Adiabatic System Research Articles

Design and thermodynamic performance analysis of a novel adiabatic compressed air energy storage system based on liquid piston re-pressurization

Compressed air energy storage (CAES) is a crucial technology for integrating renewable energy into the grid and supporting the “dual carbon” goals. To further utilize compressed heat and reduce throttling losses, this paper proposes a novel A-CAES energy storage system with liquid piston re-pressurization (LP-A-CAES). During the energy release process, the air in the air storage tank enters the liquid piston directly without passing through the throttle valve, then undergoes further pressurization and expansion. This approach avoids throttling losses while increasing the expansion ratio of the expander, facilitating the efficient use of compressed heat. By establishing thermodynamic models for both the proposed re-pressurized A-CAES and the traditional A-CAES systems, we compare their performance variations with changes in key parameters. Results indicate that under design conditions, the system's energy efficiency is 70.74 %, a 5.07 % improvement over traditional throttle-based A-CAES systems. The total exergy loss of the system is 1.42 × 1010 J, with the compressor and expander units accounting for the largest exergy losses, at 32 % and 31.6 %, respectively. The liquid piston exhibits excellent isothermal performance, maintaining air and water temperature rises within 20 K and 2.5 K, respectively. Reducing the maximum pressure difference in the air storage tank enhances system performance, although the performance improvement of the re-pressurized A-CAES system compared to the traditional A-CAES system diminishes. Increasing the height of the thermal energy storage and reducing the diameter of the thermal storage material both contribute to higher system energy efficiency. When the height of the thermal energy storage increases from 4 m to 8 m, the system's efficiency rises from 70.04 % to 70.74 %. Similarly, reducing the diameter of the thermal storage material from 0.05 m to 0.01 m increases the system's efficiency from 68.85 % to 71.47 %.

Simulation study of a novel approach to couple compressed CO2 energy storage with compression heat storage in aquifers

The integration of energy storage systems is essential for addressing the limitations of renewable energy generation, such as intermittency and fluctuations. This study introduces a porous media adiabatic compressed CO2 energy storage system (PM-ACCES) that combines thermal energy storage with compressed CO2 energy storage within aquifers at different depths. PM-ACCES aims to reduce the overall system complexity by eliminating the need for thermal storage systems at the ground level to store compression heat, while simultaneously integrating CO2 energy storage with sequestration. Through comprehensive numerical simulations and thermodynamic modelling, the study evaluates the performance of the PM-ACCES system under various operating conditions. The results show that, under the default conditions of this study, the average discharge power and charge power of the PM-ACCES with solar heating over 30 days are 4663.7 kW and 2342.9 kW, respectively, with a corresponding discharge capacity of 18,655 kWh and a charge capacity of 23,429 kWh. The PM-ACCES system can operate without external heat sources, achieving a discharge power of 3045.31 kW and a discharge capacity of 12,156 kWh, while attaining a higher round-trip efficiency of 51.93 %. Additionally, the study examined various factors affecting the energy storage performance of the solar-heated PM-ACCES. The findings suggest that improving wellbore thermal insulation and utilizing deeper aquifers can significantly enhance energy storage performance. However, increasing the circulation flow rate, while boosting charge and discharge power, reduces the round-trip efficiency. These findings provide a robust foundation for future optimization of CO2-based energy storage systems, offering a promising solution for integrating renewable energy into the power grid.

Modelling of a continuous sorption-enhanced methanation process in an adiabatic packed-bed reactor system

The present study investigates a sorption-enhanced methanation process and successive solid regeneration stages using a dual-function catalyst containing nickel as a catalyst and zeolite 13X for water removal. An adiabatic packed bed, modelled by a dynamical and heterogeneous model, has been considered, and a five-stage sequence describes the sorption-enhanced methanation and successive solid regeneration. First, methanation occurs with in-situ water removal; then, the catalyst drying using a pressure and temperature swing approach implemented by blowdown, purge, cooling, and pressurisation stages. In adiabatic operation, heat management is crucial; on the other hand, the heat produced can be efficiently used to dry the zeolite. Process intensification is pursued by addressing the effect of gas inlet temperature, pressure, and GHSV on system performance. Achieving an average purity of 99 % of the methane for pressures greater than 2 bar is possible for long-time operation, with productivity averaging 0.8 mol/(kgads min) at the highest gas hourly space velocity investigated.

