Scientists engineer non-toxic flow batteries using common plant nutrients rather than toxic metals and acids

(NaturalNews) Harvard researchers have designed a new type of rechargeable battery using cheap, abundant and nontoxic elements, according to a study published in the journal Science. This cost-efficient, safe energy storage system could be the key to making wind and solar energy more feasible on a large scale, the researchers said.

"This is chemistry I'd be happy to put in my basement," said lead researcher Michael J. Aziz. "The nontoxicity and cheap, abundant materials placed in water solution mean that it's safe — it can't catch on fire — and that's huge when you're storing large amounts of electrical energy anywhere near people."

Nontoxic, nonflammable, non-corrosive

The battery in question is a flow battery, in which energy is stored in external tanks of liquid similar to fuel cells; in contrast, solid-electrode batteries store energy in metal electrodes that are often toxic. Flow batteries are viewed as appealing for storing solar- or wind-generated electricity because they can easily and inexpensively be scaled to any size desired simply by adjusting the size of the tanks and pumping hardware.

Most flow batteries, however, are made using metal ions dissolved in acid. The metals in question are often expensive, corrosive and inefficient. Last year, the same Harvard researchers designed a flow battery that uses organic molecules known as quinones in place of metal ions. Quinones are not only organic but also naturally abundant, playing key roles in photosynthesis and cellular respiration. Even this battery, however, still relied on the toxic, volatile element bromine for part of its design.

In the new design, bromine has been replaced with an iron compound called ferrocyanide.

"It sounds bad because it has the word 'cyanide' in it," said co-lead author Michael Marshak, now at the University of Colorado Boulder. "Cyanide kills you because it binds very tightly to iron in your body. In ferrocyanide, it's already bound to iron, so it's safe. In fact, ferrocyanide is commonly used as a food additive, and also as a fertilizer."

The team also made other changes to the design to improve its efficiency without increasing its cost or reducing its safety.

"We combined a common organic dye with an inexpensive food additive to increase our battery voltage by about 50 percent over our previous materials," co-lead author Roy Gordon said, "deliver[ing] the first high-performance, nonflammable, nontoxic, noncorrosive, and low-cost chemicals for flow batteries."

The new battery is made with an alkaline solution. Although it is not safe for direct exposure, it poses relatively little risk during normal use or disposal. Touching the solution would be similar to touching the inside of a disposable AA battery, Marshak said.

"It's not something you want to eat or splash around in, but outside of that it's really not a problem," he said.

Game-changer for solar power?

The greatest potential for the new batteries is likely in the storage of wind- or solar-generated electricity, both on a home and utility scale. One of the major obstacles to widespread adoption of wind and solar energy is that the electricity needs to be generated only at specific times (i.e., windy days or while the sun is shining), and it is wasted if it is not used immediately. In contrast, fossil fuel-based power plants are constantly adjusting their generation to account for current usage.

The prospect of a cheap, safe, scalable battery dramatically changes that picture.

The new batteries have strong implications for home users of solar energy as well, said market expert William W. Hogan, also of Harvard. Hogan notes that the incentives currently offered by power companies for consumers to install solar rooftop systems and sell the excess power generated back to the utility in exchange for a credit are "uneconomic and unsustainable." As solar panels become more widespread, utilities won't need that much power and will stop offering incentives. When that happens, homeowners will need to install their own batteries, which could then allow them to unplug from the grid entirely.

Sources for this article include:
News.Harvard.edu