Improving Air-Cooled Condenser Performance in Combined Cycle Power Plants

Abstract

It has been recognized in recent times that air-cooled condensers (ACCs) are environmentally preferable to the traditional water-cooled condensers for rejecting heat in combined-cycle power plants (CCPPs). However, a drawback of ACCs is that their performance can decline with increasing ambient air temperature. A new approach is proposed in this paper that has the potential to alleviate this drawback of ACCs. In this approach, a chilled-water thermal energy storage system (TES) is used to precool the inflow air to the ACC whenever the ambient air temperature increases above the design air inlet temperature. The temperature of the TES system is maintained by an absorption refrigeration system (ARS) driven by low-quality waste heat from the CCPP. A process model integrating the CCPP with the ARS and the TES has been developed to optimize the volume of the TES. A 500MW CCPP with steam turbine net output of 170.9MW was chosen to evaluate the application of this approach for a power plant to be located in southern New Mexico. This analysis showed that a tank volume of 4,500m3 will be required to maintain the air temperature at the inlet to the ACC at the design value of 20°C throughout the year. Simulations under ambient air temperatures up to 40°C indicated that the proposed system is capable of maintaining the rated net power output of the plant with minimal fluctuations. Simulations also showed that TES tank volume is most sensitive to the design air inlet temperature to the ACC—an increase of this temperature by 1°C can result in at least 25% reduction in the volume.