International audienceSolar thermal energy represents an increasingly attractive renewable source.However,to provide continuous availability of this energy,it must be stored. This paper presents the state of the art on high temperature(573-1273K)solar thermal energy storage based on chemical reactions,which seems to be the most advantageous one for long-term storage. The paper summarizes the numerical,experimental and technological studies done so far. Each system is described and the advantages and drawbacks of each reaction couple are considered
OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 15980To link to this article : Michel Ca(OH)2/CaO reversible reaction in a fluidized bed reactor for thermochemical heat storage.
AbstractThermal energy storage (TES) is a key factor for increasing the efficiency of concentrated solar power plants. TES using a reversible chemical reaction appears to be a promising technology for high energy density thermal storage (100-500 kW h m À3 ), at high temperature (up to 1000°C) and during a long period (24 h to several months). This paper details an experimental study to carry out the reversible reaction Ca(OH) 2(s) + DH r () CaO (s) + H 2 O (g) in a fluidized bed (FB) reactor. The 4 lm Ca(OH) 2 powder fluidization has been performed with an appropriate proportion of inert easy-to-fluidize particles. Then, Ca(OH) 2 dehydration and CaO hydration have been implemented in a FB reactor and 50 cycles have been reached. The mean energy density obtained is 60 kW h m À3 solid_mixture which amounts to a promising energy density of 156 kW h m À3 Ca(OH) 2 -bulk if the reactants and the easy-to-fluidize particles are separated. The results demonstrated the feasibility of the implementation of the Ca(OH) 2 /CaO thermochemical heat storage in a fluidized bed reactor.
The CaO/Ca(OH) 2 hydration/dehydration chemical loop has long been recognized as a potential candidate for application in energy storage systems for concentrated solar plants. However, the technology still remains at a conceptual level because little information has been published on the performance of the key reactors in the system. In this work, we experimentally investigate the hydration and dehydration reactors in a 5.5 kW th batch fluidized bed reactor, in conditions relevant to larger systems (superficial gas velocities of up to 0.53 m/s, temperatures of up to 500ºC for dehydration, input H 2 O (v) fractions between 0 and 0.8 etc.). Furthermore, to assist in the interpretation of the experimental results, a standard 1D bubbling reactor model has been formulated and fitted to the experimental results by including kinetic information at particle level independently measured in a thermogravimetric apparatus. The results indicate that the hydration reaction is mainly controlled by the slow kinetics of the CaO material tested while significant emulsion-bubble mass-transfer resistances were identified during dehydration due to the much faster dehydration kinetics.
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