Australia used concentrated sunlight to split water directly into hydrogen without an electrolyzer; SunHydrogen’s coaster-sized module hit 10.8%, while its 1,200-cm² version reached 9%

A solar panel that makes hydrogen sounds simple until engineers try making it bigger. SunHydrogen has now crossed 10% solar-to-hydrogen efficiency in new Australian testing. That sounds like a clear step forward for direct solar hydrogen technology. But the company has faced a revealing problem before, when larger modules produced lower efficiency.

The latest result came from preliminary testing with Sparc Hydrogen in Australia. SunHydrogen said its modules exceeded 10% efficiency while producing more hydrogen under concentrated sunlight. The companies are now preparing for additional laboratory work and potential pilot-scale testing in South Australia.

That makes the announcement interesting for a reason beyond the percentage itself. SunHydrogen previously reported 10.8% efficiency from a much smaller 100-square-centimeter module. A later 1,200-square-centimeter module reached 9%, showing how difficult it can be to preserve performance during scale-up.

Why is 10% solar-to-hydrogen efficiency such a big number?

Solar-to-hydrogen efficiency measures how much sunlight becomes chemical energy stored in hydrogen. In simple terms, the device captures sunlight and uses that energy to split water. The hydrogen then stores part of that captured energy in chemical form.

Crossing 10% is considered an important benchmark for technologies that make hydrogen directly from sunlight. It does not mean the system is commercially ready, though. Efficiency must be combined with durability, manufacturing costs, hydrogen output and reliable outdoor performance. Those factors ultimately determine whether the technology can compete with other clean-hydrogen systems.

SunHydrogen has already seen efficiency fall with size

The company’s earlier results provide useful context for the new announcement. In 2024, SunHydrogen said its 100-square-centimeter modules reached 10.8% solar-to-hydrogen efficiency at Honda R&D in Japan. Those modules were developed with German manufacturer CTF Solar.

SunHydrogen later tested a 1,200-square-centimeter module using a large-area solar simulator. That module reached 9% active-area efficiency across temperatures from 5°C to 40°C. The company described the result as a leading efficiency for a module of that size.

The difference is worth noticing because the larger module did not simply preserve the smaller device’s performance. Engineers had to deal with the challenges that appear when active areas expand. SunHydrogen said improvements to water-splitting area and catalyst loading could help larger modules move beyond that level.

What changed in the new Australian testing?

The new work brings SunHydrogen’s modules into Sparc Hydrogen’s concentrated-sunlight approach. Sparc Hydrogen is a joint venture involving Sparc Technologies, Fortescue and the University of Adelaide. Its work focuses on producing hydrogen through photocatalytic water splitting under concentrated sunlight.

SunHydrogen said its modules produced more hydrogen as the sunlight became more concentrated. That is important because the Australian team is developing reactors designed around concentrated solar energy. The companies now plan laboratory testing at increasing levels of solar concentration before considering on-sun testing at the SHARP pilot facility.

The testing is not yet a commercial demonstration. SunHydrogen described the efficiency result as preliminary, and the next stages depend on agreed technical milestones. That distinction matters because laboratory efficiency and commercial hydrogen production are very different hurdles.

How does direct solar hydrogen actually work?

Traditional green hydrogen usually starts with electricity. Solar panels generate power, and an electrolyzer then uses that electricity to split water into hydrogen and oxygen. SunHydrogen is pursuing a different arrangement that combines solar-energy capture with water splitting inside its modules.

Its technology uses photovoltaic layers and catalysts to help drive the water-splitting reaction. The company has also developed nanoparticle-based approaches for producing hydrogen directly from sunlight and water. The broader idea is to reduce the need for separate solar electricity equipment and an external electrolyzer.

That could eventually simplify some hydrogen systems if the technology becomes durable and inexpensive. But fewer components do not automatically mean lower costs. Manufacturing, water handling, gas collection, maintenance and module lifetime would still shape the final economics.

SunHydrogen is based in Coralville, Iowa. The company has also been developing larger modules through pilot work in Austin, Texas. In May, it said improved 1.92-square-meter modules showed preliminary field performance consistent with earlier laboratory-tested modules.

That outdoor testing is particularly important because sunlight does not behave like a laboratory simulator. Real systems face changing weather, temperatures, dust and uneven illumination throughout the day. A technology that can hold its performance outside becomes much more interesting than one that only produces impressive numbers under controlled conditions.

The potential applications also extend beyond passenger cars. Clean hydrogen is being explored for industries where direct electrification can be difficult, including fertilizer production, refining and some heavy industrial processes. For American companies, cheaper ways to produce clean hydrogen could eventually affect those energy-intensive sectors.

The next stage is designed to answer a much harder question than whether the technology can cross 10%. SunHydrogen and Sparc Hydrogen plan more laboratory testing under increasing solar concentration. If the required milestones are met, the work could move outdoors at the SHARP facility in Roseworthy, South Australia.

The companies also plan a techno-economic assessment after the testing program. That study is supposed to examine the levelized cost of hydrogen, which measures the overall cost of producing hydrogen across a system’s operating life. For investors and future customers, that number could matter more than the headline efficiency percentage.

There is another reason to watch the next results closely. SunHydrogen has recently reported improved performance from its larger Austin modules, suggesting that lessons from earlier testing are being incorporated into newer designs. The company says those 1.92-square-meter modules are showing performance consistent with previous validated module benchmarks.

For now, the 10% result is a promising laboratory milestone, not proof of commercial success. The more revealing test will come when the modules operate at larger scale and under real sunlight. SunHydrogen has already shown that reaching 10% is possible on a small device. The harder challenge is proving that the number can survive outside the lab.