Fraunhofer ISE says it has achieved a record 31.3% solar-to-hydrogen efficiency under outdoor operating conditions in Germany
Its HyCon hybrid module combines 4-junction solar cells with PEM electrolysis technology
The research highlights hydrogen’s role in storing intermittent renewable energy from solar and wind sources
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE have achieved a solar-to-hydrogen (STH) conversion efficiency of 31.3% under real outdoor conditions. The institute terms it a ‘record-breaking’ efficiency for renewable hydrogen production in real-world outdoor conditions.
The research team demonstrated the result in Freiburg, Germany, using a compact photovoltaic-electrolysis hybrid module called HyCon.
Fraunhofer ISE developed this module by combining high-voltage 4-junction (4J) III-V solar cells with 2 polymer electrolyte membrane (PEM) electrolysis cells that operate with deionized water to convert sunlight directly into hydrogen. They used concentrator PV solar cells in the work, combining 2 dual-junction semiconductor structures. The 4J solar cell technology has achieved record solar-to-electricity (STE) conversion efficiencies of up to 47.6% under concentrated sunlight conditions.
For the outdoor demonstrator, the team used concentrated sunlight through a Fresnel lens array to power water splitting and generate hydrogen. The efficiency was measured using the higher heating value (HHV) of hydrogen, which accounts for the total energy stored in the fuel.
The CPV/PEM electrolysis prototype module was tested outdoors on a dual-axis solar tracker over 13 summer days in Freiburg. It demonstrated that hydrogen can be generated with an STH conversion efficiency of up to 31.3%.
Researchers said hydrogen can serve as a flexible energy carrier for electricity generation, industrial processes, and heat and gas markets. Most existing STH approaches have lower efficiencies, whereas the HyCon system demonstrated that highly efficient, compact solar-hydrogen technologies are feasible under practical operating conditions.
The German research institute explains that the study highlighted hydrogen’s potential role in balancing intermittent renewable energy sources such as solar and wind, even though it is currently a more expensive option than producing gray hydrogen from natural gas.
Yet the team is hopeful that green hydrogen will become cost-competitive in regions with strong solar resources by 2030, citing the International Energy Agency’s estimates that renewable hydrogen costs between $1.6/kg and $4.0/kg globally.
“To reach these scenarios, it is crucial to increase the solar-to-H2 (STH) conversion efficiency well beyond 15% in addition to reducing the system CAPEX and increasing operating hours. Systems using sunlight concentration in combination with highest performance photoabsorbers and electrocatalysts facilitate these targets,” adds Fraunhofer ISE.
The complete paper titled Photovoltaic water electrolysis reaching 31.3% solar-to-H2 conversion efficiency under outdoor operating conditions is available in the communications engineering journal.