Thermal stability enhancement of D-mannitol for latent heat storage applications

Phase change materials (PCM) are suitable to store high thermal energy densities in narrow temperature ranges due to the phase change from solid to liquid. Sugar alcohols are potential PCMs in the temperature range between 100 °C and 250 °C. Their melting enthalpy is higher than the one of most other PCMs, but their latent heat tends to degrade when heated above the melting temperature. In the present study, degradation rates of the sugar alcohol d-mannitol at three temperatures above the melting temperature are examined and strategies to enhance its thermal stability are demonstrated. These are the use of an antioxidant and the exposure to an inert atmosphere. The degradation shows the highest rate for pure d-mannitol under air and the lowest one for a mixture of PCM and antioxidant under argon. The thermal stability of pure d-mannitol under argon is higher than the one for a mixture of d-mannitol and antioxidants under air. The use of antioxidants and argon or their combination yield to an improved stability compared to pure d-mannitol under air, but cannot stop the degradation completely under the performed conditions.