Advanced Adiabatic Compressed Air Energy Research Articles

Modelling and experimental validation of advanced adiabatic compressed air energy storage with off‐design heat exchanger

Advanced adiabatic compressed air energy storage (AA-CAES) has been recognised as a promising approach to boost the integration of renewables in the form of electricity and heat in integrated energy systems. Nevertheless, the uncertainty and variability of renewables spark the consideration of the off-design thermodynamics of AA-CAES, particularly when the heat exchanger is equipped to collect and recycle air-compression heat. Here, the authors propose a general off-design thermodynamic simulation model of AA-CAES incorporating the part-load characteristics of heat exchangers, and validate the effectiveness of the proposed model on a practical AA-CAES demonstration pilot. The results indicate that the simulation model offers an acceptable approximation for the practical operation behaviour of AA-CAES facility and decreases the modelling error from 20.8 to 6.28% compared with the existing model. The proposed simulation model is expected to provide insights into the investigation of the dynamic characteristics of AA-CAES in the future integrated energy system.

Performance of compressed air energy storage system with regenerative heat exchangers

In order to improve the heat storage and heat exchange system of advanced adiabatic compressed air energy storage (AA-CAES) system, an AA-CAES system with regenerative heat exchangers (RHEs) is studied. The RHE is used to replace the conventional complex units, including heat exchangers, high temperature tank, and low temperature tank mode. For the AA-CAES with RHEs, the energy storage system is simplified to reduce the heat loss in the heat exchange and storage processes, and thus, the output work, energy storage density, energy storage efficiency of the system are improved. The thermodynamic model is established and the influences of compression ratio distribution, expansion ratio distribution and ambient temperature on the system performance are investigated. The results show that for the AA-CAES with RHEs, when the ratio of compression ratios is 1.14, the input work of the compressor is the minimum, the energy storage efficiency is 66.42%, and the energy storage density is 3.61 kWh/m3. When the ratio of expansion ratios is 0.82, the energy storage efficiency reaches the maximum value of 67.38%, and the energy storage density reaches the maximum value of 3.66 kWh/m3.

Thermodynamic simulation of a micro advanced adiabatic compressed air energy storage for building application

In the context of developing renewable energies, storing energy improves energy efficiency and promotes the insertion of intermittent renewable energies. It consists of accumulating energy for later use in a place that may be the same or different from the place of production. Converting electrical energy to high-pressure air seems a promising solution in the energy storage field: it is characterized by a high reliability, low environmental impact and a remarkable energy density. This article carries out a novel numerical global model of micro advanced adiabatic compressed air energy storage based on thermodynamic and energy analysis of components available commercially in the market: photovoltaic panels coupled to building model and storage system. This model allows to study multiple sizing parameters (solar surface, storage volume, geographical locations, compression/expansion ratio) based on energy production (renewable energy, grid) and energy storage technology. The results show an interesting energy part of 64% that answered the total building electric energy consumption based on solar production and energy resulted from storage. Levelized cost of energy analysis is also provided to highlight the influence of the critical parameter in the context of developing a micro compressed air energy storage system based on commercial units available in the market.

Performance assessment of a hybrid solid oxide and molten carbonate fuel cell system with compressed air energy storage under different power demands

As electricity demand can vary considerably and unpredictably, it is necessary to integrate energy storage with power generation systems. This study investigates a solid oxide and molten carbonate fuel cell system integrated with a gas turbine (GT) for power generation. The advanced adiabatic compressed air energy storage (AA-CAES) system is designed to enhance the system flexibility. Simulations of the proposed power system are performed to demonstrate the amount of power that can supply to the loads during normal and peak modes of operation under steady-state conditions. The pressure ratios of the GT and AA-CAES and the additional air feed are used to design the system and analyze the system performance. The results show that a small additional air feed to the GT is certainly required for the hybrid system. The GT pressure ratio of 2 provides a maximum benefit. The AA-CAES pressure ratio of 5 is recommended to spare some air in the storage and minimize storage volume. Moreover, implementation of the GT and AA-CAES into the integrated fuel cell system allows the system to cope with the variations in power demand.

