High performance materials play a key role in the development of thermal energy storage technologies. This paper first provides a state-of-the-art review on the development of thermal energy storage materials with a specific focus on applications at medium and high temperatures. The review covers classification, characteristics, applications and technological barriers for sensible heat storage materials, thermochemical storage materials and latent heat storage materials. Recent progress in the composite structured thermal energy storage materials is then presented. Finally, an outlook of future development of the medium and high temperatures thermal storage materials is given and nano/micro-structured composite materials are recommended as a direction for future research.

Energy storage will play a pivotal role in the next generation power grid and is the key enabler for renewable energy. Its potential applications widely spread within the domain of electricity generation, transmission, distribution and power end user. We briefly summarized and analyzed the energy storage market economics in this paper, focusing on the key bottleneck of the energy storage adoption, i.e., cost. The cost target of general energy storage product is identified, and viable cost reduction pathways are thoroughly analyzed, with the historical development of PV product as the reference. We concluded that the energy storage market is expecting high growth with high economical and societal value with large challenges, especially in China. The cost reduction remains the critical cornerstone in this challenge.

Phase change materials have a great potential in building insulation applications. This paper first provides a brief summary of the classification and synthesis routes for the materials. Recent progress in the research and development of the materials, and applications and associated technological issues are then discussed. Finally, techno-economic aspects and future development of the materials are presented.

Three dimensional unsteady-state modeling has been performed on the heat transfer behavior of a heat exchange system made of both a straight and a twisted pipe containing a phase change material(PCM). Natural convection was considered in the modeling. Effects of various factors including fluid velocity, inlet temperature and the configuration of the pipe inlet were examined. The results showed that, given the amount of PCM, the melting time of the twisted pipe heat exchange system was over 15% shorter than the straight pipe configuration. Analyses suggested the secondary flow induced by the twisted pipe as well as the increased heat exchange surface area be the main reasons for the reduction in the melting time. The modeling results of the straight pipe show a deviation from the measurement, but the trend agrees fairly well. This indicates that the modeling results could serve as a guidance for the design and optimization of the phase change heat exchange systems.

This study is concerned about encapsulation of phase change materials (PCM) with a ceramic honeycomb structure to give composite PCM. K₂SO₄ and NaCl were used as the PCM, whereas the honeycomb structure was made of cordierite synthesized in-situ with andalusite as the main raw material. A special agent was developed to seal the opening of the honeycomb pores filled with the PCM. A number of techniques were used to characterize the properties of the prepared composite PCM, including SEM, EPMA, TG-DTA and so on. It was shown that andalusite based ceramic honeycomb structures and the sealing agent can effectively encapsulate the PCMs. The prepared thermal storage density of the composite material containing 20% K₂SO₄ was around 987.70 kJ/kg (0~1080 ℃), whereas that with 16% NaCl was 796.40 kJ/kg (0~810 ℃).

Paraffin wax (PW) has been widely used as a phase change material for thermal energy storage due to relatively high thermal energy storage density and other desirable properties. However, it has a low thermal conductivity (TC), leading to a long charging and discharging time. To address the issue, carbon nanotubes (CNTs) were mixed with PW to form PW-CNTs composites. As CNTs are highly thermally conductive, the use of such a material is expected to give a good level of thermal conductivity enhancement. To further enhance the heat transfer process, metal meshes were placed in the interior of the PW-CNTs composites. Experimental results show that the addition of 10% CNTs by mass leads to a thermal conductivity enhancement of 31.4% and 40.2% respectively in the solid and liquid states. The results also show that the use of metal meshes shortens the charging and discharging durations by at least 40.3% and 30.2%, respectively. Heating and cooling cycling tests have also been carried on the PW-CNTs composites and the results show a large decrease in the thermal conductivity after a few cycles due to severe aggregation of CNTs in PW-CNTs composites.

Faraday's Law describes the quantitative relationship between electronic transfer and matter transformation during electrochemical reaction, which constitutes one of the fundamental theories for the modern electrochemical engineering. Faraday's Law denotes an alternative formation of the charge and mass conservation in electrochemical reaction. Nowadays, it has been used in many advanced and mature industrial fields, including electro-deposition industry, battery manufacture, Coulomb analysis processes and so on. For better understanding Faraday's Law, this paper reviews the background of basic idea of Faraday's experiment and the following proof, since we believe that a historical review will discover some important factors in the past, which can highlight our future research in the electrochemical field.