Electrospun form-stable phase change materials (FSPCMs) emit 85-90 wt% of organic solvents and suffer from inherent poor thermal conductivity. We developed eco-friendly PEG/PVA/Ag composite fiber-based FSPCM by electrospinning an aqueous solution of PEG/PVA/AgNO3, followed by ultraviolet (UV) irradiation directly. The composite fibers with 45 wt% PEG showed an optimal smooth, cylindrical, and uniform morphology and a diameter of 80-300 nm. The UV irradiation process accelerating the formation of facecentered cubic Ag nanoparticles (AgNPs) and showed no significant effect on the morphology of the composite fibers. The composite fibers melted at 45.9 degrees C and had a latent heat of 67.5J/g, which is comparable to that of the previously reported phase-change fibers. They exhibited robust thermal, chemical, and morphological stability after 2000 melting/cooling cycles. In addition, they also showed significantly high thermal energy transfer efficiency because of the presence of in-situ reduced AgNPs. These NPs acted as heat conductive bridges and facilitated the formation of continuous heat conduction networks or efficient percolating pathways for heat flow. Moreover, the electrospinning process did not require any organic solvent, and hence was eco-friendly, non-hazardous, and cost-effective. Therefore, it is suitable for large-scale thermal energy storage and environmental protection applications. (C) 2019 Elsevier Ltd. All rights reserved.