Thermal energy represents half of the primary energy used in Europe and is one of the main contributor of greenhouse gas emission. Integration of renewable thermal energy sources, such as biomass, solar thermal, geothermal or wasted heat is then a major stake for near future. Thermal Energy Storage (TES) is one of the key component that can help the development of renewable thermal energy in domains like urban heating network or industrial processes, allowing to smooth peaks of demand, to manage the balance with the supply and then to minimize the use of fossil energy. Most of the TES currently operated in the world are based on sensible heat by increasing and decreasing the temperature of a material such as water, thermal oil, molten salt, rock… The use of Phase Change Materials (PCM) as storage medium enable to reach higher energy density for a large temperature range (i.e. 30°C to 1 000 °C [1]). Current technologies use solid-liquid phase PCM as TES medium and reach energy densities from 100 MJ.m-3 for paraffin to 1 000 MJ.m-3 for salt hydrates. These systems show some drawbacks like the presence of a liquid phase which may imply leakage, undercooling or large volume variation of about 10 to 20%V/V upon phase transformation [2] which leads to mechanical stresses for the storage vessel. An alternative solution consists in using solid-solid PCM with about 5-10%V/V phase change variation [1] and that could even later be used as structural material of the TES systems. This study proposes to investigate and compare the thermal behavior of a classical solid-liquid paraffin and a polyalcohol as a solid-solid PCM. Both materials have first been analyzed by calorimetry and then characterized into a thermal bench. The bench used is composed of two thermal loops, a heat exchanger with circular metallic fins composes the former test section. PCM fills the space between the fins. Temperature into the section is measured and used to calculate the heat flux and the energy stored into the system to compare the properties of the solid-solid PCM with the solid-liquid classical paraffin as reference. Latent heat, energy density and thermal conductivity are compared. Furthermore, several thermal cycles are done to study the effect of the aging on both materials.