# Design Considerations for the Liquid Air Energy Storage System Integrated to Nuclear Steam Cycle
## 3 Result and Discussion
### Pressure Drop and Ambient Temperature Effects  
In any type of hydrodynamic component and pipe, the pressure of fluid is decreased by frictional pressure drop while traveling in the components and pipelines. In this study, the pressure drop is modeled as a fractional pressure drop of the system pressure while ignoring the shape and flow path of air going through the system. The pressure drop changes the properties of fluid; therefore, the output and consumption power of each component will change. The increase of pressure drop lowers the round-trip efficiency, shown in the top of Figure 8. This is because the liquid air yield is substantially reduced in the separator, which leads to a decrease in overall flow rate of the LAES system during release mode as shown in the bottom of Figure 8. Consequently, the reduced mass flow rate of air in the heat exchanger 4 results in the decreased steam mass flow rate from the steam cycle, and thus, the delivered thermal power is reduced to have an increasing effect on the round-trip efficiency. However, net output power from the air turbines reduces due to lowered expansion ratio, and overall, the round-trip efficiency decreases. It is thus necessary to minimize the number of components that make up the system in order to prevent round-trip efficiency degradation caused by pressure drop in the actual system.  
The sensitivity of the overall system to the change in ambient temperature is also studied. As the LAES system is an open system that inhales air from the outside of the system to operate, there is a significant impact on the operation with respect to the ambient condition. The ambient temperature was set to 288K in the above calculations. However, the ambient temperature can increase or decrease due to seasonal change or the weather conditions in the installed location. Since it is trivial that a decrease of the ambient temperature will be helpful to increase the round-trip efficiency, as cold air will consume less energy to be liquefied, only the increase of ambient temperature case is presented in this study.  
The rise in ambient temperature decreases the round-trip efficiency of the system because of the increased energy consumption in storage mode. Due to the nature of the LAES using the air as an energy storage medium, the higher the temperature of the ambient air, the more energy is consumed to cool the air, as shown in the top of Figure 9. The increase in ambient air temperature also increases the temperature of the No. 5 hot side inlet of heat exchanger 6. This increases the temperatures of outlet No. 6 and No. 9 from heat exchanger 6, which leads to a decrease in the liquid air yield. Moreover, the reduction of the liquid air yield reduces the mass flow rate in the system during the release mode and consequently reduces the generated power of the release mode. This trend is shown in the bottom of Figure 9. The reduction of power output leads to a decrease in round-trip efficiency. The round-trip efficiency is further deteriorated by the net power consumption increase during the storage mode, which is shown in the top of Figure 9. This consequently reduces the round-trip efficiency as the ambient temperature increases.  
Figure 8: Pressure drop, power consumption, and round trip efficiency (**Top**), LAES Yield (**Bottom**).