Optimal design and operation of integrated solar combined cycles under emissions intensity constraints

Highlights: • A framework for combined design and operations optimization of an ISCC is developed. • Physical and practical operational constraints are incorporated in the model. • Most ISCC designs are infeasible, but optimization reveals six viable configurations. • One configuration dominates all others with respect to NPV and CO₂ emissions. • Tradeoffs between emissions and NPV are optimized for different economic settings. Direct integration of solar thermal and natural gas systems can be achieved through integrated solar combined cycle (ISCC) power generation. In this work, optimal ISCC system design and hourly operations are determined simultaneously using computational optimization procedures. The full optimization problem is intractable, so a series of problem reductions are employed to explore the ISCC design space while ensuring that individual designs can operate feasibly for a wide range of operating conditions and under realistic constraints. We construct bi-objective Pareto fronts for two conflicting objectives: net present value (NPV) and average CO₂ emissions intensity of power produced. A variety of ISCC designs are explored to find a superior configuration with physically feasible annual solar contribution (ASC) of up to 20%, a significant improvement over published designs. We then explore the sensitivity of the results to economic factors such as discount rate, power price, and capital cost. By examining the Pareto frontiers of each case, we quantify the economic cost of reduced CO₂ emissions. The resulting ISCC-derived mitigation costs are found to be competitive with other CO₂ mitigation technologies.