January 15, 2014
New Solar Energy System May Provide Power 24 Hours A Day
[ Watch the Video: How To Get 24 Hours Of Solar Power ]
Brett Smith for redOrbit.com - Your Universe OnlineWhile solar power has long been considered a viable alternative to fossil fuels, a limited number of daylight hours has kept it from becoming a 24-hour source of electricity.
Now, researchers from the Energy Frontier Research Center at the University of North Carolina have reportedly developed a system that converts the sun’s energy into hydrogen fuel that can be stored for later use – sidestepping solar energy’s nighttime pitfall.
“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 Tom Meyer, a chemistry professor at UNC. “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.”
The new system, known as a dye-sensitized photoelectrosynthesis cell (DSPEC), creates chemical fuel by using the solar power to divide water molecules into their constituent parts: hydrogen and oxygen. After water is split, hydrogen is isolated and stored, while oxygen is released into the air.
“But splitting water is extremely difficult to do,” Meyer noted. “You need to take four electrons away from two water molecules, transfer them somewhere else, and make hydrogen, and, once you have done that, keep the hydrogen and oxygen separated. How to design molecules capable of doing that is a really big challenge that we’ve begun to overcome.”
The UNC system depends on the use of a particular molecule and specialized nanoparticle. The molecule, called a chromophore-catalyst assembly, takes in solar energy and then starts the catalyst that draws electrons away from water molecules. The nanoparticle is part of a film that removes the electrons to make the hydrogen fuel.
Previous attempts to create this system have crashed because either the molecule kept breaking away from the nanoparticle film or because the electrons couldn’t be removed fast enough to make fuel.
To solve these problems, the researchers used a technique that covered the nanoparticle with a thin atomic layer of titanium dioxide. By such thin layers, the researchers discovered that the nanoparticle was able to whisk away electrons much more quickly – allowing freed electrons to readily make hydrogen. The team also created a protective coating that keeps the chromophore-catalyst assembly linked to the nanoparticle.
The novel system is able to turn the solar energy into fuel without external power and greenhouse gas emissions. Additionally, the infrastructure necessary for the system is based on existing technology. The researchers said their next goal is to target carbon dioxide, a greenhouse gas, for conversion into a carbon-based fuel such as methanol.
“When you talk about powering a planet with energy stored in batteries, it’s just not practical,” Meyer said. “It turns out that the most energy dense way to store energy is in the chemical bonds of molecules. And that’s what we did – we found an answer through chemistry.”
Last week, Harvard scientists announced the discovery of another chemical system that could be used to store solar energy: an innovative grid-scale battery.