# Design Considerations for the Liquid Air Energy Storage System Integrated to Nuclear Steam Cycle
###### Abstract  
A nuclear power plant is one of the power sources that shares a large portion of base-load. However, as the proportion of renewable energy increases, nuclear power plants will be required to generate power more flexibly due to the intermittency of the renewable energy sources. This paper reviews a layout thermally integrating the liquid air energy storage system with a nuclear power plant. To evaluate the performance realistically while optimizing the layout, operating nuclear power plant conditions are used. After revisiting the analysis, the optimized performance of the proposed system is predicted to achieve 59.96% of the round-trip efficiency. However, it is further shown that external environmental conditions could deteriorate the performance. For the design of liquid air energy storage-nuclear power plant integrated systems, both the steam properties of the linked plants and external factors should be considered. liquid air energy storage (LAES); nuclear power; load following operation +
Footnote †: journal: Applied Sciences  
19 July 2021 10 September 2  
The intermittency problem of renewable energy can be alleviated with a flexible operation of conventional power plants such nuclear and coal power. In this study, the authors focus on the concept of directly coupling ESS to the conventional power plant to enhance flexibility. However, there is also a study suggesting that renewable energy with ESS can support grid stabilization when a nuclear or coal power plant goes out of service unexpectedly [10]. Thus, the grid stability can be improved by adding ESS to either conventional energy sources or renewable energy sources. Nuclear power is one of the main sources of baseload generation in many countries [11]. As previously mentioned, the increase of renewable sources inevitably demands the load reduction of existing nuclear plants. Although some nuclear power plants have the capacity to control the output power following the demand (load following), not all of them can be operated in load following mode. Even if they do so, the periodic output changes in the core can affect the service time of safety important equipment and can even deteriorate the integrity of the reactor core [12]. Such load reduction strategies can also curtail the economic return from the nuclear plants [13], since they economically perform best when operating at full load to maximize the generation profit from the large initial investment. An alternative way of shifting the load of conventional nuclear plants is to integrate a large-scale ESS to the secondary system of a nuclear power plant; a system from steam generator to steam turbine. Without changing the reactor output, this method stores energy available from the steam cycle during the period of overgeneration and generates extra energy during high demand. The solution is a better way to retrofit nuclear power plants that were previously unable to follow the load due to stability problems. However, the ESS technologies suitable for such integration need to be scalable to the level of nuclear plants and affordable at such sizes. One of the potential candidates is the liquid air energy storage (LAES) system, recently receiving attention due to its potential for fast deployment [14]. A research team from the University of Birmingham suggested a conceptual study combining a liquid air energy storage system with a light water reactor [15]. Their results showed that the round-trip efficiency would reach approximately 71%, and output work would be approximately 2.7 times higher than that of the existing nuclear power plant alone. However, the suggested design poses several technical challenges, as marked in Figure 1. First, the discharge mode involves 100% steam bypass from the nuclear secondary side which poses integrity issues to the nuclear power plant's steam cycle. Second, excessively ideal design conditions were used for the performance prediction, including zero pressure drop and low pinch temperatures across heat exchangers [16].