Thermodynamic analysis of an advanced adiabatic compressed air energy storage system integrated with a high-temperature thermal energy storage and an Organic Rankine Cycle

Advanced adiabatic compressed air energy storage (AA-CAES) system has drawn great attention owing to its large-scale energy storage capacity, long lifespan, and environmental friendliness. However, the performance of the air turbine during the discharging process is limited by the low temperature of the compression heat. Thus, this study proposes an integrated AA-CAES system incorporating high-temperature thermal energy storage and an Organic Rankine Cycle (ORC). The high-temperature thermal energy storage is introduced to heat the discharging compressed air to enhance the air turbine performance, and the Organic Rankine Cycle is integrated to utilize the waste heat. Notably, two preheaters are deployed in a special tandem to recover the heat from the air exiting the turbine and the water exiting the hot water tank, respectively. This paper develops a thermodynamic model to simulate the proposed system, assessing the effects of heat storage temperature, ambient temperature, and inlet conditions of the air turbine on performance metrics, including exergy efficiency and exergy destruction. The simulation results indicate that, compared to thermal oil and Hitec salt, employing solar salt as the heat storage medium for the solar thermal collection and storage unit yields the best performance. The energy storage efficiency, roundtrip efficiency, exergy efficiency, exergy conversion coefficient, and energy storage density of this system are 115.6 %, 65.7 %, 78 %, 79.4 %, and 5.51 kWh/m3, respectively. Exergy analysis reveals that the exergy efficiency of interheaters (IH) is the lowest at 76.7 %, while air turbines (ATBs) exhibit the highest exergy efficiency at 91.2 %. Moreover, due to the irreversible processes of compression, expansion, and throttling, ATBS, compressors, and throttle valves collectively contribute to an exergy destruction rate as high as 79.2 %. The parameter analysis demonstrates that low ambient temperature, high inlet temperature, and high inlet pressure of the air turbine enhance energy storage performance.

Dynamic analysis of an adiabatic compressed air energy storage system with temperature-regulated in air tanks

In this study, an innovative temperature regulation method is developed to augment the air storage capacity of adiabatic compressed air energy storage. Hot water, produced by recovering waste heat from the discharging process, is injected into these tanks to control the air temperature as needed. The transient-state calculation models have been established for each component, and validation is performed using experimental data obtained from published work. The utilization of proportion integration differentiation control technology enables precise regulation of the air outlet temperature of heat exchangers, achieving a control accuracy of 1K. The operational status of the components has been investigated, and a comparison is made between the performances of the modified and traditional adiabatic compressed air energy storage systems. The comparative analysis results show that the modified system can achieve a notable round trip efficiency of 71.71 %, which is comparable to that of conventional system (71.41 %). The effective air storage density of the modified system is 47.24 kg/m3, which presents a 15.08 % increase compared to traditional system (41.05 kg/m3). The influence of discharge pressure and pressure difference between threshold pressure and discharge pressure is also investigated. It is found that the modified adiabatic compressed air energy storage shows a consistently greater effective air storage density than traditional system, with a minimum increase exceeding 10.52 %.

Design and performance optimization of a novel CAES system integrated with coaxial casing geothermal utilization

At present, the heat storage sub-system in the adiabatic compressed air energy storage system generally has low heat storage density and limited heat storage temperature, resulting in mediocre power generation efficiency of the system. To address these issues, this paper proposes a novel approach for coupling the energy storage system with geothermal energy utilization. This study innovatively uses coaxial casing wells to extract geothermal energy and to preheat compressed air in front of the expander. Detailed numerical investigations and dynamic thermodynamic analysis are carried out to evaluate system performance. Sensitivity and optimization are analyzed to identify the operational and design parameters of the proposed system. In addition, an economic analysis is conducted to estimate the investment and payback of the energy storage system. The results show that geothermal energy utilization can directly and significantly enhance the electric, heating and cooling energy output of compressed air energy storage system. During one 24-hours operation cycle, the electricity output is 104.45GJ, the heating supply output is 81.59 GJ, and the cooling supply output is 16.69 GJ. The RTE and energy efficiency are 64.26 % and 122.68 %, respectively. Economic analysis shows that the static payback period is 12.17 years, and the net present value can reach 3.46 million USD. It can be concluded that geothermal energy plays a greater role in energy storage systems than geothermal power production alone. The compressed air energy storage system combined with geothermal energy addresses current issues and leads to improved system performance.

