(124c) Enhanced Phase Change Materials for Ocean Thermal Energy Conversion

Latent heat storage through phase change materials (PCM) has attracted attention in the ocean thermal energy conversion (OTEC) area and unmanned underwater vehicles (UUVs) because it provides economic energy storage solutions with small weight and volume requirements. The goal here is to develop advanced PCM with enhanced thermal conductivity to accelerate the heat transfer rate that will lead to a higher power generation per profile for UUV using PCM technology. Multiwall carbon nanotube (MWNT) modified was used as additives to enhance the thermal conductivity of hexadecane which was selected as the PCM candidate due to its appropriate melting temperature (18 ^oC) and availability. The dispersion of the MWNT in hexadecane was enhanced by the modification of the long carbon chain and the thermal conductivity of the hexadecane can be increased by more than 20% by adding less than 4 vol% modified MWNT. Correlations between the thermal conductivity and onset melting point with the concentration of the added modified MWNT were investigated by a thermal conductivity analyzer and differential scanning calorimeter. Volume expansion of the PCM was also measured to understand the potential impact of the enhanced thermal conductivity on the conversion of thermal energy to hydraulic energy.