Liquid Air Energy Storage System Research Articles

Thermodynamic analysis of liquid air energy storage system integrating LNG cold energy

Liquid air energy storage (LAES) presents a promising solution to effectively manage intermittent renewable energy and optimize power grid peaking. This paper introduces a LAES system integrating LNG cold energy to flexibly manage power peaking, including intermediate energy storage, power generation using organic Rankine cycle, multi-stage direct expansion, and solar energy for heating. Aiming to maximize the electrical round-trip efficiency, a genetic algorithm is employed to optimize the operational parameters of the proposed LAES system. The results indicate that the combined design of cold energy utilization, multi-stage direct expansion and solar heating for proposed LAES system significantly improve the power performance, achieving an energy capacity of 0.125 kWh/kgLNG and an electrical round-trip efficiency of 376.7 %. The exergy losses of heat exchange equipment are far larger than mechanical equipment in the LAES system, so the optimization design of heat exchange equipment is preferred to improve the exergy performance. The proposed system achieves both high efficiency and flexibility and hence contributes to the development of liquid air energy storage systems.

Sustainable energy storage solutions for coal-fired power plants: A comparative study on the integration of liquid air energy storage and hydrogen energy storage systems

With the majority of the world's energy demand still reliant on fossil fuels, particularly coal, mitigating the substantial carbon dioxide (CO2) emissions from coal-fired power plants is imperative for achieving a net-zero carbon future. Energy storage technologies offer a viable solution to provide better flexibility against load fluctuations and reduce the carbon footprint of coal-fired power plants by minimizing exergy losses, thereby achieving better energy efficiency. This work focuses on developing two such energy storage technologies: Liquid Air Energy Storage (LAES) and Hydrogen Energy Storage (HES), and their integration strategies with a sub-critical coal-fired power plant. The performance of the integrated systems is analyzed based on key parameters like energy storage capacity, net unit power output during charging and discharging, round-trip efficiencies, and net unit efficiencies at different operating load conditions of the plant. Our results show that during the charging cycles, by increasing the air flow rate in LAES and the hydrogen production rate in HES, the net unit efficiency of the integrated plant decreases by 3–10% at different load conditions, while the energy-based round-trip efficiency increases with increasing liquid air and hydrogen flow rates during the discharge cycles. For the HES system, utilization of the produced hydrogen in the fuel cells gives 40–50% better roundtrip efficiencies than co-firing hydrogen in the boiler at full and minimum load and it increases with increasing hydrogen flow rates. While HES has shown a better overall net unit efficiency (41.5%, in fuel cell scenario) of the integrated unit than the LAES system (40%) for the base case operation, LAES shows superior round-trip efficiencies when operated at higher liquid air discharge flow rates (>80 kg/s). The results provide insights into the system modeling of LAES and HES integrated with a sub-critical coal power plant, contributing to the advancement of sustainable energy storage solutions.

Evaluating economic feasibility of liquid air energy storage systems in US and European markets

Liquid air energy storage is a clean and scalable long-duration energy storage technology capable of delivering multiple gigawatt-hours of storage. The inherent locatability of this technology unlocks nearly universal siting opportunities for grid-scale storage, which were previously unavailable with traditional technologies such as pumped hydro energy storage and compressed air energy storage. While the technical viability of liquid air energy storage has been established, its economic viability has not yet been rigorously assessed across diverse electricity markets. In this work, a mixed-integer linear program was used to conduct a high-level economic analysis of this technology in US and European markets. By simultaneously optimizing the design and operation of liquid air energy storage systems to maximize their net present value, a yes/no indication of their economic viability can be obtained. Using this approach, the economic viability of this technology was established for the West load zone of Texas through identification of a system with an optimal net present value of $10.4 million and a levelized cost of storage of $119/MWh. Sensitivity analyses were also performed to elucidate how improved technical performance and economic incentives might affect the economic feasibility and, consequently, the adoption of this technology more broadly in the future.

