Experimental investigation of tank stratification in liquid air energy storage (LAES) system

Liquid air energy storage technology is a technology that stores liquid air in case of excess power supply and evaporates the stored liquid air to start a power generation cycle when there is an electric power demand. When liquid air is stored for a long-time during operation, safety and performance degradation can be caused or mitigated by the tank stratification. To investigate the tank stratification phenomenon and associated issues, an experimental facility is constructed. The heat ingress is controlled with respect to changing vacuum level in the experiment. Furthermore, the conditions under which stratification occurs are defined in terms of temperature and concentration, and based on this, the stratification stability ratio and the stability map are defined and evaluated experimentally. The results show that the time required for destratification is 8-29% shorter for liquid air mixture cases than for liquid nitrogen. Moreover, the time required for destratification is 2.4 times longer for the high tank pressure cases, and it is 39% shorter for the case of high heat ingress. From experimental observations, an operation strategy utilizing stratification inside the liquid air storage tank is newly suggested that can minimize the boil-off gas of liquid air in the tank.