Energy and exergy analysis of hydrogen production combined with electric energy generation in a nuclear cogeneration cycle

The cogeneration nuclear energy cycle with a power-to-gas solution was investigated. The aim of combining hydrogen production with electric energy generation is to increase operational flexibility and profitability of high temperature nuclear reactors, which are the safest of all nuclear technologies. The main motivation for this research is to take advantage of the developing world hydrogen market. Hydrogen production can be based on renewable energy sources. However, renewable and thermal power plants are connected in the power grid, and therefore, it is more profitable to use a thermal power plant to produce hydrogen via thermo-electrical processes while renewable energy sources cover the power grid demands. However, this novel approach to energy balance in the power grid requires high operational flexibility of hydrogen-electric cogeneration plants to ensure power reserves for wind and solar power plants. Using simulations and analyses, the possibility and profits of using the combination of hydrogen production and electric energy generation were confirmed. The nominal electric net power of the cogeneration plant, with no hydrogen production, equals 303.54 MW with energy efficiency equal to 50.59%. For a full load of hydrogen production with a full load nuclear reactor, the hydrogen amounts to 4392 kg/h, which according to the higher heating value gives 173.00 MW. The electric energy consumption for that process is 121.94 MW and electric net power of the cogeneration plant decreases to 161.99 MW, which is 26% of the nominal electric power. The energy efficiency of the cogeneration plant with the nominal hydrogen production equals to 55.83%.