Boosting Gas Turbine Combined Cycles in Hot Regions Using Inlet Air Cooling including Solar Energy

Abstract

Cooling the air before entering the compressor of a gas turbine of a combined cycle power plant is an effective method to boost the output power of both the gas and the steam turbines in hot regions. Usually, in hot area, the time at which the demand of power is highest coincides with the time of the largest drop of power generation due to the weather conditions, which shows the importance of air inlet cooling. However, fortunately, the daily peak period of electrical power demand coincides with the peak of solar radiation that is abundant in Saudi Arabia. This paper presents a novel system of cooling the gas turbine inlet air using a solar assisted absorption chiller. The study includes also a comparative analysis of a gas turbine combined cycle power plant performance when it is integrated with conventional and solar-assisted absorption chillers for inlet air cooling with the performance of the plant operating without inlet air cooling. The effect of ambient air temperature on the output power is investigated and reported. The advantage of air inlet cooling in boosting the power of the combined cycle in Dhahran is evident especially in summer. The study revealed that at the design hour under the weather conditions of Dhahran, KSA (July 17^th at 1 p.m.), the net power output of the plant drops from 267878 kW to 226361 kW at 48 °C (15.5% drop). While the gross power output of the gas turbine drops from 189472 kW to 151469 KW (20.1% drop) and the steam turbine from 84798 KW to 80495 KW (5.1% drop). Integrating conventional and solar-assisted absorption chillers increased the net power output of the combined cycle by 34964 KW and 37999 KW, respectively. Average and hourly performance during typical days have been conducted and presented. The plants without air inlet cooling system show higher carbon emissions (0.73 kg CO₂/KWh) compared to the plant integrated with conventional and solar-assisted absorption chillers (0.509 kg CO₂/KWh) and (0.508 kg CO₂/KWh), respectively. Also, integrating a conventional absorption chiller shows the lowest levelized electricity cost.