In this paper, a novel thermal energy storage (TES) system based on a thermo-sensitive magnetic fluid (MF) in a porous medium is proposed to store low-temperature thermal energy. In order to have a better understanding about the fluid flow and heat-transfer mechanism in the TES system, four different configurations, using ferrofluid as the basic fluid and either copper foam or porous carbon with different porosity (90 and 100 PPI, respectively) as the packed bed, are investigated experimentally. Furthermore, two thermal performance parameters are evaluated during the heat charging cycle, which are thermal storage velocity and thermal storage capacity of the materials under a range of magnetic field strength. It is shown that heat conduction is the primary heat-transfer mechanism in copper foam TES system, while magnetic thermal convection of the magnetic fluid is the dominating heat-transfer mechanism in the porous carbon TES. In practical applications in small-scale systems, the 90-PPI copper foam should be selected among the four porous materials because of its cost efficiency, while porous carbon should be used in industrial scale systems because of its sensitivity to magnetic field and cost efficiency.