Design and optimization of hydrogen production by solid oxide electrolyzer with marine engine waste heat recovery and ORC cycle

Highlights: • A hydrogen production by solid oxide electrolysis (SOEC) is performed. • Marine diesel engine is integrated for load variation and waste heat recovery. • Organic Rankine Cycle (ORC) is used for power generation. • The SOEC system design and operating parameters are optimized. Hydrogen is considered as a promising alternative to future energy systems. Water or steam electrolysis at elevated temperature consumes less electricity due to the highly efficient utilization of thermal energy. In this paper, a solid oxide electrolyzer cell (SOEC) is integrated with a marine diesel engine to use both electricity and waste heat for hydrogen production. An Organic Rankine Cycle (ORC) is applied to produce electricity from SOEC production streams. A comprehensive thermodynamic analysis model of SOEC, ORC and marine diesel engine waste heat recovery is conducted. The results indicated that the system could produce hydrogen at a rate of 0.431 kg/s and power output of 32386.45 kW with a power reduction of 60%. An efficiency of 104.41%, 12.12% and 53.56% could be achieved for the electrolyzer cell, ORC and integration system, respectively. The waste heat available efficiency could reach only 44.13% under the design conditions. To study the impact of some key parameters on the system performance, sensitivity analysis of current density, H₂O inlet flow rate and total SOEC area were performed. It was found that an optimal current density and H₂O flow rate can be obtained. Moreover, higher total cell area benefits the integration system thermodynamically.