One of the challenges in applying phase change materials (solid-liquid PCM) is the difficulty in shape stabilization. Previous polymer encapsulated PCMs are not cost effective and hard to manufacture for large scale applications. In this work, we applied nanoporous activated carbon (AC) as an encapsulation material, reported the PCM charging process and the resulting thermophysical properties of AC encapsulated PCMs. Two types of activated carbon ? the powder type and the granular type ? was investigated and the thermal conductivity of the powder type was larger than the granular type due to the smaller particle sizes and resulting higher solid fraction. Our FT-IR measurements also shows that there was no chemical reaction between the AC and PCM, and DSC measurements show the effective heat capacity is maintained. The power AC encapsulated PCM maintained its performance even after 60 hours of thermal cycling. This work shows that AC encapsulation would be a practical method to apply PCMs to various practical applications.