• Energy Research
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Abstract Renewable energy generation is inherently variable. For example, solar energy shows seasonal (summer–winter), daily (day–night), and hourly (clouds) variations. Thermal energy storage (TES) systems correct this mismatch between the supply and demand of the thermal energy. Hence, TES is a key cross-sectional technology with growing present and future importance for utilizing volatile renewable sources (e.g., wind and photovoltaics) and energy efficiency improvements. This chapter gives a broad overview of different options and challenges for TES utilization in a high-temperature field. The chapter structure follows the value chain of TES development from material via component to system integration research and development aspects. The structure of this chapter is based on the classification commonly adopted in the academic literature, which distinguishes between three major TES types: sensible, latent, and thermochemical storage. The chapter focuses on high-temperature applications in the area of concentrating solar power generation and operation temperatures beyond 300°C.

High supercooling and single functionalization are the main barriers to the large-scale application of microencapsulated phase-change materials (PCMs) in the construction industry. To address these issues, we propose a new inorganic microencapsulated PCM, PW@CaWO4, which was synthesized via the in situ polymerization method using inorganic CaWO4 as shell and phase-change paraffin wax (PW) as core. We investigated the effects of different emulsifiers and core-to-shell ratios on microcapsule properties and found that the PW@CaWO4 microcapsules have regular spherical topography and good uniformity in particle size. During the synthesis process, the CaWO4 shell provides convenient conditions for heterogeneous nucleation of PW and effectively reduces the supercooling degree. The minimum supercooling degree of the PW@CaWO4 microcapsules is only 1.00 ± 0.08 °C, which is 3.41 °C lower than that of PW. Moreover, the PW@CaWO4 microcapsules can absorb ultraviolet radiation and exhibit fluorescence, which originates from the peculiar WO42– structure in the CaWO4 shell, eliminating the need for doping other light-activating ions into the shell. The newly prepared microcapsules possess several advantages, including suitable particle size, low supercooling, good heat storage, high thermal conductivity, good short-wave ultraviolet absorption, peculiar fluorescence, excellent proof of leakage, and so on. The microcapsules can be applied to fluorescent architectural energy-saving coatings.