Annual Conference of Postgraduate Studies and Scientific Research (Basic and Engineering Studies Board) 17-20 February 2012, Friendship Hall, Khartoum 1 Effectiveness and Economic Feasibility of Gas Turbine Inlet-Air Cooling by Air Washing in the Hot and Dry Climate of Sudan M.M. El-Awad and H.A. Saeed Department of Mechanical Engineering, Faculty of Engineering, University of Khartoum Abstract: This paper studies the effectiveness and economic feasibility of cooling the gas-turbine's inlet-air by air washing (AW) compared to wetted-media evaporative cooling (WMEC) in the hot and dry climatic conditions of Sudan. Measurements were made on an experimental test rig to determine the cooling effect of the WMEV and that of AW with water at ambient temperature and with chilled water. Taken at two seasons of the year with different ambient temperature and humidity levels, the experimental results were used to estimate the revenues that the systems can generate as a result of increased megawatts and reduced heat rate of a typical gas turbine model (GE PG6581B). The calculations indicate that the WMEC system can increase the gas turbine output by 12% and reduce its heat rate by 1.6%. Using un-chilled water, the AW system can increase the output by 16.7% and reduce the heat rate by 2.2%, while with chilled water it can increase the power by 23.3% and reduce the heat rate by 3.1%. Based on these estimates, the WMEC system requires a payback period of 8 months if run for 4 hours daily, which reduces to 4 months if used for 8 hours. AW with un-chilled water has a payback period of about 8 months, but the pay-back period for the chilled-water AW system is about 5 years. Keywords: Gas turbine; Power augmentation; Inlet-air cooling; Hot and dry climate 1. INTRODUCTION It is well known that the generation capacity of a gas turbine diminishes with increased air temperature. High inlet-air temperature reduces the air density, leading to a reduction in the power generated from the turbine and a higher heat rate. According to Cracken [1], gas turbines produce 25-35% more power in winter than in summer and at 5-10% lower heat rate (kJ/kWh) which means less fuel consumption by an average of 6% saving in fuel. Since the ambient temperature in Sudan is high almost all the year round, gas turbines have lower power output and higher heat rate compared to their design values particularly in summer time when they are mostly needed. Due to high ambient temperature in summer (average of 42oC) the gas turbines lose 25% of their rated capacity at the standard design conditions. Moreover, the highest temperatures occur during the hot midday hours when the demand is high; thus causing frequent power interrupts and blackouts. Cooling the air entering the gas turbine's compressor is one of the most practiced power augmentation methods used to avoid loss of generation capacity. There are a number of proven inlet-air cooling technologies that include the wetted media-type evaporative systems, fog-cooling systems, mechanical refrigeration systems, and absorption refrigeration systems [2-7]. Johnson [2] presented a discussion of the theory and operation of evaporative coolers for industrial gas turbine installations. Chaker and Meher-Homji [3] presented a detailed climatic analysis of 106 major locations over the world to provide the hours of cooling that can be obtained by direct evaporative cooling. Their data helps gas turbine operators in assessing the economics of evaporative fogging. Hasnain et al [4] looked into the prospects of thermal storage systems in Saudi Arabia which has similar climatic conditions to Sudan's. They estimated that the use of ice storage systems with gas turbines for inlet air cooling would increase the turbine's output by 30% and reduce its heat rate by 10% at a mere fraction of the cost of installing additional capacity for power generation in order to meet the summer peak demand. Jaber et al [5] presented a theoretical study on the influence of intake air cooling on the gas turbine performance by evaporative cooling and refrigeration coil cooling. A computer simulation model was developed in order to evaluate the performance of the PG5341 gas turbine unit at Marka Power Station, Amman, Jordan. Their results