Xu Yujie

Advances and prospects in thermal energy storage: A critical review

Thermal energy storage is an indispensible technology for adjusting the instability and time discrepancy between supply and demand of energy. It is mainly utilized for intermittent occasion, such as solar energy, variable energy load, and excessive energy that would be wasted rather than effectively utilized if it cannot be stored. Due to their potential for efficiently improving the comprehensive utilization rate of energy, thermal energy storage systems are of growing importance within the energy awareness: solar thermal utilization, peak shaving, industrial energy saving and waste heat recovery, building energy conservation, energy internet construction and so on. Developing efficient and inexpensive thermal energy storage devices is as important as developing new sources of energy, thus, in the past several years the thermal energy storage techniques have attracted a great deal of attention from both fundamental research and technological applications. Usually, there are three different mechanisms for thermal energy storage techniques: the sensible heat storage, the latent heat storage and the themochemical heat storage. The scope of this review is to give an overview and further analysis on the research which has been done on these three kinds of thermal energy storage techniques, and this review will be beneficial for the researchers and engineers to develop more efficient and optimized thermal energy storage systems. On the one hand, the research trends of three kinds of thermal energy storage techniques from 2000 to 2015 are carefully analyzed in the present review by using the statistics functions within the Web of Science Platform managed by Thomson Reuters. The statistics results show that according to the trends on paper numbers of each thermal energy storage techniques within the whole statistics period, the latent heat storage currently can be concluded as the most popular thermal energy storage technique in terms of fundamental research, the sensible heat storage is classified as least concern because main sensible heat storage systems so far have been almost matured, and the thermochemical heat storage is attracting more and more attention from researchers. On the other hand, the main technical characteristics (such as, energy storage density, energy storage scale, energy storage period, energy storage cost, advantages of technology, disadvantages of technology, future research focus, technology maturity and so on) of three kinds of thermal energy storage techniques are systematically compared in the present review on the basis of summarizing the previous related research work, and the final compared results reveal that because the key features for each thermal energy storage technology are totally different, the selection and extension of application fields for one thermal energy storage technique cannot move forward without a full consideration of its own technical characteristics. Finally, the latest progress on the development of thermal energy storage technologies is further discussed. The technical principles of the recently developed novel thermal energy storage concepts, mainly including of new latent heat storage materials represented by heat-storage ceramics and ionic liquids, the calcium based high temperature thermochemical heat storage systems and hybrid thermal energy storage systems, are introduced in detail, moreover, the technical potential and future outlook of these new thermal energy storage concepts are also addressed.