Thermal energy storage with Phase Change Materials (PCMs) can be used to fill the gap between energy supply and demand. The main reason preventing their widespread application is the low thermal conductivity of PCMs which makes the systems to have slow energy storage and recovery rates. This study achieved better PCM melting rate with novel fin configuration in triplex-tube storage compared to the use of nanoparticles. This will eliminate problems such as associated viscosity increases and sedimentation. Since heat transfer at different parts of the unit is not the same, a variety of fin arrangements were investigated with numerical analyses of the PCM melting in the triplex-tube. Significant increases in the rate of PCM melting were achieved using special arrangements of fins. Results show that using long fins at the lower half of the storage unit where conduction dominates resulted in accelerated melting. It was further found that using fewer and relatively shorter fins at the upper half of the unit results in better performance. Using this arrangement in the storage unit containing pure PCM achieved significantly faster melting rate compared to the use of fin-nanoparticles combination or nano-enhanced PCM in the same volume of the triplex-tube heat exchanger. (C) 2018 Elsevier Ltd. All rights reserved.