Here, m_ is the mass flow rate of the working fluid, h and s are
respectively the specific enthalpy and specific entropy of the working fluid at the state point for which the physical exergy is calculated, and ho and so are respectively the specific enthalpy and specific entropy of the working fluid at environment conditions.
For the receiver, the rate of exergy destruction was calculated as the difference in the values of physical exergy available in the solar radiation incident on the receiver surface and the exergy absorbed by the working fluid (which is, in turn, the difference in the values of physical exergy of the working fluid across the receiver). This value includes both the exergy that is destroyed during the transfer of heat from solar radiation to the working fluid, and the exergy that is lost to the environment due to the thermal losses in the receiver.