The Carnot method's advantage is that no external reference values are required to allocate the input to the different output streams; only endogenous process parameters are needed.
Thus, the allocation results remain unbiased of assumptions or external reference values that are open for discussion.
with fPE,F: primary energy factor of the used fuel The reciprocal value of the fuel factor (f-intensity) describes the effective efficiency of the assumed sub-process, which in case of CHP is only responsible for electrical or thermal energy generation.
The quality of the product "thermal energy" is fundamentally determined by the mean temperature level at which this heat is delivered.
Hence, the exergetic efficiency ηx describes how much of the fuel's potential to generate physical work remains in the joint energy products.
with ηx,total = exergetic efficiency of the combined process ηx,el = exergetic efficiency of the virtual electricity-only process ηx,th = exergetic efficiency of the virtual heat-only process The main application area of this method is cogeneration, but it can also be applied to other processes generating a joint products, such as a chiller generating cold and producing waste heat which could be used for low temperature heat demand, or a refinery with different liquid fuels plus heat as an output.
f is a factor for rating the relevant product in the domain of primary energy, or fuel costs, or emissions, etc.