Investigation of temperature gradient effects and effective thermal inertia during adiabatic decomposition of substances with varying exothermic characteristics

To further study adiabatic parameters distortion, the adiabatic decomposition of 2,4-DNT, 20%DTBP, and 45%Glucose was systematically analyzed using thermal analysis calorimetry and numerical simulation methods. The study revealed the variation laws and influence mechanisms of the temperature gradient effects and thermal inertia in adiabatic systems. A numerical model for decomposition in a closed adiabatic system was developed by integrating the apparent kinetics into the CFD code. The results show that the temperature gradient effects during adiabatic decomposition initially increase and then decrease until reaching zero. The temperature gradient effects become more pronounced as the exothermic characteristics of substances increase. They are the most significant at the peak self-heating rate, with gradients of 182.4 °C·cm−1, 21.6 °C·cm−1, and 0.78 °C·cm−1, respectively. Specific data segments for adiabatic analysis should maintain α values below 0.138 for 2,4-DNT, 0.484 for 20%DTBP, and should utilize complete 100 % adiabatic data for 45%Glucose, aiming to mitigate potential distortion in adiabatic parameters. Furthermore, Фeff varies with the reaction, initially increasing and then decreasing in deviation from the theoretical value, with peak deviations of 60 %, 20 %, and 0.3 % for three substances, respectively. These findings lay the foundation for further optimizing the temperature gradient effects and establishing a dynamic Фeff correction model.

Design of Underwater Compressed Air Flexible Airbag Energy Storage Device and Experimental Study of Physical Model in Pool

Renewable energy is a prominent area of research within the energy sector, and the storage of renewable energy represents an efficient method for its utilization. There are various energy storage methods available, among which compressed air energy storage stands out due to its large capacity and cost-effective working medium. While land-based compressed air energy storage power stations have been constructed worldwide, their efficiency remains low. Underwater compressed air energy storage has the potential to significantly enhance efficiency, although no such device currently exists. This paper presents the design of an UWCA-FABESD utilizing five flexible air bags for underwater gas storage and discharge. Additionally, it introduces the working principle of the adiabatic underwater compressed air energy storage system and device. Furthermore, a small-scale physical model with similar functionality was designed and manufactured to simulate the charging process of the air bag in onshore charging and discharging tests as well as posture adjustment and lifting arrangement tests, along with underwater charging and discharging tests. These experiments validated the related functions of the designed underwater compressed air flexible bag energy storage device while proposing methods for its improvement. This research provides a new approach to underwater compressed air energy storage.

Multi-perspective analysis of adiabatic compressed air energy storage system with cascaded packed bed latent heat storage under variable conditions

Adiabatic compressed air energy storage (A-CAES) with advanced thermal energy storage systems has enormous potential in applications. In particular, the extent of thermal energy utilization determines the comprehensive performance of an A-CAES system. In this paper, a cascaded latent heat packed bed storage system is used as a thermal energy storage under variable conditions of A-CAES. The transient thermal characteristic of the packed bed under variable conditions are further studied. Moreover, the key parameters that affect the thermal energy utilization of the system are also parametrically investigated. The results show that the proposed system has a roundtrip efficiency of 63.42 %, an exergy efficiency of 66.58 %, and a payback period of 4.63 years. The economic analysis shows that the proposed system is more advantageous in comparison with A-CAES with heat transfer oil as heat storage system.

Design and operation of an adiabatic compressed air energy storage system incorporating a detailed heat exchanger model

Heat exchangers (HEXs) are among the key components of adiabatic compressed air energy storage (A-CAES) systems. However, the existing HEX models applied in the A-CAES systems are overly simplistic, limiting research regarding design and operational simulation. For the first time, this study incorporates a comprehensive HEX model, including calculations for geometric dimensioning, heat transfer, and pressure drop, into the A-CAES system model; in addition, a novel layered, interactive system design and operational simulation algorithms are developed. The developed models and algorithms can facilitate the design process and yield reasonable operational simulation results with only basic parameters. The design algorithm can determine all key parameters of the system and assess the effect of the HEX pressure drop and heat transfer area on the system performance. The operational simulation algorithm considers the performance of all key equipment under off-design conditions. The design exergy efficiency and daily net income of the system are 73.15 % and $26,998, respectively; however, these values decrease during operation to 72.15 % and $25,034, respectively. A comprehensive analysis of the key parameters during operation revealed that the primary causes for the degradation were the sliding pressure in the energy storage process and variations in the air storage tank parameters.

