Design, modeling and multi-objective techno-economic optimization of an integrated supercritical Brayton cycle with solar power tower for efficient hydrogen production

Solar-driven hydrogen production systems are environmentally benign alternatives to gain more benefits of green hydrogen. In this work, a novel power generation plant based on supercritical Closed Brayton Cycle (CBC) driven by solar heliostat field is designed and optimized to be integrated with an electrolyzer for green hydrogen production. To improve the CBC performance, its waste heat is recovered by an organic Rankine cycle (for additional power generation) and an absorption chiller for compressor inlet cooling. Thermoeconomic models are developed to evaluate the proposed hydrogen production plants and to compare the proposed combined cycle performance with that of standalone CBC-based system, in terms of hydrogen production rate, solar-to-hydrogen exergy efficiency and levelized cost of produced hydrogen. Then, a bi-objective optimization is conducted to attain minimum hydrogen cost and maximum exergy efficiency. The results revealed superior performance of the combined cycle over the CBC-based system. Under the optimum operating condition, the combined cycle yields around 15.8% higher hydrogen production rate and solar-to-hydrogen efficiency, and approximately 4.2% lower hydrogen cost. This implies that, the additional expenditures imposed by adding the bottoming cycles are totally compensated by extra hydrogen production, which in this case it costs 7.01$/kgH2. A comparison with a solar tower-based previous system proved superiority of the present plant by around 5% based on solar-to-hydrogen exergy efficiency.