Thermal energy is one of the most prospective clean and renewable energy because it is freely available from industrial waste gas and solar radiation every day. With growing global energy consumption, there is increased need for research of thermal energy storage (TES) in critical areas. TES is a technology that conserves surplus thermal energy by a suitable medium so that the stored energy can be draw upon at a later time and usefully re-applied in a given operation. TES is useful not only for addressing the mismatch between the supply and demand of energy in the space and time, but also largely increasing the energy efficiency in industrial productions and expanding energy resources from nature. In general, thermal energy can be stored at different temperatures by three main forms: sensible heat storage (SHS) by heating a liquid or solid storage medium (e.g., water, mineral oil, molten salts, sand, rocks and concrete), latent heat storage (LHS) by using PCMs and thermo-chemical heat storage by chemical reactions. The common materials, main requirements and application fields of TES system are generalized by the latest reviews. Among the three TES forms, LHS using phase change materials (PCMs) is the most competitive form due to its indisputable advantages including large energy storage density, small temperature swing during heat storage process, low cost, chemical stability and non-corrosiveness.
As fibrous form-stable PCMs, over the last 30 years, phase change fibers (PCFs) have been extensively investigated and applied as high-performance nonwoven fabrics and coatings. As a prospective renewable and clean material, PCFs with micro-scale have been successfully prepared by melt/wet spinning for applications in TES and temperature regulation. With the development of fiber manufacturing techniques, e.g. electrospinning, ultrafine PCFs for thermoregulation materials have been exploited and investigated in the last decade. Here, the PCFs based on phase change materials/cellulose derivative blends were fabricated successfully via various electrospinning technologies. Especially, a series of polyethylene glycol /cellulose acetate (PEG/CA) ultrafine PCFs fabricated by uniaxial electrospinning and coaxial electrospinning were systematically investigated. The morphology, thermal properties and tensile properties of the PCFs were investigated by SEM, TEM, DSC, WAXS, respectively. Results revealed that PEG weight fraction has crucial influence on the thermal properties of PCFs, and the thermal stability and water-resistivity of PCFs have improved obviously after the surface crosslinking. The fibers with reliable thermal properties are suitable and promising in serving as TES and thermoregulation materials.

Keywords: Electrospinning; Cellulose derivatives; Ultrafine fibers; Thermal properties; Thermoregulation