The relationship among the factors determining the thermal efficiency to convert concentrated solar thermal energy to chemical energy by the O2-releasing reaction of the reactive ceramics in the tow-step water splitting process has been studied for the development of rotary-type solar reactors. The α O2-releasing reaction which has been discovered in the present study for Ni-ferrite (NiFe2O4) has a high chemical reaction rate (k = 0.50 mol sec−1/m2). From calculation with the heat transfer equation in terms of heat transfer through the cavity wall with thckness, d (m), and heat absorption by the endothermic process of the O2-releasing reaction with rate constant, k (mol sec−1/m2), it is cralified that the heat flux of 2000 kW/m2 can be absorbed by the α O2-releasing reaction using the cavity wall with the thickness, d = 0.00036 m and thermal conductivity, λ = 70 WK−1m−1. The heat loss in the temperature swing (ΔT = 300K) for the two step water splitting of O2 releasing step (TH = 1773K) and H2 generation step (TL = 1473K) is only 8.3% for the α O2-releasing reaction. However, the O2 releasing reaction of NiFe2O4 in the β region where the reaction rate constant is around 0.0001 mol sec−1/m2, the heat flux of the concentrated solar energy to be used for conversion to chemical energy becomes very low around 300 kW/m2; the heat loss by the temperature swing in the two step water splitting is 87%. It is concluded that the α O2-releasing reaction can be used for the rotary-type solar reactor to convert the concentrated solar thermal energy to chemical energy with a high efficiency.
- Advanced Energy Systems Division and Solar Energy Division
O2 Releasing Reactivity of Ceramics for Rotary-Type Solar Reactor With Two-Step H2O Splitting
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Tamaura, Y, & Kaneko, H. "O2 Releasing Reactivity of Ceramics for Rotary-Type Solar Reactor With Two-Step H2O Splitting." Proceedings of the ASME 2009 3rd International Conference on Energy Sustainability collocated with the Heat Transfer and InterPACK09 Conferences. ASME 2009 3rd International Conference on Energy Sustainability, Volume 2. San Francisco, California, USA. July 19–23, 2009. pp. 497-505. ASME. https://doi.org/10.1115/ES2009-90421
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