Research on dynamic characteristics and control strategy of energy release process of liquid air energy storage system

Research on dynamic characteristics and control strategy of energy release process of liquid air energy storage system

A novel system of liquid air energy storage with LNG cold energy and industrial waste heat: Thermodynamic and economic analysis

Liquid air energy storage (LAES) is a promising technology for large-scale energy storage applications, particularly for integrating renewable energy sources. While standalone LAES systems typically exhibit an efficiency of approximately 50 %, research has been conducted to utilize the cold energy of liquefied natural gas (LNG) gasification. This approach, applied during the LAES energy storage phase of air compression and liquefaction, can reduce the power consumption of the compressor and enhance the performance of the integrated system. However, the improvement in the system's efficiency is constrained due to the low temperature of the air entering the turbine expansion during the energy release phase. Most studies only focus on the utilization of LNG cold energy, neglecting the proper utilization of the cold energy generated during the liquid air gasification process. This paper proposes an integrated system of LNG cold energy utilization and cement industry waste heat recovery (WHR) with LAES (LNG-LAES-WHR). A thermodynamic model is constructed, and the system is optimized by using four-stage compression, four-stage expansion, and R601 as the working fluid for WHR. The optimized integrated system has a round-trip efficiency (RTE) of 176.27 % and achieves a power output of 337.53 MW. Compared to the previously proposed system, this system has a high exergy efficiency of 74.49 % with a maximum energy storage capacity of 0.5918 kW/kg LNG. The economic analysis shows that the system has the best economic performance when constructed in Zhuhai: the dynamic payback period (DPP) is 4.2 years and the life cycle net present value (NPV) is 1170.72 million USD. This system realizes the cascaded utilization of energy, both in terms of heat and cold, which is safe, flexible, and highly efficient. This work provides a reference for the design of integrated systems for large-scale LAES for industrial applications.

Modelling and simulation of a novel liquid air energy storage system with a liquid piston, NH[formula omitted] and CO[formula omitted] cycles for enhanced heat and cold utilisation

A liquid piston system (LP) is proposed to recover energy during the discharge of a liquid air energy storage (LAES) plant. The traditionally used air turbine is replaced with an LP system which will expand the evaporated air to generate power. Moreover, an NH3 and transcritical CO2 cycle are integrated to enhance heat and cold utilisation. The integrated LAES system was modelled using gPROMS. The numerical results have a maximum discrepancy of less than 6.4% from experimental data previously reported in the literature. The round-trip efficiency (RTE) was studied for various scenarios, including the sensitivity to thermal oil flow rate and heat exchanger efficiencies. Additionally, the study examined the influence of several LP configurations and concluded with a comparison to a conventional LAES system. With a liquefaction pressure of 40 bar, the highest RTE reached was 37%, surpassing the conventional LAES system’s 25% RTE at a discharge pressure of 25 bar. The heat utilisation was 96%, which doubles that of the conventional LAES system, while the cold utilisation was enhanced by 10%. Furthermore, the LP, NH3, and CO2 cycles thermal efficiencies were 88%, 19%, and 30%, respectively. A detailed energy assessment for heat and cold utilisation is presented.

Novel liquid air energy storage coupled with liquefied ethylene cold energy: Thermodynamic, exergy and economic analysis

Liquid air energy storage (LAES) technology, unrestricted by geographical conditions and capable of flexible integration with external energy sources, holds considerable potential. However, the efficiency of the LAES system is hindered by the shortage of cold energy, requiring the introduction of external cold energy. Currently, research on external cold energy coupling predominantly concentrates on the regasification cold energy of Liquefied Natural Gas (LNG), with scant attention to other cold energy sources, such as ethylene. The conventional regasification process of Liquefied Ethylene (LE) is accompanied by the wasting of abundant regasification cold energy, making it crucial to explore a method to effectively recover and utilize it. This study firstly presents two system cases that couple LAES with the regasification cold energy of LE, filling the research gap. Two cases are simulated: Case 1 utilizes the LE cold energy to cool the air after compression, similar to the common method of coupling LNG cold energy, and Case 2 innovatively applies LE cold energy in low-temperature compression and cooling after compression, along with the introduction of 350 ℃ solar thermal energy. Key parameters in Case 2 are optimized through sensitivity analysis. Additionally, exergy destruction and economic analysis of the two cases are conducted. The main results indicate that: the round-trip efficiency (RTE) and exergy efficiency (EXE) of Case 1 are 63.3% and 59.5%, respectively; for Case 2, although the EXE of 57.06% is slightly lower than Case 1, the RTE can be markedly improved to 211.4%, and it has a lower initial investment cost, quicker return, and lower investment risk. This study systematically presents a novel technical solution for the integration of external cold energy with LAES systems, marking the first investigation into the coupling of LAES systems with liquefied ethylene regasification processes.

