Thermodynamic Considerations for the Design of Solar-Thermal Chemical Processes

The maximum efficiency of a solar reactor/receiver is limited not by the Carnot efficiency, but rather by the product of the Carnot efficiency and a factor involving both the enthalpy and entropy changes occurring as a result of the chemical reaction. This limiting efficiency can be greater than the Carnot efficiency when the entropy change is positive, and is a function of several parameters including the standard property changes of the reaction, inlet and outlet stream conditions, reactor temperature, conversion, and relative amounts of inert gas. By including this factor in the overall limitation on the reactor efficiency, both the optimal reactor temperature for a given concentration ratio, and the concentration ratio required to achieve a given temperature and efficiency can, in many cases, be found to shift to lower values.