Fundamental Experiment and Analysis of Direct Energy Conversion Using Proton-Conducting Ceramic Fuel Cells Supplied with High-Temperature Nuclear Heat and Natural Gas

Abstract

A system to utilize high-temperature nuclear heat effectively is proposed here. The system comprises a High-Temperature Gas-cooled nuclear Reactor (HTGR), reaction vessels to produce H₂ using the steam-reforming reaction of CH₄ or the Iodine-Sulfur (I-S) process, chemical heat pumps and He gas turbines. The chemical heat pumps are operated between the two decomposition temperatures of SO₃ (~900°C) and HI (~500°C) of the I-S process. The pump system transfers heat from lower temperature to higher one with repeated H₂ absorption-desorption cycles, and the overall thermal conversion ratio from H₂O to H₂ can be enhanced. The material candidate for H₂ absorption in heat pump is considered TiH₂ and ZrCoH₃ (or UH₃) according to the two reaction temperatures. The decomposition of the metal hydrides proceeds at their respective plateau pressures that are a function of temperature regardless of the H content in metals. Variations of the temperature and the equilibrium H₂ pressure with repetitions of the heat-pump cycle are shown in the present paper comparatively. In addition, proton-conducting fuel cell system supplied with CH₄ is incorporated in the high-temperature utilization system.