Experimental Testing Of a 400 KWh Steel Slag-Based Thermal Energy Storage Prototype for Industrial Waste Heat Recovery Applications

Abstract

There is a clear need to develop cost-effective thermal energy storage systems to improve industrial energy efficiency since great amounts of energy is lost as waste heat. In this paper, a cost-effective 400 kWh thermal energy storage prototype for waste heat recovery at high temperature is tested over different charging and discharging conditions. The technology studied is based on the use of steel slag as thermal energy storage material and air as heat transfer fluid, in a packed bed reactor of 1 m 3 . Since the steel slag is a byproduct of the steelmaking industry its cost is almost negligible, whilst its thermomechanical properties make it very attractive to store heat. The aim of the testing studies is to gather information regarding the heat exchange efficiency between the heat transfer fluid and the slag in different temperature levels, reproducing common industrial off-gas waste heat release. Finally, with these results a technoeconomic calculation approach is provided in the frame of a real waste heat recovery plant in the steelmaking industry, which confirms this technology as a very promising candidate for waste heat recovery solutions.

Characterization of the Ratcheting Effect on the Filler Material of a Steel Slag-Based Thermal Energy Storage

“…In this research, characterization studies conducted by some of the authors [20] retrieved its main thermo-physical properties, namely apparent density (3430-3770 kg•m −3 ), specific heat (890-950 J•kg −1 K −1 ), thermal conductivity (1.2-1.75 W•m −1 K −1 ) and thermal stability under air (1100 • C), confirming its suitability for use as an energy storage material. Subsequently, a laboratory testing campaign was conducted on a 400 kWh TES prototype to assess slag behavior under various charging and discharging conditions [22,23]. The results contributed to the validation of a thermal model designed to scale up the solution for real-scale prototypes.…”