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Communication Dans Un Congrès Année : 2013

Study of absorption couples used in solar heat storage process

E. Lefebvre
  • Fonction : Auteur
S. Bennici
  • Fonction : Auteur
E. Gagniere
D. Mangin
A. Auroux
  • Fonction : Auteur

Résumé

Thermal solar energy storage is an interesting way of reducing gas emissions. This storage can be achieved using water vapour absorption-desorption in a binary or ternary system with a desiccant salt-like lithium bromide, lithium chloride, calcium chloride, etc. As illustrated in the figure below, in summer, solar energy dehydrates a concentrated solution of salt in the generator. The water vapour is condensed and stored in the water tank. The resulting more concentrated solution is stored in a semi crystallized form in a second tank. In winter, the previous condensed water is evaporated at low temperature, using geothermal source, and absorbed by the highly concentrated salt solution in the absorber, thus generating thermal energy. Therefore, in order to design the most adaptable system for this process, it is important to determine its thermal behaviour. In this work, dissolution and dilution enthalpies and solubilities were studied for five anhydrous salts (lithium chloride, lithium bromide, zinc bromide, zinc chloride and sodium thiocyanate) by titration calorimetry. Experiments were carried out at different temperatures from 25°C to 40°C. On one hand, the plot of cumulated enthalpy versus coefficient ą= n_salt/n_solute allows determining the dissolution and dilution enthalpies. One the other hand, these experiments allow to calculate the salt solubility and its kinetics for each temperature. The results have been compared to theoretical data. Moreover, salt hydration characteristics were studied. Indeed, the concentrated solution is crystallized in the tank to increase the storage density and reduce the storage tank size. Therefore, the salt should crystallize in anhydrous or at least in monohydrated form. The five anhydrous salts were hydrated at room temperature. They were analysed using thermogravimetry (TG) and differential scanning calorimetry (DSC) to determine the transition temperature of the hydrated form and its corresponding dehydration enthalpy.
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Dates et versions

hal-00802710 , version 1 (20-03-2013)

Identifiants

  • HAL Id : hal-00802710 , version 1

Citer

E. Lefebvre, S. Bennici, E. Gagniere, D. Mangin, A. Auroux. Study of absorption couples used in solar heat storage process. Journée d'Etudes des Equilibres entre Phases, Mar 2013, Nancy, France. ⟨hal-00802710⟩
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