Thermo-economic multi-objective optimization of the liquid air energy storage system

Liquid Air Energy Storage (LAES) is a promising energy storage technology for large-scale application in future energy systems with a higher renewable penetration. However, most studies focused on the thermodynamic analysis of LAES, few studies on thermo-economic optimization of LAES have been reported so far. Thus, this work focuses on the multi-objective optimization of LAES by using non-dominated sorting genetic algorithm (NSGA-II), taking the round trip efficiency (RTE) and economic indicators as the optimization objectives. Three major results were obtained from this work. First, the NSGA-II-based optimization framework is able to determine the optimal design and operational parameters of LAES under different configurations and scenarios, including the optimal charging and discharging pressure, heat transfer areas, and mass flow rates of hot and cold storage media etc. It is shown that the increase of energy efficiency by 9 % ~ 14 % and a decrease of exergy destruction by 16 % were seen. Secondly, the design and operational guidelines of LAES can be derived from the optimization. The optimal charging pressure was found to vary between 13 and 15 MPa, and the optimal discharging pressure is between 9 and 12 MPa, depending on the machines' efficiencies and pinch points of heat exchangers of a LAES system. Finally, the Pareto Fronts of capital expenditure, energy efficiency and the occupied space energy density of a LAES system provide system operators good operational and investment advice. Specifically, the RTE of the LAES increasing by 1 % is at the cost of increasing the capital cost by 0.5–1 %. In this study, if the investment budget is over 48 M£, a LAES system with three-stage compressors and four-stage turbines presents better trade-off between RTE and investment cost than the three-stage and four-stage systems. Overall, this work provides, for the first time, an NSGA-II-based optimization framework capable of determining the optimal design and operational parameters of LAES, informing the stakeholders of the design guidelines and investment guidance under different scenarios.

Experimental analysis of packed bed cold energy storage in the liquid air energy storage system

Liquid air energy storage (LAES) is a large-scale energy storage technology with extensive demand and promising application prospects. The packed bed for cold energy storage (CES) is widely applied in LAES due to its safety and environmental friendliness. At present, most of the research on CES is theoretical analysis with symmetric cold energy transfer. Actually, the changes of the temperature field result in asymmetrical energy transfer in the energy storage and release processes, but there are few experimental studies on the dynamic characteristics and parameter influence mechanism. Therefore, a platform is established and experiments with different conditions are conducted. The dynamic characteristics of CES and the corresponding performance of LAES are analyzed. The results show that the thermocline develops until outlet temperature changes, leading to a decrease in the LAES efficiency. Under basic conditions, the energy and exergy efficiencies of CES are 90.3 % and 73.3 %. Selecting materials based on physical properties, reducing the flow rate and temperature range of the fluid can improve the packed bed performance. Furthermore, dynamic characteristics of CES gradually weaken until reaching a stable state after multi-cycle, with energy and exergy efficiencies decreasing by 2.5 % and 8.0 %. The decline in the LAES energy efficiency is 4.7 %.

The effect of insulation on boil-off gas in liquid air storage tank

Increasing renewable energy is posing a challenge to the stability of electricity grid, and the importance of an energy storage system (ESS) is becoming clearer. A Liquid Air Energy Storage System (LAES) is proposed as one of the promising ESS technologies. LAES converts electricity to liquid air efficiently and economically. However, since the storage temperature of liquid air is −196 °C, loss of liquid air is inevitable due to evaporation, i.e., boil-off gas (BOG). A loss of liquid air has negative effect on the round-trip efficiency of LAES; therefore, the BOG rate must be minimized. In this research, the insulation performance of liquid air tank is evaluated. To calculate the heat ingress and BOG rate, a partial equilibrium model is developed. The insulation performance is evaluated with varying insulation thickness, emissivity, aspect ratio and materials. The results show that the BOG rate of vacuum insulation can reach 1.8 %/day. For foam glass insulation, the BOG rate can become 2.25 %/day. With optimal geometry, 0.7 %/day for vacuum insulation and 1 %/day for foam glass insulation can be achieved. The vacuum insulation generally shows better insulation performance, however, there is area where the foam glass insulation shows better performance depending on the insulation thickness and emissivity.

