International Journal of Thermophysics (2018) 39:112 https://doi.org/10.1007/s10765-018-2437-5 Innovative Design of a Thermal Battery: Influence of Carbon Nanotubes Concentration on Thermal Storage Characteristics Bekir S. Yilbas 1,2 · Muhammad K. Anwar 3 · Abdullah Al-Sharafi 1 Received: 15 March 2017 / Accepted: 13 August 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Innovative design of a thermal battery resembling the solar thermal receiver is intro- duced. The fully connected aluminum meshes and the phase change material (NaCO 3 ) 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 ther- mal 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 dis- turbs the uniform-like temperature distribution inside the thermal battery when only phase change material is used. The presence of MWCNT enhances the thermal con- ductivity 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 concentra- tion > 6 % in the phase change material does not significantly shorten the total melting duration of the energy storing medium. Keywords Carbon nanotubes · Concentrated solar receiver · Phase change material · Thermal battery B Bekir S. Yilbas bsyilbas@kfupm.edu.sa 1 Mechanical Engineering Department, KFUPM, Dhahran 31261, Saudi Arabia 2 Center of Excellence Renewable Energy, KFUPM, Box 1913, Dhahran 31261, Saudi Arabia 3 University of Management and Technology, Lahore, Pakistan 0123456789().: V,-vol 123