Heat transfer analysis of a latent heat thermal energy storage system using graphite foam for concentrated solar power

A latent heat thermal energy storage (LHTES) system, consisting of a tank filled with a phase-change material and pipes carrying a heat transfer fluid, for a concentrated solar power plant was analyzed. The effect of a relatively new, high thermal conductivity graphite foam was considered in the phase-change material region. An 8-h discharging transient was analyzed for an LHTES system with and without graphite foam. The phase-change front position at the end of the transient was calculated and used to determine the number of heat transfer fluid pipes in the tank. Optimization of the LHTES system was conducted through varying the thermal conductivity of the phase change material/foam combination, the velocity of the heat transfer fluid, and the diameter and wall thickness of the pipes. It is shown that dramatic reductions in number of the pipes can be achieved with the use of the graphite foam in the phase-change material and the turbulent flow.