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Harnessing the Sun’s Energy for Use at Night

Solar energy has long been used as a clean alternative to fossil fuels such as coal and oil, but it could only be harnessed during the day when the sun’s rays were strongest. Researchers have built a system that converts the Sun’s energy not into electricity but hydrogen fuel and stores it for later use, allowing us to power our devices long after the Sun goes down.

The new system designed at North Carolina State University is a dye-sensitized photoelectrosynthesis cell, or DSPEC, and it generates hydrogen fuel by using the sun’s energy to split water into its component parts. After the split, hydrogen is sequestered and stored, while the byproduct, oxygen, is released into the air.

The design has two basic components: a molecule and a nanoparticle. The molecule, called a chromophore-catalyst assembly, absorbs sunlight and then kick starts the catalyst to rip electrons away from water. The nanoparticle, to which thousands of chromophore-catalyst assemblies are tethered, is part of a film of nanoparticles that shuttles the electrons away to make the hydrogen fuel.

The system can turn the Sun’s energy into fuel while needing almost no external power to operate and releasing no greenhouse gases. What’s more, the infrastructure to install these sunlight-to-fuel converters is in sight based on existing technology. A next target is to use the same approach to reduce carbon dioxide, a greenhouse gas, to a carbon-based fuel such as formate or methanol.

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