Liquid Air Energy Storage System Research Articles

Parametric analysis and multi-objective optimization of a new combined system of liquid carbon dioxide energy storage and liquid natural gas cold energy power generation

Liquid carbon dioxide energy storage is a potential energy-storage technology. However, it is hindered by the difficulty of condensing CO 2 using high-temperature cooling water because the critical temperature of CO 2 is close to the temperature of the cooling water. Therefore, this study proposes a new combined liquid CO 2 energy storage and two-stage condensation organic Rankine cycle system. Thereby, the condensation of CO 2 is realized, and liquid natural gas (LNG) cold energy is utilized. The impact of key variables on the performance of the system is examined by establishing a mathematical model of the system and analyzing the parameters. In addition, the systems that use pure working fluid and mixed working fluid are optimized and compared using a simultaneous multi-objective optimization method. The results indicate that the system using mixed working fluids is better than that using pure working fluids, with an η R T E of 375.49%, η E X of 81.09%, and LCOS of 0.08 USD/kW·h. The proposed system performs better than the combined liquid air energy storage and LNG cold energy system in the literature from thermodynamic and economic perspectives. • A new combined system of LCES and LNG power generation is proposed. • It improves the difficulty of CO 2 to be condensed by high-temperature cooling water. • The impact of key variables on the performance of the system is explored. • Simultaneous multi-objective optimization method is conducted. • System using pure and mixed working fluid is compared.

Transcritical carbon dioxide cycle as a way to improve the efficiency of a Liquid Air Energy Storage system

The article deals with the subject of energy storage. This important issue relates to the ongoing transformation toward renewable energy sources. Liquid Air Energy Storage (LAES) is a mechanical energy storage technology that is suitable for large-scale energy storage. The article presents a method to increase the efficiency of LAES by coupling it with the transcritical carbon dioxide cycle. To this end, the paper presents a numerical analysis of two Kapitza LAES systems with the transcritical CO2 cycle: in parallel and subsequent mode. In both cases, maximizing CO2 pressure contributes to greater overall efficiency. It is only profitable to direct residual heat to the CO2 cycle. In contrast, lowering the air temperature prior to expansion in hopes of providing a greater amount of heat to the CO2 cycle actually delivers worse results. Parallel system implementation can add 5–6% to storage efficiency, depending on other factors. In comparison, the subsequent system only adds some 3.5%–5% to storage efficiency.

Feasibility and performance analysis of a novel air separation unit with energy storage and air recovery

The high-purity air output by expansion during energy release is discharged into the ambient for liquid air energy storage (LAES) technology, resulting in a large loss of material resources. Currently, LAES research focuses mostly on enhancing thermally driven power generation while disregarding the use of its discharging air. To address this issue, we proposed a novel air separation unit (ASU) with energy storage and air recovery (ASU-ESAR) based on the matching characteristics of air separation and LAES technologies in refrigeration temperature and material utilization. Except for storing liquid air on large-scale by employing ASU and directly recovering cold energy of liquid air, ASU-ESAR has the benefit and novelty of fully recycling high-purity air outputted during energy release, as well as its low temperature and high pressure energy, into ASU. Its process design and feasibility studies are carried out. Energy conservation efficiency, economic benefits, and its influences on China's power grid and emission reductions are assessed. Without any waste heat usage, an electrical round-trip efficiency of 55.82%–58.72% is presented. Taking Shanghai, China as an example, ASU-ESAR's electricity costs are reduced by 5.77%–7.65% when compared to conventional ASU, and the payback period for LAES system with a power capacity of 70.70–74.38 MWh/day is 2.2–2.9 years. The average peak-valley ratio (PVR) of China's power grid might fall by 13% once ASU-ESAR is implemented across the industry, and the yearly CO2 emissions could be reduced by 12.53-27.71 Mt. Its application can achieve a win-win situation of electricity cost savings in ASU operations as well as energy savings and emission reductions on the power generation side.

