Evaluation of reaction characteristics of Na2S2O3.5H2O for thermochemical energy storage

Abstract

In the present study, calorimetric investigations are performed on Na2S2O3.5H2O to determine the dissociation temperature(s), decomposition temperature and reaction enthalpies due to dehydration and hydration, using the DTG-60H instrument. Towards this, heating and single cycle (comprising of sequential dehydration and hydration reactions) tests are performed. The heating tests are performed to measure the dissociation and decomposition temperatures by heating the material’s sample for a temperature up to 600 °C at a heating rate of 5/ 10/ 20 °C/min. The single cycle tests are performed at different hydration temperatures (30 and 50 °C) and durations (30, 60 and 120 min). The results indicate that the dissociation and decomposition temperatures increase with heating rate. The heating tests also helped in determining the material’s reaction enthalpy due to dehydration. Reaction enthalpy due to hydration increases with its duration and decreases as its temperature increases. For the single cycle with 120 min duration and 30 °C temperature of hydration, the calculated energy storage densities are respectively 1.90 and 1.81 GJ/m3. These values are far superior to that of materials used for conventional thermal energy storage methods.