Abstract: Innovative design of a thermal battery resembling the solar thermal receiver is introduced. The fully connected aluminum meshes and the phase change material (NaCO3) with the presence of multiwall carbon nanotubes (MWCNT) are used as the thermal energy storing medium in the thermal battery. The aluminum meshes behave like heat carriers and increase heat diffusion rates, while the use of MWCNT in the phase change material enhances the thermal conductivity of the thermal energy storing medium. The flow field, temperature rise, and liquid fraction are simulated numerically in the thermal battery using the finite element code for various concentrations of MWCNT. The findings revealed that the aluminum meshes improve the thermal conduction in the energy storing medium. Temperature increases locally in the storing medium and disturbs the uniform-like temperature distribution inside the thermal battery when only phase change material is used. The presence of MWCNT enhances the thermal conductivity and minimizes the excessive temperature rise inside the storing medium. In addition, the mixture of phase change material and MWCNT provides almost steady rate of melting inside the thermal battery; however, increasing MWCNT concentration > 6 % in the phase change material does not significantly shorten the total melting duration of the energy storing medium.