Combined Heat and Power dispatch considering Advanced Adiabatic Compressed Air Energy Storage for wind power accommodation

As an attractive large-scale clean energy storage technique, Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) can store and generate both electricity and heat, which has great application potentials in Integrated Electricity and Heating Systems (IEHSs). However, few studies have been reported on Combined Heat and Power (CHP) dispatch by implementing AA-CAES in IEHS. This paper presents a CHP dispatch model considering the participation of AA-CAES for IEHS and mitigating wind curtailment. The mathematical model of AA-CAES for CHP dispatch is developed based on Mixed Integer Linear Programming (MILP). The off-design characteristic of AA-CAES is considered in the modelling process. The benefits of AA-CAES for mitigating wind curtailment and decreasing operation costs in IEHS has been studied. The scheduling analysis based on the developed model and the existing model without considering off-design characteristics has been carried out. The study shows that the participation of AA-CAES in CHP dispatch can increase the flexibility of IEHS, and it can lead to an apparent reduction of wind curtailment and operation costs. Also, AA-CAES’s off-design conditions need to be considered in the dispatch; otherwise it can cause the misjudgment of AA-CAES’s state of charge, which in turn results in costly operation.

Numerical Model of Time-Dependent Gas Flows Through Bed of Granular Phase Change Material

A novel mathematical model and original numerical method for investigating time-dependent gas flows through a bed of granular phase change material (PCM) are proposed and described in detail. Such material is modeled as a porous medium, and continua mechanics method are used for constructing the mathematical model. The numerical method is based on a combination of explicit and implicit finite-difference schemes. Comparison of calculation results with known experimental data demonstrates a very good coincidence. The results of the study can be applied in modeling the thermal energy storage with granular PCM in advanced adiabatic compressed air energy storage and other heat storage devices.

Comparison Analysis of Different Compressed Air Energy Storage Systems

Based on the theory of thermodynamics, several compressed air energy storage (CAES) systems with different heat sources are proposed by our team to study the efficiency issues of CAES. The study focuses on the waste heat recovery and compression heat utilization. By adopting the round-trip efficiency as evaluating indicator, the performances of these systems are compared. The results indicate that the waste heat recovery is beneficial to improve system efficiency. The compression heat can replace the heat of combustion to preheat the compressed air before entering turbines. For advanced adiabatic compressed air energy storage (AA-CAES) system, it has better system efficiency and smaller capability. But the waste heat from exhaust gas has little influence on system efficiency when compared with conventional CAES.

Investigation of discharge characteristics of a tri-generative system based on advanced adiabatic compressed air energy storage

The tri-generative system based on advanced adiabatic compressed air energy storage can simultaneously provide cooling energy, heating energy and mechanical energy. In order to study the discharge characteristics, three operation modes of expanders, which contain constant pressure, constant-sliding and sliding pressure, are proposed in this paper. By utilizing the numerical simulation method, the performance difference of three modes is compared with each other. The results show that four performance indexes of constant-sliding mode are all the biggest, which are respectively cycle efficiency 40.55%, thermal efficiency 80.06%, exergy efficiency 48.45% and exergy density 4.071 × 106 J·m−3, and cooling capacity of it is also the strongest, 8.386 × 109 J, among the three operation modes. Air storage chamber has the largest exergy destruction. Operation process of air storage chamber is similar for three operation modes. Meanwhile, the effects of heat exchanger effectiveness, ambient pressure and air storage chamber model on system performance are also investigated.

Thermodynamic analyses and multi-objective optimization of operation mode of advanced adiabatic compressed air energy storage system

Advanced adiabatic compressed air energy storage system plays an important role in smoothing out the fluctuated power from renewable energy. Under different operation modes of charge-discharge process, thermodynamic behavior of system will vary. In order to optimize system performance, four operation modes of charge-discharge process are proposed in this paper. The performance difference of four modes is compared with each other based on energy analysis and exergy analysis. The results show that exergy efficiency of mode 4 is the highest, 55.71%, and exergy density of mode 2 is the largest, 8.09 × 106 J m−3, when design parameters of system are identical. The second heat exchanger has the most improvement potential in elevating system performance. In addition, a parametric analysis and multi-objective optimization are also carried out to assess the effects of several key parameters on system performance.

