Solar hydrogen’s role for a sustainable future

In this study, hydrogen’s role during the transition to 100% renewable energy systems is discussed thoroughly, and the importance of sustainable hydrogen production is highlighted. For a successful transition to hydrogen-based renewable energy systems, hydrogen has to be produced in a clean, reliable, affordable, efficient, and safe manner. Therefore, in the second part of this study, a comprehensive life cycle assessment of solar hydrogen production options is conducted. The selected clean hydrogen production options are steam methane reforming, conventional electrolysis, photoelectrochemical cells, PV electrolysis, and photocatalysis. A complete source to service approach is taken when evaluating the environmental and technical performance of the selected hydrogen production options. Greenhouse gas (GHG) emissions, resource use, fossil fuel use, water use, energy and exergy efficiencies, and cost of hydrogen are the selected sustainability performance criteria. The selected hydrogen production methods are compared based on these performance criteria. In the next part, the performance evaluation results of each option are normalized and ranked in the 0–10 range where 0 gives the least sustainable manner, and 10 is the hypothetical ideal case where there is no damage to the environment, zero resource and water use, and 100% energy and exergy efficiencies, and zero cost. The GHG emissions, resource use, fossil fuel use, and water use results indicate that photoelectrochemical cells (PEC) is the most advantageous. Steam methane reforming has the highest efficiencies and the lowest. When all of the selected performance criteria are considered together, PEC has the highest sustainability rankings (5.24/10), and steam methane reforming has the lowest (3.24/10).