Photovoltaic-driven liquid air energy storage system for combined cooling, heating and power towards zero-energy buildings

Renewable energy and energy storage technologies are expected to promote the goal of net zero-energy buildings. This article presents a new sustainable energy solution using photovoltaic-driven liquid air energy storage (PV-LAES) for achieving the combined cooling, heating and power (CCHP) supply. Liquid air is used to store and generate power to smooth the supply-load fluctuations, and the residual heat from hot oil in the LAES system is used for the cooling and heating supplements. Taking an actual building as the research object, the dynamic PV-LAES system model is built to optimize the power/cooling/heating supplies, and then evaluate the economic and environmental performances. In a single year, the PV-LAES system can produce 523.93 MWh of electricity, 57.75 GJ of cold energy, and 119.24 GJ of heat energy, resulting in an improved round-trip efficiency of 67.05 % and a carbon emission reduction of 368.35 tons. The dynamic payback period is 6.45 years and the cumulative net present value (NPV) reaches 515 k$ throughout the life cycle. Overall, this article provides a new solution using the PV-LAES system to obtain high energy efficiency, good economic benefits, and high environmental performance for future zero-energy buildings.

Techno-economic analysis of a new thermal storage operation strategy for a solar aided liquid air energy storage system

The SA-LAES system is an economical and efficient energy storage solution that combines solar energy with LAES. However, the inherent instability of solar energy can result in uncertainty regarding heat storage, thereby compromising the stability of the energy storage system. The development of more economical, efficient, and stable strategies for the SA-LAES system represents a challenging task. The present study puts forward a novel thermal storage operation scheme (Strategy 2) for SA-LAES systems integrated with electric heating during valley periods, thereby achieving long-term stable operation of the energy storage system via the alternating utilization of two full molten salt tanks and one empty molten salt tank. Theoretical and case studies are conducted based on thermodynamic and economical technical indicators, and detailed comparisons are made with the traditional strategy (Strategy 1) of only changing the solar multiple and capacity. The results show the exergy destruction of Strategy 1 mainly occurs in air turbines under off-design operating conditions. The exergy destruction of Strategy 2 is mainly in the electric heater part. The single-day analysis found that the new strategy has a more significant advantage in terms of exergy efficiency than Strategy 1 when the direct normal irradiance (DNI) is below 650 W/m2. In the case study, the levelized cost of energy (LCOE) values for Nanning, Beijing, and Hami regions in Strategy 2 are 0.118 $/kWh, 0.077 $/kWh, and 0.062 $/kWh, respectively. The LCOE values of Strategy 2 are decreased by 10.97 %, 27.49 %, and 3.40 % compared to Strategy 1, respectively. The payback periods for investments in the Beijing and Hami regions have decreased by 67.63 % and 16.41 %, respectively. The research presented in this article provides an economical, efficient, and stable operating strategy for thermal storage in the SA-LAES system.

Dynamic characteristics of a novel liquid air energy storage system coupled with solar heat and waste heat recovery

Liquid air energy storage (LAES) is a promising energy storage technology for its high energy storage density, free from geographical conditions and small impacts on the environment. In this paper, a novel LAES system coupled with solar heat and absorption chillers (LAES-S-A) is proposed and dynamically modeled. A power-speed control system is established for this system. Two operating control strategies are developed for the solar heat collection process. The transient characteristics of the novel system during the start-up, load-up process and encountering different disturbances are investigated. Besides, the dynamic responses when the waste heat is used for producing heating energy are also studied. The results indicate that the power-speed control system can guarantee a very short equilibrium time and a very small overshoot. The energy efficiency of the LAES-S-A system is 65.84 %, while that is 75.32 % when the waste heat is used for producing heating supply. When a disturbance occurs, the equilibrium times of the absorption chiller, air turbines and heating device are 1500 s, 40 s and 38 s, respectively. Compared with the absorption chiller, the heating device can better cooperate with the air turbines. The results can provide a reference for future studies.