Effect of geothermal heat transfer on performance of the adiabatic compressed air energy storage systems with the salt cavern gas storage

The temperature and pressure of compressed air influence the output performance of the adiabatic compressed air energy storage system with salt cavern gas storage. However, current studies often overlook the impact of geothermal heat transfer on system performance. In this paper, a mathematical model of the energy storage system with salt cavern gas storage is developed, considering the geothermal heat transfer in wellbore and salt carven. The model is used to illustrate the effects of geothermal heat transfer on the system performance through a sensitivity analysis of some key parameters. The results show that geothermal heat transfer will significantly reduce the gas and energy storage capacity, with a maximum reduction of 15.3 % and 11.1 % at a depth of 2000 m, respectively. Furthermore, this reduction would increase with the depth of the salt cavern. The geothermal energy reduces the round-trip efficiency from 68.7 % to 66.26 % and the energy storage density from 5.18 kWh·m−3 to 4.32 kWh·m−3. For common salt cavern gas storage at a depth of about 600 m ∼ 1200 m, the negative impacts of geothermal heat transfer on round-trip efficiency and energy storage density are less than 2.2 % and 0.5 kWh·m−3, respectively. Sensitivity analysis also demonstrates that the primary factors influencing the system’s performance are the thermal conductivity of the surrounding rock, the volume of the salt cavern, and the length of the wellbores. The secondary factors include the heat transfer coefficient on the inner wall of the salt cavern, the inner pipe radius, and the roughness of the inner pipe. Irrelevant factors include the thermal conductivity of the protective fluid and the thermal conductivity of the cement layer. The proposed comprehensive mathematical model of the system and simulation findings aid in forecasting the performance of storage systems and offer theoretical guidance for the design of large-scale compressed air energy storage systems.

Thermodynamic and economic analyses of a modified adiabatic compressed air energy storage system coupling with thermal power generation

With the proposal of "Carbon peaking and carbon neutrality", Adiabatic Compressed Air Energy Storage (A-CAES) has emerged as a significant component within China's energy storage infrastructure. But its thermodynamic efficiency and economical return need yet to be raised. The present paper proposed a modified system coupling with thermal power plant to utilize the excess compression heat. Utilizing advanced transient modeling software, an A-CAES plant is modeled and validated. The operation performance of the coupled system is compared with non-coupled system, which shows that the system efficiency is raised from 54.8 % to 76.7 % and the investment return rate is improved from 9.18 % to 10.43 %.

Solution for Post-Mining Sites: Thermo-Economic Analysis of a Large-Scale Integrated Energy Storage System

The intensive development of renewable energy sources and the decreasing efficiency of conventional energy sources are reducing the flexibility of the electric power system. It becomes necessary to develop energy storage systems that allow reducing the differences between generation and energy demand. This article presents a multivariant analysis of an adiabatic compressed air energy storage system. The system uses a post-mining shaft as a reservoir of compressed air and also as a location for the development of a heat storage tank. Consideration was given to the length of the discharge stage, which directly affects the capital expenditure and operating schedule of the system. The basis for the analyses was the in-house numerical model, which takes into account the variability of air parameters during system operation. The numerical model also includes calculations of Thermal Energy Storage’s transient performance. The energy efficiency of the system operating on a daily cycle varies from 67.9% to 70.3%. Various mechanisms for economic support of energy storage systems were analyzed. The levelized cost of storage varies, depending on the variant, from 75.86 EUR/MWh for the most favorable case to 223.24 EUR/MWh for the least favorable case.

