Modeling and performance evaluation of a thermal power plant converted to a natural gas combined cycle power plant by full repowering method

Increasing electricity demand as a result of industrial development brings with it the need for larger installed power generation capacity. However, existing regulations, capital costs of new equipment, time-dependent constraints, and public opposition against construction of new power plants pose a strong challenge for greenfield power generation projects. These compelling factors have caused the "full repowering" concept to gain importance again in recent years. "Ambarlı Repowering Project" is a "Full Repowering by Conversion to Combined Cycle Power Plant" project that is the first of its kind in Turkey and is equaled in magnitude and complexity by only a handful of worldwide examples. In this context the existing heavy fuel-oil fired steam power plant was repowered by conversion to natural gas fired combined cycle power plant. Here, in this thesis, initial performance calculations of the existing steam turbine and achievable power output after rehabilitation are evaluated in detail. Parameters such as inlet temperature, pressure, and steam mass flow are defined as boundary conditions for the simulation model of the repowered Ambarlı Power Plant that allows a comprehensive evaluation of the performance of the combined cycle power plant. An in-depth validation study is conducted to verify the outputs of the developed model by comparing them with the official performance test results. The results show that with only a 25% increase in heat rejection from the condenser, the total capacity of a conventional steam power plant can be increased by 203%. Moreover, it is found that repowering has significant positive environmental effects such as reduction of NOx, SOx, and CO2 emissions in addition to economic benefits. Therefore, it is expected that this novel thesis study, which has been validated with official performance tests, will shed light on similar projects to be made in the future.