DEVELOPMENT OF INTEGRATED MEASURES FOR PERFORMANCE ANALYSIS OF A GAS TURBINE POWER PLANT

Abstract

Performance analysis of gas turbine power plant is imperative for its optimal operations and maintenance. Reliability, exergy efficiency and emission characteristics are measures that have been used independently to assess its performance. However, this independent assessment approach has not adequately expressed the actual state of the plant performance. While other approaches are being explored, literature on Integrated Assessment Approach (IAA) is sparse. This study therefore focused on development of performance measures of IAA for the evaluation of gas turbine power plants. Four-year (year-1, year-2, year-3 and year-4) available data of a 180 MW simple cycle gas turbine power plant (Model No.:GT13E2) operating on dry low NOx technology was obtained to determine the plant performance state. Performance parameters of exergy destruction and exergy efficiency (at base loads of 80, 120 and 140 MW), reliability and availability were analysed, yearly. Steady state exergy analysis equation was used to evaluate the plant exergy destruction and exergy efficiency. System adequacy technique was used to evaluate the plant reliability and availability. Two new performance indexes (I and II) based on the IAA were developed and compared with the independent measures in the assessment of the power plant. Exergy efficiency and reliability were combined to formulate Index I, while exergy efficiency and availability were combined to formulate Index II. The indexes ranges between zero and one indicating the minimum and maximum points. Data were analysed using ANOVA at α0.05. Plant exergy destruction at 80, 120 and 140 MW base loads were 0.6640, 0.6290 and 0.5914; 0.6476, 0.6342 and 0.5855; 0.6295, 0.6342 and 0.5926; and 0.6523, 0.6285 and 0.6043 in year-1, year-2, year-3 and year-4, respectively. Exergy efficiencies at 80, 120 and 140 MW were 0.7195, 0.7916 and 0.8691; 0.7510, 0.7854 and 0.8775; 0.7808, 0.7774 and 0.8602; and 0.7389, 0.7875 and 0.8445 in year-1, year-2, year-3 and year-4, respectively, indicating improvement as base load increased. Reliability and availability were 0.8820 and 0.8168; 0.7959 and 0.6734; 0.7604 and 0.7497; and 0.6294 and 0.7238 for year-1, year-2, year-3 and year-4, respectively. At 80, 120 and 140 MW base loads, Index I values were 0.8281, 0.8630 and 0.9289; 0.7919, 0.8098 and 0.9023; 0.7833, 0.7819 and 0.8822; and 0.6538, 0.6860 and 0.8197 in year-1, year-2, year-3 and year-4, 7 respectively. At 80, 120 and 140 MW, Index II values were 0.5877, 0.6466 and 0.7099; 0.5058, 0.5289 and 0.5909; 0.5854, 0.5828 and 0.6449; and 0.5345, 0.5700 and 0.6113 in year-1, year-2, year-3 and year-4, respectively. Index I exhibited higher sensitivity by mimicking the combined behaviour of reliability and exergy efficiency. The best plant state was achieved in year-1 at 140 MW base load. Index II also indicated that the plant performed better in year-1 at 140 MW base load compared to other years. The integrated measures had similar trend with the independent measures but were significantly different. The integrated assessment measures were found suitable in the assessment of gas turbine power plant as they gave a better expression of the actual plant performance state.