Thermodynamic analysis of two very-high-temperature gas-cooled reactor-driven hydrogen and electricity cogeneration systems under off-design operating conditions

Abstract

This study conducts a thermodynamic analysis for two very-high-temperature gas-cooled reactor-driven hydrogen and electricity cogeneration systems integrating an iodine-sulfur cycle and a helium turbine direct cycle under off-design operating conditions. Control strategies are proposed based on inventory control. The calculation model is established for the main components of the system under off-design conditions. Two operation modes are proposed, one is to maintain the split ratio at the reactor outlet at the rated value, and the other is to maintain the hydrogen generation rate at the rated value. The off-design performance of the two systems under partial load in two modes is analyzed. For Systems 1 and 2, the suggested lower limits of reactor thermal power are 68.80 % and 69.00 % of the rated value in mode 1, and 72.04 % and 64.98 % in mode 2. As the reactor thermal power decreases from the rated value to the suggested lower limit, in modes 1 and 2, the hydrogen-electricity efficiency of System 1 decreases from 37.46 % to 36.20 % and 31.81 %, and that of System 2 decreases from 42.40 % to 41.45 % and 35.21 %. The decrease in overall efficiency is more significant in mode 2.