The improved distribution method of negentropy and performance evaluation of CCPPs based on the structure theory of thermoeconomics

In order to evaluate the performance of components in the large gas-fired combined cycle power plant (CCPP), an improved thermoeconomic analysis method based on the structure theory of thermoeconomics is proposed. First, the fuel-product model is established; the productive structure and the distribution method of negentropy are modified. Negentropy produced and consumed in the gas turbine cycle is also considered. It is proved that the method is reasonable and practical. The exergy cost by the method is higher than that by the traditional method. Then, thermoeconomic model based on structure theory is built by using the improved distribution method of negentropy. Compared with matrix model of thermoeconomics, the accuracy and the effectiveness of the model are verified. The relative error is less than 3%, which is within the permissible range of engineering. Afterwards, relative cost difference and exergoeconomic factor are calculated. The improved relative cost difference is put forward through introduction of non-energy weighting factor. The results indicate that the heat recovery steam generator (HRSG) has a very great potential improvement. The investment on the steam turbine (ST) and the irreversibility of the combustion chamber (CC) should also be paid more attention, the decrease of which makes a great contribution to the decrease of thermoeconomic cost. It shows that the new evaluation index for components of CCPP is reasonable and will support the researches on thermoeconomic optimization of CCPPs.