Projects : Gas Turbine Inlet Air-Cooling and Analysis
DPT conducted an economic analysis to evaluate the economic feasibility of installing inlet air-cooling to improve the daytime power output of a proposed simple cycle generation plant in the midwestern US. The project developer, Aquila provided information for the analyses:
- General plant layout
- ISO airflow through the combustion turbine
- Combustion Turbine performance/temperature correction curves for the GE Model PG7121EA gas turbine
- Anticipated number of peak hours daily and months of operation
- Approximate electricity prices (selling on-peak/buying off-peak)
- Approximate natural gas price
The developer suggested the analyses be performed using a maximum daily temperature. However, DPT recommended the economic analyses would be more realistic and probably result in more-cost equipment if NOAA temperature profile data (dry bulb and wet bulb) based on hourly averages using incremental and seasonal temperature changes. Analyses were conducted using NOAA data for the following alternatives:
- CT operation without chiller
- CT operation with evaporative cooling without chiller
- CT operation with 5100T electric air-cooled chiller
- CT operation with 3400T electric air-cooled chiller
- CT operation with 3400T electric-driven water-cooled chiller
- CT operation with gas IC driven chiller (water cooled)
The analyses demonstrated
that a 3400T air-cooled system was more cost effective than the 5100T
air-cooled system, but that it was about 40 to 50 percent more expensive
than a water-cooled system. Total turnkey pricing for the 3400T system
was estimated to be about $3M per CT, which would provide a 4-year ROI.
If chilling was installed on multiple CT's, then economies-of-scale were
estimated to result in a 10% reduction in unit cost for 4 CT's. The report
noted that if an on-site well of sufficient capacity could be developed,
a water-cooled system would be much preferable over the electric chiller
alternative which would reduce the ROI significantly.