An innovative electrospun form-stable phase change composite material is fabricated by combining binary fatty acid eutectics of capric-lauric acid (CA-LA) and capric-palmitic acid (CA-PA) as the phase change materials (PCMs) and polyethylene terephthalate (PET) as the supporting matrix. The encapsulated PCM composite fibers are produced by co-electrospinning of different fibers at various PCM-to-PET ratios of 50/100, 70/100, 100/100 and 120/100. Thermal behavior and characteristics of individual fatty acids, fatty acid eutectics and composite fibers as well as the structural morphology of the composite fibers are characterized by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Scanning electron microscopy images revealed that the average diameter of the composite fibers is slightly increased by increasing the PCM contents. Comparison of FT-IR plots for fatty acids and PET with those of composite fibers containing PCMs clearly indicates that no chemical reaction occurred between PCM and PET matrices. In addition, thermogravimetric analysis results have shown that composite fibers have two steps of degradation which correspond to decomposition of PCM molecular chains and PET structure, respectively. Moreover, DSC results have indicated that enthalpy of composite fibers is improved by increasing PCM contents while no considerable change is observed in phase-transition temperature. Compared to previous studies, the present fabricated co-electrospun composite fibers offer wider phase-transition temperature range (-9 to 34 degrees C) and higher enthalpy values even with lower amounts of PCM. Therefore, these composite fibers are very promising for use in near ambient storage and retrieval energy systems. (C) 2016 Published by Elsevier Ltd.