Simulation and Optimal Integration of a Heat Recovery Steam Generator with Solar Thermal Energy

With the increasing industrial manufacturing, commercial activities and better living conditions of world population, the consumption of electricity increases steadily. However, the world consumption of fossil fuels, which is the traditional source of electricity, is being reduced due to the impact of air pollution caused by the burning of fossil fuels.The integration of the Combined Cycle (CC) power plant with solar energy have recently been regarded as a good choice to mitigate high consumption of fossil fuels for a better environment for the reason that solar collectors can be coupled with the steam cycle side of CC power plant which is also called a Heat Recovery Steam Generator (HRSG). In this paper, the HRSG of a CC power plant located in Mexico was studied and simulated in ASPEN Plus. Different methods of adding solar thermal energy into the CC system are presented. The concept of solar conversion rate is introduced which is the ratio of net power output increase after the solar thermal energy is integrated into the fossil part of the plant over value of solar thermal energy to quantify the performance of each method of integration. Operational constrains on temperature of the feed water leaving a solar heat exchanger and the extraction ratio of the feed water are introduced. A comparison of solar conversion rates for different methods with different values of solar input, and different flow rates of the feed water were investigated. The results show that heating the feed water leaving the HRSG's superheater and extracting the feed water leaving the evaporator while sending it back to a location after the superheater are most effective ways to achieve the largest solar conversion rate.This paper is based on a real power plant and provides an integration on how to effect and achieve the largest solar conversion rate within reasonable limits of the practical thermal plant operation. This provides guidance on a method to Integrated Solar Combined Cycle Power Plants (ISCC) for largest solar conversion rate.