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1
Conceptual design and exergy analysis of combined cryogenic energy storage and LNG regasification processes: Cold and power integration

Lee, Inkyu,Park, Jinwoo,Moon, Il Pergamon Press 2017 Energy Vol.140 No.1
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Abstract This study aims to develop an efficient cryogenic energy storage (CES) process using the exergy from liquefied natural gas (LNG) regasification. While LNG has low internal energy, it has high exergy because of its cryogenic characteristics, and much of this exergy is wasted in the process of regasification. Thus, this work focuses on the recovery of LNG cold exergy to store cryogenic energy using air as a working fluid. The cold exergy of LNG is transferred in two forms: cold transfer by heat exchange to liquefy air, and shaft work transfer by direct expansion of LNG to compress the air. Thermodynamic analysis of the proposed process is carried out in three exergy flow steps: the LNG regasification step, the air liquefaction step, and the air expansion step. In addition, the proposed system has an advantage which system can store and release the energy simultaneously. Therefore, daily produced energy by CES system is more than double compare to the most recent contributions that have divided operation modes for energy storage and release. This study not only proposes an efficient energy storage process that can generate power flexibly but also highlights further possibilities for performance enhancement by thermodynamic analysis. Highlights <UL> <LI> The integrated Cryogenic energy storage (CES) and liquefied natural gas (LNG) regasification process is proposed. </LI> <LI> Exergy efficiency of the air storage process is 94.2%, and the air release process is 61.1%. </LI> <LI> The specific power output per 1 kg of LNG is about 160.92 kJ. </LI> </UL>
2
A novel cryogenic energy storage system with LNG direct expansion regasification: Design, energy optimization, and exergy analysis

Lee, Inkyu,Park, Jinwoo,You, Fengqi,Moon, Il Elsevier 2019 ENERGY Vol.173 No.-
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Abstract Recovering the remaining cold energy from the regasification process is one of the key challenges of the overall LNG value chain. This paper aims to develop a cryogenic energy storage system (CES) integrated with LNG direct expansion regasification (LNG–CES) that can recover cold energy and store it as cryogenic energy using air as the working fluid. Cold energy of LNG is available in two forms: thermal energy by heat exchange and shaft work by expansion, while the cryogenic storage process requires compression and cooling. The supply and demand of LNG direct expansion and cryogenic energy storage processes are well balanced. Therefore, a combined LNG–CES process to store energy will prove efficient. This study proposes an industrial-feasible design for the LNG–CES process and energy optimization to maximize net power output from the process. Moreover, a novel process design is proposed to recover cold energy lost during LNG regasification more efficiently. Energy optimization results of the proposed design demonstrated an 11.04% increase in the net power generation from the feasible configuration of the base design. Additionally, the cause of this improvement was studied using thermodynamic analyses. Highlights <UL> <LI> A feasible design of cryogenic energy storage process with LNG regasification. </LI> <LI> A novel design for efficient air sub-cooling via two-stage LNG pressurization. </LI> <LI> A thermodynamic based optimization to maximize net power output. </LI> </UL>
3
Experimental study on the cryogenic thermal storage unit (TSU) below -70 °C

Byeongchang Byeon,Kyoung Joong Kim,Sangkwon Jeong,Dong min Kim,Mo Se Kim,Gi Dock Kim,Jung Hun Kim,Sang Yoon Lee,Seong Woo Lee,Keun Tae Lee 한국초전도저온학회 2024 한국초전도저온공학회논문지 Vol.26 No.1
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  ScienceON
  
  eArticle
Over the past four years, as the COVID-19 pandemic has struck the world, cold chain of COVID-19 vaccination has become a hot topic. In order to overcome the pandemic situation, it is necessary to establish a cold chain that maintains a low-temperature environment below approximately 203K (-70°C), which is the appropriate storage temperature for vaccines, from vaccine suppliers to local hospitals. Usually, cryocoolers are used to maintain low temperatures, but it is difficult for small-scale local distribution to have cryocooler due to budget and power supply issues. Accordingly, in this paper, a cryogenic TSU (Thermal storage unit) system for vaccination cold chain is designed that can maintain low temperatures below -70°C for a long time without using a cryocooler. The performance of the TSU system according to the energy storage material for using as TSU is experimentally evaluated. In the experiments, four types of cold storage materials were used: 20% DMSO aqueous solution, 30% DMSO aqueous solution, paraffin wax, and tofu. Prior to the experiment, the specific heat of the cold storage materials at low temperature were measured. Through this, the thermal diffusivity of the materials was calculated, and paraffin wax had the lowest value. As a result of the TSU system's low-temperature maintenance test, paraffin wax showed the best low-temperature maintenance performance. And it recorded a low-temperature maintenance time that was about 24% longer than other materials. As a result of analyzing the temperature trend by location within the TSU system, it was observed that heat intrusion from the outside was not well transmitted to the low temperature area due to the low thermal conductivity of paraffin wax. Therefore, in the TSU system for vaccine storage, it was experimentally verified that the lower the thermal diffusivity of the cold storage material, the better low temperature maintenance performance.