A new artificial photosynthesis system can create solar fuel without needing batteries. This makes the process simpler and potentially cheaper for storing clean energy.
Researchers at Osaka Metropolitan University developed this system. It produces solar fuel more consistently by building a self-regulating chemical part directly into the electrolyzer. This removes one of the most expensive components usually found in these technologies.
Like plants, artificial photosynthesis uses sunlight to turn water and carbon dioxide into useful fuels. One such fuel is formic acid, which can store energy.
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The electrolyzer is a key part of this process. It changes electricity from solar cells into chemical energy. This allows fuels like formic acid to be made and stored.
One challenge is keeping the system working well when sunlight changes throughout the day. Many artificial photosynthesis systems use Maximum Power Point Tracking (MPPT) to handle this. MPPT adjusts voltage and current to keep solar cells working at their best.
However, MPPT systems often need batteries and other electronics to keep the energy flow steady. While effective, these extra parts add cost and complexity.
Battery-Free Design
To make the system simpler, a team at Osaka Metropolitan University, led by Associate Professor Yasuo Matsubara and Professor Yutaka Amao, redesigned the electrolyzer. They worked with Iida Group Holdings Co., Ltd and used a special solid electrolyte.
This new electrolyzer can perform the MPPT function on its own. This means it doesn't need batteries or external control hardware.
Instead of relying on separate electronics, converters, and batteries, the electrolyzer automatically adjusts itself. It changes its electrical properties by varying its heat and resistance.
"As sunlight increases, the electrolyzer naturally heats up," Professor Amao explained. "The system is designed so that this warming causes the electrical resistance to drop, allowing electricity to flow more freely." He added that this makes the system automatically adjust its electrical behavior.
This self-regulating feature helps keep fuel production stable all day. It also automates the system and reduces the need for batteries and expensive external parts.
Real-World Testing
The researchers tested a prototype of this technology. It successfully and consistently made formic acid from water and CO2 under real outdoor sunlight. This worked even when light levels changed.
"We were confident that it would be successful," Professor Matsubara said. He noted that they had shown this research at an exhibition for the Osaka Kansai Expo 2025. "It successfully generated enough formic acid to power a miniature diorama in the pavilion, showing its potential." He believes it could be used to power applications in homes.
Deep Dive & References
The findings were published in the journal EES Solar.
Chemical maximum-power-point tracking system for stabilized liquid solar-fuel production - EES Solar, 2026