Techno-economic analysis of an advanced polygeneration liquid air energy storage system coupled with LNG cold energy, solar energy, and hydrate based desalination

Techno-economic analysis of an advanced polygeneration liquid air energy storage system coupled with LNG cold energy, solar energy, and hydrate based desalination

Novel ASU–LAES system with flexible energy release: Analysis of cycle performance, economics, and peak shaving advantages

This study uses a cryogenic distillation method air separation unit (ASU) coupled with liquid air energy storage (LAES) to improve the round-trip efficiency and reduce the initial investment of LAES. We propose an integrated system (ASU–LAES–DER) with different ways of energy release. In the novel system, the liquid air can be reheated and expanded to produce additional power, or the liquid air energy stream and part of the material stream can be used for ASU distillation to produce power saving effects. This novel integration allows the ASU to have load regulation capability and facilitates the implementation of demand-side power management. Furthermore, the flexible and efficient energy release methods improve the energy efficiency and economic value of LAES. The comprehensive round-trip efficiency of the system can reach 52.1%–69.2 % with a payback period of 3.25–6.72 years. The peaking index is used to analyze the peak-to-valley load transfer capability of the novel system. Results show that the peaking index ranges from 25.5 MW to 50.1 MW at different scales, indicating that the system can be used as an important grid peaking unit when applied on a large scale.

Advancing liquid air energy storage with moving packed bed: Development and analysis from components to system level

Liquid air energy storage (LAES) technology is a promising large-scale energy storage solution due to its high capacity, scalability, and lack of geographical constraints, making it effective for integrating renewable energy sources. The core unit of the LAES system is the cold energy storage (CES) unit, which significantly influences its overall efficiency. However, the current mainstream liquid-phase and solid-phase CES methods have inherent drawbacks, including safety, environmental issues, and the dynamic effect of the thermocline. Moreover, previous research has often over-idealized the CES unit and neglected the actual heat transfer processes during the CES and cold energy release (CER) processes. In the innovative study, a gravity-driven moving packed bed (MPB) based LAES system (MPB-LAES) adopting quartz sand as the CES medium is proposed. A thermodynamic model for the LAES system is constructed, and the gas-solid counterflow coupling heat transfer model for the MPB is developed based on the continuous solid-phase model and finite difference method. The accuracy of the model is validated through experimentation using the constructed test apparatus. The research findings reveal the gas-solid coupling heat transfer characteristics in the low-temperature region of −180 °C to 30 °C, particularly the asymmetry during the CES and CER processes. The cold energy transfer mechanism within the CES unit is also uncovered, and the analysis of exergy destruction within various components is carried on. Through design parameter analysis and optimization of the MPB-LAES system, an impressive round-trip efficiency of 57.0% is achieved. This marks a significant breakthrough as it is the first report that a LAES system based on solid-phase CES has attained a round-trip efficiency (RTE) of over 55.0% while considering the actual heat transfer processes.

Novel heat transfer fluid for maximum recovery of heat of compression: A steady state analysis on improving the performance of liquid air energy storage

BackgroundEnergy storage is a key technology required to manage the limitation of the variability of renewable energy resources. In this study, a concept of energy storage based on Liquid Air Energy Storage (LAES) is presented, with proposed designs to improve the performance based on the heat transfer fluid. The heat generated from the compression of ambient air during the charging stage is usually stored in the heat storage tank and later used for power recovery in the discharging process. The challenge with the LAES is their low round-trip efficiency. Studies have proposed different system configurations and materials for improving the efficiency of the LAES technology, by incorporating multigeneration systems (like organic Rankine cycle, refrigeration system etc.), packed beds for the charging and discharging process, and fluids for cold storage. MethodThis study presents a first-of-its-kind nanofluid analysis for heat recovery in the charging process of ambient air. The effect of hybridization and volume fraction of carbon nanotubes was analysed, in comparison with other oils (Therminol-VP1, Therminol-66, and Dowtherm Q). ResultThe results show that nanofluid@0.005 requires 3331 m3 of storage tank, which caused the least investment cost of the high-temperature storage tank, with $ 2.318 Million. The levelized cost of storage for the LAES systems utilizing nanofluid@0.005, nanofluid@0.001, nanofluid@0.0005, Therminol-VP1, Dowtherm-Q, and Therminol-66 are 208.4 $/MWh, 209.1 $/MWh, 209.7 $/MWh, 211.1 $/MWh, 211.7 $/MWh, and 210.2 $/MWh respectively.