Analysis of temperature rise of low temperature adiabatic oxidation of sulfur-containing “coal-like substances”

ABSTRACT Spontaneous combustion of coal is one of the main natural disasters in the process of coal mining, and spontaneous combustion of sulfur-containing coal is an urgent problem to be solved. In order to understand the influence of different sulfur structures and sulfur content on spontaneous combustion tendency of coal, the self-developed synchronous temperature compensation adiabatic oxidation experiment system was used to study the oxidation self-heating performance of a series of sulfur-containing “coal-like materials.” Through the analysis of the heating rate of coal containing specific sulfur structure, it is considered that the time of adiabatic oxidation temperature of different organic sulfur “coal” to rise to 70°C is dimethyl sulfoxide > phenylene sulfide > dibenzothiophene. By analyzing the oxidation temperature rise characteristics of organic sulfur models with different sulfur contents, it is believed that the higher sulfur content, the faster the low temperature oxidation reaction of “coal-like substance,” the faster the temperature rise rate, and the shorter the time to reach the uncontrollable self-heating temperature, so the shorter the spontaneous combustion period. In general, in the stage of low temperature oxidation, active sulfur containing small molecules (dimethyl sulfoxide) promote the oxidation temperature rise, stable structure, larger molecular weight of dibenzothiophene slow down the “coal-like” oxidation temperature rise.

Effects of Hydrogen, Methane, and Their Blends on Rapid-Filling Process of High-Pressure Composite Tank

Alternative fuels such as hydrogen, compressed natural gas, and liquefied natural gas are considered as feasible energy carriers. Selected positive factors from the EU climate and energy policy on achieving climate neutrality by 2050 highlighted the need for the gradual expansion of the infrastructure for alternative fuel. In this research, continuity equations and the first and second laws of thermodynamics were used to develop a theoretical model to explore the impact of hydrogen and natural gas on both the filling process and the ultimate in-cylinder conditions of a type IV composite cylinder (20 MPa for CNG, 35 MPa and 70 MPa for hydrogen). A composite tank was considered an adiabatic system. Within this study, based on the GERG-2008 equation of state, a thermodynamic model was developed to compare and determine the influence of (i) hydrogen and (ii) natural gas on the selected thermodynamic parameters during the fast-filling process. The obtained results show that the cylinder-filling time, depending on the cylinder capacity, is approximately 36–37% shorter for pure hydrogen compared to pure methane, and the maximum energy stored in the storage tank for pure hydrogen is approximately 28% lower compared to methane, whereas the total entropy generation for pure hydrogen is approximately 52% higher compared to pure methane.

Adiabatic Compressed Air Energy Storage system performance with application-oriented designed axial-flow compressor

Medium and long-duration energy storage systems are expected to play a critical role in the transition towards electrical grids powered by renewable energy sources. ACAES is a promising solution, capable of handling power and energy ratings over hundreds of MW and MWh, respectively. One challenge with ACAES is achieving the required highly efficient operation in the compressor over the range of conditions encountered in the system as the pressure in the air store changes. In this paper, an application-oriented axial-flow compressor is designed, aiming towards efficient operation throughout the operation range, whilst also associating the performance prediction to a practical compressor geometry. A two-step design methodology based on inviscid, axisymmetric flow conditions has been implemented, leading to the flowtrack, blade-row geometries and the compressor performance map. The compressor model is integrated into an ACAES model, including two compression spools, two expansion stages with preheat, a constant volume high pressure storage operating between 5.5 and 7.7 MPa and two separate Thermal Energy Storage units. While the existing ACAES literature either ignores the transient off-design operation or uses generic numerical correlations (which are not associated to a particular geometry), the key novelty of this paper is the application of a detailed design method for turbomachinery to ACAES. The results indicate that the designed compressor requires 33 stages over the two spools, and is able to operate efficiently over the storage pressure range, showing that if the application-oriented design procedure is applied to the compressor, it does not stop ACAES reaching 70% round-trip efficiency, outputting 35MW for approximately 15 h. Importantly, the specific ACAES requirement of conserving heat at higher temperatures has been fulfilled by decreasing the number of intercoolers. Finally, it is recommended that a similar level of scrutiny is applied to the other components (i.e. expanders, heat exchangers and TES units), keeping in mind the unique set of operational requirements of ACAES. This work is an important step towards removing the common misconception that off-the-shelf components can be easily be used in typical ACAES designs.

