solartohydrogen

Solar-to-hydrogen (STH) refers to converting solar energy into chemical energy stored in hydrogen, typically by splitting water into hydrogen and oxygen. The aim is to provide a carbon-free energy carrier that can be produced when sun is available and used later for electricity generation, transportation, or industrial processes.

Most practical STH systems rely on solar electricity generated by photovoltaic cells that powers an electrolyzer to split water. This PV-plus-electrolysis approach is closest to commercial deployment and modular in design. A complementary approach seeks to drive water splitting directly with sunlight using photoelectrochemical cells or photocatalytic systems, which bypass the separate electricity generation step but face greater material and durability challenges.

Efficiency in STH is described as solar-to-hydrogen efficiency, the fraction of incident solar energy stored in hydrogen. PV-powered electrolysis systems typically achieve overall efficiencies in the range of about 15–25% under standard conditions, depending on technology and operation. Direct solar-to-hydrogen devices demonstrated in laboratories have shown a broader range of results, often lower due to stability and scaling issues, though some milestones exceed 20% in specialized setups.

Hydrogen produced by STH can be stored as compressed gas, liquefied hydrogen, or in solid-state storage materials and later used in fuel cells, turbines, or as industrial feedstock. This makes STH attractive for long-term energy storage and for sectors that are difficult to electrify.

Barriers include high capital costs for electrolyzers, durability under operating conditions, water resource considerations, hydrogen handling safety, and the need for integrated storage and distribution infrastructure. Advances in materials, system design, and policy support influence the pace of commercialization and deployment.