Molten carbonates for advanced and sustainable energy applications: Part II. Review of recent literature

Abstract

Unprecedented interest for clean and sustainable energy innovation has recently stimulated a return of attention on molten alkali carbonate salts not only for traditional use as electrolyte and high temperature reaction media but also as innovative energetic material for advanced applications in hybrid fuel cell systems and high-temperature CO2 gas separation processes. The main focus of this literature review is on examining novel and emerging molten carbonate applications in energy sectors beyond the well-assessed and mature domain of the Molten Carbonate Fuel Cells. In general, a number of advanced processes and highly functional materials are currently under investigation involving molten carbonates in a key role, suggesting a high potential of these salt systems for the future development of sustainable energy technologies. Current research activities can be grouped into three main energy research areas related to generation/conversion/storage of energy, materials and manufacturing processes, hot gas processing and gasification technologies. As already analyzed in Part I of this work, notable features of molten carbonates include their chemical stability, safety and optimal performance under a wide range of moderate (500–600 °C) and moderate-to-high temperature (600–800 °C) conditions. Thanks to these peculiar aspects, molten carbonate processes can be ideally integrated with solar energy sources for maximum sustainable level of use and with broad development prospects in the storage of solar energy and solar-to-chemical conversion systems. This view is confirmed, for example, by a series of extensive studies that has recently investigated novel solar-to-chemical energy conversion strategies based on a molten carbonate electrolysis process for solar production of fuels and other important chemical products, including iron and cement. In the last part of this work, several directions and opportunities for future research and studies on molten carbonates are suggested.