“…In variants 1, 3, and 5, only low-mineralized water pumped from the goaf is to be treated, while in variants 2, 4, and 6, rainwater captured from photovoltaic panels is also to be treated. The designed variants have a similar surplus of generated electricity, so the amount of hydrogen generated by the variants is similar [36,51,52]. Variants 2, 4, and 6 achieved an annual production of 222 Mg of hydrogen, and variants 1, 3, and 5 an annual production equal to 224 Mg of hydrogen.…”