Highly stable nanoemulsions of a phase change material (PCM) such as tetradecane and beeswax in water have been developed using common surfactants and a low energy emulsification method by CCNY and IRSTEA researchers. However, their rheological and heat transfer characteristics must be studied extensively to utilize them in practical thermal energy storage systems. Nanoemulsions with a mean particle size of ~200 nm have been shown to be stable with no significant phase separation for more than one year. Emulsion viscosity increases significantly when the solid fraction exceeds 10%, which is much lower than in ice slurries. Further investigations are necessary to obtain lower viscosities at higher solid fractions to achieve a greater thermal storage capacity. In forced convection experiments, thermal non-equilibrium effects and unusual instabilities (large amplitude oscillations in the flow rate and heated tube surface temperatures) have been observed at the phase change temperature in both nanoemulsions and gas hydrate slurries.