A Techno-economic Study on the Waste Heat Recovery Options for Wet Cooled Natural Gas Combined Cycle Power Plants

摘要

Increasing ambient temperature is known to have negative impacts on the performance of gas turbine and combined cycle power plants. There have been multiple approaches to mitigate this performance reduction. One such method involves cooling of the gas turbine inlet air. There are several different commercial techniques available, but they are energy intensive and require large capital investments. One potential option for cost reduction is to recover the waste heat emanating from the power plants to operate thermally activated cooling systems to cool the turbine inlet air. In this study, a 565 MW natural gas combined cycle power plant subjected to different waste heat recovery scenarios and gas turbine inlet chilling is assessed. A simplified thermodynamic and heat transfer model is developed to predict the performance of an evaporatively cooled NGCC power plant 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 this plant is predicted at a 100% capacity factor. The feasibilities of different waste heat recovery (WHR) systems including a gas turbine exhaust driven absorption chiller, 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. In each of these cases, a parametric analysis was performed on the COP and the costs ($ per kWth) of the system. In these cases, the COP was varied from 0.2 to 2.0 (increments of 0.2), whereas the costs were varied logarithmically from $10 to $10,000 per kWth. The results of the analysis showed that for a fixed WHR system cost (i.e., $ per kW th), the system powered by flue gas generated the lowest LCOE, followed by the electrically-driven vapor compression chiller, steam-heated chiller, and finally, the gas turbine exhaust driven chiller for both geographic locations at all COP combinations. The analysis also investigated the impact of fixed investment cost, and the flue gas system again yielded the smallest LCOE and yielded a lower LCOE than the baseline case (no WHR) over a wide range of COPs. The maximum costs each of these systems could tolerate before the LCOE is higher than the baseline case was also determined. The flue gas driven absorption system had the highest tolerable costs at all COP combinations, followed by the vapor compression, steam, and gas turbine exhaust driven systems. As such, the flue gas powered system was identified as the most economic system to reduce the LCOE from the baseline case for a wide range of COP combinations at high tolerable costs for these two locations.