A reserve capacity model of AA-CAES for power system optimal joint energy and reserve scheduling

Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) has received much attention in the recent years due to its merits of no fossil fuel consumption, low costs, fast start-up and wide-ranging part load ability. It is considered to have a variety of power gird applications including providing reserve services. Although a number of studies are reported in the optimal scheduling strategy of using compressed air energy storage, very few studies have been reported in AA-CAES reserve capacity modelling. This paper presents a reserve capacity model for an AA-CAES facility considering its working mode conversion process, the dynamic characteristics, the air pressure limitations, the thermal storage capacity limitations and the power output limitations of AA-CAES. The developed reserve capacity model is then used in the power system optimal joint energy and reserve scheduling. In the scheduling, the limits on the reserve capacities of Thermal Power Units (TUs) and Interruptible Loads (ILs), which are caused by AA-CAES, are taken into account. The developed scheduling model are used to analyse the impacts of AA-CAES on the system energy and reserve schedules, the system operation costs and the wind curtailment. Numerical simulation results indicate that the participation of AA-CAES in power system operation does not only reduce the system energy and reserve costs, but also mitigate the wind curtailment. However, it is found that AA-CAES is unsuitable for undertaking the system reserve demand alone and using AA-CAES to provide reserve services may increase the system total reserve demand.

Investigation of operation strategy of combined cooling, heating and power(CCHP) system based on advanced adiabatic compressed air energy storage

Combined cooling, heating and power(CCHP) system can meet the diversified demand of users. To investigate the performance of CCHP system based on advanced adiabatic compressed air energy storage(AA-CAES) under different operation strategies, four operation scenarios of compressor-expander, which are respectively constant-constant, constant-sliding, sliding-constant, and sliding-sliding, are proposed in this paper. By employing the numerical simulation method, system performance of four scenarios is compared via energy analysis and exergy analysis. Meanwhile, a parametric analysis is conducted to evaluate the influence of key parameters on system performance. The results show that cycle efficiency, thermal efficiency and exergy efficiency of sliding-sliding scenario are all the highest, 48.31%, 91.04% and 56.48%, respectively. And exergy density of constant-sliding scenario is the biggest, 7.69 × 106 J m−3, when design parameters of system are the same. In addition, second heat exchanger makes the largest contribution to the overall exergy destruction of system. For the four operation scenarios, with heat exchanger effectiveness increasing, cycle efficiencies exist optimal values, whereas thermal efficiencies, exergy efficiencies and exergy densities gradually augment. The influence of ambient temperature on different performance indexes is different. The increase of ambient pressure has negative effect on exergy densities, but it has positive effect on other performance indexes.

Thermostatic properties of nitrate molten salts and their solar and eutectic mixtures

Nitrate molten salts are extensively used for sensible heat storage in Concentrated Solar Power (CSP) plants and thermal energy storage (TES) systems. They are the most promising materials for latent heat storage applications. By combining classical molecular dynamics and differential scanning calorimetry experiments, we present a systematic study of all thermostatic, high temperature properties of pure KNO3 and NaNO3 salts and their eutectic and ”solar salt” mixtures, technologically relevant. We first study, in solid and liquid regimes, their mass densities, enthalpies, thermal expansion coefficients and isothermal compressibilities. We then analyze the cP and cV specific heats of the pure salts and of the liquid phase of the mixtures. Our theoretical results allow to resolve a long-standing experimental uncertainty about the cP(T) thermal behaviour of these systems. In particular, they revisit empirical laws on the cP(T) behaviour, extensively used at industrial level in the design of TES components employing the ”solar salt” as main storage material. Our findings, numerically precise and internally consistent, can be used as a reference for the development of innovative nanomaterials based on nitrate molten salts, crucial in technologies as CSP, waste heat recovery, and advanced adiabatic compressed air energy storage.