Liquid air energy storage with effective recovery, storage and utilization of cold energy from liquid air evaporation

Liquid air energy storage (LAES), as a promising grid-scale energy storage technology, can smooth the intermittency of renewable generation and shift the peak load of grids. In the LAES, liquid air is employed to generate power through expansion; meanwhile cold energy released during liquid air evaporation is recovered, stored and later utilized for air liquefaction enhancement. However, it is challenging for effective cold recovery from liquid air in the evaporator and cold utilization to compressed air in the cold box. The current cold recovery fluids are exergy-inefficient, and thus the most suitable cold recovery fluids should be determined. In this paper, a practically dynamic LAES system with cold/heat storage packed beds is studied from the startup to stability. Some common cold recovery fluids, such as air, propane, and methanol/propane, are investigated and compared in terms of heat transfer characteristics in the heat exchangers (i.e., evaporator and cold box) and cold storage packed bed. Simulation results show that using pressurized air (10 MPa) as cold recovery fluid results in high heat transfer coefficients in the heat exchangers and cold storage packed bed. Compared to other fluids, the pressurized air leads to a larger exergy efficiency of 78.2% in the cold box, and a comparable exergy efficiency of 89.6% in the evaporator. It is found that pressurized air and methanol/propane are both good cold recovery fluids in view of the heat transfer performance in the cold box and evaporator, achieving similar idealistic round trip efficiency of 53%. However, the consideration of exergy destruction in packed beds will decline the round trip efficiency to 43% for pressurized air and 38% for methanol/propane. The cold storage packed beds with methanol/propane as cold recovery fluids are easier to be penetrated by thermoclines at the same size of pebbles, which causes a lower round trip efficiency. This study gives new insights into the effective cold recovery, storage and utilization process of LAES for industrial applications.

Optimization of a cryogenic liquid air energy storage system and its optimal thermodynamic performance

For grid-scale intermittent electricity storage, liquid air energy storage (LAES) is considered to be one of the most promising technologies for storing renewable energy. In this study, a steady-state process model was developed for an LAES, by combining a Linde liquefaction process and an open Rankine power cycle. To investigate the system performance and achieve global optimization, a single-factor analysis approach and multifactor genetic algorithm (GA) optimization model were built using MATLAB software. The effects of the charging pressure, storage pressure, discharging pressure, and isentropic efficiency of the compressor/turbine on the LAES performance parameters, such as the inlet temperature of the Joule–Thomson valve, round-trip efficiency (RTE), liquefaction ratio (LR), and power consumptions in the compressor, cryo-pump, and turbine, were investigated. Subsequently, the optimal conditions were obtained using the GA optimization method to achieve the optimal performance of the LAES. The results showed that the charging pressure, discharging pressure, and isentropic efficiencies of the compressor and turbine had significant effects on the RTE; an increase in the discharging pressure resulted in an improved expansion power output; the GA optimization could achieve RTE, LR, the system energy storage and recovery exergy efficiencies of 53.33%, 86.96%, 81.00%, and 78.16%; the power consumption in the compressor of GA optimization was 10.02% maximum saving. The proposed optimization method can be used to further explore the global optimization of cryogenic energy storage systems, such as different-layout LAES systems and different cryogenic liquefaction media energy storage systems.

