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

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 m³. 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.