Pilot-scale demonstration of advanced adiabatic compressed air energy storage, Part 2: Tests with combined sensible/latent thermal-energy storage

Abstract Experimental and numerical results from the world’s first pilot-scale advanced adiabatic compressed air energy storage plant with combined sensible/latent thermal-energy storage are presented. The combined thermal-energy storage was composed of sensible and latent units with maximum capacities of 11.6 MWhth and 171.5 kWhth, respectively. The latent thermal-energy storage consisted of a steel tank with 296 stainless-steel tubes encapsulating an Al–Cu–Si alloy as phase-change material. The combined thermal-energy storage was investigated using four charging/discharging cycles with durations of about 3 h each and air inflow temperatures of up to 566 °C. The experimental results showed that the latent thermal-energy storage reduced the drop in the air outflow temperature during discharging. Minor leaks of the phase-change material were traced to the welding seams in the encapsulation as well as to holes required to insert resistance temperature detectors. Analysis of the leaked phase-change material revealed degradation and/or phase separation, which were attributed to the initial off-eutectic composition of and impurities in the phase-change material and resulted in a reduced heat of fusion. Simulations predicted the performance of the combined thermal-energy storage with good overall accuracy. Discrepancies were put down to changes in the thermophysical properties.

Pilot-scale demonstration of advanced adiabatic compressed air energy storage, Part 1: Plant description and tests with sensible thermal-energy storage

Abstract Experimental and numerical results from the world's first advanced adiabatic compressed air energy storage (AA-CAES) pilot-scale plant are presented. The plant was built in an unused tunnel with a diameter of 4.9 m in which two concrete plugs delimited a mostly unlined cavern of 120 m length. The sensible thermal-energy storage (TES) with a capacity of 12 MWhth was placed inside the cavern. The pilot plant was operated with charging/discharging cycles of various durations, air temperatures of up to 550 °C, and maximum cavern gauge pressures of 7 bar. Higher pressures could not be reached because of leaks that were traced mainly to the concrete plugs. Simulations using a coupled model of the TES and cavern showed good agreement with measurements. Cycle energy efficiencies of the TES were determined to lie between 76% and 90%. The estimated round-trip efficiency of the pilot plant was based on the measured TES performance and estimated performances of the other components, yielding values of 63–74%, which compares favorably with the usually quoted values of 60–75% for prospective AA-CAES plants.

Comparison of underwater and underground CAES systems for integrating floating offshore wind farms

Floating offshore wind farms (FOWF) with advanced adiabatic compressed air energy storage (AA-CAES) are thermodynamically scrutinized to evaluate if the compressed air is better stored underground or underwater. The corresponding energy efficiency is deduced based on an exergy analysis that details the exergy destruction of each system. The effects of key parameters such as storage and expansion pressures are examined parametrically. It is revealed the underwater compressed air energy storage has a higher efficiency and exergy density. These advantages tend to diminish beyond a critical storage pressure.

Numerical investigation of a joint approach to thermal energy storage and compressed air energy storage in aquifers

Different from conventional compressed air energy storage (CAES) systems, the advanced adiabatic compressed air energy storage (AA-CAES) system can store the compression heat which can be used to reheat air during the electricity generation stage. Thus, AA-CAES system can achieve a higher energy storage efficiency. Similar to the AA-CAES system, a compressed air energy storage in aquifers (CAESA) system, which is integrated with an aquifer thermal energy storage (ATES) could possibly achieve the same objective. In order to investigate the impact of ATES on the performance of CAESA, different injection air temperature schemes are designed and analyzed by using numerical simulations. Key parameters relative to energy recovery efficiencies of the different injection schemes, such as pressure distribution and temperature variation within the aquifers as well as energy flow rate in the injection well, are also investigated in this study. The simulations show that, although different injection schemes have a similar overall energy recovery efficiency (∼97%) as well as a thermal energy recovery efficiency (∼79.2%), the higher injection air temperature has a higher energy storage capability. Our results show the total energy storage for the injection air temperature at 80°C is about 10% greater than the base model scheme at 40°C. Sensitivity analysis reveal that permeability of the reservoir boundary could have significant impact on the system performance. However, other hydrodynamic and thermodynamic properties, such as the storage reservoir permeability, thermal conductivity, rock grain specific heat and rock grain density, have little impact on storage capability and the energy flow rate. Overall, our study suggests that the combination of ATES and CAESA can help keep the high efficiency of energy storage so as to make CAESA system more efficiency.

