The South Australian Green Hydrogen study supports your considerations:
"Scale of industry / future renewable uptake The proceeding sections have demonstrated that under certain conditions there may be a commercial opportunity for Green Hydrogen in South Australia and that the prospect may improve if the full value proposition can be realised. It is worth considering in very coarse terms what the size of the opportunity might be. What might the Green Hydrogen market look like in the future? This requires consideration of not just production cost but policy, social and political drivers. It is these factors which largely set any green premiums available to Green Hydrogen and ultimately market size. This is difficult to predict, so a real opportunity can be used to illustrate by example. In 2016, South Korea’s finance minister was reported13 to announce plans to replace the country’s 26,000 CNG powered buses with hydrogen-powered buses, representing around 475,000 tonnes of hydrogen consumption per year. This is to be undertaken progressively, replacing around 2000 buses per year. If this final consumption was to be fuelled by Green Hydrogen, a prospect that many Governments are likely to consider, what would the “Green Hydrogen” industry production be to meet this demand? Assuming that hydrogen is produced in South Australia from renewable energy, a hydrogen carrier, such as ammonia, is used to transport the fuel to South Korea, and based on metrics for the 2027 full scale ammonia plant involving around 28,000 tonnes of H2 per year per plant, 17 full scale 600t per day ammonia production facilities are required to meet this demand. This would be an investment of approximately $15bn in the plant alone, representing approximately 700 full time jobs. This level Green Hydrogen production would require approximately 28TWh per year in electricity input, which is more than twice the current South Australian yearly consumption. To meet this demand for renewable energy would require the installation of around 11GW of solar photovoltaic generation, or likely more than $15B in generation investment. To put the size of the construction required into perspective, AEMO estimated that there was 679MW of rooftop solar PV installed in South Australia in 2015-16 and 1,576MW of wind generation15. To consider just what size the Green Hydrogen market could grow to, considering more than 60 million tonnes per year of hydrogen are currently consumed by industry, a factor of more than 100 times the South Korean example cited above. The Green Hydrogen opportunity size could be a very significant export industry for South Australia." https://virtualpowerplant.sa.gov.au...8761688/green-h2-study-report-8-sept-2017.pdf
