Gas turbine performance at varying ambient temperature

The difference between the actual power generated by a gas turbine and the design rated power tagged on the gas turbine is observed whenever a gas turbine operates at site ambient conditions that vary from the stipulated ISO conditions. A detailed study and extensive logging of data has endorsed the well known existence of a direct relationship between the ambient temperature and the de-rating of gas turbine power output. The paper proposes an empirical relationship between the gas turbine’s ability to generate power when exposed to site ambient conditions, such as the ambient temperature, which differ from ISO conditions. For every K rise in ambient temperature above ISO conditions the Gas Turbine loses 0.1% in terms of thermal efficiency and 1.47 MW of its Gross (useful) Power Output. This established relationship will assist the proper assessment of local power generation for installation planning and forecasting with special reference to Middle-eastern countries which are rapidly developing the application of Gas Turbine Inlet Air Cooling (GTIAC) technologies. This study was conducted for specific turbines SGT 94.2 and SGT 94.3 installed at the DEWA Power Station located at Al Aweer, H Phase II and III in Dubai, UAE.