SunHydrogen says its hydrogen-producing modules have exceeded 10% solar-to-hydrogen efficiency in testing with Australian company Sparc Hydrogen, giving the technology a new path toward pilot-scale demonstrations.
The companies have now signed a 24-month technology collaboration agreement that will test whether SunHydrogen’s modules can be integrated into Sparc Hydrogen’s concentrated-sunlight reactors. The next stages will progressively increase the intensity of sunlight reaching the modules before the system is tested outdoors at Sparc Hydrogen’s SHARP pilot facility in Roseworthy, South Australia.
The important number here is solar-to-hydrogen (STH) efficiency. It measures the fraction of incoming solar energy that ultimately becomes chemical energy stored in hydrogen. In other words, a 10% STH system turns the equivalent of 10% of the sunlight hitting it into hydrogen energy.
That is a meaningful research milestone, but it is not a world record. The U.S. National Renewable Energy Laboratory (NREL) reported a 16.2% STH efficiency for a photoelectrochemical system in 2017, while NREL has also cautioned that solar-hydrogen measurements can vary substantially between laboratories without rigorous standardized testing.
How the technology produces hydrogen
Conventional green-hydrogen systems generally use electricity from renewable sources to power an electrolyzer, which splits water into hydrogen and oxygen. SunHydrogen is developing a different approach.
Its modules use sunlight directly to drive hydrogen production, through a combination of photoelectrochemical and integrated photovoltaic-electrolysis components. Instead of first generating electricity in a separate solar farm and then sending it to an electrolyzer, the device is designed to integrate solar energy conversion and the water-splitting process.
Sparc Hydrogen uses another direct solar route: photocatalytic water splitting. Its reactors concentrate sunlight onto photocatalyst materials that drive the chemical reaction producing hydrogen. The company was founded around research led by University of Adelaide chemist Professor Greg Metha, whose group demonstrated concentrated-sunlight hydrogen production in 2021.
The attraction of combining the technologies is straightforward: if SunHydrogen’s modules can operate efficiently under concentrated sunlight, they could potentially benefit from the same high solar flux that Sparc’s reactor architecture is designed to exploit.
Testing has already provided one encouraging result. According to SunHydrogen, its modules generated more hydrogen as the sunlight was concentrated, suggesting that increasing solar intensity can increase production rather than simply pushing the system outside its useful operating range.
The real test comes next
The companies will now increase the concentration level during laboratory testing before potentially moving to outdoor operation at SHARP. Results from that work will feed into a jointly funded techno-economic assessment, examining the levelized cost of producing a kilogram of hydrogen. That economic question may ultimately matter more than the 10% efficiency figure.
High efficiency can reduce the amount of equipment and land required for a given amount of hydrogen, but commercial systems also have to contend with material costs, catalysts, optical systems, heat management, maintenance and, crucially, durability.
Durability is a particularly important challenge for direct photoelectrochemical hydrogen systems. NREL has noted that semiconductor materials can degrade when exposed to aqueous electrolytes, making long operating lifetimes difficult to achieve even when laboratory efficiency is high. SunHydrogen and Sparc Hydrogen therefore still have to demonstrate that the efficiency observed in testing can survive the transition from controlled laboratory conditions to a larger system operating under concentrated sunlight.
If the collaboration reaches its milestones, Sparc Hydrogen will have an 18-month option to negotiate either a long-term supply agreement or manufacturing license for SunHydrogen’s modules.