Energy, exergy, and economic analyses of a new liquid air energy storage system coupled with solar heat and organic Rankine cycle

Liquid air energy storage (LAES) has attracted more and more attention for its high energy storage density and low impact on the environment. However, during the energy release process of the traditional liquid air energy storage (T-LAES) system, due to the limitation of the energy grade, the air compression heat cannot be fully utilized, resulting in a low round trip efficiency (RTE). In addition, coupling solar heat can improve the energy grade of the air during the discharging cycle, which shows a promising prospect. Therefore, a new LAES system coupled with solar heat and organic Rankine cycle (LAES-S-O) is proposed in this paper. Compared with T-LAES system, the thermal oil absorbs solar heat to reheat the air, which improves the output power of the air turbine. Meanwhile, two parts of excess heat of the system are respectively used as heat source to drive organic Rankine cycle (ORC), which greatly improves the RTE of the system. Since the influences of the split fraction (α) of the air compression heat on the system performance are not deeply studied in the previous researches, the factors affecting both the maximum αmax and the minimum αmin are analyzed first. Then the effects of ambient temperature, solar irradiation intensity, energy storage pressure, inlet air temperature of the throttle valve, mass flow rate of the sol-oil and service life on the new system performance are studied with the change of the split fraction. Meanwhile, the energy, exergy and economic performance analyses of the new system are carried out. The results show that the RTE of the new LAES-S-O system is 73.33%, 44.98% higher than that of the T-LAES system. Exergy efficiency of energy storage process and energy release process are 82.71% and 79.18% respectively. The payback period is 9.582 years, the levelized cost of electricity (LCOE) in the lifetime is 0.1434 $/kWh, and the net present value (NPV) is 159.537 million $ over a 30-year period.

Artificial intelligence‐based multi‐objective optimization of a liquid air energy storage system integrated with gas turbine plants for peak shaving

Artificial intelligence‐based multi‐objective optimization of a liquid air energy storage system integrated with gas turbine plants for peak shaving

Techno-economic assessment of a biomass-driven liquid air energy storage (LAES) system for optimal operation with wind turbines

Liquid air energy storage (LAES) is a promising technology for enhancing the quality and stability of renewable power. In this regard, improving the performance of the LAES system has a significant effect on the future of energy systems. The LAES system can be employed for managing the functions of wind power as an important source of renewable energies. In this study, the novel biomass-driven LAES system is designed for power and heat production. A thermoelectric generator (TEG) and domestic hot water (DHW) are used for waste heat recovery in the compression process. Energy, exergy, and economic analysis are applied for evaluating the performance of the system. One kilogram per second of air is compressed by consuming 3964 kWh of power during the charging time and generates 9041 kWh power, and 3795 kWh heat during discharging period with 79.2% energy efficiency and 51.8% exergy efficiency. The gasifier and combustion chamber are responsible for 65% of exergy destruction in the system. The dynamic performance of the system is investigated for the case study of Ireland using actual wind data. Additionally, single-objective optimization shows that the introduced system can provide 2615 MW, 120.4 MW, and 1425 MW constant power for three days in February, July, and December, respectively. The income for electricity generation is 1 M$ for February and December and 20,045 $ for July.

Technical and economic evaluation of a liquid air energy storage system with air precooling for compressor inlet

The intensification of carbon emissions and the energy crisis have made the safe and reliable application of renewable energy in the energy supply system significantly urgent. Liquid air energy storage (LAES) system is an effective means to solve the time and space mismatch between energy supply and demand. The LAES has the advantages of no geographical restrictions, high energy storage density and flexible operation, making it available to integrate with other industrial processes. In traditional LAES, the heat generated in the compression process is used to supplement the heat in the expansion process, and the excess heat is dissipated. In this study, the compressor inlet air is cooled by absorption refrigeration cycle to avoid excess compression heat, which reduces the power consumption of the compressor and improves the efficiency of the system. The sensitivity analysis of the ambient temperature and the compressor stages on the system efficiency is performed. Furthermore, a comparative analysis between the absorption refrigeration cycle driven by the waste heat and the compression refrigeration cycle driven by electricity for air precooling of the compressor inlet was carried out, and the system round-trip efficiency, exergy efficiency and initial investment cost was selected as indicators for system evaluation.

