Rechargeable battery to power homes from rooftop solar panels

A team of Harvard University scientists and engineers has demonstrated a safe and affordable battery capable of storing energy from intermittent sources -- like rooftop solar panels -- that is suitable for the home.

The rechargeable battery can make storage of electricity from intermittent energy sources like solar and wind safe and cost-effective for both residential and commercial use.

In the operation of the battery, electrons are picked up and released by compounds composed of inexpensive, earth-abundant elements (carbon, oxygen, nitrogen, hydrogen, iron and potassium) dissolved in water.

The compounds are non-toxic, non-flammable, and widely available, making them safer and cheaper than other battery systems.

"That is huge when you're storing large amounts of electrical energy anywhere near people," explained Michael J. Aziz from Harvard Paulson School of Engineering and Applied Sciences (SEAS).

The mismatch between the availability of intermittent wind or sunshine and the variability of demand is a great obstacle to getting a large fraction of our electricity from renewable sources.

This problem could be solved by a cost-effective means of storing large amounts of electrical energy for delivery over the long periods when the wind is not blowing and the sun is not shining.

This new battery chemistry was discovered by post-doctoral fellow Michael Marshak and graduate student Kaixiang Lin working together with co-lead author Roy Gordon, Thomas Dudley Cabot Professor of Chemistry and professor of materials science at Harvard.

"We combined a common organic dye with an inexpensive food additive to increase our battery voltage by about 50 percent over our previous materials," Gordon added.

The findings "deliver the first high-performance, non-flammable, non-toxic, non-corrosive, and low-cost chemicals for flow batteries."

The "flow battery" design offers potential advantages in cost and the length of time it can maintain peak discharge power compared to lithium batteries.

The research appeared in a paper published in the journal Science.