Low-cost saltwater battery wins $500,000 award

Could this be a small turning point for renewable energy?

A relatively cheap and environmentally friendly battery that uses saltwater and other commonly available materials to solve one of the biggest technical challenges facing renewable energy technologies was awarded a prize whose past recipients have gone on to have significant impact on technology and society at large.

An Aqueous Hybrid Ion battery roughly the size of a dishwasher or small refrigerator potentially stores enough solar or wind energy to power a single-family home completely off the grid in a region where sunlight is relatively plentiful, according to Dr. Jay Whitacre, a professor of materials science at Carnegie Mellon who invented the battery.

Aquion M100 Battery Module.
Source: Aquion Energy
Aquion M100 Battery Module.

Whitacre founded Aquion Energy in 2008 and received venture funding from Kleiner Perkins Caufield and Byers shortly thereafter. It was announced Tuesday that Whitacre was given the 2015 Lemelson-MIT Prize, an award worth $500,000, for inventing the battery. (Investors in Aquion include Bill Gates and venture capital firm Kleiner Perkins Caufield and Byers.)

Past winners of the Lemelson-MIT Prize have included other influential inventors, including Ray Kurzweil, Dean Kamen, Douglas Engelbart, the inventor of the computer mouse, and Leroy Hood, who invented the DNA sequencer.

A suitable and inexpensive method for storing energy could be a boon to the adoption of renewable energy technology, especially sources such as wind and solar energy.

When conditions are favorable, these sources are capable of capturing much more energy than users might immediately need. But when the sun is not shining or the wind is not blowing, they are of little help.

Scientists and the renewable energy industry have considered using batteries to smooth out this imbalance; energy captured when sun or wind are abundant can be stored and be meted out in leaner times.

This would make wind and solar far more competitive with fossil fuels and nuclear power, which are seen as providing a steadier stream of electricity than wind and solar.

There already are similar batteries available, but Whitacre says they are typically made with materials that might be unsafe, are more expensive or are environmentally dangerous.

Lithium-ion batteries are a common technology that Whitacre said might be considered competitors with Aquion's batteries, but lithium-ion batteries that can perform for as many charge and discharge cycles as Aquion's saltwater battery would cost significantly more.

Whitacre said that the company should be able to sell Aquion batteries capable of powering a typical single family home for between $1,000 and $3,000, depending on the size, once the company is working at full production in the next year or two. Those batteries will last for about 3,000 cycles, or 3,000 days and nights. So, if the battery were hooked up to solar panels, one day would represent a full charge and one night might represent a full discharge. Taken together, one charge and one discharge makes one complete cycle.

In addition, lithium-ion batteries are full of a flammable solvent, whereas the Aquion battery are nonflammable and nonexplosive, Whitacre told CNBC.

"[Our batteries] cannot burn, they are full of water," he said. "And when they dry out, they are fire retardant." The batteries also do not use heavy metals or toxic chemicals.

Michael Webber, deputy director of the Energy Institute at the University of Texas, said he was not familiar with Aquion Energy in particular, but he said that a saltwater-based battery poses a number of potential advantages over other options.

"With some battery technologies, such as lithium-ion, you have potential issues with the price and availability of the materials."

Webber said that some of the materials needed for batteries could prove difficult to source down the road. There even could be trade or supply-chain security issues that may hinder access to needed materials in countries where they are mined.

"Saltwater, on the other hand, is everywhere, so you don't have those same constraints," he said.

Aqueous-ion batteries are also easier to build than lithium-ion batteries, said Robert Fares, a researcher in Webber's lab at the University of Texas.

"It is basically electrodes that dip into the saltwater, whereas lithium batteries undergo this complex manufacturing process," Fares told CNBC.

Stringing lithium-ion batteries together also generally requires a battery management system to manage them, which Aquion's batteries do not need.

However, there are a couple of limitations to saltwater batteries in general, Fares said. First, aqueous-ion batteries have a lower energy density than lithium batteries; lithium-ion batteries can pack more battery capacity into a smaller case than aqueous-ion batteries can.

And, generally lithium-ion batteries come out on top for efficiency.

"A battery is a box of energy where you put a certain amount of energy in, and you get a slightly smaller amount of energy out," he said. With lithium-ion, you get out a larger amount of the energy that you had put into the box.

That might not be a problem for aqueous-ion batteries, as long as they save enough money over lithium-ion to make up for the lost efficiency, Fares said.

Aquion is focusing its near-term sales efforts on areas where energy is expensive and dirty, such as island regions, developing countries or remote regions with poor energy infrastructure.