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To control greenhouse gas emissions and improve the sustainability of renewable energy technologies, thermal energy storage systems are receiving significant attention in recent years. Extensive research has been conducted on shell-and-tube Latent Heat Thermal Energy Storage (LHTES) systems to match energy supply and demand. The selection of the tube and shell diameter in the heat exchanger is a crucial aspect in the design of LHTES systems. This research intends to deliver the most suitable shell-to-tube diameter ratio for the complete operation of horizontal thermal energy storage. Different shell-to-tube diameter ratios were studied using two schemes: (i) varying the shell diameter on a fixed-sized inner tube, and (ii) varying the inner tube diameter within a fixed shell diameter. The outer shell was constructed of acrylic, while the inner tube was made from copper, and paraffin RT50 was used as the phase change material. Numerical simulations were performed using the enthalpy-porosity method and verified with data from the literature. Performance indicators, such as average liquid fraction, temperature, average storage/retrieval rate, Fourier number and storage/retrieval density were utilized to evaluate the system's performance. Results indicated that the thermodynamic characteristics were similar in both schemes. The maximum energy density was found to be around 268 kJ/kg and remained constant until a diameter ratio of 5 and 4 for the charging and discharging processes, respectively, before decreasing. During charging, the Fourier number decreased initially and then stabilized at 0.4 after the diameter ratio of 5, while it stabilized at 1.2 during discharging. The best diameter ratio was found between 4 and 5 for the charging process, and between 3 and 4 for the discharging process. Ultimately, the most suitable diameter ratio was recommended as 4 for the complete cycle. • Effect of shell-to-tube diameter ratio in a horizontal LHTES has been investigated. • Energy storage density remains constant up to a specific diameter ratio. • Fourier number plays a critical role in identifying the best diameter ratio. • Most favourable ratio lies between 4 and 5 for charging and 3 to 4 for discharging. • Overall, the most suitable ratio is recommended as 4 for the complete operation. [ABSTRACT FROM AUTHOR]

Abstract Integration of renewable energy source (RES) generation to displace diesel generation can present clear economic, environmental and social benefit. While low level RES integration is relatively easy to achieve, both the cost and complexity escalate as systems target increasing RES penetration. A key barrier to greater RES penetrations remains the inefficiency of diesel generation to operate at low or partial loading. To achieve low or partial loading, conventional fixed speed diesel technologies must rely on prescribed purge routines, which serve to increase emissions intensity and fuel consumption. Fixed speed constraint remains the primary barrier to increased engine flexibility and improved partial load efficiency. This paper investigates redesign of the diesel generator to achieve variable speed operation. A suitable design basis is developed, with laboratory testing used to validate unit performance, ahead of economic evaluation. Economic modelling is presented to explore the improve engine flexibility, required of hybrid diesel applications. Variable speed application is shown to reduce diesel fuel consumption by up to 40 % in comparison to conventional hybrid diesel applications. [ABSTRACT FROM AUTHOR]

Abstract In the isolated power system, consumers are traditionally supplied with electricity produced by diesel generators. Conventional diesel generators demonstrate robust and efficient operation when connected to electrical grids with slowly varying loads. With the introduction of intermittent and stochastic renewable energy sources, such generators may not be responsive enough to retain the stability and reliability of the system. The problem becomes especially acute in cases when diesel generators are required to operate at a low load. Regulating devices (e.g. energy storage systems and/or dump load) used to improve the system reliability, increase system complexity and incur additional expenses or energy losses. This paper investigates low load diesel technology as a potential solution to high level renewable energy penetration. The focus is made on the engine time delay and the generator inertia constant that should be considered during the design of the isolated hybrid power system. [ABSTRACT FROM AUTHOR]

Abstract Methanol vehicles, as a type of alternative energy vehicle, become an approach to mitigate the dependence on petroleum and to reduce emissions. A number of policies for implementing methanol vehicles have been promulgated by the Chinese government to achieve sustainable development. This paper summarizes existing policies for pilot projects, methanol fuel and fuel stations, technological improvement and manufacturer engagement. Then, the paper systematically reviews the released policies based on their categorisation and timeline. Whilst the released policies for pilot projects were sufficient and effectiveness, there was a lack of incentive policies for other aspects. Based on the policy assessment, it is necessary to enhance the continuity and effectivity of the existing policy mechanism. As a contribution, this paper provides some suggestions including: developing follow-up policies after the accomplishment of pilot projects; providing more incentive policies to encourage technological improvement of methanol vehicles; creating a trans-provincial methanol fuel region and enhancing manufacturer engagement by narrowing the subsidy gaps between methanol vehicles and other AEVs. [ABSTRACT FROM AUTHOR]

