Hybrid systems for solar hydrogen: A selection of case-studies

Twelve case-studies on systems that generate, store and use hydrogen from photovoltaic energy are hereby presented and discussed. Hydrogen generated from direct sunlight is often called solar hydrogen, and the whole process is characterized by having very low CO2 and pollutants emissions. Such systems, comprising of several sub-systems of different technologies, are called hybrid systems. All case-studies are briefly analyzed and the most prominent conclusions reported. Results show that production of solar hydrogen and its subsequent use in fuel cells is technically viable but costs still need to be reduced for widespread adoption. A comparison is given and need for further work highlighted; in particular, researchers should investigate carbon structures as a potential alternative to pressurization or metal hydrides; a complete analysis of the intangible costs and benefits involved should be performed, together with Discounted Cash Flow and Life Cycle Assessment analysis to understand the true nature of such investments and their sustainability in the near future. Performing such a rigorous and complete economical analysis would, for instance, enable governments to design better incentive schemes and propel such technology in real life usage.