LENS Engineering, Science, and Technology

Go with the Flow

Developing a Renewable Battery for Emerging Energy Needs

Drawing that has a modern machine outputting clouds of dataIMAGE: Harry Campbell / Theispot

Four decades ago, Case Western Reserve Professor Robert Savinell, PhD, and his colleagues did something no one had done before: They used inexpensive materials to create an economic, continuously rechargeable battery capable of storing the energy generated by utility power plants, windmills and solar panels.

Right about that time, the energy crisis subsided and the world lost interest in alternative strategies.

But with the recent expansion of wind farms, the growth of solar capacity and the explosion in the market for products that store energy, Savinell's 40-year-old idea is taking on new life.

The Distinguished University Professor and his team have received nearly $3.25 million from the U.S. Department of Energy to enlarge the size and capacity of their prototype "iron- flow" battery, which stores excess energy and makes it available during peak usage times.

Navigant Research, which analyzes clean-technology markets, estimates the global market for utility-scale energy storage such as ow batteries will be $3.6 billion by 2025—15 times higher than in 2016.

Flow batteries store and discharge energy with the help of a chemical mixture and two storage tanks. As energy in the form of electricity ows into the battery, it forces the removal of electrons from the chemical mixture in one tank and the absorption of the electrons in a mixture in the second tank, turning the mixtures in both tanks into a high-energy state that allows for storage of the electric energy. The process is reversed when the energy is discharged for use as electricity.

Savinell's battery offers several advantages. While most other flow batteries under development use the expensive element vanadium in highly corrosive acid solutions, his battery relies on inexpensive, readily available iron in a saltwater solution for energy storage.

Iron also offers cost benefits with increased storage capacity because larger tanks are used with more low-cost chemicals. For example, an iron-flow battery can store a kilowatt-hour of energy for about $200, said Savinell, also the George S. Dively Professor of Engineering. Doubling the storage capacity halves the cost per kilowatt-hour, while quadrupling it quarters the cost. In most other systems, he said, costs increase with capacity.

"If utilities had large-scale energy storage, they could operate power plants more efficiently because they wouldn't have to turn them off and on to respond to demand," Savinell said.

—Jenni Laidman