A comparative study of two liquid air energy storage systems with LNG cold energy recovery

Due to the nature of fluctuation and intermittency, the increasing penetration of wind and solar power will bring a huge impact to the power grid management. Therefore the concept of liquid air energy storage system was proposed. Compared to compressed air energy storage, liquid air energy storage has a larger storage capacity and no geographic constraints owing to the high density of liquid air. In order to obtain the optimum system design, two different liquid air energy storage systems with LNG cold energy recovery were studied. For one system, the LNG cold energy was used to precool the compressor inlet air to decrease the compression work. For another one, the LNG cold energy was applied to supplement the cold energy needed to liquefy the air and realize the decoupling between the energy storage and release processes. Thermodynamic analysis based on steady-state mathematical model was employed to evaluate the system performance difference.

Thermodynamic analysis of a liquid air energy storage system with off-peak electric heat storage and reutilization

As a large-scale energy storage technology, liquid air energy storage (LAES) can effectively improve the stability and quality of power grid. However, the traditional LAES has low cycle efficiency, high initial investment and low economic benefits. In order to improve the system performance, a LAES system based on off-peak electric heat storage and high temperature preheating of turbine inlet air was proposed. The thermodynamic characteristics of the LAES system were analyzed, and the energy analysis, exergy analysis and economic evaluation were carried out. Combined with off-peak electric heat storage, the power generation during the peak time by the LAES system can be significantly increased, and the economy of the LAES system can be effectively improved with the peak-valley electricity price difference, especially in areas where the price difference is obvious. The results will be beneficial for the application and promotion of the LAES technology.

Thermodynamic analysis of the non-ideal cryogenic packed bed regenerator for the liquid air energy storage system

Liquid air energy storage (LAES) is one of the most recent technologies introduced for grid-scale energy storage. The cryogenic regenerator, which can greatly affect the system efficiency, is the key component of the system. A non-ideal packed bed regenerator for the LAES system was investigated. The cold energy loss and the axial heat conduction of the packed bed regenerator exist in the intermittent period between the charging and discharging process, which significantly degrades the system performance. With rock particles used as the cold energy storage medium, the axial temperature distributions of the packed bed regenerator with different initial temperatures and intermittent periods were compared. Also, the cold energy loss with different boundary conditions was analysed. The results show that the intermittent period exacerbates the negative impact of the axial heat conduction on the performance of the packed bed, and the thickness of the thermocline decreases as the inlet temperature of the cold end decreases. Moreover, as the cold energy loss increases, the cold energy storage efficiency of the packed bed decreases significantly.

Study on the selection method of solid cold energy storage medium for liquid air energy storage

Liquid air energy storage (LAES) is a promising large-scale energy storage technology. A packed bed cryogenic regenerator was investigated for cold energy storage in the LAES system. As the thermophysical properties of the filling material directly affects the performance of the regenerator, sensitivity analyses of the specific heat capacity and thermal conductivity were carried out. Results show that the thickness of the thermocline in the packed bed can be reduced by increasing the specific heat capacity and decreasing the thermal conductivity. Furthermore, the synergy effect of the specific heat capacity and thermal conductivity on the system was considered. In the case of simultaneous changes of the two parameters, the selection method of the solid material was proposed innovatively, and the feasibility of the method was verified by theoretical calculation of various materials.

Multi-energy flow cooperative dispatch for supply-demand balance of distributed power grid with liquid air energy storage system

It is of great help for alleviating energy shortage and decreasing carbon emission to increase the proportion of renewable energy in energy structure. However, the volatility of renewable energy causes a mismatching for multi-energy flow in distributed micro-grid. To settle this problem, a standalone liquid air energy storage system coupled with cold energy of liquefied natural gas is proposed. A double-parameter regulation method is proposed to make the compressor cope with volatile wind power, and make the expander to meet the variable power demand. To improve the simulation precision, the dynamic behavior of packed bed is investigated and the link between the transient temperature of packed bed and system performance is achieved. The results indicate that the hourly power supply-demand in micro-grid gets balance by employing LAES, and the daily energy storage reaches 285 MWh which is more than enough for the energy demand in peak time (200 MWh). Moreover, the energy storage and supply gets balanced and the round trip efficiency reaches a stable value (63%) in the 8th day. In economic analysis, the short dynamic payback year (5 years) and high net present value (80 million dollars) indicate high economic feasibility. Finally, the proposed system obtains the optimal thermal energy storage density (96 kWh/m3), the minimum work consumption (643 kJ/kg), and the highest round trip efficiency (0.63) compared to those in previous literature.

