Manuel Valdés

Thermoeconomic optimization of combined cycle gas turbine power plants using genetic algorithms

Abstract This paper shows a possible way to achieve a thermoeconomic optimization of combined cycle gas turbine (CCGT) power plants. The optimization has been done using a genetic algorithm, which has been tuned applying it to a single pressure CCGT power plant. Once tuned, the optimization algorithm has been used to evaluate more complex plants, with two and three pressure levels in the heat recovery steam generator (HRSG). The variables considered for the optimization were the thermodynamic parameters that establish the configuration of the HRSG. Two different objective functions are proposed: one minimizes the cost of production per unit of output and the other maximizes the annual cash flow. The results obtained with both functions are compared in order to find the better optimization strategy. The results show that it is possible to find an optimum for every design parameter. This optimum depends on the selected optimization strategy.

Optimization of heat recovery steam generators for combined cycle gas turbine power plants

Abstract The heat recovery steam generator (HRSG) is one of the few components of combined cycle gas turbine power plants tailored for each specific application. Any change in its design would directly affect all the variables of the cycle and therefore the availability of tools for its optimization is of the greatest relevance. This paper presents a method for the optimization of the HRSG based on the application of influence coefficients. The influence coefficients are a useful mathematical tool in design optimization problems. They are obtained after solving the equations of the system through the Newton–Raphson method. The main advantage of the proposed method is that it permits a better understanding of the influence of the design parameters on the cycle performance. The study of the optimization of the distribution of the boiler area between its different components is presented as an example of the proposed technique.

The Influence of Atmospheric Conditions on the Performance of Combined Cycle Gas Turbine Power Plants

This paper deals with the calculation of the ambient conditions influence on combined cycle gas turbine (CCGT) power and efficiency. The main parameters influencing the CCGT performances when ambient conditions change are the air density and the steam condenser pressure. An 800 MW CCGT is studied in order to obtain numerical results in a particular case. This power plant is analyzed working with different condenser cooling techniques (direct or indirect cooling with open or closed circuits) at both 100% and 50% load. The results show that power output drops by 0.60% to 0.65% are to be expected for every 1 °C rise in ambient temperature and by 0.13% to 0.14% for every 1 mbar decrease in ambient pressure. The efficiencies are affected to a lesser extent since some of the gas turbine waste energy is recovered in the heat recovery steam generator and the steam turbine power is almost constant.Copyright

On existence of trends applicable to thermoeconomic optimisation of combined cycle gas turbine power plants

This paper aims at the influence of the nominal power on the design configuration of combined cycle gas turbine (CCGT) power plants. This is achieved by means of a thermoeconomic model aimed at the minimisation of the power plant cost. The present work starts with the establishment of trends in existing commercial gas turbines. Based on these, other trends are found for the design of the whole CCGT, leading to the assessment of the most suitable heat recovery steam generator type and the optimal design parameters. Finally, an analysis of the influence of fuel price on the design configuration is carried out. This serves two purposes: to observe the dependence of economic results with fuel prices and to determine whether fuel price variations might influence the previously established trends in the CCGT design.

Thermoeconomic Coherence: A Methodology for the Analysis and Optimisation of Thermal Systems

In the field of thermal systems, different approaches and methodologies have been proposed to merge thermodynamics and economics. They are usually referred as thermoeconomic methodologies and their objective is to find the optimum design of the thermal system given a specific objective function. Some thermoeconomic analyses go beyond that objective and attempt to find whether every component of the system is correctly designed or to quantify the inefficiencies of the components in economic terms. This paper takes another step in that direction and presents a new methodology to measure the thermoeconomic coherence of thermal systems, as well as the contribution of each parameter of the system to that coherence. It is based on the equality of marginal costs in the optimum. The methodology establishes a criterion to design coherently the system. Additionally, it may be used to evaluate how much a specific design is far from the optimum, which components are undersized or oversized and to measure the strength of the restrictions of the system. Finally, it may be extended to the analysis of uncertainties of the design process, providing a coherent design and sizing of the components with high uncertainties.