Small-scale Compressed Air Energy Storage Research Articles

Small-Scale Compressed Air Energy Storage Application for Renewable Energy Integration in a Listed Building

In the European Union (EU), where architectural heritage is significant, enhancing the energy performance of historical buildings is of great interest. Constraints such as the lack of space, especially within the historical centers and architectural peculiarities, make the application of technologies for renewable energy production and storage a challenging issue. This study presents a prototype system consisting of using the renewable energy from a photovoltaic (PV) array to compress air for a later expansion to produce electricity when needed. The PV-integrated small-scale compressed air energy storage system is designed to address the architectural constraints. It is located in the unoccupied basement of the building. An energy analysis was carried out for assessing the performance of the proposed system. The novelty of this study is to introduce experimental data of a CAES (compressed air energy storage) prototype that is suitable for dwelling applications as well as integration accounting for architectural constraints. The simulation, which was carried out for an average summer day, shows that the compression phase absorbs 32% of the PV energy excess in a vessel of 1.7 m3, and the expansion phase covers 21.9% of the dwelling energy demand. The electrical efficiency of a daily cycle is equal to 11.6%. If air is compressed at 225 bar instead of 30 bar, 96.0% of PV energy excess is stored in a volume of 0.25 m3, with a production of 1.273 kWh, which is 26.0% of the demand.

Dynamic modeling and design of a hybrid compressed air energy storage and wind turbine system for wind power fluctuation reduction

A hybrid compressed air energy storage (CAES) and wind turbine system has potential to reduce power output fluctuation compared with a stand-alone wind turbine. Dynamic behaviour of such a hybrid system is critical to its operation and control. In this paper, we propose a dynamic modeling approach to a hybrid CAES-wind turbine system. Differential algebraic equation based dynamic sub-models are developed for key components, including compressors, internal heat exchangers, a storage chamber and turbines. A case study is presented where a 2 MW wind turbine is integrated with a small-scale CAES system. Dynamic simulation results show that the power output fluctuation of such a hybrid system can be reduced by 38%, and its stable operation period can be extended by three hours.

Performance analysis of an innovative kind of two-stage piston type expansion air engine

In small-scale compressed air energy storage system, expansion air engine is the key component. To improve the expansion air energy performance, an innovative kind of two-stage piston type expansion air engine is put forward. In this article, working principles of the new kind of expansion air engine are described. A mathematical model of the working processes is set up by analysis of the air engine. The characteristics of the expansion air engine are obtained by using the simulation technology. Results show that, first of all, with the same supply pressure, the efficiency of the new kind of expansion air engine is higher than that of the single stage expansion air engine by approximately 15%, which is about 1.31–1.56 times of that of the single stage air engine. Simultaneously, the output power of the new kind of air engine is higher than that of the single stage expansion air engine. Second, the efficiency and output power are mainly impacted by the closing angle of valve 1. Third, the bigger the cylind...

Multi-objective optimization of a gas turbine-based CCHP combined with solar and compressed air energy storage system

The small-scale compressed air energy storage system (CAES) combined with renewable energy sources (RES) is becoming increasing popular in distributed energy system (DES), which allows RES uninterrupted and improves the supply capacity of power system. In order to balance the electricity load and improve the energy efficiency of CCHP system in combined cooling, heating and power (CCHP) system, the paper described a CCHP system combined with solar and compressed air energy storage (CCHP-S-CAES). Solar energy was coupled with the CAES in this paper to heat the high-pressure air from air storage cavern. The proposed system consists of a conventional CCHP, a CAES and a solar energy collector/storage system, which stores the surplus electric power of gas turbine during off-peak time and releases it during on-peak time. Sensitivity analysis on the CCHP-S-CAES system was conducted to investigate the effects of the key parameters on its performances. It is clear that the performances of the CCHP-S-CAES system are mainly determined by the pressure ratio of compressor, the inlet pressure and temperature of turbine and the effectiveness of heat exchangers. In addition, a multi-objective optimization based on the Non-dominated sorting Genetic Algorithm-II (NSGA-II) is performed for obtaining the optimum performance of the CCHP-S-CAES system from the view of investment cost and exergy efficiency. The results show that the optimal exergy efficiency of the proposed system is about 53.10% and 45.36% in maximum heating condition and maximum cooling condition respectively.

