A team of researchers in Germany has discovered a highly efficient way to convert sunlight into hydrogen fuel, potentially solving some of the most critical challenges facing the green hydrogen sector and offering an elegant solution to clean up some of the economy’s dirtiest industries. The new prototype, which uses a kind of solar cell used in spacecraft, is a proof-of-concept for what could someday make the production of totally clean-burning fuel a commercially scalable possibility.
Scientists at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Baden-Württemberg, combined photovoltaic cells with proton exchange membrane electrolyzer cells to create a totally new system capable of converting sunlight to hydrogen with 31.3 percent efficiency. “Our new record shows that hydrogen can be produced very efficiently directly from sunlight,” Frank Dimroth, PhD, told Interesting Engineering.
The prototype relies on III-V solar cells, the most efficient solar cells produced anywhere. “These cells have long been used in spacecraft because of their high performance and durability,” reports Interesting Engineering.
Green hydrogen has long been hailed as a critical clean alternative for hard-to-abate industrial sectors like steelmaking and shipping. Like the emissions-intensive thermal coal and heavy fuel oil that power those industries, respectively, hydrogen burns at a high heat. But instead of leaving behind carbon dioxide and other greenhouse gases and pollutants, hydrogen leaves behind nothing but water vapor when combusted.
There’s just one major issue – hydrogen is only as green as the energy used to produce it. The vast majority of the hydrogen used in the global economy is gray hydrogen, which is made using fossil fuels and therefore ineffective for reducing a given industry’s carbon footprint. Green hydrogen, made using renewable energies, has been touted as a kind of silver bullet for the clean energy transition for many years now, but, as usual, the reality is far more complicated.
Once lofty global green hydrogen ambitions have seriously fizzled in recent years. A 2025 study on “The green hydrogen ambition and implementation gap” found that, in 2023, less than a tenth of planned green hydrogen was actualized. “Tracking 190 projects over 3 years, we identify a wide 2023 implementation gap with only 7% of global capacity announcements finished on schedule,” reads the paper, published in the scientific journal Nature Energy.
In many – if not most – applications, renewable energy resources are more useful consumed directly than used to make hydrogen. A 2022 report by the International Renewable Energy Agency (IRENA) warned against the “indiscriminate use of hydrogen,” cautioning that the extensive use of hydrogen “may not be in line with the requirements of a decarbonised world,” as it “requires dedicated renewable energy that could be used for other end uses.” In other words, just because we can use green energy for hydrogen without losing money, we are still losing efficiency, and those clean energy resources may be better used elsewhere. Put very simply, green hydrogen is costly and inefficient to produce.
For this reason, the breakthrough at the Fraunhofer Institute for Solar Energy Systems (ISE) could be majorly disruptive. Instead of producing electricity with photovoltaic solar panels, and then using that energy to make hydrogen, the new prototype directly converts sunlight into hydrogen, skipping the middle step. As sunshine is an infinite resource, this new approach could be a gamechanger, decarbonizing heavy industry without taking clean energy away from any other sector.
However, the model still has a long way to go before it could potentially hit the market and change everything. “Development is still in its early stages, and it’s hard to say how quickly we’ll be able to achieve competitive systems,” Dimroth said in a press release related to the study. “To further develop the concept, we are seeking investors for our planned spin-off, Clearsun Energy,” Dimroth concluded.
Luckily, timing has rarely been better to secure funding in green hydrogen research. After years of flagging interest in the technology and a startup bubble that had all but burst, the current global energy crisis emanating out of the Strait of Hormuz has revitalized investor interest in green hydrogen.
By Haley Zaremba for Oilprice.com
