Evaluation of Cooling Tower Performance Based on Range, Approach and Effectiveness Parameters on Geothermal Power Plant Turbine Performance

Abstract

This study evaluates the thermal performance of the cooling tower at PT. Geo Dipa Energi Unit Patuha, a 60 MW single-flash geothermal power plant, using cooling-water temperature range, approach, and effectiveness, and examines their statistical relationships with condenser pressure and turbine output power. Operational data were obtained from the plant Distributed Control System (DCS) at two-hour intervals during January–June 2026. After validation, 1,090 of 1,104 records (98.8%) were retained. The cooling-water temperature range, defined as the difference between return and supply temperatures, remained relatively stable (mean 24.65°C, SD 0.24°C). Because range is a temperature difference, it is not itself a measure of heat-rejection rate; the latter requires cooling-water mass flow rate and specific heat according to Q̇ = ṁCp(T1−T2). The approach ranged from 2.38°C to 12.33°C and effectiveness from 66.43% to 91.15%. Wet-bulb temperature was positively associated with cooling-water supply temperature (r = 0.704). Cooling-water supply temperature showed a very strong association with condenser pressure (r = 0.975, R² = 0.951; Vacuum = 5.76T2 − 20.33), while condenser pressure was negatively associated with turbine output power (r = −0.716, R² = 0.512), with an estimated 0.0723 MW decrease per 1 mbara increase. These observational results indicate that absolute cooling-water supply temperature is more directly associated with turbine output than effectiveness alone. The findings should be interpreted as statistical associations rather than causal effects because steam flow, inlet steam conditions, plant load, humidity, fouling, and other operational factors were not simultaneously controlled in the simple regression models.