Simulation of a GEF5 Gas Turbine Power Plant Using Fog Advanced Cycle and a Systematic Approach to Calculate Critical Relative Humidity

The ambient conditions have a significant effect on the generated power and efficiency of gas turbines [1]. These variations considerably affect power generation, fuel consumption, power plant emissions, and plant incomes. However, cooling the compressor inlet air has been widely used to reduce this deficiency [2]. In this paper, by simulating a specific gas unit in Thermoflow software, the effect of the FOG system on it was studied. Considering the error in determining the capacity of cooling systems based on the average values of dry and wet bulb temperatures, or even considering the worst possible temperature and humidity conditions, it is advisable to use ECDH or Evaporation cooling Degree Hours. Accordingly, by calculating ECDH under at ambient temperatures above 15 °C and changing the conditions of the model, the total production increase of the unit was estimated to be 4.7×106 kWh. In addition, the effect of relative humidity on payback time was examined, which illustrated the critical relative humidity for a gas unit would depend on the price of fuel, the purchase price of electricity, the design parameters of the unit and the expected payback time. For this gas unit, critical relative humidity was monitored based on expected payback time and electricity purchase price. Results showed that for a certain electricity price, at the shorter PBT, the critical RH is lower; therefore, the temperature drop and power enhancement will be greater. In addition, at a certain PBT, as the electricity price increases, the critical RH for the same PBT will be higher.