Comprehensive performance investigation of a novel solar-assisted liquid air energy storage system with different operating modes in different seasons

Recently, many researchers have put a spotlight on solar-assisted liquid air energy storage (LAES) system for its cleanliness and large storage capacity. However, the energy efficiencies of such systems are relatively low, resulting in poor economic performance. In addition, very few studies are conducted on the performance of such systems with multi-generation output. Thus, a novel solar-assisted LAES system with different operating modes (LAES-S-D) in different seasons is proposed, which fully utilizes the solar heat and air compression heat to supply cooling/heating/power/domestic hot water in different seasons to meet the energy requirements of users in different seasons. The waste heat recovery/utilization potential of the system is analyzed from the perspective of the energy cascade utilization. Energy, exergy, techno-economic and exergoenvironmental performances are deeply investigated. In contrast with the reference system, the energy efficiency is improved from 0.5101 to 0.5561 (transition seasons), 0.7849 (summer) and 0.8674 (winter), respectively. The net present value is improved by 324.63 million $, the levelized cost of energy is reduced by 0.0774 $/kWh and the dynamic payback time is decreased by 4.87 years.

Performance improvement of liquid air energy storage: Introducing Stirling engine and solar energy

Liquid air energy storage (LAES) is a promising energy storage system with the main advantage of being geographically unconstrained. The efficiency of LAES could be improved by utilizing compression heat and integration with other systems. As an effective heat recovery process, the Stirling engine (SE) is introduced to the LAES system. The Pseudo Stirling model and Malmo relation are used to obtain practical results. Firstly, the Stirling engine is used to utilize compression heat, in which the Round Trip Efficiency (RTE) could be improved by 3.16% points and 8.96% points in LAES-SE and Liquified Natural Gas (LNG)-LAES-SE systems. Then, with solar energy introduced as heat source for the Stirling engine and air before the expander as heat sink, a more flexible Solar-LAES-SE system with decoupled charging and discharging sections is proposed. The RTE and exergy efficiency of the Solar-LAES-SE system are studied and compared with those in a Solar-LAES-Organic Rankine Cycle (ORC) and an LAES system directly heated by Solar energy. The exergy analysis shows that it is more effective to directly heat the air before expanders by solar energy than to integrate an ORC or a Stirling engine if the solar energy is insufficient. The Solar-LAES-SE systems show the best performance in terms of RTE when the air temperature before expanders is low and the molten salt (solar energy carrier) outlet temperature is high. The cost evaluation of the solar energy storage section shows that when the molten salt outlet temperature is lower than 370 °C, the cost of the molten salt-based storage system for the Solar-LAES-SE will be lower than the cost of the thermal oil-based storage system for Solar-LAES-ORC. The reason is a reduced flowrate of molten salt for decreased outlet temperature, thereby increasing temperature change for the molten salt. With a fixed duty of the heat transfer, this reduces the flowrate of molten salt. As a result, the cost of molten salt and its storage is reduced.

Cryogenic energy storage characteristics in cascaded packed beds

Energy storage is a key technology required to utilize intermittent or variable renewable energy sources such as wind or solar energy. Liquid air energy storage (LAES) technology has important research value because of its advantages of high energy density and free construction from regional restrictions, and the high efficiency and stable operation of the cold thermal storage subsystem is of great significance for LAES application. Therefore, this paper experimentally studies the operating characteristics of the cryogenic energy storage device in the LAES system. By using a cascaded packed bed to store cryogenic energy in different temperature ranges, different flow rates of fluids with different specific heat capacities can be distributed. Hence, the temperature difference between the heat transfer fluids can be reduced, thereby improving the energy and exergy efficiencies. In this study, the experimental system and operating procedures are detailed herein. The pressure drop correlation of the packed beds under the combined influence of density gradient and frictional losses is obtained. The variations in the temperature fields in the charging and discharging processes are revealed, and the energy and exergy efficiencies are calculated to be 93.13 % and 85.62 % with 0.25-h preservation, and 90.46 % and 76.98 % with 4-h preservation, respectively. The exergy loss mechanism of the packed beds during the holding process is revealed. It is found that axial thermal conduction exergy loss accounts for 21.65 % and 7.04 % of the total loss in the packed beds in the full- and low-temperature regions, respectively.