Liquid Air Energy Storage System (LAES) Assisted by Cryogenic Air Rankine Cycle (ARC)

Energy storage plays a significant role in the rapid transition towards a higher share of renewable energy sources in the electricity generation sector. A liquid air energy storage system (LAES) is one of the most promising large-scale energy technologies presenting several advantages: high volumetric energy density, low storage losses, and an absence of geographical constraints. The disadvantages of LAES systems lay on the high investment cost, large-scale requirements, and low round-trip efficiency. This paper proposes a new configuration using an air Rankine cycle (ARC) to reduce the exergy destruction during heat-exchanging in the liquefaction process while reducing liquefaction power consumption. The addition of the ARC increases the round-trip efficiency of the LAES from 54.1% to 57.1%. Furthermore, the energy consumption per kg of liquid air drops 5.3% in comparison to the base case LAES system. The effects of compression, storage, and pumping pressure on the system performance are investigated by parametric analysis. The results from exergy analysis show that the overall exergy destruction is decreased by 2% and a higher yield of liquid air can be achieved. The results reveal that the increase in the yield of liquid air is more important to the overall efficiency than the power that is generated by the Rankine itself. From an economic viewpoint, the proposed system has a better economic performance than the base case LAES system, decreasing the levelized cost of storage (LCOS) by almost 2%. The proposed configuration may improve the performance and economic competitiveness of LAES systems.

A comprehensive study and multi-criteria optimization of a novel sub-critical liquid air energy storage (SC-LAES)

Liquid air energy storage, as a bulk-scale energy storage technology, has recently attracted much attention for the development and sustainability of smart grids. In the present study, a sub-critical liquid air energy storage system is designed and comprehensively investigated in terms of energy, exergy, environmental, economic, and exergoeconomic. The objective of this design is to minimize the number of equipment in the liquid air energy storage to reduce its structural complexity, increase its applications, improve the performance, and recover waste cold exergy at the liquefied natural gas regasification terminals. Moreover, a fundamental comparison is performed between five storage systems including the proposed system, the conventional liquid air energy storage, and compressed air energy storage by single-stage and two-stage expansion with reheating to highlight the specific characteristics of the proposed system. In addition, using a combination of the artificial neural network and genetic algorithm, optimal design conditions in terms of thermodynamic and economic performance are presented. The proposed system presents a remarkable performance from various points of view compared to other alternatives by storing 27.20 MWh of excess grid power as liquid air during off-peak periods and exploiting it to generate a power of 182.70 MWh at peak demand times. The results show that the electrical efficiency, round trip efficiency, and exergetic round trip efficiency of the system are 563.80%, 77.10%, and 68.80%, respectively. The payback period and net profit of the system in the states of California, USA are around 1.8 years and $ 151 M. At the optimum condition, the round trip efficiency and TOTAL cost rate are 68% and 461 $/h respectively.

