# Design Considerations for the Liquid Air Energy Storage System Integrated to Nuclear Steam Cycle
## 4 Conclusions  
A model was reproduced from the previously suggested system concept in the previous work [15], and the optimization for realistic operating conditions was completed in this project. An in-house code was developed and utilized to model the liquid air energy  
Figure 9: Ambient Temperature, power consumption and round-trip efficiency (**Top**), LAES Yield (**Bottom**).  
storage (LAES) system combined with a nuclear power plant (NPP). The minor differences in the reference comparison, rooting in the cryogenic components having notable range of differences in the mixture properties, were re-evaluated in this study more realistically.  
The optimization was focused on the conditions targeting the realistic design of the system. The pinch of heat exchanger was limited to 5K which is the common pinch used in the industry. In the 5K pinch case, the power consumption in the storage mode increased, and the power output in the release mode decreased. Moreover, in the actual operation, pressure drop and changes in the ambient temperature are unavoidable. After reflecting these realistic considerations, the round-trip efficiency of the ideal value for the system is 67.6%, which is lower than reported value in the reference [15]. For the 2K pinch case, it is slightly higher at 68.29%.  
Moreover, the round-trip efficiency decreases to 59.96% under the realistic operation conditions from the APR1400 nuclear power plant. Considering the technical and safety issues to bypass a high-pressure turbine from the nuclear power plant, this result is an acceptable alternative to integrate the LAES and the nuclear power plant. Given the pressure drop and changes in the ambient temperature, the actual round-trip efficiency of the LAES nuclear power plant system is expected to have difficulty exceeding 60% efficiency. However, the combination of these two systems presents a new possibility for the original non-existing load following operations. In addition, the LAES-NPP system can expect higher economic value because some of the energy to be discarded is stored in a usable form, whereas conventional load following mode operates as a reduction of reactor power which reduces the capacity factor.  
The following observations were made in the analysis when the realistic design conditions were applied:  
1. Pinch temperature of heat exchangers--storage mode power consumption increased and release mode power output decreased
2. Realistic NPP steam conditions--thermal power from NPP decreased, LAES yield decreased, and release mode power output decreased
3. Pressure drop--round-trip efficiency is slightly decreased
4. Ambient temperature--round-trip efficiency decreased substantially  
In order to increase the efficiency of the integrated systems, the LAES system must be linked under conditions that do not affect the normal operation of the plant. It also requires a design that can efficiently transfer the thermal power of the nuclear power plant to LAES under those conditions. While expanding the heat exchange area, length limit of thermal components is required to minimize pressure drop even under such design conditions. Finally, external factors should also be considered as the LAES-NPP integrated system is sensitive to ambient temperature. These realistic considerations will facilitate the deployment of the LAES-NPP system in the near future.  
Conceptualization, S.-H.S. and J.-Y.H.; methodology, S.-H.S. and J.-Y.H.; software, S.-H.S. and J.-Y.H.; validation, S.-H.S., J.-Y.H. and J.-I.L.; formal analysis, S.-H.S.; investigation, S.-H.S.; resources, S.-H.S.; data curation, S.-H.S.; writing--original draft preparation, S.-H.S.; writing--review and editing, S.-H.S., J.-Y.H. and J.-I.L.; visualization, S.-H.S.; supervision, J.-I.L.; project administration, J.-I.L. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data used in this study are openly available in the reference [15; 17].  
The authors declare no conflict of interest.