Phase-change thermal storage technology has been widely studied and applied because of its high heat storage density and constant temperature. Particularly in the case that energy supply is not continuous, its application is very extensive. As an effective method to resolve the time and space conflicts of energy supply, phase-change thermal storage system can significantly improve energy utilization efficiency. In this paper, state-of-the-art of phase change thermal storage at middle and low temperature includes the three aspects: Phase-change material selection, numerical simulation of the phase-change process, phase-change thermal storage device. Firstly, introducing species and cycling stability, thermal conductivity enhancement of the phase change material. Secondly, summarizing numerical simulation methods and theories. Thirdly, describing different devices of phase-change thermal storage. Finally, pointing out the research objectives and directions of phase-change thermal storage at middle-low temperature.

Energy storage power station is an effective method to meet the urgent demand for solving the problem of intermittency and instability of renewable energy and improving the efficiency, security and economical efficiency of conventional electric power system and the regional energy system. A new kind of thermal storage power station technology----Independent thermal storage power station with molten salt is proposed in this paper. This paper outlines the principle, conceptual design and techno-economic appraisal of the independent thermal storage power station with molten salt. The results show that initial investment of the station is very low, only 6152.88yuan/kW. Its payback period is short, within three years. Independent storage plant with molten salt can set up in cities and towns with less area occupation and the plants can realize the cogeneration of heat and power. Total efficiency can be raised from 30% for power only to more than 80% for cogeneration.

A three dimensional model for a shell-and-tube latent heat storage (LHS) unit was established to investigate the effect of liquid PCM natural convection on the performance. The enhancement effects of the outside enhanced tube and the bilateral enhanced tube were comparatively studied with the smooth tube. The results show that the natural convection can cause nonuniform distribution of solid-liquid interface and the nonuniformity can be weakened by using the designed enhanced tubes. At the same time, the presented enhanced tube can reduce the PCM melting time and total charging time. Compared with the PCM melting time of the smooth tube, the PCM melting time of the outside enhanced tube is reduced by 18.0% and the PCM melting time of the bilateral enhanced tube is reduced by 52.5%. In a conclusion, the presented finned enhanced tube can not only weaken the nonuniform distribution of solid-liquid interface caused by liquid PCM natural convection, but also enhance the LHS performance.

Microencapsulated phase change materials (MicroPCMs) are widely used for larent heat storage. The core and wall materials of MicroPCMs and their properties are reviewed in this paper. Several preparation methods including in-situ polymerization, interfacial polymerization, complex coacervation, suspension-like polymerization and spray drying are discussed and the applications of MicroPCMs in building, heat conduction, fiber fabric, military camouflage and electronic device cooling fields are summarized.

The research of expanded graphite matrix composite phase change material is the highlight in energy storage science field, for its properties of high thermal conductivity, high energy storage density and no liquid leakage during the phase change process. This paper discusses the properties and classification of phase change materials used in thermal storage system, and the preparation methods of expanded graphite and its composite phase change material are briefly analyzed, finally reviewed the domestic and overseas research progress of expanded graphite matrix composite phase change materials with the working media of waxes, fatty acids, eutectic mixture, polyethylene glycol and acetamide.

This bimonthly review paper highlights 100 recent published papers on lithium batteries. We searched the Web of Science and found 1203 papers online from Feb. 1, 2014 to March 31, 2014. 100 of them were selected to be highlighted. Layered oxide and high voltage spinel cathode materials are still under extensive investigations. Large efforts were devoted to Si based anode materials and composite carboneceous anode, solid state electrolytes, additives for electrolyte. There are a few papers related to Li/S battery, Li-air battery and more papers related to theoretical simulations, cell analyses and modeling.

Chemical heat pump (CHP) is a high-efficient and environment-friendly energy technology. CHP has promising potential on applications in waste-heat harvest, energy storage and renewable energy. This paper reviews the general theory and application progress in terms of the reaction selection, working pairs and industrial development.

