Towards Flexible Power Generation Short-term Optimization of a Combined Cycle Power Plant Integrated with an Inlet Air Conditioning Unit

Abstract: Combined cycle gas turbine power plants (CCGT), as part of the electricity generation fleet, are required to improve their flexibility to help balance the power system under new scenarios with high shares of variable renewable sources. Among the different possibilities to enhance the power plant performance, an inlet air conditioning unit offers the benefit of power augmentation and “minimum environmental load” reduction by controlling the gas turbine intake temperature using cold thermal energy storage and a heat pump. In this thesis, an evaluation of the conditioning unit impact over a power-oriented CCGT under a day-ahead optimized operation strategy is presented. To establish the hourly dispatch of the power plant and the right operation mode of the inlet condition unit bringing the desired benefits, a mixed-integer linear optimization was formulated aiming to maximize the operational profit of the plant within a 24 hours horizon. To assess the impact of the proposed unit operating under this control strategy, annual simulations of a reference power plant were developed with and without the unit, allowing to a comparison of their performance by means of technical and economic indicators. Furthermore, a case study changing equipment sizes was performed in order to identify trends of the power plant performance related to such parameters; and lastly, a sensitivity analysis on market conditions to test the control strategy response was included. The results indicate that the inlet conditioning unit together with the dispatch optimization increase the power plant operational profit trough the gain of power variation over peak and off-peak periods. For the specific case study in northern Italy, it is shown that a power plant integrated with the conditioning unit is more profitable in terms of net present value based on the undertaken investment figures. Related to the technical performance, it also shows that the unit reduces by 1,34% the minimal environmental load when part-load operations are required and that it can increase the net power output by 0.17% annually. All in all, this study presents the benefits of a dispatch optimization strategy when couple to a novel solution to increase CCGT flexibility.