Hydrogen is expected to play an important role in the future of clean energy because it can store renewable electricity and produce no carbon emissions when used as a fuel.
However, making hydrogen requires energy, and the process is only environmentally friendly if that energy comes from renewable sources such as sunlight or wind.
Now, scientists at the Fraunhofer Institute for Solar Energy Systems (ISE) in Germany have developed a new technology that produces hydrogen directly from sunlight with remarkable efficiency.
Their new system combines advanced solar cells with a water-splitting device, allowing solar energy to be converted into hydrogen in a single, highly efficient process.
The researchers built a demonstration system that converted up to 31.3% of the sunlight it received into the chemical energy stored in hydrogen.
This is one of the highest efficiencies reported for this type of solar hydrogen production.
Hydrogen is produced by a process called electrolysis. During electrolysis, electricity is used to split water molecules into hydrogen and oxygen.
Normally, electricity is first generated by solar panels and then sent through electrical equipment before reaching the electrolyzer. Each of these steps can waste some energy.
The new system avoids many of these losses by connecting the solar cells directly to the electrolyzer.
This allows the electricity produced by the solar cells to flow straight into the water-splitting process without unnecessary conversion steps.
The researchers used a special type of solar cell known as a III-V solar cell. These are the most efficient solar cells currently available and have been used for many years in spacecraft because of their excellent performance and long lifespan.
To make the system even more efficient, the team used a Fresnel lens array to concentrate sunlight onto the small solar cells.
A Fresnel lens works like a lightweight magnifying glass, focusing sunlight into a much smaller area. This allows the highly efficient solar cells to generate a stronger electrical voltage while using much less solar cell material.
The electricity generated by the solar cells was sent directly to two proton exchange membrane (PEM) electrolyzer cells connected in series.
These electrolyzers split water into hydrogen and oxygen. Because the electrical output of the solar cells was carefully matched to the needs of the electrolyzer, the system operated with very little wasted energy.
During outdoor testing, the small demonstration device, which had a lens area of just 64 square centimeters, achieved an impressive solar-to-hydrogen conversion efficiency of 31.3%.
Although the technology is still in its early stages, the researchers believe it has great potential for future clean energy systems. Highly efficient solar hydrogen production could help store renewable electricity for later use, support industries that need clean hydrogen, and reduce dependence on fossil fuels.
The Fraunhofer team says more research and investment are needed before the technology becomes commercially available.
They are now seeking investors to help launch a new company, Clearsun Energy, which will continue developing this promising approach.
If successful, the technology could become an important step toward producing affordable, renewable hydrogen directly from the power of the sun.
Source: KSR.
