This new battery design could be the future of powering off-the-grid cottages

Updated: November 26, 2018

Metal-Air Battery Brandon Hopkins

The rhythmic chug of a backup gas generator can signal a cottager’s worst nightmare: a winter power outage. It doesn’t help that these generators are cumbersome, expensive, and not the environment’s closest ally. But Brandon Hopkins, a postdoctoral fellow at the U.S. Naval Research Laboratory in Washington, D.C., may have just refined the next big energy source for cottagers with power problems. Hopkins has been researching metal-air batteries, some of the lightest and most compact batteries on the market. Metal-air batteries are made up of two electrodes and an electrolyte. “You can kind of think of it like a sandwich,” Hopkins says. “You have two pieces of bread and then jelly in the middle. And the jelly in the middle is the electrolyte, and the two electrodes are like the pieces of bread.”

Specifically, Hopkins has been focusing on aluminum-air batteries because they have some of the highest energy discharge. “The main selling point of aluminum is that it’s super, super energy dense,” he says. “It’s way more energy dense than lithium-ion and other batteries like that.” Aluminum-air batteries generate power by using a pump to funnel oxygen from the atmosphere into the battery. The oxygen then reacts with the aluminum to create a charge. Because of the battery’s powerful discharge, they tend to be used by the military to power long-range drones, and have started to be used by electric car companies to extend the range of their cars’ batteries. Metal-air batteries are not electrically rechargeable, but are recharged mechanically by replacing the corroded aluminum.

Of interest to cottagers, EaglePicher Technologies, a battery manufacturer, has even been dabbling with generators powered by aluminum-air batteries instead of gasoline. The main issue with aluminum-air batteries, however, is that if they’re not used frequently, the aluminum is corroded by the electrolyte very quickly. They can lose 80 per cent of their charge a month by just sitting on the shelf, compared to a lithium-ion battery that only loses about five per cent of its charge per month.

That’s where Hopkins comes in. He, along with researchers Yang Shao-Horn and Douglas P. Hart, have discovered that a little oil can drastically increase the shelf-life of an aluminum-air battery. “It’s a pretty straightforward technology,” Hopkins says. When the battery is not in use, a small amount of oil is pumped into the battery pushing out the electrolyte, preventing the aluminum from corroding. Then, when the battery is put to use, the electrolyte is pumped in and pushes out the oil.

During lab experiments, Hopkins and his team tested an aluminum-air battery without the oil and one with the oil by using them for five-minute intervals with 24- or 72-hour breaks in between. The battery without the oil corroded after a matter of days, while the battery with the oil continued to operate for a few weeks. With Hopkins’ oil innovation, aluminum-air batteries now lose only .02 per cent of their charge a month. This makes them viable options for powering devices like backup generators. Not to mention, the battery is very lightweight and easy to carry around.

Hopkins’ oil innovation has been patented but it is not commercially for sale yet. “We’re kind of now looking for industry partners to license the technology,” he says. Although Hopkins stresses that off-the-grid cottages were not the intended subject of his research—he envisioned the battery being used primarily for military applications—he says that he could certainly see the battery being used to power a generator. “I do think it’s a pretty good application for the technology.”        



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