Off-Design Performance and Annual Solar Contribution Assessment of a 100 MW Hybrid Solar Tower–Gas Turbine System under Libyan Desert Conditions

This work examines the off-design and long-term operational performance of a 100 MW hybrid solar tower–based gas turbine system under desert climatic conditions in Libya. The solar field and receiver performance are modeled with the System Advisor Model (SAM), while a steady state Brayton cycle thermodynamic model is used to calculate the hourly hybrid operation and fuel requirements. At the design point, the power block produces a net electric power of approximately 109 MW with a net electrical efficiency of about 39%, thus confirming the physical consistency of the adopted thermodynamic formulation. On an annual basis, the solar receiver provides 524,602 MWh of useful heat, which is equivalent to a solar fraction of the total annual heat demand of 21.43%. The hybrid design leads to a decrease in natural gas consumption from 236.57 million m³ in the baseline case to 185.88 million m³, i.e., an annual saving in fuel of about 50.69 million m³. Using standard conversion and emission factors, the value of avoided emissions in CO₂ equivalent is about 108 thousand tons per year. An economic assessment based on the Levelized Cost of Electricity (LCOE) further indicates that the proposed hybrid configuration reduces the estimated LCOE by approximately 4.3% compared with a conventional gas turbine operating under identical conditions. The results of this paper indicate that the coupling of solar energy with gas turbine cycles by hybridization can deliver a considerable improvement in the thermodynamic performance as well as decrease fossil fuel consumption and greenhouse gas emissions, even without the use of thermal energy storage, under high DNI desert conditions.