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

<P><B>Abstract</B></P> <P>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.</P> <P><B>Highlights</B></P> <P> <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> </P>

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.-

<P><B>Abstract</B></P> <P>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.</P> <P><B>Highlights</B></P> <P> <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> </P>

수소 저장 방식과 수소저장합금 카트리지 기반 휴대용 에너지 시스템 개발 연구

김태성,김경욱 대한산업경영학회 2025 산업융합연구 Vol.23 No.1

전 세계적으로 수소에너지의 중요성이 높아지면서 다양한 수소 저장 기술이 개발되고 있다. 한국은 수소경제 활성화 로드맵에 따라 수소차와 연료전지를 중심으로 친환경 수소경제 구축을 목표로 하고 있다. 현재의 수소 저장 방식은 고압 기체, 저온 액체, 고체 저장 등으로 나뉘며, 각 방식은 안전성, 효율성, 비용 측면에서 차이가 있다. 본 연구는 수소를 금속합금에 저장하는 고체저장기술을 기반으로 수소고체저장 시스템을 개발하는 것이다. 특히 본 연구자가 개발하고 있는 고체 저장 방식은 높은 밀도로 안정적인 저장이 가능해 미래 유망 기술로 평가된다. 국제에너지기구(IEA)는 2050년까지 재생 가능 에너지 비율을 크게 높이는 로드맵을 제시하며 수소가 에너지 캐리어로서 주요 역할을 할 것으로 전망하고 있다. 본 연구의 목적은 수소 고체저장방식으로 에너지 밀도를 높이고 폭발이나 화재의 위험성을 낮춘 수소 에너지 시스템에 대한 내용이다. As the importance of hydrogen energy grows worldwide, various hydrogen storage technologies are being developed. South Korea aims to establish an eco-friendly hydrogen economy centered on hydrogen vehicles and fuel cells, following its hydrogen economy activation roadmap. Current hydrogen storage methods are categorized into high-pressure gas, cryogenic liquid, and solid-state storage, each differing in terms of safety, efficiency, and cost. This research aims to develop a hydrogen solid storage system based on solid storage technology that stores hydrogen in metal alloys. Among these, the solid-state storage method being developed by this researcher is highly promising for the future due to its high-density and stable storage capabilities. The International Energy Agency (IEA) has set a roadmap to significantly increase the share of renewable energy by 2050, forecasting hydrogen to play a key role as an energy carrier. This study aims to develop a hydrogen energy system with solid-state storage to increase energy density and reduce risks of explosion or fire.

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

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.

Packed bed 방식 다중 냉열저장장치 시스템의 왕복효율 평가를 위한 연속운전 실험

곽다희(Dahui Kwack),이춘식(Chunsik Lee),염층섭(Choongsub Yeom) 대한기계학회 2024 대한기계학회 춘추학술대회 Vol.2024 No.11

The multiple Cryogenic Thermal Energy Storage (CTES) system was suggested to achieve the commercialization of LAES and increase the capacity of the CTES. This study was aimed to experimentally observe the temperature gradient of multiple CTES system, which is packed bed type using pebbles, and evaluate the round-trip efficiency between charging and releasing operation. The round-trip operations were conducted continuously in 3 times, and the temperature gradient changes of the entire system for each time were suggested. The gradient was sigmoid shape at first time and then changed to straight line in next times, so that the released cold energy was reduced at 3rd operation. However, the round- trip efficiency was increased to 65%, because the required cold energy for charging were much reduced. In order to achieve 80% efficiency, the insulation of the system should be improved.

극저온 팽창 이후 액화 공기 조성 변화를 고려한 액화공기에너지저장 시스템의 예비 연구

채용재(Yong-Jae Chae),박정환(Jung Hwan Park),이정익(Jeong Ik Lee) 대한기계학회 2024 대한기계학회 춘추학술대회 Vol.2024 No.11

The implementation of carbon reduction policies has resulted in a notable increase in the proportion of renewable energy sources globally. However, this transition has also given rise to a significant challenge, namely the issue of intermittency. To address this challenge, LAES, which offers high round-trip efficiency, substantial energy density, and capacity, has been the subject of extensive research. The liquefaction rate and performance of LAES have been the subject of study in relation to different layouts and conditions. However, the composition of liquefied air after cryogenic expansion has not been studied. Therefore, it is necessary to consider the ratio of nitrogen and oxygen, which are the main components, as well as the properties of the working fluid during the discharge process, which must be reflected in the performance analysis. When this was considered, the performance of the liquefied air energy storage system under each condition was confirmed.

RE100 대응을 위해 액화가스 에너지 저장을 활용한 반도체 공정챔버용 극저온 냉각시스템 개념설계

이춘식(Chunsik Lee),염충섭(Choongsub Yoem) 한국태양에너지학회 2024 한국태양에너지학회 학술대회논문집 Vol.2024 No.10