'Solar flow batteries' generate and store energy from sunlight with record efficiency

Alex Crees
By Alex Crees October 8th, 2018
For business

Solar panels generate energy from sunlight. Batteries store that energy for later use. And now, a new hybrid may be able to combine those two technologies – with record efficiency.

Researchers from the University of Wisconsin-Madison and the King Abdullah University of Science and Technology in Saudi Arabia say they are developing a “solar flow battery” that marries photovoltaics, energy storage and energy delivery.

Their research, published in the journal Chem, outlines the general design principles for further development of the integrated device, which has a record solar-to-output electricity efficiency of 14.1 percent – eight times the efficiency rating of earlier prototypes.

Comparatively, most commercially available solar panels today have a 15 to 17 percent efficiency rating. The researchers say it may even be possible to improve upon that rate.

“We believe we could eventually get to 25 percent efficiency using emerging solar materials and new electrochemistry,” Song Jin, a professor of chemistry at the University of Wisconsin-Madison, said in a released statement. “At this efficiency range, without using the expensive solar cells, it should be quite competitive with other renewable energy technologies.”

What is a solar flow battery?

A solar flow battery combines a solar cell and a battery to absorb sunlight and store it as chemical energy for later on-demand use.

The battery has three modes: it can immediately convert sunlight to electricity, it can store the energy electrochemically to be used later, or it can be re-charged by electrical energy – just like a normal battery.

One of the primary benefits of the integrated system is that it can help reduce losses and inefficiencies, according to the researchers.

“Compared with separated solar energy conversion and electrochemical energy storage devices, combining the functions of separated devices into a single, integrated device could be a more efficient, scalable, compact, and cost-effective approach to utilizing solar energy,” said Jin.

Bringing clean energy to rural areas

The relationship between solar energy and grid resiliency made headlines in September when it was widely reported that solar installations in North Carolina were up and running a day after Hurricane Florence crippled the state’s electric grid. Residents who relied on coal-fired utilities, on the other hand, were without power for weeks.

Not only does a solar flow battery present an alternative option when traditional electrical systems fail, it could also bring clean electricity to remote, off-grid locations.

This work paves the way for a practical new approach to harvesting, storing, and utilizing the intermittent solar energy with unprecedented high energy conversion efficiency and energy storage density,” the researchers wrote. “These integrated solar flow batteries will be especially suitable as distributed and stand-alone solar energy conversion and storage systems in remote locations and will enable practical off-grid electrification.”

But these applications, for now, are still out of reach from a financial standpoint, the researchers admitted.

“At this early stage of the development of solar flow batteries, we are trying to demonstrate the design principles and push the boundaries to show what could be possibly achieved, with some sacrifice regarding cost effectiveness,” they wrote.

The researchers added that simpler designs, cheaper materials and technological advancements in the future could make the batteries more competitive with other forms of renewable energy.

Optimally, Jin told Inverse solar flow batteries could be commercially available within the next 5 to 7 years.

Alex Crees is a writer covering issues related to energy, the environment and politics.  Her work has appeared in Fox News and Prevention. Alex earned a bachelor’s degree in journalism from New York University.