Techno-economic analysis of waste heat recovery systems for wet-cooled combined cycle power plants

Increasing ambient temperature negatively impacts the performance of natural gas combined cycle (NGCC) power plants. There have been multiple approaches to mitigate this performance reduction by chilling the compressor inlet air of the gas turbine, as well as by recovering the waste heat emanating from the power plant to generate additional power. In the present study, a detailed techno-economic assessment on the application of different types of waste heat recovery systems used to chill the compressor inlet air has been assessed. A simplified thermodynamic and heat transfer model is developed to predict the performance of an evaporatively cooled NGCC at varying ambient conditions. By taking typical meteorological year (TMY3) hourly weather data for two different locations - Los Angeles, California and Houston, Texas - the yearly output for a 565 MW plant is predicted at a 100% capacity factor. The feasibilities of different waste heat recovery (WHR) systems including a flue gas driven absorption chiller, a steam driven absorption chiller, and an electrically driven vapor compression chiller are assessed by calculating the levelized cost of electricity (LCOE) for each scenario. The results of the analysis showed that, for a fixed WHR system costs (i.e., $ per kWth), the system powered by flue gas generated the smallest LCOE, followed by the mechanically-driven vapor compression, steam-heated chiller, and, finally, the gas turbine exhaust chiller for both the locations at all COP combinations. The analysis also investigated the impact of fixed investments cost, and the flue gas system again yielded the smallest LCOE, while still yielding a lower LCOE than at baseline case over a wide range of COP and tolerable cooling costs for both locations.