Solar energy conversion and storage through sulphur-based thermochemical cycles implemented on centrifugal particle receivers

The recently demonstrated potential of centrifugal particle receivers to provide hot particle streams of temperatures above 950°C as heat transfer fluid and solar energy storage material in the form of sensible heat opens new possibilities in performing endothermic chemical reactions that take place below this temperature in solar tower plants. Of particular interest among such reactions is the SO3 splitting/sulphuric acid decomposition scheme, common to all sulphur-based thermochemical cycles. This set of reactions, instead of being implemented on a solar receiver/reactor, can be performed in a reactor/heat exchanger configuration downstream of the solar receiver using the enthalpy of the hot solid particles stream heated in the receiver. Two alternative concepts of performing this reaction are examined and analysed, focusing on the different catalytic reactor configurations to be employed and the long-term characterization of suitable catalytic compositions. Oxide-based catalytic systems in the form of particles, honeycombs and foams have been tested in a lab-scale reactor demonstrating high SO3 conversions at 850°C, 60%, corresponding to 68% of equilibrium value, with less than 15% loss of performance after more than 1000 h on SO3 vapours stream. REFERENCES