First aqueous solar flow battery designed

Researchers have designed the first aqueous flow battery with solar capability that can achieve a 20 per cent energy savings over traditional batteries.
Researchers at The Ohio State University had developed the world's first solar air battery last fall.
In a new study, the researchers have reported that their patent-pending design - which combines a solar cell and a battery into a single device - now achieves a 20 per cent energy savings over traditional lithium-iodine batteries.
The 20 per cent comes from sunlight, which is captured by a unique solar panel on top of the battery, said Yiying Wu, professor at Ohio State.

The solar panel is a solid sheet, rather than a mesh as in the previous design. Another key difference comes from the use of a water-based electrolyte inside the battery.
Because water circulates inside it, the new design belongs to an emerging class of batteries called aqueous flow batteries.

"The truly important innovation here is that we've successfully demonstrated aqueous flow inside our solar battery," Wu said.
As such, it is the first aqueous flow battery with solar capability. Or, as Wu and his team have dubbed it, the first "aqueous solar flow battery.
"It's also totally compatible with current battery technology, very easy to integrate with existing technology, environmentally friendly and easy to maintain," he added.

Researchers around the world are working to develop aqueous flow batteries because they could theoretically provide affordable power grid-level energy storage someday.
The solar flow battery could thus bridge a gap between today's energy grid and sources of renewable energy.
"This solar flow battery design can potentially be applied for grid-scale solar energy conversion and storage, as well as producing 'electrolyte fuels' that might be used to power future electric vehicles," said Mingzhe Yu, lead author of the paper and a doctoral student at Ohio State.
The new solid solar panel is called a dye-sensitised solar cell, because the researchers use a red dye to tune the wavelength of light it captures and converts to electrons.

Those electrons then supplement the voltage stored in the lithium-anode portion of the solar battery.
To carry electrons from the solar cell into the battery, a liquid electrolyte is required, which is typically part salt, part solvent.
The researchers used lithium iodide as the salt, which offers a high-energy storage capacity with low cost, and water as the solvent.
In tests, the researchers compared the solar flow battery's performance to that of a typical lithium-iodine battery. They charged and discharged the batteries 25 times. Each time, both batteries discharged around 3.3 volts.
The difference was that the solar flow battery could produce the same output with less charging.

The study was published in the Journal of the American Chemical Society.