New system harnesses sun’s energy during day for use at night

January 15, 2014 by  
Filed under Solar Energy Tips

According to a January 14 news release from the University of North Carolina at Chapel Hill, a team of researchers led by Tom Mayer at the university’s Energy Frontier Research Center has built a system that converts solar energy into hydrogen fuel and stores it for later use.  The system allowed the team to power several electronic devices for hours after sunset.

“So called ‘solar fuels’ like hydrogen offer a solution to how to store energy for nighttime use by taking a cue from natural photosynthesis,” said Meyer, Arey Distinguished Professor of Chemistry at UNC’s College of Arts and Sciences.  “Our new findings may provide a last major piece of a puzzle for a new way to store the sun’s energy – it could be a tipping point for a solar energy future.”

In a single hour, our sun radiates enough energy to power every vehicle, factory, and device on Earth for an entire year.  Although solar panels can absorb that energy during the day, when the sun sets, the ability to provide power disappears.  For solar energy to really become popular on a global scale, researchers had to devise a means to store the energy for nighttime use.

The new system bridges that gap.  Called a dye-sensitized photoelectrosynthesis cell, or DSPEC, the unit produces hydrogen fuel by using the sun’s energy to divide water into its component parts.  Following the split, hydrogen is isolated and stored, while the derivative, oxygen, is released into the air.

Meyer’s design has two fundamental components: a molecule and a nanoparticle.  The molecule, called a chromophore-catalyst assembly, absorbs sunlight and then triggers the catalyst to split electrons away from water.  The nanoparticle, to which thousands of chromophore-catalyst assemblies are bound, is part of a film of nanoparticles that transports the electrons away to produce the hydrogen fuel.

However, the system always crashed either because the chromophore-catalyst assembly kept breaking away from the nanoparticles, or because the electrons couldn’t be transported away fast enough to make hydrogen.

To combat both of these issues, Meyer collaborated with Greg Parsons’ group at North Carolina State University to employ a technique that coated the nanoparticle, atom by atom, with a thin layer of a material called titanium dioxide.  By using extremely thin layers, the researchers discovered that the nanoparticle could transport electrons far more quickly than before, with the freed electrons available to make hydrogen. They also figured out how to build a protective coating that keeps the chromophore-catalyst assembly tethered firmly to the nanoparticle, ensuring that the assembly stayed on the surface.

Meyer’s system can transform solar energy into fuel – with little external power to operate, and no greenhouse gas emission.  The next target in the research team’s sight is to use the same approach to shrink carbon dioxide to a carbon-based fuel such as formate or methanol.

Comments are closed.