Performance Study of an Advanced Adiabatic Compressed Air Energy Storage System

Renewable energy sources such as wind and solar, have vast potential to offer cost competitive power supply and reduce dependence on fossil fuels and environmental issues in the electric sector. However, renewable energy systems often have variable and uncertain energy supply which makes electrical energy storage systems highly valuable for renewable energy applications. Compressed air energy storage is one of the most promising technologies that have received wide attention in scientific community. In this paper, a comprehensive thermodynamic model is developed to investigate the thermal performance of an Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) system. The effect of key parameters including storage pressure, pre-set pressure along with compressor and turbine efficiencies on the system performance is studied. The results show that the storage pressure has a significant effect on the amount of energy stored in the AA-CAES and power generated by the expander. As the storage pressure increases from 2 MPa to 10 MPa, the amount of energy stored increases from 7.8 MJ/m3 to 105.6 MJ/m3 while the output power increases from 4.2 to 63.2 MJ/m3. The results also show that the overall energy conversion efficiency is dominated by the efficiency of the compressor and turbine. As the efficiencies of both compressor and expander increases from 0.65 to 0.95, the efficiency of the AA-CAES system is improved from 35% to 74%. This study provides a deep understanding of operation characteristics of the AA-CAES system and useful information for system design and optimization.

Designing and optimizing a novel advanced adiabatic compressed air energy storage and air source heat pump based μ-Combined Cooling, heating and power system

This paper presents the design and optimum scheduling of a solar CCHP (combined cool, heat and power) system which is powered by a Stirling engine in the presence of an AA-CAES (advanced adiabatic compressed air energy storage) system for a residential energy sector. An absorber and a thermal energy storage tank are employed to absorb and store all collected solar radiation for continuous energy supplied when sunlight is insufficient, and nighttime. In this paper, an ASHP (air source heat pump) that is equipped with two inside and outside air fans, an expansion valve, compressor, condenser and an evaporator is installed to cool and heat a benchmark residential building under hot and cold climate conditions, respectively. The AA-CAES system is modeled with injected and produced power constraints, storage, air balance and operation limits. A comprehensive energy and exergy based optimization is developed as a mixed-integer nonlinear program to minimize total energy procurement cost in the presence of ASHP, prime mover and AA-CAES's constraints. It is found that the use of AA-CAES results in 21.79% and 22.36% lower operational costs in the cooling and the heating modes, respectively.

Thermodynamic analysis of a novel energy storage system with carbon dioxide as working fluid

Recently, energy storage system (ESS) with carbon dioxide (CO2) as working fluid has been proposed as a new method to deal with the application restrictions of Compressed Air Energy Storage (CAES) technology, such as dependence on geological formations and low energy storage density. A novel ESS named as Compressed CO2 Energy Storage (CCES) based on transcritical CO2 Brayton cycle is presented in this paper. The working principle of CCES system is introduced and thermodynamic model is established to assess the system performance. Parametric analysis is carried out to study the effect of some key parameters on system performance. Results show that the increase of turbine efficiency is more favorable for system optimization and the effect of minimum pressures on system performance is more significant compared with maximum pressures. A simple comparison of CCES system, liquid CO2 system and Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) system is conducted. It is shown that the system efficiency of CCES is lower than that of AA-CAES system but 4.05% higher than that of liquid CO2 system, while the energy density of CCES system is 2.8 times the value of AA-CAES system, which makes CCES a novel ESS with potential application.

Advanced Rock Drilling Technologies Using High Laser Power

Drilling through hard rock formations causes high mechanical wear and most often environmental disturbance. For the realization of an Advanced Adiabatic Compressed Air Energy Storage (AA-CAES) power plant a new and efficient method for tunneling utilising laser technology to support mechanical ablation of rock formations will be developed. Laser irradiation of inhomogeneous rock surfaces causes irregular thermal expansion leading to the formation of cracks and splintering as well as melting and slag-formation. This study focuses on the interaction of laser irradiation with calcite, porphyrite and siderite rock formations. A high power disc laser system at 1030nm wavelength is used to investigate the specific energy necessary to remove a unit volume depending on interaction times and applied power. Specific energies have been measured and an increase of fragility and brittleness of the rock surface has been observed.