Review on integrated green hydrogen polygeneration system——Electrolysers, modelling, 4 E analysis and optimization

Green hydrogen production by water electrolysis is sustainable and carbon-free for energy storage. This paper introduces recent development in integrated green hydrogen polygeneration. Throughout this review, theoretical concepts, design types, and recent developments related to the integration of Alkaline Electrolysis (AE), Proton Exchange Membrane Electrolysis (PEME), and the Solid Oxide Electrolysis Cell (SOEC) are summarised. This review evaluates the thermodynamic efficiency and economic impact of green hydrogen production integrated with different energy sources, energy storage and power cycles. Compared with two kinds of commercially applied methods (AE and PEME), SOEC is the state-of-the-art method to produce hydrogen, which can be integrated with external heat to reduce energy consumption. SOEC avoids the inevitable energy loss in AE and PEME, which leads to low-temperature waste heat evaluated as exergy destruction rather than utilized. The overall efficiency improvement of SOEC systems is over 10%. In most cases, the efficiency is always over 70%, and over 80% in some cases, which exceeds the typical values of 20%–60% from AE and PEME systems. The produced hydrogen can be stored and transported, as well as being used as a feedstock for chemical production, forming a polygeneration system with multiple energy sources, desalination, and fuel production. The latest lifetime of SOEC was predicted at 50,000 h or more, which is the minimum requirement to be commercially competitive. In the literature review, 80.4% of papers chose exergy efficiency as assessment index, compared with 67.9% of energy efficiency. And 58.9% of them chose genetic algorithm to complete multi-objective optimization.