Evaluation of Electricity Cost in a Growing Market

Abstract

Operating gas turbines at higher firing temperatures has been shown to be more thermally efficient with more power obtained from relatively less fuel. There is, however, an associated slight increase in operating and maintenance costs at higher power settings. This paper studies the relationship between gas turbine power setting, the hot gas-path components’ life consumption, operating and maintenance cost and how these parameters can affect the cost of electricity. A 165 MW gas turbine power plant is modelled and investigated with a comparative turbine blade lifing model that performs stress and thermal analysis, and creep life estimation using the parametric Larson Miller method. The outcomes of this analysis are then linked to an economic model to calculate the cost of generating electricity. The results shows that the optimum cost of electricity does not coincide with the lowest TET or power setting as would be expected when taking into account the creep life of the blade. This is because although lower TET results in improved component life, it will also result in lower thermal efficiency which is found to have a more significant impact on the overall electricity cost. In other words, the cost of electricity will increase at low TETs due to reduced thermal efficiency. On the other hand the cost of electricity will also increase at high TETs due to reduced turbine blade life that leads to increase in maintenance cost.