Hydrogen energy occupies an important position among non-fossil energy sources. Among various hydrogen production methods, high-temperature electrolysis has high hydrogen production efficiency, and combined with solar energy, it can achieve clean hydrogen production, which is expected to become the main hydrogen production method. Internationally, the coupling method of solar energy and high-temperature electrolysis is indirect coupling, that is, using solar energy to generate high-temperature steam, and then passing the high-temperature steam into a solid oxide electrolysis cell to undergo electrochemical reactions to produce hydrogen. However, this method has problems such as low equipment integration and large heat transfer losses. Recently, Li Xin's research team from the Institute of Electrical Engineering, Chinese Academy of Sciences, proposed a direct coupling solar high-temperature electrolysis hydrogen production technology and developed a prototype.
The team innovatively proposed the concept and design scheme of direct-coupled solar high-temperature electrolysis. By studying the transmission characteristics of high-intensity, non-uniform incident radiation inside porous electrodes and the coupling mechanism of microscale flow and porous structure radiation heat transfer under concentrated solar conditions, the team developed a prototype of direct-coupled solar high-temperature electrolysis, revealing the mechanism of the influence of concentrated solar energy on concentration polarization in the electrolytic cell. Compared with electrically heated solid oxide electrolytic cells of the same size, this technology improves the start-up speed of the solid oxide electrolytic cell by nearly 12 times and reduces the electrolysis energy consumption by 76%.
Meanwhile, the team developed a novel solar high-temperature atomizing steam generator under indirect coupling mode. Leveraging the heat and mass transfer enhancement mechanism of atomized gas-liquid two-phase flow within a porous heat absorber, the research elevated the outlet temperature of the steam generator to 877°C, correspondingly increasing the thermal efficiency by 60.92%. Based on this solar steam generator, the team further constructed a 5kW-scale solar high-temperature electrolytic hydrogen production system. This system achieved an actual measured electrolysis efficiency of 95.2% and a steam conversion rate of 92%. Compared to traditional electrolysis systems that use electricity or fossil fuels to generate steam, the solar high-temperature electrolytic hydrogen production system can save 30% of electricity.
The relevant research results have been published in the Chemical Engineering Journal and Energy Conversion and Management. The research work has been supported by the National Natural Science Foundation of China and the Beijing Natural Science Foundation, among others.
Paper links: 1, 2
Direct solar high-temperature electrolysis principle prototype
