Overview of current development in electrical energy storage technologies and the application potential in power system operation

The increase in energy demand and reduction in resources for conventional energy production along with various environmental impacts, promote the use of renewable energy for electricity generation and other energy-need applications around the world. Wind power has emerged as the biggest renewable energy source in the world, whose potential, when employed properly, serves to provide the best power output. In order to achieve self-sustenance in energy supply and to match the critical needs of impoverished and developing regions, wind power has proven to be the best solution. However, wind power is intermittent and unstable in nature and hence creates lot of grid integration and power fluctuation issues, which ultimately disturb the stability of the grid. In such cases, energy storage technologies are highly essential and researchers turned their attention to find efficient ways of storing energy to achieve maximum utilization. The use of batteries to store wind energy is very expensive and not practical for wind applications. Compressed Air Energy Storage (CAES) is found to be a viable solution to store energy generated from wind and other renewable energy systems. A detailed review on various aspects of a CAES system has been made and presented in this paper which includes the thermodynamic analysis, modeling and simulation analysis, experimental investigation, various control strategies, some case studies and economic evaluation with the role of energy storage towards smart grid and poly-generation.

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A review on compressed air energy storage – A pathway for smart grid and polygeneration

A review of scroll expanders for organic Rankine cycle systems

With the increase of power generation from renewable energy sources and due to their intermittent nature, the power grid is facing the great challenge in maintaining the power network stability and reliability. To address the challenge, one of the options is to detach the power generation from consumption via energy storage. The intention of this paper is to give an overview of the current technology developments in compressed air energy storage (CAES) and the future direction of the technology development in this area. Compared with other energy storage technologies, CAES is proven to be a clean and sustainable type of energy storage with the unique features of high capacity and long-duration of the storage. Its scale and cost are similar to pumped hydroelectric storage (PHS), thus CAES has attracted much attention in recent years while further development for PHS is restricted by the availability of suitable geological locations. The paper presents the state-of-the-art of current CAES technology development, analyses the major technological barriers/weaknesses and proposes suggestions for future technology development. This paper should provide a useful reference for CAES technology research and development strategy.

Overview of Compressed Air Energy Storage and Technology Development

Modelling study, efficiency analysis and optimisation of large-scale Adiabatic Compressed Air Energy Storage systems with low-temperature thermal storage

A scroll air motor, also known as a scroll expander, is a relatively new concept to pneumatic actuators. Its unique structure leads to its feature of high ability in energy conversion. In recent years, scroll air motors have been adopted by combined heat and power boilers, uninterrupted power supplies, and some other energy storage systems as a new mechatronic device for energy conversion. The paper aims to present the work in developing a complete mathematical model of the scroll air motor for analysis of scroll energy efficiency and the factors affecting energy efficiency. The work will be reported in two parts of the paper. The paper describes the derivation of spiral equations, chamber volume calculations, and the driving torque of the scroll air motor. The dynamic process modeling and energy efficiency analysis will be presented in Part II of the paper.

Mathematical Modeling Study of Scroll Air Motors and Energy Efficiency Analysis—Part II

Although pneumatic actuators have been widely used in industry and other application areas, its weakness in low-energy efficiency is well known. Aiming for energy efficiency improvement, this paper presents a new hybrid pneumatic system that will recover energy from the exhaust compressed air through a scroll expander. The scroll expander drives a generator to convert the exhaust compressed air energy to electrical energy; thus, the proposed system is entitled “pneumatic-electrical” system. A closed-loop coordinate control strategy is engaged and proven to be essential in maintaining proper actuator operation status, while the scroll expander is connected in. The overall system mathematical model is derived and simulation results are presented in this paper. A test rig is set up to verify the feasibility of the proposed system structure. Both simulation and test results indicate that the proposed scheme is realistic and work well.

Study of a New Strategy for Pneumatic Actuator System Energy Efficiency Improvement via the Scroll Expander Technology

A voltage regulation device adapted for connection to a varying electrical supply and to regulate the voltage supplied to certain selected circuits whose loads benefit from voltage regulation. The device comprises a PWM or phase angle switched autotransformer which is sufficiently compact and lightweight to be incorporated into a standard electrical consumer unit which has separated circuits, ie, those whose loads benefit from voltage regulation and those whose loads do not, such that the former may be controlled by the device to operate at a constant and reduced voltage thus ensuring a reduction in energy consumption and the life enhancement of the appliances connected to the device. The operating temperature of the autotransformer is controlled by temporarily increasing the output voltage of the autotransformer in the event of overheating.

A voltage regulation device

The paper presents a simplified mathematical model for a scroll-type air motor. Through air power/energy analysis, it has shown that a scroll-type air motor with a properly specified structure and suitable pressure of compressed air supply is able to achieve high energy efficiency and satisfies air power requirement. The features of a scroll-type air motor in geometry, mechanical structure, and pneumatic power transmission are studied in the paper. Differential geometry is used as the mathematical tool to parameterise the scroll. In this study, Matlab Symbolic Math Toolbox is found very efficient in finding analytic expressions of scroll chamber volumes and generalised torques. State shifting is employed to solve the dynamic system equations numerically. Energy efficiency of a scroll-type air motor is analysed based on the mathematical model.

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Energy Efficiency Analysis of a Scroll-type Air Motor Based on a Simplified Mathematical Model.

A system for reducing the voltage of an AC electrical supply to a load for the purpose of energy efficiency, comprising a transformer and power converter in circuit between an AC electrical supply and a load, and a bypass switch S to cause the transformer to be taken out of circuit and to connect the electrical supply to the load in the event of a sustained overload of the transformer. The system includes means (14) to measure the temperature of the transformer, means (17) to measure the electrical current in the circuit and control means (15) receiving signals from the sensors (14, 17) and to operate bypass switch S to bypass the transformer and allow it to cool. A fuse F 2 and thermal cut out device (16) are in circuit with the secondary winding of the transformer as failsafe means to interrupt the supply to the transformer in the event that the bypass switch fails to operate.

Mangan Stephen

Papers

Mathematical Modeling Study of Scroll Air Motors and Energy Efficiency Analysis—Part II

Study of a New Strategy for Pneumatic Actuator System Energy Efficiency Improvement via the Scroll Expander Technology

A voltage regulation device

Energy Efficiency Analysis of a Scroll-type Air Motor Based on a Simplified Mathematical Model.

Overload protection of a voltage reduction device