Synthetic ammonia will come from electric synthetic ammonia production plants. A few production-scale plants are already under construction, but of course hundreds more will be needed. Ammonia will not be, primarily, a storage medium, but a transportation medium and fuel, although it stores well under light pressure. Any tropical country can put up a solar farm and begin exporting ammonia to places less blessed with reliable sunshine -- for fertilizer, at first.

Insisting technologies that people are already spending billions of dollars on building out were not first shown to be viable is a peculiar position to take.