Abstract To improve the use of renewable energy sources and increase their penetration in the renewable energy market, different types of energy storage technologies have been introduced among which compressed air energy storage (CAES) systems offer more competitive feature. In this paper, a comprehensive exergy analysis of a one-stage, adiabatic compressed air energy storage (A-CAES) system is carried out for a wide range of parameters. The governing parameters on the system performance include, but not limited to, storage pressure, pre-set vessel pressure as well as isentropic efficiencies of the major components involved in the A-CAES systems most specifically compressor and expander. By performing the exergy analysis and using the concept of exergy destruction, which is a criterion for power loss due to the irreversibility, the magnitude and source of thermodynamic inefficiencies at each part of the system is identified. The obtained results reveal that the isentropic efficiency of the machine has a significant effect on the amount of exergy destructed by the machine. In addition, the results show that generally more exergy is lost in the expander than other components of the A-CAES system during the system operation. Consequently, to improve the system performance, utilising a high-efficient expander should be a priority. It is also shown that increase in the storage pressure improves the exergy efficiency of the compressor and expander. Using the obtained results, it would be possible to find the optimum working condition for the system leading to improvement of the system performance. [ABSTRACT FROM AUTHOR]

Abstract Following time-constraining obligations under 2015 Paris Agreement, nations are racing to integrate more renewable energy generation into their power systems than ever before. While solutions for mitigation of renewable energy negative effects to power system stability exist, they are still complex and expensive. One of the most promising technologies, battery energy storage, is widely advocated, but is still unable to solve basic challenge of renewable energy integration – low inertia and provision of sufficient fault currents. This paper presents a practical enabling technology in a form of synergy between a battery energy system and a synchronous machine, which can support fully renewable power system while providing nominal power system inertia. For simplicity, the case for this technology is presented on an example of an Isolated Power System capable of 100% instantaneous renewable operation for prolonged periods of time. High-speed measurements during both steady-state operation and performance under fault conditions were recorded and presented in the paper. [ABSTRACT FROM AUTHOR]

Abstract Moving away from a centralized diesel generation plant, future isolated power systems will increasingly depend on renewable generation which can be distributed across larger areas, due to lower energy density of renewable resources. In future distributed generation systems, a key enabling technology for operating high renewable energy penetration system will be a high-speed communications infrastructure. This new infrastructure can then be used for real-time power system monitoring and control of customers loads, as well as for control of the distributed generation. Our paper presents the concept of a high-speed wireless network capable of real-time monitoring and control of both loads and distributed generation across an isolated power system. The paper also presented real-world measurements taken during a multi-year operation of an isolated power system, and specifically, presented how utilizing communications networks can prove beneficial to increasing renewable penetration in the system whilst preserving power system stability. [ABSTRACT FROM AUTHOR]

This paper presents experimental results of cluster analysis using self organising neural networks for identifying failing banks. The paper first describes major reasons and likelihoods of bank failures. Then it demonstrates an application of a self-organising neural network and presents results of the study. Findings of the paper demonstrate that a self-organising neural network is a powerful tool for identifying potentially failing banks. Finally, the paper discusses some of the limitations of cluster analysis related to understanding of the exact meaning of each cluster. [ABSTRACT FROM AUTHOR]

• A PHCA system can be incorporated with renewable sources such as wind and solar. • A thermodynamic and exergy model was developed to study a PHCA system performance. • Key parameters affecting the system performance were investigated and evaluated. • Exergy destruction for each system component was analysed and discussed. • Pump was identified as the most important component to improve the system efficiency. The Pumped-Hydro and Compressed-Air (PHCA) is a new energy storage system which can be coordinated with renewable energy sources such as wind and solar. In this paper, a comprehensive thermodynamic and exergy model is developed to study the thermal characteristics of a combined Pumped-Hydro and Compressed-Air (PHCA) energy storage system. The effect of key parameters, including storage pressure, pre-set pressure, air-compression mode and pump/hydroturbine efficiency on system performance is investigated. The results showed that an optimum pre-set pressure existed to maximize energy storage level for a specific storage pressure. The storage pressure also showed a large effect on the energy storage level and work output. As the storage pressure increased from 4 to 16 MPa, the energy storage level and work output increased remarkably. Furthermore, the performance of a PHCA system was largely influenced by the air compression/expansion mode in the energy storage vessel. The PHCA system stored 10% more energy through an isothermal compression process than that through an isentropic air compression process. It generated 14% more work output through an isothermal expansion process than that through an isentropic air expansion process. The exergy analyses showed that exergy destruction in pump was about 15% higher than that in hydroturbine. [ABSTRACT FROM AUTHOR]