Energy storage is an effective technology for improving the energy utilization efficiency, and it can be used to adjust the instability and time-discrepancy between energy supply and energy demand. The conventional sensible and latent heat storage technologies have energy densities ranging from 100 kJ/kg to 200 kJ/kg. The low storage capacity usually hinders their application in large-scale situation. A potential solid-gas thermochemical sorption method is proposed in the paper for achieving the high-capacity thermal energy storage with little heat losses. Thermal energy is stored in form of chemical bonds resulting from thermochemical sorption process of solid-gas working pair. The operating principle and working performance is described and analyzed using four typical sorption working pairs with different working temperatures, and the candidates of possible working pairs are presented for thermal energy storage with a temperature range between 50~280℃. Thermodynamic analysis showed that the advanced thermochemical sorption energy storage method has a distinct advantage of high energy density when compared with conventional sensible and latent heat storage methods. An energy density higher than 2000 kJ/kg of salt was obtained by employing the proposed thermochemical sorption energy storage technology, and it was about 10~20 times the energy density obtained with sensible and latent heat storage. The presented thermochemical sorption energy storage is a potential high-capacity heat storage method, and thus it can promote the application of thermal energy storage in large-scale industrial processes and the utilization of renewable energy.

This paper concerns a solar thermal water heating system that combines two concrete modules connected in series for thermal energy storage. The heat transfer performance of the concrete based thermal storage unit was investigated experimentally. The results showed that the temperature of the concrete thermal storage modules increased from 31.5 ℃ to 65 ℃ within a charging period of 6 h using solar thermal energy, and the water temperature difference from the storage was about 10 ℃. During the discharging process, the outlet water temperature was about 45 ℃, which could potentially be used for building heating for 8 h.

Paraffin-based composite phase change materials (PCMs) were prepared by using graphene nanoplatelets (GNPs) and boron nitride nanosheets (BNNs). Effective thermal conductivity of the PCM composites in solid state was measured at 20 ℃ using a transient plane source technique. It was shown that the thermal conductivity increased linearly with increasing particle loading for both nanofillers. The thermal conductivity enhancement of the GNPs/paraffin composites was found to be much higher than the BNNs/paraffin composites. The effective medium theory was used to analyse the thermal conductivity of the composites. It was found that, despite of similar shape, size and thermal conductivity of the two nanofillers, the calculated interfacial thermal resistance of BNNs was two orders of magnitude higher than that of GNPs, which explained, at least partially, the observed better performance of the PCM composite containing GNPs.

This paper reports a study on the supercooling behaviour and non-isothermal crystallization processes of dilute aqueous suspensions of carbon nanotubes. A differential scanning calorimeter (DSC) was used in the study. The dependence of the extent of the suspension supercooling was measured as a function of nanotube concentration and cooling rate. It was found that the extent of supercooling of water decreased due to the addition of carbon nanotubes and the extent of decrease increased with increasing carbnon nanotube concentration. The decrease in the supercooling was nearly 7 ℃ at a concentration of 1%. An increase in the cooling rate led to a slight increase in the extent of supercooling. Although the use of carbon nanotubes was able to reduce the extent of supercooling, it did not show any influence on the non-isothermal crystallization processes.

The electrolyte is a very important component in lithium ion batteries. Practically, it is quite difficult to find an optimized electrolyte composition to satisfy different requirements for various applications. In this article, the nonaqueous electrolytes, including history, basic properties, solvents, lithium salts, additives, ionic liquids, gel polymer electrolytes and high voltage electrolytes are summarized briefly. Several problems needs to be solved in the future:Improving the safety of the electrolyte, extending voltage range and temperature ranges, prolonging the cycle life and service life, lowering the cost.

Bipolar plates served as one of the key components for flow batteries plays an important role in connecting the positive and negative electrodes and physically separated the electrolyte in the neighboring chambers. The types of bipolar plates reported before included metal plates, graphite plates and composite plates. Composite plates meet the demands of the flow batteries and meanwhile they overcome some shortcomings of metal plates and graphite plates. Carbon fiber has various advantages including good conductivity, mechanical strength and chemical stability. And herein the method of adding carbon fiber into bipolar plates is attracting more and more researchers to improve the performance of the bipolar plates. This paper reviews the recent major research results of employing carbon fiber to reinforce the performance of composite bipolar plates. Moreover, various methods are compared and proposed to the development tendency of reinforcing the properties of composite bipolar plates with carbon fiber.