Improvement of a liquid air energy storage system: Investigation of performance analysis for novel ambient air conditioning

Liquid air energy storage (LAES) is a grid-scale energy storage technology that utilizes an air liquefaction process to store energy with the potential to solve the limitations of pumped-hydro and compressed air storage. A challenge it faces itself is its high compression work during the charging process. Thus, attempts to increase the performance of the system need to include reducing the compression work. This study investigates the possible performance improvement of a LAES system through inlet air dehumidification and cooling. A simulation is performed on a 40 MW/320 MWhe LAES system which uses a desiccant wheel dehumidifier and a cooling coil for inlet air conditioning. The results show that the system can save 9521 MWhe in compression work annually which will translate to $761,680 annual cost savings in charging the system. The maximum performance improvement achieved during the summer period when the ambient conditions are unfavorable is 11.7%. Financial analysis also shows that the simple payback period of the desiccant wheel dehumidifier modification is 11.5 years and the levelized cost of storage (LCOS) of the LAES system is $237/MWh which is competitive compared to other storage systems.

Dynamic simulation and techno-economic analysis of liquid air energy storage with cascade phase change materials as a cold storage system

Liquid air energy storage (LAES) is a promising solution for overcoming the challenge of intermittency in renewable-based energy systems. Cold recovery is the most important part of the LAES and plays a vital role in the performance of the system. In this study, the LAES system which utilizes a packed bed thermal energy storage (PBTES) comprising three-layer phase change materials (PCM) is investigated from a thermodynamic and economic point of view. As a result of the transient nature of PBTES the dynamic modeling is applied to analyze the performance of the system. The designed LAES system with ideal condition consumes 4.42 MWh for compressing the air and generates 1.8 MWh of electricity during the peak time. The payback period of the system for the case study of San Fransico is 6.7 years with 0.66 M$ total profit. As a dynamic behavior of the system liquid yield, the mass flow rate of liquid air, the specific work of the compressors, and the cryo turbine vary during different cycles. After about 22 cycles system with a total efficiency of 42.5% reaches the equilibrium and the performance of the system decrease about 5.9% because of transient behavior in comparison with the ideal cycle.

A novel liquid air energy storage system using a combination of sensible and latent heat storage

This paper proposes a novel stand-alone liquid air energy storage (LAES) system to enhance round-trip efficiency (RTE) using a thermal energy storage system. Thermal energy storage comprises sensible heat storage with quartz and latent heat storage with cryogenic phase change material (PCM) for recycling cold energy from the LAES discharge process. The liquid air in the pressurized tank was released during the discharge cycle and used to store energy using PCM and quartz. The cryogenic phase change material melts at 110 K based on experimental result, making it possible to provide cold heat of fusion 61.62 kJ/kg at a constant temperature for air liquefaction. Thus, proposed system can effectively increase the cold energy recycle. In addition, the two-dimension numerical model allowed us to estimate the outlet temperature of sensible heat store without isothermal assumption by Biot Number. The proposed process is modified from Linde-Hampson, and a sensitivity analysis is performed using ASPEN HYSYS. The analysis shows that the implementation of energy recycling from the compressor and thermal store leads to a high round-trip efficiency (60.6%) higher than base case (34.4%) of LAES system. Therefore, the proposed system is a promising process in terms of simplification and high efficiency, cognizant of the integration of waste heat from industrial plants.

Experimental investigation of tank stratification in liquid air energy storage (LAES) system

Liquid air energy storage technology is a technology that stores liquid air in case of excess power supply and evaporates the stored liquid air to start a power generation cycle when there is an electric power demand. When liquid air is stored for a long-time during operation, safety and performance degradation can be caused or mitigated by the tank stratification. To investigate the tank stratification phenomenon and associated issues, an experimental facility is constructed. The heat ingress is controlled with respect to changing vacuum level in the experiment. Furthermore, the conditions under which stratification occurs are defined in terms of temperature and concentration, and based on this, the stratification stability ratio and the stability map are defined and evaluated experimentally. The results show that the time required for destratification is 8–29% shorter for liquid air mixture cases than for liquid nitrogen. Moreover, the time required for destratification is 2.4 times longer for the high tank pressure cases, and it is 39% shorter for the case of high heat ingress. From experimental observations, an operation strategy utilizing stratification inside the liquid air storage tank is newly suggested that can minimize the boil-off gas of liquid air in the tank.