Thermal characterization of a solid-solid phase change material for energy storage application

International audienceThermal 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

Thermal characterization of a solid-solid phase change material for energy storage application

International audienceThermal 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

On the dynamic modeling of Brayton cycle power conversion systems with the CATHARE-3 code

International audienceAs the share of intermittent energy sources is increasing, the dynamic modeling of thermal power plants including their power conversion system gets researchers' attention. Recent applications require transient simulations of high-pressure nitrogen closed Brayton cycle for which the ideal gas assumption is no longer verified. In this work, the REFPROP real gas equation of state and pressure drop correlations suitable for high Reynolds numbers have been implemented in the CATHARE-3 code. Moreover, new real gas turbomachinery and sonic flow models have been developed and integrated in the code. Relative errors obtained for the nominal state of a high-pressure nitrogen closed Brayton cycle are in the range −3%/+0.8%. A detailed analysis of real gas effects is carried out on the heat exchangers heat flux and the piping pressure losses. The new sonic flow computed during a loss of coolant accident is in the best possible agreement with literature experimental results. With regard to the turbomachinery, the new real gas model creates a pressure dependence that brings compressors closer to the choke region when the pressure drops in the cycle. This work is expected to provide an efficient and reliable simulation tool for transient analysis of real gas closed Brayton cycles

Xylitol used as phase change material: Nucleation mechanisms of the overcooling rupture by stirring

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Triggering Xylitol crystallization in a 42 kWhth shell and tubes latent heat thermal energy storage system

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Xylitol used as phase change material: Nucleation mechanisms of the supercooling rupture by stirring

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Xylitol used as phase change material: Nucleation mechanisms of the overcooling rupture by stirring

International audienc

Xylitol used as phase change material: Nucleation mechanisms of the overcooling rupture by stirring

International audienc

Xylitol used as phase change material: Nucleation mechanisms of the overcooling rupture by stirring

International audienc