primary heat storage medium due to their high thermal stability, resistance to extreme temperatures, and environmental safety. The presented solution holds superiority over other commercial energy storage systems owing to its lack of need for mined material and rare-earth minerals, thus lowering its carbon footprint. The system is built around a stainless-steel container filled with firebricks and integrated with a square air duct housing nichrome heating coils, controlled by PID feedback systems and enhanced by forced convection via axial fans. This configuration ensures even thermal distribution, efficient charging, and prolonged heat retention. To replicate industrial rejected heat, the nichrome coils were used to heat the firebricks up to 330 °C, simulating conditions typically encountered in manufacturing sectors such as cement, steel, and ceramics. Experimental validation demonstrated that the system charged from ambient temperature of 36 °C–90 °C in 100 min and discharged back to ambient temperature over 350 min, achieving a charging-to-discharging time ratio of approximately 1:3.5. Scaled-up analysis predicted a heat retention duration exceeding 34 h, thus surpassing the market products that hold heat for 18 h and proving the feasibility for next-day thermal reuse. The modular design, combined with cost-effective materials such as Siporex mounts and Rockwool insulation, ensures durability, scalability, and operational safety. The study also benchmarks the prototype's performance against existing commercial TES systems like Rondo, Caldera, and Kraftblock, emphasizing the economic and environmental advantages of firebrick-based storage in the industrial landscape. The proposed solution paves the way for sustainable heat recovery systems in medium-to-high temperature industrial settings, promoting energy efficiency, reducing fossil fuel dependency, and contributing to global decarbonization goals.