This study was aimed at preparing the capric acid (CA)/lauric acid (LA) and capric acid (CA)/myristic acid (MA) mixtures as novel phase change materials (PCMs) for low-temperature latent heat thermal energy storage (LHTES) and to determine their thermal properties and long-term thermal reliability by using differential scanning calorimetry analysis technique. The DSC results indicated that the CA/LA and CA/MA mixtures with eutectic composition were suitable PCMs for low-temperature LHTES applications in terms of melting temperature (18.51 degrees C for CA/LA and 21.70 degrees C for CA/MA mixture) and latent heat of fusion (162.85 J/g CA/LA and 168.37 J/g for CA/MA mixture). Accelerated thermal cycling test showed that the phase change temperatures and the latent heats of the PCMs were in decreasing trend, but the variations with increasing thermal cycling number were irregular. The probable reasons of the changes in thermal properties of the PCMs with increasing thermal cycling number were also investigated using Fourier transform infrared spectroscopy method. Based on all results, it was concluded that the prepared and tested CA/LA and CA/MA mixtures as novel PCMs have good thermal properties and long-term thermal reliability for low-temperature LHTES systems used in solar passive heating and cooling applications.