A New Hydro-Compressed Air Storage System Using Repetitive-Controlled Technique

A new method for adiabatic compressed air energy storage system is presented, this clean energy solution incorporates compressed ambient air with hydraulic oil in to improve the overall system's efficiency. The approach is based on a new technique of small-scale Compressed Air Energy Storage (CAES) systems; it is implemented using a new design of a Repetitive Controlled Compressed Air Hydro Energy Storage (RC-CAHES) system. The energy is charged using hydraulic pump, which is more efficient than pneumatic compressor in energy conversion. This proposed technique is adequate for residential applications as it is designed for small energy storage systems, with energy of 12kWh and maximum discharging power of 4kW. In addition, the system is simulated using MATLAB/SIMULINK with a 36 cubic meters storage tank and 3000-6000 kPa operating storage pressure. Furthermore, the performance of RC-CAHES system is studied from energy conversion perspective during charging phase. The feasibility of such energy storage system is demonstrated, and it has been verified that all system parameters such as pressure, temperature, work, and enthalpy have similar final results using both analytic and simulation analyses. The main contribution of this paper is that a new storage technique is introduced, and the performance of this technique has been studied and mathematically analyzed from the perspective of energy conversion efficiency, in addition, the instantaneous and continuous performance of power conversion and thermodynamic parameters are studied. By comparing the performance of new CAHES technique with a typical CAES technique that has a similar input power and operational parameters, the results showed that CAHES technique has better performance than typical CAES technique.

Modelling of a new hydro-compressed air-storage system

ABSTRACTThe interest in energy storage systems is increasing, since it provides an excellent solution to store the low-cost excess energy from the energy sources, which are available at peak demand hours. This paper presents a new compressed-air storage system that combines ambient air and hydraulic oil, in order to store energy in compressed-air form and benefit from the advantages of both pneumatic and hydraulic systems. The process consists of charging and discharging cycles, however, this paper investigates the discharging cycle, where a new technique of Small-Scale Compressed Air Energy Storage (SS-CAES) system is realised. The new idea in RC-CAHES is to obtain higher efficiency in energy conversion machines during charging and discharging processes with numerous advantages over conventional types of energy storage systems. This study demonstrates the effectiveness of this technique by proving that it has higher efficiency than a similar Compressed Air Energy Storage (CAES) systems.

Thermo-economic optimization of a combined cooling, heating and power system based on small-scale compressed air energy storage

Energy storage systems are important for dealing with the fluctuation of renewable energies in course of their increasing penetration into the energy market. Small-scale compressed air energy storage (CAES) with artificial air vessels can improve the supply capacity of power system and the utilization of renewable energy by storing excess power during off-peak time and releasing it for on-peak power supply and becomes more promising for distributed energy systems. For diabatic CAES, heat usually cannot be efficiently utilized and the low inlet temperature of turbine in an adiabatic-CAES (A-CAES) usually leads to low discharge efficiency. To address these problems, in this paper, we propose a novel combined cooling, heating and power system (CCHP) based on small-scale CAES. The sensitivity analysis performed shows the effectiveness of heat exchanger, and the air temperature and pressure at the turbine inlet have great influence on the system’s thermodynamic performance. Then, the trade-off between the thermodynamic and economic performances is investigated by an evolutionary multi-objective algorithm. The total investment cost per output power of the Pareto solutions does not increase significantly when increasing exergy efficiency below 51%, indicating the solutions with an exergy efficiency of around 51% are promising for practical designs.

Maximum Power Point Tracking of a Small-Scale Compressed Air Energy Storage System

This paper is concerned with the maximum power tracking of a pneumatically driven electric generator in a standalone small-scale compressed air energy storage system. In this system, an air motor is used to drive a permanent-magnet direct-current generator, whose output is controlled by a buck converter supplying power to a resistive load. The output power of the converter is controlled such that the air motor operates at a speed corresponding to the maximum power. A maximum power point (MPP) tracking controller employs a hybrid perturb and observe method. The rate of change of the converter's output power with respect to its duty cycle and the change of the power and the duty cycle are used to correct the search direction under transient input power fluctuations. Small speed step changes are used in the vicinity of the MPP to improve the accuracy of the search algorithm. However, relatively coarse speed step changes are used when the operating point is far from the MPP to improve the dynamic response of the controller and to increase its speed of convergence. The analysis and design of the controller are based on a small injected-absorbed current signal model of the power converter. The controller is experimentally implemented using a real-time digital signal processor system. Test results are presented to validate the proposed design and to demonstrate its capabilities.

