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This study investigates the impact of including (or neglecting) the variable efficiency of hydrogen electrolyzers as a function of operating power in the modelling of green hydrogen produced from variable renewable energy sources. Results show that neglecting the variable electrolyzer efficiency, as is commonly done in studies of green hydrogen, leads to significant overestimation of hydrogen production in the range of 5–24%. The effects of the time resolution used in models are also investigated, as well as the impact of including the option for the electrolyzer to switch to stand-by mode instead of powering down and electrolyzer ramp rate constraints. Results indicate that these have a minor effect on overall hydrogen production, with the use of hour resolution data leading to overestimation in the range of 0.2–2%, relative to using 5-min data. This study used data from three solar farms and three wind in Australia, from which it is observed that wind farms produced 55% more hydrogen than the solar farms. The results in this study highlight the critical importance of including the variable efficiency of electrolyzers in the modelling of green hydrogen production. As this industry scales, continuing to neglect this effect would lead to the overestimation of hydrogen production by tens of megatonnes. • Variable efficiency electrolyzers are compared to fixed efficiency electrolyzers. • Fixed efficiency can lead to overestimation in hydrogen production by up to 24%. • Low fidelity time resolution has a modest impact on modelling hydrogen production. • Fixed efficiency electrolyzers underestimate the optimal size of hydrogen plant. • Results are validated using data from six renewable energy sites in Australia. [ABSTRACT FROM AUTHOR]

Hydrogen is considered a key energy vector and carrier for the decarbonization of global energy systems. However, the economics of green hydrogen systems hinder their widespread application. This paper presents a techno-economic analysis of a green hydrogen production system using high-temperature water electrolysis integrated with a concentrated solar power system (CSP-SOEC) for Western Australia. Real-time solar resource data with 30-min resolution for a typical meteorological year were used to assess the performance of the entire system. The intermittent nature of solar resources is accounted for by integrating the system with a thermal energy storage medium and performing the analysis in off-design mode. The validity of the electrolysis stack model is crucial for overall system performance, which was confirmed through experimental testing conducted on a 15-cell stack. The system was designed to generate a 1 MWe output, and the results showed that a field area of 29,000 m2 and thermal energy storage capacity of 382,500 kWh can fulfil the design criteria. The system generates 0.86 tonne/day of hydrogen at a cost of 8.87 US$/kg-H 2 with a solar-to-hydrogen efficiency of 13.80 %. The cost breakdown revealed that the storage medium has the most significant contribution. Moreover, the sensitivity of the system to the production capacity was analyzed, which showed that larger-scale hydrogen production systems have the potential to further reduce the cost. An 8 MWe system has the capacity to produce 7.18 tonne/day of hydrogen at a cost of 6.1 US$/kg-H 2. The molten salt is currently utilized only 39.3 % for the hydrogen production process. To optimize resource utilization, a cogeneration system is devised and assessed for simultaneous steam and hydrogen production. The results reveal that the cogeneration system can achieve an LCOH reduction of 9 % by reaching 8.07 US$/kg-H 2. These findings are invaluable for academic and industry stakeholders in making informed decisions and fostering the green hydrogen sector in Australia. • A techno economic assessment of green H 2 production for Australia is done. • The electrolysis model is corroborated using experimental results. • The cost of green H 2 for such system in Australia is 8.87 US$/kg-H 2. • Higher production capacity favors the system economics. • The cogeneration system reduces the cost by 9 %. [ABSTRACT FROM AUTHOR]

Large-scale hydrogen production will be required to provide sufficient hydrogen for planned applications. In Australia, and other countries, two main hydrogen productions methods have been proposed: hydrogen produced using renewables (green hydrogen) and hydrogen produced with fossil fuels and CCS (blue hydrogen). It is, to date, unclear how people think about the different attributes of these production methods and the extent to which the public's support for each approach influence downstream applications. Using an online survey instrument, this study explored how manipulating the hydrogen production method (green vs blue) influenced beliefs and public attitudes toward to production approach and various applications. The results revealed that beliefs differed depending on the production method presented but effect sizes were quite small overall. The effect was, however, more pronounced with those who more strongly endorse an environmental preservation attitude. The findings, overall, suggest that there is slightly stronger support for green hydrogen production, which is informed by the beliefs that blue hydrogen is a replaceable technology, will conflict with renewable electricity production and will have negative environmental impacts. The research emphasizes the importance of researchers and industry to show that blue hydrogen is a viable long-term option that will compliment, not conflict with, renewable electricity production. Additionally, the findings suggest that blue hydrogen projects will gain stronger support if they can demonstrate minimal local environmental impacts and limited carbon emissions. • Small differences in the perceived effects of blue vs green hydrogen production. • Acceptance of hydrogen applications are unaffected by the production method. • Blue hydrogen is seen as more replaceable and less environmentally friendly. • People who endorse environmental preservation are less accepting of blue hydrogen. • Industrial applications of hydrogen seen as more favourable than domestic uses. [ABSTRACT FROM AUTHOR]