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Recently, considerable attention has been paid to the installation of renewable energy capacity to mitigate global CO2 emissions. H2 produced using water electrolysis and renewable energy is regarded as a clean energy carrier, generating electricity without CO2 emissions, called ‘Green H2’. In this paper, a prognostics and health management model for an alkaline water electrolyzer was proposed to predict the load voltage on the electrolyzer to obtain the state of health information. The prognostics and health management model was developed by training historical operating data via machine learning models, support vector machine and gaussian process regression, showing the root mean square error of 1.28 × 10−3 and 8.03 × 10−6. In addition, a techno-economic analysis was performed for a green H2 production system, composed of 1 MW of photovoltaic plant and 1 MW of alkaline water electrolyzer, to provide economic insights and feasibility of the system. A levelized cost of H2 of $ 6.89 kgH2−1 was calculated and the potential to reach the levelized cost of H2 from steam methane reforming with carbon capture and storage was shown by considering the learning rate of the photovoltaic module and electrolyzer. Finally, the replacement of the alkaline water electrolyzer at around 10 years was preferred to increase the net present value from the green H2 production system when capital expenditure and replacement cost are low enough.

Summary: For a sustainable hydrogen economy, large-scale transportation and storage of hydrogen becomes increasingly important. Typically, hydrogen is compressed or liquified, but both processes are energy intensive. Liquid organic hydrogen carriers (LOHCs) present a potential solution for mitigating these challenges while making use of the existing fossil fuel transportation infrastructure. Here, we present a process intensification strategy for improved LOHC dehydrogenation and an example of clean power generation using solid oxide fuel cells. Four LOHC candidates—ammonia, biphenyl-diphenylmethane eutectic mixture, N-phenylcarbazole, and N-ethylcarbazole—have been compared as stand-alone and integrated systems using comprehensive process simulation. “Temperature cascade” dehydrogenation was shown to increase the energy generated per unit mass (kWh/kg LOHC) by 1.3–2 times in an integrated system compared to stand-alone LOHC systems, thus providing a possibility for a positive impact on a LOHC-based hydrogen supply chain.

Economic evaluation for water electrolysis compared to steam methane reforming has been carried out in terms of unit hydrogen production cost analysis, sensitivity analysis, and profitability analysis to assess current status of water electrolysis in Korea. For a hydrogen production capacity of 30 Nm3 h−1, the unit hydrogen production cost was 17.99, 16.54, and 20.18 $ kg H2−1 for alkaline water electrolysis (AWE), PEM water electrolysis (PWE), and steam methane reforming (SMR), respectively with 11.24, 10.66, and 11.80 for 100 Nm3 h−1 and 8.12, 7.72, and 7.59 $ kg H2−1 for 300 Nm3 h−1. With sensitivity analysis (SA), the most influential factors on the unit hydrogen production cost depending on the hydrogen production capacity were determined. Lastly, profitability analysis (PA) presented a discounted payback period (DPBP), net present value (NPV), and present value ratio (PVR) for a different discount rate ranging from 2 to 14% and it was found that a discounted cash flow rate of return (DCFROR) was 14.01% from a cash flow diagram obtained for a hydrogen production capacity of 30 Nm3 h−1. [ABSTRACT FROM AUTHOR]