Research on compressed air energy storage systems using cascade phase-change technology for matching fluctuating wind power generation

The wind speed varies randomly over a wide range, causing the output wind power to fluctuate in large amplitude. An isobaric adiabatic compressed air energy storage system using a cascade of phase-change materials (CPCM-IA-CAES) is proposed to cope with the problem of large fluctuations in wind farm output power. When the input power is lower than the minimum energy storage power of the compressor, the gradient phase-change thermal energy storage is utilized to broaden the operating range of the system. Second, the system design method and operation rules are elaborated. The storage/release characteristic curve is obtained by constructing the system components and the overall variable operating condition model. A matching system scheme is designed according to the characteristics of a wind farm in a port in China. The case study shows that the wind farm configured with the CPCM-IA-CAES system reduces the wind abandonment rate by 5.7%, recovers 4,644.46 kW h of wind power abandonment, and improves the storage power index by 16.67% compared with that of IA-CAES. Meanwhile, the system efficiency is increased from 65.96% to 74.68%, and the energy storage density is increased from 8.69 to 9.89 kW h m−3.

Advanced exergo-economic analysis of an advanced adiabatic compressed air energy storage system with the modified productive structure analysis method and multi-objective optimization study

In this study, conventional and advanced exergy/exergo economic analyses of an advanced adiabatic compressed air energy storage system (AA-CAES) system with a power output of 6 MW were performed. In addition, sensitivity analysis and multi-objective optimization study of the proposed system were also carried out. For the first time in the literature, advanced exergo-economic analysis was applied to the AA-CAES system with the Modified Productive Structure Analysis (MOPSA) method, and a new parameter was introduced as a performance criterion for this method. As a result of the study, the system's exergy efficiencies were found to be 54.51 % and 77 %, respectively, according to the conventional and advanced exergy analyses of the system. According to the conventional exergy analysis, the first three system components that should be given priority are the wind turbine (WT), the regulator (REG), and the heat exchangers-3 (HE-3), respectively. According to the advanced exergy analysis, this order changes as WT, the compressor-1 (C-1), and the compressor-2 (C-2). 40 % of the system's exergy destruction and exergy destruction cost rates are avoidable endogenous. This value shows the improvement potential of the system. As a result of the multi-objective optimization study, the modified exergy efficiency was found to be 94.58 %. The average unit product-exergy destruction cost was 59.51 $/GJ; these values were 22.83 % and 1.6 % improvement, respectively, compared to the base case.

Theoretical analysis of cavern-related exergy losses for compressed air energy storage systems

The paper presents a thermodynamic analysis of the exergetic losses occurring due to pressure and temperature variations within constant-volume compressed air caverns. Direct cavern losses are due to mixing and irreversible heat transfer, and may also include an exit loss as a result of unusable thermal exergy in the discharge air. Additional cavern-related losses may occur in other system components, including compressors (due to off-design operation), throttles and thermal stores. These indirect losses are also discussed and analysed for a simplified but representative adiabatic compressed air energy storage system. The overall aim is to determine trends in the various loss components with operating parameters (chiefly the minimum and maximum cavern pressures) and other thermal parameters. A comparison between isobaric and isochoric storage is also made and reveals the trends of efficiency vs. storage density for these two modes of storage.

Adiabatic compressed air energy storage system combined with solid-oxide electrolysis cells

Green hydrogen from electrolysis using renewable energy is becoming increasingly important and competitive because of the rapid decrease in the price of electricity from solar photovoltaic (PV) and wind power. Electrical energy storage (EES) can reduce the installation capacity of electrolyzers owing to their steady and continuous operation. Adiabatic compressed air energy storage (A-CAES) systems can be effectively combined with large scale solid-oxide electrolysis cells (SOEC) for low-cost production of hydrogen. Although the round-trip efficiency of the power-only A-CAES (70–75%) is lower than that of batteries (90%), the A-CAES system can be used as a combined cooling, heat and power (CCHP) system, providing heat and power to SOEC in order to maximize the energy efficiency of the system. This paper presents a parametric study of an A-CAES system combined with an SOEC system in terms of the energy and exergy analyses. The results show that a medium-temperature trigeneration CCHP A-CAES system in combination with a SOEC system with a compression power of 100 MWh can provide 47.8 MWh of electric power and 63.5 MWh of heat to the SOEC system as well as 9.9 MWh of cold energy from the cold outlet air of the A-CAES.