A small-scale CAES (compressed air energy storage) system for stand-alone renewable energy power plant for a radio base station: A sizing-design methodology

In this paper, a novel CAES system (compressed air energy storage) is proposed as a suitable technology for the energy storage in a small scale stand-alone renewable energy power plant (photovoltaic power plant) that is designed to satisfy the energy demand of a radio base station for mobile telecommunications.The innovation introduced in this study concerns two aspects: the first one is the using of a small-scale CAES system integrated with a TES (thermal energy storage) unit with inter-cooling compression and inter-heating expansion; the second one is the cooling energy production, that is obtained by the cold air (3 °C) at the turbine outlet of the CAES system. For this reason, the storage system is defined a PSS-CAES (Polygeneration Small-Scale Compressed Air Energy Storage) system.In this paper, a sizing-design methodology of the energy power plant has been illustrated and the overall performance has been calculated.Results have highlighted that the storage system has an efficiency equal to 57%, that is an interesting value considering its small size. Moreover, the contribution of the PSS-CAES unit on the cooling energy requirements results equal to 17% with reference to the cooling energy required in the hours in which it works.

Design and Simulation Analysis of a Small-Scale Compressed Air Energy Storage System Directly Driven by Vertical Axis Wind Turbine for Isolated Areas

AbstractIncreasing interest is being paid to the exploitation of wind power to supply stable electricity for the microgrid. The microgrid system coupled with wind turbines is available to generate power for local residents, especially in isolated areas. Being suitable for a microgrid, a 30-kW compressed air energy storage (CAES) system directly driven by a vertical axis wind turbine (VAWT) is presented in this paper. A high-pressure storage tank was used to store the compressed air in order to guarantee continuous operation. In addition, a control strategy was designed for the system to make full use of wind energy and enhance system stability. Moreover, a mathematical model was established to simulate the system with hourly wind speed data, which were randomly selected from Zibo in the Shandong province of China. Variations in gas turbine temperature, operation pressure, and the mass flow rate of compressed air with wind speed over two weeks in winter and two weeks in summer are shown in the paper. The r...

Innovative isothermal oil-free co-rotating scroll compressor–expander for energy storage with first expander tests

The development of an efficient isothermal turbine and compressor is essential for the realization of a small-scale compressed air energy storage (CAES).This article presents the theoretical development of an oil-free co-rotating scroll air compressor and turbine working with water injection to make the operations of expansion and compression as isothermal as possible. First experimental results in expander mode are shown.The theoretical performance is predicted with the help of a mathematical model using the equations of energy and mass conservation and the equation of state. This model takes into account the effects of water injection and volumetric losses.The experimental prototype is an oil-free scroll air compressor with the distinctive feature of having two mobile involutes working in synchronized co-rotation one relative to another. The prime-mover is an electric motor driving the two scrolls with two synchronizing belts. Water injection in the housing intends to provide a quasi-isothermal compression. The same device is used as an isothermal expander by supplying high-pressure air with water when it rotates backwards in expander mode, the electric motor acting then as a generator.Expected improvements to a standard scroll compressor and expander are a better volumetric efficiency and a greater power density due to a higher rotational speed of the scrolls, thanks to their symmetrical masses. The isothermal processes increase also the overall performance.

Overview of Current Development in Compressed Air Energy Storage Technology

With the rapid growth in electricity demand, it has been recognized that Electrical Energy Storage (EES) can bring numerous benefits to power system operation and energy management. Alongside Pumped Hydroelectric Storage (PHS), Compressed Air Energy Storage (CAES) is one of the commercialized EES technologies in large-scale available. Furthermore, the new advances in adiabatic CAES integrated with renewable energy power generation can provide a promising approach to achieving low-carbon targets. The small-scale CAES facilities are also attracting attention for more flexible power system applications. This paper will present an overview of different types of multi-scale CAES, including their working principles, current development, typical technical and economic characteristics, existing facilities, application potentials, challenges and issues associated with the future development of CAES.

Guidelines for the pressure and efficient sizing of pressure vessels for compressed air energy storage

The paper reports guidelines for the efficient design and sizing of Small-Scale Compressed Air Energy Storage (SS-CAES) pressure vessels, including guidelines for pressures that should be used in the SS-CAES system to minimize the cost of the pressure vessel. Under a specified energy storage capacity and specified maximum and minimum operating pressures in CAES, the volume of the vessel(s) can be evaluated. The present study provides guidelines for choosing appropriate shape and size for the vessels that minimize material and manufacturing cost for cylindrical vessels. The two main contributions of the paper are that it provides a methodology to determine: (a) an optimum pressure; (b) the shape, size, and number of vessel to be used in a particular application. Results suggest that pressure vessels with a length to diameter ratio of roughly three are the most economical, and that a system should be designed for a pressure of roughly three times the minimum pressure of the expansion device.