Thermo-economic assessment and retrofitting of an existing electrical power plant with solar energy under different operational modes and part load conditions

This paper investigates operational modification of 250 MW Rajaee natural gas fired electrical power plant by supplying a portion of the required heat load from the solar energy source. The base case and the introduced hybrid system, both are simulated in Thermoflow and MATLAB softwares. Simulation of parabolic collector solar field in both methods of power boosting and fuel saving is performed by MATLAB. An economic analysis is done and optimal solar contribution is calculated. The obtained results specify that in solar aided electrical power generation mode can reach higher thermal efficiency in comparison with the using natural gas as fuel. In this case, with utilizing the solar field (120,000 m2) the thermal efficiency extends from 37.0% to 39.1%. The electrical power generation by employing 7.00% of solar heat energy, up to 24.0 MW can be improved. In the fuel saving mode, the gross annual cutbacks of the fuel consumption and CO2 emissions rates for a 12×104 m2 solar collector receiver are 35,125×103 kg and 11,164×103 kg; respectively. The electrical power generation costs and fuel consumption rate saving are 80.0 US$/kWh. Also, period of return for the electrical power generation mode is six years.